Causes of wolf tones in the midrange?

[Boomzilla]

In the past, and on some material, midrange vocal tones seemed to be blurred. At first, I thought that it might be a recording or ripping shortcoming, but as the resolution of my system has increased, the blurring is beginning to come more into focus. On some midrange frequencies (usually higher register male voices to mid-register female voices in particular), there seems to be a second voice singing along with the fundamental. I believe that in audio parlance, this is typically called a "wolf tone."

garbulky (whose ears are better than mine) has consistently claimed that this is a room echo and that additional absorbers will alleviate it. I tried to resolve the issue with diffusers behind the listening position and by moving the listening couch away from the back wall by a couple of feet. This helped, but the wolf-tone is still there.

It's time to deal with this issue. The first thing that comes to mind is to remove the diffusers from behind the listening couch and substitute the thickest absorbers that I can find (4 to 6 inch thickness?). Is this a reasonable first step?

The second thing that comes to mind is to add a suspended ceiling diffuser or diffusers made of acoustical tile. I'd have to build this and hang it myself.

The wall behind the speakers already has four 4x2 foot x 2-inch absorbers with a 65" flat-screen hung on the wall between the speakers. The third thing that I though might help would be to suspend curtains that could be opened and closed in front of the TV.

The side walls are already at least seven feet from the speakers and already have 2x2 foot x 4-inch absorbers at the first-reflection points.

At the moment, floor is hard and the 9-foot ceiling is sheet-rock. I can't raise the ceiling because there is a second floor above. There is an 8x10 foot rug on the floor.

ROOM SIZE = 23.5 x 16 feet x 9 tall thus, Volume = 3,384 cubic feet and all 4 corners are vented to other areas of the house. Additionally, the speakers are on the long wall, about 2 feet from the wall behind them and the listening couch is about 2 feet from the wall behind it meaning that the plane of the speakers (ignoring placement for width) is about 12 feet from the listening couch.

Any suggestions on banishing the wolf-tone are appreciated.

Boomzilla

PS - The AcoustiMac calculator ( www.acoustimac.com/room-calculator?limit=all&gclid=CjwKCAjwrvv3BRAJEiwAhwOdM4sjUHrBRDQ1yi2Rq4_BcF6dcjr-uBoXMaQXyyxmP6amhmcgzncvxBoCo_AQAvD_BwE ) recommends between 87 and 121 square feet of absorbers, but to get that much coverage, I'd HAVE to make my own. Their calculator is also mute on WHERE those absorbers should be installed.

[KeithL]

I'm not sure exactly what you're describing...

But, if it's what I think it is, it may indeed be room reverberance, and, if so, some strategically placed absorbers should indeed tame it.

Assuming you have a very live room...

Echoes that arrive very soon after the main sound make the room sound more live but aren't heard as distinct sounds...

And echoes that arrive after a certain longer time are easily heard as echoes...

And our brains are very good at differentiating between those two extremes.

However our brains have some difficulty with echoes that fall between those extremes.

What you're talking about would be technically described as "having an excessively long RT60 in the upper midrange".

"Reverberance Time" is a fancy way of saying that you're graphing how long it takes sound to die down by 60 dB at various frequencies.

(I see that REW can do that measurement... although I've never used it for that measurement.)

What happens is that, if the RT60 is too long, certain frequency ranges tend to build up over a few seconds if excited by a steady source.

So, when you get something like a voice, which delivers a long sound rather than a transient, it tends to build up into a drone or howl...

In addition, since each echo arrives at a slightly different time, the first arrival times our brains use to determine source location are blurred together.

(You're hearing the initial sound followed by a steady stream of small echoes that blur together and are collectively too loud.)

If you use an analogy of sound to light...

A room will be very unpleasant if it's lined with too many mirrors...

And diffusers are the equivalent of crumpled or frosted aluminum foil... and may smooth out the glare...

But, since sound can take several seconds to die down, it can also build up over time into a sort of "sonic glare"...

