RLA style JBL/VOTT Club System, advice needed [Archive]

RMC

07-04-2017, 04:10 PM

Hi budney,

First, forget the "Hi-Fi" aspect this is all Sound Reinforcement stuff in a club system. Second, I don't know why (though I have some ideas about it) but way too many people, like in your case, keep repeating the same mistakes of mixing in same stacks short-throw and long-throw equipment without proper consideration to many acoustical issues involved. Since you're writing "a party space I'm planning on opening" my understanding is that this will be Inside, not outdoors. Therefore, long-throw stuff like the Altec 816/828 (equivalent to JBL's 4560A) are not really appropriate for normal-size indoor rooms, even if others do it, unless you have a VERY LARGE (HUGE) place, because the horn "concentrated" low frequencies will more likely be bouncing on opposite walls and everywhere around the place, while the mid/high frequencies with shorter throw will be dispersed according to the device's coverage angle and throw. It's not because you've seen it done elsewhere that it necessarily makes good sense acoustically...

Since your top-end is already pretty much determined, with the most important of it being short-throw stuff (e.g. 2395 slant plates acoustic lens and 2404/2405 tweeters), then this is what you have to go with also on the bottom-end for it to be acoustically wise (i.e. technically sound) to avoid all sorts of sound quality problems. The 2402 bullet-type tweeters are more suited for long-throw applications. Mixing both types (short/long throw) close together is begging for trouble acoustically speaking. But then, it all depends on what you're trying to achieve: to impress the gallery with too loud bad sound or quality reproduction in a venue that MAY also turn out to be a difficult acoustical environment ?

W bins, berthas and levan extensions, all of that is for long-throw... To be logical with the top-end you chose, and if you don't want to repeat the errors of others, you should be looking more, for low-frequencies, at JBL 4520/4530 type cabinets or even at vented-boxes which would make more sense than front-loaded horns/BR enclosures such as Altec 816/828, and the former are much less difficult to build.

Based on some of the high/low-frequency choices you are mentioning, and with all due respect, it seems you have been improperly influenced by some of the technical non-sense circulated around here by some individuals who have clearly not done their homework. In simple terms, it's mostly a question of level, coverage and "reach" (i.e. spl, directivity and throw). I have written here before (in another thread) about some of this technical non-sense being thrown around here right and left, I quoted serious reference to JAES (and sent a personal copy) from some of the world-renowned JBL Engineers (Mark Gander and John Eargle) that what was mentioned by this member didn't exist (other than in his dreams) and guess what ? I still see that member here repeating again and again the same things as he did before in a new thread... Some people never learn! Or their ego refuses to admit they don't really know...

To avoid repeating the errors of others and maximize return (sound quality) on investment, my best advice is do yourself a favour, consult some professionnal and respected manuals like: JBL's Sound System Design Reference Manual, Yamaha's Sound Reinforcement Handbook or John Eargle's Handbook of Sound System Design, or to some extent even JBL's Dance Clubs Systems Booklet 2003 (I tried to upload this last one for you but the file is too large to be allowed by this site, write me with an address I'll send it to you by e-mail). Regards,

Richard

budney

07-04-2017, 08:05 PM

Hi Richard

Thanks for the detailed reply, this is exactly the kind of advice I was looking for!

In regards to mixing short throw and long throw equipment, that is just going from the system that I heard recently, which did use various different JBL acoustic lenses with various Altec vott boxes. I narrowed them down to the ones I thought sounded the best from listening to them in that room, but when listening to them I did think that it could have possibly been done better, that was just the first high efficiency club system I'd heard before and it inspired me to do it myself. It makes sense now that when you say the low range was long throw but the high short throw, I did notice some odd acoustical effects occurring when walking around the room. It's just that when comparing it to a normal modern club system, it sounds so much better, I was blown away by the clarity and not focusing on the shortfalls. Also I have nothing else to compare it to, all other systems I've worked with are awful modern digital things that are never set up correctly, with DJ's playing awful music from low quality mp3s.

I was also going by some research I had done online, specifically for vintage disco club systems. These systems are spoke about as once being the best in the world, and I trust that the people who worked on them knew what they were doing. Some of the engineers who worked on them back in the day agree that what they did wasn't always technically correct, but it did sound the best...for instance they swear by the 2402 being hung in an array above the dance floor because thats what they want, full throw of the highs everywhere around the room. I think thats maybe perhaps why the system I heard recently still sounded really good. The highs were short throw, but the centre of the room was covered by the 2402's above the dance floor, with the long throw altecs being able to reach far into the centre.

I have only been going by the advice/chat of professional engineers from that era, not someone who thinks they know audio in a forum. I have been told by modern professional engineers that pointing 4 stacks into the middle of the room is absolutely awful for the acoustics, but it makes for such a great party! Obviously I want to go for the best reproduction of sound I can, but I also want it to have that club thump and crack!

Which sub would you advise on using? That is one aspect I am most unsure about, I wasn't convinced that the subs I had heard recently were the best for that room. I'm planning a decent size room, that could fit 300 people in at a push, and hopefully with some acoustic treatment budget permitting. I should also say that the kind of music I'm going to play is mainly disco/world music/pre 1990s dance music, which is why I'm trying to design it with a vintage aspect in mind.

Thanks for the advice on the reading material, I had planned on picking up Yahama's sound reinforcement handbook as I'd seen the name thrown around a few times, I shall also look into the others. I've just had a glance at the JBL Dance Club booklet, and it does have useful information, but I feel like it was written with a modern dance floor in mind, which is something I'm trying to avoid. For instance the crossover I plan on using is in the DJ booth, so the DJ can change the levels of the subs and tweeters independently to great effect, you don't see these in clubs anymore. Also, I am trying to create a more 'hifi' club sound system, but without breaking the bank and going full class a. Is there anything that I could change/add to make it a bit more hifi and less PA?

Horn Fanatic

07-04-2017, 10:01 PM

budney

07-05-2017, 12:28 PM

More sensible words you have written are hard to find on this forum. Bravo. Frankly, I don't understand the fascination some folks on this forum have with that Jensen / RLA cabinet. Some kind soul on the forum a while back posted frequency graphs of the RLA box, and some dare to call it a sub-woofer. Odd, considering that dog begins to tank at 50 Hz.

It is my understanding that the RLA Waldorf, which is based on the Jensen, was not used as a sub? They were used on top of the big bertha/levan subs, as far as I'm aware. I've never seen or heard them, just going off what I've read online. I'm only looking at the RLA kind of speakers because everyone speaks of them as being the best dance systems in the world in the 70s and 80s.

I agree with your advice for using the 4520 horn, or multiples of the 4530. IMHO, the ALTEC Stanley Screamer single and dual 15" bass cabinets make for outstanding sub-woofers. The drivers for those ( the 421-8H and 8H II ) are easy to find, and command less money than used JBL woofers. Plus, if re-coning is required, Bill Hanuschack has the correct kits for them.

So dual 15" will be sufficient? I only ask this because every club sub I've heard has been dual 18s.
Would the 4520 scoop be a high fidelity speaker? The only scoops I've heard were awful and that put me off the idea of scoops, but that doesn't mean they're all bad. I'm just looking for a really efficient, dynamic system, would they provide that with the right drivers?

Horn Fanatic

07-05-2017, 04:11 PM

Greetings Budney -

I can understand why you were put off hearing some rear loaded enclosures. Typically, some folks have a habit of loading them with drivers unsuitable for use in horn cabinets with small chamber volumes such as the 4520 & 4520. Drivers with low Efficiency Bandwidth Product values do not operate well in small volumes. What you get is inarticulate bass. Not all cone drivers like to be horn loaded. Those with low EBP values tend to operate better in larger volumes. What you end up with is an enclosure comprised of more chamber volume than horn. For an enclosure of practical size, the horn would be so short as to be considered a discontinuity. To be honest, the majority of commercial folded horns behave more like a discontinuity, than a legitimate horn. As such, they perform much better in numbers.

As long as horn enclosures are within half a wavelength from each other at the the flare rate frequency, at a full wavelength they behave as one.

As for a vented sub enclosure, if dual 18" drivers are to your liking, there are scads of drawings on the internet for such enclosures. An 18" driver will move more air than a 15". A rear loaded bass horn such as the 4520 enclosure will be much more efficient than a bass reflex direct radiator.

Good luck,

HF

RMC

07-06-2017, 04:18 PM

Hi budney, and Horn Fanatic

Since you are into vintage disco club speaker systems, here's how it looked like back then (having 60 yo soon, I was there often in the 70's and 80's, and had friends who build JBL horn-loaded enclosures for a living during that period). The top choice of the disco era, the king of the dance floor, was JBL's 4520 rear-loaded folded horn more often than not. BTW these are NOT subwoofers but rather high-efficiency low frequency enclosures (bass cabinets), they don't go very deep into the bass (-5 db at 42 hz), instead they provide some amplitude in LF response (60-100 hz range) to add punch or impact to some of the lows. They are short-throw cabinets (75 feet or less) and the horn provides maximum driver loading down to 42 hz according to JBL. In my view this is quite sufficient for the application.

In terms of parts model numbers, the following is what it looked like most of the time in the good old days:
4520 (2205 drivers)/2440 compression driver/2395 slant-plate (some 2390 folded-plate) acoutic lens/2405 tweeter(s).

Now some comments regarding the above. First, though I really like their sound, I still think one has to be somewhat sadistic to himself to want to build horn-loaded cabinets on your own: too difficult, too much time, too large, too heavy, too costly, etc. I hope you have a large and well equipped woodshop along with a lot of muscle. Also, finding GOOD plans on the Web MAY be difficult. JBL never published official ones since this was probably a patented design. A German fellow has posted somewhere on the Web HIS plans for the 4530 (truthful to original?), but I don't recall seeing on the Net a complete and truthful set of drawings for the 4520. Former JBL Technical Director, George Augspurger did write a very long time ago about this type of cabinet in "The importance of speaker efficiency", Electronics World, January, 1962 (yes 1962), and on the last of his 3 page article he gave a drawing with most (not all) dimensions. Since the 4520 didn't exist officially until 1971 or so, the dimensions given by George are probably for the C-55 ancestor of the 4520. With that, along with JBL, Professional Series, Low Frequency Enclosures, May, 1980, you should be able to figure out pretty close dimensions using "reverse engineering" if need be. Nevermind the 4" pedestal shown by Augspurger if not required, these boxes were often placed directly on the floor.

