Kendale's Studio (Acoustic Treatment for Temporary Location)

[kendale]

I am temporarily located in the “family room” of my home with a floor plan of 20’ x 12’ x 8’ ceiling @ wall up to 10’ ceiling crest, hardwood flooring over post & pier construction. The walls and ceiling are gypsum/sheetrock.

There is a 6’ x 4’ picture window with a honeycomb window treatment (curtain) located on the front wall where the console is located, and a 8’ x 7’ sliding glass door with cloth inserts in plastic vertical shades at the rear of room.

The console (Soundcraft Ghost/Argosy7032G, Mackie HR824 monitors on console) is located up against the front wall, with a large hardwood wall unit/bookshelf (9’6” x 22” x 7’) on the left wall, Spire equipment rack (7’ x 24” x 35”) on the right wall, with guitars hanging on wall above equipment rack.

Here are some of the RTA measurements taken of room so far:

20 0
25 0
31.5 0
40 0
50 +2
63 +4
80 +2
100 0
125 0
160 0
200 -1
250 -1
315 -2
400 -2
500 -1
630 -1
800 +2
1K +5
1.25K +6
1.6K +2
2K 0
2.5K 0
3.15K 0
4K 0
5K 0
6K 0
8K -3
10K 0
12.5K 0
16K +2
20K 0

Given this temporary situation, data and photos, what recommendations would you all suggest regarding acoustical treatments, please?

Thanks!

[knightfly]

Don't see any photos, but that sounds pretty flat - although 1/3 octave won't tell the whole story. You also didn't mention whether one or both speakers driven, mic position, or any other details of the test so it's hard to comment.

The glass in front and behind should be causing you all sorts of flutter echo -

Monitors should NOT sit on the console but behind, placed on heavy decoupled stands - console placement causes early reflection problems in most cases, unless the console is slanted down in front a LOT.

Distance to wall behind speakers will change response drastically - there is a wall bounce calculator on the Acoustics forum that's fun to play with (needs Excel)

Moving either speakers or your head by as little as an inch or two can sometimes make drastic changes in response, due to modal peaks and dips; here's a useful calculator for figuring this.

http://www.harman.com/wp/index.jsp?articleId=131

I cut and paste the length and width graphs alongside a scaled room diagram (after scaling them to the same size as the walls) and draw red lines across the room where peaks and nulls are, then green lines where there are NO peaks or nulls - anywhere there's a green intersection is a candidate for speaker or head placement, keeping in mind you need plane symmetry in a mix room (head in center side to side) and an equilateral triangle for speaker/head placement (or at least an Isoscelese triangle)

Just read that back, if you're as confused as I am I'll try a sketch for you -

Can you try the pix again? Less than 150k file size, JPEG is best, please keep width down to 750 pixels to avoid side scrolling when reading text... Steve

[kendale]

Let's see if this works...okay!

RTA was done with one speaker.

I was hoping to build some sort of treatment for the front wall that I could take with me to the new location in the future, and didn't really want to stick a piece of foam there. Any suggestions, designs?

I have also been looking for a good pair of speakers stands. any suggestions on which brand and/or placement? I did find a pair of stands 42" high. Would that be about right?

Thanks for the link to the Room Resonance Calculator. Which figure do I enter for the room height being that the ceiling slopes upward from 8' at the wall to 10' at the center of the room?

Thanks again!

[knightfly]

42" stands are almost perfectly WRONG for your application - that would put the centers of your woofers almost exactly at HALF your ceiling height when close to the wall, which would cause a fairly deep null in response at around 70 and 212 hZ, and peaks at around 140 and 280 hZ. If you pulled the speaker location away from the wall enough, you could get them out of that dead center vertical location -

Although you didn't mention which way the ceiling slopes - I'm hoping it's up to your rear as you face the speakers?

IN the pic, those two light areas on either side of the console - are those from lights, or is there a door on one side? Those two corners should have some corner traps as one of the first things you do.

Here's a page with some DIY ideas on traps, and their suggested locations within a rectangular room -

http://www.johnlsayers.com/HR/index1.htm

Room height for the calculator should be taken at the speaker location -

Left/right room symmetry (at least within a foot or two of ear height) is important for good stereo imaging, and that glass-faced cabinet can't be helping - if there is any way to move it more to your rear...

OTOH, the dog looks like a promising upper bass absorber, but needs to be closer to the back wall Steve

[kendale]

Aloha Steve and thank you for your replies. I can see why so many others have posted favorable reports to this forum.

Okay, so the 42 inchers are out. Being that the console shelf stands 36" I'll be looking for something closer to that.

Yes, the ceiling slopes upward from the front wall over the mix position.
The two lights in the corners were to shed some indirect lighting to help the photo turn out better. I'll check with a friend of mine to see if he can build those corner bass traps and wall absorbers.

I'm afraid that the wall unit is non negotiable at this point. Perhaps I should consider it to be one of the walls and place some type of treatment in front of it?

The problem with the dog is that she keeps moving around from room to room.

Mahalo!

