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I'm having custom cabinetry built around my RPTV, so I'm wondering if there are there any considerations for placing speakers in cabinetry?


Specifically:

-Do the speakers need to be front-ported, or can they be rear ported (such as the BW CM series)?

-Should the speakers be be insulated/dampened in any way?

-Can I cover the cabinet enclosures in fabric, and are there special fabrics for this purpose?

-What should I know about putting a subwoofer in the cabinet?


Any advice to a newbie is much appreciated!
 

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Quote:
Originally posted by SilverScreen
I'm having custom cabinetry built around my RPTV, so I'm wondering if there are there any considerations for placing speakers in cabinetry?


Specifically:

-Do the speakers need to be front-ported, or can they be rear ported (such as the BW CM series)?

-Should the speakers be be insulated/dampened in any way?

-Can I cover the cabinet enclosures in fabric, and are there special fabrics for this purpose?

-What should I know about putting a subwoofer in the cabinet?


Any advice to a newbie is much appreciated!
SilverScreen,


As long as the port is vented to the room with minimal resistance - you should be OK. If the speaker is a tight

fit and the port is essentially trying to pressurize the air trapped behind the speaker, or if you are venting the cabinet

via a long tube - then it will have an effect on the sound. The vent needs to be able to "breathe".


You also might look at "acoustic suspension" speakers to aviod the problem.


If the speaker is in a cabinet, you need to make sure the cabinet is not adding reflections. You don't want a speaker

in a cabinet surrounded by a big empty cavity. You should stuff the cabinet full of sound absorbing material in this

case. Don't bury the speaker deeply in the cabinet - you'll get reflections off the cabinet sides.


The cabinet can be covered with speaker grille cloth.


The subwoofer will be less problematical than the main speakers. The wavelengths of the sound produced by the sub

will be much greater than the dimensions of the cabinet. In general, waves are not greatly influenced by objects that

are smaller than their wavelengths.


Dr. Gregory Greenman

Physicist
 

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Hi SilverScreen,

Quote:
Originally posted by SilverScreen
I'm having custom cabinetry built around my RPTV, so I'm wondering if there are there any considerations for placing speakers in cabinetry?
There certainly should be some considerations made, unfortunately many overlook little details, even though they would be very easy to implement or require relatively minor changes.

Quote:


Specifically:

-Do the speakers need to be front-ported, or can they be rear ported (such as the BW CM series)?
For building into a cabinet, I would look for front porting, or a sealed design, but there are ways you can help things out or work with a speaker with a rear port, but in most cases it is a compromise. With a conventional wide dispersion speaker, you will typically have a great deal of sound radiated back into the cavity the speaker is placed in, which can produce a very "boxy" sound which will vary related to the size and dimensions of the cavity the speaker is placed in. For such installations, I prefer to not permit the speaker to direct any energy into the cavity. Since the cavity does have to have some room for manuvering, and many people want the ability to upgrade down the road, I prefer effectively making a baffle for the speaker rather than just making a tight fit. When I say to create a baffle, this basically means that the speaker rests directly up against or very near the grill, where wood, hardboard or similar mates up to the face of the speaker, and foam usually helps create an acoustic seal allowing the sound to only project forward, not back into the cavity. If you wanted to go to larger speakers down the road, presuming the cavity is large enough, you only have to re-work the opening in the grill. Probably the most common screw up I see is having the frame/trim of the grill obstruct the mid or high frequency drivers of the speaker. This may require re-designing of grills, or simply building a small stand for the speaker to sit on, giving it a clear opening.


I would like to note that such mounting WILL change the sound of a speaker, generally augmenting the bass response in the lower midrange. Some companies design speakers to work well in this sort of built-in situation. Any speaker designed to be placed up against a wall should also work well. Triad, Aerial, Snell and NHT as an example all make speakers either designed for, or with adjustments to allow this sort of installation.

Quote:
-Should the speakers be be insulated/dampened in any way?
Most cabinets will be somewhat resonant, and if vibrations are mechanically coupled to the shelves, they can be conducted to the outer panels and make audible noise. Mildly soft(relative to the weight of the speaker) rubberized feet of some sort are my preference as they also keep the speaker from moving at all. For the sake of being thurough, I would also fill the space between the speaker and the cavity walls. Egg-crate styel foam or fiberglass batting of some sort can work fine. The better the speaker is coupled to the baffle, the less this matters.

