My New Theater

[Todd Anderson]

Yes... we actually just finished phase 1, which was to convert the garage into a half storage/gym space. We had the floor finished with an hard epoxy and then finished the garage off new beams/decking in the rafters (for storage), insulation, and dry wall. We also installed jack-shaft garage door openers to save space.

Essentially, the garage doors open to reveal storage bays and access to the new attic storage area. And an insulated dividing wall (that we can easily remove) has created the back-end of the garage into a gym. The gym room has its own heating/cool unit installed in the ceiling. We're still waiting on shutters... and I have to install some gym flooring and move equipment. That should happen in the coming days/week.

Phase 2 is laying new foundation/structure for a new basement room and our kitchen expansion.

Phase 3 is a kitchen renovation... and we're basically gutting the basement (opening it up to make it more usable for our kids and their friends). The home theater is having some work done on it... will probably be out of commission for several months :-(. I think it will all be worth it tho!

 

[Todd Anderson]

here’s a few pics of the garage area. The storage bay looks a tad full... but it’s housing some construction supplies at the moment (you can’t see it in the pic). Once that’s gone our stuff will have a lot more breathing room...

 

[bkeeler10]

Nice! Well, having suffered through almost a year of construction, and even though there are still some loose ends to wrap up, I can say that it is worth it if you get the space you want. We're already enjoying the new kitchen and great room, and just moved kids into a new bedroom downstairs. So yeah, I can say it is worth the pain, and that's even without the theater up and running just yet. When that's done, I can sit back and relax a bit. A year from now, the pain will be a distant memory

 

[Todd Anderson]

It's good to hear that... because I have a feeling our fall/winter are going to be pretty painful. I sure hope it doesn't turn into a year long project... a year is ton of time. But, as you said, it will be easy to forget!

 

[bkeeler10]

All right, folks, I think the pace of this thread is about to pick up. Our house is essentially done (finally!), and I'm starting to outfit the theater.

First thing that has gone up is the projector screen. It is a 110" wide, acoustically transparent, retractable scope screen by Seymour AV (using the UF fabric). I've got it on the ceiling, but am already thinking about moving it away from the front wall a bit to give me a few extra inches behind it.

I also have my projector on hand. It is the JVC DLA-RS440. The projector hush box needs paint and a few finishing touches, so the projector has not been installed yet. I did get a 50' fiber HDMI cable from Monoprice, and I need to fish that through my conduit.

We couldnt resist watching a movie over the weekend (The Last Jedi). I just set the projector on a table, set it to cinema mode, and zoomed/ focused it. Plugged in my Oppo 103 and went straight from it to my Outlaw amp and to a pair of Chane A1.4. Image was pretty good, but color and brightness need to be adjusted. Sound was a little flat, but to be expected in an untreated, un-eq'd and pretty much empty room with speakers up against a wall. Pictures attached.

Next steps are to terminate speaker cables with bananas, order acoustic panels (discussing with GIK right now), order AVR and UHD bluray player, build subs, order speakers, etc. Will be doing all this over the next month.

Does anyone have any recommendations for shelves in my component cubby? It's just a framed inset in the wall, and I'm looking for a system that will allow for several adustable-height shelves.

 

[Todd Anderson]

Awesome. Congrats!!!

I don't have any cubby recommendations. I think you're wise to look for a way to make it adjustable... I built my own cubby and tried to make my own adjustable shelves. Didn't work out so well. Have you considered just buying a true rack system to insert into your framed area?

 

[Matthew J Poes]

For shelves, Have you considered this https://woodworker.com/24-zinc-standard-mssu-853-056.asp

They are designed to be inset, but don’t have to be. The hardware is typically available at most hardware stores and isn’t very expensive. You would need to make your own shelves.

Personally, if you do make shelves of wood, I would consider putting holes in the shelves to allow better ventilation. You also need to cut an opening along the back for wiring.

There are also pull-out spinning racks but those cost a lot of money. They are convenient to be sure, but you can spend $1000 on the rack alone.

