What process did you use to integrate multiple subwoofers for 2 channel listening?

No worries!
Great to hear of your progress!
You are in for a delight!
Enjoy!

@hleeid Thanks for your post. I tried some elevation but didn't help. Turned out that a different bit of advice from Duke was key -- partly plugging the ports on my stand mount speakers.

I'm happy to report that I now have no more than +/- 6 db peaks or nulls on my system and much less than that in the bass regions, most of the time. The combination of 3 sub placements, room treatments, and port plugging has dialed the room in to what I think are the best limits for this space. 6.5' ceilings made this a major project, but I have learned a lot. The bass is very accurate and full now.

@hilde45 -

Duke LeJeune (AudioKinesis) wrote:
So imo you are definitely playing the distrubuted multisub game already! If you can elevate one of the subs so that it is closer to the ceiling than to the floor, you get bonus points. This is one of the things that @hleeid did to get good results in his 11 x 13 foot room; I think he actually elevated three of the four Swarm subs, as that was more practical than the other way around in his room.

So yes.  That is true.  The room was actually a bit smaller due to closets. 
Had a conversation with Duke about this. 

Even Duke had reservations about the extremely small room.  But I mentioned to him a thread he posted about elevating one or more subs above the room mid height which would contribute to dispersion in the vertical plane.

The light bulb went off in my head.  After some measurements, I figured a way to make 4 subwoofer easily fit by elevating three of them.
One was mounted on the wall behind me above my head.
The one sub on the floor also served as a lamp table next to my desk.

NOTE:  The only limited floor space sacrificed was for the ''lamp table'' sub.

NOTE 2: I must respectfully disagree with Duke about my good results.
They were not really good.

Shockingly incredible would better describe the experience!  Even before hooking up the 4th sub, let alone elevating some of them.

In my new place, I have my mains (Harbeth SHL5+ 40s) firing diagonally across my 13' x 16' (9' ceiling) office.
Two subs are ceiling facing.  One at 12'' and the other 18'' from the ceiling.
Each of these are near the corners along the long wall.
One sub on the floor is slightly behind and to the right of the right speaker.
The other floor sub is to forward and to the right of my desk (my listening position).

After much experimentation with speaker/listener position, light acoustic treatment, etc. I feel this is my best (currently) sounding setup all around.
No DSP, EQ, etc.  except for reversing phase on the sub closest to the mains and unporting the sub furthest from the listening position.

Best of luck to you on your quest!

Thanks, Steve. That sounds like a great result!

Hilde45 - lots of great information here and ways to do this. I have four large subwoofers and measured the room (speakers and listening position) with Room EQ Wizard and then input that data into Multi Sub Optimizer via an Earthworks M30 microphone to generate filters everything running out of my Mini DSP with balanced connections which is processing all filters at 56bit/ 96kHz. The results are stunning and perfect integration. 
Thanks,
Steve

kellyp - I'm not disputing, but HOW do you know it's FLAT to 4Hz.? Could you please briefly explain? So if my calculations are correct; one full 4Hz. wave is 286.96 feet, 1/4 wavelength is 71.74 feet, correct?

WOW, is all that I can say!

FLAT to 4 HZ, that is one Hell of a system, that obviously an be FELT & HEARD!

Just, what Maximum  DB level do you measure with your system?



  

All the speakers have their own power amps, so it is quad amped with an electronic crossover.  that makes it easy.  My subs go for like 70 to 30 Hz, using the Klipschorns.  Then there are the sub-subs, each having 4x15" in a tuned quarter wave huge tube and a 1KW plate amp.  Three of those on separate power.  Obviously these are different, as they are FLAT to 4 HZ.  and the SOUND level, well it's more for show, no meter can measure so with the earthquakes I've been it, it appears R5.2. and yes, things move around, neighbors seek safety and all that. 

Not to many speakers do full range. The JTR Noesis 215RT is one perhaps some of the big JBL cinema 3 ,4 or 5 ways. They still would need DSP in my opinion.

Yeah, Sliders , one of those inventions that are so simple but so ingenious.

@mapman  Interesting. I just listened to a couple of podcasts with Duncan/Darren and they are sub integration fanatics. They said that no full range speaker, even the Wilsons, are immune from some benefit from at least one sub.

Yes, I've moved them all over the place, etc. Bought sliders. Best. Tweak. Ever.