(And, while diffusers can soften the harsh reflections, they don't do much of anything to prevent such a build-up.)

Audibly, if you play a very short burst of pink noise, it will sound normal...

But, if you play a steady pink noise tone, for several seconds, it will seem to change over the first second or two...

It's difficult to see on an analyzer because the display takes a few seconds to settle... but you can often hear it with pink noise.

Note that this can happen in your listening room... or can be there in the original recording... or a little of both.

And, of course, since it's only obvious with certain types of sounds, in certain frequency ranges, you may only notice it with some recordings.

And, if it is present in a specific recording, and your speakers have a bump in their response in that range, that will also tend to make it more obvious.

(And, if the original recording venue has an uneven T60, with a lump somewhere, you can't easily fix it in the recording studio afterwards.)

If you want to figure out if it's your room and system that's responsible then forget all the calculations...

Just listen to those same recordings with a good pair of headphones...

(That way you can compare the way it sounds "with and without the room".)

And, yes, for those who may want to ask....

You can artificially INCREASE RT60 - by adding artificial reverberance in certain frequency ranges.

However, the only way to DECREASE RT60 is by actually adding physical absorption to the room.

There is one more thing worth considering - especially if you only notice this with certain recordings.

Many modern multi-track recordings are recorded in a studio - with each track recorded separately.

And, in many cases, each track is recorded in a close approximation to an anechoic chamber.

And, to put it bluntly, the "room ambience" you think you hear may have come from a hardware black box or a software program.

This leaves open the possibility that it may simply not sound very natural...

Or that the reverberance in different tracks, or between the voice and the instruments in the same track, may not match...

Or that what you're hearing is partially due to the side effects of using a lot of EQ to correct something else...

Jul 3, 2020 22:22:41 GMT -5 Boomzilla said:

In the past, and on some material, midrange vocal tones seemed to be blurred. At first, I thought that it might be a recording or ripping shortcoming, but as the resolution of my system has increased, the blurring is beginning to come more into focus. On some midrange frequencies (usually higher register male voices to mid-register female voices in particular), there seems to be a second voice singing along with the fundamental. I believe that in audio parlance, this is typically called a "wolf tone."

garbulky (whose ears are better than mine) has consistently claimed that this is a room echo and that additional absorbers will alleviate it. I tried to resolve the issue with diffusers behind the listening position and by moving the listening couch away from the back wall by a couple of feet. This helped, but the wolf-tone is still there.

It's time to deal with this issue. The first thing that comes to mind is to remove the diffusers from behind the listening couch and substitute the thickest absorbers that I can find (4 to 6 inch thickness?). Is this a reasonable first step?

The second thing that comes to mind is to add a suspended ceiling diffuser or diffusers made of acoustical tile. I'd have to build this and hang it myself.

The wall behind the speakers already has four 4x2 foot x 2-inch absorbers with a 65" flat-screen hung on the wall between the speakers. The third thing that I though might help would be to suspend curtains that could be opened and closed in front of the TV.

The side walls are already at least seven feet from the speakers and already have 2x2 foot x 4-inch absorbers at the first-reflection points.

At the moment, floor is hard and the 9-foot ceiling is sheet-rock. I can't raise the ceiling because there is a second floor above. There is an 8x10 foot rug on the floor.

ROOM SIZE = 23.5 x 16 feet x 9 tall thus, Volume = 3,384 cubic feet and all 4 corners are vented to other areas of the house. Additionally, the speakers are on the long wall, about 2 feet from the wall behind them and the listening couch is about 2 feet from the wall behind it meaning that the plane of the speakers (ignoring placement for width) is about 12 feet from the listening couch.

Any suggestions on banishing the wolf-tone are appreciated.

