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Dual sub placement - corners or beside speakers?

Thetiminator

Thetiminator

Painfully virile
Hi guys
I’ve got a pair of DB1’s that are currently sited in the rear corners of the room behind the speakers. They have two drivers so each sub has one pointing across the long rear wall and tother hitting the side wall from about 1ft away.
I’d put them here as the dealer said this was the best place, but I’m wondering if anyone has gone from this position to beside the speakers (on the inside between speakers and rack), pointing toward the listening position? This would mean one driver would be firing toward the listening position and the other rear wards toward the back wall....
I thought I’d ask first as moving them would involve a pile of shuffling and moving of other bits and pieces....
They work well at the mo, but I’m wondering if the sound might blend even better with my mains (big horns with super fast bass) moved out of the corners?
Cheers
 
Purité Audio said:
45Hz is low, did you measure to determine the speakers in-room roll off ?
Keith
Click to expand...

Keith, in situations where DSP is not available, and assuming the main speakers can extend adequately, would you agree that crossing over to the subs as low as possible and with a steep a slope as possible makes sub positioning less critical in terms of time alignment? This seems to be my experience at least.

I don't high-pass my main speakers and simply set the subs' crossover points low enough so that they don't overlap too much with my main speakers' respective roll-offs, thus avoiding a peak in the amplitude response (I actually set the crossover point so that there is a slight dip in the response). With my Tannoy Edinburghs I set my dual XXLS400 subs to cross at around 30Hz at 24dB/oct, with my Celestion Ditton 66 I set the subs crossover a little higher because the Celestions' roll-off a little earlier and steeper than the Tannoys.

My subs are located on the same horizontal axis as my Tannoys, so are as close as possible to being aligned from a physical/visual perspective. When I listen to my Celestions however, they sit a good 30cm to 40cm in front of the subs and are therefore less time-aligned (again from a physical/visual perspective).

Perhaps it's because I haven't been trained to hear the effects of poor time alignment, but to my ears my subs integrate just as effectively with the Celestions as they do with the Tannoys despite the difference in physical distance.
 
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TT I just think that a small processor is so effective and so inexpensive you should integrate properly .
Once you can control everything you can experiment for best results.
Keith
 
To set up I used a test disc with LF tones to match level with speaker roll off. But then mainly by ear, I found anything above 44/45hz and you could hear the effect of the sub on the bass of the main speakers. The speakers roll off sharply around 45hz but above this the bass is huge and any further help just bloats it a touch and also degrades the tone, punch, detail etc...also above 45hz you can really hear it degrade the mid range too.
The speakers don’t need any help with their output at all, I just need the subs to fill in below where the speakers tail off....
 
To properly integrate you need to acoustically measure with REW, see where the mains roll off and then use something like a MiniDSP processor to set slope, order frequency, gain and delays if necessary.
There is a good ‘how to’ on their site.
Keith
 
Thanks I’ll have a look at that down the line.

For now though does anyone have any experience of using a sub/s in corners and then moving to between speakers? Thanks guys...
 
Wilson benesch recommend subs between the speakers. That’s what I did when I had them (2off) and they worked very well. Integration is easier when close to the main speakers.
 
Things to try :

Subs facing each other, both in and out of phase.

Subs as far apart as possible.

Assuming you are not using DSP (supposedly optimal), adjust roll off point until you can only just hear the subs’ contribution, then turn down a tad more.

I gathered the above info whilst intending to add a pair of JBL subs to my vintage Sonabs, but tried something else (placing a second pair of Sonabs right in the corners of the room), which I liked so much that I now have two JBL coffee tables !
 
Purité Audio said:
To properly integrate you need to acoustically measure with REW, see where the mains roll off and then use something like a MiniDSP processor to set slope, order frequency, gain and delays if necessary.
There is a good ‘how to’ on their site.
Keith
Click to expand...

Keith, DSP appears to be your default response regardless of a user's setup specifics. I see you have dodged my attempt to start a discussion with you on the importance/unimportance of perfect time alignment between subs and mains when the crossover frequency is low and steep. A DSP box may indeed be the most optimal and easiest route to integration, but are you willing to at least acknowledge that it's possible to get satisfactory results without it?!
 
Well I’m sort of asking generally at the mo. My guess would be that in the corners the sub drives the room better but may be perhaps slower and less tuneful....and between the soeakers it may be tighter and more tuneful but may need the volume cranked up a bit?
 
Thetiminator said:
Well I’m sort of asking generally at the mo. My guess would be that in the corners the sub drives the room better but may be perhaps slower and less tuneful....and between the soeakers it may be tighter and more tuneful but may need the volume cranked up a bit?
Click to expand...

I could be wrong but I think this largely depends on the frequencies of your axial room modes is and the frequency your crossing over at. Below the room's lowest axial mode (dictated by the room's longest dimension), a bass driver becomes a pressure-based source and the in-room amplitude frequency response flattens out. Placement is therefore less critical in terms of achieving a flat amplitude response. However as you have quite rightly noted you also have to consider speed / reverberation times, which often worsen as the speaker's position is moved closer to a corner. How much of an impact this has on frequencies below your lowest axial mode I'm not sure, hopefully someone with more knowledge on this will chime in.
 
ToTo Man said:
Keith, DSP appears to be your default response regardless of a user's setup specifics. I see you have dodged my attempt to start a discussion with you on the importance/unimportance of perfect time alignment between subs and mains when the crossover frequency is low and steep. A DSP box may indeed be the most optimal and easiest route to integration, but are you willing to at least acknowledge that it's possible to get satisfactory results without it?!
Click to expand...

Do it by ear I'm sure you'll be fine, I had a sub with ATC 25s and ATC recommend not high passing the mains. I found it very helpful to have a friend adjusting the controls on the sub while I sat in the listening spot! This is a helpful guide from Genelec, it's more aimed at studios but the Sub placement is relevant:
https://www.genelec.com/sites/defau...logues/monitor_setup_guide_2018_bbage125e.pdf
 
As a general point multiple subs are required to get even response. Modes are cancelled. Two get you most of the way there (must be opposite ends of room) and 4 is an additional improvement. It also makes the response far more consistent as you move around the room. A bit of judicious dsp EQ will perfect things.

I would recommend proper crossover filtering 60 to 80hz. Let the subs do the work and benefit from the mode cancellation which you won't benefit from otherwise.

Ill post some measurements later of 1 to 4 subs placed in room corners. The improvement isn't subtle.
 
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1 sub no dsp no mains (small B&W asw608)

1%20sub%20w_zpsjuuwtdrg.png


2 sub in line
2%20subs%20IL_zpskwh1i11w.png


2 subs diagonal

2%20subs%20diag_zpshcykdrvj.png


3 subs

3%20subs_zpspahoegys.png


4 subs

4%20subs_zpsscnzvxov.png


4 subs with dsp and xo
4%20subs%20WF%20with%20dsp_zpskskv1nuc.png
 
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