Deep dive: Questions after reading Toole and Geddes for stereo setup.

[krivium]

Ok i got it.
Thank you Earl.

 

[johnp98]

I strongly recommend that you have three front speakers as almost anyone will. But they should all be identical, which makes for the only solution is the speakers behind the screen. If I were you I'd just screen off a whole end of the room and put all the speakers and lots of damping behind it. It doesn't have to cover the whole area, but the vast majority of it.

Perfect. Will do!

See, that's not possible. Going one way enhances one and the other not and visa-versa. The relative rates may change, but not the overall situation - if that makes any sense.

That makes sense, I will have to play around with this and see what I prefer the most.

As to pointing, I'd always prefer a toe-in - I'd put you speakers somewhat near the side walls point in almost 45 degrees - your room is so narrow that getting the speakers away from the walls will be difficult. The expected listening range for this would be back from the speaker plane about the same distance as the speakers are apart. That's the sweat spot in narrow rooms like ours - mine is 14 x 22 ft. though, a bit better ratio than yours.

I have also preferred this larger toe in and will have to also tinker around with it with my new listening setup and thanks for the suggestions.

I've heard that near field works very well, especially if sound leakage is a problem. But I don't think that it would compare with a well sealed room with some 5 subs around it. But, I expect that it's a great solution when needed.

Yeah I don't have 5 subs at this point... and the back end of the room is quite leaky, so I have enjoyed nearfield sub placement, but I realize that it is more ideal and tactile for the prime listening seat.

E-mail me and I can get you foam.

Will do! Very generous to offer, I live in Canada so who knows if that will make shipping prohibitively expensive but Ill message.

Thanks again.

 

[krivium]

About the 5 subs: Earl's proposal about multisubs includes your mains ( they are supposed to be wideband - include a low or sub way) and 3 more subs.
So overall you'll have 5 sub emmissive spot as a whole for a stereo setup.

For HT you'll have one more emmissive spot with your C (surrounds are usually limited to 80hz so they won't count in it).

This won't do bad but you won't gain either in Earl's approach: 3 subs and the mains are the point of diminushing return in this approach.

 

[johnp98]

About the 5 subs: Earl's proposal about multisubs includes your mains ( they are supposed to be wideband - include a low or sub way) and 3 more subs....This won't do bad but you won't gain either in Earl's approach: 3 subs and the mains are the point of diminushing return in this approach.

Right, I remember that he said beyond 3 was diminishing returns and that the mains can contribute. So I guess in that case I have 4!

 

[bradleypnw]

Earl Geddes provided more detail on his personal multi-sub setup here.

https://www.diyaudio.com/forums/multi-way/121590-cardioid-bass-6.html#post1492937

His main channels play down to 50 - 70Hz. He fills in below that with a narrow band Ultra-Low-Frequency bandpass sub. Then he adds two additional broadband subs at low volume level. But he adjusts them to the room through physical location and modification of input signals.

Two subs located close together are correlated.

https://www.diyaudio.com/forums/multi-way/121590-cardioid-bass-5.html#post1492786

Unless the two subs are decorrelated with a filter.

https://www.diyaudio.com/forums/multi-way/121590-cardioid-bass-5.html#post1492863

Todd Welti, Floyd Toole, and Sean Olive (Harman) use a different technique.

 

[bradleypnw]

For HT you'll have one more emmissive spot with your C (surrounds are usually limited to 80hz so they won't count in it).

I don't know. Read this by Earl Geddes.

These go up to about 150 Hz or so. Of course there is always some fitting of the subs into the specific room thats why I can't give you the exact numbers. (Someday I'll write-up how to correctly setup multiple subs in a room.) The BB subs are usually so low in level that you can't even tell there on unless you are right on top of them, so localizing on them is never an issue.

Think of it this way. The mains and the ULF carry the bulk of the energy, but there will be the inevitable holes in the response. Remember (or maybe you didn't know this) that holes are much deeper than peaks are high, its almost 2:1 (+6db to -11 dB on average). So to get good bass you have to fill in these holes or the bass sounds empty. Raising the bass level only makes it sound boomy. So in essence the BB subs ONLY fill in the holes and this is not really a lot of energy, but it makes a huge difference in both the measured response and the sound quality.

His broadband subs run from below 50Hz to 150Hz and aren't played at high level.

If your surrounds play down to 80Hz you will cover a portion of his broadband sub range.

 

[bradleypnw]

Yeah I don't have 5 subs at this point... and the back end of the room is quite leaky, so I have enjoyed nearfield sub placement, but I realize that it is more ideal and tactile for the prime listening seat.

How do you implement your nearfield subwoofer?

 

[gedlee]

About the 5 subs: Earl's proposal about multisubs includes your mains ( they are supposed to be wideband - include a low or sub way) and 3 more subs.
So overall you'll have 5 sub emmissive spot as a whole for a stereo setup.

For HT you'll have one more emmissive spot with your C (surrounds are usually limited to 80hz so they won't count in it).

This won't do bad but you won't gain either in Earl's approach: 3 subs and the mains are the point of diminushing return in this approach.

Yes, more than three have diminishing returns, but still an improvement.

Just remember that no two of my "subs" (anything playing below 100 Hz.) are set the same except the main channels. The three stand alone subs all have different settings of LP, gain, EQ, etc. It's the sum of them all that matters and so, yes, each sub has a lower output, in general, than any single sub or just mains would. This yields a lot of LF headroom, which for HT is a big requirement since film can, and often does, have substantial LF output.

 

[johnp98]

How do you implement your nearfield subwoofer?

Right now it is located directly behind the couch at the main / ideal listening location as COVID has significantly limited the number of people who come over and watch movies, so it is usually just my wife and I (and she is happy to give me the good spot).