QUESTION: Bit of a side question -- At present, I have my REL hooked up to BOTH mono block amps' speaker terminals -- left and right. This has worked really well in providing left/right sides to my single REL.

However, now I have 3 subs -- two Rythmiks which hook up the the L/R on the PRE-amp, and the REL, still hooked up as it was.

So --  one Rythmik to Left Preamp RCA, one Rythmik to Right Preamp RCA, one REL to BOTH R&L Amps speaker terminals.

QUESTION: The REL has forced me to keep my monoblocks about 3 inches apart. Can I now just have the REL connected to one monoblock rather than two? I know that technically the answer is yes, because that's the design in the first place. But the other factor is that now two subs will be connected to one channel (say, Left) and only 1 sub will be connected to the Right channel. Make any difference?

@djones51 @soundsspectacular 

Yes, I listen nearly near field. I bought speakers based on how they sounded in this space. My stands are at 20" (not the usual, higher 24 or 27") and I sit a bit lower, too. I have carpet and ceiling absorption, too.

djones51,
He is dealing with subwoofer issues , not mains.

Low ceiling is a challenge the first consideration would be get a speaker with a very narrow vertical dispersion and have the listening position nearfield. 

Excellent point about your ceiling height, I should have thought about that and asked ( or maybe you mentioned it in an earlier post and I missed it ) because I do benefit from having 12 foot ceilings and though obviously  being a completely different animal when I went to Atmos surround I knew immediately the ceiling speakers integrated well for that very reason. I can just imagine the challenge of dealing with just 6 1/2 feet overhead!!

These are  great suggestions and I really appreciate them. 
For the moment one thing is absolutely certain : with 6 1/2 foot ceilings there is no way that I am going to get a great result even with the technology you are mentioning. At this point my best option is to try to learn how to optimize my room with what I have. Because even if I have a more sophisticated tool it is only going to drive me toward recognizing a foregone conclusion, namely that I have the limitations that I’m already close to confirming, I believe. When I am able to move rooms, hopefully in a year or so, these tools may be much more appropriate.

REW can do so much more when implementing the MiniDSP along with it, it's not just a sweeping tool, it's an all in one turn key solution. The Driverack is a great piece of equipment, I used the original 360 model back in the day in a professional environment,  but you can do all the things ( and more ) the DBX Driverack can for 20% of the price with REW ( free ) and the MiniDSP ( $205 ) for up to 4 subs.
You measure each sub separately then measure them all together ( gain matching should be done before you start ) and you can see the difference after all have been measured together. Then you start delay comparisons ( with sweeps ) and after you find the best combination of delays you go to the EQ section of REW and that's where the magic begins. You create a room curve of your liking ( you don't want total flat response ) and after going through the settings then hit the "Match the Target" and REW equalizes your original measurement ( of YOUR room with all it's acoustic anomalies )  to the "room curve" you've determined. It has used a 10 point parametric EQ to do it ( including Q control ) and you can continue to manipulate it ( and if it didn't use all 10 points you can add to it ) to make it better.
I'm sure you have had successful  improvement from just using the sweeps and adjustments you made but REW / MiniDSP will take it to the point your attempting to get to. You will be absolutely amazed and will enjoy your 2 channel system in a way you hadn't even imagined.
 

JI use the DBX Driverack VENU360. It has 6 analog outs (xlr), four which can be used for subs. Each sub can be “tuned” to your liking with delay, polarity, dB gain, off/on all from your laptop, phone or iPad. You can also control your two mains with “Q” control, graphic and parametric eq’s as well as all of the above options. It also has a subharmonic control that can be very useful.
I’ve been very leased with the results.
Did I mention it also has a built-dac? I don’t use it, but it’s there if you need it.

hilde 45, relative to Sub Woofer Placement 3 Subs are IDEAL!

Here's my solution for  optimization of results, with 3 subs.  

1) Set of 12 inch, self powered 500 Watt Subs at Far Left & Right of room, set @ 70 HZ Crossover.

2) Single 15 Inch Sub Directly in Center. This Sub Woofer is Fed its signal from a dbx 234S Electronic Crossover set @ 40 HZ Crossover Frequency, & set to SUM Left & Right Channel Inputs, which signal is in turn fed to a Classe 25 in Mono Mode, putting out an honest 1,000 Watts. dbx 234S gets its signal directly from the second output of my pre-amp.

