Do you think you need a subwoofer?

lewn,

   As you are well aware, the Sound Lab 845Pxs are excellent speakers that are capable of going fairly deep (26 hz).  However,  I believe a distributive bass arrray (DBA) would be a very good solution in your system for several reasons:

1.  The bass produced by a DBA, using 4 10" driver subs, will be seamlessly integrated into the sound coming from your sound Labs; capable of being as quick and detailed as the Sound Labs or deeper and more powerful depending on the source content.  

2.  Using a DBA will relieve your OTL amps and the Sound Labs from reproducing the more demanding lowest frequencies., the supplied separate class A/B amp would be powering the bass (if you go with the Audio Kinesis Swarm or Debra DBA) or the internal class D amps on the mini-subs would be powering the bass (if you go with the Rel q201e subs that enginedr1960 uses).  You could then turn down the bass level to taste on the Sound Labs.  I think the result would be even better performance from the Sound Labs (especially in increased dynamics) since your OTL amp would mainly be powering the mid-range and treble with bass level powering reduced by the amount you determine sounds best.

3.  Using a DBA as described above will significantly reduce the amount of crossover circuitry in your system's signal path.  There would only be crossover circuitry in the bass level that is built into both the Audio Kinesis separate amp or each individual powered sub.  
      You would customize the bass to your preference by a combination of reducing the bass output level on your Sound Labs and adjusting the crossover frequency and volume setting on the Audio Kinesis DBA separate amp or each individual powered mini sub.  A bit cumbersome but it would provide great flexibility in dialing in the bass to your exact preferences.

4  Room aesthetics would be minimally affected. I replied to you in an earlier post about this.  
     Basically, I described how my 2 front subs are hidden behind my 2ft wide panel speakers and the other 2 (each along a side wall near a back wall) are partially hidden by a leather chair and an oversized end table.
      My room is 23ft x 16ft with an 8ft ceiling and I barely notice them.  I think your room may be even larger.  Your panels are also even wider at 3ft so, as long as you determined through the setup process the subs sound best at those positions, they would be completely hidden from view.  That just leaves the rear 2 subs that need to be creatively hidden.


   Just my thoughts but I really believe a DBA would be a great sonic match with your Sound Labs.

Tim
   

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.