Bass Brace, Spike, and where to brace???

[proffitt]

I have a newly acquired pair of SDA SRS 2. Love them. I've read about the bass brace, and of course spikes. They will go on carpet. So, brace and spike? Or just one or the other?

If bass brace, I have a unique opportunity I wanted to run by you. I'm building out my home theater in a currently unfinished basement room, and these will be the front L&R. The room will be roughly 16' wide, 40' long. They will go in the center of the 16' wall. This wall is a poured concreted wall full height of 9 feet to the ceiling. It has already been framed with a 2x4 stud wall, 2 inches off the concrete wall. The stud wall does not touch the concrete wall. I will sheetrock the stud wall soon.

So I would have two options for the bass brace. 1) connect the brace to the stud wall. Or 2) take advantage of the concrete wall that is just 2 inches farther back, connecting the brace through a hole in the sheetrock, directly to the concrete wall.

I imagine there is some "activation" of the stud wall with the brace connected to it. Is this intended? Or is the brace intended to connect to the most solid structure nearby, and that is just usually a stud wall? The fact that I am able to get much more solid than the stud wall, just 2 inches farther back.... Or am I missing the point of the bass brace? By not coupling it to a semi "active and moving" stud wall am I missing out on something? Does the stud wall play a part in actually creating and/or radiating lower frequency sound waves, or is the sole purpose just to immobilize the speaker as best as possible?

Thanks for any help.
proffitt

[Toolfan66]

I wouldn't mess with the concrete wall. Just mount it to the wall and immobilize the speaker. Question: does the SDA 2 have a nut on the back for a bass brace?

Spikes are a must IMO..

Don't over think it, and it sounds like you have a great project in the works!!

Enjoy!!

[PolkieMan]

I have the original ones that came with my speakers. Brackets came with that is are screwed to the wall with wood studs behind the sheet rock.
The bracket mounts to the wall with two screws and then has a threaded center for the all
thread and locking nut. It sets them fairly solid and keeps them from being knocked over. One other thing is
they are easy to move just unscrew and slide on carpet.

[proffitt]

No, there's no type of connection for the brace on the speaker. I was going to construct my own braces from threaded rod and nuts epoxied to plates. It would allow me to turn the threaded rod within the nuts kind of like a turnbuckle, to fine tune it after speaker placement. Epoxy only cause I don't have a welder.

[Toolfan66]

I wouldn't bother with it if I was you. Spike them and enjoy...

[F1nut]

Spikes are better.

[Dawgfish]

+1 on the just spikes recommendation. The SRS 2s didn't come with the bass brace OEM. The bass brace was used on the taller SDAs. Spiking my SRS 2s was one of the best mods I've done to them.

[Schurkey]

First Guess: The Bass Brace is less effective than spikes.

Second Guess: You have a unique opportunity, you might as well take advantage of it. I'd install BOTH spikes and bass brace.

"I" would connect the Bass Brace set-up to the concrete if at all possible. Main problem will be finding best speaker position before you lose access to the 'crete.

An alternative would be to include a 2X4 horizontally at the appropriate height, glued 'n' screwed to the concrete behind the Sheetrock. Then no matter where along the wall you want the speakers, you've got the solid wood 2x4 at the right height to attach to.

Attaching a Bass Brace to a sheetrock wall seems to me like attaching it to an enormous drum skin, if the speakers move at all they'll be flexing the wall.

Take your nuts and plates to anyone with welding equipment. Ten times more solid than epoxy.

[Toolfan66]

First Guess: The Bass Brace is less effective than spikes.

IMO!!! Yes!!


[/QUOTE]Attaching a Bass Brace to a sheetrock wall seems to me like attaching it to an enormous drum skin, if the speakers move at all they'll be flexing the wall.[/QUOTE]

Not at all.

[/QUOTE]Take your nuts and plates to anyone with welding equipment. Ten times more solid than epoxy.[/QUOTE]

Or maybe I get off my ass and make some threaded plates!!!!

[Toolfan66]

Not sure what happened there!!!

[Schurkey]

Attaching a Bass Brace to a sheetrock wall seems to me like attaching it to an enormous drum skin, if the speakers move at all they'll be flexing the wall.

Not at all.

You'd be surprised at how stud-and-sheetrock walls are NOT rigid. Flexy-as-all-get-out. The speaker vibrates while connected to wall-anchors set into sheetrock, the sheetrock is JUST like the skin on a drum. Gets bad enough, the sheetrock will crack.

