Ron's Speaker, Turntable, Power and Room Treatment Upgrades

Bobvin · Oct 25, 2017

Ron Resnick said:
Bob, thank you for detailing this. Did you use two offset layers of screwed and glued sheet rock, or the NoiseOut covers a single layer of sheetrock?

Hi Ron, the NoiseOut in my application went over the studs before we attached the drywall, so it cushions and separates the drywall from the studs. We did not do the double layer sheetrock, though I asked about it I was told unnecessary. Bonnie had spec'd 5/8 sheetrock, but the existing was 1/2 so we just copied what was there. As we were treating with panels after the rock was installed, I don't think it really made any difference though perhaps the hard fiberglass insulation that was attached had a different spec as a result of the thickness change. (Only Bonnie could answer that one.)

I do remember asking about the 'green glue' often discussed in forums when two layers of rock are installed, Bonnie said she'd never noticed any effect of that stuff.

Ron Resnick · Oct 25, 2017

Here are two videos from today's house visit, one at the listening position facing the front wall and one at the front wall facing the listening position.

Facing the front wall:

https://vimeo.com/239935305?ref=em-share

Facing the rear wall:

https://vimeo.com/239935416?ref=em-v-share

Ron Resnick · Oct 25, 2017

During a talk with PeterA today Peter suggested that I ask Bonnie about adding a second layer of sheetrock when the walls of the room get fixed.

I certainly should have blue jean insulation stuffed in various crevices and cavities.

I also spoke today with Matts of SMT, and I am in contact with RPG, as well.

Ron Resnick · Oct 26, 2017

Rodney Gold said:
So I could send one pair of interconnects from the Io to the bass towers, and use the loop built into the bass tower electronics to send the signal to the amplifiers of the ribbon panels, but then the length of the interconnect cables to the ribbon panels (do you mean bass panels) is longer than the length of the interconnect cables to the ribbon panels. Does this tiny time delay cause any issue?

I dont see it as being a problem.
Ron what is the sensitivity of the pendragon passive panels... will you get enough volume with a lowish powered amp?
if you , for example are sitting 4 m from the speakers, you will be -12db down from that sensitivity figure at the listening position
(The sound level will decrease by 6 dB every time the source to the listener's distance is doubled.)

Hi Rodney, I meant to write: "So I could send one pair of interconnects from the Io to the bass towers, and use the loop built into the bass tower electronics to send the signal to the amplifiers of the ribbon panels, but then the length of the interconnect cables to the ribbon panels is longer than the length of the interconnect cables to the bass towers. Does this tiny time delay cause any issue?"

This is because the length of the interconnect to the ribbon panel is the sum of the length of the interconnect from the Io to the bass tower plus the length of the interconnect from the bass tower to the ribbon panel.

Marcus · Oct 26, 2017

Ron Resnick said:
I also spoke today with Matts of SMT, and I am in contact with RPG, as well.

Matts is a great guy. Honest, very helpful and has great products. He literally saved my room.

Ron Resnick · Oct 28, 2017

shakti said:
As I have some experiance combining the Hypex driven subwoofermodels of my YG system with SET tubes for the satellites and as I am currently looking to theoretically merry Gryphon Poseidon mid/high's with the active Gryphon subwoofers, I like to share some thoughts.

Apart from any sound / performance results, the set up should work from the technical point of view, which is complex in it's own.

Let us have a look to the Aesthetix IO, which is a typical tube PreAmp, expecting high Impedance figures at the Amplifier side:

Aesthetix IO
Output impedance: 1K ohms SE, 600 ohms balanced
Recommended load: 10K ohms or greater (SE), 20K ohms or greater (Balanced)

( not using SET and XLR in parallel)

Looking to the Pendragon , it shows, that the XLR input would fit the bill with 40kohm:

Gryphon Pendragon
active crossover section included.

Input Impedans, balanced (20-20000Hz) 40KOhm
Input Impedans, single ended (20-20000Hz) 20KOhm

Gain +32dB

First logic would be, to combine the IO with a Gryphon amp and and the Pendragon on XLR. But unfortunately, the Gryphon Amps do have an input impedance between 10 kohm and 20 kohm which would give (using parallel cabling) a parallel input impedance of 8kohm or 13kohm, which is far below the IO can drive! So hard distortion would be the result.

