Acoustic Room Treatments For My Altecs

[voice of the theater]

Much of this is probably acoustics 101 basics but I'd appreciate the help as I do most stuff by ear and I know there are people here who really understand the science of this stuff.

I've been tinkering with my two Model 19 setups trying to get the best sound from them possible. I've got the 19's in my in home recording studio sounding great. I keep my newer pair of Santana II's on top of the 19's in that room (my older 19's from 1976) and they sound phenomenal when I play the 19's and Santana II's in that room all at once. This past week I've been focusing on the Model 19 setup in my rec-room. I've got my older pair of Santana II's on top of the 19's in that room (my newer 19's from 1978). I own a spare pair of original tweeters for the Santana II's (from Ebay) and I installed them this week. What a difference! Now my older pair of Santana II's sound just as bright as my newer pair of Santana II's whereas before I swapped out the original tweeters for the (original) pair that I bought on Ebay they sounded dull in comparison to how they sound now.

NOW ONTO THE MAIN POINT OF THIS THREAD I've been spending more time this week with the acoustics in my rec room. It's a considerably smaller room than my recording studio and while the speakers sound great in that room, I've been trying different things to help out with the acoustics. As you can see in the photos below, I have one of my Model 19's in a corner, and the other one is not in a corner. I know that you're not "supposed" to place speakers that way, but due to the size and layout of the room, I don't have a choice. Of course, with no acoustic treatments in the room, the 19 in the corner sounds a little louder and has a little more bass than the 19 that's not in the corner. I swapped 19's before and it's the same problem no matter which 19 is in the corner of course. I've had 4 wool blankets tacked up in that corner to deaden it and it helped quite a bit. This past week I added two layers of foam (bed mattress pad/egg crate type foam) over the 4 wool blankets and it has really deadened the acoustical effect of corner placement of that 19 even more.

FIRST QUESTION: Is there anything better than the two layers of foam with 4 wool blankets behind them to deaden this corner? Or, is there something that will work as well and not look so bad? (although I'm getting used to the look)

As you can see in one of the photos, there is a door next to the other Model 19 (the one that's not in a corner). Believe it or not, the system sounds noticeably better with that door open. It sounds more open and airy and detailed, and the stereo balance sounds much better as well. I would think that to "compete" with the other 19 that's in the corner, you'd need the door closed so that this 19 has more of a surface to reflect off of. I guess since I've somewhat deadened the corner effect for the one speaker, getting rid of the door reflection is a good thing for the other one as I want to hear the sound of the speakers, not the sound of the reflections.

SECOND QUESTION: Does the above statement make sense? Is the fact that the system sounds better with the door open also partly due to it being a smaller room, opening the door gives the sound "somewhere to go"/less surface to reflect off of, where as closing the door makes more of an echo chamber?

Lastly, the overall design and layout of this room would appear to be horrible for acoustics, but with the foam in the one corner and the door open in the other, it sounds fantastic. There is carpeting on the floor and ceiling tiles on the ceiling which both absorb a lot of sound, maybe that helps? Both speakers sound to be at about the same volume level now (the corner one no longer sounds considerably louder now that there's foam in that corner), and the bass now sounds like it's coming more from the center (no longer sounds like most of the bass is coming from the left corner speaker).

THIRD QUESTION: Does the fact that there is no rear corner on the right side of the room (see last photo--this side of the room has an opening with no door that leads to my recording studio) help the overall sound of this smaller room by giving the sound/echoes "somewhere to go"/less surface to reflect off of? Or, is the lack of a rear corner in the right side of the room a contributor to the fact that without the foam padding in the front left corner, the left channel sounds louder than the right channel (there is a corner in the rear left side of the room, and no corner in the rear right side of the room)?

LAST QUESTION: It occurred to me that since the left speaker is in the corner, it's a lot closer to the entire left wall. Should I cover that entire left wall with foam (or something "better than foam) or is it mainly the corner that's the culprit and not the closer proximity to the entire left wall (compared to the right speaker being farther from the entire right wall?

Thanks in advance for the help.....