Second, finding proper drivers for these cabinets could be quite a job in terms of availability and suitable Thiele/Small parameters. JBL 2205 drivers are long gone (except for my still original and working pair from 1981!) and if you can find some they will probably have been reconed to something else like 2225 (not same Thiele/Small parameters, but some members have said they used it successfully). The other driver later recommended by JBL for 4520 cabinets was the E-140 which has T/S pretty close to those of the 2205. Again, they will probably have been reconed with who knows what. Adventurous fellows, like my friends who built these cabinets, did also use JBL's K-140/K-145/E-145 for their longer cone travel capability (X-max) so DJ's could extract from the cabinets every drop of bass output possible in use/abuse... The parameters of the K/E-145 were somewhat off for ideal performance but since it had even more cone travel capability that prevailed over reason and anything else... Fellow member Horn Fanatic did suggest in the past the 2220 driver was suitable here re T/S and I agree with that, however the 2220 would not survive long the abuses in the field(Xmax 2mm), and was never recommended by JBL for this application. However, 2220 was THE choice for front-loaded horns such as 4550/4560.

Third, my advice if you want new drivers for these boxes is to look-up the T/S for 2205H/E-140 on JBL's driver T/S parameters list (jblpro.com) and try to purchase 15" drivers of proper dimensions and with as close as possible T/S as those of the two above, but preferably with higher Pe and X-max (min. 5+ mm) numbers since you seem to want to beat the hell out of the boxes to make lots of noise... Unless you use subwoofers, which personnaly I wouldn't do since it's not really required in Disco music, as in cinema sound for example, and not seen much in the good old days. Remember, Disco is more a matter of some amplitude in LF response, than very deep bass. Many people mix-up these two different things.

Fourh, since you raised budget considerations and indicated being in the UK, you may want to look first at some new Fane drivers like the Sovereign Pro and Colossus lines; maybe Eminence or Peavey brands. Others from Europe could be too expensive since the Pound has lost some luster VS Euro: B & C, RCF, 18 Sound, Faital Pro, etc.

Fifth, In any case, clever member Horn Fanatic gave you a pretty damn good suggestion with his idea of LF Stanley Screamers, which I didn't think of and haven't heard of for quite some time... Yeah, Stanley Screamers! If my memory is correct, these were developped by Altec Sound Contractor Stanal Sound USA in conjunction with Altec Lansing many years ago, right HF ? But they may not be easily available in the UK (location indicated by budney). BTW I'm glad Horn Fanatic (a knowledgeable horn guy around here) is keeping an eye on me in this Thread, this way I have to keep giving no less than 110%, otherwise he could be tempted to nail me to the cross, which is fine if I screw-up things. So far so good, HF ? My humble suggestion for subwoofer, which as said before I don't see as necessary, also to save some money, would have been something along the lines of JBL 4645C Cinema Sound Sub with 2242H 18" driver or even 2x15" cabs properly loaded (e.g. E-V DL 15W type, among many others).

BTW from the Disco era I also remember seeing some Cerwin-Vega setups made around B36A and L48 something folded-horn cabinets. They still exist with different model numbers and some modifications. I can remember only one Club that used Altec Lansing equipment, it wasn't used much in Canada...

"I am trying to create a more 'hifi' club sound system, but without breaking the bank and going full class a. Is there anything that I could change/add to make it a bit more hifi and less PA? " Yes, there is starting with your choice of equipment: rear-loaded horns, yes vs front-loaded horns, no. Compare frequency response curves of both types (e.g. 4520 vs 4560), it's evident; 2405, yes vs 2402 tweeters, no. Again compare frequency response curves it's also evident, you'll see the 2405 is a flatter (and "sweeter") device compared to the "gross" extreme output 2402 with 40° conical dispersion. 2405 tweeters were also often used by JBL in large Studio Monitors, I think this says it all for "Hi-Fi" aspect. Moreover, a "pack" of 2402 tweeters above middle of the dance floor, shooting in every direction, and far apart from the main boxes, may well raise phase and delay issues...

In my view a 4520 cabinet loaded with proper drivers will certainly be more "High Fidelity" as you say than a front-loaded horn (e.g. JBL 4560 or Altec 816/828) in the application you are looking at. Finally, as for driver EBP value I could not have said it better than Horn Fanatic did. But I could say it differently (blink): these type of boxes are more compatible with such things as drivers having a low Qts number (e.g. 0.17 - 0.21 or so). Best Regards to both of you.

Richard

Horn Fanatic

07-07-2017, 05:09 PM

[QUOTE=RMC;406918]Hi budney, and Horn Fanatic

A very well written and detailed analysis. It's nice to see someone in Canada who knows what he is talking about.

I recommend using the 2220 in the JBL 4500 series rear loaded enclosures only for HiFi use. The 2220 is the commercial version of the 130A, and they both share the exact same T-S Parameters with the only difference being a more stout surround. The 130A was used in one model of the C34, and it works admirably in that enclosure.

Regards,

H.F.

RMC

07-07-2017, 08:36 PM

Hi Horn Fanatic,

Thanks for you good words. I'll be out for a week of vacation. Going to spend some money on the beach in the USA. Good for your economy. I'm sure Budney will be in good hands. I'll read you guys when I'm back on July 15.

Richard

cooky1257

07-08-2017, 08:52 AM

I am looking on building a large hifi/club system for a party space I'm planning on opening, and was hoping for some advice on the finer details of this setup. A general plan that I have so far is 4 stacks around the room, each stack being:

JBL 2395 lens horn with 2441 driver
JBL 2404 or 2405 tweeter
some form of altec box, can't make my mind up between the 828 or the 816, some advice here would be helpful
some form of w bin, i'm thinking maybe double 18 berthas with eminence drivers, not enough room for a levan extension, looking for some advice
4 x JBL bullet tweeters, 2402 or 075 for an array above the dance floor, not sure about which one, again some opinions would be great

also dependant on the boxes I decide on is the available plans online, as I would be building all the boxes myself/locally

I'm planning on running this system all analogue, with class a/b amps(crown, bgw etc), classic rotary mixer (og bozak or urei) analogue crossovers and eq (RLA/GSA, urei, bryston) and modified technic 1200s

I'd always read about those old RLA disco sound systems from new york, and always thought it was in the past, until I went to a party and heard a high efficiency altec VOTT system with JBL acoustic lenses and tweeters. I was blown away by how great it sounded, and my plan is loosely based on what speakers I heard at that party. There's nowhere (that I know of close to me in the UK) that has all these speakers where I can A/B them, so hopefully someone on this forum will know the nuances of the speakers I'm looking at and can advise me on whats best.

Look here, ask questions, Lee In Montreal who posts here was a contributor, have fun, there's a great thread(among others) here including layouts of Paradise Garage, cabinet plans etc from guys who do /have done it right down to the 4x2402 tweeter rigs; http://forum.speakerplans.com/levan-horn-extension_topic58957_page3.html

budney

07-10-2017, 07:17 AM

Thanks RMC for the first hand detailed account of the good old days, great stuff! I've got a few comments/questions for you

Now some comments regarding the above. First, though I really like their sound, I still think one has to be somewhat sadistic to himself to want to build horn-loaded cabinets on your own: too difficult, too much time, too large, too heavy, too costly, etc. I hope you have a large and well equipped woodshop along with a lot of muscle. Also, finding GOOD plans on the Web MAY be difficult. JBL never published official ones since this was probably a patented design.

I agree that is a mammoth task to build a load of horn loaded cabs, but my brother in law is an excellent carpenter and the workshop where we work is well equipped for the task. Also the building next door to the workshop is a PA company that regularly build their own speakers so I feel confident I have the right resources, now I just need to find the time! but i'm happy treating this as a labour of love for quite a while.

Second, finding proper drivers for these cabinets could be quite a job in terms of availability and suitable Thiele/Small parameters. JBL 2205 drivers are long gone (except for my still original and working pair from 1981!) and if you can find some they will probably have been reconed to something else like 2225 (not same Thiele/Small parameters, but some members have said they used it successfully). The other driver later recommended by JBL for 4520 cabinets was the E-140 which has T/S pretty close to those of the 2205. Again, they will probably have been reconed with who knows what. Adventurous fellows, like my friends who built these cabinets, did also use JBL's K-140/K-145/E-145 for their longer cone travel capability (X-max) so DJ's could extract from the cabinets every drop of bass output possible in use/abuse... The parameters of the K/E-145 were somewhat off for ideal performance but since it had even more cone travel capability that prevailed over reason and anything else... Fellow member Horn Fanatic did suggest in the past the 2220 driver was suitable here re T/S and I agree with that, however the 2220 would not survive long the abuses in the field(Xmax 2mm), and was never recommended by JBL for this application. However, 2220 was THE choice for front-loaded horns such as 4550/4560.

All these stats and numbers don't mean much to me...but I've bought the yamaha handbook so will study up! I think I'll end up with what drivers I can find the cheapest/closest. Shipping and customs for 8 drivers from the USA will surely add up quickly...and that's on top of what I'd have to shell out for 2 pairs of JBL 2395s and drivers if I ever find them!

Third, my advice if you want new drivers for these boxes is to look-up the T/S for 2205H/E-140 on JBL's driver T/S parameters list (jblpro.com) and try to purchase 15" drivers of proper dimensions and with as close as possible T/S as those of the two above, but preferably with higher Pe and X-max (min. 5+ mm) numbers since you seem to want to beat the hell out of the boxes to make lots of noise... Unless you use subwoofers, which personnaly I wouldn't do since it's not really required in Disco music, as in cinema sound for example, and not seen much in the good old days. Remember, Disco is more a matter of some amplitude in LF response, than very deep bass. Many people mix-up these two different things.

I am planning to use subwoofers for this system, I may be designing it with disco as the main genre, but it will be a dance music system at heart. I feel like most dance music, especially from the 80s onwards like house music etc when drum machines arrived, would benefit from the extra reinforcement of the subwoofers. If it was purely 70s disco then I don't think I would bother, but I'm a big fan of the garage/new york style of 80s disco, which was written for dance floors with the huge subs! Also I expect that at some point more modern dance music may be played occasionally, and without subs the modern stuff would not hit as hard as it should.