The other aspect is the gain of the amps, the Pendragon has a gain of 32 db, the Gryphon amps do have 31dbm which is within the range you can adjust.

Let us have a look to the

NAT New Magma:

Input impedance 100 kohms
Gain +27.50 dB

Using at the IO the XLR output for the Pendragon bass towers (40 kohm) and the RCA output in parallel for the NAT New Magma, the IO would see a combined load of 29 kohm, which is within the Threshold.

But we would face a gain problem, as the NAT new Magma has only 27,5 db, which is 4,5db less than the bass tower.

But I do still assume, that this is within the adjustable range, as the most power amplifiers do have a gain of 26db, so the Pendragon Tower should cope with this.

If not, you can put the RCA cable to the Pendragon, which will give the basstower a arround 3db less powered signal and use the XLR cable for the NAT new Magma, which would make no difference , as the NAT is SET anyhow.

This is a pure technical view to the situation.

My current plan is similar, as I like to combine Gryphon Poseidon (if I can manage to get them) basstowers to Air Tight SET or NAT SE3 SET amps, having an Air Tight tube Preamp.

I heard Poseidon and Pendragon with Unison Reference tube Preamp and Unison Reference tube mono Amps, the results were great. On Poseidon, I had the comparison to Gryphon Mephisto Poweramp, I preferred the Unison mono amps.

Thank you very much, shakti, for this analysis. The single-ended input impedance for the MB-750s is 130k ohms, so the VTLs would work also.

Ron Resnick · Oct 28, 2017

The point a couple of people made about transferring to the bass towers the sound signature of the amplifier driving the ribbon panels reflects a misunderstanding of the design of the Pendragons. They're thinking of a conventional external subwoofer arrangement added to a full-range loudspeaker. That has nothing to do with the design of the Gryphon bass towers.

Ron Resnick · Oct 28, 2017

Mark Seaton wrote:

Hi Ron,

One key difference with your speakers vs Mike's are that the ribbon and AMT columns are both dipoles. Dipoles have a cancellation/reduction in output in the plane of the speaker's face with the sound radiating in a pattern that would look like a figure 8 if observed overhead. Here is an over simplification of the situation:

Here you can find some great info regarding dipole speaker operation and listening rooms from one of the experts on the matter, Siegfried Linkwitz. It is admittedly heavy on the math and a very technical approach to the issues at hand. Here is another great graphic I found from Linkwitz showing how reality deviates from theory with different types of dipole implementations:

For a better understanding of dipoles scan through this page from Linkwitz as well where I pulled this image which clarifies many of the differences between conventional, front firing speakers vs dipoles when set up in the room:

The point here is that the speaker's dipole operation above ~250Hz means there isn't much of an early lateral reflection for the woofer towers to block. Also important is that for the listening distance I suspect you will be at, the first side wall reflection will be well forward of the area shadowed by the woofer tower.

Could you give us a general recap of the size and openings to the space you are setting up in?

The "room" is a dedicated space -- 19.5' wide X 24.5' long X 14.5' high (except for an asymmetrical ceiling soffit at 9.5' that steps down above the left rear side of the room) -- but not really a dedicated room. One-third of the left side of the space (towards the rear wall) is open to the kitchen, and one-third of the right side of the space (towards the rear wall) is open to the equipment room.

The front wall is poured concrete. Right now over the front wall a sheet of drywall has been erratically glued directly to the concrete, leaving some areas of the drywall sounding solid and some areas sounding hollow when rapped with knuckles. There is no insulation in the walls, so I think I have to have all of the drywall taken off to expose the concrete areas and the wood-framed areas.

The first third of each side wall from the front wall is cinder block. So imagine the first third of a rectangular with a short side as the front wall -- the front wall is concrete and the first third of the connected parts of the side walls are cinder block. The remaining two-thirds of each side wall is either regular wood framing or open space (either to the kitchen on the left or to the equipment room on the right).

Today I researched:

1) mass-loaded vinyl
2) NoiseOut2 (Bonnie's version of mass-loaded vinyl)
3) resilient channel construction
4) Green Glue
5) Quietrock

Green Glue works as a visco-elastic layer between two sheets of drywall. Green Glue can be used to glue sheetrock to another layer of sheetrock (or to a hard wall surface, I believe).