3) Combined with PS Audio BHK Signature 300 Mono Blocks, feeding a pair of Anthony Gallo Acoustic 3.0's, three way speakers.

This combination of Speakers puts out Exceptional Non Boomy Bass with Massive Slam, as the 15 Inch Sub Woofer is driving directly into one, when they are sitting in the sweet spot.

I find the "Single Very Low Bass Sub", summing both Left & Right Bass signals to be optimum for Deep Bass, while not interfering with the music that one plays.

Try it, you will like it!

Did you get a response 
from  The Benzman   ?

@mapman

You have to jump ship on the measurements at some point.

I’m not sure if you’re giving me this piece of advice, because I mentioned (I thought), I’m going back and forth, measurements to listening to measurements, etc. Better measurements reveal themselves in a listening experience that reveals more than I was hearing before and it has raised my standards, both as a listener and in terms of what I knew my room was capable of. It’s easier to give me advice if I’m a "measurementalist" but there’s no way that impression could be fairly assigned to what I’ve been saying. Listening is the final test, because after all, I didn't buy a hifi rig so I could run sweeps!

Are these devotions from ruler flat response something you are hearing that affects your listening pleasure or is it something an electronic piece of equipment is telling you is not correct?

@arrowheadrss Not sure where I expressed a fixation on ruler flat response. That’s not realistic and I know it’s not desirable. I’m treating the measurements as one might treat a BMI reading. If it says you’re obese, well, who knows if that’s the right word, but it’s safe to think that dropping a few pounds is to your benefit.

Right!
So how does it sound?

It can’t be complete  until you do the final tuning to your ears with music.  You have to jump ship on the measurements at some point.  That just gets you into the game. 

Poorly designed rooms will ALWAYS have peaks and nulls, feel blessed your's are not any worse than what they are. Are these devotions from ruler flat response something you are hearing that affects your listening pleasure or is it something an electronic piece of equipment is telling you is not correct? We build rooms that are exclusively for 2 channel listening, after the initial construction is done we begin the laborious task of tuning the room to each owners personal taste. We have built approximately 100 of these rooms and have found that very seldom does a client ever choose ruler flat response (or as close as we can get to it) as the preferred sound of there room. Ruler flat response is over rated. Electronic equipment can help you achieve better sound but it (and other people) cannot determine what is the best sound for you, only your ears and brain can determine that. 

Thank You.

@golfnutz Happily.

Working very well in my room:

1 REL Sub (further away)
Phase: 180
Crossover: 100
Volume: 7 p.m. (3 tics)

2 Rythmik F12SE Subs (both behind and to the outside of each main, but not exactly equally):

Both set at:

Phase: 180
Crossover: 40
Volume: 7 p.m. (3 tics)
LFE Pass filter: 50hz
Rumble filter: Off
Extension Filter Freq: 20
Extension Filter Damping: Mid

@hilde45
I'm curious, can you post what your settings are on the 2 Rythmik subs please, thanks.

Update. After a lot of work yesterday, I’ve made good progress. I have no peaks over 4 db, and 4 nulls that are -5-6db and one big narrow one that is -8 db.

Scan results are on my system page:

https://systems.audiogon.com/systems/9064/edit

Basics of what I did:

• Started with a baseline scan. No subs.
• Assuming positions I had worked out before were adequate....
• Added 1 sub (REL). Adjusted in minute increments to (a) gain, (b) crossover, (c) phase -180 or 0.
• Added subs 2 and 3 (Rythmik). Adjusted in minute increments to (a) gain, (b) crossover, (c) phase, (d) various filter adjustments on sub
• Once those measurements were all optimized I adjusted:
• Front wall treatments, adding, subtracting, and moving.
• Side and other area treatments, same.
• Ceiling treatments -- doubled and adjusted position of existing treatments.

REW notes: Besides using REW to play sweeps and analyze the curves I tried something new (for me).

• I looked at the graph to identify the frequency where a peak or deep null was.
• Then, I’d play a constant tone and move a single treatment, facing the laptop screen display of the SPL meter, keeping an eye on the tone and an SPL graph next to it.
• When the the SPL graph showed a real decrease in a peak (or rise in a null), I’d leave the treatment there and then go back and do a sweep.
• Then, I’d repeat it and either shift treatment position or add more treatment there or nearby.

