CR Treatment and Tuning---The home stretch!!

As the saying goes: "Pics, or it didn't happen"... Thus... : It DID happen! Looking very nice, too. Fully floated speakers, perfectly aimed, perfectly symmetrical... Nice work, Frank! :thu: - Stuart -

Some shots of progress for morale sake. :blah: We have the lower hangars, and baffle boards in production!

:thu: Looking good! - Stuart -

Frank has been a busy boy! Speakers are fully floated, soffit interiors are complete, with hangers above and below, insulation loosely packed around the speaker enclosures, and on the baffle extension.... So next up will be the baffles! He's working on those right now, so stay tuned for the next update... It looks EXCELLENT Frank! And the latest REW data also looks great. - Stuart -

Another day another milestone.......Test fitting the Baffle before finishing it.

Both baffles are up, and there's some new REW data, for those interested in understanding what baffles do, and how the room is progressing with that, acoustically. First, the graph that everyone looks at but isn't really the most important: Frequency Response: The turquoise color curve is before the baffles went on, and the purple curve is right after the baffles went on. You can clearly see them doing their magic, boosting the power below about 600 Hz by about 5 dB and smoothing the response in some key areas (notably around 500 Hz). There's also a slight lift and smoothing in the highs. Then the waterfall for the bottom end of the spectrum (lows and low-mids). In this case, I overlaid "before" and "after" onto the same graph. The turquoise curve is before the baffles went on, and the purple curve is right after they went on: You can see how modal things have smoothed out a bit in the time domain. For example, at the spot highlighted by the cursor at 113 Hz, there was some modal ringing going on there that is now attenuated. Ditto around 54 Hz, 59 Hz, 84 Hz, and a few other places. But the really interesting thing is in the low mids, where we got that 5 dB power boost, there was no change in modal stuff! So that's a pure intensity increase (from fixing the power imbalance inherent in all small speakers), with no modal penalty. Then the really nice one that shows some great precision workmanship by Frank. This shows the DIFFERENCE between the left and right channels, smoothed to 1/3 octave, which is how the specs say it should be measured. Wherever that gold-colored curve rises above the "0 dB" line, the left speaker is louder at that frequency, and wherever it falls below 0, the right speaker is louder. As you can see, the line is pretty flat! That implies that both channels are producing the exact same thing, with no differences. But that line is so flat that we have to zoom to see the details... Notice the scale up the left edge of the graph: Instead of show a range of +/- 30 dB, it is now zoomed in to show only +/- 7 dB, and the line is STILL flat! So we need to zoom in even more, and take some actual measurements of that curve. Sorry that this image is so big that it blows the margins of the post, but it's the only way to see the level of detail necessary to understand what Frank has achieved here... Note the scale: each division vertically is now only 2 dB. I have highlighted the entire spectrum with that lavender-colored measuring tool, and if you scroll across to the right, you'll see the actual measurement numbers. It says that the range of variation is about 1.2 dB. Thus, the variation is is about +/- 0.6 dB. The most stringent specs for control rooms call for this to be about 1 dB, but Frank has gone way better than that, and is getting just 0.6 dB. There is no way that your ear could ever discern such tiny variations: the minimum change that you can hear is about 1 dB, if your hearing is in perfect shape, and under optimum conditions. So even if you have perfect hearing, and you were to go sit in Frank's chair, you would be totally unable to hear even a vague hint of any difference between the channels, no matter how hard you try. In other words, Frank's room has near-perfect symmetry, and is producing a perfect stereo image, with the cleanest possible sound stage, exceeding the toughest specs for control rooms in this aspect. But we ain't done yet! :) There's still quite a bit that we plan to do to this room. The next big thing will be the desk, and of course that will mess up some of what we have achieved here so far, simply because it is a large solid, reflective object in a small room, but there's some tricks up my sleeve still for designing the desk to minimize problems, and then to treat the remaining untreated parts of the room to help with that... Congratulations, Frank! You've done a pretty darn good job of getting that room symmetrical. - Stuart -

A pic of both baffles after testing... :mrgreen: Now I gotta finish em...

So here is the rough cut of my desk for testing purposes. This will prove to be the final tug of war between Acoustic Engineer and Sound Engineer... :cen: Form vs. function....Will I have to comprise awesome work flow for accurate sound????? Time will tell.... :cop: Having left the realm of sensibility with Stuarts desk design, morale is holding out for now as I craft my dream desk design. :love: But how long can it last and how much of my shenanigans will Stuart allow???? :ahh: Stay tuned as the man likes to say!!! :snack:

Today's episode. Can't wait to see it all trimmed out.....

