Double stack ML subs?

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sleepysurf

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I don't recall seeing this topic discussed here, though I've read about it elsewhere (e.g. Reference Line Arrays - REL Acoustics).

For the past few years I've struggled to optimally integrate a pair of BF 210's (running as dual mono) with my Expression 13A's. Frankly, the 13A's, by themselves. produce tighter bass than with the BF 210's added. However, they are not sufficient to fully energize my large open floor plan family/listening room, nor (due to room geometry) fill in the deep ~55 Hz null at my main listening position. The two BF 210's (located behind our sofa) solve those issues, albeit slightly muddying up the lowest octave. I just got an Anthem MRX 740 receiver (replacing an older Denon), hoping it's ability to run ARC Genesis simultaneously for everything would optimize the timing of the 13A's and subs.

However, my wife now wants a new reclining sofa, so the subs would have to go elsewhere. I vaguely remember doing the "sub crawl" a few years ago, and at time a single sub in the front left room corner worked OK to help tame the null, while adding more bass impact. However, that's where my equipment rack had to go, so I never went that route.

As it turns out, the new Anthem receiver sounds surprisingly good as a pre-amp, and could possibly replace my C-J pre and Bel Canto DAC, thus eliminating the need for the corner rack. I could then double stack the BF 210's in that corner (daisy chained), and use ARC Genesis to optimally dial-in their timing with the 13A's. The higher position of the top sub might even help fill in the mid bass null (only way to know is to try).

Has anybody tried stacking ML subs? I'd place a heavy rubber pad between them, and use the top sub as the "Master" (in order to access the controls).
 

ttocs

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The short answer is yes.
The other short answer is I tie each Expression to a pair of stacked subs via speaker level connection, the processor is not involved in this part of it. It's all by using the adjustments of the Expression and each 1100X sub.

I'm not using BF subs so it's not exactly an apples comparison, but, I stacked pairs of 1100X's with a rubber tool drawer liner pad inbetween. So it's four subs in front and one 800X in the back of the room to smooth my null between 60-70Hz. Each pair in front is connected to each Expression via speaker level connections, the Bass Control on each Expression is reduced to -10dB. The bottom 1100X is dialed in first, then the top 1100X is added while the Expression and bottom 1100X are playing. This is done for both fronts, then the rear 800X is added while both Expressions and both pairs of 1100X's are playing to fill the null. Afterwards, each Front Group - 1 Expression and its pair of subs - are checked with the rear sub to verify that all is well. A tweak here and there and we got us a convoy.

Two miniDSP 2x4HD's control the subs for HT usage, but only one of them passes L&R to the rear sub for two channel usage. miniDSP1 provides BM and LFE to the rear sub via wireless. miniDSP2 provides separate Left and Right channel signals to the rear sub via separate wireless transmission.

Currently, the two bottom subs in front and the rear sub also provide Bass Management and LFE but from separate channels from the processor, and as such are independently adjustable for proper levels.

The Fronts are setup as Large. The Center is also setup as Large and runs through an active XO and to a dedicated subwoofer just for the Motif Center Speaker. All other speaker channels are setup as Small.

I initiated moving to this setup for two channel music. HT is secondary. Both perform great!

This is what the fronts look like. Each Front/sub-pair "acting as one unit" is only strictly as Left and Right channels. The subs provide triple duty when the system is in HT mode.
210705-Speaker-Subwoofer-Elevation.jpeg
 
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sleepysurf

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ttocs... That's quite a sophisticated setup you cobbled together! I'm sure it sounds incredible! To start, I'll have a listen and run some measurements with ONE BF210 in the corner. However, due to the sub controls being on top, I can't "tweak" it once the other is stacked (hence will need to run as dual mono "master and slave").

msimanyi... Yes, I use PBK/ARC, and have also experimented with the downloaded custom filters for the Expressions. Until getting the MRX 740, I couldn't run ARC Genesis simultaneously for everything, but now can do so. There's rumor that Anthem Genesis will eventually get automated distance and phase control, which currently must be adjusted manually.
 

