JBL 4520 speaker replacement.

[Tube Radio]

You're right I do already know what the 4520 sounds like and it's a sound I personally like.

Would be easy at some point to add one of the other types of bass enclosures that go lower than the 4520 should that be needed which can be crossed over at 42Hz using one of those Yamaha amps.

I'm debating on whether the 4560 was a good choice for the midbass cabinets due to its size.

In a way I'd like to stick with the Bullfrog cabinets or just have some Altec 816A built from the plans. That way I can still put speakers back in the wall on one side and hanging from the ceiling on the other side to have them in their original configuration.

When they originally stopped using the Bullfrogs and Yamaha horns and just had the EV cabinets on the 4520s I noticed more of an echo that wasn't present when speakers were in all 8 locations.

From looking at some of the remains of the original system I don't think there was any sort of crossover used originally that I could see unless the owner had installed a capacitor in the Yamaha horns which I didn't see any evidence of and that may explain why two Yamaha horns were missing their drivers as they probably blew from seeing a full range signal for too many years.

Those Yamaha amps will make setting up the system so much easier as the built in DSP does the crossover, EQ, delays ETC...

Now concerning the 811B and midbass cabinets I'm going to try one passive 12 db/octave crossover on one midbass and horn just to see how it sounds and if the midbass and horns are balanced with each other. If they are not I will go with another Yamaha amp for the midbass and horns.

That said if I do two 4520 cabinets side by side or stacked per corner I would need two amplifiers anyways.

Far as mounting the 811B horns I will most likely have cabinets built so I can set them on top of the midbass cabinets, although if I have some 816A cabinets built I could have the builder build in a space for the 811B horns to mount right in the cabinet unless there's already plans out there for an 816A and 811B two way cabinet.

Here's the speaker placement options I can go with









I could just get the stuff and do it like one of those huge Jamaican sound systems with stacks upon stacks of speakers



EDIT:

Is there any good plans for the 4520?

[Lee in Montreal]

4520 plans are all over the internet.

But before you go this direction, have some reading :
http://www.diyaudio.com/forums/subwo...ubwoofers.html

Startec's 18" Super bass horn seems a better choice for modern music. Tons more of lower bass. Plans are available and free. 3 meters/10ft horn = 28Hz horn in group
http://forum.speakerplans.com/super-...opic20503.html

Plenty of better bass horns than 4520 to be built.

A simple google with "bass horn" as search topic will give tons of interesting reading. Front loaded vs rear loaded horns. Compare response graphs. ;-)



18" Super bass Horn (simulated) response



JBL 4520 - Lots of 80Hz bass (great for bass driven reggae). But not much below... ;-)



So. Don't commit to the 4520s before you tested better horns... ;-) Build one. Measure it. Then compare. Your ears and chest will tell you right away which horn works best.

[Tube Radio]

I looked on the internet and saw a lot of 4520 plans but they to me didn't seem complete enough, but I'm not a cabinet builder so maybe they are indeed complete enough.

I'm thinking perhaps the 4520 used for the subs then perhaps later on adding some bass horns for under 42Hz.

[RMC]

Hi Barry (1audiohack),
I'm glad you brought-up some critical acoustic notions in this thread on March 3, on which I will expand a bit. I couldn't agree more with you with regards to skating rinks not sounding too good, that loud is easy, the fact there is some smashingly good sounding new stuff out there and that many reflective surfaces degrade sound quality. One of those skating rink existed for some time (now closed) about 20 min. from where I live. The sound was just horrible for the same reasons you mentioned. The bigger the better or the more the merryer isn't necessarily true in acoustics... Though, generally speaking, some materials like wood are more noble than cement/concrete in acoustics, except to confine low frequency noises.

"Loud is easy". Yes it is, however one has to realize at some point that by making customers or patrons a little more deaf each time, these persons won't need your services and gear anymore... Lots of big loud gear may make the DJ feel/look powerful, smart or in command, can sound impressive to teenagers, but it can also be detrimental to sound quality because of bad room acoustics, plus in the long run it's slowly killing the business. There's often many persons outside the room discussing, an indicator of too loud ?

There is no valid point in blasting people away, or the glasses off the tables. Overkill and overspending on equipment doesn't make a business profitable, the main reason why they float or fail. A skating rink is basically a business, similar to many others where logical choices must be made according to a business case and budget, including sound, but in a more challenging acoustical environment in this particular case.

