Do I have a problem with replaced dustcaps and foam surrounds?

[Kuja]

Hello Everybody!

I have restored a cosmetically beaten up pair of AR-90 loudspeakers.

Woofers and lower midrange drivers needed refoaming.

8" lower midrange drivers had smashed in dustcaps:

They were kinda ugly, so I replaced them with new ones.

Original dustcaps were porous and made from textile, so I replaced them with the same type.

New dustcaps are larger and maybe are more porous since they have larger openings in the fabric.

Here they are:

Now, after reading some articles on the Internet,

I started worrying that I might have degraded performance of these drivers...

New dustcaps are a little bit larger (and I guess that they are couple of grams heavier too?) and are potentially more porous due to larger holes in the material.

Here are the old and the new dustcaps compared:

Also, the new foam surrounds seem to be made of little bit thicker and stiffer foam.

I couldn't find a closer match in my country.

I have two questions:

1:

I have a new dustcap that is larger (maybe a bit heavier too?) than the original

and has larger holes in its porous material.

Textile porous material of the new dustcaps also seems to be a little bit thicker and rougher.

Is it going to significantly / audibly change the sound of a paper 8" lower midrange driver,

operating in the 200Hz - 1.2kHz range?

If the answer is yes, how exactly?

Am I going to have some new dips or peaks in the frequency response? Where and how big?

2:

What can be the influence of a slightly thicker and stiffer foam surround replacement

in the case of this paper 8" lower midrange driver?

No need for the library searching, here are some more details regarding the crossovers:

Thanks in advance!

.

[Carlspeak]

Nice work on the refoam job Kuja.

1. The change in the dust cap will be imperceptible. The more open screen will vent and cool the voice coil even better. Also being larger in size won't matter much because of its more porous structure. It shouldn't affect the response profile significantly.

2. The stiffer foam will reduce your low end bass response somewhat. The extent is dependent on how much stiffer it is compared to original. In any case, your ears will be the judge of both changes.

[Kuja]

Carl,

Thanks for the fast response!

2. The stiffer foam will reduce your low end bass response somewhat. The extent is dependent on how much stiffer it is compared to original. In any case, your ears will be the judge of both changes.

What is the borderline low frequency, at which different foam materials will start to have influence?

Is lower midrange driver operating in 200Hz - 1.2kHz range safe?

.

[Carlspeak]

My comment referred to regular woofers that operate down well below 100hz.

Regarding the freq. range you sited it shouldn't be noticed.

Have you noticed anything?

[Kuja]

Have you noticed anything?

It seems that hey are playing fine.

I can't compare them to anything, since I have listened to new pair some 30 years ago.

I will do some measurements with a Behringer ECM-8000 measuring microphone and I will post them here on the forum.

[Carlspeak]

Oh, so you can do measurements. You didn't mentioned that earlier. Do near field on the woofer/mid about 1/2 CM from the dust cap.

If you think they are playing fine, then they most likely are. Your ears are the best test instrument of all.

[Kuja]

Oh, so you can do measurements. You didn't mentioned that earlier. Do near field on the woofer/mid about 1/2 CM from the dust cap.

If you think they are playing fine, then they most likely are. Your ears are the best test instrument of all.

Ok. I will do that.

Thanks a lot for the tip! I didn't know about the practice of measuring drivers from 0,5cm distance.

My room is far from perfect and speaker placement is even worse, so I have some serious dip at around 200Hz.