Quietrock is a constrained damping product. It needs to not be attached directly to concrete or plaster because its method of operation requires it to be able to vibrate and dissipate vibration into heat, which it cannot do if it cannot move. Quietrock should be glued or screwed or both to wood framing or can form the outer layer of a resilient channel arrangement.

So, I can use Green Glue to glue regular drywall to the concrete walls, but I cannot use Green Glue with Quietrock on the concrete walls. I can use Quietrock on the wood framing, but I would rather not fir out the concrete walls with wood framing to hold the Quietrock because I would rather not haircut the room dimensions on three sides for no reason.

Yet, I assume that it is desirable to use the same wall surface material all around rather than having regular drywall on the concrete portions and Quietrock over the wood framing portions. I assume (but I do not know) that it cannot be good for the first third of the left side wall and the right side wall from the front wall to be regular drywall and the remaining two-thirds of the side walls to be Quietrock -- or should I not be concerned about that slightly dissimilar material?

I think all of the drywall has to come off of the wood-framed portions so the open areas in the framing can be filled with blue jeans insulation.

Right now I am inclined to use Quietrock all around, gluing it to the concrete sections with Green Glue, which should provide a bit of the flexibility Quietrock requires, and then screw and glue Quietrock on all of the wood-framed areas.

That leaves the slightly dropped drywall ceiling. Do I take all of the drywall of the ceiling and make sure the framing crevices are filled with blue jeans insulation and then install Quietrock?
Does this make sense?

What is your advice?

Mike Lavigne · Oct 28, 2017

Ron Resnick said:
The point a couple of people made about transferring to the bass towers the sound signature of the amplifier driving the ribbon panels reflects a misunderstanding of the design of the Pendragons. They're thinking of a conventional external subwoofer arrangement added to a full-range loudspeaker. That has nothing to do with the design of the Gryphon bass towers.

my comments regarding the MM7 approach to amp integration were just a question, not any suggestion that it's the only way it can be done. and if I gave that impression then I apologize. there is more than one way to skin a cat.

OTOH the MM7 is exactly the opposite of a full range speaker + a subwoofer. the MM7 is a single speaker system in two towers, neither of which are stand alone. the main towers roll off at the bottom and are not 'right' by themselves, and the same with the bass towers, which require the exact transition of the main towers to match.

I totally agree that a full range speaker + a subwoofer can be excellent, but never 'quite as good' as if it was a ground up fully integrated uncompromised design.

Ron Resnick · Oct 28, 2017

Mike Lavigne said:
my comments regarding the MM7 approach to amp integration were just a question, not any suggestion that it's the only way it can be done. and if I gave that impression then I apologize. there is more than one way to skin a cat.

OTOH the MM7 is exactly the opposite of a full range speaker + a subwoofer. the MM7 is a single speaker system in two towers, neither of which are stand alone. the main towers roll off at the bottom and are not 'right' by themselves, and the same with the bass towers, which require the exact transition of the main towers to match.

I totally agree that a full range speaker + a subwoofer can be excellent, but never 'quite as good' as if it was a ground up fully integrated uncompromised design.

Mike, not at all; nothing to apologise for all (I am not sure what you are referring to).

I came back to this a few days later and so I wasn't sure of who posted what, but a very friendly Viking looking out for me encouraged me to clarify this.

I actually agree with you on both points, Mike: a full-range speaker plus subwoofer can be excellent, but a fully integrated design like the MM7s and the Pendragons and the Kodos is best.

Folsom · Oct 28, 2017

All three - Kodo, Pendragon, MM7 - have very different crossover points. From a technical point of view the sentiment doesn't mean much.

The Pendragon ribbon towers couldn't play as a fullrange speaker. The MM7 and Kodo could without the subwoofer towers, but would have limited extension.

The argument that really could be made, is that speakers without enough drivers don't hold up well against full towers, stuffed with drivers.

LL21 · Oct 28, 2017

Folsom said:
All three - Kodo, Pendragon, MM7 ...

The argument that really could be made, is that speakers without enough drivers don't hold up well against full towers, stuffed with drivers.

FWIW, the 2 greatest speakers i have heard (Arrakis and Genesis 1s) both have lots of driver surface area, 'all out' design ethos with few considerations for cost or frankly any practical limitations. I do think that (all else being equal which it of course never truly is)...the effortless quality of a speaker goes a long way to create believability, nuance, dynamic scale...and surface area and sheer size certainly help defray some of the inherent limitations of physics involved in reproducing music.

