Fixing crazy upper bass response?

Y

yepimonfire

Audioholic Samurai
I have a wildly varying response from about 80hz-200hz as you can see below in the pics.


This is an issue ONLY with the front left and right, the center measures fairly okay, as do the surround, and moving the listening position doesn’t fix it either leading me to think it might be a speaker boundary interaction problem. Here is the center measurement


The front left and right are crossed over at 60hz. I tried using a crossover at 80hz but that only changes the crazy shape of the graph, and does nothing to solve the problem. The fronts are 2’ from the front and side walls in a 20x12 room, about 8’ apart with the mlp 9’ away.

Any idea what might be going on here and how can I fix it?


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highfigh

highfigh

Seriously, I have no life.
I have a wildly varying response from about 80hz-200hz as you can see below in the pics.


This is an issue ONLY with the front left and right, the center measures fairly okay, as do the surround, and moving the listening position doesn’t fix it either leading me to think it might be a speaker boundary interaction problem. Here is the center measurement


The front left and right are crossed over at 60hz. I tried using a crossover at 80hz but that only changes the crazy shape of the graph, and does nothing to solve the problem. The fronts are 2’ from the front and side walls in a 20x12 room, about 8’ apart with the mlp 9’ away.

Any idea what might be going on here and how can I fix it?


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Turn off the sub and see if this changes. If it does, you may need to move the subwoofer.

I ran REW when I decided that I needed to change the position of my speakers and watched it as I moved each one after marking the original placement. It really saved a lot of time- I did listen after making any changes and found that small increments helped a lot. I also changed the toe-in.

You may find that this is caused by the energy interacting with the room's corners- I put absorptive panels in the corners of my room but you may need to use something else (WAF), so try that, too. My bass response problems are gone and it's much more enjoyable.
 
TheWarrior

TheWarrior

Audioholic Ninja
What's going on here is what goes on in any domestic space where sound is being reproduced. The interaction of sound waves reflecting off parallel boundaries creates standing waves that determine what you can hear, when and where.

1131 fps/ 20 feet = 56 hz
1131 fps/ 12 feet = 94 hz

Room construction can vary the actual modal frequency from predicted. I seem to remember you said there were large closets in this room?

Looks like those two modes are showing up at 50 hz peak, followed by null just below 90 hz.

1131/9 feet = 125 hz. Thats the distance between front wall to mic, correct? That means the 125 hz null is simply a cancellation caused by the mic placement.

More information like room set up, orientation(pics?) and equipment used, and anything else setup-wise thats already been done would be needed to recommend a solution.
 
TLS Guy

TLS Guy

Seriously, I have no life.
What's going on here is what goes on in any domestic space where sound is being reproduced. The interaction of sound waves reflecting off parallel boundaries creates standing waves that determine what you can hear, when and where.

1131 fps/ 20 feet = 56 hz
1131 fps/ 12 feet = 94 hz

Room construction can vary the actual modal frequency from predicted. I seem to remember you said there were large closets in this room?

Looks like those two modes are showing up at 50 hz peak, followed by null just below 90 hz.

1131/9 feet = 125 hz. Thats the distance between front wall to mic, correct? That means the 125 hz null is simply a cancellation caused by the mic placement.

More information like room set up, orientation(pics?) and equipment used, and anything else setup-wise thats already been done would be needed to recommend a solution.
I absolutely agree. People worry too much about this sort of thing. Those peaks and valleys are very narrow on the whole. He needs to use some smoothing on his traces. The smoothed response is actually much closer to what is perceived.

What is not shown is that smoothed response in relation to the response in the 500 to 1K range.

And once again those traces are not in the upper bass range, but still on the lower bass range.

It is definitely bass up to 600 Hz or so, and you can argue between 600 and 1K.

From what I have found because of BSE the real power required is between 70 Hz and 600 Hz. However there is lots of power demands right out to 2.5 KHz. That is why I don't like crossing over tweeters below that point.

The myth that subs off lead receivers is bunk. They do however limit main woofer excursion. However there is still a lot of cone excursion required in the 500 to 600 Hz range. X-max of many if not all bookshelves is easily and often exceeded in this range.

It is not true a bookshelf and subs is as competent a system as one with good larger speakers. It is not even close.
 
ATLAudio

ATLAudio

Senior Audioholic
@yepimonfire

First things first, please post your REW sub graphs to the typically agreed upon standard which I think is 45dB- 105dB, and 15-200 hz. It appears this is without smoothing, so you have that right, so that’s a good thing.

Also do you have any Room EQ running (I’m guessing no)? Audyssey or similar will usually give proper distances for subwoofers to smooth these out, but not always. You can tweak your subwoofer measurement distances on the AVR 1-3 feet from calibration to smooth them out. If you have multiple subs, tweak measurements for one first, and if that doesn’t work, try tweaking both the same direction. Finally rerun audyssey again with a 1’ area mic placement.

If you’re even more curious, run a graph of your speakers at full range, and another graph of just your sub(s) at highest crossover, usually 250 hz. What you’ll see here is potential dips with the sub and speakers at the same 85dB and 105dB, or perhaps they will compliment, with the speakers not dipping, and the sub dipping, which is a good thing. If you have latitude to physically move speakers and sub this will show you that impact in better isolation. You can further run sweeps a foot or two ahead of or behind your MLP, if you have latitude to change your listening spot.
 
ATLAudio

ATLAudio

Senior Audioholic
@TLS Guy

As @WaynePflughaupt has mentioned before it's best to analyze subwoofer response with no smoothing.

"cone excursion required in the 500 to 600 Hz range. X-max of many if not all bookshelves is easily and often exceeded in this range."

That completely depends on the bookshelf, and listening distance. Generally a bookshelf with a 6" + driver will handle it just fine for deafening volume. Most 5.25 will be suitable for THX reference level listening as well.

