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Suggestions for dual sub setup


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10 replies to this topic

#1 of 11 OFFLINE   TomBartley

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Posted January 13 2005 - 02:17 PM

I just have a quick question really about running dual subs. I have both a downward firing sub and a front firing one. They're esentially the same; the front firing sub is was the next model year. Same specs and stuff. Anyways, I have the downward sub under my desk on the north wall, and the front firing one on the west wall, facing inward towards the room. The room is 12x10, by the way. Am I getting the best bass response that I could be, or should I move some stuff around? Thanks for your help, and feel free to ask any questions about my system or room or whatever. Posted Image
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#2 of 11 OFFLINE   SethH

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Posted January 13 2005 - 04:29 PM

The key is to calibrate your system. Have you ever calibrated your system before? If not, you should start with a radio shack SPL meter and a calibration disc like Avia or DVE. Then you can determine any peaks or nulls at the listening area and attempt to fix them at that point.

#3 of 11 OFFLINE   ScottCHI

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Posted January 13 2005 - 04:41 PM

you may do better co-locating them; stacking them, for example.

2 subs in separate locations, although it CAN help tame some rooms, can create problems.

co-locating will give you the most output and reduce interference issues.
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#4 of 11 OFFLINE   Robert Cowan

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Posted January 13 2005 - 05:13 PM

Scott,

i beg to differ (being a dual sub owner and advocate).

by stacking subs you just add gain, thats all. if that location has a problem, you just make it worse.

using dual subs is the greatest way to tame dips and spikes in a rooms response. if one wall has a dip in mid bass, you can correct it with a second sub along the opposite wall in another location that might have a dip in the lower bass region. (this isnt an absolute, im just giving an example of what could happen).

using dual subs simply allows you to blend the bad and the good to get a flatter repsonse, but only when they are in separate locations. THX suggests stacking the subs, but that is only because THX only cares about gain, not flat response.

btw, how you been Scott, havent seen you in awhile...

#5 of 11 OFFLINE   Richard_M

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Posted January 13 2005 - 05:38 PM

Hi Tom,

As per both Seth & Roberts’s replies, Location & Calibration are going to be the main things you need to get right initially.

You should measure your in room response for each sub and also with both going, (Leave your main speakers off for this first test); this will then show you what you are or are not listening too.

To be able to conduct these tests you will need an SPL meter, test tones and be able to use an Excel Spreadsheet. If you don’t have any or all of these, about the only thing you will need to buy is the SPL Meter, and maybe MS Excel, or download a shareware program that will read Excel files. Test tones & a spreadsheet which is also handy for setting up a BFD as well are already available for free download; let us know if you require their links.
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#6 of 11 OFFLINE   SteveAZ

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Posted January 14 2005 - 05:30 AM

A second sub in a different location can help even out the response throughout the room. That is only if you can get them to cooperate together and still get them to cooperate with your mains. Most importantly, do they have phase adjustments? Are they reverse phase switches, or continuously vairable?

#7 of 11 OFFLINE   Wayne A. Pflughaupt

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Posted January 14 2005 - 07:28 AM

Robert, Steve,

Quote:
using dual subs simply allows you to blend the bad and the good to get a flatter repsonse, but only when they are in separate locations.
You really shouldn’t assume that since you had good results with this arrangement that everyone will. For instance, it didn’t work well for me. Neither did it for this poor fellow, who experienced nothing but misery trying to use separated subs.

For instance, here are some graphs he posted:

Left sub
Posted Image


Right sub
Posted Image


Combined response
Posted Image


Now, wouldn’t have made more sense for him to just put both subs at the left location???

Quote:
using dual subs is the greatest way to tame dips and spikes in a rooms response. if one wall has a dip in mid bass, you can correct it with a second sub along the opposite wall in another location that might have a dip in the lower bass region. (this isnt an absolute, im just giving an example of what could happen).
I’ve seen people say this before, but I’ve yet to see anyone post response charts to verify it. Yes, a second sub elsewhere in the room can take up the slack if the first has a dead spot somewhere, but a secondary subs won’t be smoothing out any peaks from the other sub. Then you have the issue of phase (time alignment) issues which can result in comb filtering or other response irregularities. This is a problem you won’t have if the subs are co-located.

Tom,

Bottom line, any advice anyone gives you on using multiple subs is only as good as the room they used it in – which does you absolutely no good unless your room has identical dimensions. The general rule of thumb is that separate placement usually results in worse overall response, but to be perfectly honest you won’t know for sure what’s going on in your room until you take some readings and plot your response. Until then, you’re just guessing.

That said, if you want the absolute best performance, your best bet is to put the sub in a corner and equalize it. Countless HTF Members have had the best results using this approach.

Regards,
Wayne A. Pflughaupt

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#8 of 11 OFFLINE   toddAllen

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Posted January 14 2005 - 11:06 AM

putting them in different areas is only opening the doors for serious PHASE ISSUES. you could (in theory) completely cancel both subs out by putting them in seperate locations. todd.

#9 of 11 OFFLINE   Andrew Pratt

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Posted January 14 2005 - 01:45 PM

There's a great read on the Harman International site about multi subwoofer installs that I highly recomend you reading...actually real all the white papers if you can they're worth it.

#10 of 11 OFFLINE   toddAllen

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Posted January 14 2005 - 02:06 PM

actually, what i would do is buy another blue sky 12" sub, and you can set it up to be the rollof on the rear or front speakers, or use it as the actual LFE channel, but it also has phase switch on it, and a bass management controller. todd.

#11 of 11 OFFLINE   TomBartley

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Posted January 16 2005 - 06:24 AM

Wow thanks for all the replies, I got more responses than anticipated. The way my room is setup really limits where I can put stuff- the bed is along one wall; the desk (with the donward sub underneath) & entertainment center are against the next wall; a bookcase and bureau with the front sub along the 3rd; and behind me is the chair in the corner, the radiator, and DVD rack. Space is somewhat at a premium, since I have my floor speakers standing on my desk and bureau! You're right though, i definitely need to do some kind of calibrating, because I know my system can sound way better. I was smart and bought the best stuff I could afford, and made sure it was all voice matched to boot.
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