Fifth, In any case, clever member Horn Fanatic gave you a pretty damn good suggestion with his idea of LF Stanley Screamers, which I didn't think of and haven't heard of for quite some time... Yeah, Stanley Screamers! If my memory is correct, these were developped by Altec Sound Contractor Stanal Sound USA in conjunction with Altec Lansing many years ago, right HF ? But they may not be easily available in the UK (location indicated by budney). BTW I'm glad Horn Fanatic (a knowledgeable horn guy around here) is keeping an eye on me in this Thread, this way I have to keep giving no less than 110%, otherwise he could be tempted to nail me to the cross, which is fine if I screw-up things. So far so good, HF ? My humble suggestion for subwoofer, which as said before I don't see as necessary, also to save some money, would have been something along the lines of JBL 4645C Cinema Sound Sub with 2242H 18" driver or even 2x15" cabs properly loaded (e.g. E-V DL 15W type, among many others).

BTW from the Disco era I also remember seeing some Cerwin-Vega setups made around B36A and L48 something folded-horn cabinets. They still exist with different model numbers and some modifications. I can remember only one Club that used Altec Lansing equipment, it wasn't used much in Canada...

This is what I'm finding most difficult to understand...from the info I've found online about the Stanley Screamer subwoofers, they are a ported reflex box? Is that right HF? From what I've read online, again this might be completely wrong, is that you don't really want to use direct radiating boxes for dance floor subs. But again all I have experience of when working in clubs is folded horn double 18 subs, never of direct radiators. I feel like the full range system I want to build should be quite 'high fidelity', perhaps the subs don't need to be? Again I'm not experienced with different types of subwoofers so I'm not too sure what to go for. I gather from what you guys have told me that a folded horn/front loaded sub would not be right for me because of the throw/dispersion that cab produces? From what I've read, quite a few clubs in New York used Altec gear, is there someone out there who knows more?? I can only learn so much from reading online

In my view a 4520 cabinet loaded with proper drivers will certainly be more "High Fidelity" as you say than a front-loaded horn (e.g. JBL 4560 or Altec 816/828) in the application you are looking at. Finally, as for driver EBP value I could not have said it better than Horn Fanatic did. But I could say it differently (blink): these type of boxes are more compatible with such things as drivers having a low Qts number (e.g. 0.17 - 0.21 or so). Best Regards to both of you.

The final choice I'm trying to make is to go for the 4520 or the 4530. What are the benefits of having 2 drivers in one box compared to 1? Would I be able to run them linked to the same amp channel or would it be best to have a channel per driver for those boxes? and the same goes for if I were to make subs with 2 drivers in one cab, would I need to double the amount of amplifiers? The Stanley Screamer subwoofers are all 15 inch drivers, but every sub I have worked with previously has had 18 inch drivers. I guess since I plan to have a small dance floor with stacks of speakers surrounding instead of just at one end then 15 inch drivers should move enough air?

Also will there not be phase issues with the 4520 when the front and rear waves meet? what are you opinions on that?

thanks guys :D

budney

07-10-2017, 07:22 AM

Look here, ask questions, Lee In Montreal who posts here was a contributor, have fun, there's a great thread(among others) here including layouts of Paradise Garage, cabinet plans etc from guys who do /have done it right down to the 4x2402 tweeter rigs; http://forum.speakerplans.com/levan-horn-extension_topic58957_page3.html

Hi Cooky, yes I have read that thread thoroughly. I believe Lee In Montreal was planning on cloning the JBL 2395 lens, I shall definitely be in touch with him to see if he succeeded. Have you managed to do it too? I see you aren't that far from me, if you did manage to build any boxes based on the RLA style I would love to come and hear some of them.

Thanks
Budney

cooky1257

07-10-2017, 10:56 AM

Hi Cooky, yes I have read that thread thoroughly. I believe Lee In Montreal was planning on cloning the JBL 2395 lens, I shall definitely be in touch with him to see if he succeeded. Have you managed to do it too? I see you aren't that far from me, if you did manage to build any boxes based on the RLA style I would love to come and hear some of them.

Thanks
Budney
No Bud, just pointing you at another source,
another direction.

Horn Fanatic

07-10-2017, 03:44 PM

Thanks RMC for the first hand detailed account of the good old days, great stuff! I've got a few comments/questions for you

Also will there not be phase issues with the 4520 when the front and rear waves meet? what are you opinions on that?

thanks guys :D

Greetings, budney -

Allow me to explain what I believe is the "phase issue" you're concerned about.

Within a rear loaded horn design is the chamber the driver resides in. Technically, it is considered an acoustical low-pass filter, with a 6dB / Octave roll-off.

The two elements that make the chamber an acoustical low-pass filter are the throat area and chamber volume. The throat area constitutes a mass, or as an electrical analogy, an inductance. The chamber volume constitutes a compliance, or as an electrical analogy, a capacitance. When introducing a cone driver in the mix, the acoustical properties of the driver must also be considered. It is in fact, another element in the acoustical impedance circuit treated no different than adding an extra inductor and capacitor to an electrical circuit. The math used to determine the roll-off frequency for an acoustical low-pass filter, and an electrical low-pass filter is the same. Both using values in Henries and Farads.

When the acoustical reactance of the throat mass is at unity with the acoustical reactance of the chamber compliance, the result is a frequency that begins to roll off at 6dB / octave. Very much like a 1st order dividing network. It is at that frequency where the phase angle between the two is a 45 degrees, meaning, the front radiation of the cone is in phase with the radiation of the horn mouth. Above and below that frequency the speaker cone and horn mouth are not in phase. It doesn't matter, because high frequencies do not emanate from the horn, as low frequencies mostly emanate from the horn. Some on this forum insist the length of a rear loaded horn is 1/4 wavelength, but never define what the frequency is. I'm sure they mistakenly believe the 1/4 wavelength is based on the horn cut-off frequency, which in not correct. Such a condition would hold true for a transmission line, or acoustical labyrinth, but not a rear loaded horn. An acoustical horn is not a resonator. In order for a rear loaded horn to be in phase with the front of the cone, the horn length must be based on multiples of odd half wavelengths of the acoustical low-pass roll-off frequency.

For example, consider a typical roll-off frequency of 300 Hz. The wavelength at 300 Hz is approximately 45". Divided by two is approximately 22.5". Three times 22.5 is 67.5". 67.5" is a typical length of a commercial rear loaded horn. If a longer horn is preferred, the next increment would be approximately 112". A longer horn will result in a larger horn mouth. A horn length of only 1/2 wavelength behaves more as a discontinuity, rather than a horn. Some might consider such, as a horn loaded port. There are however, different calculations for that arrangement.

Now, consider a Compound Horn, where there will be a short horn at the cone front, and a long horn at the cone rear. The total length of both horns, not including the chamber dimensions, is still at an odd 1/2 half wavelength. If your front horn is 8 " long, then subtract 8" from the 67 ", which leaves 59" of rear horn length. At the roll-off frequency both horns are in phase.

I hope I have been of some help.

Regards, H.F.

budney

07-12-2017, 01:32 PM

took me a few days to process all that info :blink:

When the acoustical reactance of the throat mass is at unity with the acoustical reactance of the chamber compliance, the result is a frequency that begins to roll off at 6dB / octave. Very much like a 1st order dividing network. It is at that frequency where the phase angle between the two is a 45 degrees, meaning, the front radiation of the cone is in phase with the radiation of the horn mouth. Above and below that frequency the speaker cone and horn mouth are not in phase. It doesn't matter, because high frequencies do not emanate from the horn, as low frequencies mostly emanate from the horn.

does that mean that any frequencies below the 'cut of' frequency emanating from the horn are not in phase with the cone? only at the cut off are they in phase?

For example, consider a typical roll-off frequency of 300 Hz. The wavelength at 300 Hz is approximately 45". Divided by two is approximately 22.5". Three times 22.5 is 67.5". 67.5" is a typical length of a commercial rear loaded horn. If a longer horn is preferred, the next increment would be approximately 112". A longer horn will result in a larger horn mouth. A horn length of only 1/2 wavelength behaves more as a discontinuity, rather than a horn.

what do you mean by a discontinuity?

Horn Fanatic

07-14-2017, 08:04 PM

took me a few days to process all that info :blink:

does that mean that any frequencies below the 'cut of' frequency emanating from the horn are not in phase with the cone? only at the cut off are they in phase?

what do you mean by a discontinuity?

Hi budney -

I think you may be confusing the roll-off frequency of the acoustic low-pass filter, with the cut-off frequency of the horn. They are not one in the same. A typical roll-off frequency would be approximately 3 to 3 1/2 octaves above the horn cut-off frequency.

A low-pass filter is just that. The driver, chamber, and throat parameters dictate at which frequency where no higher frequencies will pass through the horn. Essentially, an acoustic 1st order cross over. It is at the roll-off frequency when the cone front will be acoustically in phase with the bass horn as long as the total length of the horn, not including the chamber, is multiples of half wavelengths of the roll-off frequency. Instead of the typical -3dB drop in amplitude that is found with a passive crossover network, think of the cone and horn acting in tandem, behaving as a single diaphragm. Otherwise called mutual coupling.

As for the discontinuity, allow me to quote Leo Beranek from his book, 'Acoustics' page 141 Part XIII under Acoustic Elements;

"An exponential connector....acts as a simple discontinuity when its length is short compared to a wavelength, and as a transformer for acoustic impedances when its length is greater than half a wavelength". In this section he describes an exponential connector as a transition between two pipes of different areas. A horn is in fact, an acoustical transformer. A transformer that serves to transition the very high impedance at the horn throat, to a lower impedance at the horn mouth. The ideal condition being a transition to the impedance of air which is 407 Acoustic ohms. Easy enough to accomplish for high frequency horns, but not so for low frequency horns. In order for a 30 cycle horn in free air, or 4 x Pi for example, to achieve an acoustic impedance of 407 ohms at the mouth, would be so immense it would be cost prohibitive to build it. All commercial bass horns are a compromise. Mutually coupling an array of small bass horns is a more practical approach to reach and impedance of 407 ohms.

This is why horn loaded speakers are more efficient than direct radiator speakers. The acoustic impedance of a cone is considerably greater than the acoustic impedance of air.

As per my previous example, a 22.5" long bass horn lacks the length and mouth area to allow support of very low frequencies. Ergo, a short horn would behave more like a horn loaded port, than a horn.