"Reflective surfaces". Acoustics can be "destructive". Simple repeated hand claps in many parts of a large room are a good basic indicator of that room's reverb time. Skating rinks don't favour acoustics by design, and acoustics handicap skating rinks sound. The golden rule: to stay away from trouble. In such situations it implies to minimize interactions between room and sound, otherwise you may fail, first by not trying to be the loudest guy on the block (aggravating a bad situation), and second, by avoiding tall stacks of speakers projecting high spl sounds above people and straight out to the back or side walls for example. Yes, a good crowd of people has absorption (less if many are in the corridor !), well padded seats and some carpeting also do, reducing sound reflections bouncing around, but less reduction at lower frequencies, which often leads to a huge "boom box" effect, if the bass is let loose (too amplified/not properly controlled), a muddy peaky sound not pleasant to hear... It's incredible the number of places I went to over the last 40 years (clubs, bars, discos, marriages, parties, shows, gatherings, etc.) where the sound was simply bad. Lots of dollars waisted on piles of equipment, without little consideration to simple acoustic ways to improve. BTW some of the best sounding are simple: four mid-sized JBL Studio Monitors hanging around the dance floor, aimed at the crowd, at an acceptable SPL. Another similar one used Bose 802 with "sub" at right locations...

"Good sounding new stuff". When a remake of a room's acoustics is out of bound ($), then the only logical alternative is CONTROL of sound, by adapting/being clever on choice of equipment. This is the type of situation where professionnal acoustical consultants or sound contractors would typically specify, much more often than not, relatively small two-way dispersed directional speakers aimed directly at the audience along with some form of short throw bass cabinets in a bi-amp system, instead of the big boxes stacking solutions. It makes sense acoustically in this type of environment. The best way I know to achieve sound quality here is directivity, placement and short throw to minimize creating/amplifying reflections on every boundary. This means speakers relatively close-by projecting directly on the listeners to avoid additionnal acoustical problems, including hanging boxes if need be. To name names, E-V, JBL, EAW, Renkus Heinz, Peavey Architectural Acoustics, Clair Brothers Audio, etc. have all been increasingly going in that direction for some time by making a wide variety of new speakers better adapted to different challenging situations. One-size fits all, like in the good old days, seems pretty much gone now.

The new name of the game in this on-going trend to somewhat smaller boxes is: control/ portability/ expandability/ flexibility (various configurations, creating arrays).

As they say, it's business, only business... Since success isn't measured by DB SPL, might as well make it sound good, not primarely loud. I like the big stuff too 4520/4560/4550 when the situation requires it.

Richard

[JeffW]

I have one system comprized of RCA 9462 bass horns with Community M80 mid bass horns and Community RH60's that sound stunningly good. But, they are seven feet wide and 11 feet tall, and one J1 will best them in any metric, except cost.

To wit:





About the most fun I've had in years, stereo-wise.

[Tube Radio]

With smaller speakers comes less efficiency requiring more drive power, but with horns the drive power is much less.

Also I do know how the rink sounded when the whole original system worked properly and at least to me it did sound very good until they replaced the speakers on the 4520s with Electrovoice speakers and stopped using the ones hanging from the ceiling and mounted in the wall.

Once they did that I could hear an echo at the middle of the rink and it did not sound good. Plus the speakers had to be turned up much louder and the sound right by the speakers was way too loud.

If the horns like I am planning on using are set up right they will sound very good.

I don't really want to go the smaller less efficient and to compensate throw gobs of power at the speakers solution as I DJ at a rink like that and the sound isn't all that good with the subs requiring a lot of power.

Just because a system is overbuilt does not mean it has to be played at maximum volume.

Like the ministry of sound sound system that was mentioned earlier. Their current system is 25,000 watts per speaker stack, yet they never use nowhere near that much power.

Why so powerful? Because an amplifier used at or near maximum power all the time won't sound as good or last as long as an amplifier of twice the power used at half its maximum output power.

[RMC]

Famous horn speaker designer Paul Klipsch once said "what the world needs is a good 5 watt amplifier", with regards to is well-known La Scala and Klipschorn speakers (104-107 DB sensitivity)...

Richard

[BMWCCA]

Famous horn speaker designer Paul Klipsch once said "what the world needs is a good 5 watt amplifier"...

He also cried "Bullshit" a lot, but I'll refrain from that here!

[1audiohack]

Famous horn speaker designer Paul Klipsch once said "what the world needs is a good 5 watt amplifier", with regards to is well-known La Scala and Klipschorn speakers (104-107 DB sensitivity)...

Richard

I have to push the "Bull Shit" button on Paul, no amp can fix a La Scala haha!

Killing people with SPL is no doubt bad practice and I do not condone it. I do like the get up and go of a well tuned large format speaker system, as you may have guessed.

The shop in the picture Jeff posted is a 200 by 68 foot concrete box. The solution to acceptable sound inside is keeping the sound off the walls and on the floor as you have said, and a single stack source up high makes that a lot easier. The HF is a 60X40° horn ≈20 feet above the floor. Looking through the horn, the top line points ≈10-12" above the floor line ≈185 feet away. This naturally shades the output so the closer one gets to standing underneath the horn, the output is reduced in proportion. There is right about 2dB SPL from the front of the shop to the rear, the sound is surprisingly very well balanced. You have to be within 20' of the far wall to pickup any backslap and you really have to listen for it.