Connecting to a stud behind the sheetrock is somewhat better. Still not all that good.

Connecting directly to concrete; or to a stud glued-and-screwed to concrete is far better practice.



[/QUOTE]Take your nuts and plates to anyone with welding equipment. Ten times more solid than epoxy.[/QUOTE]

Not sure what happened there!!!

Too many [/QUOTE], not enough [QUOTE=Schurkey;1866733]

Or maybe I get off my ass and make some threaded plates!!!!

Excellent idea.

[Toolfan66]

Not everyone has concrete behind their walls. I do agree a stud would be better then just the sheetrock but I wasn't going to tear into my walls to put a stud in a certain place. Also mine have been in place for sometime now and I have no cracks...

The speakers would need to moving pretty good to crack a wall, and my speakers are sitting pretty solid. I have no worries about it..

[Schurkey]

I was going to construct my own braces from threaded rod and nuts epoxied to plates. It would allow me to turn the threaded rod within the nuts kind of like a turnbuckle, to fine tune it after speaker placement.

If you go this route, use "Connecting nuts" which are about five times taller than regular nuts. Gives you more room to thread the rod in 'n' out.

I can't find a link or photo, but I see them in Ace Hardware stores, and at big "home improvement" stores like Menards, Lowes, and Home Despot. They're a regular nut, but "long"; they're intended to connect two pieces of all-thread to make a longer assembly.

[F1nut]

Gives you more room to thread the rod in 'n' out.

The original Bass Brace was threaded into a nut on the inside of the cabinet, which allowed for the length adjustment.

[sda2mike]

Not sure what happened there!!!

yer tasting foot?

[Schurkey]

Not everyone has concrete behind their walls. I do agree a stud would be better then just the sheetrock but I wasn't going to tear into my walls to put a stud in a certain place. Also mine have been in place for sometime now and I have no cracks...

The speakers would need to moving pretty good to crack a wall, and my speakers are sitting pretty solid. I have no worries about it..

There are two issues as I see it:

1. Mechanical damage to the wall. You're right--it would take a fair amount of vibration; or maybe moderate vibration over the course of years to actually damage the wall.

2. Sound-quality issues related to turning large sections of sheetrock into the functional equivalent of a poorly-tuned and inefficient panel speaker. If the speaker vibrates, the vibration is transmitted to the wall. The wall vibrates in sympathy to the speaker cabinet. Sure, it wouldn't be much...but there's considerable surface area. I predict that it would muddy the bass, while not affecting treble at all.

If I wanted to use a Bass Brace on a stud-framed wall, I'd hang a 2X4 or 2X6, maybe even a 4X4 on the exterior of the sheetrock, the whole width of that wall. Stained, varnished, maybe veneered--or painted to match or to contrast (pretty, in other words); and call it "decoration". Kind of like a fireplace mantle. At least that way you've tied into multiple studs instead of just one directly behind each speaker--or (even worse) to the unsupported sheetrock.

[naturallight]

Now i may be totally wrong on this....This is what i remember about the "bass brace" It was never intended to do anything. It was an answer to people who said the speakers are too tall and can fall on you. This i believe is on the original SRS. Polk never designed this to do anything but pretty much keep the speakers from falling. They called it a bass brace, but was never in the original design to enhance anything. Again..i could be completely wrong on this...but that's what i remember.

[Schurkey]

Now i may be totally wrong on this....This is what i remember about the "bass brace" It was never intended to do anything. It was an answer to people who said the speakers are too tall and can fall on you. This i believe is on the original SRS. Polk never designed this to do anything but pretty much keep the speakers from falling. They called it a bass brace, but was never in the original design to enhance anything. Again..i could be completely wrong on this...but that's what i remember.

The way I remember it, the Bass Brace was invented to comply with a potential regulation regarding speaker tip-over. The potential regulation was never actually enacted; but the threat was there (for awhile). Like so many other "discoveries" it was determined after-the-fact that the brace did improve speaker sonics.

I'm sure there's a thread on this forum where I read/learned that story.

[Toolfan66]

You both are Correct!!!

As far as vibrations go don't the speakers vibrate the wall as it is? Humm yes they do!! So I don't see where adding the bass brace with a 1/4" piece of all thread is going to be any worse then what the speakers do already..