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@sleepysurf, not to derail the thread, but did you get your MRX740 before the backorder situation or after? I’m just trying to guesstimate when I might get my MRX1140 (my 520 can’t do Atmos, but otherwise is quite nice).
 

sleepysurf

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I ordered (from Shawn/Davinci) back in Feb, and just got it! Not sure how backordered they currently are. If Anthem ran out of the original AKM DAC chips, it could take some time for them to re-engineer for whatever they substitute with.
 

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I ordered (from Shawn/Davinci) back in Feb, and just got it! Not sure how backordered they currently are. If Anthem ran out of the original AKM DAC chips, it could take some time for them to re-engineer for whatever they substitute with.
I ordered from Shawn, but just recently. Are you sure that you received the “old” AKM DAC?
 

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DaVinci Media

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I don't recall seeing this topic discussed here, though I've read about it elsewhere (e.g. Reference Line Arrays - REL Acoustics).

For the past few years I've struggled to optimally integrate a pair of BF 210's (running as dual mono) with my Expression 13A's. Frankly, the 13A's, by themselves. produce tighter bass than with the BF 210's added. However, they are not sufficient to fully energize my large open floor plan family/listening room, nor (due to room geometry) fill in the deep ~55 Hz null at my main listening position. The two BF 210's (located behind our sofa) solve those issues, albeit slightly muddying up the lowest octave. I just got an Anthem MRX 740 receiver (replacing an older Denon), hoping it's ability to run ARC Genesis simultaneously for everything would optimize the timing of the 13A's and subs.

However, my wife now wants a new reclining sofa, so the subs would have to go elsewhere. I vaguely remember doing the "sub crawl" a few years ago, and at time a single sub in the front left room corner worked OK to help tame the null, while adding more bass impact. However, that's where my equipment rack had to go, so I never went that route.

As it turns out, the new Anthem receiver sounds surprisingly good as a pre-amp, and could possibly replace my C-J pre and Bel Canto DAC, thus eliminating the need for the corner rack. I could then double stack the BF 210's in that corner (daisy chained), and use ARC Genesis to optimally dial-in their timing with the 13A's. The higher position of the top sub might even help fill in the mid bass null (only way to know is to try).

Has anybody tried stacking ML subs? I'd place a heavy rubber pad between them, and use the top sub as the "Master" (in order to access the controls).
Have you ever run the PBK software with the 210s? I’d be interested to see the response curve for your room. That’s always a good tool to observe as you play with placement as well. Also, if you try to stack it I would love to see what that does to in room response. Next time I install two subs at a time I’m definitely going to try that and see!
 

sleepysurf

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Have you ever run the PBK software with the 210s? I’d be interested to see the response curve for your room. That’s always a good tool to observe as you play with placement as well. Also, if you try to stack it I would love to see what that does to in room response. Next time I install two subs at a time I’m definitely going to try that and see!
Shawn (and others), here are two ARC Genesis summary PDF's. One is from 7-28 (run using the mic from the original PBK kit), and one from today, using the newer ARC kit and USB-C mic that came with the MRX. Despite both measurements using the current ARC Genesis version (on Win 10 laptop), the reported crossover and high-pass frequencies, slope, and minimum correction frequency are all different! Not sure what to make of that!
Regardless, the bass nulls are clearly evident in both.

I'll run the same measurements later today, with the Expressions by themselves, then everything together via the MRX 740.
 

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sleepysurf

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Before proceeding, I decided to measure ONE sub in the front left corner. Fortunately, my memory was correct! It does yield a smoother bass response and less null around the main listening position! That being the case, I'll proceed with stacking the subs, but won't be able to do that for another week or so, as we have family coming to stay with us this week. Interestingly, as before, the reported crossover, slope, etc. are different yet again.
 