Would love to hear these 3 speakers at some point.

Mark Seaton · Oct 31, 2017

Ron Resnick said:
Mark Seaton wrote:

Hi Ron,

One key difference with your speakers vs Mike's are that the ribbon and AMT columns are both dipoles. Dipoles have a cancellation/reduction in output in the plane of the speaker's face with the sound radiating in a pattern that would look like a figure 8 if observed overhead. Here is an over simplification of the situation:

Here you can find some great info regarding dipole speaker operation and listening rooms from one of the experts on the matter, Siegfried Linkwitz. It is admittedly heavy on the math and a very technical approach to the issues at hand. Here is another great graphic I found from Linkwitz showing how reality deviates from theory with different types of dipole implementations:

For a better understanding of dipoles scan through this page from Linkwitz as well where I pulled this image which clarifies many of the differences between conventional, front firing speakers vs dipoles when set up in the room:

The point here is that the speaker's dipole operation above ~250Hz means there isn't much of an early lateral reflection for the woofer towers to block. Also important is that for the listening distance I suspect you will be at, the first side wall reflection will be well forward of the area shadowed by the woofer tower.

Could you give us a general recap of the size and openings to the space you are setting up in?

The "room" is a dedicated space -- 19.5' wide X 24.5' long X 14.5' high (except for an asymmetrical ceiling soffit at 9.5' that steps down above the left rear side of the room) -- but not really a dedicated room. One-third of the left side of the space (towards the rear wall) is open to the kitchen, and one-third of the right side of the space (towards the rear wall) is open to the equipment room.

The front wall is poured concrete. Right now over the front wall a sheet of drywall has been erratically glued directly to the concrete, leaving some areas of the drywall sounding solid and some areas sounding hollow when rapped with knuckles. There is no insulation in the walls, so I think I have to have all of the drywall taken off to expose the concrete areas and the wood-framed areas.

The first third of each side wall from the front wall is cinder block. So imagine the first third of a rectangular with a short side as the front wall -- the front wall is concrete and the first third of the connected parts of the side walls are cinder block. The remaining two-thirds of each side wall is either regular wood framing or open space (either to the kitchen on the left or to the equipment room on the right).

Today I researched:

1) mass-loaded vinyl
2) NoiseOut2 (Bonnie's version of mass-loaded vinyl)
3) resilient channel construction
4) Green Glue
5) Quietrock

Green Glue works as a visco-elastic layer between two sheets of drywall. Green Glue can be used to glue sheetrock to another layer of sheetrock (or to a hard wall surface, I believe).

Quietrock is a constrained damping product. It needs to not be attached directly to concrete or plaster because its method of operation requires it to be able to vibrate and dissipate vibration into heat, which it cannot do if it cannot move. Quietrock should be glued or screwed or both to wood framing or can form the outer layer of a resilient channel arrangement.

So, I can use Green Glue to glue regular drywall to the concrete walls, but I cannot use Green Glue with Quietrock on the concrete walls. I can use Quietrock on the wood framing, but I would rather not fir out the concrete walls with wood framing to hold the Quietrock because I would rather not haircut the room dimensions on three sides for no reason.

Yet, I assume that it is desirable to use the same wall surface material all around rather than having regular drywall on the concrete portions and Quietrock over the wood framing portions. I assume (but I do not know) that it cannot be good for the first third of the left side wall and the right side wall from the front wall to be regular drywall and the remaining two-thirds of the side walls to be Quietrock -- or should I not be concerned about that slightly dissimilar material?

I think all of the drywall has to come off of the wood-framed portions so the open areas in the framing can be filled with blue jeans insulation.

Right now I am inclined to use Quietrock all around, gluing it to the concrete sections with Green Glue, which should provide a bit of the flexibility Quietrock requires, and then screw and glue Quietrock on all of the wood-framed areas.

That leaves the slightly dropped drywall ceiling. Do I take all of the drywall of the ceiling and make sure the framing crevices are filled with blue jeans insulation and then install Quietrock?
Does this make sense?

What is your advice?

I'm going to first quickly cross post my responses from two other threads as they relate to the discussion above:

I found this thread soon after making the previous post here. You asked in the separate thread:

When you write "the speaker's dipole operation above ~250Hz means there isn't much of an early lateral reflection for the woofer towers to block" are you implying that I do not have to worry much about first reflections and I should not put any acoustic panel at the first reflection points? Are you implying that diffusion at the first reflection points is likely to be better for me than absorption at the first reflection points?

