Acoustic treatment and room measurement

[Eppie]

In your situation I would take highfigh's approach, as you already have the panels. Add them one at a time and maybe again in pairs, taking measurements each time. Take a systematic approach to see which setup yields the best results. A whole room solution requires professional gear and expertise that we do not have.

 

[TLS Guy]

In your situation I would take highfigh's approach, as you already have the panels. Add them one at a time and maybe again in pairs, taking measurements each time. Take a systematic approach to see which setup yields the best results. A whole room solution requires professional gear and expertise that we do not have.

That is a fairly big room, and those speakers have those miserable mids crossed at 800 Hz. There is a huge power demand in the range of those mids, and as he places acoustic treatments it is adsorbing sound and increasing power demands.

This is a huge problem for three way speakers in general. The optimal mid range driver should cover the whole speech discrimination band. That is 400/500 Hz to 4 KHz/5 KHz. The only way you can get a VC to handle power in that range is with a dome design. These are far and few between and expensive, as they are hard to manufacture.

When I spent an interesting afternoon with Billy Woodman of ATC at his factory at Stroud Gloucestershire, he took me through the whole assembly of their famous ATC mid domes. ATC domes on only available to ATC.

The justly famous Dynaudio D 76 has been unavailable for 19 years now.

So that leaves Volt as the only other source of high powered wide band dome drivers. These are now available in the US from Madisound. These are first class units available in a range of impedances.

Here is a picture of a Dynaudio D76 dome in one of my family room speakers. It is a 4.5" dome and the VC also has a diameter of 4.5" and so there is excellent heat dispersion. Crossover to the dome is 400 Hz and from the dome 4 KHz. Those are high spl. speakers.

Those speakers are B4 reflex, with an F3 if 31 Hz.

I have been toying with the idea of a three way with B139 now available again from Falcon acoustics and the Volt dome with a good 3/4" dome tweeter. This would be a TL. The B139 has absolutely perfect T/S parameters for TL loading and you get an f3 around 27 Hz and second order and not fourth order roll off.

This would be like the classic TDL designs of John Wright.

 

[highfigh]

It didn't because room treatments have a 50/50 chance of improving or making it worse and not even that good.

Where did you get that bogus idea about your room shape? If you re going to do that then you should have sloped the walls starting near the speakers, not that abrupt transition.

An even bigger mistake was picking those speakers. We have been round the houses with those before. The 3" midrange drivers are far too small for the power they have to handle. They cross at 800 Hz, and there is a huge amount of power above 800 hz to 2,700 Hz. So a big reason I suspect for your poor result is that the acoustic treatments absorbed a lot of sound that would have been reflected and stressed the speakers even more.

You have to choose speakers with huge care, as there are far more lousy ones than good ones.

If the material choices, thickness & area covered, distance to the walls/ceiling and placement are wrong, success is far from guaranteed but acoustics is a long-studied branch of science and some people are pretty good at implementing the theories.

Your favorite classical music venues- are they treated? Even if nothing is visible, permanent seating is made to be as absorptive as a human body, so attendance doesn't ruin the sound.

One problem with acoustical treatments is definitely the appearance, though.

 

[highfigh]

That is a fairly big room, and those speakers have those miserable mids crossed at 800 Hz. There is a huge power demand in the range of those mids, and as he places acoustic treatments it is adsorbing sound and increasing power demands.

This is a huge problem for three way speakers in general. The optimal mid range driver should cover the whole speech discrimination band. That is 400/500 Hz to 4 KHz/5 KHz. The only way you can get a VC to handle power in that range is with a dome design. These are far and few between and expensive, as they are hard to manufacture.

When I spent an interesting afternoon with Billy Woodman of ATC at his factory at Stroud Gloucestershire, he took me through the whole assembly of their famous ATC mid domes. ATC domes on only available to ATC.

The justly famous Dynaudio D 76 has been unavailable for 19 years now.

So that leaves Volt as the only other source of high powered wide band dome drivers. These are now available in the US from Madisound. These are first class units available in a range of impedances.

Here is a picture of a Dynaudio D76 dome in one of my family room speakers. It is a 4.5" dome and the VC also has a diameter of 4.5" and so there is excellent heat dispersion. Crossover to the dome is 400 Hz and from the dome 4 KHz. Those are high spl. speakers.

Those speakers are B4 reflex, with an F3 if 31 Hz.

I have been toying with the idea of a three way with B139 now available again from Falcon acoustics and the Volt dome with a good 3/4" dome tweeter. This would be a TL. The B139 has absolutely perfect T/S parameters for TL loading and you get an f3 around 27 Hz and second order and not fourth order roll off.

This would be like the classic TDL designs of John Wright.

Do you know why KEF began using the oval woofers? I would guess you do.

 

[TLS Guy]

Do you know why KEF began using the oval woofers? I would guess you do.

