Tweeters: Flush mount or felt ring?

StevenZ

StevenZ

Texas or nothin'
Hey guys,

I had recently come upon a build thread where instead of flush mounting the tweeter, the guy built up a felt ring around the mounting flange. Do any of you guys have an idea of how this affects the sound vs flush mounting the tweeter with no felt ring? I'd be interested to know the difference, both positive and/or negative.


Thanks,
Steven
 
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The felt will help. you should when ever possible flush mount and place the tweeter off axis to the mid or mid/woofer so that it is not in line with the centre of the cabinet as this makes the diffraction frequency the same on both sides of the cabinet. Manufacturers put them in the centre so they don't have to build and stock left and right speakers. Listen with and without felt and then you will know for yourself. Don't use synthetic felt as it is nowhere near as good a 100% wool felt SAE rated F - 11 acoustical felt is the best that you can use as it has the widest possible absorption coefficient of any felt you will find. Buy it and use it only as it is the best, why pay for second best? Good luck have fun best regards Moray James.
 
I just posted somewhere else that felt on the baffle can make an easily measurable difference regardless of the tweeter mounting. Not just next to the tweeter, either. I think it's well established that flush mounting is good.
 
Thanks for the reply, Moray. I had found some 100% wool felt at a nearby hobby store and was thinking about using it. It would be much easier to surface mount the tweeter and then put a felt ring around it than to flush mount. Though, if you say that flush mount with no felt will be better than surface mount WITH felt, I'll just suck it up and flush mount the tweeter as per original plans.

I just wanted to put a feeler out there for anyone who has possibly done both variations and could report back on their findings.


Cheers,
Steven
 
dumptruck said:
I just posted somewhere else that felt on the baffle can make an easily measurable difference regardless of the tweeter mounting. Not just next to the tweeter, either. I think it's well established that flush mounting is good.
Click to expand...


Yeah, I've always flush mounted my tweeters, and to be honest, it was in that very thread that I was inspired to use the felt rings around a surface mounted tweeter vs flush. From the limited information I've gathered on various sources from Google, the felt does do a great job at isolating the tweeter and reducing diffraction. So I'd assume that as long as the felt is a tad bit proud of the tweeter, I'd be okay to surface mount.

I should probably get some measuring equipment to test it for myself.

-Steven
 
dumptruck said:
Hey... don't you have a CNC anyway?
Click to expand...

Yes, but in this case, the tweeter flange is only 1/8" deep and it's a real bitch to veneer over the opening. I'm not big on wetting the veneer and then using a razor to free hand the flush rebate opening. Though, I could veneer the front baffle first, machine it, then lay up the sides/top/back afterwards. But that'll leave me with visual edges of the veneer on the face which is a big no-no. Decisions decisions....
 
If you're covering with felt, I can't imagine surface mounting or flush mounting is gonna' make a difference either way.

+1 on using WOOL felt.
 
Ohighway said:
If you're covering with felt, I can't imagine surface mounting or flush mounting is gonna' make a difference either way.

+1 on using WOOL felt.
Click to expand...

Well, that's the thing, I won't be covering or on the flange at all. I'd be making a ring around it with felt. Basically the tweeter and flange would be sitting on the surface of the enclosure, then along the perimeter would be a 1"+ ring of felt.

Edit:
Although, covering the entire enclosure with felt would be interesting, too.:scratch2:
 
I was kind of assuming the felt would cover the entire tweeter face -except- for the area of the dome itself.

On my EV Interface C speakers, the tweeter was foam covered, and the foam covered the entire tweeter surface except where the dome peeked through.

I'd think it would work best that way.
 
Measurements of felt rings origanally linked from Sir Byrd's Danish Speaker thread.