The answer is entirely dependent on your room/speaker/listener positioning and geometry, along with the exact aiming of the mid/high frequency columns. Based on your description, I expect the 90 deg off axis null from the main columns to mostly point at the bass column location. We can't know if the bass tower will shadow the first reflection point without knowing approximate speaker locations, room width, and listening distance. What's equal or more important to understand is that with the dipole ribbon/AMT columns, while much wider in dispersion than your Monoliths, will still have a significant reduction in energy 90 deg to the speaker's aim. In many rooms this means you can adjust how much energy arrives at the first reflection area.

Mark Seaton · Oct 31, 2017

Pulling from the Quietrock thread:

Ron Resnick said:
Please tell me about your actual experiences with Quietrock.

In your particular the listening room, what did you use it for? What were you trying to accomplish and did Quietrock achieve your goal? What other products or techniques did you consider?

Did you use it to prevent sound from leaking from your listening room into other areas of your house? Or did you use it to prevent the walls of your listening room from resonating with the music?

What was your method of installing the Quietrock? Did you ever glue Quietrock to any underlying surface material?

Did you ever mix Quietrock with Green Glue?

Did you ever directly compare Quietrock with mass-loaded vinyl?

If I do not care at all about sound escaping the listening room into other areas of the house, is Quietrock justified solely for the purpose of having a constrained layer damping product on the walls of the listening room so that the walls of the listening room are less likely to resonate with the music?

What wall treatment product do you think has the greatest efficacy for preventing the walls from vibrating in response to music playing from the loudspeakers?

Thank you!

As detailed in Mike's response, the problem to solve, and restrictions of the application are huge considerations in determining if one material makes more sense vs. others:

Mike Lavigne said:
in 2010 I found I had uneven and overdamped bass response side to side due to excessive bass trapping and uneven loading of the walls; one side was an outside wall, the other inside (this was our best guess of causes and effects). so the goal was to establish consistent room boundaries in the front sides and front window wall. we already had the whole room (all walls and ceilings) cocooned in a double layer of 5/8" sheetrock, and my cabinetry was built out from that. so that was the base layer on top of the studs.

we considered multiple layers of more sheetrock, but then came across Quietrock 545 (at that time it was also called 'THX' 545 in reference to the Home Theatre application). 545 was more effective than 6 stacked sheets of 5/8" sheetrock, and would take up as much less space...

your contractor will hate you since it's so heavy to deal with and it will tear up saw blades with that aluminum layer so it's a real pain to work with. but that part is over quick, and you have your solid walls. and it's the time and labor that is the expense; using the right materials has minimal cost differences.

The key to understand here is the equivalence of the 1 3/8" thick Quietrock 545 to just under 6 sheets of 5/8" drywall, which makes for 3.5" thick. That ~2.5x thinner factor comes from the density per area difference of about 2.6 lb/ft2 for 5/8" drywall, vs 6.7 lbs/ft2 for the QR 545 (I see the PDF datasheet contradicts noting 6.25 lb/ft2). Of course some quick math indicates each 4x8' sheet will be 200-215 lbs.

Hence the last note about the contractor. The lamination of the Quietrock 545 also affords some additional damping, but similar can certainly be achieved with multiple, equal thickness layers of drywall and green glue with a good contractor adding up to the same mass/area.

For the issue Mike was trying to address, this was absolutely an appropriate selection. At the same time, you can see that the 510 & 530 products don't offer much advantage beyond using 2 layers of common drywall. For those starting from scratch, my preference would be to see a heavy and rigid outer shell using Baltic Birch ply and/or MDF with wood or steel stud framing with isolation of some form to the flexible, but damped mass of the inner walls, more commonly 2-3 layers of drywall with green-glue. This gives the outer layer of isolation, but then allows the inner layer to eat up some energy from low frequency modes reducing their intensity (less difference peak to valley in level).

In what I've seen of your space, your biggest focus should be on maintaining left to right symmetry where ever you can. In cases like yours that might often come by NOT trying to make things overly rigid when you have a weaker boundary on the opposing surface, or beefing up the areas which do have matching rigid boundaries.