For the obvious reason, that it allows for a bigger woofer and still keep the cabinet narrow. Obvious really. Modern designers are so obtuse compared to my mentors.

 

[TLS Guy]

If the material choices, thickness & area covered, distance to the walls/ceiling and placement are wrong, success is far from guaranteed but acoustics is a long-studied branch of science and some people are pretty good at implementing the theories.

Your favorite classical music venues- are they treated? Even if nothing is visible, permanent seating is made to be as absorptive as a human body, so attendance doesn't ruin the sound.

One problem with acoustical treatments is definitely the appearance, though.

My favorite ones NO. Acoustic treatments are to make the best of a bad job, when things have gone adrift.

Detroit Symphony Hall sounds absolutely marvelous. It is an old "Shoe Box" Hall with original plaster and sounds really good.

Orchestra Hall in Minneapolis is pretty good, and has irregular "box" like structures at the front to break up reflections. The Ordway in St. Paul is an absolute dog no matter what they do with it.

The Royal Albert Hall is a circular domed building with a pronounced echo. Sir Edward Elgar famously said of it: - "It is the only place where I can hear my music twice in an evening!" The BBC hung a bunch of "flying saucers" from the dome, which has been surprisingly successful. The Royal Festival Hall in the South Bank has always been a dog. There have been numerous attempts to correct it, including changing its dimensions, but it has always been awful. It is now pretty much abandoned as a concert venue.

In general older halls built of older materials and having a dominant length dimension are definitely at the top of the pack as a rule.

As far as my rooms, the one I had at the OP as a kid was really good. It was a long room and essentially an attic space with the sloping roof lines.

In Canada I had a pretty good room, it had a dominant dimension.

Likewise my Grand Forks room was fair to good, but had a passage way off the back leading to the stairway up the main floor, and so had significant bass leakage.

At the lake it was good, but you had to be careful with the bass, due to it not being quite long enough.
The basement family room was very good, and you never would have guessed it would have been. It defied all rules known about good acoustics. There was a lot of glass window facing the speakers, and the room was L-shaped. It had a missive echo. Despite all that it sounded absolutely marvelous. My late friend and colleague Phil was astounded how good the speakers sounded down there. In the family room here it is good, but not like that other room was. Looking at the two, everyone without hearing it, would have picked the wrong room as best.

The AV room here is a very good room indeed. The dimension ratios are ideal and it has 9' ceilings. The only acoustic treatment is the sheving at the rear. This room did require a significant BSC elevation to all the speakers compared to the lake home.

So acoustics are to a large extent actually unpredictable in my view and the results frequently unexpected both good and adverse. I know one thing, you will never turn a bad space into a really good space.

 

[highfigh]

My favorite ones NO. Acoustic treatments are to make the best of a bad job, when things have gone adrift.

Detroit Symphony Hall sounds absolutely marvelous. It is an old "Shoe Box" Hall with original plaster and sounds really good.

Orchestra Hall in Minneapolis is pretty good, and has irregular "box" like structures at the front to break up reflections. The Ordway in St. Paul is an absolute dog no matter what they do with it.

The Royal Albert Hall is a circular domed building with a pronounced echo. Sir Edward Elgar famously said of it: - "It is the only place where I can hear my music twice in an evening!" The BBC hung a bunch of "flying saucers" from the dome, which has been surprisingly successful. The Royal Festival Hall in the South Bank has always been a dog. There have been numerous attempts to correct it, including changing its dimensions, but it has always been awful. It is now pretty much abandoned as a concert venue.

In general older halls built of older materials and having a dominant length dimension are definitely at the top of the pack as a rule.

As far as my rooms, the one I had at the OP as a kid was really good. It was a long room and essentially an attic space with the sloping roof lines.

In Canada I had a pretty good room, it had a dominant dimension.

Likewise my Grand Forks room was fair to good, but had a passage way off the back leading to the stairway up the main floor, and so had significant bass leakage.

At the lake it was good, but you had to be careful with the bass, due to it not being quite long enough.
The basement family room was very good, and you never would have guessed it would have been. It defied all rules known about good acoustics. There was a lot of glass window facing the speakers, and the room was L-shaped. It had a missive echo. Despite all that it sounded absolutely marvelous. My late friend and colleague Phil was astounded how good the speakers sounded down there. In the family room here it is good, but not like that other room was. Looking at the two, everyone without hearing it, would have picked the wrong room as best.

The AV room here is a very good room indeed. The dimension ratios are ideal and it has 9' ceilings. The only acoustic treatment is the sheving at the rear. This room did require a significant BSC elevation to all the speakers compared to the lake home.

So acoustics are to a large extent actually unpredictable in my view and the results frequently unexpected both good and adverse. I know one thing, you will never turn a bad space into a really good space.