For acoustics, my opinion differs from GIKs a little, so I’ll give it. Take it or leave it. Where GIK will likely encourage a few bass traps and a lot of normal absorbing panels, I think you are better off just using their bass traps. Don’t use any normal absorbing panels. The reason is that most spaces don’t have enough bass absorption, and when you treat them, end up with too much mid/high absorption. My suggestion is to use the thickest bass traps you can stomach and to use the range limited models quite a bit too.

It’s also very common to get advice to treat the first reflection pints as if they id a given. However I would suggest you try before you commit. Personally I don’t like treating first reflection points. I do treat them for bass absorption, but not mid/high. The reason is that research into our perceptions of spaciousness and envelopment found that absorbing the first reflections were detrimental to this. Our perception of the realness of the reproduced performance is diminished. Some people like this, it creates a more intimate feel. This is why I say, try before you commit. You might like it, you might not.

Treating the ceiling for bass is really critical. Again, I would hang bass traps from the ceiling rather than absorber panels. Again, I don’t like to absorb all the mids and highs from the ceiling. I prefer something that focuses on the bass. In my own system I have an MLS panel and a plan to add range limited bass traps further out.

Ceiling bass absorption is under-appreciated. I didn’t even realize how big a deal it was until I began to experience it both ways. The best sounding spaces I setup commonly had acoustic false ceilings. I never liked those and wrote them off, not realizing how much bass they absorbed. I then started treating normal ceilings and finding that it made big differences both measurably and audibly. Out of that idea evolved my current approach, which focuses on range limited ceiling treatment. For false ceilings I have now developed and deployed a multi-layer approach that fills the joists with insulation, followed by the normal acoustic tile, and faced with a pvc decorative tile adhered to it. This maintains the reflectiveness of the mid and high frequencies but drastically increases bass absorption. There are virtually no measurable effects consistent with ceiling SBIR or vertical modes. Medial modes are totally absent.

The above can be partially replicated with range limited bass traps covering most of the ceiling. Since that is often unreasonable, you can come close by covering the front third plus perimeter.

 

[JStewart]

I have an older VTI rack with adjustable shelf heights, but just checked and they all seem to be fixed height now. Zero help I know.
I've been considering this by monoprice https://www.monoprice.com/product?p_id=27678 Seems a really good value and holds a lot weight. Downside once again, not adjustable. Does look to be
slightly configurable and the heights common. I think you can also put 2 together to make a taller unit with more shelves.
Good luck with your search.
The room looks great. Enjoy.

 

[bkeeler10]

Awesome. Congrats!!!

I don't have any cubby recommendations. I think you're wise to look for a way to make it adjustable... I built my own cubby and tried to make my own adjustable shelves. Didn't work out so well. Have you considered just buying a true rack system to insert into your framed area?

I have thought about a rack system, yes. Just haven't looked into it, but I'm assuming it won't be cheap. Gonna do some digging though.

 

[bkeeler10]

For shelves, Have you considered this https://woodworker.com/24-zinc-standard-mssu-853-056.asp

They are designed to be inset, but don’t have to be. The hardware is typically available at most hardware stores and isn’t very expensive. You would need to make your own shelves.

Personally, if you do make shelves of wood, I would consider putting holes in the shelves to allow better ventilation. You also need to cut an opening along the back for wiring.

There are also pull-out spinning racks but those cost a lot of money. They are convenient to be sure, but you can spend $1000 on the rack alone.

For acoustics, my opinion differs from GIKs a little, so I’ll give it. Take it or leave it. Where GIK will likely encourage a few bass traps and a lot of normal absorbing panels, I think you are better off just using their bass traps. Don’t use any normal absorbing panels. The reason is that most spaces don’t have enough bass absorption, and when you treat them, end up with too much mid/high absorption. My suggestion is to use the thickest bass traps you can stomach and to use the range limited models quite a bit too.

It’s also very common to get advice to treat the first reflection pints as if they id a given. However I would suggest you try before you commit. Personally I don’t like treating first reflection points. I do treat them for bass absorption, but not mid/high. The reason is that research into our perceptions of spaciousness and envelopment found that absorbing the first reflections were detrimental to this. Our perception of the realness of the reproduced performance is diminished. Some people like this, it creates a more intimate feel. This is why I say, try before you commit. You might like it, you might not.

