To Sub Or Not To Sub, That Is The Question

[Kingrex]

If you are looking for an amp that offers bass cut off to the main speakers, take a look at the NAD M33. Its Settings allow for a roll-off of your choice between 40 and 200 Hz and (if you tell the amp you are using 1 or 2 subs), the pre-outs are set to match. So if 80 Hz is selected, you main speakers will be protected from those lower frequencies and the pre-outs to the subs will get only those low frequencies.

The new NAD M66 preamp goes a stage further with its 4 dedicated sub outs (single ended and balanced) and these can be tailored for room acoustics via the built-in Dirac Live Bass Control. I'm likely to get this preamp and look forward to trying that particular feature - if I keep my subs!

The M33 uses Purifi Eigentakt Class D technology, but that's to its speaker sockets. If looking for good Class D power amp for subs, the NAD M23 or Atma-Sphere Class D monos may be worth investigating. However most subs seem to include their own Class D amps that are typically 500 - 1000 watts - the ones I mentioned are lower powered.

Just an amp. The Ashley I linked is the crossover controlling up to 6 subs. Stereo amp $1500 or less. 200 watts. Small and light.

 

[LL21]

I'm not a speaker designer, and my grad courses in acoustics were long ago, so take anything I say with a block of salt. And I have not done professional analysis for 10+ years now. Unfortunately experience does not always go hand-in-hand with competence (*).

My last significant experience with Wilson was long ago and the Alexandria XLF costs more than my house when we built it. Looking at their specs and the Stereophile review is interesting; the bass response has a large peak, but John noted it is due to the near-field measurement, so I do not know their "true" response. It looks like the big port is tuned to ~19 Hz, pretty low, but should augment the bass to and a little below that point. JA later indicates they have extended response to below 20 Hz, so to me subs would be to counter room modes, and perhaps get another octave into the low organ and percussive range. Too bad he does not measure distortion though he said he expects it to be low. The XLF ports both woofer(s) and midrange drivers, a fairly unique feature, I think.

10 kW sounds like a lot of power, especially class AB, but a pair of dual-opposed 18" subs properly placed and integrated should certainly be "a reasonable target". Your room is near a 2:1 L/W ratio so modes could be an issue. Hopefully you are not sitting right in the middle of the room; a sealed rectangular room has a primary mode (null) right in the center. I usually prefer ~1/3 or ~2/3 positions for listening. If you are planning to place the subs physically beside the XLF's that may or may not be optimal depending upon where they sit -- I assume they are out in the room a ways? You could check out Todd Welti's paper on sub positioning for some insight: https://www.harman.com/documents/multsubs_0.pdf

That is a fairly large room; is it sealed, or open to the rest of the house?

In my system, in a fairly small room, I went with four smaller (12") subs for more flexibility in placement and ability to smooth the response. I do not need the output (more than enough from the little quartet), but having multiple subs scattered around provides flatter in-room response. My response is -3 dB at 7 Hz, but there are some significant peaks and valleys I cannot eliminate due to room size, wall boundaries, and so forth.

I did laugh at "foundational bass"; a pair of those subs paired with the XLFs should crack most foundations!

HTH - Don

(*) Experience comes from making lots of mistakes; wisdom is learning from them. So far, I've lots of experience... - me

Thank you! Very very helpful! Yes, speakers are 1/3 in and we listen from the opposite 1/3rd. And sub is on the listening end of the 1/3. Set up with mikes/measurement was reported as flat to 25hz and -5db in-room at 20hz at the listening point.

 

[Minnesotafats]

But your main speakers where not designed to play lower than 100 Hz, the sub towers where designed with similar material drivers and the crossover is very adaptable especially on Mk 2 versions.

True......however with back up system my MBL 101s I use 2 Rel N31s right next two each main speaker....I miss the subs greatly when they are off....

 

[Ron Resnick]

my MBL 101s I use 2 Rel N31s right next two each main speaker....I miss the subs greatly when they are off....

Do you bring up the RELs alongside the main speakers?

 

[Holmz]

....I miss the subs greatly when they are off....

If we know they are on, then that is usually not a great sign.

However when we are not sure that they are on, and damned well sure know when they are off, then that is often a pretty good sign.

 

[Lagonda]

True......however with back up system my MBL 101s I use 2 Rel N31s right next two each main speaker....I miss the subs greatly when they are off....