Mark Seaton · Oct 31, 2017

Ron Resnick said:
Mark Seaton wrote:

Hi Ron,
...
Could you give us a general recap of the size and openings to the space you are setting up in?

The "room" is a dedicated space -- 19.5' wide X 24.5' long X 14.5' high (except for an asymmetrical ceiling soffit at 9.5' that steps down above the left rear side of the room) -- but not really a dedicated room. One-third of the left side of the space (towards the rear wall) is open to the kitchen, and one-third of the right side of the space (towards the rear wall) is open to the equipment room.

The front wall is poured concrete. Right now over the front wall a sheet of drywall has been erratically glued directly to the concrete, leaving some areas of the drywall sounding solid and some areas sounding hollow when rapped with knuckles. There is no insulation in the walls, so I think I have to have all of the drywall taken off to expose the concrete areas and the wood-framed areas.

The first third of each side wall from the front wall is cinder block. So imagine the first third of a rectangular with a short side as the front wall -- the front wall is concrete and the first third of the connected parts of the side walls are cinder block. The remaining two-thirds of each side wall is either regular wood framing or open space (either to the kitchen on the left or to the equipment room on the right).

Today I researched:

1) mass-loaded vinyl
2) NoiseOut2 (Bonnie's version of mass-loaded vinyl)
3) resilient channel construction
4) Green Glue
5) Quietrock

Green Glue works as a visco-elastic layer between two sheets of drywall. Green Glue can be used to glue sheetrock to another layer of sheetrock (or to a hard wall surface, I believe).

Quietrock is a constrained damping product. It needs to not be attached directly to concrete or plaster because its method of operation requires it to be able to vibrate and dissipate vibration into heat, which it cannot do if it cannot move. Quietrock should be glued or screwed or both to wood framing or can form the outer layer of a resilient channel arrangement.

So, I can use Green Glue to glue regular drywall to the concrete walls, but I cannot use Green Glue with Quietrock on the concrete walls. I can use Quietrock on the wood framing, but I would rather not fir out the concrete walls with wood framing to hold the Quietrock because I would rather not haircut the room dimensions on three sides for no reason.

Yet, I assume that it is desirable to use the same wall surface material all around rather than having regular drywall on the concrete portions and Quietrock over the wood framing portions. I assume (but I do not know) that it cannot be good for the first third of the left side wall and the right side wall from the front wall to be regular drywall and the remaining two-thirds of the side walls to be Quietrock -- or should I not be concerned about that slightly dissimilar material?

I think all of the drywall has to come off of the wood-framed portions so the open areas in the framing can be filled with blue jeans insulation.

Right now I am inclined to use Quietrock all around, gluing it to the concrete sections with Green Glue, which should provide a bit of the flexibility Quietrock requires, and then screw and glue Quietrock on all of the wood-framed areas.

That leaves the slightly dropped drywall ceiling. Do I take all of the drywall of the ceiling and make sure the framing crevices are filled with blue jeans insulation and then install Quietrock?
Does this make sense?

What is your advice?

Depending on the flatness of the concrete and cinder block walls, I think you may have some issues getting good adhesion directly to the surface with drywall. You can fir out the surface with a 2x4 on side so it is only 1.5" thick, or even use 2x3's for 2.5" of space behind Quietrock. I do think the 530 or 545 product might work well if spaced off the wall. I'm not sure you'll observe a big difference between Roxul/rockwool vs the denim insulation. I would lean toward the denim, and it is more green after any dust settles from cutting the cotton fibers. Ideal with minimal intrusion would probably be framing with the Quietrock, which would be very dead, but still can move a little at the lowest frequencies. If you don't want to loose any space in the room, I would consider an alternate of 2-3 layers of 1/2" drywall with green glue between. This way the multiple layers and green glue would damp out any areas not securely glued to the concrete or cinder block, and you get the constrained layer damping from the green glue. Green glue can be used between materials other than drywall, where MDF to MDF makes for a hyper damped boundary.

While at first glance counter intuitive, for a suspended boundary you want symmetrical layering, as this directs the energy to the viscous boundary where it is absorbed as heat. Dis-similar material should only be used with symmetrical inner/outer layers, where you could for example use drywall of different thicknesses: 1/2" - GG- 5/8" - GG - 1/2". Changing the materials isn't a problem if it makes sense, but you want the symmetry to insure the viscous damping layer is effective.