Treating the ceiling for bass is really critical. Again, I would hang bass traps from the ceiling rather than absorber panels. Again, I don’t like to absorb all the mids and highs from the ceiling. I prefer something that focuses on the bass. In my own system I have an MLS panel and a plan to add range limited bass traps further out.

Ceiling bass absorption is under-appreciated. I didn’t even realize how big a deal it was until I began to experience it both ways. The best sounding spaces I setup commonly had acoustic false ceilings. I never liked those and wrote them off, not realizing how much bass they absorbed. I then started treating normal ceilings and finding that it made big differences both measurably and audibly. Out of that idea evolved my current approach, which focuses on range limited ceiling treatment. For false ceilings I have now developed and deployed a multi-layer approach that fills the joists with insulation, followed by the normal acoustic tile, and faced with a pvc decorative tile adhered to it. This maintains the reflectiveness of the mid and high frequencies but drastically increases bass absorption. There are virtually no measurable effects consistent with ceiling SBIR or vertical modes. Medial modes are totally absent.

The above can be partially replicated with range limited bass traps covering most of the ceiling. Since that is often unreasonable, you can come close by covering the front third plus perimeter.

Matt,

Thanks for your detailed reply, as usual. Regarding shelving, I thought I would leave a gap at the back of the shelves an inch or two wide, across the whole width, so that cables can freely pass top-to-bottom. Good suggestion though to have holes in each shelf for ventilation - maybe the shelves could be perforated across their entire area.

Interesting thoughts regarding acoustics. It is certainly the case that it is really hard to have too much bass trapping in small rooms (which pretty much every home theater is), but quite easy to overdamp the upper octaves. I had envisioned the GIK soffit trap (18" x 18") in the front wall-wall and wall-ceiling corners, along with their Monster trap ( > 7.25" thick) behind each speaker on the front wall (SBIR mitigation), which won't fit as it turns out, but the 244 (at 5.25" thick) is the alternative. I was also planning on absorbing with the 242 (their 3" panel) at all first reflection points (side walls, ceiling, back walls) from all three front speakers to the MLP. Anyway, I ran that plan by them and they suggested most of the bass traps should be range-limited to both increase the effectiveness in the bass and not deaden above the bass range too much.

So, the traditional approach for a room designed for theater (or other multichannel application) is to make the space quite dead, like RT60 times in the 0.3 - 0.4 second range. The thought being that the mix should contain the ambiance of the space (whether created by the recording location or artificially/electronically), and the audio system should be playing that track without much interference from the room. A two-channel environment is different, and doesn't want to be as dead since the stereo effect depends to some degree on boundary reflections.

However, it sounds like your approach would allow for more reverberation even in a multichannel situation. Are there reverberation metrics that should be generally adhered to in this approach? How dead is too dead, and how live is too live? I am also interested in whether your experience and the research suggests a diffusive surface at first reflection points is better than a hard reflection and/or absorption. Certainly there is the potential for comb filtering from hard reflections arriving at the MLP later than the direct sound. Care to elaborate?

It does seem to me that a theater should sound spacious, almost without walls as it were. The goal should be to put you in the middle of the mix and make you forget you're sitting in a room listening to a bunch of speakers.

By the way, I remember you asked me a while ago if I intended to do ray tracing in EASE. The model is built, and I did run what is called mirror image impacts, which allows me to see easily where first reflections would occur. Obviously it can do higher order reflections as well. What would you be interested in seeing? I would be happy to run it and post the results.

 

[Matthew J Poes]

Matt,

Thanks for your detailed reply, as usual. Regarding shelving, I thought I would leave a gap at the back of the shelves an inch or two wide, across the whole width, so that cables can freely pass top-to-bottom. Good suggestion though to have holes in each shelf for ventilation - maybe the shelves could be perforated across their entire area.

