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Old 24th November 2001, 05:08 AM   #11
Wizard of Kelts
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I ran the Blueprint 1503's numbers-those provided by the DuMax test Thomas W printed on this thread: subwoofer design problem

I got pretty much the same results as gum. At 18 Hz., in a 3.25 cu. ft box, the 1503 will be putting out about 104 dB at 1000 Watts input, or 107 dB at 2000 Watts input. The 1503s are rated for "1000+" Watts, but there are always instantaneous peaks.

A ported design would work better. About 6 dB more output in the same size box.

For what it is worth, the low final Q-about .5 in a 3.25 cu. ft. box--will give extremely undistorted bass-very fast and quick. Some loudspeaker designers design their sealed boxes for a final Q of about .5 for that reason. So it would be wrong to say that the 1503 cannot be used in a sealed box of that size.

But you will get more output from a ported box tuned to 18 Hz.

At 16 Hz, "room gain" amounts to about 9 dB, so it should be very close to that at 18 dB. This would bring the output at 1,000 Watts up to 113 dB or so at 18 Hz. for the sealed box.

I have heard mention that a low Q sealed box-which this 3.25 cu. ft. box is-merges into room gain better than a ported box, but I am unfamiliar with any details of that theory.

[Edited by kelticwizard on 11-24-2001 at 12:11 AM]
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Old 24th November 2001, 07:08 AM   #12
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Tom Nousaine frequently says

Quote:
"Sims are for show, 1 meter ground plane measurements are for go"
People can 'bench race' computer models till hell freezes over. But until you actually build something with one of the new high excursion drivers it's all just speculation.

The BluePrint 03 drivers will work fine in sealed enclosures. The 1203 for example can be used in a box as small as 33L and won't need Linkwitz-Transform circuit to get a relatively low "Q".

[Edited by ThomasW on 11-24-2001 at 11:48 AM]
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Old 24th November 2001, 07:37 AM   #13
pkgum is offline pkgum  Australia
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those statistics came from a custom design in unibox with guessed Vb(cant remember what I put in..i think the qtc was around 0.5) at 1000W power...but they were just there to show that BPs in a sealed box have much less ouput than in a ported box

you guessed right...i didnt buy the book..i went straight to building...as you had said, the posted info is enough to get me going....book later

can someone answer this...
How do manufacterers meaure freq response?
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Old 24th November 2001, 05:03 PM   #14
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gum

Mfgr's should be publishing 1 meter anechoic FR plots.

Regarding the Servo 15, if you want to copy one then just use a 1503. You must add an appropriate custom LT circuit, have a big amp and tons of EQ. That's what the mfgr's are doing that use 15" or 18" woofers in tiny boxes. Servo circuits are also helpful when cramming drivers in boxes that are too small.

Understand is that generally speaking servo designs, and designs placed in too small a box, EQ'ed with LT circuit and other hardware, won't play especially loud. Most of them will go fairly deep, but again there's not much software out there containing info below 18-19Hz
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Old 25th November 2001, 10:42 PM   #15
Ignite is offline Ignite  Canada
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Separate related question:

Two woofers facing out on opposite sides of the box like the Krell MRS... what happens when they are wired out of sync, so one pushes the other?
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Old 26th November 2001, 02:03 AM   #16
Wizard of Kelts
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Ignite:

If I understand you correctly, one would be going in toward the box while at the same time, the other would be pushing out.

I believe they would cancel each other. It would be like eliminating the box entirely and just having two unenclosed speakers in a room.
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Old 26th November 2001, 06:22 AM   #17
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kelticwizard,

in theory that is how it works because in theory the air pressure inside the enclosure remains constant but in practice it varies quite a bit....... this occurs because the compression caused by the driver whose cone is moving into the enclosure IS NOT EQUAL to the rarefaction caused by the driver whose cone is moving outward.

Such are the joys when working with air which is inherently single-ended.
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Old 27th November 2001, 03:51 AM   #18
Ignite is offline Ignite  Canada
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There's a new candidate coming out soon from Adire.
The Brahma, available in 10", 12", 15" and 18" starting in december.

The 12" offers 1600W RMS power handling 27.32mm one way xmax (DUMAX) and specs similar to other insane-excursion drivers.

http://www.adireaudio.com/cd/brahma_series.htm

Personally I'm not a fan of these drivers. Higher FS than conventional subwoofers makes them useless without EQ and thus extremely inefficient. I prefer a larger box, maybe multiple drivers, if it's not so power hungry. But that's just me.
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Old 27th November 2001, 04:10 AM   #19
walker is offline walker  Australia
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Ignite, you're half way to an isobaric enclosure, but missing one box.
What you will get is a lot of cancellation at low frequencies, (which is about everything a sub puts out). Also a good chance of damaging the drivers if they pole, (that is the voice coil or cone hit the magnetic poles, OUCH).
Definitely not a good idea.

Regards WALKER
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Old 27th November 2001, 04:31 AM   #20
Wizard of Kelts
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Ignite:

The new Brahma seems to be 3 dB down at 19 Hz in a 3 cubic foot box tuned to 19 Hz. Granted, the speaker is only 84 dB @ 1M/W. It still looks like a good subwoofer in a very compact box.

[Edited by kelticwizard on 11-26-2001 at 11:57 PM]
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