Do you think you need a subwoofer?

enginedr1960,

If someone is not buying a complete DBA (distributed bass array) such as the Audio Kinesis Debra or Swarm systems, I think the Rel q201e mini subs might be the ideal sub to use in a custom 4 sub DBA as you assembled. These subs are similar to the Debra and Swarm subs; compact and they utilize 10" drivers. Great choice.

I just have a few suggestions for you and your custom DBA:

1. The DSPeaker Antimode 2.0 and Mini DSP 2 x 4 may have been good tools when utilizing 2 subs but I really don’t believe they’re necessary in a 4 sub DBA. You may want to use the Antimode to verify after the first 2 subs are positioned optimally by ear but I doubt any signal processing will offer any sonic improvements. I don’t think the 2 x 4 will be needed either. I’m certain there is no need for microphones, analyzing or correcting software, equalizers or room treatments when the proper progressive setup procedure is followed.

2. The proper progressive setup procedure is the following:

Sub#1 is hooked up and placed on its back (driver facing the ceiling) at the normal listening position. Music is played that has good and repetitive bass.

Walk around the edges of the room and determine exactly where the bass sounds best to you.

Attach the 3 spiked footers to Sub#1 and position it upright facing the nearest wall to the spot you determined the bass sounded best.

Sub#2 is hooked up and placed on its back at the primary listening position. With sub 1 & 2 playing, continue walking around the edges of your room and determine again where the bass sounds best to you.

Attach the 3 spiked footers to Sub#2 and position it upright facing the nearest wall to the spot you determined the bass sounded best.

Repeat this procedure for sub 3 & 4.

Small positioning adjustments may need to be made for each sub due to avoiding furniture and the WAF.

Once completed, final sub hook up is done in parallel (which you can ignore since you’re using self powered Rel subs):

Attach a single wire from the amp’s speaker A’s pos. output terminal and to Sub#1’s pos. input terminal.

Attach a single wire from the amp’s speaker A’s neg. output terminal and to Sub#2’s neg. input terminal.

Attach a single wire from Sub#1’s neg. input terminal to Sub#2’s pos. input terminal.

Attach Sub 3 & 4 using this parallel method on the amp’s speaker B’s output terminals.

3. Your Rel q201e subs are front firing and I assume you have them pointed out into the room. You may want to try the Debra and Swarm method of pointing each driver directly at the wall no more than an inch away from the wall. I’m not sure this will improve your system’s bass performance but thought you should be aware of how it’s done with the Debra and Swarm systems and determine for yourself which positioning sounds best to you.

4. As you’re probably already aware, selecting the proper cutoff frequency is very important. My main speakers are Magnepans that only have good and accurate bass response down to just below 40 hz. I run my main spkrs full range and use a 40 hz cutoff frequency For 2 ch music and usually 40-60 hz for HT. My center channel and rear surrounds don’t go much deeper than about 8o hz. so this creates a frequency response hole from 40-60 hz up to about 80 hz bass for HT. When I’ve set the cutoff freq. to 80 hz for HT, however, the bass sounds too boomy to me so I prefer to set it at 40-50 hz and the bass response sounds much better to me even though I know there’s a lack of bass response in the 40/50 to 80 hz range; I find I really don’t miss these frequencies.

Your Ohm Walsh 2.2000 monitors go a bit deeper to about 32 hz. so you may need to find the cutoff freq. that sounds best to you. You may also want to try filtering out frequencies below a certain hz(and correspondingly raising the cutoff freq. the subs operate at) to see if your monitors sound even better when their bass duties are reduced.

5. The last suggestion I have (is that applause I hear?) is to sequentially reverse the polarity on 1 of your subs at a time while listening to the same content with good repetitive bass. The idea is that bass response will sound its best with one of the 4 subs running in reverse polarity. The theory is that system bass will sound noticeably better with one specific sub running in reversed polarity. The tricky part is determining which of the 4 subs this is. I cannot verify this improves performance since I was too lazy, and my system bass sounded so good as is, I’ve still not gone through this process.