Are you using a crossover on the 101's ? I prefer my 101's with subs too.

 

[Al M.]

If we know they are on, then that is usually not a great sign.

However when we are not sure that they are on, and damned well sure know when they are off, then that is often a pretty good sign.

Why? It depends on what you want to achieve with the subs. For my purposes, see #25. If you want to support the bass, of course you know when they're on, even if they blend perfectly with the main speakers. Yet as I write in my post, that depends on the specific music.

 

[Holmz]

Why? It depends on what you want to achieve with the subs. For my purposes, see #25. If you want to support the bass, of course you know when they're on, even if they blend perfectly with the main speakers. Yet as I write in my post, that depends on the specific music.

I guess it depends on whether we are looking at a full range speaker or something that tapers off closer to 100Hz.


Your post #25…

…

I do not use an external crossover, just the roll-off filter on the sub, with the speakers receiving full signal. With the floorstanders I use a slightly lower crossover frequency, (50 Hz vs 60 Hz) but importantly, the much steeper 24 db/octave roll-off rather than the shallow 12 dB/octave roll-off with the monitors.

I see…
I am using floorstanders that are receiving a HPF’ered signal.

So it can appear that the sub(s) is/are not working, as the sound appears to be coming from the floorstanders.
But when the sub, or subs, are turned off, then it is like, “where did all the bass go?”

If I was using a sub with the floor standers playing full range, then the bass could be too much.
Half of the reason to use a sub would be to make the amp’s work a bit easier.
A 100W or 200W amp on a floor stander, is a different thing than a 100/200W amp on high passed signal, and then 300-1kW on a dedicated sub and sub amp.
If typically half of the power is in the bass, then I guess that is more like 200-400W for a sub, depending on the music.

I have set the subs so that they just support the music, not intrude in it. For example, the subs are now set with my floorstanders such that on Pink Floyd's Dark Side of the Moon there is basically no difference with subs on or off *), whereas on Pink Floyd's The Wall the subs give support to the lower bass frequencies on this recording -- a nice difference.
…

That first song, “Dark side of the Moon”, would be an example where I say mentioned “not being sure whether the sub is even on or not.”

The second song, “The Wall”, would be one where the where the sub(s) not being become readily apparent.
But my point was that the sub should be disappearing.
If they are not, then it is difficult to appear like a stereo image, when there are all of a sudden more speaker becoming apparent.

 

[Hear Here]

If we know they are on, then that is usually not a great sign.

However when we are not sure that they are on, and damned well sure know when they are off, then that is often a pretty good sign.

Yep! With full-range main speakers, subs (like small children) should neither be seen nor heard.

That's what I'm trying to achieve, but (as your last point says), it would be good to notice the difference if the subs are turned off. Do others (with full-range main speakers) expect anything more from their subs? Thanks

 

[LL21]

If we know they are on, then that is usually not a great sign.

However when we are not sure that they are on, and damned well sure know when they are off, then that is often a pretty good sign.

Agree!

 

[Al M.]

That first song, “Dark side of the Moon”, would be an example where I say mentioned “not being sure whether the sub is even on or not.”

The second song, “The Wall”, would be one where the where the sub(s) not being become readily apparent.
But my point was that the sub should be disappearing.
If they are not, then it is difficult to appear like a stereo image, when there are all of a sudden more speaker becoming apparent.

Of course the subs disappear completely. I said that they blend perfectly with the mains. Yet on the second album, "The Wall", there is deeper bass -- and yes, the bass sounds like one entity, as if coming solely from the main speakers.

Isn't that the whole rationale what subs are for, to provide deeper bass?

 

[Minnesotafats]

If we know they are on, then that is usually not a great sign.

However when we are not sure that they are on, and damned well sure know when they are off, then that is often a pretty good sign.

I miss them when they are off because the sound stage is just less. I use the Cowboy Junkies Trinity Session Album for some test tracks if that gives you an idea of the music I care most about.

 

[Minnesotafats]

Are you using a crossover on the 101's ? I prefer my 101's with subs too.

No crossover on the 101s. The Rels are at 29 hz. I have them right next to the mains to avoid/reduce phase issues.

 

[Minnesotafats]

Do you bring up the RELs alongside the main speakers?