Boomzilla

PS - The AcoustiMac calculator ( www.acoustimac.com/room-calculator?limit=all&gclid=CjwKCAjwrvv3BRAJEiwAhwOdM4sjUHrBRDQ1yi2Rq4_BcF6dcjr-uBoXMaQXyyxmP6amhmcgzncvxBoCo_AQAvD_BwE ) recommends between 87 and 121 square feet of absorbers, but to get that much coverage, I'd HAVE to make my own. Their calculator is also mute on WHERE those absorbers should be installed.

[Boomzilla]

Jul 3, 2020 23:53:28 GMT -5 KeithL said:

...There is one more thing worth considering - especially if you only notice this with certain recordings. Many modern multi-track recordings are recorded in a studio - with each track recorded separately. And, in many cases, each track is recorded in a close approximation to an anechoic chamber. And, to put it bluntly, the "room ambience" you think you hear may have come from a hardware black box or a software program.
This leaves open the possibility that it may simply not sound very natural...Or that the reverberance in different tracks, or between the voice and the instruments in the same track, may not match...Or that what you're hearing is partially due to the side effects of using a lot of EQ to correct something else...

Although the effect is more audible with certain recordings, it is there with all of them. In the current system, there is no DSP and no equalization. So I'm relatively convinced that the cause IS the room and not the recording or the electronics. And thank you kindly for the explanations - they are appreciated!

Glenn

[DYohn]

Didn't we discuss proper room treatment years ago? Glad to see you are considering it.

[Boomzilla]

I'm slow, but I eventually get there...

This morning, I put the absorbers behind the couch and moved the diffusers to the side walls. Results: This helped, but it didn't totally eliminate the midrange issue. I also note that if the volume is low, the midrange gives me less problems than if I crank it up even a little. I think that this also argues for room echo being the root cause.

So it's absorber time! Next question - where do I put them first? More behind the listening position? Ceiling? Around the higher parts of the walls? My best guess at this time is that the wall behind the listening seat is the primary place where more absorbers would help (based on getting better results after swapping the diffusers for the absorbers).

Also, are thicker absorbers better? From what I've read, a thinner absorber spaced away from the wall is more effective, generally, than a thicker absorber mounted on the wall itself? Would I do better to hang the absorbers from the ceiling or to mount them to the wall with spacers? Also, do the absorbers even need a frame, or is that for appearance only? And is open cell or closed cell foam a better absorber? I'm thinking of just buying the foam, cutting it into strips of the right length, and dying it.

Once I've covered that wall, what next?

[garbulky]

The problem is that your room is so large that a thick absorber in one location isn't going to fix the problem. That would not work in a smaller room either. You need many more absorbers, not necessarily super thick ones.

[Boomzilla]

What thickness? On what walls? What percentage coverage?

And can the absorbers just be mounted on the walls or should they be suspended with an air gap behind?

I could ask a GIK or some other company to just do a design, but if I need to do a LOT of coverage, and I may, I can't afford to buy commercial absorbers. Going to HAVE to be some DIY in there.

[405x5]

Too many Tacos 🌮 and beers 🍻 in the HT room.....PLENTY of wolf tones going around!

[DYohn]

[Boomzilla]

Here's the crime scene:

[Deleted]

A room will be very unpleasant if it's lined with too many mirrors...

Haven't done this myself but that sounds like a workable way to find reflections? That is, place a cheap WalMart 4 foot tall mirror in front of you speaker tower. From you listening position shoot a laser or flashlight at the mirror and wherever that light reflects/projects upon ...... that area needs an absorber? 

I'd think using multiple mirrors even in the reflected area to find secondary reflections would work too?

There appears to be methods of finding reflections by using mirrors:

"Sit at your listening position as you normally would when listening or mixing. Starting with the left wall, have a friend hold a mirror up against the wall next at your speaker height, then move toward the back of the room. When you can see the reflection of the left speaker in the mirror, mark that spot. That’s your first reflection point. Continue moving down the wall, and when you can see the right speaker, mark that spot. That is your other reflection point. Switch walls and repeat. If you’re dealing with multiple seating locations, repeat this process for each seat." - www.gikacoustics.com/early-reflection-points/

[audiobill]

Have you ever considered placing your speakers on the short wall?

