Bass Brace

hearingimpared

Does anyone want to sell a bass brace? Please PM

schwarcw

Hearingimpaired,

I think you could easily make one with a T-nut, some all thread and a couple of wing nuts from Home Depot. You could mount the T-nut directly into a wall stud, or into a wood mounting plate that you can anchor into the wall. Cut the all thread to the desired length and screw into the back of the speaker, then back it out into the T-nut. Tighten down the two wing nuts. The total cost would be about $15.

I've attached a couple of pic's of T nuts.

John in MA

If you'll forgive the intrusion, what's a bass brace exactly? I punched that into Google and got a fellow with a bunch of fish. Don't think that's right...

schwarcw

Hi John in MA! Welcome to the Club Polk Forums!

A bass brace was supplied with the large Polks SDA's (1.2's, 2.3's, SRS). The brace was a long, threaded rod that mounted to the back of the speaker and the rear wall. This brace anchored the speakers and reduced cabinent resonance. Resulting in a tighter mid range and bass response.

I've attached a picture of a polk supplied bass brace.

schwarcw

Ooops! Check post #13 in this thread for pictures.

http://www.polkaudio.com/forums/showthread.php?t=42929

Carl

John in MA

Ah, thanks. That explains it. Now I'm wondering if you'd get any kind of weird reasonances with lousy walls.

schwarcw

John in MA wrote:

Ah, thanks. That explains it. Now I'm wondering if you'd get any kind of weird reasonances with lousy walls.

Not if they're well anchored. I suggested anchoring them to a wall stud.

Carl

hearingimpared

schwarcw wrote:

Hearingimpaired,

I think you could easily make one with a T-nut, some all thread and a couple of wing nuts from Home Depot. You could mount the T-nut directly into a wall stud, or into a wood mounting plate that you can anchor into the wall. Cut the all thread to the desired length and screw into the back of the speaker, then back it out into the T-nut. Tighten down the two wing nuts. The total cost would be about $15.

I've attached a couple of pic's of T nuts.

Thanks Carl

DarqueKnight

John in MA wrote:

Ah, thanks. That explains it. Now I'm wondering if you'd get any kind of weird reasonances with lousy walls.

Sure you would. As to whether they would be audibly ojectionable would depend on your listening levels, the room's acoustics and the wall flexibility.

Anchoring the bass brace to a wall stud would be an improvement, but what are the chances that a wall stud is going to be in the exact place that you need it to be?

Anyway, the idea of bolting my SDA's to the wall is not appealing.

amulford

DarqueKnight wrote:

Anyway, the idea of bolting my SDA's to the wall is not appealing.

Right on. If anything, some good spikes or maybe coupling it to a HEAVY piece of granite.

schwarcw

I agree that spikes might be a better anchor for the big SDA's, the problem is that the speakers now become almost immovable. At least with a brace you can unscrew the wingnut, turn the threaded rod into the speaker and slide the speaker on the floor. With spikes you'll need two people to lift the speaker to access anything behind it (wire, cables, components, etc.) In my arrangement this is a necessity to access the back of my entertainment center. The brace was recommended by Polk in some of the literature I have. In my case the braces are anchored to a concrete bearing wall. I have no wall resonance.

Carl

hearingimpared

I want to be able to try the bass brace, the spikes, and anything else that could improve the sound in any way. I want to let my ears tell me what is the best way to go. I'm in the process of getting a full set of spikes and floor protectors from MYE Sound. I am taking Raife's suggestion in the Compendium and other correspondance to take my time and record the differences with and without.

Joe

schwarcw

hearingimpared wrote:

I want to be able to try the bass brace, the spikes, and anything else that could improve the sound in any way. I want to let my ears tell me what is the best way to go. I'm in the process of getting a full set of spikes and floor protectors from MYE Sound. I am taking Raife's suggestion in the Compendium and other correspondance to take my time and record the differences with and without.

Joe

Sounds like a solid plan Joe. Let us know what your ears tell you.

Carl

hearingimpared

I still want to know if anyone wants to sell me a bass brace!!!

F1nut

Good luck with that one.

hearingimpared

F1nut wrote:

Good luck with that one.

Don't you think I can get one???? Maybe I should consider making my own.

I also have a AI-1 that I want to compare with a straight interconnect so I guess I'll have to make one of those too. Although the mono blocks I am getting can be tied together as common ground. Maybe I'll just cut the transformer out of the AI-1 and splice the cable together.

Joe

Larry Chanin

Hi,

Of course there's no harm in experimenting, especially if you have the means to objectively measure and compare the results. However, I'm inclined to agree with Raife and amulford. There is a great deal of uncertainty regarding the acoustic outcome in attaching vibrating devices to walls.