[gortnipper]

Get Jim Smith's book - cheap and good - Get Better Sound - themanual

You can read up on Traps like those offered here - TubeTrap - Welcome to the Real World of Bass Traps

And build them your self - DIY Tube Traps

and place them to your ears content - Optimizing ASC Tube Traps by J. Peter Moncrieff

[RonSSS]

Have you tried the slap echo test? Just clap your hands at the listening position and see if you get echo. If so, treatment on the adjacent walls will help.
A piece of sonax on that door would help too. Cover the whole door.

Ron

[cradeldorf]

I read that if you sit in the listening position and have a friend run a mirror along the side walls and when you can see the speaker in the mirror, that's where you put some form of dampening apparatus. That's about all I know other than the traditional bass traps.

[voice of the theater]

Have you tried the slap echo test? Just clap your hands at the listening position and see if you get echo. If so, treatment on the adjacent walls will help.
A piece of sonax on that door would help too. Cover the whole door.

Ron

I just went down there (finished basement rec-room) and did some hand claps. At first, I didn't hear any echo. but I tried to do as abrupt and "sharp" and loud of a clap as I could muster and I heard a very faint echo. Not a reverb/ringing type of echo, rather it is a very faint sharp/brief echo--a split second in length. It's coming from my right and I'm wondering if it's from my recording studio wall that's on the other side of the opening to my recording studio--see the last photo above where this room opens up into the next room with no door--that far wall in the next room (recording studio) has got to be about 30 feet away. Is this type of a faint sharp/brief echo that is possibly (don't know for sure) coming from the wall in the next room that's 30 feet away a problem?

I went to the Sonex website and that stuff is $235 for 8' x 8' of their cheaper "value" line of foam. I don't skimp on audio but I may need more than an 8'x8' piece if I decide to do more than just the corner where I currently have the mattress pad/foam. Is there anything else that would work comparably that isn't going to cost me $500-$700? How good/bad is that mattress foam pad--what else might work well?

Get Jim Smith's book - cheap and good - Get Better Sound - themanual
You can read up on Traps like those offered here - TubeTrap - Welcome to the Real World of Bass Traps
And build them your self - DIY Tube Traps
and place them to your ears content - Optimizing ASC Tube Traps by J. Peter Moncrieff

I don't have room for this type of bass trap. I think I need something flat like foam.....

I read that if you sit in the listening position and have a friend run a mirror along the side walls and when you can see the speaker in the mirror, that's where you put some form of dampening apparatus. That's about all I know other than the traditional bass traps.

Hmm, never heard of the mirror test other than when my wife uses a mirror to see if I'm still breathing!

[Alien_Shore]

In this case, learning a bit of the science behind this will be helpful.
Part of what is creating the different things you're hearing is baffle diffraction. Take a look at this page: Bafflestep

It is a fairly good simple explanation of a complex topic.
As the lower frequency sounds wrap around your cabinet, there is some diffraction loss, and in the case of your open door, probably as much as 6 dB loss for some frequencies as those waves radiate down the hall. Adding to this is reflective reinforcement (like the speaker in the corner that sounds louder). Here is another link that describes placement and effects: Optimum Speaker Placement

[mah]

FWIW

Acoustic Treatment and Design for Recording Studios and Listening Rooms


DIY Absorbers for the Less-than-Handy Man: Part 1 | Audioholics

DIY Absorbers for the Less-than-Handy Man: Part 1 - page 2 | Audioholics

DIY Absorbers for the Less-Than-Handy Man - Part 2 | Audioholics

[GM]

FWIW, I use a child?s snap ?clicker? toy for the echo test.

The rooms + doorway is no different than a type 1 double bass reflex acoustically, so sound is not ?wrapping? around the corner into the other room, just that the right speaker?s bass is less due to being near the ?vent? while the other speaker has more due primarily to being the furthest away at the closed end of this resonant ?pipe?.

Rather than damping the left speaker, I?d try tuning it lower or even sealing up its vent and only add damping if the latter still allows for too much bass ?boom?.