Hope this info and advice helped,
Tim

Hi enginedr1960,

      I understand the frustrations and compromises involved with the infamous and insideous WAF.
       I followed the  elaborate progressive sub setup procedure  rather strictly.  I took my time determining  exactly where the bass sounded best and clearly noticed the bass sounded the most natural to me located at least a about a foot or more away from room corners; the corner positions definitely reinforced  the bass response, causing bass peaks and were sub position sites I knew should be avoided.
      My goal was to find the precise locations in my room where the bass just sounded natural and right and I avoided all locations where the bass was over or under emphasized.  I think this is the reason that none of my 4 subs are located at one of my room's 4 corners.

    However, I understand your significant other may prefer the subs be tucked way in the corners of your room, the exact locations that are most likely to result in the presence of bass peaks at certain spots in your room where bass response is obviously exaggerated. 

    Just a word of warning, none of the subs should be placed squarely in a corner unless you determine that is where it sounds best, which is unlikely.  If you must place a sub near a corner,  it's best to position it at least a few inches away from the corner's center along one wall or the other.

   It seems like you've become too accustomed to using your DSPeak and 2 x 4 to even consider not using them.   I still believe there's no need for these tools, or even your Bent Audio volume control,  in a properly setup DBA system.  However, I may not completely understand why you consider these products so indispensable.

Thanks,
 Tim

Tim (Noble100)
We are on the same page.  However, I would be doing it for the gain in bass definition and overall frequency balance, more than to relieve my primary amplifiers of any stress.  The 845PX's normally use a 6db/octave passive crossover in front of two different audio step-up transformers that receive, respectively, bass and treble frequencies after the x-over.  This configuration, however, creates a nasty impedance dip at mid-frequencies, in addition to sucking energy across the resistor used in the hi-pass filter.  2-3 years ago, I replaced the treble transformer with a very high quality full range transformer, which enable me to ditch the RC network that creates the hi-pass; I still use an inductor in front of the original SL bass transformer, albeit I replaced the OEM inductor with an 12-ga air core type.  This mod hugely improved the efficiency of the speaker; I daresay it could be driven by less than 50W to very loud sound pressures.  My OTLs can do about 100W, and they are loafing at all times. It also dramatically improved dynamics.  I measured impedance v frequency across the audio range, after the mod, and I see 20 ohms or greater from about 100 Hz to 5kHz. Below 100 Hz, impedance is rising.  Above 5kHz, it falls to about 6-8 ohms at 10 Khz. This is an ideal match for an OTL.

I did mention that someone here had pointed out that two of the 4 woofers could go behind the panels.  Sorry for not remembering to credit you with that insight.  I've known Duke for a long time; I bought my 845s from him.  I will give him a call soon. On his website today, I do see the Swarm, but I don't see the Debra system.  I'll look again.

Hi lewm,

     I already knew the 845s are one of the most efficient Sound Labs ever made (about 89 db).  It sounds like your mods made them even more efficient and a good match with your OTL tube amp.

     I was just listing all the benefits I thought going to a DBA would have in your situation.  I now understand you don't really need to decrease the demand on your OTL.  You're more interested in a DBA to get a more full-range frequency balance and increase bass definition.

     I can confirm that a Debra or Swarm DBA will give your system high quality bass that is capable of blending seamlessly with your Sound Labs while it's also able to reproduce deep,powerful and impactful bass when the content calls for it.

     Just to clarify, Duke sells the Audio Kinesis Swarm and James Romeyn Audio LLC.  in Utah sells the Debra system. Here's a link to the Debra system:
http://jamesromeyn.com/old-pages/home-audio-gear/dsa-1-0-distributed-subwoofer-array-5-pieces-4k-usd...


 They're both basically the same 4 sub DBA, with small differences mainly in the subs' construction.  James licenses the rights to sell it from his friend Duke.   They both come with the same 1,000 watt class A/B sub amp, are both rated accurate down to 20 hertz, about the same system price and share the exact same setup procedure.  Either system will deliver excellent bass response that is very evenly dispersed due to the significant reduction in bass standing waves in your room.

     I didn,t know you bought your Sound Labs from Duke.  He'll be able to give you good advice on how well the Swarm would integrate with your 845s.

  Good idea to give him a call,

                Tim