Custom Bookshelf Enclosure for 265 RT
Hi. I currently have a pair of Polk RT35i speakers with a CS400i center channel in my new theater build. You can see from the picture that I have the RT35i speakers in a cabinet and the CS400i in a nook. What I've noticed is that the speakers don't have the "warmth" that they did before I put them in the enclosed space and I suspect the rear facing PowerPort is the culprit.
I noticed that the speakers have a port in the front as well as the PowerPort in the rear. Could I plug the PowerPort or would that cause chuffing from the front port?
If I can't plug the PowerPort, I was thinking to replace them with front ported speakers.
Since Polk doesn't have too many front-ported speaker options, I was thinking to get three 265RT in-wall speakers and build a custom bookshelf like enclosure for each.
If I go this route, I have a few questions.
First, how big should the enclosure be? I think I read somewhere that backer boxes should be around 1 cubic foot. Is this correct? For the right and left speakers, I have a lot of vertical space to work with, so I could definitely go bigger than 1 cubic foot. For the center, the cabinet wouldn't be the same shape as the left and right. Would this matter as long as the internal volume was the same?
Second, would I need to worry about bracing?
Finally, should I fill the enclosure with polyfill? If so, how much?
I noticed that the speakers have a port in the front as well as the PowerPort in the rear. Could I plug the PowerPort or would that cause chuffing from the front port?
If I can't plug the PowerPort, I was thinking to replace them with front ported speakers.
Since Polk doesn't have too many front-ported speaker options, I was thinking to get three 265RT in-wall speakers and build a custom bookshelf like enclosure for each.
If I go this route, I have a few questions.
First, how big should the enclosure be? I think I read somewhere that backer boxes should be around 1 cubic foot. Is this correct? For the right and left speakers, I have a lot of vertical space to work with, so I could definitely go bigger than 1 cubic foot. For the center, the cabinet wouldn't be the same shape as the left and right. Would this matter as long as the internal volume was the same?
Second, would I need to worry about bracing?
Finally, should I fill the enclosure with polyfill? If so, how much?
Comments
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In general terms the best bass frequency response will be with as close as possible to 1 cubic foot. The shape of the enclosure won't be relevant, it is the internal pressure that is important. As to the amount of internal damping material, I have always recommended to try an experiment. Once you have built the enclosure place your face in the woofer opening and recite, "Polk speakers make fine music" and listen to how your voice sounds as it is reflected off of the interior surface. There will be a "box-like" resonant quality to the way your voice sounds. Add a medium sized quantity of damping material and repeat the same exercise and note how your reflected voice now sounds. Keep doing this adding small amounts of material until it begins sounding like you are speaking into a pillow. At this point remove some of the damping until you can hear a slight amount of reinforcement to your voice.
I hope this is helpful. -
I agree you need in wall speakers versus conventional speakers.
You also need to pull those subs out of those cabinets as it is just going to shake everything and sound terrible- Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit. -
@SeleniumFalcon thank you!
If I use 3/4" MDF and I build enclosures with internal dimensions 8" wide, 10" deep and 22" tall, that should put me slightly over 1 cubic foot (assuming I did my math correctly).
Do I need to worry about bracing?
Also, do you know if 8" is enough width to allow the 265 RT to be securely installed in an enclosure? -
@VR3
I double drywalled and used Green Glue in the nook. There are very few vibrations, but unfortunately I had to replace my PSW505s with SVS PB1000 Pros as the rear ports in the PSW505s gave me similar issues to what I'm having my with RT35i and CS400i.
When I built the room, I wanted as clean a look as possible, so pulling the subs out is not an option for me. So far the SVS subs are working well. I could potentially build some DIY subs in the bottom halves of my cabinets if I absolutely have to, but that might cause too much noise to escape the room as the cabinets are screwed into studs which would just transfer vibrations to the rest of the house. -
Crutchfield has these as the cutout dimensions:
Cutout Width 7.25"
Cutout Height 19.1875" (not sure why anyone would need four decimal places)
Mounting Depth 3.75"
Most speakers can benefit from rigid internal bracing.
Good luck with your project!
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"... do you know if 8" is enough width to allow the 265 RT to be securely installed in an enclosure?"
The speaker uses "dogs" which rotate around and drawn inward to grip the inside of the mounting surface. You can figure that each dog needs about 1" for rotation, so to be safe, a 9.25" width would be good.
