Why the fuss with subwoofer specs and brands?

[jsilvela]

Notes: This is intentionally oversmoothed so it's easier to understand. The 100hz dip on the 105dB line is a measurement mistake on my part, not compression. The 115dB measurement is probably invalid because UMIK-1 compresses at 112dB unless you open it up and change the gain dip switches, but it's there for fun.

View attachment 253517

So you can see my system plays almost dead flat up to 100dB, pretty good up to 105dB, and by 110dB there's compression from 50hz that reaches -4dB by 20hz. Now, some might say "well that's crazy loud" and that's not true either. I've measured 107dB bass peaks in classical music at 77dB average SPL. I'm not going to say >105dB is a common scenario, but >100dB happens all the time in the content I listen to.

Replying once again to this fantastic post.
Finally got around to doing some measurements on my sub.
And I see what you mean.
Below you can see my sub on its own (I know, I know, it's unEQ'd (room mode at 39hz), and also I have a Low-pass filter on it to integrate vs my mains).
I had been doing a series of 20-100hz sweeps of increasing volume.
And while the increases at lower levels had been uniform, at this level the increase at 20hz is about 1.5dB, but at 50hz it's about 3dB. Compression, as you say.
I did not continue increasing levels because I was already making all the windows vibrate and getting plenty loud to my ears.

However, and it's a big one ... it's vastly better than what I had, and at 30hz it's not half bad.
And... I have not heard a system with properly powered and integrated and EQ'd subwoofers.
So I guess I may not know what I'm missing.
For now, the lil' sub will do, and we shall see if I outgrow it.

 

[Andysu]

I have to say I also did not get what you mean by "b-chain". What is it?

b-chain is your output from avr rca outputs connected to any other outboard pro audio gear , inter connection cables dsp crossovers PEQ amplifiers cable speakers EQ tuning of the speakers in the room is all part of the b-chain .

test gear commonly needed
volt meter multi meter
oscilloscope
booth monitor

so , you everone else can check everything out for yourselves no matter what the manufacture specs say .

 

[Andysu]

cheap booth monitor to connect avr amp outputs to the booth monitor to check levels frequency response ( with it's Test output connected safely to pc computer REW trueRTA ) easy to connect and cheaper than buying AP

it has 8 inputs for basic 7.1 the Lc Rc use them for back surrounds or if have two Dolby SDU4 recreate 70mm SDDS five screen that is good for go use on many movies even the ones that have directional foley/effects dialog panning .

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[Andysu]

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[jsilvela]

The Crawl is crude, but done properly can be very effective.
In order for it to work, you have to disable all Speakers excepting the Subwoofer. Then, you must get down on your hands and knees so you can listen where the Woofer itself will be.
For me, when I first did it, it took me about an hour to figure out what I was listening for. But once I did it was pretty eye opening. What made it all click for me was moving in and out of a corner and hearing how the quality of the Bass changed (from clean and precise to boomy and muddy). Once I caught on to that I was able to do the whole room pretty quickly, even finding a spot I was planning on putting a sub which was in a complete null.

For my own experience as a newb back then, I learned a lot about LF Acoustics and room interactions. I think it’s absolutely valid to do, even just as an exercise in opening your ears.

Of course, the final caveat is key: once you find locations that sound good, you will ideally place your Subs in those spots. But you have to keep an open mind to where the room acoustics tell you will be good placements and not what you want aesthetically.

I was curious about this, so I did a walkabout with the sub in its place.
I guess this is a "reverse crawl"? Or more like a chicken walk, as I was trying to keep my ears at "regular listening height".
After a while I started to get it. In some places, very boomy bass, I guess from a strong room mode. In others, fewer or tamer modes, and I could hear the music better.
Massive Attack's "Unfinished Sympathy" on loop, playing only through the sub.

What I had not gotten was all that talk of "nulls". I can hear bass pretty much everywhere. So I guess it's particular frequency bands that can get nulled?
My main listening position did not fare badly, so doing the "real" crawl can wait.

