Attic Shaped Studio

#526

coolio. be interested in what happens if you turn down the 55hz

#527

gullfo wrote:Source of the post coolio. be interested in what happens if you turn down the 55hz

That would indeed be interesting! But I think there is still plenty scope to address this with room treatments as there is virtually no treatment on the side walls of the room at the moment and 50Hz is the primary width mode. There's only a few 50mm thick panels on the right hand side, which will have no effect around 55Hz. For practical reasons I have to finish the ceiling and flush mounts first :-)

Next big problem to solve is the ETC peaks around 3 and 9ms. The 9ms peak correspdonds to a reflection from the speaker->far side wall->listener. That's resolved by placing a 100mm thick absorber on the door and equivalent position on the other side.

I suspect the 3ms peak is at the 2.5 corner around the top of the door/soffit area. Hopefully will be solved by a 200mm thick soffit type absorber on the ceiling/wall corner, like the big green ones to the far left and right of the ceiling here. These might also help with the ~50Hz resonance as well.

#528

Once of four space couplers built. The ends are angled to fit closely into the sloped ceiling.

I made this jig from offcuts to allow routing of about 20 of the strips at the same time.

A few of the lengthways pieces.

All the crossways pieces.

The plywood was nominally 9mm thick, but closer to 8mm in reality, so I used an 8mm router bit to cut the notches then sanded the notches to widen them a bit. This permitted a very secure friction fit, no glue necessary. However it did introduce a slight bow over the length of the 1.64m finished coupler. Unexpected but no big deal in practice. I think over the 60x60cm standard size of these units it wouldn't be noticeable.

#529

uh oh... off by a millimeter... you're slipping :cop:

LOL, really excellent work. and yes, spending the time to create a jig when doing lot's of precision repetitive cuts is really the way,

#530

gullfo wrote:uh oh... off by a millimeter... you're slipping

Excellent! Speaking of millimetre tolerances, ripping the plywood sheets lengthways into the 76mm wide strips was quite challenging with the circular saw. And the mini circular saw at that, my normal sized circular saw gave up the ghost halfway through cutting the first strip

I ran the saw fence along the straight factory edge of the plywood sheet to cut the 76mm strips and get another straight edge, but of course slight saw variations from my cuts accumulated quite quickly after a few strips. Solved by making the next cut using the factory edge of another plywood sheet, but took a bit of time. My new circular saw has a better fence so that might be less of an issue next time.

Cheers!
Jennifer

#531

Space couplers in place!

I ran out of danish oil so one of those remains unfinished for the moment. They had to be in place for a big recording session so there wasn't enough time to get and apply and another can before installing. A bit annoying, but there it is!

View from below.

The second from left recess shows the fabric covered absorbers before the space coupler is added below them. The space coupler has wadding on top of it to give a diffuse covering and hide the "cushions stuffed into a corner" effect of these absorbers. The far left recess has the same fabric covered absorbers with wadding applied under them, rather than above the space coupler. I didn't use this method in the end because it was time consuming and awkward to apply and didn't work any better.

The wadding is held in place above the space couplers with strips of wood at either end.

The wadding is folded over the strips and stapled. This makes sure it goes flush to the walls of the recess, looking proper and prevents any stray insulation fibres from falling through.

The very high orchestral mic stands hold the space couplers in place while I screw them into the ceiling.

Cheers!
Jennifer

#532

really spectacular results!

#533

It looks awesome! Really curious to see if there is any difference in measurements with and without the space couplers, and, of course, you to tell us if there is any audible improvements.

Cheers,

Eric

#534

ericwisgikl wrote:It looks awesome! Really curious to see if there is any difference in measurements with and without the space couplers, and, of course, you to tell us if there is any audible improvements.

Of course! Subjectively, the my ears tell me the frequency response in area below the absorbers and space couplers is more even than it was before. A recent drum recording under that area sounded excellent, best drum recording in the room to date. It would fit right into a mix without EQ, added ambience or anything. The ride cymbal sounded particularly amazing. Vocals recordings also sounding really good, in fact the singer mentioned it was better in here than in the usual other room, which has a similar shape but not this ceiling treatment.

More objectively, here are some graphs.

Raised ceiling with absorbers (blue) vs raised ceiling with absorbers and space couplers (red), left:

right:

Full range versions of the above with var smoothing, left:

right:

Untreated raised ceiling (black) vs ceiling with absorbers and space couplers (red), left:

right:

#535

I'd be interested to hear people's thoughts on the effect of the space couplers. I've attached the REW file for anyone who wishes to look into other aspects of the measurements.

Cheers!
Jennifer

#536

one thing to note - the number of phase shifts with the couplers + absorbers is way less than without. :-)

there is also marked reduction in the "heat" around the 300-400hz (mud-into-boxy) range. so mostly ±5db below 100hz and flatter ±3db above. as an experiment - you could try (using a parametric eq setting on the speaker feed) cutting 54hz down say 1.5db - 2db and see what happens to the 108hz, 160hz, 212hz etc as that could flatten things more.

#537

Thanks Glenn. Yes, that improvement in the mud into boxy range is a real benefit, and presumably one of the reasons I don't feel the immediate urge to reach for EQ to scoop out a bit of the midrange in drums in that recent recording.

Something I'm intrigued about with the space couplers + absorber versus only absorber is the broadband nature of the increase in absorption from the space couplers. It's a slight increase but almost full range, very worthwhile I think, especially since it hasn't decreased the RT60 in the way adding more absorption would.

Total area of these ceiling treatments is just under 3m², about the same as four standard 4x2' panels, a pretty good result for such a relatively small area I reckon.

Cheers!
Jennifer

#538

the space coupler works simply because the acoustic energy has no where to go except within the confines of each "chamber". so incident angle into absorption is always (almost really) 0° which is ideal (almost always) for a depth-based plain old absorber (POA). so in effect there is no "suboptimal" incident angle into the absorption, hence a decent increase in efficiency. John Brandt uses a fairly large set of space couplers in nearly all of his studios for this reason (i've helped build some of his).

#539

Cheers Glenn, it's great when theory and practice align. Given the effectiveness of space couplers and their relatively cheap and simple material and build cost, I'm surprised they are not used more often.

Cheers!
Jennifer

#540

my guess - people sense of aesthetics... in my larger designs, where i have large coupled spaces, i'll use them to bridge them to direct the acoustic entery into the absorptive space, but they're typically hidden behind clouds or hanging polys / panels etc.

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