Regards,

H.F.

budney

07-16-2017, 08:10 AM

Hi HF,

So if I'm understanding this correctly, a horn, comprising of driver, chamber, and throat, acts as an acoustic low pass filter. And the frequency that it begins to roll off is determined by their component values/measurements, like an electronic filter does with resistors, inductors and capacitors. Makes sense so far. What I'm having trouble with is understanding how the roll off frequency, which is determined by the physical components, differs from the cut off frequency. Is the cut off frequency the lowest frequency the horn can produce, and the roll off the highest due to the acoustic filter?

If you build a horn correctly, so that the length is multiples of half wavelengths of the roll off, then only the frequencies above the roll off will be out of phase with the cone?

When I was initially told about the 4520 by RMC I assumed it to be used as a midrange speaker up to 1khz. But if above the roll off its out of phase, would it not make more sense to have the 4520 electronically crossed over at the roll off frequency, and use a separate box for the midrange, roughly 100hz to 1khz? If this was to be done then would the 4520 only be used in its rear loaded horn capacity and not be used as a direct radiator?

I was also confused by the suggestion of the 4520 as I assumed that it would be a midrange box, and then a separate sub would be required. However if using a separate speaker for the midrange, I now see that what I thought would be a sub, anything below 100hz, would infact be the 4520!

Thanks for taking the time to explain this, I really appreciate it!
budney

RMC

07-17-2017, 04:39 PM

Hi Justin,

RE your Post # 11, Sorry for my late reply as I was out of the country for vacation.

"All these stats and numbers don't mean much to me..." If you don't understand what they mean and their importance in designing any enclosure the risk of project failure or poor cabinet performance increases rapidly... In General Audio Discussion Forum here there is a sticky Thread with Thiele/Small parameters definitions. You should have a look at that to at least understand the basics.

"I think I'll end up with what drivers I can find the cheapest/closest" To go with the cheapest isn't a good idea in a Sound Reinforcement system for Public Address, specially considering you seem to want very high SPL. Purchasing the closest T/S ( with more Pe/Xmax) is a must if you want to achieve expected LF performance.

"Shipping and customs for 8 drivers from the USA will surely add up quickly" In a previous post, didn't I give you a worthwhile suggestion of looking at Fane drivers from the UK ? This avoids costly shipping and customs for stuff imported from the USA...

"This is what I'm finding most difficult to understand...from the info I've found online about the Stanley Screamer subwoofers, they are a ported reflex box? Is that right HF? From what I've read online, again this might be completely wrong, is that you don't really want to use direct radiating boxes for dance floor subs. But again all I have experience of when working in clubs is folded horn double 18 subs, never of direct radiators. I feel like the full range system I want to build should be quite 'high fidelity', perhaps the subs don't need to be? Again I'm not experienced with different types of subwoofers so I'm not too sure what to go for. I gather from what you guys have told me that a folded horn/front loaded sub would not be right for me because of the throw/dispersion that cab produces? From what I've read, quite a few clubs in New York used Altec gear, is there someone out there who knows more?? I can only learn so much from reading online"

It is curious that on one hand you are so concerned about vented-box subs, while on the other hand you are so focused on Altec's 816A/828 cabinets which both use the bass-reflex principle for the low-end (down to 50 hz or so), while its front-loaded horn loads the bass driver down to 200 hz according to Altec's spec sheet!

The Stanley Screamer (2X15") type of box given to you is an intelligent alternative/option offered by HF for its cost effectiveness, performance and parts availability (in the USA), not necessarily to be the loudest guy in town. Personally, I would rather use the 421-8 LF driver instead of the 421-8 H driver mentioned. The former is a low-frequency loudspeaker (similar to JBL 2205/2225), has flatter response and lower Fs, higher fidelity, compared to the latter being a Musical Instrument loudspeaker (similar to JBL K-140) with rising response, little higher sensitivity and Fs, higher output. HF's suggestion to satisfy your appetite for SPL ?

There is nothing wrong with a ported reflex box used as a sub in a Club. I've seen that in the past with JBL's 2245H 18" driver for example. "...you don't really want to use direct radiating boxes for dance floor subs" is beyond logic and probably science too. They do have lower efficiency/sensitivity (though not lower than 816A at the low-end where bass-reflex applies)(*see below) but higher fidelity and deeper bass than a reasonable same size horn-loaded cabinet. I'm skeptical that Club "subs", made of folded-horn with double 18" as you say, are REAL subwoofers with high fidelity, unless they are pretty large in size... To get real deep bass from a horn enclosure you need a really large box (Klipschorn is a special case), this is why they fold the horn to reduce size or use bass-reflex on the rear wave to improve lacking LF performance. Therefore, a vented-box does make sense in most cases, plus Horn Fanatic rightly suggested a bass-reflex design even though he's a horn guy! Clever fellow, contrary to some others, at least HE knows when to or not to specify a bass horn in a situation, instead of being a one-track mind. Moreover, look at JBL's recent Cinema sound subwoofers for example, no horns there just vented boxes... Good reasons are involved. The low-cost of the Watt today is one of those, along with space, portability, cost/performance ratio, etc.

(*) RE Ported horn systems like Altec 816A and JBL 4560A: " The sensitivity of the ported portion of the system is no greater than a simple ported system using the same transducers in the same volume, and unless there is a specific need for the added sensitivity in the mid-bass region, it is best to use a simple ported system." John Eargle (JBL), Handbook of Sound System Design, ELAR Publishing, 1989, P. 112

Again, the distinction between amplitude (bump) and bandwidth (deeper reach in the lows) in response is of importance about what you hear or heard or think you did (on a graph, the first is vertical and the second is horizontal). Altec says "useful response to 50 hz" for the 816A, still far from subwoofer class... Did you hear amplitude or bandwidth ? Why would the subs need not be "quite high fidelity" like the rest ? If you insist on having real subs then they have to be appropriate and blend correctly with the main 4520 boxes (this does not imply nor mean the subs have to be horn-loaded).

"...you guys have told me that a folded horn/front loaded sub would not be right..." I never said that a folded horn would not be right, instead I suggested one to you (its NOT a sub): the rear-loaded JBL 4520 ! As for the front-loaded horn, I discussed the errors of mixing in same stacks for example long-throw with short-throw equipment often in random ways with no consideration for acoustical issues involved...

RE Final choice: 4520 or 4530? I'd go for 4520 since it's basically the same work involved in building the two models, but on larger panels with 4520 plus an extra hole for the second driver. However, the 4520 has deeper bass (-5db @ 42hz, VS -5db@50hz for 4530, both with 2205 driver), higher sensitivity and more SPL because of the two drivers.

RE Why two woofers in a box instead of one? Because it's a relatively easy way to increase sensitivity and maximum output in sound reinforcement. Two identical LF drivers close to each other on the same baffle and driven electrically in parallel will give you 3 db more output when both driven by the same power input, compared to a single driver. This is because two drivers close behave essentially as a single one with twice the cone area (2 x cone area = 2 x efficiency), but the overall LF alignment stays essentially the same. Naturally, such a double driver box can also take double the input power vs a one-driver box, so another 3 db of output is now possible, for a total of 6 db greater output capability. Not bad. { John Eargle (JBL), Loudspeaker Handbook, Chapman & Hall, 1997, P. 79-80}

You mentioned being used to see 18" drivers, not 15" ones. The 2x15" mentioned by HF didn't seem to be good enough. However, you should know that when two 15" drivers are used as mentioned above, their radiating surface becomes equivalent to about 1.4 times that of a single driver: 15 x 1.4 = 21. So the combined radiating surface of these two is now about equivalent to that of a single 21" driver. (Both John Eargle manuals, pages 80 and 113 respectively) Good enough air moving for you now ? Naturally, other driver specs/parameters also matter.

RE rear-loaded horn phase issue: "Phase inversion of the rear waves, due to the propagation time through the horn length, further augments response in the lowest operating range." JBL, Professional Series, Low Frequency Enclosures, May 1980, P.2 That phase inversion of rear wave is such that it works in conjunction with the front wave, not in opposition to it, since if they were out-of-phase they would tend to cancel each other, decreasing bass output.

By analogy, in a vented box the port also emits sound. A phase inversion of the rear wave inside the box occurs when going in the port and that wave comes out of the port in phase with the direct-radiating one. Low frequency output is therefore increased with port contribution.

RE Amps driving the boxes: providing the amps have enough juice per channel and capability to work at 2-4 ohms (8 ohm drivers in parallel) then I would prefer to use one amp channel per box for simpler control from Electronic X-overs for example. Would do the same for subs (2x 8 ohm drivers in parallel per cab).

Richard

budney

07-18-2017, 05:55 AM

Hi Richard,

Sorry for all the stupid questions...thanks for taking the time to explain them. I have ordered the books you recommended so I will study before trying to build anything. I'm eager to learn the actual science behind sound system design, not just throw some boxes together without any thought for why.

Re to being concerned about spl, or whether the boxes are reflex or horn loaded, or have 15 or 18 inch drivers etc. I'm sure they definitely do the job, I was just curious as to why you recommended them, when all club systems that I'm familiar with are different to your suggestions. The systems I am familiar with are moderns ones for modern dance music, and I'm just interested in why they would different from the old designs.

I have to apologise for confusing your initial recommendation. When you first mentioned the 4520 I wrongly assumed that another speaker would be required, hence my need to find another 'sub'. I see now that the 4520 would in fact be doing the job of what I wanted in a sub, without actually being a dedicated speaker for the low frequencies. When initially asking for advice in my mind I needed a speaker to cover about 800hz where the 2395 kicks in, to about 100hz where I thought a sub would take over. I thought you were recommending the 4520 as a midrange speaker only, even though you said a sub was not required...I see that I was wrong in that respect, a bad habit taken from the systems I'm used to.

An example of the club 'subs' I am familiar with are the Funktion 1 f218, folded double 18s normally running from 114hz, which is all you really see in England for dance music systems. Far from high fidelity, speakers that just sound okay 'off the shelf'. Funktion 1 also do a 21 inch sub range, quite a lot bigger than 15s! With the current dance music of today they sound fine when heavily processed, but play some old disco through them and they just don't cut it.

I would have heard amplitude, the system I heard with the altecs had lab subs for the low frequencies, so I was only thinking about the midrange when considering the altecs. I'm only still thinking about the Altec range because thats they're the only ones I've actually heard. I'm just going to start with the 4520 and the JBL 2395/2405, and take it from there. I like the idea of the stanley screamer subwoofers, if I'm still chasing those really low frequencies once I've built the 4520 then I will consider building some.

Also when I said the cheapest, I meant cheapest from the ones you recommended that have the required specs, not just any dirt cheap driver that fits the hole. I would test out the drivers first to make sure I liked them, before buying 8 of them!

