Looking for a sanity check on my acoustic treatment strategy...

[Wiggum]

Hey all,

 

I recently moved into a new apartment, and I'm using the master bedroom as a project studio. In short, the room sounds terrible. I am just a hobbyist, but I would like to improve the sound of the room.

 

I am primarily a keyboard player, so most of my tracks are recorded direct. I would like to add the occasional bass guitar or acoustic guitar, but overall, I need a good room for monitoring and mixing.

 

The room is 12'x15', with typical, thin apartment carpeting and a 5'x5' picture window. My synths are along a full wall (with a door to the side), my DAW is in front of the picture window, and a worktable with various gear is against the other wall (forming a 3-sided cell). My synths sit on an Apex stand, and a pair of Event PS-8 monitors sit atop 42" speaker stands filled with shot (the speakers sit 4" above the synths, and 4" back). The speakers and stands are a foot off the wall. There is an armoir in the back of the room, and a TV and cabinet in the corner.

 

My plan is as follows:

 

1) Move DAW CPU to walk-in closet (reduce noise)

2) Cover main walls with Auralex 2" pyramid foam, in staggered checkerboard fashion (2'x4' sheets)

3) Auralex LERND bass traps on stands in the corners of the room

4) Thick curtain for picture window (vertical blinds to remain as well)

 

Since this is a temporary living situation, I don't want to destroy the walls with glue. I am considering mounting the auralex on plastic corrugated panels, and tacking it to the wall. Or I may just tack the foam directly to the wall.

 

So is this a sound strategy? I've read the Auralex articles, and some other features on the net, and I've tried to make sense of F. Alton Everest's books. I don't have the time or resources for mathematically analyzing the room, but I need a common sense strategy for improving the acoustics.

 

As of right now, the room has a shrill echo, and bass details tend to disappear (an 808 kick is reduced to an attack transient).

 

If anyone has any advice, please post.

 

Thanks again,

 

Wiggum

[Wiggum]

Anyone...?

[Duhduh]

That shrill echo your talking about is most likely coming from the ceiling. In apartments they usually use that acoustic spray stuff. Sound just terrible for acoustics. If I were you, I would use all your Aurelex to cover the ceiling.

[c1131hotmail.com]

Might be the best you can do for where your at. I would take some of the info you have and figure out where the trouble spots are frequencey wise and treat for that, at least you would no where to compensate and what you were hearing, I would also make sure your monitor setup is setup correctly( equi triange etc etc....) and in the worst case scenario parts of the room you might just have to learn, where theres holes in frequencey spectrum and where there is bumps, just dont wipe away too much high end and make sure your low-low mids are covered well. Good Luck.

[Hippie]

I usually wing it when it comes to correcting the sound of a room. If there is too much treble, add soft material to the walls, not enough, add some hard surfaces. When it comes to low end, the LENRD's will only keep it from "collecting" in the corners, if you have a lack of low end I don't believe putting LENRD's up is going to give you something that is not there to begin with. Sometimes moving your monitors closer to the back wall will increase low end.

 

-Hippie

[ViLo]

Originally posted by Duhduh:

That shrill echo your talking about is most likely coming from the ceiling. In apartments they usually use that acoustic spray stuff. Sound just terrible for acoustics. If I were you, I would use all your Aurelex to cover the ceiling.

 

Oh NOOOOOOO! http://www.musicplayer.com/ubb/eek.gif

I was going to spray my new recording/mixing room with that stuff, what should I do? http://www.musicplayer.com/ubb/confused.gif

 

 

 

------------------

[Emile]

Wiggum, for your bass dissapearing, it's probably a resultant of where you are listening. Without moving the speakers for now, just move back or forward un til you find your bass again. You're probably in a "dead spot" right now where the bass freq are cancelling themselves out.

 

Also I didn't quite understand the way things are set up but just know this: the longest part of the room should be behind you. Meaning the speakers should be on one of the 12' wall.

 

Emile

[strat0124]

I agree your listening environment needs to be tweaked. As far as acoustic treatment, strategically placing some 2" or 3" Auralex panels to combat the BOING, maybe some bass traps in the corners. Rectangular rooms in an apartment are difficult but not impossible. As far as tracking acoustic instruments, that's not that hard really. A good condensor, tube mic preamp, and your musician sitting on the couch or in a chair just about anywhere where extraneous noise can't bleed into his performance works. Mic placement is everything of course.

