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Author Topic: Adding delayed out of phase subs to decrease room modes  (Read 11636 times)

Iain.Macdonald

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Re: Adding delayed out of phase subs to decrease room modes
« Reply #20 on: March 23, 2011, 03:07:24 pm »

In the search of SQ in the bass region (in a room) I've crossed the following approach:

To add a second set of subs, located on the opposite wall of main subs. Then to delay the signal to them by the time (a few mSec) it takes the sound to travel from the main subs to the opposite wall subs (the proposed second set). To invert the signal to the second set of subs.

Theoretically, this lets the sound travel through the room/venue then it is absorbed (almost completely) and does not get reflected to cause modes and all kinds of problems.

Has anyone tried this approach and what are your opinions on this? 

Thanks,
Herman

Herman,

500=22'≈ per side That's not a very big room! You are well within the guidelines for the multi-sub approach that Toole and Olive describe.

The most accurate sub for your listening room would be a closed box. But you mentioned techno, so the output levels and sound quality may not be to your taste.

Iain.


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Herman Chigrin

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loudness -- types of music
« Reply #21 on: March 23, 2011, 09:35:33 pm »

First of all, I'd like to thank everyone for dissecting my problem.

The loudest I would need is 110 to 115db. However, I do NOT like to push the system to it's limits so at those levels I want the subs to be in "relaxed" mode and have some headroom.

If I choose to have two subs (placed in corners behind speakers) then I have 3'x2'x8' available volume for each sub = 48 ft^3 per sub

The music to be played is Classical, Jazz and Techno.

As far as HORN subs I have a big question: lets say that the internal folded horn path is 9 feet long (reasonable length). In a small room that would make the woofer be DOUBLE of my listening distance from the main speakers.
If the wavelength at 100Hz is about 11 ft, would not those extra 9 feet throw off the phase response grossly and mess up the sound at the 80Hz crossover point I intend to use???

SEALED subs: I can place stacked sealed subs in corners, lets say 4x15" in each corner. A total of 8x15" would provide enough quality vs output to outclass other types of subs for my application requirements (see above)?

I have only used sealed subs in my current system. And the problem is I cannot imagine how other types will sound compared to the sealed design.

Thank you,
Herman


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Ivan Beaver

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Re: loudness -- types of music
« Reply #22 on: March 24, 2011, 07:35:30 am »

First of all, I'd like to thank everyone for dissecting my problem.

The loudest I would need is 110 to 115db. However, I do NOT like to push the system to it's limits so at those levels I want the subs to be in "relaxed" mode and have some headroom.

If I choose to have two subs (placed in corners behind speakers) then I have 3'x2'x8' available volume for each sub = 48 ft^3 per sub

The music to be played is Classical, Jazz and Techno.

As far as HORN subs I have a big question: lets say that the internal folded horn path is 9 feet long (reasonable length). In a small room that would make the woofer be DOUBLE of my listening distance from the main speakers.
If the wavelength at 100Hz is about 11 ft, would not those extra 9 feet throw off the phase response grossly and mess up the sound at the 80Hz crossover point I intend to use???

SEALED subs: I can place stacked sealed subs in corners, lets say 4x15" in each corner. A total of 8x15" would provide enough quality vs output to outclass other types of subs for my application requirements (see above)?

I
You state SPL levels-that is good-but what do they mean?  Is that A weighted? C Weighted?  No weighting?  Is that slow-fast-peak response?  All of those will give VERY VERY different readings on a SPL meter.

It is not just the length of the horn that you have to consider.  It is also the phase/"delay" response of the crossover filters, that will also affect signal arrivals.  It is not just the physical distance.

ALso you have to consider whether you are talking about electrical or acoustical crossover points.  Very often they are NOT (sometimes not even close) the same.  This is also affect the amount of "delay" in the system.

Putting the usbs in the corners is usually not a good idea-if you are trying to energize the room modes.  As said earlier, they need to be in different places-to excite different room modes.  The corners are easy, but often not the most effective.  But at least 1 sub should be ina corner.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Herman Chigrin

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Re: loudness -- types of music
« Reply #23 on: March 28, 2011, 01:12:25 am »

Hi,

the Spl measurement were taken at "slow" response, "c" weighing. Again, 115 db is not typical levels, but would be on the high side. Some of the options for a pair of subs are:
KV2 EX2.2 Active Bass Module
Danley sound 115

or a self built transmission line or sealed subs based on 12" or 15" woofers.
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Martyn ferrit Rowe

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