Getting back to the symmetry, the front vs side walls can be somewhat different, where again I would be more focused on achieving symmetry where you can. If aesthetically it works, I would consider even building out the soffit at the rear of the room to be symmetrical left/right. You can add or remove many different treatments, but structural symmetry is very hard to compensate for after the fact. It does sound like the openings at the rear 1/3rd of the room are reasonably symmetrical, and will end up greatly reducing the bass build-up in the room, with the front to back length modes as they relate to the listener and speaker location to be the main concern in the bass range. I expect that through seating location, bass tower placement, and bass treatments at the rear of the room you should be able to get things dialed in nicely. I would imagine a heavy curtain similar to what Bonnie used in Steve's home might be useful to pull across the L/R openings where you will likely want both fully open, or fully closed. For the side walls I would remove drywall where the cinder block ends and make sure the surface is well damped and stuffed with the denim insulation or Roxul.

How much depth is reasonably available at the rear wall of the room behind the left/right openings to the room?

pjwd · Oct 31, 2017

Ron - you are getting some good advice form Mark - on the SL pages he referenced there is a calculator for positioning dipole speakers which is quite good

WRT ceiling you could take the asymmetry out of the equation by hanging baffles below the lower ceiling and continuing them across the space - this would reduce first reflections from ceiling and provide a sense of increased height plus a visual symmetry - I have used this in control rooms - they are setout to avoid reflections and as such have an expanding spacing - they are an absorbtive material which also provides some damping

cheers

Phil

Ron Resnick · Nov 2, 2017

Thank you, Phil!

But with my ceiling height of 14.5' why would I want to lower the acoustic height of the ceiling to match the 9' asymmetrical soffit? Wouldn't it just be better to deal with the soffit if I have to by putting some absorbent material on the face of it or the underside of it?

Ron Resnick · Nov 2, 2017

The rear third of each of my side walls is symmetrically open to adjacent rooms. The front third of each side wall is symmetrically built out of cinder block. But the middle third of the left wall is wood framing and the middle third of the right side wall is cinder block.

Mark, Maybe the Quietrock 545 on the cinder block sections of my side walls, continuing over the wood framing sections of my side walls, would equalize the asymmetry, and create new, symmetrical acoustic boundaries?

I do not have enough space to build each wall out from the studs with an isolation channel of clips and hangars to hang 5/8" drywall and then Quietrock 545 (1 3/8") and then 3/4" plywood. Mark, Which do you think is more critical to employ to create the new, symmetrical acoustic room boundaries -- the Quietrock 545 or the 3/4" plywood?

If I used the Quietrock 545 and the 3/4 plywood, could I forego the insulation channel? Could I forgo the first (inside) layer of 5/8" drywall?

Which components do you think are more important to achieve a rigid, isolation exterior, but also achieve some low frequency absorption from an inner layer?

Ron Resnick · Nov 3, 2017

Only recently did I realize how theoretically and practically complicated is my listening space, with three different side wall "surfaces" (cinder block, wood framing and air) in an asymmetrical pattern on each side. The middle third of the left wall is wood framing and the middle third of the right side wall is cinder block.

I have a tentative theoretical framework for my wall treatment idea. Bonnie will run an acoustic simulation, and I will receive Bonnie's recommendation. Nyal will take some measurements, and I will receive Nyal's recommendation. Then I will make a decision.

My current theoretical framework focuses on the importance of the side walls reacting to sound waves in an identical (i.e., symmetrical) manner. My theoretical premise here is to make each surface have the same acoustic attributes of the surface opposite it.

One way to accomplish this would be to replace the wood framing in the middle third of the left side wall with cinder block, but that is not practical. So I think the best I can do is to make that wood frame section as rigid as possible.

Instead of filling up the openings and cavities in the wood frame section with blue jeans insulation I would fill up those openings and cavities with wood or some other rigid filler material. What is the most rigid type of wall insulation which could be fitted in or squirted in? Is foam insulation rigid? Is foam insulation more rigid than wood? So whatever is the most rigid wood frame filler, that is what I fill up the wood frame area with in the middle of the left side wall.

Then what is the most rigid outer layer material? Maybe I then affix Quietrock 545 (1 3/8" thick including a 1/4" layer of aluminum) or Baltic birch plywood to the outside of every wood frame section which is opposite cinder block, and I attach the Quietrock 545 to any area of cinder block which is opposite wood framing.