Hi Stuart.....:poke: Ready for more action... :jammin:

Well....Initial desk testing is not yielding good results. looks like I'm stuck on that until we get the cloud and the rest of the treatment done. Bummer... :( If Stuart gets me the details on the slats over the doors today, I should have some pics of that over the weekend...nothing else for me to do at the moment.

Check your e-mail, Frank. I sent you the design details for the slot walls above the sliding doors.... Time to dust off your table saw and carpenter's pencil! - Stuart -

More like clean off the saw dust! Gotta be 703 in the back? Can't get that stuff till next week due to a national holiday here.... :(

- Stuart -

I'm confused....The picture shows 3" of rigid...That's what I'm asking about. I can't get rigid insulation till Tuesday next week. Wanting to know if it has to be rigid, cause I'll have to wait till then to do the final assembly. Sorry if I'm getting on your nerves, but I need to know. Also, can you give me a heads up on any special insulation I'm going to need for the rest of the project? All we have left is the cloud and the wall under the window after the slats I think. getting special insulation takes a few hours round trip and I'd like to make it just one if need be.

Hi Stuart, Here is the trim I was planning on doing around the baffles. Need to make sure it won't cause any issues.

Wow guys :shock: This is really impressive work. The graphs speaks for themselves +/- 0.6 db is insanely hard to achieve. And the aesthetics of the room is just marvellous. Really really impressive !! All the best Jakob

Here is the trim I was planning on doing around the baffles. Need to make sure it won't cause any issues.

Looks like it should be OK, but do round the edges that face towards the speaker itself: Sharp edges are sources of edge diffraction. OK, yes, that trim is a long way off from the acoustic center, and out at 90° off axis, so there's not much going on there at mids and highs, you'd think, but there's still something, and there's always reflections and the diffuse field to deal with. I think I've mentioned this before, but if you can do ten things in your studio that each make a difference of 0.5 dB, then you made a difference of 5 dB! :) So that's fine, just round the edges. Get out your trusty, reliable, accurate, stable router! 8) (For those following this thread that didn't hear about it, Frank's router played a nasty trick on him, and nearly trashed one of his speaker baffles...)

That's what I'm asking about. I can't get rigid insulation till Tuesday next week. Wanting to know if it has to be rigid, cause I'll have to wait till then to do the final assembly. Sorry if I'm getting on your nerves, but I need to know.

I've been in bed with the flu the entire weekend since Friday, thus not very responsive. This insulation is fairly important, as these two slot walls are aimed at fairly low frequencies, so we need stuff that has high coefficients of absorption in the low-mid and low frequency range. 701 and 703 do. So do some others, but it's hard to say for sure if what you have is the right stuff without knowing what the exact acoustic characteristics are. If you have a link to the acoustic specs page for the product you have on hand, and it shows numbers around 0.5 or higher at 125 Hz, then you should be OK. I show 3" in the model, but if you need to go 3.5" to get that, then that's fine too. Here's some that do: - Owens Corning: Sound Attenuation Batts, OC-701, OC-703 - Roxul: RXL 40, RXL 60, RXL 80, Safe'n'Sound, AFB, RHT-40, RHT-60, - CertainTeed: OEM 600 - Fibrex: FBX 1240, FBX 1260, FBX 1280 - Rockwool: RW-5 (Although that's a bit heavy) Etc. Any of those would be fine, in either 3" or 3.5" if needed.

Also, can you give me a heads up on any special insulation I'm going to need for the rest of the project? All we have left is the cloud and the wall under the window after the slats I think. getting special insulation takes a few hours round trip and I'd like to make it just one if need be.

Not sure yet. For the cloud, you'll need about 50 ft2 of 3". Perhaps something similar to the above, but I'm thinking of going with an FRK or FSK: Johns Mansville IS 600 FSK would be great, if you can get it! It only comes in 2", I think, but we could put 2" of that with the FSK side down (facing the room) and an inch of something else above it (701, pink fluffy, etc). Ottawa Fiber OFI-48 FSK would also be good, but also comes only in 2". The best: 3" OC-705 FRK would be excellent. All of those have good absorption in the low end, but less in the mids and highs, due to the facing, which is exactly what we want up there. We'll use a thicker fabric (or maybe thin carpet) just under your finish fabric, to take the edge off the very high end, which is still a bit bright in your room as compared to the low mids, but the cloud is mostly going to do some more for the low end, as well as deal with some reflections. So look around and see what you can find in FRK or FSK faced insulation locally, and let me know so I can decide on that. For the part under the front window, between the soffits: that's not too important: we can use whatever is left over from other treatment. We'll only do that after we get your sub in its final location, and tuned, as that's roughly where the sub will be, and we'll need to damp that space one the sub is in. And for the part above the window: that's my final "wildcard"! Not sure what's going in there yet. It might need something, but I really can't say yet until we get to the REW tests at that point. In the model, I put in a nondescript absorber panel as a place-holder, and it might turn out to be something like that, but it might be different. That's the last bit of bare wall space left over, so that's what will o the final tweaking, if it is able to do that.... we'll see! OK, here's the thing: after the CR is done, there's still the re-tuning of the LR, so you'll need some more insulation for that. You might as well buy a bit extra of everything now, so you have it on hand for the LR. One thing I should mention: the CR is in the final stages of acoustic tuning, so the things you do now are not going to have major, mind-blowing effects on the acoustic response. This is just tweaking. The could will have a nice effect, yes, and the desk will have a not-so-nice effect (it always does...) but the slot walls above the sliding doors, the space below the front window, and he space above the front window are not going to make huge differences. I just wanted to warn you about that, so you don't get disappointment when the lines don't all go dead flat after you d a lot of work carefully cutting and placing slats with millimetric precision... - Stuart -