Interesting thoughts regarding acoustics. It is certainly the case that it is really hard to have too much bass trapping in small rooms (which pretty much every home theater is), but quite easy to overdamp the upper octaves. I had envisioned the GIK soffit trap (18" x 18") in the front wall-wall and wall-ceiling corners, along with their Monster trap ( > 7.25" thick) behind each speaker on the front wall (SBIR mitigation), which won't fit as it turns out, but the 244 (at 5.25" thick) is the alternative. I was also planning on absorbing with the 242 (their 3" panel) at all first reflection points (side walls, ceiling, back walls) from all three front speakers to the MLP. Anyway, I ran that plan by them and they suggested most of the bass traps should be range-limited to both increase the effectiveness in the bass and not deaden above the bass range too much.

So, the traditional approach for a room designed for theater (or other multichannel application) is to make the space quite dead, like RT60 times in the 0.3 - 0.4 second range. The thought being that the mix should contain the ambiance of the space (whether created by the recording location or artificially/electronically), and the audio system should be playing that track without much interference from the room. A two-channel environment is different, and doesn't want to be as dead since the stereo effect depends to some degree on boundary reflections.

However, it sounds like your approach would allow for more reverberation even in a multichannel situation. Are there reverberation metrics that should be generally adhered to in this approach? How dead is too dead, and how live is too live? I am also interested in whether your experience and the research suggests a diffusive surface at first reflection points is better than a hard reflection and/or absorption. Certainly there is the potential for comb filtering from hard reflections arriving at the MLP later than the direct sound. Care to elaborate?

It does seem to me that a theater should sound spacious, almost without walls as it were. The goal should be to put you in the middle of the mix and make you forget you're sitting in a room listening to a bunch of speakers.

By the way, I remember you asked me a while ago if I intended to do ray tracing in EASE. The model is built, and I did run what is called mirror image impacts, which allows me to see easily where first reflections would occur. Obviously it can do higher order reflections as well. What would you be interested in seeing? I would be happy to run it and post the results.

My approach leads to pretty low RT60 times too. If you did manage to see values above .4-.5 I would be surprised, but at that point I would probably add more full range absorption. In the spaces I’ve treated, that hasn’t been the case. My space uses a lot of range limited absorption, the only place with full range absorption is the front wall and ceiling behind the screen. My RT60 is well under .3. I believe keeping it between .25 and .5 is ideal. Where you land is a matter of taste.

Ok now as for the first reflections causing comb filtering, a lot of that is more measurement artifact than what we hear. Also keep in mind that absorbers, even really big ones don’t absorb all the sound. They demonstratably reflect a lot of sound back. That is ok, it would even be good if the sound reflected back was unmolested. However what is reflected back is actually highly corrupted by the non-flat absorption of fabric covered panels at these angles. Toole shows an image in his book. I actually questioned if it was accurate under all circumstances and sought to replicate what Toole did as well test different panel designs. Eventually I developed an institu setup to do that and was able to roughly replicate his results. I then tested curved, MLS, etc. in all cases the results were the same. The response of the reflection with an acoustic panel was far worse than without.

Even Toole admits that some people prefer this sound however. So while his blind experiments showed a preference for keeping the first reflections intact, he seems to concede that you should decide for yourself.

I currently have movable panels at my first reflection pints and can try an MLS, absorption, or simply move them and have full reflection. I find I like the MLS version, even for movies. I also like the full reflection quite a bit. I find full absorption to sound a bit too dry. This may be an artifact of my rooms already seriously low RT60 times.

The two rooms I treated the ceiling with my layered approach were 2-channel rooms. I intentionally targeted a higher RT60 for those rooms. I went for around .5-.6 range and came in fairly close. I had to actually add reflective surfaces to get up to that. Hence the way I did the ceiling. In a theater I think i would probably do a mix.

Ok now for diffusers. I’m certainly a fan. You need to have the space for them though. I know a lot of people who stick diffusers in the wrong places and sit far too close (like back wall and sit against them). For home theaters I like them on the center of the front wall between the speakers with a mix of bass traps. I like them on the side walls at first reflection points. I also like them on ceilings. However I have had very mixed results on ceilings 8 feet or less.

 

[Matthew J Poes]

For ray tracing, just an image is cool. I know it produces a lot more data that would be hard to share.