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sleepysurf

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Got some help stacking the subs (with 1/4" rubber padding in between). Bass (at main listening position) is already much improved after manually entering speaker distances in the MRX. Will run ARC Genesis again next week. BTW, that's a "Gramovox Floating Record" turntable on top of the sub stack, which is more of a "conversation piece," but sounds surprisingly good (for the handful of LP's I own). I also have a 16" ASC Tube Trap in the corner.

StackedDualMonoBF210s.jpg
 

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Okay, I have to ask: have you previously used the turntable while it was located on top of a subwoofer cabinet?

I don't have my BF210s yet, but despite the claims that the mirrored drivers cancel cabinet resonance, I'd be shocked it they truly eliminate *all* resonance.
 

sleepysurf

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Actually, no cabinet resonance whatsoever, even with the deepest bass, and the turntable has vibration dampening feet. However, I rarely spin vinyl, so it's more of a conversation/art piece.
 

Robert D

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Okay, I have to ask: have you previously used the turntable while it was located on top of a subwoofer cabinet?

I don't have my BF210s yet, but despite the claims that the mirrored drivers cancel cabinet resonance, I'd be shocked it they truly eliminate *all* resonance.
Ive got one on order too. RIght now I have been using a Depth i I bought new and it has never had any cabinet noise. It has 3 woofers on it positioned geometrically so that vibrations are minimized. I believe that the newer subs will be the same way.
 

DaVinci Media

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Shawn (and others), here are two ARC Genesis summary PDF's. One is from 7-28 (run using the mic from the original PBK kit), and one from today, using the newer ARC kit and USB-C mic that came with the MRX. Despite both measurements using the current ARC Genesis version (on Win 10 laptop), the reported crossover and high-pass frequencies, slope, and minimum correction frequency are all different! Not sure what to make of that!
Regardless, the bass nulls are clearly evident in both.

I'll run the same measurements later today, with the Expressions by themselves, then everything together via the MRX 740.
I have experienced what you were talking about with the measurements being different between the PBK software and the genesis software. One thing I always do is the Martin Logan PBK for the sub and any others Masterpiece speaker that has it available before ARC in the anthem, Or any other room correction software for that matter. First of all I think the PBK mic is a little bit more accurate. The genesis mic isn’t bad but with the PBK is better. The fact that you have to download a specific file for the microphone in the PBK kit shows you that it’s a more individual precise measurement. Anomalies in a microphone could easily cause variations in measurements. The other thing that you need to be really careful with when using Genesis with Logan’s is you really should not be running it above the crossover point between the low end in the panel. Because the panels are dipolar room correction from all of the mass produced room corrections systems cause more issues than they correct. It’s always been something that I wanted to look into more but I’ve never really had the chance. But if you talk to any of the engineers at Martin Logan or Anthem they will tell you the same thing. I do wonder if with some of the more advanced systems you can make accommodations for the dipolar nature of the panel. Anybody have any thoughts or information on that?
 

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...First of all I think the PBK mic is a little bit more accurate. The genesis mic isn’t bad but with the PBK is better. The fact that you have to download a specific file for the microphone in the PBK kit shows you that it’s a more individual precise measurement. Anomalies in a microphone could easily cause variations in measurements. The other thing that you need to be really careful with when using Genesis with Logan’s is you really should not be running it above the crossover point between the low end in the panel. Because the panels are dipolar room correction from all of the mass produced room corrections systems cause more issues than they correct. It’s always been something that I wanted to look into more but I’ve never really had the chance. But if you talk to any of the engineers at Martin Logan or Anthem they will tell you the same thing. I do wonder if with some of the more advanced systems you can make accommodations for the dipolar nature of the panel. Anybody have any thoughts or information on that?
The new ARC Genesis mic has the calibration curve built in. It looks and feels MUCH more robust (heavy aluminum) vs. the old plastic mic, and I suspect the additional front "mic pinhole" adds additional accuracy. I'm tied up for a few days, but will conduct an experiment next week, running ARC Genesis with both mics, and comparing measurements. Ultimately, I plan on using ARC Genesis "Pro" mode to limit corrections to bass response below the Schroeder frequency.