I find adding a piece of 4 x 4 or what not a little over kill and over thinking it..

I can tell you without a doubt that my speakers are solid and sound incredible..

Just my .02

[proffitt]

I was just thinking that as long as i have not yet built the wall, and I'm only 2 inches farther away from concrete than I am a stud....

But my worry was IF, (and this was a doubtful if)... if the brace was intended to "activate the wall"... I'd be missing out on the intent of the brace if i tied into concrete instead of "activating" the wall.

But that certainly doesn't sound like the case. Sounds like the sole purpose of the brace was to stabilize the speaker and force all movement from the magnet into the cone and let none disperse into moving the cabinet. Makes perfect sense.

I will spike.

I might brace, and if i decide to brace, since its so easy at this stage, i will go the extra 2 inches and tie into the concrete.

Thanks for your feedback!

[naturallight]

Yeah, thats pretty much how i remember it..something about a "proposed" regulation about the height of the cab, VS the base of the cab, and somebody said it will fall on you or some stupid thing like that.



Now weather putting a "bass bar" on a set of original SRS speakers..i'm not so sure there is really any sonic improvement...it was never designed to do that..if it dose..may be minimal at best.



To try and fix these to your 1/2" or 3/4" Sheetrock wall...well you better make dam sure..thats where the speakers work right. SDA's are not easy to place..so you better hope you have it right before you drill holes in your wall. Plus the fact if you change the "acoustics in the room..the SDA placement may not be right any more.



To me..the bass bar is a waste of time..never designed by Polk as a sonic improvement. Just spike the speakers...you can move them around to fit your room. But just my opinion on this..do what ever you like.

[naturallight]

To be blunt...you just can NOT pick out spots that you want to drill holes in your concrete basement walls.

The basement has to be finished, and with whatever stuff your putting down there.

THEN and only then can you select the proper space for the SRS's.

Once the basement is finished..then you can move the SRS's to the proper spot, were they will work right and sound the best, depending on what the basement size is and what the acoustics are. . Plus this will take some time. There not easy to place.



I mean..you can do what you want....but i just don't see this as a good idea to dril holes in the concrete..again just my opinion.

[Schurkey]

As far as vibrations go don't the speakers vibrate the wall as it is? Humm yes they do!! So I don't see where adding the bass brace with a 1/4" piece of all thread is going to be any worse then what the speakers do already..

If the speakers vibrate the walls based on air pressure spikes (sound waves), the dynamics will be essentially like an extremely-dampened curtain. The wall (or curtain flapping in the breeze) moves in synchrony with the air pressure; minus whatever time-delay takes place between speaker driver and wall based on speed of sound, and wall inertia.

Contrast that to a brace from speaker cabinet to wall. The rear wall movement is 180 degrees out-of-phase with the speaker driver. Speaker driver(s) move "out" of the cabinet (towards listener), back wall moves away from listener. The speed of sound is much faster through a solid bar than through air.

Big deal??? Probably not, but if I were going to do it at all, I'd do it so the cabinets were anchored to the most stable structure I could find or devise.

[Toolfan66]

If the speakers vibrate the walls based on air pressure spikes (sound waves), the dynamics will be essentially like an extremely-dampened curtain. The wall (or curtain flapping in the breeze) moves in synchrony with the air pressure; minus whatever time-delay takes place between speaker driver and wall based on speed of sound, and wall inertia.

Contrast that to a brace from speaker cabinet to wall. The rear wall movement is 180 degrees out-of-phase with the speaker driver. Speaker driver(s) move "out" of the cabinet (towards listener), back wall moves away from listener. The speed of sound is much faster through a solid bar than through air.

Big deal??? Probably not, but if I were going to do it at all, I'd do it so the cabinets were anchored to the most stable structure I could find or devise.

I can't disagree with you because I do agree with you, but I also don't feel it's worth all the extra work..

So I'm with you on one side of our little debate..

[motorstereo]

Why not just attach a piece of wood on top of the sheetrock to a pair of studs? Like a 6 or 8" wide piece of pine or 3/4" plywood. That would give the support you're looking for and won't vibrate the wall. The board could be routed and stained and also would be behind the speaker where it's really not that noticable. In my cases (2.3s and 1.2s) the bass brace made much more of a difference than spiking.