Our band just got through recording last week. We recorded in an old house, with bedrooms used as "isolation" booths. We used everything from matresses, drapes, pillows, office dividers, and REAL acoustic foam to "treat" our rooms suitable for recording. Some folks may scoff at our approach, but for recording on the cheap, it was kick ass. We only had 16 tracks to play with, and tons of outboards...mostly tube pre's, some I own and some I borrowed. You can do alot if you don't worry about your supposedly inadequate gear. Use what you got, and use the dynamics of your environment to your advantage.......bathrooms, kitchens, garages......it works......fo sho.

[ozbassyahoo.com]

I have had a great deal of instant success using "poly's" as described on the following site -

 

http://www.mcs.net/%7Emalcolm/

 

Very inexpensive and easy to make, portable, attractive and best of all effective. Just put one in each corner. Tightens up bass and act as effective diffusion to make a small room "feel" a little bigger.

 

If the room is still "boingy" after that, try using Owens Corning 703 sheets wrapped in a loose weave fabric hung off the walls - once again easy and inexpensive. Beware of getting too enthusiastic and making the room totally dead as it may be still quite live at lower frequencies than just a "clap" or a "1,2" may reveal.

 

 

Lack of bass definition are probably a result of small room standing waves.

 

In my experience in control room situations with nearfield monitors horizontal standing wave problems are more problematical than vertical (ceiling floor) standing wave problems. A sheet of 1/8 inch ply hung at an angle over the mixing area may make a difference - an inexpensive experiment in a rental place.

 

Just a few ideas that sholdn't cost too much money and damage your rental property.

 

Cheers.

[Wiggum]

Thanks everyone for the replies.....

 

This is a tough topic. Every time I think I understand it, I find out some new facts that turn my assumptions upside down.

 

The reason my monitors are on the short wall is due to the layout of the room. The other alternative would be to put them in front of the window, but I think the results would be worse. I would also have to put my gear table in the center of the room, which would look like crap.

 

I need to experiment with my monitors a bit. When I say that the bass lacks definition, I am referring to the following scenario. If I play a sampled 808 kick through headphones, I can hear the attack transient, the hum, and some filter resonance. When I play through the room and monitors, I can only hear the transient, and some undefined low frequencies. I can't hear the wonderful resonance. I don't know if this is because the trebly echo blocks it out, or if it is standing waves, as some suggested.

 

I have a couple of brief questions to follow-up with:

 

1) Is it better to stagger acoustic tiles, or is the ideal situation a completely covered room?

 

2) Is it wise to purchase tiles of various thicknesses, to further aid dispersion (particularly the ceiling)? I would like to hang panels from the ceiling at varying heights, but I can't think of a safe, damage-free way of doing so. A mixture of 1",2",3", and 4" foam might achieve the same effect.

 

3) I've considered building boxes and other fiberglass creations, but I just can't picture what they look like when they are done. I have only read articles -- I've never seen the actual finished product. I would rather have someone build them, as I can't stand working with fiberglass.

 

4) Is acoustic foam a fire hazard?

 

Thanks again for the help.

 

Wiggum

 

 

 

 

This message has been edited by Wiggum on 05-10-2001 at 09:20 PM

[Ethan Winer]

Wiggum,

 

> When I play through the room and monitors, I can only hear the transient, and some undefined low frequencies. I can't hear the wonderful resonance. I don't know if this is because the trebly echo blocks it out, or if it is standing waves, as some suggested. <

 

I'm sure it's standing waves. Do you have a way to play sine wave tones through your system? If so start with, say, 150 Hz. and walk around the room listening for places where the tone gets louder and softer. Then work your way down in 10-20 Hz. increments. I suspect you'll find a number of frequencies that exhibit dropouts and boosts depending on where you are standing. If so, that confirms the problem is standing waves.