Quote:
-Can I cover the cabinet enclosures in fabric, and are there special fabrics for this purpose?
There are companies which make fairly transparent fabric, but you can sometimes get lucky and make a good find at a fabric store. Basically hold it up and speak through it, if it changes the sound, it's going to do the same to your speaker. My suggestion above to build a baffle will help to also keep the fabric taught and supported, where larger grills with pictureframe structure only will often sag, depending on the fabric used.

Quote:
-What should I know about putting a subwoofer in the cabinet?


Any advice to a newbie is much appreciated!
Subwoofers have the benefit that the low frequencies they produce are not affected much by small obstructions. If it is a standard front firing subwoofer, it's pretty simple. For other boxes with side or down firing woofers, you can still build them in, allowing for proper clearances. In the case of a subwoofer, you do have to consider that unless all drivers are opposing eachother like in our ContraBass, Martin Logan's Balanced Force subwoofers, or Mirage's bi-polar subs, there will be significant cabinet vibrations. In the ideal you don't want these to be coupled to the cabinet as it will both shake things sitting on it, and possibly make noise of it's own. This means that direct cabinet contact to the subwoofer is what we want to avoid. Since the subwoofer typically goes at the floor, I usually have that section built without a bottom, or with a large enough opening to allow the sub to sit inside. This way the only coupling is mechanically through the floor, and acoutsically in the air, both of which will be much less severe than when directly in contact. For cosmetic and sometimes acoutsic or clearance reasons, you may need to place a small stand under the sub to keep the base molding or floor of the cabinet from obstructing a driver or port. Usually it's not a problem.


Since you are likely also placing all of the electronics in this cabinet, do some serious thinking about how you will access your gear, and even cable management. i.e...How will I get the cable from here to there? There are some great ways to completely conceal all the cables which a few cabinet and rack manufacturers have done, so check others out and look for ideas.


Finally, and quite importantly, cabinets vibrate! Plan on foam bumpers on all doors and drawers. You don't want the cabinet to start rattling when the sub gets going. Also do some thinking on how you mount any glass in he cabinet, as you don't want it rattling, so it must be firmly secured, not just resting in a slot. In general, do as much hunting for potential rattles BEFORE everything is done and together, as sometimes you can't change things at that point. An experienced cabinet maker should be able to come up with some good solutions so long as you bring such issues to their attention ahead of time.


Regards,
 

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What if you don't have a cabinet, but are just trying to conceal the speakers. i.e. I will have a minimal frame on my stage wrapped in fabric.


See Post for more details.
 

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topaz,


Your application is along the lines of what is often referred to as a "shadow box." The idea being that you don't see items sitting out in the room, but you maintain the benefit of free placement to achieve best sound. The idea is for the fabric "wall" to be acoustically transparent. In the case above with a cabinet, the cabinet's structure is anything but transparent.


In your case what I would plan to do is put some form of acoutsic treatment around the sides of your RPTV to reduce acoustic reflections from the mains off the set. I would also acoutsically treat almost all of the front area behind the fabric framing.


Where there are similarities to my comments above is in the framing and placement of speakers. You want the majority of the area in front of the speaker to have no obstructions other than the fabric. Where you do have the framing, I would again treat the inside of it to eliminate reflections which skew the image and call attention toward the objects reflecting.


Hope this helps,
 

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Mark,


So I should do the following:


1. Put TheaterSheild, or equivalent over the drywall on the front wall.

2. Build a minimal frame around the RPTV and speakers.

3. TS the left and right side of the RPTV.

4. Butt the speakers right up against the fabric that I will pull.


Does sound correct?


One more thing, the unfortunate part of my room is there is a door on the right side of the front wall. Sould I put the TS on the door and above it or would I not notice a difference?


Also, I'm planning on a small soffit above the RPTV to hide a future power screen. See any issues with this?


Thanks again for the great information,

Topaz
 
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