"It is not true a bookshelf and subs is as competent a system as one with good larger speakers. It is not even close."

Completely disagree. Assuming same sub and similar craftsmanship and component sophistication of bookshelf and floor standing unit.
 
Pogre

Pogre

Audioholic Slumlord
I got some pretty good results playing with the distance settings also when I was tweaking my subwoofers in.
 
Y

yepimonfire

Audioholic Samurai
Just measuring the bookshelves on direct mode (no delay etc) shows the same same thing. I’m probably being nit picky about it, as some extra research shows it doesn’t matter where you put speakers or seats, at some point there is going to be wild peaks and dips below the transition frequency. Am I correct in this?

Moved the seat back 1.5’, ignoring fr graphs and just cycling through test tones, I found an offensive null at my former seating position centered at 80hz, moving the seat back reduced this and while it’s obviously not flat, the dips aren’t as severe, and at less “offensive” frequencies.





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ATLAudio

ATLAudio

Senior Audioholic
Just measuring the bookshelves on direct mode (no delay etc) shows the same same thing. I’m probably being nit picky about it, as some extra research shows it doesn’t matter where you put speakers or seats, at some point there is going to be wild peaks and dips below the transition frequency. Am I correct in this?

Moved the seat back 1.5’, ignoring fr graphs and just cycling through test tones, I found an offensive null at my former seating position centered at 80hz, moving the seat back reduced this and while it’s obviously not flat, the dips aren’t as severe, and at less “offensive” frequencies.
Yes, you generally will have modal peaks and dips no matter what, we just want to avoid the wild aggressive ones as best we can. Moving the seat back seems to be a step in that direction. Next you can set the speakers as small, with subs, run Audyssey if applicable, and see how it looks. If you see wild peaks or dips, adjust the subwoofer distance on the avr to get the smoothest presentation possible.
 
Y

yepimonfire

Audioholic Samurai
I absolutely agree. People worry too much about this sort of thing. Those peaks and valleys are very narrow on the whole. He needs to use some smoothing on his traces. The smoothed response is actually much closer to what is perceived.

What is not shown is that smoothed response in relation to the response in the 500 to 1K range.

And once again those traces are not in the upper bass range, but still on the lower bass range.

It is definitely bass up to 600 Hz or so, and you can argue between 600 and 1K.

From what I have found because of BSE the real power required is between 70 Hz and 600 Hz. However there is lots of power demands right out to 2.5 KHz. That is why I don't like crossing over tweeters below that point.

The myth that subs off lead receivers is bunk. They do however limit main woofer excursion. However there is still a lot of cone excursion required in the 500 to 600 Hz range. X-max of many if not all bookshelves is easily and often exceeded in this range.

It is not true a bookshelf and subs is as competent a system as one with good larger speakers. It is not even close.
From a musical perspective, the sub bass range extends from 20hz-60hz, bass is 60hz-256hz, lower midrange is 256hz-500hz, midrange 500hz-2khz, upper mid from 2khz-4khz, presence 4khz-6khz, and brilliance 6khz-20khz, don’t see why audio shouldn’t use the same ranges when describing where something lies.

You won’t get any disagreement from me on whether or not a sub reduces power requirements, it often doesn’t, especially with ported speakers. Woofers are their most efficient at (and slightly above and below) the resonant frequency, and port tuning frequency, which often lie close together. A bookshelf speaker tuned to 50hz could easily meet or exceed the output of a sub tuned to 20hz, at the tuning frequency, using a ton less power as well (assuming the port is designed well enough to avoid noise). A sub sat system with respective tuning frequencies of 50hz and 25hz crosses over at 50hz is much more efficient than a single sub playing up to 80hz, especially when you consider massive amounts of efficiency is traded for extension is subwoofer drivers.

Do you mean power or xmax at 500hz? A 5” woofer with a typical 6mm of xmax could mechanically reproduce 500hz at 130dB @1m, thermally, we all know it would fail long before that, since impedance generally is the lowest from about 80hz-1khz. At 4ohms using a woofer rated at 87dB 2.8v, (2w), you’re looking at about 105dB @ 100w/1m, which is really pushing the limits of most woofers.

With direct radiating tweeters, an xover point of 2.5khz is definitely a compromise that places a lot of stress on tweeters, much in the same way sub bass frequencies stress smaller woofers. Almost all direct radiating speakers tend to start breaking up at high spl levels because of this, yet a higher xover point generally runs the risk of operating a woofer into its breakup mode, along with mismatched dispersion causing lobing and beaming, with poor off axis response. The best solutions, are either three way speaker made 4 way with a sub, allowing a tweeter to be crossed over above 3khz, or horn loading, when done correctly xmax at low frequencies is significantly reduced, the speakers in my setup are crossed over at 1500hz, using a 1” titanium dome tweeter, yet there is no breakup even at very high volumes levels because of horn loading, exceeding the output capabilities of most direct radiating tweeters crossed over at 2.5khz, with lower distortion to boot.

As far as whether or not a sub sat system is more capable than two large full range speakers, that really depends. A bookshelf using one 6.5” woofer with a f3 of 50hz, crossed over to a sub with an f3 of 30hz is going to be more capable than a floor standers using two 6.5” woofer tuned to 30hz with no sub, especially considering it’s likely the same tweeter is used, with no more output capabilities. A three way system using a 15” woofer, 5” midrange, and tweeter crossed over higher above 4khz would definitely outperform it. In modern consumer speakers, the only thing you get with most floor standing upgrades are deeper bass and more bass/midrange headroom. No two way direct radiating speaker with small cabinets/woofers and puny tweeters will ever truly be capable of high spl and low distortion. Cinemas don’t use these crippled designs and neither does pro audio, for good reason.


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