Thanks
Budney

cooky1257

07-19-2017, 03:00 AM

Hi Richard,

An example of the club 'subs' I am familiar with are the Funktion 1 f218, folded double 18s normally running from 114hz, which is all you really see in England for dance music systems. Far from high fidelity, speakers that just sound okay 'off the shelf'. Funktion 1 also do a 21 inch sub range, quite a lot bigger than 15s! With the current dance music of today they sound fine when heavily processed, but play some old disco through them and they just don't cut it.

Thanks
Budney

I think you need to get out more, listen more and get in the club before the dj red lines the mixer, other excellent uk club systems come via Voyd Acoustics, TurboSound, Martin Audio and Opus. Describing Funktion1 as 'sound ok off the shelf' and 'far from hifi' is just plain wrong-I can only assume the usual idiot dj's messing with tone controls and levels as being responsible as properly installed and set up the F1 dance stack is the closest thing to huge scale hifi I have ever heard, though the latest Voyd Air Motion system (voidacoustics.com/docs/range_intros/Air.shtml)ran it very close.

budney

07-19-2017, 10:01 AM

I think you need to get out more, listen more and get in the club before the dj red lines the mixer, other excellent uk club systems come via Voyd Acoustics, TurboSound, Martin Audio and Opus. Describing Funktion1 as 'sound ok off the shelf' and 'far from hifi' is just plain wrong-I can only assume the usual idiot dj's messing with tone controls and levels as being responsible as properly installed and set up the F1 dance stack is the closest thing to huge scale hifi I have ever heard, though the latest Voyd Air Motion system (voidacoustics.com/docs/range_intros/Air.shtml)ran it very close.

I feel like I need to get out less! I work in clubs most weekends as an engineer, mainly using Funktion 1 soundsystems, and when I'm not working I'm out dancing! I've lost count of the amount of installs I've done with the resolution ranges of their speakers and blown drivers I've replaced. Also I've lost count of the amount of times I've told idiot dj's to stop redlining :D that being said we never had the dance stack range where I've worked. I've only heard a Funktion 1 dance stack once, that was in the club Berghain in Berlin. That was a meaty system, and worked well for the heavy techno they were playing, but still I was never blown away and overwhelmed by the quality of the sound. Where did you hear Funktion 1 dance stacks? Whenever I used to pull Funktion 1 speakers 'off the shelf'(or technically from under the shelves) and loaded the default settings into the processors, it was always just, meh. Once I had them in the room and could tweak throughout the night it got better, but I was still never wowed by them. Whereas when I heard the vintage jbl/altec system not too long ago, I could not believe the sonic quality of the music I was hearing. I could hear the compression of modern tracks when compared to old tracks. I could hear the vocalist take breaths before phrases, I could hear the stereo spread of all the instruments around the room. I've never gotten that from any Funktion 1 sound system no matter how much processing and tuning you do. But again I'm comparing them when playing old dance music, disco etc. For modern stuff, they are good, sometimes very good, when the dj knows how to use a mixer properly (and a good mixer, not this pioneer crap), when they have enough power to not clip the amps constantly, when the room they're in isn't an acoustic nightmare etc

We had a few old Turbosound boxes, not enough to make a good judgement on I feel. Although they are the precursor to Funktion 1, I'd imagine F1 had improved on the Turbosound range. I've heard Void a few times before, I'd say that they are better than Funktion 1, but I rarely see them to be honest, I don't know of any venues nearby that have them installed. The Martin Audio system in Fabric is the only experience I have of big Martin Audio dance systems, that was great for techno etc, but play any music with real instruments and it didn't give me what I wanted. They have the body sonic floor there, that was incredible! but I'm not in any hurry to get a load of transducers installed under a dance floor. Opus is one I've heard of, but unfortunately never heard myself, whats it like? I have heard good things about it.

One sound system that stands out to me was the RC1, from Bristol I think. They brought their speakers to a venue I was working in once, and I thought the building was going to fall down. Dust falling into peoples drinks, ruining the dj's records, that was a good system! But they ran it far too loud, they had a bucket of earplugs by the bar and they had ran out long before the night had finished. I've also heard a fair few reggae/dub systems. I find that the ones made by just a few guys, like the RC1, or the dub systems, well outperform the systems you can buy like Funktion 1, Void, Martin audio etc. But those systems are bespoke made for a specific genre, RC1 is mainly for bass heavy music, dubstep, dnb, bassline etc, and the dub ones are obvious. Thats why I want to build a system thats specific for disco and boogie! I think the bespoke systems work well in small spaces, in huge super clubs you do need the large format of the professional speaker manufacturers to have a consistant sound everywhere, as well as cater to wide ranges of genres. But in small spaces, which I think makes for a better more intimate party anyway, bespoke rule

RMC

07-19-2017, 08:22 PM

Hi, RE YOUR POST # 19

Glad you're seeing things differently. This should not only benefit yourself, but also your future system. Starting with 4520/2441/2395/2405 makes lot of sense acoustically (its a well proven recipe around the Globe) and financially. Seeing later for possible additions is not really a problem if you keep that in mind while designing the system, because subs are relatively easy to add afterwards if need be. BTW with 4520 on the floor, a number of Clubs did have 2440/2395/2405 hanging from the ceiling and angled downwards, above the woofer boxes. This to keep some sight-lines, between low and mid/high devices, to the dance floor... Since you are now talking about a small dance floor with boxes around it or in the four corners of it, this may be an idea.

"Off the shelf" Sound Reinforcement (SR) bass cabinets or 2-3 way boxes, are frequently limited to about 50-60 hz in the lows for size, weight, portability, costs, space available, etc. Most people (like Club customers) don't really hear/know the difference between amplitude and bandwidth anyway.

Output below 40 hz is not often required in Sound Reinforcement: "In most music reinforcement systems, flat power response down to 40 hz is felt to be sufficient. However, certain special effects, both in music reinforcement and in the motion picture theater, require extension of the LF bandwidth down to 25 hz." John Eargle (JBL), Handbook of Sound System Design, ELAR Publishing, 1989, P. 112

If you were to put subwoofers for < 100 hz or so frequencies as in your example, this would defeat a good part of the purpose of having 4520 boxes, since their bass amplitude from rear horn-loading, giving "punch" to the bass notes, is mostly in the 60-125 hz range! Logically, proper subs should rather cover frequencies from about < 50-55 hz. As I said before, I don't see subs being required here IF: you choose a driver with correct T/S but with more Xmax AND/OR use a steep (18, better 24 db/oct) high-pass filter on the drivers signal in the 40-50 hz range (horn starts unloading at 42 hz according to JBL). Then, you can do some tests with volume control and EQ (amplitude/bump ) in the 50-60 hz or so range depending if you have a 1/3 or 2/3 oct. EQ .

Looking at large stacks of boxes doesn't mean much if you don't know anything about the Venue size, budget, challenges, acoustics, technical constraints, etc. (i.e. the context re how/why of box choices). Big stacks may look impressive for some, not really for me. I'm more impressed by quality, well balanced sound at a reasonably loud level, not by blasting the glasses off the table. Seen way too many of those. When you provide ear plugs to customers, your example, you have a BIG problem. Not only do you get too many people in the adjacent corridor (a red flag) since much too loud inside, but also making patrons deaf kills your own business slowly. Lot of SR guys and DJ's that don't seem to understand this elementary principle!

Why I suggested JBL 4520 bass cabinets ? Because of the intended application, also since high output SR front-loaded bass horns (e.g. Altec 816A or JBL 4560A) don't have "high fidelity" very high in their list of attributes, nor in their design goals. Higher efficiency/sensitivity is the name of that game. However, a rear-loaded horn and proper driver(s) with direct-radiating front waves is an interesting compromise. Not as "high fidelity" as a vented box, but much better for the application than a "gross" front-loaded horn. It's primarily a matter of better balanced sound output between the lows and mid-bass.

My Altec data sheet for 816A doesn't show a typical frequency response curve with one of the recommended drivers used, contrary to JBL. To get an idea of what a 816A response curve may look like, one can have a look at the curve published for JBL's 4560A (although with E-145), since both boxes use the same operating principles: front-loaded horn for the driver's front waves and bass-reflex for the driver's back waves. I'm NOT saying both curves are/should be identical, but they should show similar general shape. In their optimum operating range, front-loading horns add 6 db of on-axis sensitivity to the loudspeaker according to JBL. Looking at the curve one can in fact see quite a bump in response between the 100-800 hz or so range. The sad part is that below 100 hz or so the response does not benefit from that 6 db +, therefore it is at a much lower level than the other part, which means this box will sound much more mid-bassy, compared to a 4520. See JBL, Pro Series, Low Frequency Enclosures, May 1980, P. 2 & 4. That predominant mi-bass sensitivity/sound is what made John Eargle say (quoted in my previous Post) that if you don't have a specific need for that increased mid-bass sensitivity, then you're better off with a simple ported system.

Finally, In terms of technical books, you may want to start with Yamaha's SR handbook first as it is probably easier to understand (less math) than some others, but still good. Others mentioned can follow after, in addition to Don Davis, Sound System Engineering, 4th edition.

Richard

budney

07-21-2017, 09:06 AM

Hi Richard,

Looking at large stacks of boxes doesn't mean much if you don't know anything about the Venue size, budget, challenges, acoustics, technical constraints, etc. (i.e. the context re how/why of box choices). Big stacks may look impressive for some, not really for me. I'm more impressed by quality, well balanced sound at a reasonably loud level, not by blasting the glasses off the table. Seen way too many of those. When you provide ear plugs to customers, your example, you have a BIG problem. Not only do you get too many people in the adjacent corridor (a red flag) since much too loud inside, but also making patrons deaf kills your own business slowly. Lot of SR guys and DJ's that don't seem to understand this elementary principle!

I couldn't agree more, every event that I've run I am constantly fighting the DJ to keep the SPL at safe levels. Whenever someone tells me that its not loud enough, I politely tell them to go stand in front of the stack if they want to hear it louder. If that doesn't work, then fiddling with some knobs that don't actually do anything and then asking them if thats any better normally results in a thumbs up!

