phase plugs for b&w kevlar driver

[burnsy1]

Hello All,

My first post here....please be gentle. My daughter recently had her way with my b&w lcr600 s3. More specifically she crunched the dust caps on the two kevlar drivers. The dust caps come to a point.... and actually look like phase plugs...though they are not. They aren't pushed in....she actually crunched them on the sides...Also....turns out that my grey dust caps...are actually painted gray...they are clear underneath. I know this because she somehow managed to chip off a fair amount of the paint.

Neways... I found that I can pay 100 bucks per speaker to replace the two kevlar drivers...but thats a bit hard to swallow considering the speakers still appear to work...well enough. But I can't stand to look at them... I like (liked) having the covers off.

More to the point now ..I was wondering if anyone had ever tried putting phase plugs in place of the dust caps on the b&w drivers....or other kevlar drivers. The dust caps appear to be glued. I'm tempted to try to remove them but am hoping someone can offer some words of wisdom before I dive in.

Thanks for any help\info

[Iain McNeill]

How do they sound?

Sometimes, these dings don't make a lot of difference in sound. If you're hearing buzzing or missing bands then you're in for some cash.

However, before you give up on them, try reforming them. I've heard of people fixing cones/domes with a number for ways. Blutack-that stuff for sticking pictures on the wall can be used to pull out dings. Scotch tape (sellotape) can also work. You can remove the driver and see if there's a way to apply back pressure by blowing whilst holding the cone still to pop out the dings. Get creative - the worst thing is you'll bugger the driver up - which it is anyways

If all else fails, I'm sure you'll get some good advice for replacements.
good luck!

Then Dave (Planet10) might have an opinion too

[Nanook]

any piece of suitable dowelling, cut to length, with a couple of Robertson screws screwed into the back side can make a nice phase plug...a´la P10

as far as Ian and his signature line : crossover = coiled wire with loss--get ye a fullrange driver

[roger_lew]

Yeah phase plugs might work. Although it might not be a perfect solution. The phase plugs would need to match the geometry of the original dust cap phase plugs.

Keep in mind that having phase plugs rather than dust caps means that the cone is slightly lighter which means that all the speaker parameters will change slightly. For instance, the resonant frequency will be higher, which will make qms and qts slightly higher. These changes have subtle, but predictable effects on the low end frequency response. The effects the modifications will have on the midrange response are less predictable. Closely matching the geometry of the dust caps will help mitigate changing the frequency/polar response too much.

In terms of resale value you might be better off just replacing the drivers. You might also consider selling your crunched drivers in the swapmeet forum to offset your cost. There are people here that have the equipment and expertise to replace the dust caps, or put in some phase plugs, measure the modified drivers, and use those parameters to optimize a speaker around them. Unfortunately in your situation, the chances the phase plugs will improve the speaker are not very good, your really just hoping to not degrade it too much.

my 2 cents

[roger_lew]

P.S.

Generally speaking sound comes first here, aesthetics are a distant second.

[burnsy1]

Thanks for the help....I was able to get some of the dents out by using tape. I think I'll try removing the drivers to see if I can push the dust caps out somehow from behind.

I haven't noticed any difference in sound quality, though in general I've felt this speaker does not sound as "brilliant" as the towers in the same range...which doesn't make much sense to me. They are supposed to have the same tweeter.

If I am able to get the caps pushed out all the way...any suggestions on what type of paint I might use to repaint over where its been chipped off?

[Iain McNeill]

Originally posted by Nanook
get ye a fullrange driver

Funny you should say that, Stew



Not sure if I'll get them to Dave's this summer tho

[burnsy1]

Thanks for all the help and suggestions. I tried removing the speakers to see if I could somehow get the caps pushed out from behind...it wasn't possible. I was able to get some of the dent out of one of them with scotch tape.

I've attached a picture, it's not for the faint of heart..this is actually before i was able to get some of it back out.

[planet10]

Those look pretty much toast.

To retain value you need to get factory replacements... but nothing stopping you from playing with these. Time to get the razor knife/scalpel out. (i recommend a proper craft one, not a box cutter)

dave

[chris661]

Hoover it.

That's saved speakers lots of times for me when "mates" have been out poking.

This might be a long shot, but could you take them off, get them back to shape, then restick?...... I said it was a long shot.

As I said before - get a hoover, put it over the dustcap, switch it on. DO NOT pull it off. Wait for 5 secs, then switch off the hoover. Then remove the nozzle. Note - must be a reasonably powered hoover.