RLA style JBL/VOTT Club System, advice needed

[budney]

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.

[RMC]

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]

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?

[RMC]

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]

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]

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.

[Ruediger]

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]

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

do you have any pictures?

[Horn Fanatic]

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

RMC -

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.

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.

HF

[budney]

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]

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]

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]

[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.

[budney]

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

[Horn Fanatic]

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

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.