 

[bkeeler10]

Ok now as for the first reflections causing comb filtering, a lot of that is more measurement artifact than what we hear. Also keep in mind that absorbers, even really big ones don’t absorb all the sound. They demonstratably reflect a lot of sound back. That is ok, it would even be good if the sound reflected back was unmolested. However what is reflected back is actually highly corrupted by the non-flat absorption of fabric covered panels at these angles. Toole shows an image in his book. I actually questioned if it was accurate under all circumstances and sought to replicate what Toole did as well test different panel designs. Eventually I developed an institu setup to do that and was able to roughly replicate his results. I then tested curved, MLS, etc. in all cases the results were the same. The response of the reflection with an acoustic panel was far worse than without.

Interesting. How is an absorption coefficient of 1.00 to be interpreted? A 2" batt of OC703, for example, is basically 1.00 from 500 Hz up to 10 kHz or higher. Perhaps I have a fundamental misunderstanding of what absorption coefficients mean. In any event, spectral distortions from a reflection seem like a bad thing

I currently have movable panels at my first reflection pints and can try an MLS, absorption, or simply move them and have full reflection. I find I like the MLS version, even for movies. I also like the full reflection quite a bit. I find full absorption to sound a bit too dry. This may be an artifact of my rooms already seriously low RT60 times.

Pardon my ignorance, but what does MLS stand for?

The two rooms I treated the ceiling with my layered approach were 2-channel rooms. I intentionally targeted a higher RT60 for those rooms. I went for around .5-.6 range and came in fairly close. I had to actually add reflective surfaces to get up to that. Hence the way I did the ceiling. In a theater I think i would probably do a mix.

That's another thing I've been thinking about. Since my room will sometimes be used for 2-channel listening, I was hoping to have the ability to easily (like, in a couple minutes or less) modify the acoustics to better suit 2-channel vs multichannel listening.

Ok now for diffusers. I’m certainly a fan. You need to have the space for them though. I know a lot of people who stick diffusers in the wrong places and sit far too close (like back wall and sit against them). For home theaters I like them on the center of the front wall between the speakers with a mix of bass traps. I like them on the side walls at first reflection points. I also like them on ceilings. However I have had very mixed results on ceilings 8 feet or less.

I was planning to use diffusers primarily on the ceiling and side walls behind the MLP. Ceiling height is about 9'2", so I should be no closer than about 5' away from any diffuser.

Well, I think the thing to do is start with big bass traps on the front wall corners and behind LCR speakers. I'll probably need to use small sections of 2" absorption behind the rest of the speakers to combat SBIR, since they will all be on-wall speakers. Maybe get diffusion going behind the MLP. Then listen and measure and see where I stand and decide how to proceed.

 

[bkeeler10]

Here are some shots from the EASE model, including ray tracing for first reflection points from LCR speakers to MLP.

 

[bkeeler10]

Interesting tidbit about my HVAC isolation efforts, which granted were not that extensive -- not enough space or budget to get really serious about it. Couldn't really do lined duct because of space. What I was able to do was have them install a resilient connection between the furnace and the new trunk that feeds the theater. This should isolate furnace vibrations from the ductwork.

I noticed the other day sitting in the theater with the A/C going, that I was getting what sounded like some air handling noise from above the theater door. There is a duct that goes through there and continues down the side wall. I can't hear it from the side wall forward of the door, but I can hear it quite well from the door cavity, and it appears to come from there when sitting in the MLP. I was not able to put the ceiling of that fur-down on clips, nor was I able to double up drywall there, due to space restraints.

I'm a little bummed about this noise. It's not super intrusive, but it's annoying that it's there. I could probably devise something to completely cover up the inset the door sits in for when the theater is in use and that would probably alleviate it. We'll see whether I get annoyed enough with it to do something like that.

The two supply vents coming into the room on the back wall are surprisingly quiet. As in, whatever noise they might be making is masked completely by the air handling noise I mentioned above. Some of it might have to do with the fact that I had them build bigger boxes close to the opening, so the supply dumps into a bigger space before hitting the vent cover. This should have had two benefits: 1) Slowing down velocity before the vent cover, to reduce turbulence noise; 2) There might be some end reflection working to keep equipment noise from coming into the theater.