My Altec data sheet for 816A doesn't show a typical frequency response curve with one of the recommended drivers used, contrary to JBL. To get an idea of what a 816A response curve may look like, one can have a look at the curve published for JBL's 4560A (although with E-145), since both boxes use the same operating principles: front-loaded horn for the driver's front waves and bass-reflex for the driver's back waves. I'm NOT saying both curves are/should be identical, but they should show similar general shape. In their optimum operating range, front-loading horns add 6 db of on-axis sensitivity to the loudspeaker according to JBL. Looking at the curve one can in fact see quite a bump in response between the 100-800 hz or so range. The sad part is that below 100 hz or so the response does not benefit from that 6 db +, therefore it is at a much lower level than the other part, which means this box will sound much more mid-bassy, compared to a 4520. See JBL, Pro Series, Low Frequency Enclosures, May 1980, P. 2 & 4. That predominant mi-bass sensitivity/sound is what made John Eargle say (quoted in my previous Post) that if you don't have a specific need for that increased mid-bass sensitivity, then you're better off with a simple ported system.

So if once I've built the 4520s, and I still find that I want a bit more in the midbass region 150hz up to 800hz, to forget the front loaded boxes and go for direct ported boxes? They would not be as efficient as a horn loaded speaker as HF explained earlier, but would be a better choice acoustically right? But then isn't that what the 4520s do above 150hz anyway, act as a direct radiator? However it's still a big IF, I'm going to see how I like the 4520s first, and it will take me quite a while to get to that point.

Thanks
Barney

RMC

07-21-2017, 08:45 PM

Hi Barney,

"So if once I've built the 4520s, and I still find that I want a bit more in the midbass region 150hz up to 800hz, to forget the front loaded boxes and go for direct ported boxes? They would not be as efficient as a horn loaded speaker as HF explained earlier, but would be a better choice acoustically right? But then isn't that what the 4520s do above 150hz anyway, act as a direct radiator? However it's still a big IF, I'm going to see how I like the 4520s first, and it will take me quite a while to get to that point."

Why would someone want more mid-bass than normal is beyond me. Prominent mid-bass doesn't sound good in my book... Try it on any speaker with an EQ, boost that a few db and listen. I hate that sound.

I would not go with front-loaded boxes for added mid-bass. If need be, I'd be more tempted to go with a closed or vented-box with single 10" (e.g. JBL 2123H) or double 12" (e.g. JBL 2202), maybe higher sensitivity single 12" (e.g. JBL 2202H), for their smoother response, higher fidelity. The JBL 2020H 12" made for maximum output with even more sensitivity, has a less interesting too much rising response. These drivers (except 2020H) have, when used in quantity mentioned above, sensitivity about on par (± 1 db) with double 2205H in the 4520, and probably less directivity/throw issues than a front-loaded horn inside a normal room.

My preference is no mid-bass boxes, use your EQ for "a bit more in the mid-bass" as you say, if that is your wish, since yes the 4520 is direct-radiator above 150 hz. Why complicate things more than required by adding another box ? More x-overs, amps, boxes, money, work, level matching, and maybe directivity issues depending on box type chosen...

Looking at JBL's response curve for the 4520 (with 2205), there's a few db bump in the 60-125 hz range, then a dip of about 3 db in the 125-200 hz or so range, then the curve is reasonably smooth from about 200 to 700 hz. Difficult, in my view, to ask for better than that in Sound Reinforcement disco application. The reason being what you will be hearing with such a response. The dip in mid-bass has the advantage of giving more emphasis sonically to the bumped frequencies in the lows (i.e. the punch in discotheque music). JBL Engineers who designed the boxes weren't stupid, they listened to it extensively and tweaked things until they got it right for the application.

Try it with speakers and an EQ: duplicate somewhat the curve with more mid-bass than usual and listen, after duplicate somewhat the 4520 type of response curve and listen. I've done it for myself with my 2205H in vented boxes. No contest, it sounds much better to me the latter way. Sound with mid-bass emphasis to my ear is crap... Authoritative lows in the 50-60 hz range are much better sounding than the other in this application.

Richard

budney

07-22-2017, 11:45 AM

Hi Richard,

Okay, gotcha, I understand. It was just purely another what if question I was curious about, as I'm used to 4 way systems. I won't bother with a mid bass speaker for now.

Thank you for all your help and advice, I really appreciate the time you took to explain this to me. I've still got a lot of reading up I want to do before beginning to build these speakers. I'm sure I'll have a few more 'what ifs' pop into my head at some point.

Best regards
Barney

RMC

07-23-2017, 08:15 PM

Following my recent posts here, I had another look at the Dark Side, the other still in business major Sound Reinforcement (SR) Company (Electro-Voice) to see if things had changed on their side since the last time I checked and their approach in terms of 18" driver subwoofers.

They have 7 series of portable SR boxes, 5 of them with "subwoofers", each including models with 18" driver(s) mounted in vented-boxes (didn't see any horn-loaded ones in their current line-up). Though I looked quickly at all of them, to represent the group I took a few specs of the Tour X premium "subs", described as world-class, tour grade... These are loaded with E-V's EVS-18S 18" woofer(s).

Model TX 1181 (1 x 18") has a stated frequency response of 45-700 HZ (- 10 db) and 50-160 hz (- 3 db). The other, model TX 2181 (2 x 18") has response of 40-1500 hz (- 10 db) and 50-160 hz (- 3 db), still far from earthquake bass, though they do have pretty high output. The 3 db down point is much more meaningful in use than the - 10 db LF response in my opinion.

Some boxes in the 5 series line-up are recommended for use with a high-pass filter in the 30-36 hz range...

For a few among all the "subs", E-V did not mention the number of db down @ hz for LF response given, as other manufacturers also do, and this is sometimes a bad sign regarding real effective response...

The "subs" seen there seem mostly limited to 40-50 hz in the bass range (- 3 db), and the best ones to 30-35 hz (- 10 db). Remember, these are all single or double 18" driver(s) boxes! Deeper bass would probably require larger box volumes and that's too penalizing in terms of size, weight, portability... That's the way it is, also probably the way it should be in SR most of the time. In this type of application, an F3 at about 45 hz or so isn't that bad, it appears still quite acceptable for SR. Maybe, making cabs with 2 x 15" look better?

This short examination does show the use of large 18" driver(s) does not guarantee very low bass from a box. Remember in a previous post I said I was skeptical about "subwoofer" low-bass from a 2 x 18" folded-horn box Budney heard/ mentioned, unless it was really large. I even asked him if he heard amplitude or bandwidth, and he replied probably amplitude...

In my view, if the above 18" driver(s) vented-boxes from E-V don't achieve real subwoofer performance, then folded-horn boxes of comparable or reasonable size with 18" drivers, will achieve it even less...

This quick review also shows home Hi-Fi subs and Sound Reinforcement "subs" are two different things. To me, such low-frequency cutoffs (- 3 db) are more compatible with the "bass cabinets" name than real subs.

In the end, however, E-V remains constant/logical with its prior mention that "In general, subwoofers for dance environments and concert reinforcement are best limited to about 40 hz. Cinema sound and special effects applications require performance to 30 hz and below." Electro-Voice, Pro Sound Facts, No. 7, October 1984, page 2, Note # 2. This quote is quite similar to John Eargle's I made in a previous post here re 40 hz felt to be sufficient.

BTW E-V's previously known Cinema Sound LF loudspeakers were TL606M (2 x 15", - 3 db @ 45 hz), and two subwoofers: TL440M (1 x 18") plus TL880DM (2 x 18"), both with - 3 db @ 32 hz, also loaded with EVS-18S woofer(s)...

OTHER MEMBER'S COMMENTS WELCOME.

Richard

1audiohack

07-23-2017, 11:09 PM

Since you are looking around, take a look at the Danley Sound Labs PGD series. This stuff will knock your socks off, it's made just for your application and it sounds great. The J94 is the best sounding large format fullrange speaker I have ever heard, ever. The fidelity is astounding and its impact is literally frightening.

These will kill anything else you have considered here with considerably smaller box count.

If by chance you think you need more sub than the PG218 look at the BC218.

Disclaimer: I have no business connection to Danley Sound Labs. I know some of the guys there and I have bought some of there products.

Barry.

budney

07-24-2017, 05:16 PM

Hi Richard

I'd be interested in what you think about the flared levan horn extensions used on W subs for club sound systems, they are supposed to run all the way down to 30hz. These are what I was basing my initial ideas on, a few clubs in the 70s and 80s had these extensions and are still spoken about today as having the best sound around. These subs were used with special crossovers(the same kind that I wish to use) that allowed the dj to play with their gain throughout the night. Also I think they were used as well as already existing bass cabinets, so the levan horn would be running at 100hz and below, but the other bass cabinets would also output 100hz and below.

I know that technically this is a big no no because of all the time aligning and phase issues, but the clubs that had the system set up in this way still worked excellently and were known for their sound. I think that set up worked because the dj had control over them. Most of the time they weren't in use, and the dj could suddenly turn them on for added effect. Also they used a dbx boom box to increase the amount of low frequency content available.

I'm not saying that I wish to use these kinds of subs, I don't think its practical for a small room like I plan on having, they'd take up most of the floor space. That being said, I do like the idea of being able to control subs in that way by using that type of crossover and boombox. The system I plan on using does not have to take portability into consideration as once its there it won't be moving again.

Some more modern systems with the flare extension
77628
77627

1audiohack

07-24-2017, 05:37 PM

This. :D This one goes to 11.

budney

07-24-2017, 06:29 PM

This. :D This one goes to 11.

sure looks mean! That top box is bizarre, never seen anything like it. Would be keen to hear proper club kitted out with that system. It also looks expensive :eek: how are they any different from all the other 218 subs that all the big manufacturers make?

Mitchco

07-24-2017, 07:28 PM

This. :D This one goes to 11. Where is the like button :applaud:

RMC

07-24-2017, 09:18 PM

Hi Barry,

Thanks for the input. I had a quick look (< half-hour) at the Danley Sound Labs Web site, and speaking for myself only (not Budney), my comments will follow below. I watched the owners' approach video and checked specs and/or data sheet for three models: PG 118, PG 218, and J1-94 (JH90) which you mentioned.

I never heard, nor owned any of their speakers so I cannot comment on their particular sound. I do trust your ears for that matter, considering the type of gear you own plus your experience as well as knowledge.

Their business is definitely to be the LOUDEST as seen in the video, though they also claim to do that with "higher fidelity". Certainly a horn addict's paradise. Craftmanship, in the USA, looks impressive to me. But as you probably know by now, I'm not a LF horn fanatic, nor a space-high SPL junkie, for the many reasons I already mentioned in this thread. However, I am capable of recognizing and admitting a horn's advantages over a vented-box, such as efficiency/sensitivity, pattern control/directivity, etc. I guess I'd rather have some of your JBL 43 series boxes than your impressive mammoth-size RCA/Community monsters (no insult intended).