Diffraction from the windows, side speaker reflections go nowhere, 25.5' depth obviates rear treatment.......

[novisnick]

Jul 4, 2020 18:58:12 GMT -5 audiobill said:

Have you ever considered placing your speakers on the short wall?

Diffraction from the windows, side speaker reflections go nowhere, 25.5' depth obviates rear treatment.......

IfI may, rotating the setup would be as near impossible as me moving mine. Sometimes you just have to do what’s completely inappropriate. Homes (most) were not designed with audio in mind. Perhaps hollering through the house to call the children for supper! 

[audiobill]

Sorry, Nick, lost my way!

[garbulky]

All walls and ceiling and most of it . Probably about $2 to 2.5 k worth of absorbers. I know there’s lots of reasons you wouldn’t want to do it. But that’s what it takes. Gik gave you a recommendation some time ago. . Perhaps that’s a good place to start. I don’t think you’ll hear much difference otherwise. You won’t find the diy route aesthetically pleasing or realistic to complete as it’s a good amount of work.

[Boomzilla]

On the recommendation of an audio amigo, I draped a curtain over the 65" TV this evening while listening. About 50% of my echo issue went away!

After consideration, I could place the speakers and listening seat as shown below. But THAT would put the speakers in CLOSE proximity to the side walls AND leave me with a heavy TV in a useless position...

Doing the setup this way, however WOULD eliminate (actually, greatly attenuate) back wall reflections AND it would let me put absorbers on the side walls just in front of the speakers. Whadda ya think?

[Boomzilla]

Jul 4, 2020 19:10:58 GMT -5 audiobill said:

Sorry, Nick, lost my way!

Not...

[novisnick]

Jul 4, 2020 21:37:50 GMT -5 Boomzilla said:

On the recommendation of an audio amigo, I draped a curtain over the 65" TV this evening while listening. About 50% of my echo issue went away!

After consideration, I could place the speakers and listening seat as shown below. But THAT would put the speakers in CLOSE proximity to the side walls AND leave me with a heavy TV in a useless position...

Doing the setup this way, however WOULD eliminate (actually, greatly attenuate) back wall reflections AND it would let me put absorbers on the side walls just in front of the speakers. Whadda ya think?

Thats how I’ve envisioned that room from the start. If you can go this route and not worry about HT for now I truly believe you’ll fall in love all over again with music. Especially if your adding the panels garbulky suggests. 

[KeithL]

If you have a reflective TV screen in front of the seating position...

And a reflective wall behind the seating position...

Then the obvious thing to do is a big absorber behind the seating position.

(To eliminate the two big flat reflective parallel surfaces.)

Since the problem is in the midrange, and probably the upper midrange, you probably don't need any fancy absorbers.

A nice fuzzy rug, hung on a curtain rod like a tapestry, should absorb plenty at those frequencies.

Just get a pretty tapestry rug like this one and hang it from a heavy curtain rod...

(They come in a variety of sizes, including 4x6 and 5x9, and a wide variety of patterns and colors.)

[audiobill]

Jul 4, 2020 21:37:50 GMT -5 Boomzilla said:

On the recommendation of an audio amigo, I draped a curtain over the 65" TV this evening while listening. About 50% of my echo issue went away!

After consideration, I could place the speakers and listening seat as shown below. But THAT would put the speakers in CLOSE proximity to the side walls AND leave me with a heavy TV in a useless position...

Doing the setup this way, however WOULD eliminate (actually, greatly attenuate) back wall reflections AND it would let me put absorbers on the side walls just in front of the speakers. Whadda ya think?

Well worth trying, IMO - and don't worry so much about the side wall reflections, you can damp them easily.  And, can you reverse the speaker and couch positions?


Don't let Gar spend your money!!!