 

[bkeeler10]

I'm not quite sure what to do about speakers at this point. I had been set on the Chane L series, but they are taking much longer than anticipated and it will probably be a few more months still before they hit our shores. I definitely want to try them out before making a final decision, which means I need to find some placeholders. Preferably speakers I'm interested in already, but could sell at little to no loss if I decide on something else.

The Revel Concerta2 series is an option, and I have connections there that may work out to a discount. I could also buy some Chane A series and keep them for surround duties when the L series is ready, using only the L7 from the L-series, for LCR. Still trying to decide on that.

The AVR will almost certainly be the NAD T758 v3. The UHD bluray player will be the Panasonic UB820.

Any suggestions for good banana plugs for 10 gauge wire? I found these at Parts Express: https://www.parts-express.com/parts-express-banana-plug-pair-compression-type--091-330. They accept 10 gauge wire from the side, but only 12 gauge wire and smaller from the back. I would prefer to wire from the back.

 

[Matthew J Poes]

First coefficient alpha. I’ll admit, it’s a little beyond me. I’m not an acoustical physicist. I took a few courses. This concept was a bit lost on me. It is supposed to be the measure of incident sound, a reflection. 1 is supposed to mean 100% absorption of the incident sound. Yet that isn’t true. When I did my tests, my approach didn’t require a full understanding of this or the math. I took a panel outside with a piece of plywood. I mounting a mic and speaker on a pole. I suspended the pole over the plywood. I measured. Then I added the panel and measured again. I divided the second measurement by the first. The difference was the change in the response due to the panel of the reflection. I used windowing to remove the direct signal.

In any case, when I first came across Tooles article discussing this I asked a professor friend. He gave me this explanation. If you covered a wall with 10” thick mineral wool, it wouldn’t be a soundproof wall. Sound would still transfer through the wall. Yet it would have an absorption coefficient of 1.0 down to a pretty low frequency. If you made a wall of that fiberglass, no drywall, it would be far less soundproof. A lot of sound would get through. Most of us get this, this is intuitive. Yet if it absorbs 100% of the sound, none should be left to pass through it to the other side.

I’ve had people not believe me on this and so one test I did to show was I placed a speaker a few inches from a panel I made which has no back. The panel is 6” thick and 8lb density minerwool. I measured with a mic a few inches from the other side. It only caused maybe 10-20dB of sound reduction. Significant but not 100%.

MLS stands for maximum length sequence. It’s an old 1D diffuser approach that relies on absorption between a sequence of virtually randomly spaced reflective surfaces. Because of the absorption, varying either width or length is similar to changing well depth. It’s not as effective as QRD or PRD sequences. Some also take issue with diffusion that includes absorption as they feel the definition of diffusion requires that 100% of the original sound energy exist in the sum of the diffused rays. Yet in an MLS diffuser, a significant portion has been removed from the room and converted to heat.

I like MLS in place of straight absorbers, but I don’t treat them like diffusers. I treat them more like alternatives to straight absorbers when planning a room.

Ok now for changing a rooms acoustics, my trick isn’t pretty. My wife hates it. I made panels with feet. They don’t hang on the wall. Then I mounted some Vicoustic MLS panels so they can hang over the main panel (which itself is more of a free standing bass trap).

I think you could maybe make a system that allows you to hang a reflector panel over the absorbers in the room. Basically, most of the rooms absorption is range limited below 300hz or so. Then above that point just have some discrete absorbers in key locations. Make reflector panels you can hang on the absorbers. Maybe Velcro, hooks, etc.

I saw a cool system that had small triangular panels. Each side was different. Absorption, diffusion, reflection. They rotated and were in rows next to each other. This allowed the rooms acoustics to be changed easily. It looked really cool too.

Then of course there is active room acoustics. If you crack that nut with simple diy products, let’s talk, I have a business opportunity for you!