Have you tried using more toe-in? Virtually all speakers benefit from their axis crossing somewhat in front of the ?sweet? spot. This also generally removes any need for sidewall damping with horns, though the bookcase will probably need a highly damped ?curtain? more that the corner once the speaker?s tuning is lowered.

If cosmetics aren?t a high priority, then no need to spend big bucks. Using inexpensive ?trail pad? or similar OPEN CELL foam ?horn? extensions that extend somewhat behind/in front of the cabs combined with more toe-in will negate the need for most room treatments since it will damp its cab, floor, ceiling, eigenmodes, off axis polar response and if a suspended acoustic blanket is used to damp the doorway ?vent?, then all that?s left is DIY broadband traps for the two other corners and some sort of damping [thick decorative rug or similar DIY cloth covered, foam filled ?picture frame? absorber] to keep the rear wall from being too reflective since it appears that the LP is [very] near it.

Unfortunately, I know of no clear cut way to determine the amount of foam overhang required, but extending them to the rear/side wall is normally a good plan and my SWAG is it will need to extend at least 12? in front of the horn mouth?s vertical plane.

GM

[voice of the theater]

Thanks GM! We have an old clicker here that my wife had tried using to train our dog years ago and I just used it to do the echo test downstairs in my rec room. Good news is there is no noticeable echo if I use the clicker while standing next to either speaker (I think the carpeting and the ceiling tiles are absorbing a lot of the sound). If I use the clicker while sitting in my normal listening spot (where I did the clap test), there is still a very faint echo coming from the wall in the next room some 30+ feet away (there is an opening with no door leading to that room--see pic in post 1) but I'm pretty sure that there's no audible echo from that wall (in the next room) originating from the speakers/in their current position because when I use the clicker while standing next to the speakers I don't hear the echo--only when I use the clicker at my listening spot and there's no sound originating from listening spot (no speaker there) so a slight echo coming from the next room only when sound originates from my listening spot shouldn't be a problem I wouldn't think?

Thanks for the tips on speaker toe in and on inexpensive foam. I'll try experimenting with more toe in and I've been googling open cell foam. I assume the 1" and 2" stuff is flexible for bending around corners? Otherwise, I could just make a cut in a sheet to go around that one corner. The foam in the link below is much less expensive and doesn't look bad. Do people usually use 1" or 2" (or thicker?) to "dampen" walls and corners? Here's one link-- anyone out there know a better or even cheaper place to buy this stuff?

The Foam Factory, Open Cell Foam, Acoustic Foam, Color Foam,

Thanks everyone for all of the advice and the informative links you've posted here so far. I guess maybe I've still got potential for some of that "fancy book larnin"! This link in particular was interesting--see quote below link....

What speaker placement and listener position is optimum? : Empirical Audio

"A good rule of thumb is to pull box speakers out at least 1.5 feet from the back wall of the listening room. 2-3 feet is better, but you may lose some bass reinforcement depending on your speakers and room size. Side walls can be just as bad or worse. Ideally, each speaker should have an open door on its extreme side, but this is usually not architecturally possible. Try to locate speakers away from room inside corners and hard surfaces like fireplaces."

So I guess keeping that door (next to the speaker) open is a good idea after all! BTW, my rec room is the smallest listening room I have in my house (my recording studio where I have my second pair of 19's is a huge room as is my living room where I have my Model 14's). However, the rec room is large enough for the 19's--they sound great in there. I measured the room and it is approx 17x 13 (I think if the room was a little smaller it wouldn't work for Model 19's). Because of the door the most space I can have between the speakers is a little over 9 feet between woofer dust caps (because I have them toed in--it would be more if I angled them straight). When I sit on the center cushion of my couch (which is pressed up tight against the back wall) I am dead center between the two 19's and I get great stereo imaging with them and I'm back far enough (13 foot deep room) so that highs and lows seem to come from around the same point--that's why I unfortunately have to have the speakers almost touching the wall that's in back of them. If I were to move them forward a foot and a half they'd be too close to me and I'd hear highs coming from the top of them and lows coming from down below instead of how it sounds now more like one source for all the sound with me back a little ways. Please continue to chime in on this thread--I'm learning a lot and hopefully other people reading this thread are as well....