# Setting BFD With 4 Subs



## hjones4841 (Jan 21, 2009)

I have on order the Hsu Quad Drive (4 ULS15s) and need ideas on what order to EQ them. I may end up with 2x2 co-located, but suppose I put them around the room. What order to I EQ them?

Right now I have one BFD, but I can get another one if needed to give independent EQ for each. I have REW with ECM-8000 and the Behringer mixer.

So, do I EQ them individually, then check all 4 together and see what I have? How do I know which one(s) to re-EQ if problems show up with all 4 running? Or is it trial-and-error multiple times?

By the way, room is 2050 cu ft (12.5 x 20.5 x 8). LCR is on one 12.5' wall, L/R rear on other 12.5' wall and side surrounds about midway down the 20.5' wall. I know that the Quad Drive is overkill for this room, but I have lived with limited sub headroom for 11 years with my one Velodyne FSR-18 and wanted to make sure I did enough this time.

Sorry if this has been covered before. Most posts that I have seen are for two, not four.

Thanks.


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## Wayne A. Pflughaupt (Apr 13, 2006)

If you're co-locating them all, then it's easy: EQ the group as one with a single EQ channel. 

If you're putting a pair in one location and a pair in another, then that's a little trickier. If you have a symmetrical shoe-box-type room and are using symmetrical placement (e.g., one pair on one front corner, the other pair in the other front corner) response should be the same for either location, so once again you can EQ them all with the same set of filters from a single EQ channel. If you're going for asymmetrical placement in a symmetrical room, you'll probably want to EQ each pair separately (two EQ channels). 

For a non-symmetrical room, again with a pair in two locations, with either symmetrical or asymmetrical placement, response will most likely be different at each location, so you'll probably need to EQ each pair separately (two EQ Channels).

If you're locating all four in four different locations, that can be a nightmare, depending on the room. It might be best (read easiest) in that case to just EQ them as a whole (i.e., one EQ channel).

Regards,
Wayne


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## hjones4841 (Jan 21, 2009)

Thanks, Wayne. I likely will co-locate each pair at first, likely symetrically on the front wall.

I first thought about stacking them vertically, one pair on either side of the center channel. I have the room to do that under the screen, but don't have the room to co-locate side by side without moving them to the side wall. Pete Hsu does not recommend stacking vertically due to possible undesirable floor effects. What has been your experience?

I have a LOT of trapping, some on the front wall, but most on the back and above the suspended ceiling. Not sure if that would negate floor interaction, tho.


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## Wayne A. Pflughaupt (Apr 13, 2006)

hjones4841 said:


> Pete Hsu does not recommend stacking vertically due to possible undesirable floor effects. What has been your experience?


I had mine stacked in a corner for a long time, in two different living rooms. Worked fine in both.



> I have a LOT of trapping, some on the front wall, but most on the back and above the suspended ceiling. Not sure if that would negate floor interaction, tho.


Not sure I get what that's all about, trying to avoid "undesirable floor effects" and such. Subs react with every boundary. How can that be avoided? :huh: 

Regards,
Wayne


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## Sonnie (Apr 11, 2006)

I have two plus two by two... two in front and two by two in back. I equalize them all together. Trying to eq them separately will never work. Think about it... when you eq them separately, then put them together, nothing is the same... you have one eq'd location canceling or enforcing the other location. The only way to eq multiple subs and not pull your hair out is going to be eq'ing them all together... been there and done that a bunch of times. Eq'ing them all at once is very easy and works well, no matter the location of them. Remember... you are eq'ing the overall response of the subs while seated at a particular location. :T


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## hjones4841 (Jan 21, 2009)

That is what I decided to do, Sonnie. I plan to stack a pair on either side of the center channel and drive them with one channel of the BFD. I plan to move the old Velodyne FSR-18 to the rear of the room and move it around to help compensate for modes. I will use the other BFD channel for it.

Anyone remember how much the BFD rolls off by at 10Hz or so?


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## hjones4841 (Jan 21, 2009)

Wayne A. Pflughaupt said:


> Not sure I get what that's all about, trying to avoid "undesirable floor effects" and such. Subs react with every boundary. How can that be avoided? :huh:
> 
> Regards,
> Wayne


That surprised me also. Anyway, I am going to stack them vertically on either side of center and give that a try.


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## brucek (Apr 11, 2006)

> Anyone remember how much the BFD rolls off by at 10Hz or so?


About a half dB............ basically nothing.









brucek


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## hjones4841 (Jan 21, 2009)

Thanks. For some reason I had remembered that it had an intentional rolloff below 20.


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## hjones4841 (Jan 21, 2009)

Sonnie said:


> I have two plus two by two... two in front and two by two in back.


Sonnie: How did you set the sub distance ? I am going to try one in each corner, but the listening positions are a couple of feet back from center. The room is symmetrical and so will be the placement. Thanks.


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## hjones4841 (Jan 21, 2009)

This site recommends using the average distance:

http://www.audioholics.com/tweaks/get-good-bass/subwoofer-connection-guide


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