There are two 55 HP CNC lathes near the center of the floor and the noise on the floor changes throughout the day. To deal with this and other DSP chores there is an old BBS 8810 that employs ambient noise compensation. There is a $50. Behringer mic hanging about 100' from the speaker stack. With this set up properly the sound system level stays where one can hear it anywhere any time.

I am not trying to run away with your thread TR. Just wanted to share a working solution to another acoustically challenging environment.



I agree Jeff, we need to do that again!

My best All!
Barry.

[Lee in Montreal]

Why so powerful? Because an amplifier used at or near maximum power all the time won't sound as good or last as long as an amplifier of twice the power used at half its maximum output power.

Indeed.
Older people, especially DJs, will remember fried voice coils because of too small amps being used, clipping all the time and outputting DC. Wondering if 5W amps would have worked better... ;-)

Probably what "DC" meant in the Crown DC150 ;-)

[JeffW]

The stacks I posted above were running a touch over 5 watts



You could feel the music from here when they were opened up a bit

[Lee in Montreal]

The stacks I posted above were running a touch over 5 watts



You could feel the music from here when they were opened up a bit

How much db did you have at, say, 40Hz ? What about peaks? Would that be enough to impress drum'n'bass or EDM dancers in a club? ;-)

Lee

PS are these 5W amps in the picture? if more, why then? ;-)

[Tube Radio]

1audiohack, that's ok. Every bit of advice helps.

Wondering if I should use some sort of DSP box such as a Mini DSP before the amplifiers that can work with a room measurement mic in order to optimize the whole system to the room? I could then just use the built in DSP of the amps for the crossover and limiting with the Mini DSP doing the rest.

Think the plan will be this.

4 or 8 4520 cabinets for the bass to 90Hz or whatever is the best crossover point for them.
4 4560 cabinets for the midbass to 800Hz or 8 Altec 816A cabinets for the midbass to 800Hz (depending on if the owner already bought those 4560 cabinets.
4 or 8 Altec 811B horns with BMS 4550 compression drivers.
8 Yamaha PX3 or PX5 amplifiers (depending on just how much headroom is needed)
Maybe Some sort of DSP box that can work with a room measurement mic and software.
A DJ style mixer

Lee, those berthas look awesome. How low in frequency do they go? If low enough is it possible to just add one to one end of the rink crossed over at 42Hz.

If I do add one that may come later as needed.

The idea is for this to be the best sound system out of any rink in the local area and with the advice I've gotten here and my knowledge of how to set up sound systems and what sounds good I believe that I can achieve that goal.

Far as using 8 midbass and horn speakers I can just parallel two each per amp channel unless it is best for each speaker to have its own amp channel.

Setup will be easy as I'll be able to set one amp up then transfer the settings to the other amps.

If the audio cabling is still there I think each of the four original amps were fed in parallel.

Will that be ok? Also is there any DJ style mixers that output a mono signal or will I need a box to take care of that?

I do see a problem using only one 4520 per speaker stack. That is I'll need 6 amps if I run the 811B horns on an amp channel.

Using two 4520 per speaker stack will eliminate that issue, but I'll then need 8 amps.

Now if I use the PX5 amps I'll have 500 WPC 8 ohms and would need two per speaker stack for sure.

Thinking the PX5 would be better anyways as the woofers I'm going to use with the 4520 cabinets are rated at 500 watts and with the PX3 running them in 4 ohms I have 500 watts max and the amps will be running near maximum unless I'll never need anywhere near 500 watts at sane listening levels given the efficiency of those cabinets.

[BMWCCA]

Probably what "DC" meant in the Crown DC150 ;-)

Not familiar with a DC150 Crown.

D150, yes. DC300, yes. Just not DC150. I've run an original D150 (the one without any front panel) for over 40-years without issue. The only blown tweeter I've ever had is an 075 when I didn't know any better and was pushing my 030s with a Kenwood receiver. JBL repaired it under their "lifetime" warranty terms but alerted me to check for a "high-frequency oscillation" from my amp. I just sold the Kenwood instead, and that original 075 is still working today. So is the Crown.

[Lee in Montreal]

Not familiar with a DC150 Crown.

D150, yes. DC300, yes. Just not DC150. I've run an original D150 (the one without any front panel) for over 40-years without issue. The only blown tweeter I've ever had is an 075 when I didn't know any better and was pushing my 030s with a Kenwood receiver. JBL repaired it under their "lifetime" warranty terms but alerted me to check for a "high-frequency oscillation" from my amp. I just sold the Kenwood instead, and that original 075 is still working today. So is the Crown.

Hey buddy.

You are correct... D150 and DC300. My bad. It was a very long time. ;-)