This is really impressive work. The graphs speaks for themselves +/- 0.6 db is insanely hard to achieve. And the aesthetics of the room is just marvellous. Really really impressive !!

Thanks for the kind words, Jakob! Your room will be able to turn out something like this, for sure! I'm ready to put the final touches to the design for you.... as soon as you are ready! :) Not far to go now... Just waiting for your input on the final dimensions of the stair case, after the move... :) - Stuart -

Hi Jakob, If anyone can bring out the best in your space, its Stuart. Your in good hands no doubt...Thanks for the kind words also. Its by far the hardest thing I've ever done in my life when you factor in the cost, time invested and challenges faced over almost 4 years doing the construction mostly myself. I had the slab poured,stucco done, and hired a guy to help me build the building itself (done in 6 weeks as opposed to the 3+ years on the interior by myself!) Crazy... I'm almost done at long last, and its kind of surreal... Good luck with yours!

That nasty router incident was really an issue of trying to use a shank that was just too small a diameter for the job of cutting a 2" depth. Also, the cutter was garbage. I got it off of ebay and now i know why its hard to find a 3/8 radius cutter with a 1/4" shank and a 2" cut depth...Cause they don't work! Go 1/2" shank on jobs like that! Fortunately I stopped before the bit tore too far into the edge, but it made things look ugly for a minute! :roll:

Hi Stuart, At this point I'll just pick up some 703 tomorrow and also buy what I can for what we know. I know I can get 703 all day probably faced as well. I'll have to check on 705. I can't get any of the other products easily without longer waits and shipping charges, so that's kind of a non starter. No matter though. Can I get away with 703 in the cloud if need be? I can buy tons of 703 for sure.....

Actually I think I answered my own question. According to the data sheet, 703 2" FRK has a coefficient of .63 down at 125 Hz...So, I can use some combination of 703 FRK and un-faced to achieve the results. I will probably buy 1" material for versatility... Also, I don't see it in the data sheet, but I'm pretty sure that 703 is 3lb/sq. in. and 705 is 6lb/sq. in.

According to the data sheet, 703 2" FRK has a coefficient of .63 down at 125 Hz...So, I can use some combination of 703 FRK and un-faced to achieve the results.

:thu: Yup! Get the 2" 703 FRK for the underside of the cloud, and get some 1" 'whatever' (not critical, but not too dense) for above that, to make up the 3". For the cloud, the insulation can't be thicker than 3", because that's 2x4 framing, and we need a slight gap there, to make sure the insulation doesn't bulge down over time, pushing out the face of the fabric, and making it ugly. So, from top to bottom it will be: Hard back - 1" of "something" insulation, 2" of 703 FRK with the paper facing DOWN (towards the room), then the air gap (with straps, or mesh, or whatever to hold the insulation clear of the fabric), then some thin carpet or thick cloth to take the edge off the high end (I'll give you more details on that later), then the final finish fabric You won't need plastic on this cloud, because the FRK does the same job even better, plus the carpet, plus the finish fabric. No chance of fibers getting through that lot!. Don't forget that I modified the cloud with the updated soffits, and I'll need to do some more minor mods so the cloud will fit in with the updated slot walls, so don't build the cloud from the original plan! It's rather different now... :) I'll send you the final version when I'm done updating the update of the update... - Stuart -

Sounds good....Yeah I had the mods in mind. Shouldn't be a major difference fortunately. I'll just use my screw and fender washer technique for retaining the rigid stuff. One other question...Do i need to go with MDF on the backing for the cloud? It adds considerable weight which makes installing it harder and a bit more dangerous.