 

> 3) I've considered building boxes and other fiberglass creations, but I just can't picture what they look like when they are done. <

 

You can see my bass traps - and plans for building them - at my web site. Go to my Magazine Articles page:

 

www.ethanwiner.com/articles

 

And from there find "Build a better bass trap" from the June 1995 issue of Electronic Musician.

 

--Ethan

[Wiggum]

I HAD AN ACOUSTICAL EXPERIENCE LAST NIGHT!!!

 

I would have never believed it had I not seen it (er, heard it) myself. Ethan and Emile nailed it. My room suffers from standing waves. It's not the only problem, but it's at least one of the confirmed problems.

 

I put on a very simple 808 kick / snare pattern (no reverb), and then tried some different listening positions. When I sat forward (the position I am in when I play my keyboards), the bass was alright. Not exceptional, but alright. When I leaned 2 feet back, it disappeared into a transient.

 

I thought to myself, "Okay, these are nearfield monitors...they are designed for up close listening". But I knew something didn't add up. So I walked into the corners of the room, and Ouila, the bass was back! I tried standing in various parts of the room, and sure enough, the strength of the signal varied.

 

As it turns out, my chair is in the very center of the room. This is the worst spot I have found, but cancellation occurs consistently along the centerline of the room (in varying degrees).

 

So, how do I get rid of these waves? I am going to do some research on my own, but I'd sure like if someone could point me in the right direction. I would hate to move my gear around in the room (the ergonomics are perfect right now), so I am looking for a simple way to eliminate the waves without moving my gear.

 

Ethan: I do use several softsynths, so I could produce a clean sine wave if need be. I don't have a good way to measure the frequency, but I might be able to convert the frequency measurement to pitch, and then simply sustain a note.

 

If I can cancel the standing waves, and do something about the pinging echo, then I might actually have a room I can work in.

 

Thanks again everyone for the help.

 

Wiggum

[Wiggum]

It looks like Ethan's article has some info on standing waves...I'll check it out and continue my research.

 

Ethan, those traps look great! When I think of a bass trap, I picture a cylindrical, itchy, burlap & fiberglass, chicken-wire disaster. Those flat panels are pretty unobtrusive.

 

Thanks for the help,

 

Wiggum

[Ethan Winer]

Wiggum,

 

> I do use several softsynths, so I could produce a clean sine wave if need be. I don't have a good way to measure the frequency, but ... <

 

That's not really necessary anymore, since you confirmed the problem is standing waves.

 

> Ethan, those traps look great! When I think of a bass trap, I picture a cylindrical, itchy, burlap & fiberglass, chicken-wire disaster. Those flat panels are pretty unobtrusive. <

 

These are the best bass traps I know of. They are absolutely effective, and as you can see they are barely noticeable. You do have to make them yourself, though, since I've never seen such a trap offered for sale commercially.

 

--Ethan

[Guest]

Furniture adds to acoustical treatment.

 

Get some cheap tall bookshelves and put some books and magazines and old vinyl recordings in your bookshelves. They'll probably act as bass traps too. They'll interfere with the standing waves and help randomize your reflections. The more varied your reflective and absorbtive surfaces the better your room will sound. Put a pad under your rug. That'll help.

 

Joe

[Wiggum]

Ethan,

 

I read through your article (Build a Better Bass Trap). Great stuff.....

 

Quick question for you:

 

You mentioned using 1/2" holes, toggle bolts, and caulk to seal the low traps to the wall. Is there a way to get a similar effect without a permanent installation? My landlord will end me if I drill large holes into the walls, so I am trying to figure out a way to trap the low bass w/o any damage.

 

I hope to get a house over the next two years, which will permit me to do more intensive modifications. In the meantime, how many traps do you think I need to correct a 12'x15' room? I thought about putting one low trap in each corner of the room, and then maybe some mid / high traps along the main walls (or perhaps just going with the simpler acoustic foam for the higher frequencies). How heavy is a low trap? Is it something I could hang like a picture?

 

That's a great looking home studio you have. I noticed that you have your monitors near a window. Does this create any acoustic problems? I thought about moving my monitors, but the only viable alternative is in front of my picture window.

