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
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:
An externally hosted image should be here but it was not working when we last tested it.
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
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?
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
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?
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
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.
This driver sounds good with no filtering, therefore it's
an easy driver to work with and you can pretty much
do what you want with the crossover points. Whatever
sounds good to you. I guess it's easier when you have
a test bench with an active crossover setup so you can
sweep various crossover frequencies to see what you like.
In my case, I start with tweeter first and work down.
I like my tweeters (any tweeters) to operate between
2-2.5khz, it's my personal preference. Crossing the midrange
at his point is not a problem. The slope? What sounds good
to you? I prefer 12db up to 24db for tweeters. If it's high SPL
application, then I use the higher slope.
Active setup is more expensive, but the real time tweakabiliy gives
you peace of mind because you can locate the 'best sound'
really fast without juggling passive crossovers around --
turn the dial
an easy driver to work with and you can pretty much
do what you want with the crossover points. Whatever
sounds good to you. I guess it's easier when you have
a test bench with an active crossover setup so you can
sweep various crossover frequencies to see what you like.
In my case, I start with tweeter first and work down.
I like my tweeters (any tweeters) to operate between
2-2.5khz, it's my personal preference. Crossing the midrange
at his point is not a problem. The slope? What sounds good
to you? I prefer 12db up to 24db for tweeters. If it's high SPL
application, then I use the higher slope.
Active setup is more expensive, but the real time tweakabiliy gives
you peace of mind because you can locate the 'best sound'
really fast without juggling passive crossovers around --
turn the dial
Thanks. I tried running the midrange full-range last night, with a single cap on the tweeter to bring it in at around 8kHz. Then I tried a resistor on the midrange to lower its level, and then tried replacing the resistor with an inductor (again, set for around 8kHz). None of these sounded as good as my 5500-6000 crossover, so I went back to that at the end.
Hi Saurav,
May I ask what you are planning on using on the lower end to match the PR170m0. What high pass frequency are you going to use on the PR170m0? 250,500Hz.
It seems that in order to find a bass/midbass driver that will match the sensitivity you will not find a driver that will go very low, maybe 50 Hz vented. If you are planning going active then you have more choices as far as sensitivity goes but then a driver that goes into the 30's might not sound to well into the midrange of the PR170m0.
I have a pair of these midranges and these are the choices I'm finding. Listening to these by themselves full range makes me believe that they will make a great pair of speakers
BDP
May I ask what you are planning on using on the lower end to match the PR170m0. What high pass frequency are you going to use on the PR170m0? 250,500Hz.
It seems that in order to find a bass/midbass driver that will match the sensitivity you will not find a driver that will go very low, maybe 50 Hz vented. If you are planning going active then you have more choices as far as sensitivity goes but then a driver that goes into the 30's might not sound to well into the midrange of the PR170m0.
I have a pair of these midranges and these are the choices I'm finding. Listening to these by themselves full range makes me believe that they will make a great pair of speakers
BDP
My last speakers were Eminence Beta 12CXs in sealed cabinets with a coaxially mounted compression tweeter. These 12CXs are "full-range" drivers, which I'm using as woofers. Active XO at 500Hz for now, based on advice here about power distribution in music in different frequency bands. The 12CX will be crossed over (again active) at around 80Hz to an NHT 1259 in a sealed cabinet that'll be the subwoofer.
Here's roughly what it looks like right now:
The cardboard baffle's been replaced by a 1/2" chipboard baffle. The tweeter is a Fostex FT17H, and the mid-tweeter XO is passive.
While I'm posting pictures... the system:
The active crossover:
The 2A3 SET driving the mid and tweeter:
And the Gainclone driving the woofer:
This is all from about 2 weeks ago, so things are a lot cleaner now, both in the room and in the electronics
Here's roughly what it looks like right now:
An externally hosted image should be here but it was not working when we last tested it.
The cardboard baffle's been replaced by a 1/2" chipboard baffle. The tweeter is a Fostex FT17H, and the mid-tweeter XO is passive.
While I'm posting pictures... the system:
An externally hosted image should be here but it was not working when we last tested it.
The active crossover:
An externally hosted image should be here but it was not working when we last tested it.
The 2A3 SET driving the mid and tweeter:
An externally hosted image should be here but it was not working when we last tested it.
And the Gainclone driving the woofer:
An externally hosted image should be here but it was not working when we last tested it.
This is all from about 2 weeks ago, so things are a lot cleaner now, both in the room and in the electronics
Which would mean getting a new tweeter or midrange, since my current tweeter can't be crossed much lower than 5kHz. That's a long-term "plan B", if this combination of drivers doesn't work out. I know that these aren't particularly well matched drivers, I should have done some more research before buying them. But, so far it's sounding pretty good, and the midrange has a reputation for sounding good when crossed over relatively high. Thanks for the advice though, I hadn't realized that the blip at 1.5kHz was the start of the cone breakup.
There's no point in using a really high crossover frequency (like 6kHz) to "keep it out of the critical vocal range" if it means that a woofer will be used in that range instead of a tweeter. You may need a new tweeter that can go a bit lower without maxing out. {Edit: I hate when I have to change something cos I missed the last couple of posts before sending...}
It would help to make full use of the actual measurements. Even if nobody said that it was a paper coned woofer, I could probably still tell that it is just from its waterfall plot. The first big breakup mode is at around ~1.5kHz, visible on both the waterfall plot and the glitch in the impedance. It's relatively benign because judging by the wf plot it doesn't have such a high Q factor. But I'd definitely try to filter out as much as possible above 3kHz - those ripples might look pretty harmless on the frequency graph, but just look at all the crap it causes in the waterfall plot.
CM
It would help to make full use of the actual measurements. Even if nobody said that it was a paper coned woofer, I could probably still tell that it is just from its waterfall plot. The first big breakup mode is at around ~1.5kHz, visible on both the waterfall plot and the glitch in the impedance. It's relatively benign because judging by the wf plot it doesn't have such a high Q factor. But I'd definitely try to filter out as much as possible above 3kHz - those ripples might look pretty harmless on the frequency graph, but just look at all the crap it causes in the waterfall plot.
CM
hi
the approach is plot the responce (pro gear) find out the exact break up mode and cause of occurance ,
reinforce (composite) as necessary the - cone s pulp to minimise the break up
if you have to resort to doping it is done by :-
tking quite a few drivers - doping with quite a few componds in - different densities
plotting these
drawing and inferecnce - and then as required , mixing compounds ets to get the desired dope - right for this application
a dope for one speaker - necessarily will not be able to solve poblems in another
- best avoid dope - makes bonding with adheives (with which the entire driver is held togeter ) - difficult
- in fact - cos like loctite does not recommend it - (info given by loctite to diver manufactureres using loctite adhesives)
the trade off of longetivity of a driver and robustness needs to be considered - when doping
suranjan
transducer design engineer
the approach is plot the responce (pro gear) find out the exact break up mode and cause of occurance ,
reinforce (composite) as necessary the - cone s pulp to minimise the break up
if you have to resort to doping it is done by :-
tking quite a few drivers - doping with quite a few componds in - different densities
plotting these
drawing and inferecnce - and then as required , mixing compounds ets to get the desired dope - right for this application
a dope for one speaker - necessarily will not be able to solve poblems in another
- best avoid dope - makes bonding with adheives (with which the entire driver is held togeter ) - difficult
- in fact - cos like loctite does not recommend it - (info given by loctite to diver manufactureres using loctite adhesives)
the trade off of longetivity of a driver and robustness needs to be considered - when doping
suranjan
transducer design engineer
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.