Subs blowing

[Music is life]

A local night club has 2 dual 15" subs placed one on each side of the DJ booth.

They do blow their subs from time to time. I heard them and they do not have much depth to the sound. Sounds like the typical 50Hz rapid drop.

They do have a "bass-frequency subharmonics generator". So I suspect that they are not reaching the thermal limits of their speakers but are reaching the exertion limits.

IMO they need subs that extend a bit lower and need to be placed together and closer to a half corner of sorts which is available for further boundary reinforcement.

I suspect that they are using the "bass-frequency subharmonics" because of the shortcomings of their dual 15's and set up. Suspect that they will not need to use it with subs that naturally go lower and are better placed.

Can anyone tell me if these "bass-frequency subharmonics" generators put a lot of extra pressure on subs? I have no experience with these.
Also if the speakers are not putting out those frequencies it seems that they are of less benefit in such an application, right?

Thanks in advance.

[billfitzmaurice]

A local night club has 2 dual 15" subs placed one on each side of the DJ booth. That's mistake #1.
http://www.prosoundweb.com/article/in_search_of_the_power_alley/

Mistake #2 is their likely failure to use boundary loading, mistake #3 they probably have them far enough away from the rear wall to create suck-out losses via Allison Effect.
http://www.padrick.net/LiveSound/CancellationMode.htm



They do have a "bass-frequency subharmonics generator".
Mistake #4. Using those things the only wonder is that they don't blow drivers on a nightly basis.

[Music is life]

That's mistake #1.
http://www.prosoundweb.com/article/in_search_of_the_power_alley/

Mistake #2 is their likely failure to use boundary loading, mistake #3 they probably have them far enough away from the rear wall to create suck-out losses via Allison Effect.
http://www.padrick.net/LiveSound/CancellationMode.htm



Mistake #4. Using those things the only wonder is that they don't blow drivers on a nightly basis.

Good info, thank you.

[Paul O]

The existing subs could be more than adequate if setup properly, don't write them off just because they're only 15's. It's entirely possible the subs are perfectly placed right now to produce almost total cancellation below 50hz, and it wouldn't matter how much more subbage you added in the same locations.. the results would be the same. Get the room figured out and test some alternative locations before buying upgrades, and pitch that sub synth in the trash. You should also take all system control away from the DJ.. besides what he has on his battle mixer, and install a system limiter so the speakers cannot be overdriven and lock it away with the amps so the system protection cannot be bypassed.

[Music is life]

The existing subs could be more than adequate if setup properly, don't write them off just because they're only 15's. It's entirely possible the subs are perfectly placed right now to produce almost total cancellation below 50hz, and it wouldn't matter how much more subbage you added in the same locations.. the results would be the same. Get the room figured out and test some alternative locations before buying upgrades, and pitch that sub synth in the trash. You should also take all system control away from the DJ.. besides what he has on his battle mixer, and install a system limiter so the speakers cannot be overdriven and lock it away with the amps so the system protection cannot be bypassed.

Thanks Paul.

Their sub amp is the Peavey 4080hz. So in addition to the sub harmonic thingy my concern is also that this amp does not have a HP filter built in.

Does anyone know if this amp has a HP filter (like 30Hz).
(If not can someone point out a stereo 2 way electronic crossover that has a HP filter. No they do not have a electronic crossover either unless some filter is in the sub harmonic thingy. :rolleyes: )
Can anyone recommend a system limiter.

Thanks in advance.

[billfitzmaurice]

No they do not have a electronic crossover either
And the mistakes just keep on coming. :(
So, who did the install on this? Howard, Fine and Howard?
http://upload.wikimedia.org/wikipedia/en/thumb/b/bc/Stoogelogo.png/300px-Stoogelogo.png

[Music is life]

And the mistakes just keep on coming. :(
So, who did the install on this? Howard, Fine and Howard?
http://upload.wikimedia.org/wikipedia/en/thumb/b/bc/Stoogelogo.png/300px-Stoogelogo.png

I do not know of any install in my area that is done half way correctly :eek:
All of the subs are separated.
All of them are placed badly.
When they do have an electronic crossover half the time it is set higher that what is needed for the tops they have like 160Hz.
Oh well.

[Paul O]

Man... these things never had a chance. Get a PA processor(Berry DCX2496) it has everything you need.

[billfitzmaurice]

I do not know of any install in my area that is done half way correctly :eek:
All of the subs are separated.
All of them are placed badly.
When they do have an electronic crossover half the time it is set higher that what is needed for the tops they have like 160Hz.
Oh well.Get your act together and start doing audio consulting. I get $75 per hour with a 2 hour minimum charge.

[dwigle]

This is very interesting. I frequently see bass bins used under MT or MTM speakers.

I was considering building a pair to act as subs and stands for a pair of Nat Ps. Are they subject to the same comb filtering? how can it be avoided? thanks

[billfitzmaurice]

This is very interesting. I frequently see bass bins used under MT or MTM speakers. Unfortunately pro-sound subs don't come with user manuals that tell one the correct way to place them.


I was considering building a pair to act as subs and stands for a pair of Nat Ps. Are they subject to the same comb filtering? how can it be avoided? thanksWhat's a Nat P?

[dwigle]

Unfortunately pro-sound subs don't come with user manuals that tell one the correct way to place them.

What's a Nat P?

Natalie P - popular design MTM for home audio using a pair of Dayton RS180s and an RS28.

I had thought comb filtering was a problem at mid and tweeter xover frequencies and not so much at 25-80 hz.

How does comb filtering effect full range speakers that have subs built in?

Or for that matter many of the monkey coffins of the past with 12" and larger woofers - like the jbl 100?

[Paul O]

The wavelength of sound at sub frequencies is very long so while this means relatively small driver seperations (several feet) won't have much of a negative effect on the direct radiated sound from these drivers, unless you have a perfectly anechoic chamber for a listening room, reflections and the interference patterns created by them will play a major factor in bass production. Multiple drivers create multiple interference patterns which overlap and create even more interference patterns.. and a typical home listening room is pretty small so reflections play a major role and sub or bass driver positioning is everything.

[billfitzmaurice]

How does comb filtering effect full range speakers that have subs built in?

The same way it affects separates. But in the home, where boundaries and cabin gain affect response as much as anything else, it's not nearly as much a concern as in the large rooms where pro-sound gear is generally employed.

[dwigle]

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