 

Thanks again for the help,

 

Wiggum

[Ethan Winer]

Wiggum,

 

> Is there a way to get a similar effect without a permanent installation? <

 

I've never done this, but you could probably build portable 2'x8' "back walls" out of very heavy (3/4-inch) plywood and mount the traps to them. The fiberglass-only absorbers don't need that of course. But it's important that each bass trap backing be rigid enough to not flex. And the box must be sealed air-tight just as if it were mounted on a real wall. You could also glue a piece of 3/4-inch sheetrock to each backing to make them even more rigid.

 

> That's a great looking home studio you have. I noticed that you have your monitors near a window. Does this create any acoustic problems? <

 

No problem at all. The most important thing is that the room be mostly symmetrical, and that is has enough bass traps. Since my single room doubles as a recording area I didn't install as many traps as I would have if it was a control room only. Normally for a control room you'd want to cover three of the walls with alternating (low / mid / hi / mid) traps. But even just putting bass traps in the corners helps a lot, and then the more you add the better it gets.

 

--Ethan

[Wiggum]

Ethan,

 

If I understand correctly, you're saying that I could build the same bass traps, but instead of mounting them to the wall, mount them to some thick, rigid plywood. Do you have any suggestions as to how I could place them? Would I just lean them against the wall, or should they be free standing?

 

If I can make them free standing (by using some sort of stand), does it matter how close to the walls they are?

 

I'm really excited about this. I tried moving my DAW to the closet last night, and that alone made a huge difference in the listening experience. I didn't realize how obtrusive that piece of gear can be.

 

Hopefully I will have the DAW move completed in two weeks (need to wire my own cables). From there, I am going to build the traps, and hopefully have me studio complete within a month.

 

All the best,

 

Wiggum

[KikkyMonk]

In one of your articles you said that pretty much all speaker wire is the same... So all of that monster wire stuff is B.S.? The reason I ask is my band is about to replace all of our wires with monster cables (mic cables, instrument cables, and speaker cables) and I want to know if it will make a difference. Also monster cable even put out some stuff like bass cables and jazz cables and rock cables.. this is B.S. too?

Thanks

 

Dave

(P.S. your articles are wonderful reading.)

 

sorry wiggum for butting in on your post

[Philip OKeefe]

Wiggum, the math isn't as difficult as you might think.

 

From Everest's books I'm sure you've learned about axial modes and how they are the primary concern for lower frequencies (below about 500 Hz). Above that point sound tends to act like light - ray acoustics - Angle of incidence equals angle of reflection. IOW, if the sound impacts the wall at a 45 degree angle, it will bounce off in a mirror image 45 degree angle.

 

Lower frequency modes will have a dramatic effect on the lower frequency response of the room. One of the reasons the 808 kick seems to be disappearing may be because the lower frequency components of the sound are cancelling out at the mix position. Sound waves are bouncing off one wall and hitting either direct sound or other reflections that are out of phase with that signal. And you know what happens when two waves of the same frequency hit each other out of phase - they cancel each other out.

 

Here's some suggestions:

 

Calculate the axial response of your room - don't worry about the tangental and oblique modes. There's three dimensions in your rectangluar room - Lenght Width and Height. Take the speed of sound (we'll use 1,130 FT / Sec. as an average... it varies with different temperatures, humidity levels, elevation above sea level, etc.) and divide it by the first dimension (we'll start with the 15' length). So 1,130 / 15 = 75.33. Then divide that by 2 for the fundemental axial mode frequency (37.66 Hz) for that room dimension. That frequency, plus every harmonic of it (75.33 Hz, 112.98 Hz, 150.64 Hz, 188.33 Hz, etc...) will be "reinforced" by the room's length dimension. Do the same calculations for the room's width and height, and figure them out all the way up to 400 - 500 Hz. Then chart them all out and see if there's frequencies that show up in two or even all three collums. THOSE frequencies are the ones that are being double or even triple reinforced, and when a note or sound at those frequencies is played, the room will tend to "go off" like a cannon. Knowing WHICH frequencies your room is artifically reinforcing will be very useful to you because you'll either be able to correct them as part of your acoustical treatment and / or you'll at least be aware of them so you don't over compensate when you're mixing.