[PolkieMan]

Some day I'm going to find those spikes and try them The speakers are just so heavy

[Reagan]

I bought some inexpensive Parts Express spikes and cross-tapped the existing threads to 1/4-20. I then inserted 1/4-20 rod with 2 parts epoxy. They are solid. The problem was that no matter how I adjusted the 4 spikes, the monoliths would still wobble somewhat (on carpeted floor board) when I applied a little force. I decided to remove the back two spikes and add a single support brace to the back. With the speakers weighing 155 lbs, this results in 77.5 lbf vertical and 8.5 lbf horizontal on each of the two front spikes and (by my calculation) 17 lbf (in compression) on the back brace. I added a large washer between the brace and the speaker to spread the load. Of course, the braces are not appying force directly to the drywall but rather are resting on 2x4 reinforcements installed between the wall studs. The results are amazing! The monoliths are rock steady and don't budge even a little when I apply force. I find the bass to be tighter but it's still early in my listening.

[Mr. Bubbles]

to the OP. The answer may already be here but I didn't read all the posts all the way through. What is the floor made of? Is the wall facing already there or is it still studs?

The reason I ask these two questions is multifold. First lets define the primary purpose of spikes or braces of any kind.
The are intended to create a more solid coupling of the cabinet to the foundation or structure of the listening area ( in most cases this is the room (either walls or floor) materials since most people don't desire any major construction to achieve this. Imagine speakers like Focals best; they weigh in at many hundreds of pounds. This is not only for cabinet rigidity as this can be achieved with much lighter materials, but also to use that weight to couple the cabinets with the primary structure of the listening environment. back to my point(s). In most homes we have wooden beam/stud floors and walls covered in either Sheetrock or some sort of wood sheeting. most of the studs/ beams are much stronger than the panels of our speaker cabinets (for most speakers) and therefore can be used as external braces. Using spikes or braces gives a stronger more direct contact with the listening area structure than just sitting on boards or carpet. this in turn keeps the cabinet more stationary during driver acceleration and deceleration in doing this more detail can be achieved as the driver cones are not moving opposite of the cabinet movement and therefore the cabinet is not releasing energy out of phase with the driver. remember all this is theoretical and since we do not live in a perfect world these things are not 100% but do offer some benefit to the ends mentioned here. Now, on the other end of the issue; since most homes or listening areas are made of wood as mentioned before and themselves are not completely rigid, they too can release and transmit energy. I will keep the mathematics out of this but if you calculate the speed of sound through air and then through any solid material you will see that these are different. For this reason spiking sends energy through the floor that arrives at the listener at a different time than the energy in the air, and is the reason most people prefer spikes to braces ( the floor is almost always stronger than the wall) Bracing to the wall does the same (only the wall is generally no where near as strong as the floor). bracing to the wall and spiking now does this in an additive fashion. This is why it is not recommended to use both spikes and braces together. The deader, more resonant free the structure the less this is realized. This is why I asked my original question; you are dealing with an environment that most others don't have (concrete) and I assume that concrete is couple to the earth on the other side. If this is the case, it won't get much deader. If the floor is concrete as well it will not react the way a wooden structure would. I would personally brace and bond the wall structure to the concrete at several pints to deaden and strengthen the wall. This will not only give you a stronger wall to brace the speaker to once everything is finshed and you find the correct placement, but also change the way the wall releases the energy it absorbs through sound waves the drivers create in the air. Good luck and enjoy.

If you ever decide to get rid of these let me know. I currently have a set of SRS that get little use and I have been looking for some SRS 2's for some time. maybe we could work out some sort of trade. I am only about 4 hours from you.

[schwarcw]

I seem to recall a thread, I can't remember who posted a response but it quoted Matt Polk as saying the original intent of the brace was to keep the speaker from tipping over. But, they were surprised how much the bass improved when they did this. I also seem to recall the improvement was better than just spiking the speaker. I also recall reading where somebody said not to spike AND use the brace, although I don't know why. I have the brace but have never used it. I always thought if you could improve the way the brace attaches to the speaker and the wall, either by using a larger all thread with a steel plate inside the speaker, and a bigger plate to mount on the wall this would be a worthy "tweak".

I have the original spikes that do a nice job penetrating my carpet and padding down to the concrete floor. The bass response is very good and my SDA soundstage is very wide. I love these SDAs!!

[F1nut]

I used the brace in the past, spikes are better.