Ever see the project cost for a new hall? Do you want to try to buld it with great acoustics without bankrupting the project? The great halls were often built by the government in one way or another- they wanted it done.

It's not unpredictable- it's easy to find the NRC of a material, which is then used to find the amount needed, based on models and software. Location, area, thickness, shape- all can be selected.

Domes are definitely a problem- the location of the sound affects the positions where the sound is focused, or where it was scattered. It's bad if the dome is circular, worse if ellyptical- we have one in Milwaukee- I went to see Jeff Beck at that venue and they must have use some kind of delay that can produce anti-phase sound at a specific time interval because in one song, there are three drum beats that aren't masked by the other instruments and the first thing I noticed was that there was no echo. My friend asked why my mouth was open and I told him, but he didn't know the song well enough to notice.

This book is ini its 7th Edition- mine is 1st edition, so I don't know what they added, but I'm sure it's a substantial amount of information-

Master Handbook of Acoustics

Practical Instruction on the Art and Science of Acoustic Design and Architecture Build your own acoustic environments such as recording studios, control rooms, and home listening rooms with expert insights from two engineering professionals. Fully expanded to cover the latest methods and...

books.google.com

 

[highfigh]

For the obvious reason, that it allows for a bigger woofer and still keep the cabinet narrow. Obvious really. Modern designers are so obtuse compared to my mentors.

Apparently, the Crown imposed a tax on round woofers larger than a specific size and this was the way they avoided it. I was told by a friend, who's a regional sales manager for KEF.

 

[Eppie]

That is a fairly big room, and those speakers have those miserable mids crossed at 800 Hz. There is a huge power demand in the range of those mids, and as he places acoustic treatments it is adsorbing sound and increasing power demands.

This is a huge problem for three way speakers in general. The optimal mid range driver should cover the whole speech discrimination band. That is 400/500 Hz to 4 KHz/5 KHz. The only way you can get a VC to handle power in that range is with a dome design. These are far and few between and expensive, as they are hard to manufacture.

When I spent an interesting afternoon with Billy Woodman of ATC at his factory at Stroud Gloucestershire, he took me through the whole assembly of their famous ATC mid domes. ATC domes on only available to ATC.

The justly famous Dynaudio D 76 has been unavailable for 19 years now.

So that leaves Volt as the only other source of high powered wide band dome drivers. These are now available in the US from Madisound. These are first class units available in a range of impedances.

Here is a picture of a Dynaudio D76 dome in one of my family room speakers. It is a 4.5" dome and the VC also has a diameter of 4.5" and so there is excellent heat dispersion. Crossover to the dome is 400 Hz and from the dome 4 KHz. Those are high spl. speakers.

Those speakers are B4 reflex, with an F3 if 31 Hz.

I have been toying with the idea of a three way with B139 now available again from Falcon acoustics and the Volt dome with a good 3/4" dome tweeter. This would be a TL. The B139 has absolutely perfect T/S parameters for TL loading and you get an f3 around 27 Hz and second order and not fourth order roll off.

This would be like the classic TDL designs of John Wright.

A little off topic, but I wish I was retiring sooner. I would love to try and build a speaker like that but time does not currently permit that. I have yet to build the BMR kit that I got from Swerd and that will take priority. If you develop a speaker along those principals, I would be interested in getting the plans and design specs. Good topic for another thread.

The op's Monitor Audio Silver are generally considered a good speaker but I auditioned the Monitor Audio Gold at a hi-fi shop and was rather disappointed at how they performed. Can't help but wonder whether the undersized midrange is why the seemed to perform so poorly compared to the JBL HDI3600 in the same room.

The op is not about to replace his speakers, though. If he already has the panels and the measuring gear then a systematic approach of different arrangements may yield some results if he is willing to invest the time.

 

[TLS Guy]

A little off topic, but I wish I was retiring sooner. I would love to try and build a speaker like that but time does not currently permit that. I have yet to build the BMR kit that I got from Swerd and that will take priority. If you develop a speaker along those principals, I would be interested in getting the plans and design specs. Good topic for another thread.

The op's Monitor Audio Silver are generally considered a good speaker but I auditioned the Monitor Audio Gold at a hi-fi shop and was rather disappointed at how they performed. Can't help but wonder whether the undersized midrange is why the seemed to perform so poorly compared to the JBL HDI3600 in the same room.

The op is not about to replace his speakers, though. If he already has the panels and the measuring gear then a systematic approach of different arrangements may yield some results if he is willing to invest the time.

It was, that was the problem with that speaker. It is a fatal flaw. It won't show in the measurements as they are not done at power. In speaker design, you have to keep the power bands of instruments and ensembles front and center of your mind. If you don't you can think you have a great design and end up disappointed. I have a feeling a lot of speaker designers don't do this, as finding speakers deficient for power in crucial power bands is not uncommon. I learned years ago, not to make that mistake.