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Old 20th July 2011, 02:50 AM   #1
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Default IB sub placement

I have limited space and an intense desire for deep bass in my studio. IB seems like an obvious answer to me, but I'm not really aware of the downside(s) to such a design and what would be optimal placement for SQ(smooth, even bass response).

The room looks like this:
Click the image to open in full size.

I have the ability to run a high quality room correction, but I'd like to minimize nulls as best as possible. I have no limit on the number of subwoofers I can add other than the limit imposed by the size of the room. Right now it is primarily set up as a Live End , Dead End deal and I'd like the optimal response to be at the current listening position.
The live end is nearly covered with diffusion, the exception being the back wall which has a huge/deep broadband absorber.

I made a number of graphs of the current listening position performance on my blog: audio blog: The Dan"TheMan"Cave and you can see the rocky bad response I currently have and the nasty 45(ish) Hz mode that rings like a bell. Can't say I can hear it, but none the less, I want better measured performance if only to retain what little sanity I have left. I'm going to move the mains around to do it here soon.

I have several amplifiers(too many to count) at my disposal suitable for subwoofers driving though not immensely powerful--most around 100 watts. Number is not a limitation except by size on the space.

Thanks for any help n advance,

Dan
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Old 20th July 2011, 07:49 PM   #2
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The only downside of an IB is the lack of efficiency, which should not be a problem in your studio if you are prepared to get enough of whatever you decide on getting.

The 45 Hz peak may be your speaker’s response, it looks like a ported cabinet with an underdamped Fb, as it peaks and falls like a rock.

Try testing your mains outdoors so you can tell what is room and what is “boom”.

As far as placement, I’d suggest placing a pair of subs beneath the main speakers for starters, if it is not smooth in the listening area, move them around.

Although this is DIY, and you have indicated a preference for IB, I’ll still mention I use a Mackie HRS 120 in my control room, placed in a corner it is “flat” (other than the dips and peaks caused by the small room dimensions) to below 20 Hz. The size is only 18 x 19 x 21 inches, but it produces enough LF output to excite wall resonant frequencies as low as 15 Hz. It is a powered sub using a passive radiator.

It is rated at 117 dB maximum SPL at one meter, which it probably can exceed in a corner of a small room.

I purchased it used after listening to several other small studio monitor subs, it was the only one that I heard that had much out put below 30 Hz.
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Old 20th July 2011, 09:31 PM   #3
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I try to stick by the 1/4 dimension rule to keep room nodes/modes from exciting. In your room, with a pair of subs, that would be 3.6ft from front and side walls, 2ft off floor. As a starting point.

reference: http://socalht.com/subs/multsubs.pdf
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Old 20th July 2011, 11:27 PM   #4
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IB temptation ? Give a try then. If this helps, these are my user's comments.

I use one since a few months after living with EQed H Frames for years, and IB has some advantages...the trade off being that you can't move it to try other positions in the room, the thread object.

The efficiency issue can be adressed by using a vertical array. I have four 15", it's the minimum, don't think small in IB. It runs more than 6dB higher than the same drivers in OB (over 100 Hz). Plus maybe radiating in a 2 Pi space. Power handling is better as no bass boost is required, so no worries for level . Only the amp could be a limitation if aiming to rattle the house with a 6Hz tone.

But the problems of bass in a room remain the same, you can have any peak or suck out difficult to EQ, the only solution is to move the listening spot, but with the concerned wavelengths this can be illusory. I use then 2 others 15" in the room, trying random positioning to get rid of a 45 Hz suck out but looks like there's nothing to do.

Anyway, IMHO, IB is a very positive evolution when just considering the hearing (and feeling...) results. It's really an other level of truth for definition and impact of the low end. Imaging is not compromised by a central array, spaciousness is much better.

If you think of monitoring, you will notice on some records (classical as well) some infrasonic artefacts (like a hit or blow on the mike) that the guys have not been aware of, probably because their systems were not going low enough.

Last point, the domestic issues : first, IB is not space consuming, and second, the back wave will not put the neighbours in trouble, that's pretty hard to identificate or localize. Only the rattle could become very annoying, for this my IB is decoupled by rubber pads, I suggest you to do the same. Etancheity of the enclosure ? Bah, I can open a big window close to the IB, I don't measure or ear any difference.

What kind of drivers will you use and where are you planning to make the hole ?
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Old 21st July 2011, 03:43 AM   #5
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the 45Hz is there regardless of speaker. Worse on some others. I've talked myself out of the IB. Too many issues I don't want to deal with. I sub or 2 will have to do.

Thanks,

Dan
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