RS Center Wm/tW, Q's about standing waves

[Raptor550]

I have all crossovers and woofers purchased. In order to reduce any internal standing waves in my CC I thought it would be a good idea to make the internal walls of the mid/tweeter enclosure with a slanted back, and side walls bent out giving what would be a standing wave a spiral motion. I would be sure to keep the internal volume, and the front baffle the same.

I am intending to make #1 either like #2 or #3. what would be better? the depth behind woofer in 2 or the up angle of 3?

How might these changes affect the sound? I am probably going to do this to match my Slanted NatP's anyways but was curious to get professional opinion.



If all goes well my setup will look like below when finished:

[ThomasW]

#2 is the best if you're trying to reproduce the lowest bass.

A or B? Well if you really like cutting compound complex angles go for B. But with proper damping I doubt you'd hear a difference between them.

[Raptor550]

Thank you for the advice Thomas. Proper dampening? Like wispermat or sonic barrier? Would A and B be different given an equal amount of dampening?

Cuts a bit harder are worth the extra effort for me, I've done it before. If somethings going to be THAT huge in the center of my room I might as well try to pass it off as modern art! I already plan on putting Sonic barrier and insulation inside.

PS. anyone know where to get thin strips of brass? I have searched home depot and all over online and cant find any. I want to use them to give my boxes a streamline look. dosn't have to even be real brass so long as it dosn't look like paint.

[ThomasW]

IMO proper damping is fiberglass.

The difference between A&B is splitting hairs regardless of the amount of damping.

Look in your local yellow pages under 'metals' for brass suppliers. I'm sure McMaster-Carr has it online, but they're $pendy..

[Curt C]

Thank you for the advice Thomas. Proper dampening? Like wispermat or sonic barrier? Would A and B be different given an equal amount of dampening?

Cuts a bit harder are worth the extra effort for me, I've done it before. If somethings going to be THAT huge in the center of my room I might as well try to pass it off as modern art! I already plan on putting Sonic barrier and insulation inside.

PS. anyone know where to get thin strips of brass? I have searched home depot and all over online and cant find any. I want to use them to give my boxes a streamline look. dosn't have to even be real brass so long as it dosn't look like paint.

I agree with Thomas. Properly stuffed I doubt you will hear any difference due to the enclosure variations.
I would suspect the midrage sound could be improved with a larger midrange enclosure, though...

C

[djg]

Brass

A good hobby shop will have brass stock probably up to 36" length.

[Raptor550]

Really curt? How much larger would you go on the midrange to be optimum? I plan to have sonic barrier on the back and sides and fiberglass everywhere else - or should I reverse that?

I will check out some hobby shops when I fly back home. Mcmaster looks promising if nothing else is cheaper, Thank you.

Tweeter X-over is now complete, onto the midrange! Pics to come

[Hdale85]

Look for a local metal shop we have a place here in Pittsburgh that will cut anything I want to size and everything. Great customer service through emails or phone as well. But as they said Mcmaster Carr has that stuff as well

[David_D]

As far as the brass goes, Try a crafty store, like hobby lobby or micheal's. I think every micheal's I've been in has had hobby brass sheet metal by the balsa wood.

[Curt C]

Really curt? How much larger would you go on the midrange to be optimum? I plan to have sonic barrier on the back and sides and fiberglass everywhere else - or should I reverse that?

I probably shouldn’t have brought this up, as this is an established design, which many have built and are happy with, so just consider this to be my personal preference.

It apears the back of the RS150 is only 3.5” from the rear wall, and by necessity, very near the side and bottom walls as well, only being ‘open’ above the driver. IMO, a little extra breathing room behind the mid certainly couldn't hurt, and would allow addtional stuffing to attenuate the energy off of the back of the cone. As we discovered in the Statements, putting the foam too close to the driver made the sound dull and lifeless, but due to the differences in designs, may not be a potential issue here.

C

[ThomasW]

I plan to have sonic barrier on the back and sides and fiberglass everywhere else - or should I reverse that?

No need to use both in combination for the woofers. Pick one thing and use it, that's all you'll need.

As Curt indicated the midrange damping is more critical.

[---k---]

IMO, a little extra breathing room behind the mid certainly couldn't hurt, and would allow addtional stuffing to attenuate the energy off of the back of the cone.

C

Curt,
I don't know if you saw it in my Khanspire thread, but I found the mids to be very sensitive to stuffing. CJD has also experienced this.

The Khans have a little bit bigger mid enclosure, with the back being 6" away. The mid is lined with 1" OC703. When I put just a little bit (3-4 fist fulls) of acoustic stuff in the mid chamber it attenuated the RS150 and made it very forward. I thought I had something wrong with the crossover, because I had just redone them. But, pulling our ALL the stuffing returned it to what I was used to (and what you heard in Iowa).

CJD isn't sure why the RS150 is so sensitive. Just a caution that everyone should experiment with it.

[Jim Holtz]

Not to get off the original topic but I did want to chime in with a few thoughts.

I've been a proponent since I first started building DIY speakers to have as deep of mid enclosure as the cabinet will allow. I'd much rather have the mid enclosure tighter on the sides/top/bottom than a shallow one. I've never felt or had any of the folks that design crossovers for me comment on mid range issues due to reflection of back waves in cabinets I've built. The deep enclosures might be why I'm able to get good results using foam rather than fiberglass or Sonic Barrier too. Who knows? :huh:

As Curt pointed out, the Statements development highlighted how critical the mid damping was to the overall sound.

Jim