Ken

[knightfly]

Aloha Ken, are you on Oahu or one of the other islands? 'way back in 1973 we lived on Oahu for about a year and a half, out in Hauula, while I was Service Manager for a Pro audio and video company (no longer in business - not my fault, really )

Not sure how much luck you'll have finding the right material for absorption in the islands - generally we hit the yellow pages under insulation contractors and call ALL of them til we get one who will sell us the industrial types of insulation without having to buy a boxcar load - I did a search on 'em, came up with this

http://directory.superpages.com/listing ... RC=portals&
T=Honolulu&S=HI&STYPE=S&CP=Construction+%26+Contractors%5EBuilding+%26+Home +Construction%5ESpecial+Trades+Contractors%5EPlastering%2C+Drywall%2C+%26
+Insulation%5EInsulation%5ECommercial+%26+Industrial&RC=1

(you'll need to put that link back together by removing the space after home - it's so long, it would have caused you to have to scroll left/right to read the rest of the text)

What you need to ask for is either rigid fiberglass, such as Owens Corning 703 (un-faced) or rockwool, mineral wool, somewhere between 2 to 4 pounds per cubic foot density; Johns Manville and Knauf also make similar products.

This stuff is cheaper and more absorbent than the acoustic foam some music stores sell, and it's 3-4 times as effective as the looser, typical home insulation batts. Here's an idea of what it looks like -

http://www.idimn.com/products/ins/fiber ... m_ind.html

And if you have lots of money and absolutely can't find things anywhere else, here's a pre-made version - not as thick as I'd like, and really not practical for your situation due to cost, shipping, etc - more just for comparison -

http://www.auralex.com/sound_absorption ... anels4.asp

For your application, a movable panel about 4" thick would help the wall unit "disappear" acoustically - it could be moved against a wall somewhere when not in use. Same for the front wall (behind the speakers) - and again behind you, if that's a glass surface.

For serious mix decisions, you would need to take the guitars out of the room and do some sort of half-height free-standing panel of this stuff that could sit on the rack to your right - this would help stereo imaging (the half-panel) and smooth out frequency response (acoustic guitars make great tuned resonators, even if you were to slide a piece of felt or foam under the strings - nearly impossible to get a true sound field when they're in the room)

Here's my (stereo, sorta) bass trap - the guy on the right weighs 160 pounds and stands 31" at the shoulder - those are heat lamps on a thermostat set at 60 degrees (did I mention dobies are wusses?) Still, notta lotta problems with theft... Steve

[kendale]

Aloha Steve,

I am on the Kohala Coast of the Big Island. While I do like the pace of life and less traffic it offers, it does make finding some products a bit challenging.

Was that A/V company Rhema Sound by any chance?

Thanks for the links. It helps to know what I'm looking for looks like. I tried to attach the results from the Room Resonance Calculator link but I dont think I quite got it figured out yet. I'll keep working on it. The Auralex product looks nice. What are your thoughts on RealTraps?

I like your 300 lbs of stereo bass trapping! I'll bet they eat more than bass alone, though!

Mahalo!

[knightfly]

Yeah, any island is nicer than Oahu for the most part -

I actually was service manager for two companies simulaneously, one was Electronic Measurement Corp and the other was Pacific Video Sales - pretty sure both are gone. Offices were on Ualena St. out by the airport.

I've yet to use Real Traps, but have seen quite a few positive comments on the Mini's - If you're at all into DIY, though, you can beat price AND performance of just about ANY commercial unit...

Yeah, my "traps" have been known to improve the "treble" response of certain individuals under some circumstances The smarter ones just go somewhere else... Steve

[kendale]

After looking over the DIY ideas on traps I've got a couple of questions...

Regarding the front wall absorber: slats or no slats?

Regarding the "mdf" material: will substituting 3/4" plywood affect the performance of the units? Would the plywood act as a resonator? (considering furniture grade birch plywood for esthetic reasons or is there mdf material with a laminate finish available?)

Mahalo.

[knightfly]

For front absorbers, since they are pretty close to the mix position, unless you're building a front wall that's angled for RFZ I wouldn't recommend slats - too much chance of mid/high freq. early reflections. If you could build slats that were angled enough to reflect AWAY from the mix position, and that reflection path then became long enough before returning to your ears to exceed about 20 milliseconds (around 22 feet), then it would be OK to use something more reflective.

MDF is denser than plywood, so would have a lower resonant frequency - either panel will resonate, but the stiffer/denser you make them, the less (and lower frequency) the resonance. Are you talking about the rear panels of the free-standing traps? These don't even show -

I'm not aware of any specific MDF that's laminated already - although if the size worked out and you could find some "blems" of solid core wood exterior doors (not the fancy ones with wierd panels and windows) they would be massive enough to never worry about this... Steve

[kendale]

"unless you're building a front wall that's angled for RFZ"

Actually, I was considering using the front wall absorber and the two front bass traps to fit together like a new front wall.

"MDF is denser than plywood, so would have a lower resonant frequency - either panel will resonate, but the stiffer/denser you make them, the less (and lower frequency) the resonance. Are you talking about the rear panels of the free-standing traps? These don't even show.
"
I was refering to the rear wall and side pieces mostly, being that I was intendeing to use the two side absorbers and the rear wall unit (not pictured) as movable, free standing units, the sides and facing edges would be in plain view. MDF is fine, just wondering and trying to keep the mrs.

[knightfly]

Looks like you're on the right track there - I wouldn't do slats for the front of room absorbers, but they're fine on the sides where you're showing them - they'll also be needed at the rear to kill reflections off the glass there... Steve

[kendale]

Moving to Construction Forum http://johnlsayers.com/phpBB2/viewtopic.php?t=4091

[chelscaldwell]

Acoustic room must be in a quite place. Surely you wanted to sound proof the room you will use, soundproofing requires you some time and a few hundred bucks for sound proof board panel, but all can be a worth your effort.

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[Soundman2020]

" chelscaldwell", why are you posting on a thread that has been inactive for ELEVEN YEARS? And why are you posting totally irrelevant comments? Only spammers do that, normally...

- Stuart -