By doing this for the most problematic peaks and nulls, I was able to try new and more asymmetric combinations of treatment positions to really address the curve. In other words, I finally discarded my visual bias.

MiniDSP 2 x 4 HD, a calibrated mic ( Umik-1 or Dayton ), a db measurement tool of your choice ( decibel: db sound level app on iPhone is great ), REW app on your laptop, YouTube tutorial Episode 7 from "Hometheatergurus" channel ( along with the gain matching episode )  and you will get absolutely amazing results if your willing to go through the headaches of a learning curve. 
I have a Focal 1000F, Def Tech SC4000 and an old Def Tech SC-1
 ( how's that for a crazy ridiculous mix?!! ) and it literally sounds like I have a single subwoofer from the main listening position. The SC4000 is only about 5-6 feet behind the listening position so occasionally ( but rarely ) I have to adjust the volume but it has remote control and through my Harmony hub it's easy as pie to do.
  MiniDSP allows for 4 configurations ( again controlled through the Harmony hub ) that I have set from flat response to a couple of different mid bump options to play with depending on the movie or music track and my listening whim at the moment. 
  A long time issue I've dealt with from just one to two to three sub configuration is now a mute point. Although nothing is perfect, the technology available is a wonderful tool if your willing to give it a try. I guarantee it's better than any " by ear " method, I don't care how good your ear is or how long you crawl around your room. Your just finding bumps in frequency at different areas of your room and not flat response anyway . There are too many factors so let technology be your friend. You ( and your ears ) will be glad you did.

P.S. - room treatments would be a great addition to the equation. That will
         be my next step hopefully.

+1 on ceiling treatments, often overlooked.

Been testing all day, off the computer. I've definitely improved things a lot with systematic adding in of each sub and then doubling the amount of treatment at ceiling first reflection points. I'm now dialing in a variety of room treatments. Be back when I can.

@hilde45 wrote: "...the orange "morning" line is speakers only.  Improvement from "Morning scan, without subs" to "Afternoon scan, with subs" mitigates the dip significantly at various points, e.g. pulling up a null by 10 db at 129 hz, by 8 db at 241hz."   

Maybe I'm just slow, but eyeballing the curves I would have thought that Orange was WITH subs, and Green was speakers ONLY.   

Anyway assuming that's the only difference, AND that the microphone locations and other measurement conditions are identical, the curves imply that the subs are active pretty high up.  Where are you rolling off the top end of the subs?  

Incidentally the dip around 270 Hz and peak around 540 Hz look to me like floor bounce artifacts (perhaps modified by the ceiling bounce) and imo should NOT be EQ'd away.  

Duke

See my posts on bass and room treatment. A huge amount of boomy bass was eliminated with vibration control- Townshend Podiums and Pods- and a lot of the rest went away with F1 cables. Yes wire contributes to resonance problems.   

If I had gone the traditional tube traps first approach I would now be struggling to restore that which was being unnecessarily removed with expensive bulky tube traps. 

It's a new millennium, boys. One sub is out, DBA is in. Panels are passe, HFT are hot. Podiums trump traps. Etc, etc.

My steps on bass integration/room Eq. 

1st do appropriate room treatments, *this is the foundation for all that follows.
 2nd add multiple subs 2/3/or more.
 3rd add a crossover to eliminate mains from the sub                              
 4th integrate DSP in the Sub range.

Took my room size and layout out of the equation.





              

@mapman 

It helped that that room is thin dense carpet pad over solid concrete foundation. No floor resonance issues there like I have upstairs to deal with. If you have those, tackle those directly with isolation pads or equivalent under speakers.

I'm on concrete, too. 2/4 walls are brick. Not a symmetrical room but not much resonance.

@gosta  The guys on the hifi podcast just described a guy who spent 150k on a room for listening using treatments, and other tools and it still has problems. 

So in my case, FWIW, I’ve been able to get the sound I want with a sub and good but not full range small monitors (KEF ls50 meta) simply by getting the mains setup optimally first, then using decibel app on iphone and streaming white noise to get the sub to visibly fill in the missing lowest octave. Only three controls to play with on one sub, a Klipsch sw308: level, low pass cutoff, and phase. I eyeballed it with the meter app, then sat down with some music to fine tune the sub. It’s perfect to my ears now! Took about 30 minutes to get it dialed in (sub controls are accessible from main listening position). Discovered I had not landed anywhere near the right level and settings for the sub by ear alone. Low pass cutoff way too high and level way too low.