Yes. To reduce/avoid phase and timing issues. Worked in my room.....maybe not others.

 

[LL21]

I miss them when they are off because the sound stage is just less. I use the Cowboy Junkies Trinity Session Album for some test tracks if that gives you an idea of the music I care most about.

Yes, I have had this happen with live jazz club recordings where you are immersed in the club performance...you mute the sub, and it's like SNAP...you are back in your own living room, and there is some music coming from across the room. Unmute -- and you are back inside the jazz club.

 

[Hear Here]

Yes. To reduce/avoid phase and timing issues. Worked in my room.....maybe not others.

No crossover on the 101s. The Rels are at 29 hz. I have them right next to the mains to avoid/reduce phase issues.

Placing subs close to main speakers with 12" bass drivers rather surprises me, because the MBL's surely don't need more bass? Earlier in this useful thread, it was said:

I think one should start with considering WHY one is adding subs. What are you trying to achieve?

More bass? Deeper frequency response? More sense of ambience / immersiveness / sense of room? More even bass response?

If main speakers are full-range and don't need more bass or deeper frequency response, then the other attributes are presumably the reason for adding subs to full-range speakers. I've rather thought (though possibly wrongly) that to achieve these other advantages of countering modes, etc, subs should be placed well away from full-range main speakers.

As this is my first sub purchase (2 x REL S812s), I'm floundering around rather, but starting on that premise - that subs supporting full-range speakers should be placed where they may be able to deal with room-related acoustic problems that the main speakers can't resolve. The more advice I read, the more confused I get !

 

[sigbergaudio]

If main speakers are full-range and don't need more bass or deeper frequency response, then the other attributes are presumably the reason for adding subs to full-range speakers. I've rather thought (though possibly wrongly) that to achieve these other advantages of countering modes, etc, subs should be placed well away from full-range main speakers.

As this is my first sub purchase (2 x REL S812s), I'm floundering around rather, but starting on that premise - that subs supporting full-range speakers should be placed where they may be able to deal with room-related acoustic problems that the main speakers can't resolve. The more advice I read, the more confused I get !

This is in essence correct. What "well away from subs" means will vary from room to room. Sometimes it is actually enough to break the symmetry of the speaker setup. So placing one sub on the outside of the left speaker and one sub on the inside of the right speaker, or the other way around depending on what gives the best result.

Such a setup may not be the best possible positioning in a given room (but it could be), but it can be a good compromise between practical placement and bass response. It is also close enough to the speakers that you can run stereo subs with a pretty high crossover if you want.

Sidenote: To find the 100% optimal spot for several subs (if that is the goal) without measuring the bass response is near impossible.

 

[Minnesotafats]

Placing subs close to main speakers with 12" bass drivers rather surprises me, because the MBL's surely don't need more bass? Earlier in this useful thread, it was said:



If main speakers are full-range and don't need more bass or deeper frequency response, then the other attributes are presumably the reason for adding subs to full-range speakers. I've rather thought (though possibly wrongly) that to achieve these other advantages of countering modes, etc, subs should be placed well away from full-range main speakers.

As this is my first sub purchase (2 x REL S812s), I'm floundering around rather, but starting on that premise - that subs supporting full-range speakers should be placed where they may be able to deal with room-related acoustic problems that the main speakers can't resolve. The more advice I read, the more confused I get !

The 101s sounds better with subs.

 

[sbnx]

I agree with sigbergaudio. Even if a person knows nothing about acoustic measurements it would be less time to learn to use REW and measure to place the subs than just guessing and being wtong 99% of the time.

 

[Holmz]

Of course the subs disappear completely. I said that they blend perfectly with the mains. Yet on the second album, "The Wall", there is deeper bass -- and yes, the bass sounds like one entity, as if coming solely from the main speakers.

Isn't that the whole rationale what subs are for, to provide deeper bass?

Yeah - but I am not sure how that is done with a full range speaker without filtering out some of the sub frequencies.
It seem like one would have too much energy somewhere.
- Either too much below 40Hz,
- or if the main speakers started at 60 Hz, then too much in the 60-8100Hz region.

Of course with a room, and modes, it may all just work out fortunately.
But luck is not a plan, so in a different room it could end up be a disaster,.
And working well with your speakers, may not be replicated with other speakers.

But at least the OP has a sense of what it should be like.