I've used felt inside boxes but never around a dome tweeter. Got to give that a try. My BLH's have a suprabaffle of synthetic leather and I don't hear a bit of difference, with or without. I know JBL used foam rings on monitors and NHT had rings on their bigger fkoorstanders. Sure didn't seem to hurt anything. Heck, I think Ill cut some rings and stick 'em with some carpet tape. Might even fire uo the measuring gear for this :scratch2:.
 
westend said:
I've used felt inside boxes but never around a dome tweeter.

Heck, I think Ill cut some rings and stick 'em with some carpet tape. Might even fire up the measuring gear for this :scratch2:.
Click to expand...

And report on the findings..... right??!! :thmbsp:
 
Covering the entire baffle in felt should do something different (and I would guess usually better) than just a ring or etc. I know I've seen it measured once online. I don't have nearly enough felt around to measure it on anything here.
 
StevenZ said:
Well, that's the thing, I won't be covering or on the flange at all. I'd be making a ring around it with felt. Basically the tweeter and flange would be sitting on the surface of the enclosure, then along the perimeter would be a 1"+ ring of felt.

Edit:
Although, covering the entire enclosure with felt would be interesting, too.:scratch2:
Click to expand...

If you have the ability mount the tweeter inside the cabinet behind the baffle rater than on the front of the baffle then fill the hole in the baffle with built up felt. This will give you some time alignment and will sound better. If you can align the tweeter top plate (centre line) with the mid or woofer top plate (centre line) you will notice much better focus of image. You can test this out on top of the cabinet first if you like as a trial run. I time align my big horns this way (Peavey CH-1) and it makes a huge difference.
 
moray james said:
This will give you some time alignment and will sound better.
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Potentially, but if the crossover was designed to bring the drivers into time alignment even though the tweeter is physically forward, or designed to flatten on-axis response despite the lack of alignment, it will sound worse.

If this is the SR71 that we are talking about, the case appears to be some of both, but regardless the forward lobe is pretty much straight ahead, i.e. you don't want to change the driver mounting from how Zaph did it at all. It does seem to be sending a little more off-axis HF toward the floor, which makes me think they might sound better upside down, but it appears to be an ear-level speaker either way.

SR71-modeled-polar-1500blue-2500red-100step.gif


P.S. Also, when you don't have the sharper off-axis cutoff of a horn, those new edges from behind-baffle mounting are a bigger problem.
 
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Ohighway said:
And report on the findings..... right??!! :thmbsp:
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Well I'd like to report the findings but I'm kind of new to this measurement stuff and can't seem to find a way to get the files in a format that can be shared. I was using REW 5 and the files save into a .mdat format, something Photobucket doesn't recognize. Got some help for me?

The test mule, Boston A-40:

IMG_0001-50.jpg


Felt in place:

IMG_0002-30.jpg


Edit: OK, the "capture" button, who knew? These ae SPL 1/12 octave smoothed. Gold is felt, Red is no felt:

felting3.jpg




I still have a bad cal file so my signal levels are low but the graphs are in relation to each other. I'll try to recalibrate and see if I can get those DB levels up.

Edit 2: Higher DB Orange-no felt, Goldish-felt 1/24 smoothing:

dbup.jpg
 
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StevenZ said:
Yes, but in this case, the tweeter flange is only 1/8" deep and it's a real bitch to veneer over the opening. I'm not big on wetting the veneer and then using a razor to free hand the flush rebate opening. Though, I could veneer the front baffle first, machine it, then lay up the sides/top/back afterwards. But that'll leave me with visual edges of the veneer on the face which is a big no-no. Decisions decisions....
Click to expand...

Why not build a jig that will index on the edge of the finished cabinet, and cut the tweeter recess with a router? That will let you hide the veneer edges, but not have to freehand or veneer over an opening.
 
doors666 said:
for the tweeter, the response looks pretty much identical
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Yes, I think we can say with insurity that, after much goofing around and measurements, it doesn't make a lot of difference ....or, it might tame some of the brightness of an overly bright tweeter (not all that is heard turns up in measurement) :D Conclusion: Not much difference but at least we tried something new.
 
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