Danley's business model for SPL is built on the principle of mutual coupling of drivers inside a horn box to increase efficiency/sensitivity/output, instead of coupling boxes together (as seen in video). Clever, maybe not new. Danley mentions celebrating their 10 years in business (2005-2015).

On the other hand, you may remember that E-V came out in the early 90s with the Manifold Technology Systems described as: "The MTL-4A low-frequency section features four DL 18mt drivers manifolded in a vented-box design. The MTL-4A is typically 2-3 db more efficient than horn-loaded enclosures of equivalent size in the 40- to- 80- hz region. Four drivers manifolded in each of the four band passes." E-V Pro Sound Products Catalog, 1993, P. 16. Danley's principle looks to me similar to E-V's, at first sight the difference I can readily see being that Danley applied it to horns, whereas E-V initially applied it to LF vented-boxes and later to some LF horns. Old new idea/stuff ? (Old because the basic principle may have existed a dozen or so years before, and new because of the different and/or better execution ?). In the 1996 E-V Pro Sound catalog, this time with another model, but still a Manifold Technology LF system, "The PI218L vented low-frequency system features two DL18MT... woofers facing a central manifold chamber. The air-mass load of the chamber provides 2 to 3 db more output in the fundamental 40- to 80- hz range, compared to conventional direct radiators." (P.33) Re underlinings, are these typos or dumb me (as D.B. Keele once said) has missed something here? If that 2-3 db over direct radiators may make sense for 2x18" manifolded in PI218L, but then also 2-3 db over horn-loaded (not a second 2-3 db gain over direct radiators for doubling of drivers) for 4x18" manifolded in MTL-4A ? Maybe Horn Guys and Fanatics here can shed some light on this for us? Output can be something else than efficiency.

Danley thrives on less boxes needed, compared to others, because of their huge SPL. Their marketing is based on "buy ours you'll need a fraction of the number of the others with our SPLs" type of thing. For me that means the guy sitting/standing close-by gets blasted for the remote listener to hear well. I prefer more boxes spread correctly, at a reasonable sound level each, for everyone to hear. So many people out there destroying their hearing for what glory? Hearing loss is cumulative and irrevocable...

RE PG 118 and 218 they provide a good looking operating range, but no ± db @ hz, no 3 db down point... That seems suspicious to me for a premium manufacturer. Sensitivity is given with 2.83 volts input which leads to a higher number of watts in a 4 ohms box: voltage squared/resistance = watts (2.83^2/4 = 2 w) instead of the usually accepted 1w/1m. Then their rated sensitivity of 108 db shouldn't that be 105 db ? Disapointing a bit. Also, they are heavier, less portable, than the ones mentioned in my previous post.

RE J1-94 (JH 90) "The loudest Reference Monitor" as they say. 47-18khz ± 3 db (37 hz @ -10 db). Your large JBL 43 series probably do better than that ? 148+ db spl no wonder the're loudest! 6 X 18" drivers and a "light" 720 lbs box, one needs a forklift to move this even a few feet! I'm not even sure I'd want to ask them the price of any of these... Regards,

Richard

Ruediger

07-25-2017, 04:20 AM

The dbx 120A has two stereo inputs, two stereo outputs, and a subwoofer output. Subwoofer crossover frequency is 80 Hz (120 Hz optionally). Use of the subwoofer channel is optional, original bass and synthesized bass can be routed via the normal stereo outputs as well.

The recommended configuration here is 2 or 4 of JBL 4520 Bass Horns with the JBL 2395 lens on top, and a custom built "monster basshorn" for the lows (see below). The synthesized signal ranges from 24 Hz up, so here a 25 Hz horn is not an exaggeration. A crossover of 80 Hz does not mean that the 4520s run idle at 79 Hz, okay? :)

The inner part of the monster bass, where dimensions are small, can be made from multiplex, the rest can be made from bricks. I have designed such a thing when I was a student.

I wrote "monster bass" cause such a horn is an attraction. Do not hide these pretty things :)

You may as well use other main speakers with such a setup, for example the JBL Dance 3 or Dance 5.

Ruediger

budney

07-25-2017, 06:36 AM

The inner part of the monster bass, where dimensions are small, can be made from multiplex, the rest can be made from bricks. I have designed such a thing when I was a student.

I wrote "monster bass" cause such a horn is an attraction. Do not hide these pretty things :)

A monster basshorn, made from bricks??? That definitely sounds like a monster!
I think that's a little bit overkill for what I want :D

do you have any pictures?

Ruediger

07-25-2017, 06:50 AM

A monster basshorn, made from bricks??? That definitely sounds like a monster!
I think that's a little bit overkill for what I want :D

do you have any pictures?

Look for post #1

http://www.audioheritage.org/vbulletin/showthread.php?26878-Four-way-disco-system-with-huge-basshorn

It does not resonate, it is quickly built, it is relatively cheap, so why not?

Ruediger

budney

07-25-2017, 07:15 AM

Look for post #1

http://www.audioheritage.org/vbulletin/showthread.php?26878-Four-way-disco-system-with-huge-basshorn

It does not resonate, it is quickly built, it is relatively cheap, so why not?

Ruediger

why not indeed, they look kind of like a klipsh speaker. I was initially picturing a lot bigger when you mentioned bricks.

The split scoop looks interesting, what is the benefit of splitting the horn either side of the driver like that?

Ruediger

07-25-2017, 07:57 AM

<snip> what is the benefit of splitting the horn either side of the driver like that? <snip>

Wavefronts in a horn are always bent and never plane, even in a straight horn. At hornbends things get even more complicated, as the path at the outer side is longer than the path at the inner side.

When you make a horn "flatter" or "thinner" the difference between outer and inner path length gets less. You need to make the horn wider, of course.

You get the horn flatter by splitting it.

Ruediger

budney

07-25-2017, 08:27 AM

RMC

07-25-2017, 10:08 AM

Some minor correction and missing underlinings in my post # 32 here.

On the other hand, you may remember that E-V came out in the early 90s with the Manifold Technology Systems described as: "The MTL-4A low-frequency section features four DL 18mt drivers manifolded in a vented-box design. The MTL-4A is typically 2-3 db more efficient than horn-loaded enclosures of equivalent size in the 40- to- 80- hz region. Four drivers manifolded in each of the four band passes." E-V Pro Sound Products Catalog, 1993, P. 16. Danley's principle looks to me similar to E-V's, at first sight the difference I can readily see being that Danley applied it to horns, whereas E-V initially applied it to LF vented-boxes and to some MF horns. Old new idea/stuff ? (Old because the basic principle may have existed a dozen or so years before, and new because of the different and/or better execution ?). In the 1996 E-V Pro Sound catalog, this time with another model, but still a Manifold Technology LF system, "The PI218L vented low-frequency system features two DL18MT... woofers facing a central manifold chamber. The air-mass load of the chamber provides 2 to 3 db more output in the fundamental 40- to 80- hz range, compared to conventional direct radiators." (P.33) Re underlinings, are these typos or dumb me (as D.B. Keele once said) has missed something here? If that 2-3 db over direct radiators may make sense for 2x18" manifolded in PI218L, but then also 2-3 db over horn-loaded (not a second 2-3 db gain over direct radiators for doubling of drivers) for 4x18" manifolded in MTL-4A ? Maybe Horn Guys and Fanatics here can shed some light on this for us? Also, output can be something else than efficiency.

Richard

Ruediger

07-25-2017, 10:38 AM

Hi Ruediger

When making a horn flatter, in what way does it change the sound?

Could you tell me more about your 'monster' horn, are the plans for it on that thread? what driver did you load it with?

Thanks
Barney

Hi Barney,

a bend in a horn is nothing you can easily account for when computing the horn shape. It results in a discrepancy between the calculated horn and the horn actually built. Splitting the horn makes the discrepancy smaller. That should result in a more precise sound. See a cutaway view of the Waldorf horn with its large bend at the bottom: that is anything but a well defined horn. The 4520 and 4530 suffer from the same disease.

The drivers were 18 inch JBL for sure, E155 I think. I don't have plans any more, they were quite simple anyway. It was a simple W-horn, like the Martin bin.

Ruediger

1audiohack

07-25-2017, 03:25 PM

Quickly and comments not necessarily in any order:

The EV manifold box more different than the same as a T.H. The TH's maintain a solid grip on the drivers over a wide range much like a tuned box at resonance. This drives the conversion efficiency up. When I beat on mine I watch the cones moving about quarter inch at 1200 Watts and can't believe the voice coil to cone juncture doesn't break but they don't. Mini's are done at 40Hz but I can carry two of them at once and they scale nicely.

I haven't heard the W boxes yet but they apparently have the sound signature that fits dance clubs. Cool.

The BC subs work on a different theory and really sound natural to me. The design make it possible to create a "Synergy" crossover into the full range horns where that is not possible with a T.H.

Fewer sources (above subwoofer range) is a magic bullet for sound quality in my experience and the bigger the sources the worse it gets when you have to add.

Shading:
My shop is 200 by 70 feet concrete with 28 foot ceilings. With big horns on the mezzanine tilted properly I can maintain better than 3dB difference (closer to 2dB) front to rear intil you get nearly under the horns where they fall off rapidly. Single sources in close proximity don't have to melt your hair.

Fireworks.
Search the Danley site for audio downloads. There are two fireworks recordings that are very very dynamic. A word of caution, you can ruin stuff with these recordings and the really sharp stuff is near the end so creep up on the volume.

I have played this on every system I own and my SH50's do it well with at least eight Danley Mini subs and about 12,000 Watt's total power and the Community stack with the Boxer bass bins with four 2440's and 2220's in the Levi's do pretty well but even at that, having heard plenty of full scale fireworks as all of us have, if you closed your eyes, you would never ever be fooled into thinking you were really there.

A pair of J394's with a pair of BC218's in the center could very honestly convince me. I listened in utter disbelief.

A pair of J3's cost about the same as a pair of DD6700's retail. They sound so good I just can't get over it.

Barry.

