Audax PR170M0 and breakup modes - diluted PVA glue, damar, Mod Podge... ?

Saurav · 6th May 2004, 07:58 PM

Hi,

I have a paper cone midrange driver with breakup modes that I'd like to try and tame. Based on what I've understood so far, one approach would be to use products like diluted PVA glue or latex, which would damp the cone, at the expense of added mass and reduced efficiency. The other option would be to use damar (or maybe even shellac) which would stiffen the cone, which hopefully might push the breakup modes out to a high enough frequency that they're fairly attenuated by the crossover.

Here's the FR plot of the driver:

The peaks start at around 3kHz, and go out to about 8kHz. My XO right now is a 2nd order electrical, set for I think a target 4th order acoustic slope at 5 - 5.5kHz.

First of, does anyone have experience or information on successfully doping this specific driver? That would be the most helpful, I think, both the stuff that worked and the stuff that didn't work. Failing that, any general information based on theory or experience with other (hopefull similar) drivers would be most appreciated too.

And of course, I'm open to suggestions for non-doping solutions. In fact, reversible mods would be preferred, because at least I could try those first. I've seen people mention foam/felt rings on the surrounds, but I'm not too clear on how those are mounted.

Thanks,
Saurav

thylantyr · 6th May 2004, 08:45 PM

Have you listened to the driver without doing any modifications?

I think this driver sounds great 'as is', even without low pass
filtering.

Mark25 · 6th May 2004, 09:22 PM

if you were feeling adventurous you could goactive with a 24dB/oct electronic X-over. The reputation of this driver would make me wary of modifying it, i'm not saying it can't be improved, but........
M.

Saurav · 6th May 2004, 09:47 PM

The reputation of the driver is why I haven't touched it yet

I know, it sounds great, I've been listening to it for a couple of weeks now with somewhat temporary crossovers. I don't have enough amps to go active between the mid and the tweeter. I have active XOs between the mid and the woofer, and between the woofer and the sub.

Maybe that's the best option, just do the best I can with the XO and leave the driver untouched?

Quote:

I think this driver sounds great 'as is', even without low pass filtering.

Now that is something I haven't tried. I know people add tweeters/supertweeters up really high to full-range drivers, maybe even make them top-firing or rear-firing. I wasn't sure if I could do something similar with the PR170M0, but your post seems to indicate that you ran it with no low-pass filter? I was thikning about this last night, because it would be a pretty easy change to the XO to try this out. If you have tried this, did you use a supertweeter? If you did, what frequency and slope did you bring that in at?

Thanks,
Saurav

Ap · 6th May 2004, 11:41 PM

Xover at 5.5k- Why so high?
As it is a 6.5" I would try & bring it down to about 3k where it's oiff-axis resonse is still acceptable. This may also negate the need for damping.
I have seen Duntech & VAF Research (both Australian) use felt glued to the cones.

Saurav · 6th May 2004, 11:49 PM

Because I picked a tweeter without really thinking far enough ahead, and I wanted it that high so that the effects of my crossover wouldn't be right in the critical frequency region (this is my first attempt at designing a speaker). If this doesn't work out I'll try different tweeters that can go lower.

Ap · 6th May 2004, 11:54 PM

Xover at 5.5k- Why so high?
As it is a 6.5" I would try & bring it down to about 3k where it's oiff-axis resonse is still acceptable. This may also negate the need for damping.
I have seen Duntech & VAF Research (both Australian) use felt glued to the cones.

woody · 7th May 2004, 12:40 AM

I am also a little reluctant to do anything to the pr170mo,
yet I used some THICK silicon oil on the cone and spider
of a pair of 1197`s and was verry verry pleased with the
results.

Woody

Saurav · 7th May 2004, 01:39 AM

Did you notice any drop in efficiency? Does this oil soak into the paper of the cone, or does it sit on the surface? And how did it change the sound?

robertwb70 · 7th May 2004, 04:10 AM

Suarav and I already discussed this some but maybe someone here has actually tried this idea?

what about using cyanoacrylate(super glue) as cone dope?