 

Bass does tend to build up at the junctions of walls and in corners. Bass trapping can be difficult to do in a apartment. Lenrds are a good product, but you can also make your own bass traps. There's different plans out there on the web, and a few of them can be modified for use in an apartment.

 

As far as mid and high frequency control, you might want to try some old tricks. First of all, the BBC study from years ago shows that putting all the absorptive material together is less effective than spreading it around a bit. So I think you're on the right track there.

 

One common idea is to place the majority of the absorption for the mids and highs near the front half of the room, making it deader, and putting diffusion at the rear wall behind you (a simple bookcase full of books can do wonders in this respect) and the bass traps into the corners and in the rear of the room.

 

Take a regular mirror and have an assistant help you - while you're sitting in the "mix" position, have the assistant hold the mirror on the various wall and ceiling positions at the front half of the room. If youcan see the speaker(s) reflected in the mirror, sound at the upper and midrange frequencies will bounce off those spots and be directed to the mix position - just as the light reflecting off the speaker is reflected off the mirror to your eyes. Those places where you can see the speaker in the mirror are good candidates for acoustical foam. The idea is that you should (as much as possible) be hearing direct sound from the speakers when seated at the mix position, and reflected sounds should travel AT LEAST 20' before they hit your ears (for more info, look into something called the Haas effect...)

 

One final thought: Don't monitor at really loud levels. The frequency response of your ears is at its most linear at about 85 dB. There's really no reason to slam the mix at a level louder than that on a ongoing basis (once in a while for vibe and visceral feel, but not as a normal pratice...). Besides, your neighbors will be less likely to call the authorities on you, and the hearing you save will be your own!

 

I hope some of this is of use to you. Best of luck with your project studio.

 

Phil O'Keefe

Sound Sanctuary Recording

Riverside CA

http://members.aol.com/ssanctuary/index.html

pokeefe777@msn.com

[Philip OKeefe]

Originally posted by pokeefe777@msn.com:

Wiggum, the math isn't as difficult as you might think.

 

From Everest's books I'm sure you've learned about axial modes and how they are the primary concern for lower frequencies (below about 500 Hz). Above that point sound tends to act like light - ray acoustics - Angle of incidence equals angle of reflection. IOW, if the sound impacts the wall at a 45 degree angle, it will bounce off in a mirror image 45 degree angle.

 

Lower frequency modes will have a dramatic effect on the lower frequency response of the room. One of the reasons the 808 kick seems to be disappearing may be because the lower frequency components of the sound are cancelling out at the mix position. Sound waves are bouncing off one wall and hitting either direct sound or other reflections that are out of phase with that signal. And you know what happens when two waves of the same frequency hit each other out of phase - they cancel each other out.

 

Here's some suggestions:

 

Calculate the axial response of your room - don't worry about the tangental and oblique modes. There's three dimensions in your rectangluar room - Lenght Width and Height. Take the speed of sound (we'll use 1,130 FT / Sec. as an average... it varies with different temperatures, humidity levels, elevation above sea level, etc.) and divide it by the first dimension (we'll start with the 15' length). So 1,130 / 15 = 75.33. Then divide that by 2 for the fundemental axial mode frequency (37.66 Hz) for that room dimension. That frequency, plus every harmonic of it (75.33 Hz, 112.98 Hz, 150.64 Hz, 188.33 Hz, etc...) will be "reinforced" by the room's length dimension. Do the same calculations for the room's width and height, and figure them out all the way up to 400 - 500 Hz. Then chart them all out and see if there's frequencies that show up in two or even all three collums. THOSE frequencies are the ones that are being double or even triple reinforced, and when a note or sound at those frequencies is played, the room will tend to "go off" like a cannon. Knowing WHICH frequencies your room is artifically reinforcing will be very useful to you because you'll either be able to correct them as part of your acoustical treatment and / or you'll at least be aware of them so you don't over compensate when you're mixing.

 

Bass does tend to build up at the junctions of walls and in corners. Bass trapping can be difficult to do in a apartment. Lenrds are a good product, but you can also make your own bass traps. There's different plans out there on the web, and Ethan's are WONDERFUL and can be modified for use in an apartment (make free standing versions).

