Polydome replacement

[markuus3889]

We'll see, but I think they are what they are. 5 pairs have been sold on ebay so some other owners input would be good. I don't want to be the only judge. My polydomes are in reasonable shape and they do most things better in my opinion than the new ones.

The new ones aren't horrible and some nuance may come through better but complex passages become fatiguing at higher volume and I don't get that with the polydomes.

Mark K.

 

[okeeteekid]

We'll see, but I think they are what they are. 5 pairs have been sold on ebay so some other owners input would be good. I don't want to be the only judge. My polydomes are in reasonable shape and they do most things better in my opinion than the new ones.

The new ones aren't horrible and some nuance may come through better but complex passages become fatiguing at higher volume and I don't get that with the polydomes.

Mark K.

I think the original polydomes material absorbs up the fatiguing sound you are hearing in the new polydome, wonder if the coil on the new one is so different contributing to it's harsh sound.

 

[markuus3889]

I think the original polydomes material absorbs up the fatiguing sound

I agree!

I measured resistance and it is what is claimed so I'm not sure it alone is a problem. Voice coils are not exactly the same dimensions, they are close, but not interchangeable from new mag to polydome mag. The fabric dome is very thin and pliable. Maybe some doping, but then how long does that last and is the weight then uniform. Trying to tune the driver seems like a waste of time. I'm back to waiting/hoping someone will just repro the f%^king diaphragms.

Is there acoustic measurements of the Polydomes anywhere so we may compare?

Mark K.

 

[okeeteekid]

I agree!

I measured resistance and it is what is claimed so I'm not sure it alone is a problem. Voice coils are not exactly the same dimensions and are not interchangeable from new mag to polydome mag. The fabric dome is very thin and pliable. Maybe some doping, but then how long does that last and is the weight then uniform. Trying to tune the driver seems like a waste of time. I'm back to waiting/hoping someone will just repro the f%^king diaphragms.

Is there acoustic measurements of the Polydomes anywhere so we may compare?

Mark K.

Take a look at this, it tells you the polydome uses flat wire, I doubt the new one does
https://1drv.ms/i/s!AhHWCBRVD6phgwWF6NXpIZdgYGWx

Does the new one have a ceramic magnet besides the glued on neo mag? if so I wonder how it would sound if the neo mag was removed? I just think you are hearing the sound of the clothe material, don't know why they didn't make them the same.

 

[markuus3889]

The wire is edge wound. Not sure about the magnet I'd have to disassemble again.

 

[okeeteekid]

The wire is edge wound. Not sure about the magnet I'd have to disassemble again.

At least they got that right.
I looked at your pics and it looks like there is a ceramic magnet.

 

[okeeteekid]

Spoke with midwest speaker through email and told him about what a forum member who tested the driver thought about the sound of it and here is what he said.

New message from: midwestspeaker (16,542)
Agreed, they are a little brighter then the original. The manufacture that made these could not find any replacement domes that would work except the fabric, they said the "poly dome" material is not available anymore. It is possible to use a resistor on the midrange to tame down the brightness if needed.
Thanks for the info!

How could they not the original material.

 

[markuus3889]

Polypropylene in some form is quite literally all over the earth, from pole to pole.

The magnet looks ceramic in there but I'm not bold enough to disassemble.

 

[okeeteekid]

Polypropylene in some form is quite literally all over the earth, from pole to pole.

The magnet looks ceramic in there but I'm not bold enough to disassemble.

It looks ceramic to me, I wouldn't take it apart.

 

[markuus3889]

I would think any plastic material from 30yrs ago could be reproduced and even bettered. Why it isn't is beyond my comprehension. Maybe the manufacturer was not into plastic manufacturing and had lots of fabric to use up and fed Midwest a line. I really don't know.

I'm not sure a resistor is going to help. I think it is physical.

Mark K.

 

[markuus3889]

Someone else who has them should chime in. 1 reviewer is not enough.

Mark K.

 

[okeeteekid]

I would think any plastic material from 30yrs ago could be reproduced and even bettered. Why it isn't is beyond my comprehension. Maybe the manufacturer was not into plastic manufacturing and had lots of fabric to use up and fed Midwest a line. I really don't know.

I'm not sure a resistor is going to help. I think it is physical.

Mark K.

Lol.
I don't think a resistor will work either, I think that's how the material just sounds, it could be modded if someone gets brave and changes the dome out for a different material, the clothe surround is good on it.

 

[markuus3889]

the clothe surround is good on it.

It seems to me the surround is also quite important here, and maybe the slightly stiffer(not the best descriptor) poly helps. The roll looks a little deeper on the poly too.

Or the 3 inch Polydome is MAGIC! I'm not above this belief anymore.

Mark K.

 

[okeeteekid]

My RSDS uses an accordion edge surround,it feels slightly stiffer than the polydome edge but then again it was not used since it was made so it probably will loosen up after a while.

 

[swechsler]

It's not just that the material is still available; the manufacturer isn't going to want to purchase expensive tooling to work with a different type of material for a relatively small run of drivers.

Wonder if they could be tamed somewhat by putting some sound-absorbent material (felt, maybe?) in front of part of the dome. This technique has been used on tweeters. Doping might work, although chances are you'd need to test on several different units until you got it right. Don't know if anyone has enough spare cash to do that - I certainly don't.

Putting a resistor in series or parallel with dome will affect the crossover frequency; you'd need to do a crossover mod or use an L-pad with a higher range of adjustment.

 

[Bahamayellow]

Thanks every

Some pics:

Thanks for sharing and doing the comparisons. By the way your polydomes look amazing.

 

[markuus3889]

You're welcome. I've been treating my polydomes every so often with pure silicone oil for rc vehicle shock absorbers. Seems to be prolonging their lives ok so far.

Mark K.

 

[sagebug]

I agree with the above impression. They look and sound awfully close to the vifa's. Thinner material than VIFA.
Millers sound better IMHO.
Don't sell those OG Polydomes!!

 

[slimpikkins]

Doesn't Millersound add mass to the back of their replacement dome?

 

[7.62]

I haven’t had much to say because I don’t own any with polydomes anymore, my oldest son has my 8’s. I was seriously about to throw a pair of originals in the trash. I think now I’m going to send them to Bill for a rebuild and just stash them away.