6th May 2004, 07:58 PM	#1
Saurav diyAudio Member Join Date: Sep 2002 Location: Oregon, USA	Audax PR170M0 and breakup modes - diluted PVA glue, damar, Mod Podge... ? Hi, I have a paper cone midrange driver with breakup modes that I'd like to try and tame. Based on what I've understood so far, one approach would be to use products like diluted PVA glue or latex, which would damp the cone, at the expense of added mass and reduced efficiency. The other option would be to use damar (or maybe even shellac) which would stiffen the cone, which hopefully might push the breakup modes out to a high enough frequency that they're fairly attenuated by the crossover. Here's the FR plot of the driver: The peaks start at around 3kHz, and go out to about 8kHz. My XO right now is a 2nd order electrical, set for I think a target 4th order acoustic slope at 5 - 5.5kHz. First of, does anyone have experience or information on successfully doping this specific driver? That would be the most helpful, I think, both the stuff that worked and the stuff that didn't work. Failing that, any general information based on theory or experience with other (hopefull similar) drivers would be most appreciated too. And of course, I'm open to suggestions for non-doping solutions. In fact, reversible mods would be preferred, because at least I could try those first. I've seen people mention foam/felt rings on the surrounds, but I'm not too clear on how those are mounted. Thanks, Saurav

7th May 2004, 04:10 AM	#10
robertwb70 diyAudio Member Join Date: Nov 2003 Location: Sanford,FL	Suarav and I already discussed this some but maybe someone here has actually tried this idea? what about using cyanoacrylate(super glue) as cone dope? __________________ "The appreciation of music is subjective.The reproduction of music isn't."-Bill Dudleston

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6th May 2004, 08:45 PM	#2
thylantyr diyAudio Member Join Date: Feb 2001 Location: Mars	Have you listened to the driver without doing any modifications? I think this driver sounds great 'as is', even without low pass filtering.

6th May 2004, 09:22 PM	#3
Mark25 diyAudio Member Join Date: Feb 2002 Location: The Netherlands (Friesland)	if you were feeling adventurous you could goactive with a 24dB/oct electronic X-over. The reputation of this driver would make me wary of modifying it, i'm not saying it can't be improved, but........ M.

6th May 2004, 11:41 PM	#5
Ap diyAudio Member Join Date: May 2002 Location: Sydney, Australia	Xover at 5.5k- Why so high? As it is a 6.5" I would try & bring it down to about 3k where it's oiff-axis resonse is still acceptable. This may also negate the need for damping. I have seen Duntech & VAF Research (both Australian) use felt glued to the cones.

6th May 2004, 11:49 PM	#6
Saurav diyAudio Member Join Date: Sep 2002 Location: Oregon, USA	Because I picked a tweeter without really thinking far enough ahead, and I wanted it that high so that the effects of my crossover wouldn't be right in the critical frequency region (this is my first attempt at designing a speaker). If this doesn't work out I'll try different tweeters that can go lower.

6th May 2004, 11:54 PM	#7
Ap diyAudio Member Join Date: May 2002 Location: Sydney, Australia	Xover at 5.5k- Why so high? As it is a 6.5" I would try & bring it down to about 3k where it's oiff-axis resonse is still acceptable. This may also negate the need for damping. I have seen Duntech & VAF Research (both Australian) use felt glued to the cones.

7th May 2004, 12:40 AM	#8
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	I am also a little reluctant to do anything to the pr170mo, yet I used some THICK silicon oil on the cone and spider of a pair of 1197`s and was verry verry pleased with the results. Woody

7th May 2004, 01:39 AM	#9
Saurav diyAudio Member Join Date: Sep 2002 Location: Oregon, USA	Did you notice any drop in efficiency? Does this oil soak into the paper of the cone, or does it sit on the surface? And how did it change the sound?