 

[Andysu]

I was curious about this, so I did a walkabout with the sub in its place.
I guess this is a "reverse crawl"? Or more like a chicken walk, as I was trying to keep my ears at "regular listening height".
After a while I started to get it. In some places, very boomy bass, I guess from a strong room mode. In others, fewer or tamer modes, and I could hear the music better.
Massive Attack's "Unfinished Sympathy" on loop, playing only through the sub.

What I had not gotten was all that talk of "nulls". I can hear bass pretty much everywhere. So I guess it's particular frequency bands that can get nulled?
My main listening position did not fare badly, so doing the "real" crawl can wait.

here is easier way of doing it with seeing the results on RTA

video is rather long but skip to 5min 17sec and 7min 0sec is where i show how to make subwoofer life easier

 

[jsilvela]

I did one more experiment today: instead of preamp + Hypex NCORE amp, with the sub connected via RCA splitter from the amp, I tried connecting to a DENON AVR to try out bass management. And then try Audyssey EQ.

Separates with no EQ:

DENON AVR with Bass Mangement, configured manually, Xover at 80hz, levels matched with pink noise:

Then, DENON with the sub connected via the LFE input, letting Audyssey do its thing.
The first song I played, I thought something was truly bad. Overblown bass. Could identify 100% with a blind test. Heck, even with a deaf test.
The REW sweep made me laugh:

Finally, I thought, one try with the DENON and Audissey, but using the Low-Level RCA input on the sub, with my existing settings for Phase and Crossover frequency.
Better. Not as funny though:

 

[sigbergaudio]

@jsilvela That looked weird. Audyssey should definitely be able to bring down the peak at ~37hz. Did you do the Audyssey calibration process properly? Also, is Dynamic EQ enabled or disabled?

 

[jsilvela]

@jsilvela That looked weird. Audyssey should definitely be able to bring down the peak at ~37hz. Did you do the Audyssey calibration process properly? Also, is Dynamic EQ enabled or disabled?

Well I may have done something wrong, but the 37hz bump is there across two calibrations, and with dynamic EQ enabled.
Huh, so it is is surprising. I'll say that the Denon I have is an X1500H, so probably low-end...

 

[jsilvela]

@jsilvela That looked weird. Audyssey should definitely be able to bring down the peak at ~37hz. Did you do the Audyssey calibration process properly? Also, is Dynamic EQ enabled or disabled?

BTW this is what I got the other day with preamp + Hypex amp, and with SoundSource using an EQ profile generated with REW.
I believe the curve should be a bit higher in LF to get the X curve. I try to get better another dayl
Still, my manual effort was way better than Audissey, and the EQ by the way had I think 3 PEQ points only

 

[sigbergaudio]

Well I may have done something wrong, but the 37hz bump is there across two calibrations, and with dynamic EQ enabled.
Huh, so it is is surprising. I'll say that the Denon I have is an X1500H, so probably low-end...

Hm. I wrote an article a while back on the topic, perhaps worth reading through: https://www.sigbergaudio.no/blogs/news/audyssey-room-calibration-common-mistakes

Potential mistakes could have been spreading the microphone measurements too far apart (distance), and possible also having it too close to the back wall, you should be at least 50cm away from it. Have you tried measuring across the different Audyssey measurement points to see if that bump is present in all?

WIth regards to Dynamic EQ, that will boost the bass, perhaps try turning that off or at least reducing it's level (can be done with the feature called reference level or something, it defaults to 0dB but can be turned down to -5dB or -10dB to reduce the bass. Your final graph actually looks quite decent if you got rid of the bump.

 

[sigbergaudio]

BTW this is what I got the other day with preamp + Hypex amp, and with SoundSource using an EQ profile generated with REW.
I believe the curve should be a bit higher in LF to get the X curve. I try to get better another dayl
Still, my manual effort was way better than Audissey, and the EQ by the way had I think 3 PEQ points only

View attachment 255292

looks good except too little tilt (need more low end).