I'm impressed thus far with the MRX 740. My only concern is that everything is run through the internal DAC chip, with no option to "pass through" the pure analog from my higher end (Bel Canto) DAC. However, I'm hoping the advantage of being able to "time align" subs and mains outweighs that issue.
 

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I have experienced what you were talking about with the measurements being different between the PBK software and the genesis software. One thing I always do is the Martin Logan PBK for the sub and any others Masterpiece speaker that has it available before ARC in the anthem, Or any other room correction software for that matter. First of all I think the PBK mic is a little bit more accurate. The genesis mic isn’t bad but with the PBK is better. The fact that you have to download a specific file for the microphone in the PBK kit shows you that it’s a more individual precise measurement. Anomalies in a microphone could easily cause variations in measurements. The other thing that you need to be really careful with when using Genesis with Logan’s is you really should not be running it above the crossover point between the low end in the panel. Because the panels are dipolar room correction from all of the mass produced room corrections systems cause more issues than they correct. It’s always been something that I wanted to look into more but I’ve never really had the chance. But if you talk to any of the engineers at Martin Logan or Anthem they will tell you the same thing. I do wonder if with some of the more advanced systems you can make accommodations for the dipolar nature of the panel. Anybody have any thoughts or information on that?
I totally concur with keeping the corrections to under the XO of the ML speaker so the panel is left alone. My processor uses Dirac, and I've experimented with various frequency upper limits and while the results can be very good and non-problematic with regard to reflections from the rear wave, I find that just above or below the speaker's XO has the best result.

I run ARC first, then Dirac on top of that. I'm results driven, so whether the mic is plastic or metal is immaterial to me, nor is it possible to use another mic with PBK. The PBK system improves the response.

These attachments from last night are for only the 13A woofers, no subs were active. ARC is always optimistic, REW shows otherwise, but ARC provides a great starting point that Dirac can improve upon. I'll run Dirac over the weekend.
210818-05-ARC-13A-a.jpg


210818-05-ARC-13A-b.jpg


210818-05-L13A-beforeafter.jpg
 

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I don't recall seeing this topic discussed here, though I've read about it elsewhere (e.g. Reference Line Arrays - REL Acoustics).

For the past few years I've struggled to optimally integrate a pair of BF 210's (running as dual mono) with my Expression 13A's. Frankly, the 13A's, by themselves. produce tighter bass than with the BF 210's added. However, they are not sufficient to fully energize my large open floor plan family/listening room, nor (due to room geometry) fill in the deep ~55 Hz null at my main listening position. The two BF 210's (located behind our sofa) solve those issues, albeit slightly muddying up the lowest octave. I just got an Anthem MRX 740 receiver (replacing an older Denon), hoping it's ability to run ARC Genesis simultaneously for everything would optimize the timing of the 13A's and subs.

However, my wife now wants a new reclining sofa, so the subs would have to go elsewhere. I vaguely remember doing the "sub crawl" a few years ago, and at time a single sub in the front left room corner worked OK to help tame the null, while adding more bass impact. However, that's where my equipment rack had to go, so I never went that route.

As it turns out, the new Anthem receiver sounds surprisingly good as a pre-amp, and could possibly replace my C-J pre and Bel Canto DAC, thus eliminating the need for the corner rack. I could then double stack the BF 210's in that corner (daisy chained), and use ARC Genesis to optimally dial-in their timing with the 13A's. The higher position of the top sub might even help fill in the mid bass null (only way to know is to try).

Has anybody tried stacking ML subs? I'd place a heavy rubber pad between them, and use the top sub as the "Master" (in order to access the controls).
 
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