It helped that that room is thin dense carpet pad over solid concrete foundation. No floor resonance issues there like I have upstairs to deal with. If you have those, tackle those directly with isolation pads or equivalent under speakers.

Of course all rooms and ears are different. Also experiments are how you learn. I learned never make these things any harder or more complex than necessary to deliver results that are technically good but more important pleasing to the listener.

NExt step would be DSP just to see what happens and if worth it, but I am at a good place now so not much incentive to dabble more than needed at present. Maybe someday when I retire.

@tvad 
I believe that was very good advice from the manufacturer. No dsp software is perfect but you won’t succeed without. You may think so though...

@mapman -- I'm not against it, absolutely, but want to see if I can make a casserole with what I have and with the skills I have. I've spent a fair amount to have more than decent cables and DAC, so to add something into that mix is not necessarily about "polluting" the signal so much as adding an element that will change the character in unintended ways, even as it may be correcting other outcomes. But I hear you. Not ruling it out.

@tvad  That's a good object lesson. And I'm not aiming for Howard Hughes levels of cleanliness in line response. My issue is that I can hear the bump that I see measured. I tested that out last night -- I found a track of acoustic bass on a Chesky recording that goes up and down the scale, knew instantaneously where the muddy/tubby section was, measured the frequency of those notes on an analyzer and then compared to my REW graph. Exact match. If I can at least manage a couple unwieldy peaks, I will not have lifeless music, but I will eliminate flaws which my ears can hear. That's the goal.

That said, we all remember Hawthorne's short story, "The Birthmark," where his otherwise beautiful and kind wife has a birthmark which the protagonist insists on removing? Spoiler alert: the process kills her.

a good quality parametric equalizer or DSP would really be the simplest and most cost effective way to fix things in a problem room rather than a complex sub setup in a system that does not seem bass starved to start with.

I know, I know, more stuff in the signal path. So what? As long as its good stuff? Audiophiles get too anal about these things sometimes. THe end result is all that matters. With digital anything is possible. Them’s the facts!  Digital is your friend!  Stick some tubes upstream if you must.

Whatever works best.

@djones51 In the image I posted yesterday -- which I didn’t label specifically enough -- the orange "morning" line is speakers only.

Improvement from "Morning scan, without subs" to "Afternoon scan, with subs" mitigates the dip significantly at various points, e.g. pulling up a null by 10 db at 129 hz, by 8 db at 241hz. At other points, the later scan makes some things worse, but overall, the subs were helping.

Morning scan, there's another big dip between 2khz and 10khz. Afternoon scan mitigates that by a very large amount (varying, but up to 7 db mitigation).

How high are you crossing the subs? Looks like it drops between 90hz and 500hz and another big dip between 2khz and 10khz. What does a measurement without subs look like? 

@audiokinesis 

Thank you, thank you! for your help. I'm saving this email and printing it out.

Here's the result of my work before your advice, over the course of the day. It's the top slide on my system page: https://systems.audiogon.com/systems/9064/edit

Might it be a floor-to-ceiling mode? Do you have a lower than normal ceiling?

Oh definitely. 6.5' ceilings. I told this to Dennis Foley and he said, bluntly, "Get another room." Sigh.

Thanks for the compliment on the Salks! When I did extensive speaker placement analysis (with the help of brownsfan) I found that 6'4" from front wall was optimal. Today, I've added a few inches more and had some luck with that. But the bass hump ain't moving much. A little but not enough. Nulls still painfully deep.

I'll try that overlap cancellation thing. Had not considered it. The Rythmiks use a line-in RCA so not sure how to manage that with them. The Rel seems easy enough.

I'll try stuffing some foam in those beautiful front ports.

I am a bit daunted by the idea of wiring a capicitor but it is probably easier than I imaging. I'll save this email for future reference.

Good to know that 3 gets me in the ballpark. I was under the impression that the idea was "Get 4 or go home."

I'll try to elevate one of the subs....closer to the ceiling. If you know a good orthopedist, that might come in handy.

There is one sub presently closer to me than the speakers. I'll try to roll off the top ends lower and steeper on that one.

I'm glad you mentioned deliberate phase variation between the subs; I was worried about keeping them symmetrical, but since the room is going to be different where each is, that assumption doesn't really make sense.

