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Old 21st August 2012, 04:07 PM   #11
sreten is online now sreten  United Kingdom
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Join Date: Nov 2003
Location: Brighton UK
Hi,

That HK paper is routinely trotted out regarding multiple subs
when its simply not applicable to the cases being discussed.

THe HK paper is about minimising seat to seat differences,
not the overall frequency smoothness, and then using
advanced digital EQ to smooth the overall response.

Fair enough, but the suggested placements are not good
(in fact they are bad) if your after the flattest response.

Given most will mount subs on the floor up against a wall
The simplest option is two subs, one placed around 1/3
along the back wall and the other ~1/3 furthest side wall.

rgds, sreten.
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There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
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Old 23rd August 2012, 12:59 PM   #12
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Join Date: Apr 2010
After checking with the other half another four towers in the living room is a no apparantly four enclosures standing around around 1.4m tall is enough .

Got a couple of days off later this week so am going to try a couple of the isobaric designs first I think , can always seal up the port as mentioned and remove the outer driver from the isobaric configuration to see what sealed sounds like . Would the auto audussey in my onkyo receiver be suffiecent eq if i try sealed?

What kind of power should I be looking at providing for a pair of the isobaric enclosures? I'd like to build an amplifier (my first one) to power them . I do have a plate amplifier to use as a temporary
measure , only 150w @ 4ohm or so but worked really well on my old box with three jl audio 15w6 tuned to 21hz if i remember correct .

From reading I see my room is less than idealy shaped , its actually more like 5 x 6 x 2.4m but not far from square . I have two locations I can put the enclosures , 1st is on the front wall either side of the AV rack under the projector screen around 1.5m from the corners which would be preferred or 2nd choice is around 2/3 along the sidewalls towards to the back of the room and my seating postion .

Thanks for the links , I will have a read when I have some spare time and thankyou for the suggestions . Will let you know how they sound

Steve
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Old 23rd August 2012, 11:41 PM   #13
sreten is online now sreten  United Kingdom
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Join Date: Nov 2003
Location: Brighton UK
Hi,

A 140W / 4 ohm plate amplifier should be fine for two isobaric enclosures.

Simple fact is it likely will be loud enough for your typical usage, if it isn't
you can increase power but only by say +3dB to 300W or +6dB to 600W
but these are marginal gains on Max SPL and your overall Max SPL levels.

I severely recommend against trying to build a high powered subamplifier
as your first amplifier project, it likely will go horribly wrong, typically.

Simply having two boxes (4ohm) versus one (8ohm) ups the efficiency
in room by 6dB, i.e. two boxes with 150w will better one box with 600W
easily, simply by having a lot lower distortion at any required SPL.

Sealed versus vented depends on the alignment you choose, and FWIW
the isobaric sealed will probably outperform a single driver sealed in the
same box, so there is little point in removing a driver from isobaric.

rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

Last edited by sreten; 23rd August 2012 at 11:49 PM.
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Old 24th August 2012, 08:33 AM   #14
mlkraft is offline mlkraft  United States
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Join Date: Mar 2012
Location: Mesa, AZ
I have a 12" Boston car sub in use in my living room. Sucky acoustics, lots of standing waves and no way to optimize.

Sounds like a good time to test a dual rear sub: wide and tight against the rear wall, perhaps even cone outward (think 3-4 " deep, 2 feet tall or so and however long it needs to be, perhaps blending the drivers int an end table or what have you.); and put the other 2 in an isobaric loaded TL or other horn-type near the front.

Iso = half the cubic volume and same db levels as a single driver.
hmmm, time to research isobaric loaded 8th order bandpass enclosures...
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