I am of two minds about it, as it certainly does not have the best / flattest frequency response, but it does give a very tactile sensation for the bass that I seem to greatly miss whenever I move it to more 'ideal' locations..

 

[johnp98]

Yes, more than three have diminishing returns, but still an improvement.

Just remember that no two of my "subs" (anything playing below 100 Hz.) are set the same except the main channels. The three stand alone subs all have different settings of LP, gain, EQ, etc. It's the sum of them all that matters and so, yes, each sub has a lower output, in general, than any single sub or just mains would. This yields a lot of LF headroom, which for HT is a big requirement since film can, and often does, have substantial LF output.

When you integrate additional subwoofers I recall that you said that the frequency response is the main thing that you look at (I assume you are looking to excite different room modes, and thus mainly looking to fill any previous nulls) and that the phase and time domain are not important due to our lack of ability to distinguish to time domain with such low frequencies. Just wanted to make sure that is correct, and that I can change phase and delay focusing on the frequency response.

Do do you put individual EQs for each sub to generate a 'flat' response prior to integrating them, or put more global EQs to all of them so the final result is a flat response?

Also, I have found that the frequency response of my subs is better when it faces the wall (instead of out into the room). Mostly because there is a large null because of speaker boundary interference that is right in the 60-120hz range when facing into the room goes away. I assume that it is acceptable to aim the woofer at the wall instead of into the room eh?


It also seems that you have alluded to the fact that number and location and integration of subs is more important than large / high quality subs. Do you think that most any sub would be worth adding to ones system (as long as you don't drive it beyond its capabilities)? As I have a knack for finding reasonable subs for very good prices secondhand, and don't know if I could be adding these to my main system (as most of my secondary systems all now have a sub or two.

 

[gedlee]

Do do you put individual EQs for each sub to generate a 'flat' response prior to integrating them, or put more global EQs to all of them so the final result is a flat response?

I assume that it is acceptable to aim the woofer at the wall instead of into the room eh?


It also seems that you have alluded to the fact that number and location and integration of subs is more important than large / high quality subs. Do you think that most any sub would be worth adding to ones system (as long as you don't drive it beyond its capabilities)? As I have a knack for finding reasonable subs for very good prices secondhand, and don't know if I could be adding these to my main system (as most of my secondary systems all now have a sub or two.

I EQ both individually and then global at the very end including the mains, which I normally don't EQ.

Since I recommend a "dominate" sub - the first one setup, this one should be higher powered. The rest of the subs kind of fill-in and those can probably be smaller. But I caution that store bought subs in my experience are very very limited in output and clip at level much below their claims. I haven't found one yet that I admired.

Putting the sub to the wall is fine if it works better.

 

[krivium]

I don't know. Read this by Earl Geddes.



His broadband subs run from below 50Hz to 150Hz and aren't played at high level.

If your surrounds play down to 80Hz you will cover a portion of his broadband sub range.

I have read the link you gave and don't get the relation between what you quoted from my message and what Earl said. Could you put it in plain words?

I could go on about the design choices ( compromise) made for Summa and why they are 'limited' in lowend extension ( but i don't think that for typical 'pop' music they would be somewhat limited in room for a stereo setup without subs) but i'm not sure it is what you want to point ( and it would be simpler to ask directly to Earl!).

Same thing about your comment about surround. I could give you an insight about mixing but it may be too much Off Topic here so please clarify your point.

 

[bradleypnw]

Maybe I misunderstood you but surrounds that play down to 80Hz would behave as additional modal region sources similar to the two mains but not as low.

 

[krivium]

Ah ok Bradley!
They indeed are other source but decorelated ( they are discrete channels so have their own signals, same situation for mains and their low way or subs). As such for me they don't count ( even more so as they will usually be high pass filtered at matrixing during mixdown).

 

[Antoinel]

I have to chuckle at that one. My "front wall absorption" is a giant wall of waveguide foam scraps all piled high from floor to ceiling, about 3 feet thick. Scrape from years of cutting foam for speakers. Scrap was > product - ouch! It is one heck-of-a sound absorber! Think anechoic chamber wall.

Hello Mr. Geddes,

I hope that you are well. I asked Google: does foam emit volatile organic components [VOC]? Its answer is YES.

This thread is an advanced "deep dive" course; which is worthy of daily study.

Please visit the last few posts of the thread in the Pass Labs Forum which I entitled "DIY the device of US Patent 4,899,387"; granted to Mr. Nelson S. Pass. I show another stereo setup seating in my listening room; which is fully satisfactory.

Best wishes,
Anton

 

[gedlee]

That's not what I read when I Googled that. Yes, there are VOCs emitted right after the foam is form, but like paint these dissipate to near nothing in a fairly short time frame as the material cures. They are used in all kinds of household products (including air filters) and I have never heard that VOC were a problem. They have no smell - unlike paint.

I am not a member of that forum.

 

[Antoinel]

I am glad the current status of your foam does not pose a health issue.

I am not in any VOC forum. As a chemist, your post triggered VOC in my head; out of concern and awareness.

 

[gedlee]

Wrong forum.

 

[Antoinel]

Hello Mr. Geddes,

I'll continue to look forward to your valuable contribution [and those of others] in any Forum/website available. I grasp your [not VOC] forum answer.

I've attached the layout of my stereo set-up. I hope that I am not intruding on this thread. I am experimenting with bass management in the corner opposite to my seat which is 1-2 feet away from my corner.

Best wishes
Anton.

 

[gedlee]

You sit in the corner for listening!? Most would agree that that is a very bad idea because of the near wall reflections. Toole makes a strong case for this.