In the thread that Carl references, Bob McGowen comments about the SDA braces:

The speakers are tall without being all that deep in proportion and the Brace prevents any movement that might otherwise occur due to high volume levels. (Very excited drivers mounted fairly high!) Combine this with their hefty weight and say a less than rock solid floor and Polk figured you could get movement. I can see their point. If you were to find the balancing point of one of these speakers I think you'd find them a bit top heavy.

Chances are that Polk introduced the braces more out of a concern for saftey rather than a pressing need to improve SDA's bass response. (For folks with toddlers, the brace probably makes a lot of sense.)

I frequent a number of Home Theater forums where it is universally agreed to avoid situations in where speakers producing energetic, deep bass become coupled to structures. The concern centers around a few issues. Coupling a speaker to a wall will cause the wall to resonate at the wall's natural resonant frequency. It would be a major stroke of luck if by accident this frequency just happened to cancel a problematic room mode. It is much more likely that any randomly generated wall resonances are going to interfere with the bass response of the room. Unless care is taken, mechanical coupling can sometimes result in unwanted buzzing and rattling noises. Finally, coupling with walls adversely effects sound isolation from other rooms.

Its true that if Carl's braces are solidly anchored into a concrete bearing walll, resonances and buzzing are very unlikely. However, concrete does an excellent job of transmitting bass energy outside the listening room, and depending on your situation, this can present a problem.

To avoid these situations many home theaters, including my own, have specially constructed stages filled with sand as a means of isolating the bass from subwoofers and floorstanding speakers from being transmitted through the floor. Care is taken to ensure that the stage is freestanding and does not come in contact with the walls.

Larry

hearingimpared

Larry Chanin wrote:

To avoid these situations many home theaters, including my own, have specially constructed stages filled with sand as a means of isolating the bass from subwoofers and floorstanding speakers from being transmitted through the floor. Care is taken to ensure that the stage is freestanding and does not come in contact with the walls.

Larry

Wow Larry great information. Can you be more specific in describing the "specially constructed stages filled with sand?"

Thanks,
Joe

Larry Chanin

hearingimpared wrote:

Wow Larry great information. Can you be more specific in describing the "specially constructed stages filled with sand?"

Thanks,
Joe

Hi Joe,

I'm not sure a stage would lend itself to your situation. I just mentioned it to illustrate an alternate approach to coupling your speakers to the walls. Without knowing your constraints perhaps spikes or speaker weights might be more practical.

In any event, to answer your question you can get a little better idea visiting my web site.

Below is the plan layout of my theater. At the top of the drawing you can see the framing for the stage. This framing was lined with very heavy plastic sheeting (pond liner) and then filled with 1,000 pounds of dry sand before the decking was installed.



I then placed my main speakers and lower center channel speaker on massive concrete block stands on the deck of the stage as shown on the drawing below.



Larry

hearingimpared

Thanks Larry. . . you just gave me a new idea of how to try another way of bracing those big boys. . . I have one word of warning for you, if you see a beautiful, Mediterranean looking woman who is built like a brick s#i! house coming your way with dark flashing eyes duck and run . . . because it is probably my wife!!!!

Joe

F1nut

Each situation is different. What works for one, doesn't for another. I've used the Bass Brace for years with no issues and therefore highly recommend them.

schwarcw

F1nut wrote:

Each situation is different. What works for one, doesn't for another. I've used the Bass Brace for years with no issues and therefore highly recommend them.

Exactly Jesse!

Larry, you always provide some good insight and recommendations. I think for the cost of a homemade pair of bass braces (my estimate is about $15) and the relative ease of installation (four to eight screws with anchors or into studs) try it and give it a listen. Same for the spikes. You can probably pick a set of these up for $30 or so. Try them both. See if you get any wall resonance or one method gives you better sound in your opinion. Polk does not recommend using both as they state "some cabinent movement is neccessary".

76911

Hello Larry,
Been very busy with school...great to see your posts.

Bob Worsham

univera

Larry, you are a sick man...As far as "coupling" the SDA's to a piece of granite, is that nothing more than having a custom piece cut to sit under the speaks? I have carpet and don't want to use either spikes or braces for all the reasons already mentioned.

Also, does anyone have any suggestion on how to keep bass from penetrating over to the next house? My neighbors, although super cool, are very close and can hear the bass of the SDA's alone. A sub is really going to boom them out. I am guessing not since bass is felt and not heard, but if there is a way...The walls are sheetrock and vinyl siding.

amulford

As far as "coupling" the SDA's to a piece of granite, is that nothing more than having a custom piece cut to sit under the speaks?

Yes, kind of. You get the piece cut. Then attach spike pads to it, ala super glue or whatever. Then sit the spikes on them. Or you could drill it and bolt the granite to the bottom of the cabinets.

Also, does anyone have any suggestion on how to keep bass from penetrating over to the next house?

Maybe turn it down? Eff that:D

Kind of hard, sounds like the house is transducing. F#ckin A!:cool:

F1nut

Soundproof sheetrock may help.