Labsub or HLa at 17Hz? - diyAudio
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Old 25th November 2008, 02:56 PM   #1
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Location: stockholm
Default Labsub or HLa at 17Hz?

I have been asked by a theatregroup to do 17Hz but how well does the labsub do 17Hz and what power can it be fed?
I dont know how the signal is shaped and for how long the signal will be on.
Does anyone have any experience of anything like this?

The other alternative would be JBL HLA subs, but i dont like the idea of frontloaded that low at any serious soundpressure.
http://www.jblpro.com/catalog/suppor...=233&doctype=3
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Old 25th November 2008, 07:25 PM   #2
jbell is offline jbell  United States
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labsub is a PA sub, aka 40hz and higher. 17hz would require an incredibly long path for a FLH.

By chance are you looking for something like this??

http://home.comcast.net/~jhidley/Subwoofers/index3.html
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Old 25th November 2008, 07:28 PM   #3
simon5 is offline simon5  Canada
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For 17 Hz, I'd recommend huge ported enclosures or a Tapped Horn.
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Old 25th November 2008, 08:26 PM   #4
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There wont be any newbuilds for this , so these two are the only alternatives at hand.


From some tests with hornresp. It seems that the labsub can do any frequency limited to 225 watts , but can handle more than that both below and above the 32,5Hz resonance...

Livetests with real amps infront of the theatredirector will be done tomorrow...

So, what power is it possible to run the labsubs on without burning the coil "with almost DC"? Will it handle 400W safely?
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Old 25th November 2008, 08:45 PM   #5
jbell is offline jbell  United States
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The problem is a lab sub at 17hz, is basically a small sealed box direct radiator, that just happens to go through a horn path.

If you take any program that can model a small sealed box with a lab12 driver -- that's what you should get. (which is what hornresp shows)


now, if you had some 4x8 sheets of ply, and could add about 8' of length to your labs (following the horn flare) you might have something.
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Old 25th November 2008, 09:50 PM   #6
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Hi
If you find products that have half space measurements, you can compare them to these, some boxes I designed that are usable at 17Hz.
Warning I am the manufacturer but the measurements are real and easily repeatable.
The Imax cinema at Navy pier in Chicago has for of the first boxes for lf.

http://www.danleysoundlabs.com/pdf/T...ec%20Sheet.PDF

http://www.danleysoundlabs.com/pdf/D...ec%20Sheet.PDF

http://www.danleysoundlabs.com/pdf/SPUD%20intro.pdf

Best,
Tom Danley
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Old 25th November 2008, 10:28 PM   #7
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Tom's DTS is an excellent solution to your problem. The closest
thing that the diyaudio forum has produced is a double folded
tapped horn as designed by MAVO and folded by me. With a total
path length of 5.5 meters, Hornresp says it's down -5dB at 17 Hz.

How much power do you need?
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Old 26th November 2008, 12:55 AM   #8
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If you need a 17 Hz sine wave sound, the above cabinet can be modified (stretched) to put out 115 dB at 1 meter.

This could be built for less than $300 USD.
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Old 26th November 2008, 01:25 AM   #9
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Quote:
Originally posted by jbell
The problem is a lab sub at 17hz, is basically a small sealed box direct radiator, that just happens to go through a horn path.

If you take any program that can model a small sealed box with a lab12 driver -- that's what you should get. (which is what hornresp shows)


now, if you had some 4x8 sheets of ply, and could add about 8' of length to your labs (following the horn flare) you might have something.
(Yes you are correct, it somehow slipped my mind when i was thinking of the HLAs)

If it was possible under these circumstances, i would definately build some extensionflares or better yet start out fresh with a TH.


Quote:
Originally posted by Don Snyder
Tom's DTS is an excellent solution to your problem. The closest
thing that the diyaudio forum has produced is a double folded
tapped horn as designed by MAVO and folded by me. With a total
path length of 5.5 meters, Hornresp says it's down -5dB at 17 Hz.

How much power do you need?

Danleys constructions are well known and has been discussed for several years, but they arent aviable over here.

I dont actually know how much i need, the theatredirector dont have a clue...
And since i dont know what kind of material they are going to play so who knows if 17Hz is important at all.
-They just asked for a 17Hz demo tomorrow morning, a few hours from now...

So will it be safe to run that demo with 400W and a narrow notch at 32,5Hz? can i maybe use more than 400W safely?
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Old 26th November 2008, 01:29 AM   #10
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Join Date: Mar 2004
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Quote:
Originally posted by Don Snyder
If you need a 17 Hz sine wave sound, the above cabinet can be modified (stretched) to put out 115 dB at 1 meter.

This could be built for less than $300 USD.

Thanks Don!
I will save those drawings for the next time.
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