 

As far as mid and high frequency control, you might want to try some old tricks. First of all, the BBC study from years ago shows that putting all the absorptive material together is less effective than spreading it around a bit. So I think you're on the right track there.

 

One common idea is to place the majority of the absorption for the mids and highs near the front half of the room, making it deader, and putting diffusion at the rear wall behind you (a simple bookcase full of books can do wonders in this respect) and the bass traps into the corners and in the rear of the room.

 

Take a regular mirror and have an assistant help you - while you're sitting in the "mix" position, have the assistant hold the mirror on the various wall and ceiling positions at the front half of the room. If youcan see the speaker(s) reflected in the mirror, sound at the upper and midrange frequencies will bounce off those spots and be directed to the mix position - just as the light reflecting off the speaker is reflected off the mirror to your eyes. Those places where you can see the speaker in the mirror are good candidates for acoustical foam. The idea is that you should (as much as possible) be hearing direct sound from the speakers when seated at the mix position, and reflected sounds should travel AT LEAST 20' before they hit your ears (for more info, look into something called the Haas effect...)

 

One final thought: Don't monitor at really loud levels. The frequency response of your ears is at its most linear at about 85 dB. There's really no reason to slam the mix at a level louder than that on a ongoing basis (once in a while for vibe and visceral feel, but not as a normal pratice...). Besides, your neighbors will be less likely to call the authorities on you, and the hearing you save will be your own!

 

I hope some of this is of use to you. Best of luck with your project studio.

 

Phil O'Keefe

Sound Sanctuary Recording

Riverside CA

http://members.aol.com/ssanctuary/index.html

pokeefe777@msn.com

[Ethan Winer]

Wiggum,

 

> If I understand correctly, you're saying that I could build the same bass traps, but instead of mounting them to the wall, mount them to some thick, rigid plywood. <

 

Yes, exactly.

 

> Would I just lean them against the wall, or should they be free standing? <

 

I'd lean them against the wall, to most closely emulate the way they were originally intended to work.

 

> I tried moving my DAW to the closet last night, and that alone made a huge difference in the listening experience. I didn't realize how obtrusive that piece of gear can be. <

 

I suffered for years with the fan noise from my Crown power amps. When I overhauled my studio recently and got rid of all my outboard gear, I built a little box out of black shelving I bought at Home Depot. I simply glued the edges together with contact cement, leaving the bottom and back open. I put the power amps under my desk and put the "box" over the amps. Yes, what a big "quality of life" improvement it is to get rid of ambient background noise!

 

--Ethan

[Ethan Winer]

Dave,

 

> In one of your articles you said that pretty much all speaker wire is the same... So all of that monster wire stuff is B.S.? <

 

I'm assuming that question is for me?

 

Yes, as far as I'm concerned it's all BS and marketing hype aimed at getting you to spend more than necessary for cables. There are differences in mike cables, but only truly cheap junk will be a problem for normal cable lengths. For speaker wire, just get the heaviest cable practical.

 

> monster cable even put out some stuff like bass cables and jazz cables and rock cables.. this is B.S. too? <

 

It sure is.

 

--Ethan

[Philip OKeefe]

Originally posted by Ethan Winer:

Wiggum,

 

> Is there a way to get a similar effect without a permanent installation? <

 

I've never done this, but you could probably build portable 2'x8' "back walls" out of very heavy (3/4-inch) plywood and mount the traps to them. The fiberglass-only absorbers don't need that of course. But it's important that each bass trap backing be rigid enough to not flex. And the box must be sealed air-tight just as if it were mounted on a real wall. You could also glue a piece of 3/4-inch sheetrock to each backing to make them even more rigid.

 

--Ethan

 

 

I have to complement you on these designs Ethan - they work, and work very well.

 

I did a similar mod on a set of your traps once and it worked just fine.

 

Phil O'Keefe

Sound Sanctuary Recording

Riverside CA

http://members.aol.com/ssanctuary/index.html

pokeefe777@msn.com

[Ethan Winer]

Phil,

 

> I did a similar mod on a set of your traps once and it worked just fine. <

 

Thanks for letting me know that! Over the years a lot of people have asked if those traps can be built but not mounted to the walls, and I've always said "probably" but never heard from anyone that actually did it.

 

--Ethan