 

[jsilvela]

Hm. I wrote an article a while back on the topic, perhaps worth reading through: https://www.sigbergaudio.no/blogs/news/audyssey-room-calibration-common-mistakes

Potential mistakes could have been spreading the microphone measurements too far apart (distance), and possible also having it too close to the back wall, you should be at least 50cm away from it. Have you tried measuring across the different Audyssey measurement points to see if that bump is present in all?

WIth regards to Dynamic EQ, that will boost the bass, perhaps try turning that off or at least reducing it's level (can be done with the feature called reference level or something, it defaults to 0dB but can be turned down to -5dB or -10dB to reduce the bass. Your final graph actually looks quite decent if you got rid of the bump.

Thank you! That's very useful. I will retry another day.
I was mindful to move the mic less than 60cm between measurements. Just 3 positions, fairly close.
And all plenty more than 50cm away from walls.

 

[sigbergaudio]

Thank you! That's very useful. I will retry another day.
I was mindful to move the mic less than 60cm between measurements. Just 3 positions, fairly close.
And all plenty more than 50cm away from walls.

Hm. Weird.

 

[Sancus]

Denons that don't have MultEQ XT32, which starts at 3000 series iirc, have really poor filter resolution in low bass and don't actually perform that well. There are threads about it around here.

 

[Vacceo]

And by implication, also increase the extension, because it lifts the lowest frequencies to a relevant level. This will, of course, apply more to sealed subs with their shallower downward slope than to ported subs. My own not very powerful sealed 2x8 inch B&W PV1d produces serious level to some 13 Hz when located in the corner, and in that same corner my even smaller sealed 8 inch Kef Kube8b manages more or less flat output down to 25 Hz.

That is something I have noticed on my ancient KEF PSW2500's. If I play a 15hz wave, I notice the vibration when I place them close to a corner.

 

[jsilvela]

Denons that don't have MultEQ XT32, which starts at 3000 series iirc, have really poor filter resolution in low bass and don't actually perform that well. There are threads about it around here.

Yep I've seen other people post janky LF curves from Audissey at ASR.
Just checked and the X1700H has MultiEQ XT32. (I have the X1500H, without)
Haha, always so many decisions.
Considering how much better I've done rolling my own EQ with SoundSource on the mac, I'm thinking of getting a miniDSP though.
But I want to repeat / retry with what I have

 

[Sancus]

Yep I've seen other people post janky LF curves from Audissey at ASR.
Just checked and the X1700H has MultiEQ XT32. (I have the X1500H, without)
Haha, always so many decisions.
Considering how much better I've done rolling my own EQ with SoundSource on the mac, I'm thinking of getting a miniDSP though.
But I want to repeat / retry with what I have

No, I don't think so. Looking at Denon's website, under "Sound Enhancements" the X1700H and X2700H both have "MultEQ XT". The 3700H has "MultEQ XT32". Same for the X800Hs.

If you have a way to apply PEQs generated in REW though then that's also fine.

looks good except too little tilt (need more low end).

It's actually such a pain in the ass to create a constant tilt with Audyssey because of the way you have to adjust the subwoofer level manually. Audyssey doesn't have a global target curve in the app, it has per-channel target curves and the subwoofer one won't allow you to boost it(it basically treats the highest level on your curve as 0dB).

 

[bodhi]

It's actually such a pain in the ass to create a constant tilt with Audyssey because of the way you have to adjust the subwoofer level manually. Audyssey doesn't have a global target curve in the app, it has per-channel target curves and the subwoofer one won't allow you to boost it(it basically treats the highest level on your curve as 0dB).

Manual boost for lower frequencies does not work well with Dynamic EQ. At least for me the bass is boosted way too much.

 

[killdozzer]

I think the video below explains the problems with subs in the corner pretty well. Also, in the last 4 rooms I've set up subs in, I've gotten better native room response from my subs when placed along the wall away from the corners. Too much "room sound" would be the primary problem I have with corner subs.

Oh no! Not this guy again... This guy is a total douche. "Your subs need to move up the walls as well and by sheer coincidence, I'm manufacturing just what you need." "Oh, and btw, don't get DSP, the less EQ you do the more of my sh... gets sold."