@mijostyn
I'm not an electrical audio engineer by any means but have had lengthy conversations with a couple. And to my understanding -

It's the other way around.

Digital is machine code/computer code. Analog electrical signals are everywhere else. 

DSPs are doing more conversation from things that are all ready converted (from square waves to sine waves). I'm sorry I want as few conversations (between wave types) in my chain as possible; especially an extremely low quality converter down stream from my EXPENSIVE converter. 

Low frequencies are a pain and yes a DSP "makes things easy" because most people are not going to test their subs moving them a 1/4 inch and changing distance between the floor and yes a 1/4" movement can make a difference with a sub just as it can with the mains.

Do "car" guys not know how to change their oil?

To me (and I want to make this completely clear) using DSP in MY system is taking my car in to get an oil change. Many people can and do choose to use a DSP; I'm only saying that there are alternatives to spending money and adding to the chain. Other peoples priorities are different than mine. If he decides to use one good for him, that works for him, if he decides to not use one, good for him.

But for the vast majority of people to say that DSP is the ONLY way is just completely ignorant. 

@hilde45 , thanks for your answers. You’ve obviously worked very hard on this and your results really are quite good, which makes that 88 Hz peak stick out like a sore thumb all the moreso!

Might it be a floor-to-ceiling mode? Do you have a lower than normal ceiling?

At any rate, here are a few ideas:

- I agree with @erik_squires that THIS is the sort of thing EQ is good at fixing (bass traps too, but I think EQ would be more cost-effective).

- You might try placing the Salks (very nice speakers, by the way) about six feet out from the wall behind them, which will result in the low frequency reflection off that wall arriving ½ wavelength behind the front wave at 88 Hz, hopefully providing some useful cancellation.

- Place one of your subs near the Salks. Run it up high enough that its output overlaps with the Salks in that 88 Hz region, and then adjust the phase control until the sub is CANCELLING the Salks enough in that region to make the peak live-with-able. If you can’t get the cancellation you need going from 0 to 180 degrees, then use the speaker-level inputs on that sub (if you aren’t already) and reverse the polarity of the signal going to them, such than now your phase control is effectively doing 180-360 degrees. You may need to do this overlap/cancellation trick with more than one of your subs, and/or you may need to use the parametric EQ in one or more of your subs to enhance the cancellation effect.

- The contribution from the Salks across the bass region may result in too much net bass energy before you can fully take advantage of what the subs can do. If so, stuff some open-cell foam in the slot ports of the Salks to disrupt the airflow, turning the box into an aperiodic enclosure. If this is a net benefit, you can look forward to further hours of audiophile fun as you fine-tune the foam-in-the-slots. 

- Another way to reduce the contribution of the Salks in the bass region is to wire a small capacitor in series with the amplifier’s input, perhaps by performing amateur surgery on an inexpensive interconnect. You can use an online first order highpass filter calculator, substituting the amplifier’s input impedance where the tweeter’s impedance would normally go. You will probably have some trial-and-error chasing down the best capacitor value.  (Maybe your system already has an easier way to roll off the bottom end of the Salks, but if so I overlooked it.)

- As a ballpark rule of thumb for a distributed multi-sub system (I avoid using the otherwise-convenient term “DBA” because it can also mean “Double Bass Array”, which is something very different), you want to get the subs spaced as widely apart as you reasonably can while distrbuted in as many dimensions as you reasonably can. My mentor Earl Geddes finds two subs are much better than one, and three subs are much better than two, and four subs are an improvement over three but not by as much. So imo you are definitely playing the distrubuted multisub game already! If you can elevate one of the subs so that it is closer to the ceiling than to the floor, you get bonus points. This is one of the things that @hleeid did to get good results in his 11 x 13 foot room; I think he actually elevated three of the four Swarm subs, as that was more practical than the other way around in his room. In your case though, I would still keep at least one of the subs near the Salks if you try that overlap/cancellation thing. For any of the subs which are not near the Salks, and especially if they are physically closer to you than the Salks, you want to roll off their top ends lower and steeper, so they don’t betray their locations by passing upper-bass energy loud enough for you to hear. If that’s not possible, then imo ideally you’d want those other subs to be farther away from you than the Salks so that their output is not the first-arrival sound.