 

[bkeeler10]

I also need to find a piece of glass to fill in the "peephole" for the projector box. I ran into this option: https://www.edmundoptics.eu/p/203.2-x-254-x-3mm-high-efficiency-window/5443/. Has anyone here had to find something like this for a hush box?

By the way, I'm very glad I will have the projector in a hush box. Reason number one is the noise obviously, and since I live at 4200' above sea level I have to run my JVC in high altitude mode. The fan noise is quite noticeable. The other reason is the projector heats up the room pretty fast, so having it out of there will be a good thing.

I will have to design a forced ventilation system for the hush box, but I think I have it sorted out already.

 

[Matthew J Poes]

I'm not quite sure what to do about speakers at this point. I had been set on the Chane L series, but they are taking much longer than anticipated and it will probably be a few more months still before they hit our shores. I definitely want to try them out before making a final decision, which means I need to find some placeholders. Preferably speakers I'm interested in already, but could sell at little to no loss if I decide on something else.

The Revel Concerta2 series is an option, and I have connections there that may work out to a discount. I could also buy some Chane A series and keep them for surround duties when the L series is ready, using only the L7 from the L-series, for LCR. Still trying to decide on that.

The AVR will almost certainly be the NAD T758 v3. The UHD bluray player will be the Panasonic UB820.

Any suggestions for good banana plugs for 10 gauge wire? I found these at Parts Express: https://www.parts-express.com/parts-express-banana-plug-pair-compression-type--091-330. They accept 10 gauge wire from the side, but only 12 gauge wire and smaller from the back. I would prefer to wire from the back.

I think those Revel are really good. Very well engineered speaker.

I would think 12 gauge would be fine. That’s what I used. I did measure resistance and inductance once to see, it was nothing too serious.

 

[bkeeler10]

In any case, when I first came across Tooles article discussing this I asked a professor friend. He gave me this explanation. If you covered a wall with 10” thick mineral wool, it wouldn’t be a soundproof wall. Sound would still transfer through the wall. Yet it would have an absorption coefficient of 1.0 down to a pretty low frequency. If you made a wall of that fiberglass, no drywall, it would be far less soundproof. A lot of sound would get through. Most of us get this, this is intuitive. Yet if it absorbs 100% of the sound, none should be left to pass through it to the other side.

Yes, this makes some sense and I had thought about it too. There are only three things that can happen to sound impinging on a boundary: Reflection, absorption and transmission. And of course all the original energy must be accounted for in some combination of those three things. Perhaps what's going on with an absorption panel is a transmission of some of the sound to the hard boundary behind it, a reflection off that boundary, and then some transmission back through the panel and out into the room. So it's not reflecting off the absorber itself. Still doesn't fully explain the absorption coefficient issue though. I'm gonna have to think some more about this.

I’ve had people not believe me on this and so one test I did to show was I placed a speaker a few inches from a panel I made which has no back. The panel is 6” thick and 8lb density minerwool. I measured with a mic a few inches from the other side. It only caused maybe 10-20dB of sound reduction. Significant but not 100%.

This is a common misconception - that placing absorption on a wall equates to improved transmission loss across that wall. In reality it does virtually nothing when it comes to transmission loss. It does of course help somewhat inside a wall cavity, reducing resonance.

 

[Matthew J Poes]

I also need to find a piece of glass to fill in the "peephole" for the projector box. I ran into this option: https://www.edmundoptics.eu/p/203.2-x-254-x-3mm-high-efficiency-window/5443/. Has anyone here had to find something like this for a hush box?

By the way, I'm very glad I will have the projector in a hush box. Reason number one is the noise obviously, and since I live at 4200' above sea level I have to run my JVC in high altitude mode. The fan noise is quite noticeable. The other reason is the projector heats up the room pretty fast, so having it out of there will be a good thing.

I will have to design a forced ventilation system for the hush box, but I think I have it sorted out already.

I have no experience but my understanding is that you want a good coated optic glass panel mounted at an angle. I researched this pretty heavily at one point but then backed out when I saw the cost and ventilation concerns. Someone also suggested going with two pieces of glass. I guess that is how pro-rigs are setup and it provides more sound isolation.