RMC

07-25-2017, 03:49 PM

Hi Justin,
RE YOU'RE POST # 28

"I'd be interested in what you think about the flared levan horn extensions used on W subs for club sound systems, they are supposed to run all the way down to 30hz. These are what I was basing my initial ideas on, a few clubs in the 70s and 80s had these extensions and are still spoken about today as having the best sound around. These subs were used with special crossovers(the same kind that I wish to use) that allowed the dj to play with their gain throughout the night. Also I think they were used as well as already existing bass cabinets, so the levan horn would be running at 100hz and below, but the other bass cabinets would also output 100hz and below.

I know that technically this is a big no no because of all the time aligning and phase issues, but the clubs that had the system set up in this way still worked excellently and were known for their sound. I think that set up worked because the dj had control over them. Most of the time they weren't in use, and the dj could suddenly turn them on for added effect. Also they used a dbx boom box to increase the amount of low frequency content available.

I'm not saying that I wish to use these kinds of subs, I don't think its practical for a small room like I plan on having, they'd take up most of the floor space. That being said, I do like the idea of being able to control subs in that way by using that type of crossover and boombox. The system I plan on using does not have to take portability into consideration as once its there it won't be moving again. "

I use Rane AC 22, stereo 2-way, 24db/oct., Active Crossovers with each channel having: master level control, low and high level controls, Mono sub (inactive on channel 2), Mute, adjustable delay and adjustable freq. 70-3600 hz. I can play with the gain as much as I want in many ways, but don't consider them as "special crossovers" as you say. Just damn good X-overs! Except for their low voltage "wall wart" transformer which I don't like, but that's the compromise to have these Rane. Replaced by AC22S, also now discontinued, sniff.

One more time, 4520 and 2395 are short throw devices, and the subwoofer shown in the 1rst pic is long throw, all in the same stack. I have already commented on mixing these "randomly" in previous posts here and elsewhere. No need to repeat myself again, refer to this thread again. The logic and technical worthiness of running both 4520 and the subs at the same time to cover the SAME < 100 hz is beyond me. BTW Beware of DBX sub-harmonic use on 4520, not appropriate. On real subs OK.

As for short/long throw on first picture you posted: since that is outdoors, the inverse-square Law would apply (- 6 db per doubling of distance from box, though not a perfect point source), as well as effects of temperature, wind, humidity. (see John Eargle, Sound System Design, P.22...). Then, image listeners sitting/standing at 100+ feet or so from the stack (remember 4520 is for 75 feet or less according to JBL), what can they be expected to hear ? Not rocket science to figure that out. Most likely the long-throw horn's BOOM, BOOM, BOOM, and a lot less from the other devices in such situation... Sounds good ? Indoors, other issues involved such as absorbtion, reflections, reverb time, etc. (Eargle, same, P. 32...)

NOTE TO RUEDIGER RE: "A crossover of 80 Hz does not mean that the 4520s run idle at 79 Hz, okay?" Hi Ruediger, long time no see. In case you are referring here to one of my previous posts where I said: "If you were to put subwoofers for < 100 hz or so frequencies as in your example, this would defeat a good part of the purpose of having 4520 boxes, since their bass amplitude from rear horn-loading, giving "punch" to the bass notes, is mostly in the 60-125 hz range! Logically, proper subs should rather cover frequencies from about < 50-55 hz." Since I usually "work" with the above-mentioned steep 24db/oct. X-overs, an 80hz freq. at that rate would mean -24 db at 40 hz, and around - 12 db at 60 hz or so, just where the 4520 "punch" starts to kick-in according to JBL's response curve. That's why I suggested a lower X-over freq. mentioned above as "about", just below where the 4520 "punch" starts, otherwise why bother building complicated 4520 boxes if you're not going to use all of their inherent impotant attributes ? Regards,

Richard

budney

07-25-2017, 06:57 PM

Hi Richard,

As for short/long throw on first picture you posted: since that is outdoors, the inverse-square Law would apply (- 6 db per doubling of distance from box, though not a perfect point source), as well as effects of temperature, wind, humidity. (see John Eargle, Sound System Design, P.22...). Then, image listeners sitting/standing at 100+ feet or so from the stack (remember 4520 is for 75 feet or less according to JBL), what can they be expected to hear ? Not rocket science to figure that out. Most likely the long-throw horn's BOOM, BOOM, BOOM, and a lot less from the other devices in such situation... Sounds good ? Indoors, other issues involved such as absorbtion, reflections, reverb time, etc. (Eargle, same, P. 32...)
Richard

I understand the acoustic principles with those boxes, and understand that mixing them up isn't acoustically sound. However, what I don't understand is how to achieve the low frequencies that those bass horns produce, without them being so large and hence having such a long throw. When you say "Deeper bass would probably require larger box volumes and that's too penalizing in terms of size, weight, portability..." then what box would be suitable? If it were a permanent install where size and weight does not matter. Also taking into account acoustic treatment of the room, which is what was done to the best clubs anyway.

I'm not going to build these speakers, I will stick with the 4520, just curious. I should also add that I'm getting most of the information about the crossovers, subs etc from a document about the Paradise Garage, known at the time to be the club with the best sound system in the world. Maybe not technically correct in every sense, but still spoken today as a legendary system in certain circles, and people lucky enough to have heard it speak very highly of it. I've attached this document, it should be able to explain things much better than I can, and I would like to hear what you think about it. Also this link has it typed up, may be easier to read through, but the attached pdf has better pictures and diagrams.

http://www.ibiza-voice.com/media/news/News/larry_levan/sound.html

That sound system pictured in the pdf has now reappeared 40 years later, in the form of the new Pioneer GS Wave range, the second picture that I posted on my earlier post. Funny how a sound system with such limitations and technical faults is still in demand today.
I guess you could make an analogy to the old analogue synths of the 70s and 80s. Some very limited, with plenty of faults, always going out of tune, not perfect at all by todays standards. But still have a specific sound that people chase today, and the vintage synth market is thriving because of it. If you go by specs alone, modern synths should win hands down every time, but they don't. Developers are now responding to this and going back to the old designs, the reissue of the minimoog being a prime example. The same could be said of old sound systems, no? Albeit slightly different, theres not really a thriving market for vintage sound systems, not for big ones anyway.

I've seen on other posts that you have some documents relating to the 4520 and rear loaded horn design, do you think you could send them to me?

Thanks
Barney

RMC

07-26-2017, 03:32 PM

Hi Justin,

In a previous post, In relation to E-V's vented-box Sound Reinforcement "subs", I did mention "Deeper bass would probably require larger box volumes and that's too penalizing in terms of size, weight, portability... (...) Maybe, making cabs with 2 x 15" look better? " There was a message here I think (driver vs box size).

As a general rule-of-thumb, larger drivers are usually more suitable for larger vented-boxes and smaller drivers to smaller ones, naturally subject to each driver's specific T/S parameters. Also, larger box volumes usually lead to lower bass frequencies than smaller volumes.

What you're trying to get here is large driver, in smaller box but with very low bass... That's everyone's dream, however it doesn't work this way in real life, unless unduly compromising efficiency (and distortion) by using a smaller driver/box to cover very low bass notes. Because of the very large cone excursions required from such a smaller combination trying to move enough air for low bass, it would not survive long in your application... Well-known Speaker Engineer W.J.J. Hoge wrote about this in an understandable way with his article "Confessions of a Loudspeaker Engineer", Audio Magazine, August, 1978, P. 47-55 (John Hoge is also the guy who started the WAVE on subwoofing with his article "Switched-on Bass", Audio Magazine, August, 1976, P. 34-40, followed by the above "Confessions...", after being flooded with letters and phone calls about reducing the vented-box subwoofer size (600L/21 cu.ft., F3 20hz, 1% eff., 15" driver). After explaining the applicable science and math, his advice was to go for less deeper bass, instead of compromising efficiency/distortion. (BTW, Hoge is also the guy John Eargle (JBL) took to review his manuscript of Handbook of Sound System Design).

As for horns, well its similar. To go deep LF horns must be rather long, therefore large also. This is why they fold the horn to reduce box size. There's no magic. You decide If you can accept/live with that. If you think the "Paradise Garage" is the way to go, then my advice is go for it, try to duplicate their system.

From the beginning, this Thread has had more and more the looks and sound of other ones here like "4520 speaker replacement" and "Skating rink bass build". With mostly theoretical questions "just for curiosity." We seem to be turning in circles since some issues already covered. You've already been given a lot of info/explanations and many box suggestions from others and myself. Time to do your homework.

Richard

budney

07-26-2017, 06:52 PM

Hi Richard

I started this thread as a way to get some technical and practical advice for what I was trying to achieve, to 'emulate' the Richard Long way of doing things. As far as I'm concerned, I've gained a huge amount of advice and knowledge (hopefully others have too), which is exactly what I was after, mainly thanks to you. I'm not going to build those huge bass horns with the extensions, I'm not going to build the altecs with the long throw. I've gained more from this thread than the other 4520 threads, if those threads had all the info I needed I wouldn't have posted in the first place. I've also bought the books that you recommended, and will read them thoroughly before doing anything. If you have any other documents that you think I would benefit from reading, the ones you are quoting from, then I would really appreciate it if you could send them to me, so I can do my homework as you say.

Trying to duplicate that system is a fools errand. The amount of time, money and manpower that went into it is on such a large scale that I can't even comprehend. Also I don't fancy running a huge super club for 1000+ people. I was just trying to make the point that even if all the technical details aren't correct, they mix long throw with short throw boxes, they have phase issues with the tweeter arrays, they have the subs running on the same frequencies as the other bass cabs, it was and is still regarded as the best sound system in the world for that application. It won awards year after year, despite not being perfect on paper. I never heard that sound system, but the one I have heard is the same style. Tweeter arrays, long and short throw boxes, subs and bass cabs playing together. It was hands down the best system I'd ever heard. When there, listening to it, I wasn't thinking about how there is phase and acoustic issues, I was marvelling at how incredible it sounded. How it was fantastic that the dj could work the subs and arrays to their liking, which is what inspired me to try and do it myself in the first place.

I believe with this kind of sound system, it is as much the person using it and playing with it in the way that its set up, as it is technical details. I believe that the added tweeters and subs, are treated more like dj effects, than they are a cohesive part of the sound system. There is the full range stacks, and then the dj can use extra subs and tweeters to their liking when they deem appropriate. That is what I think makes it stand out. You say that the 4520/2395/2405 combo was common around the world, but I had never heard of that combination before. I had heard of a Richard Long sound system. I didn't know what it consisted of, but I had heard of it.

Barney