Will replacing Polytone grille affect the sound?

[jeremiahzellers]

I have a Polytone 102 that I’m taking in for routine service. It has that very chunky cubed foam front grille that smells terrible. I wanted to replace it.. but I’m realizing it’s very thick and may be contributing to the overall mellow tone of the amp.

Am I over thinking this? Anyone do this and notice a tonal change? Ordinarily I wouldn’t even think twice on an amp with a normal grille, but this one is very thick so it’s giving me pause.

[Sigmund451]

Im not sure of the answer but looking at that I cannot imagine that it acoustically invisible. Id be concerned also. It look like its intentionally absorbent. That is probably why it also absorbed odors....that or it sucks out the stinky tones

[AllanAllen]

Sure, it'll scientifically change it in some way, but can anyone truly tell? I'm doubtful. If it smells bad, it's got to go.

Audiophiles Can't Differentiate Audio Signals Sent Through Copper, Banana, and Mud in Blind Test | Headphonesty


If it smells bad, it's got to go.

[sgosnell]

There's only one way to find out. That foam is old and likely has changed in changed in texture over the years. Removing it might destroy it, but I can't tell from here. I doubt the difference in sound can be detected by others, but it's your amp, and you're the judge of the sound, and the decision to proceed or not is yours. I would get rid of the foam, but I'm not you.

[wintermoon]

That stuff is very light and porous. Many people w old Polytones are looking for that kind of replacement foam since it disintegrates into powder over time.

[Alter]

I am sure the foam plays a part. My Aer foam disintegrated and i had it without it for a while, then i noticed a subtle noise coming through the amp. Had it checked and it turned out to be the air that was coming in/out through the bass port. I ordered new foam from the Aer people and sure enough the noise went away. Probably a bit more treble coming through without the foam, but nothing a pot twist can't handle.

[Bob_Ross]

Sure, it'll scientifically change it in some way, but can anyone truly tell? I'm doubtful.

^^^This. Came in to post "Appreciably? No. Measurably? Yes."

fwiw I changed the grill on my Polytone MiniBrute III ~30 years ago, and the amp lost none of its "overall mellow tone"

[AllanAllen]

Cats on Amps

[Mick-7]

Cats on Amps

Sure, it'll scientifically change it in some way, but can anyone truly tell?

I can confirm that cats can tell - and in fact will if given the chance.

[jeremiahzellers]

Thanks for the responses. From what it seems:

yes, the foam most likely does something with the sound

No, it’s probably measurable but not noticeable and most likely just a small adjustment if the treble knob.

yes, I am over thinking this.

I feel like this amp has seen several gross smoke filled venues since the late 70s. The smell hits you in the face when you walk in the room with it.

in fact, I would surprised if it wasn’t cigarette tar that was holding this grille together at this point.

Will replace it.

[Alter]

I'd be more concerned about dust getting places it shouldn't be without the foam rather than the sound effect..

[jeremiahzellers]

I'd be more concerned about dust getting places it shouldn't be without the foam rather than the sound effect..

Agree. I do see some thicker foam like grilles that are available that might be close to what is there already.

otherwise just a Mojotone brand replacement unless others here have grille manufacturers/suppliers they recommend?

[wintermoon]

I wouldn't be so quick to replace the grill, that might not remove the smell.
I'd start by temporarily removing the grill and putting it in a seperate room and cleaning the entire exterior of the amp and see if the smell is reduced.
Also leave the grill/amp in direct sunlight for a week or two, the UV rays might kill the smell.

[Dave70]

I'd try using a shop vac with a brush attatchment on that thing too.

[skiboyny]

I have a 102 and years ago, I replaced the foam grill with some 1/4 finished plywood covered with grill cloth. I used some velcro tape pads to hold it in place so it's removable. I didn't notice a difference in sound.

[Herbie]

I have a 102 and years ago, I replaced the foam grill with some 1/4 finished plywood covered with grill cloth. I used some velcro tape pads to hold it in place so it's removable. I didn't notice a difference in sound.

So did I too. No difference. Maybe better definition if something.

[sgosnell]

I suspect the main reason Polytone used the foam was that it was the cheapest cover available. Cheap to buy and prepare, quick and easy to install.

[vintagelove]

I am 100% positive I could hear the difference in a blind test.

I'm about 70% positive it would be an improvement. Slight, yes... but a little extra air wouldn't hurt.

[Alter]

When i did the Aer foam replacement, the company sent me very detailed instructions on what glue to use, suggested tools, what and where, etc, to keep things factory standard. I had a friend who is very handy with such work do it. So take some time to research how to replace the foam if you do it.

[jeremiahzellers]

When i did the Aer foam replacement, the company sent me very detailed instructions on what glue to use, suggested tools, what and where, etc, to keep things factory standard. I had a friend who is very handy with such work do it. So take some time to research how to replace the foam if you do it.

yeah… I am not at all handy.. at the mercy of trades people to do this. I’m in north Texas (DFW area).. will have to find someone that performs this type of work and see what they think as well.

[Bob_Ross]

I am 100% positive I could hear the difference in a blind test.

Thread Drift: As someone who's spent decades studying psychoacoustics, placebo effects, confirmation bias, and properly controlled double-blind ABX listening tests as a methodology for identifying audio components, I always recoil a bit when I see people make uber-confident claims such as yours. This has nothing to do with how good your hearing is, and everything to do with how fallible human auditory memory is. (It also has a lot to do with people misunderstanding how a "blind test" really works.)

I am 100% positive you couldn't reliably -- meaning, better than chance guessing -- identify which was the original foam grill, and which was the replacement fabric grill, in a true blind test.

But if the confidence percentage in your claim moved down towards 50%, so would mine.

[vintagelove]

Thread Drift: As someone who's spent decades studying psychoacoustics, placebo effects, confirmation bias, and properly controlled double-blind ABX listening tests as a methodology for identifying audio components, I always recoil a bit when I see people make uber-confident claims such as yours. This has nothing to do with how good your hearing is, and everything to do with how fallible human auditory memory is. (It also has a lot to do with people misunderstanding how a "blind test" really works.)

I am 100% positive you couldn't reliably -- meaning, better than chance guessing -- identify which was the original foam grill, and which was the replacement fabric grill, in a true blind test.

But if the confidence percentage in your claim moved down towards 50%, so would mine.

Well, as someone who's spent decades critically listening, I can say it with actual confidence. Here is me reliably hearing a 1ms timing difference (and a link to the test where you can try yourself, and yes I have perfect scores for all the ms listening tests, it's not luck). That's a MUCH harder task than hearing the effect of an inch of foam in front of a speaker. FWIW, I've been doing recording work for almost 30 years, so I'm pretty confident in what I can and can't do. Still aggravated that I failed the 2c pitch listening test...


Blind testing a 1 ms Timing Difference (2-way)




Edit: Ah, I read the end of your post again, you said between the foam and the fabric. I was thinking between the foam and no foam, or one of the "speaker protectors" you see on a bunch of poly's. It would definitely depend on the fabric material. And if the OP cares, you could probably find a thick material that would indeed be close enough to the foam to not matter. But... I would still replace it with the most acoustically transparent stuff you can get, as poly's benefit from a little extra air.

[Gustavo Eiriz]

Well this foam is very thin, probably it dampens only very high frequencies. And Polytone surely doesnt go far more than 4k or 5k... removing completely the foam could increase the brightness if this foam dampens a little. Low frequencies are not affected at all by such a thing.