- In my experience it is usually beneficial for there to be some deliberate phase variation between the subs, so don’t be afraid to twiddle those phase controls. The effects of the phase controls are more subtle than the effects of the subs’ volume and low-pass frequency controls.

Hope there’s something useful in this.

Duke

Hilde45, you absolutely can use a MiniDSP with powered subs you just bypass the crossover section. Many subs have a switch to do this.
powemi, the vast majority of sources now are digital, analog is the outlier except for a few very stubborn individuals. You just stay in the digital domain until you get to the DACs then amplifiers. If you have a turntable you use a high quality ADC to convert to 24/192 which is entirely invisible. Digital crossovers are far superior to analog ones in every way. The advantages of using digital signal processing and digital crossovers far out weighs and disadvantages. 

The instructions most sub manufacturers invent for integrating subwoofers are laughable. Using a one way crossover and trying to avoid matching speakers in time is...pathetic but otherwise there is no way they can be cost competitive. 

All good. It’s also possible the speakers are not flat down to their lowest rating. Not uncommon. You would have to measure with a test signal alone to know as a baseline then add the subs. Room size, acoustics and amp are factors for that. Bigger rooms always need a lot more muscle for flat extended bass. Power needs increase exponentially with lower frequency and many  main amps alone are not up to the task of doing it alone at the lowest frequencies.

@mapman

@hilde45 did I read correctly that your subs go down to 35hz and your mains also not much different in terms of low end extension?

Subs go lower than 35 hz. The mains are listed at 35 hz. I do not know their roll off slope. In the past, the addition of a single REL to these speakers always helped noticeably. Not dramatically, but noticeably.

You may be right that there’s not much to get from a 3 sub array. I’m definitely trying to test this out in the 30 day trial period for the subs.

To volume match, I need to see how I can get just the subs to play without turning off the tube amps.

No turntable.

If your mains are truly somewhat responsive into the 30s hz, benefits of using a sub at all is marginal to start with. The control flexibility of even one in your case (rhythmik) would help.

This is what Jim Salk said. BUT, I did notice a difference with the RELs. Let me add a report of the latest scan I did (I'm doing them right now):
I increased the bass about +5-6 db from 20-60hz, from nulls to small peaks (up to +3.5db) or so. This is just the latest scan and as you can imagine, pulling all those dips to the flat line or a little above is very hear-able.

Now if you are crossing over the mains at a higher frequency and offloading the low end below to the subs, then we are talking. That would have benefit of offloading work from you main amps which should be a good thing if done right.

I do not have the technology right now to do that.

@hilde45 did I read correctly that your subs go down to 35hz and your mains also not much different in terms of low end extension?

If so, unless the 3 sub array is smoothing out the response at your listening position, there may not be much if any benefit with using any subs at least for those seeking flat response.

Your subs have a lot of controls though which should help tune in however many subs you throw at it to improve whatever might be possible, so that is a good thing.

Your sound meter is your friend. I used white noise as a source to get my sub tuned in optimally with minimal effort.

Some might seek more bass, not necessarily flat response. No problem. To each their own.

Generally, from a pure technical perspective though, you primarily use subs to extend the low end to pick up the lowest octave down to 20hz or so that is missing otherwise. If both subs and mains have same extension to lower 30s hz, they are merely adding more of what you already have, nothing new. Your bass down to the low 30s hz is a combo of mains + subs and you are still not picking up the full lowest octave most can hear (if even in the recording to start with which is typically not a given except with some better recordings involving instruments that produce music down there). See chart:

https://i.pinimg.com/originals/8b/4a/6f/8b4a6fd7b8d65711eed41850a194284e.jpg

I would think it could be very difficult to get a sub array to smooth out response ideally when the mains are also contributing.

If using a turntable, you may pick up power draining rumble or feedback down there which is a bad thing and should be eliminated or filtered if present and not done so already in the phono section of the amp, so need to be careful there. Are the woofers noticeably moving with a record playing and no music? That’s the sign if so. Not an issue with digital sources.

If your mains are truly somewhat responsive into the 30s hz, benefits of using a sub at all is marginal to start with. The control flexibility of even one in your case (rhythmik) would help.

Now if you are crossing over the mains at a higher frequency and offloading the low end below to the subs, then we are talking. That would have benefit of offloading work from you main amps which should be a good thing if done right.

Duke is the bass array man. See what he thinks.