The narrow wood frame section on the left side of the front wall (the yellowish painted wall with blue tape squares) should be filled with rigid material to imitate as much as possible poured concrete (which is what the rest of the entire front wall is made of). Then I would cover both sections of the front wall with simple 5/8" drywall board.

Screen Shot 2017-11-03 at 3.38.24 PM.jpg

I want the angled ceiling soffit hanging down from the left rear corner of the ceiling to disappear acoustically so I want that soffit to be as absorptive as possible. I would the fill the cavities in the soffit will blue jeans insulation and put sound absorbing material on the vertical face of the soffit and underneath the soffit (the "ceiling" of the soffit facing the floor).

The rear end of the right side wall is wood framing. The rear end of the left side wall is air. I want the rear end of the right side wall to disappear acoustically (so it matches as closely as possible the "non-wall" at the rear of the left side wall) so I want that section of the right side wall to be as absorptive as possible. I would the fill the cavities in that section of the wood framing will blue jeans insulation and put sound absorbing material on the vertical face of that wall.

What do you think of this theoretical framework?

What is the most rigid material to insert or squirt or build into wood framing (short of concrete or cinder blocks) to make it as cinder block-like as possible?

Is absorption the right technique to make a wall or a soffit "disappear" acoustically?

Mark Seaton · Nov 3, 2017

Ron Resnick said:
The rear third of each of my side walls is symmetrically open to adjacent rooms. The front third of each side wall is symmetrically built out of cinder block. But the middle third of the left wall is wood framing and the middle third of the right side wall is cinder block.

Mark, Maybe the Quietrock 545 on the cinder block sections of my side walls, continuing over the wood framing sections of my side walls, would equalize the asymmetry, and create new, symmetrical acoustic boundaries?

I do not have enough space to build each wall out from the studs with an isolation channel of clips and hangars to hang 5/8" drywall and then Quietrock 545 (1 3/8") and then 3/4" plywood. Mark, Which do you think is more critical to employ to create the new, symmetrical acoustic room boundaries -- the Quietrock 545 or the 3/4" plywood?

If I used the Quietrock 545 and the 3/4 plywood, could I forego the insulation channel? Could I forgo the first (inside) layer of 5/8" drywall?

Which components do you think are more important to achieve a rigid, isolation exterior, but also achieve some low frequency absorption from an inner layer?

Circling back, this was the last note in the first post I made in the Quietrock thread:

Mark Seaton said:
From what I've seen of your space, your biggest focus should be on maintaining any degree of left to right symmetry where you can. In cases like yours that might often come by NOT trying to make things overly rigid when you have a weaker boundary on the opposing surface, or beefing up the areas which do have matching rigid boundaries.

Since then it's become clear that your two openings at the rear keep things pretty well symmetrical in that area, but the front area has the differences you note with how far the cinder block construction extends into the room from the front wall.

As one or two others mentioned more recently, while there are certainly differences between a cinder block wall and 1/2" drywall or Quietrock with 24" stud spacing, this difference is NOT going to eliminate bass modes in any room. The more flexible boundaries will reduce the intensity of certain modes some, but the differences are still in the realm of "how big is the peak?" not "is the peak gone?"

The cinder block and concrete walls need a cosmetic covering. In most homes drywall makes the most sense aesthetically, but other options are available like Mike Lavigne chose for his room. For your space I would stick to conventional drywall with so much existing surface that it doesn't sound like you will be replacing. Any facing you glue directly to the concrete or cinder block is for aesthetic reasons only and won't change the acoustics. If you chose to fir out the drywall by 0.5" to 1.5", it makes a very minor change, but nothing that takes up modest depth will significantly change how the bass reacts with the cinder block boundary. In my mind, this means you should beef up the framed wall on the left where it is opposite the cinder block construction on the right. I don't see any reason to use isolation clips here, as you want a more rigid boundary. I would flip the layers and mount the 1/2-3/4" high grade plywood to the studs for a rigid surface, and then mount the Quietrock 545 to the plywood for a drywall finish in the room. In a relatively modest thickness, I think that will be as close as you can get to cinder block.

As I typed the last sentence, a thought did occur... It might be easier to just have a contractor strip out the framed wall and install a cinderblock or similar wall to match the right side of the room. We're ruminating on ways to match your existing drywall over cinder block after all.

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