I will be curious how the hushbox works for you. I had wanted to do one, and it’s till high on my priority list. My projector is my highest noise floor at the moment.

 

[bkeeler10]

I think those Revel are really good. Very well engineered speaker.

I would think 12 gauge would be fine. That’s what I used. I did measure resistance and inductance once to see, it was nothing too serious.

I'e already got 10 gauge in the walls. I could have gone 12 gauge and it would have been fine, but I went a little overboard. Not a bad thing, unless I can't find good banana plugs for it.

 

[bkeeler10]

I have no experience but my understanding is that you want a good coated optic glass panel mounted at an angle. I researched this pretty heavily at one point but then backed out when I saw the cost and ventilation concerns. Someone also suggested going with two pieces of glass. I guess that is how pro-rigs are setup and it provides more sound isolation.

I will be curious how the hushbox works for you. I had wanted to do one, and it’s till high on my priority list. My projector is my highest noise floor at the moment.

Mine is built of a single layer of 3/4" MDF (STC 29), and is open to the room behind it, so it is a huge sound hole into that room. Which I'm not as concerned about as the other adjacent rooms. But it should be sufficient to reduce projector noise down to below the noise floor of the room I would think. I may have to consider two layers of glass to maintain that sort of STC. I just don't want to lose too much light. Anyway, I'll keep looking around.

 

[Matthew J Poes]

Interesting tidbit about my HVAC isolation efforts, which granted were not that extensive -- not enough space or budget to get really serious about it. Couldn't really do lined duct because of space. What I was able to do was have them install a resilient connection between the furnace and the new trunk that feeds the theater. This should isolate furnace vibrations from the ductwork.

I noticed the other day sitting in the theater with the A/C going, that I was getting what sounded like some air handling noise from above the theater door. There is a duct that goes through there and continues down the side wall. I can't hear it from the side wall forward of the door, but I can hear it quite well from the door cavity, and it appears to come from there when sitting in the MLP. I was not able to put the ceiling of that fur-down on clips, nor was I able to double up drywall there, due to space restraints.

I'm a little bummed about this noise. It's not super intrusive, but it's annoying that it's there. I could probably devise something to completely cover up the inset the door sits in for when the theater is in use and that would probably alleviate it. We'll see whether I get annoyed enough with it to do something like that.

The two supply vents coming into the room on the back wall are surprisingly quiet. As in, whatever noise they might be making is masked completely by the air handling noise I mentioned above. Some of it might have to do with the fact that I had them build bigger boxes close to the opening, so the supply dumps into a bigger space before hitting the vent cover. This should have had two benefits: 1) Slowing down velocity before the vent cover, to reduce turbulence noise; 2) There might be some end reflection working to keep equipment noise from coming into the theater.

It’s always the way. Something always goes a little wrong. I have so many little issues. I did use liked ducts and lots of isolation methods, but still ended up with some hvac noise issues. My biggest problem remains that the total transmission loss through the duct is not high enough. One of these days I should try to measure it. There are specific ducts that must be a straight path. One is in the closet of my bedroom and another is in my daughters bedroom. For whatever reason, a movie played back at “reference” levels can be heard during dynamic peaks through the vents. My wife claims she can even understand the dialogue at times.

Another dumb move on my part was I cheaper out on decoupling clips in key locations. Everything I did used rubber or urethane grommets for resilience/isolation. With loud bass scenes it is sufficient to shake the room beyond the travel of the grimmest and transfer to the house. I asked a guy at Kinetic about this and he told me I should have used spring isolators. That they always use spring isolators on the main stud walls and ceiling for exactly this reason. I didn’t realize it would be such an issue (but admittedly, that would have added a ton of money to the cost of the room isolation). Live and learn I guess. I knew it was preferred, but didn’t realize the real world effect.

 

[Matthew J Poes]

I'e already got 10 gauge in the walls. I could have gone 12 gauge and it would have been fine, but I went a little overboard. Not a bad thing, unless I can't find good banana plugs for it.

Oh I see.

I have a bunch of Dayton banana plugs sent as samples for an article. I should see if any would be a good recommendation for you.