Refoaming and Sound Quality

N

NearysEpiphany

New Member
I have a pair of AR-14s which have been in my family for 28 years. I am intimately familiar with how they sound. Very warm, low bass tones and smooth highs. An all around pleasant speaker to listen to.

In the last few years the foam surrounds started to break down, but the speakers still sounded fine. Very recently the surrounds were so disintegrated that the woofer started making a vibrating noise so I finally decided to take them to a local shop to have the surrounds re-foamed.

Well, I get them back from the shop and the woofers look fine. Problem is they sound terrible. No vibrating or distortion, but just very poor bass. What bass there is is ill-defined and "sludgy" sounding.

Has anyone had a similar experience? Is there a break-in period for the new surrounds or are my expectations just too high? Is it a given that refoaming will alter the sound, possibly for the worst?
 
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There are a myriad of possibilities. A refoamed speaker should sound just like it did right before it was refoamed. It's possible that (a) one of the woofers was hooked up out of phase in the crossover when it was put back together, (b) your memory of what they sounded like isn't really what they did sound like, or (c) a crappy refoaming job was performed. Also, if it's been any length of time, it may be time to do a recapping of the crossover.
 
Scorpion8 said:
There are a myriad of possibilities. A refoamed speaker should sound just like it did right before it was refoamed. It's possible that (a) one of the woofers was hooked up out of phase in the crossover when it was put back together, (b) your memory of what they sounded like isn't really what they did sound like, or (c) a crappy refoaming job was performed. Also, if it's been any length of time, it may be time to do a recapping of the crossover.
Click to expand...

I'm thinking (a) & (c) are possibilities. It looks like the refoaming job is ok so I'm leaning more towards (a).

How do I check to see if they were hooked up in-phase? I know the woofers each have two wires connected to them, one red and one black.
 
IIRC the new foams need time to become pliable. At least that's been my experience with the woofers I've refoamed. After 50 to 100 hours of playing the speakers sounded significantly better.
 
Is the new surround material similar to the older material? Is it glued to the same side of the cone as previous? Is there a possibility of an air leak around the mounting ring? Are the dust caps the same size? Those are the first things that come to mind.
It's possible that the woofers need some time to break in, as well. The woofers may have been mounted in a different position and the spiders might need a little play to reorient. If the difference is drastic there was something amiss in the surround installation.
 
You can un-mount the woofers and lift up, and just check that the red and black are on the same terminals on both woofers.
 
I just re-foamed some bose 601s.

They sound great :banana:

Now that being said, I never heard them before I re-foamed them, so if the sounds gets better. :banana::banana:

But, I find it unlikely that the new foam has much to do with the sound quality. The spider in the woofer has more resistance then the foam, so that is really what gets "Broken in" not the foam

I could be wrong.

Chances are, you;re out of phase, which is a good thing if that is the case. Means you can fix it your self.

If it comes down to a break in period, then that means my 601s are going to sound even better which means :banana::banana::banana:
 
How do I check to see if they were hooked up in-phase? I know the woofers each have two wires connected to them, one red and one black.
Click to expand...

Save yourself the trouble of pulling them apart and just switch from stereo to mono. (If you have that option) If the bass comes back in mono the speakers are out of phase.

Steve
 
Consider that the last times you were listening to them the woofers weren't performing to spec. They were likely lacking mechanical resistance which would change many of the woofer's parameters so that they were no longer "optimized" for that particular speaker system.

EDIT: Also consider that when the foam has deteriorated to the point that it's no longer airtight, the box tuning is also being affected, meaning at that point the speakers sounded quite different than they did 28 years ago.

Now with new surrounds installed, you've gone from one extreme to the other. The new foams probably offer more mechanical resistance than what was originally spec'd for the woofers, things should settle down with some play time.

When i re-foam, i usually run the woofer for a few hours with a few watts at 30-40 hz, and then test the woofer to see that it's Fs is within a few hz of spec.................. if the specs are known. I've had cases where a significant change takes place, as well as cases where there's little change at all.

Just my .02 y'all understand................................
 
Sounds as if the shop MAY have used a too-stiff foam surround.

Contrary to intuition, a stiff surround will NOT give "tight" bass in most cases. A stiffer surround will raise the Fs, and more importantly, RAISE THE QTS- the "resonant Q factor" of the speaker.

What this results in, in most cases, is a speaker that, instead of having a linear, smooth response down to a low frequency rolloff point, will have the bass "bunched up" in the midbass, leading to a boomy, muddy sound, with little definition and not much extension, compared to a correct softer surround on the same speaker.

Some surrounds will "soften up" somewhat after installation... one way to accelerate that process, is to play a low frequency test tone (30 Hz or so) at moderate amplitude (say, between 3/16" and 1/4" excursion), for a few hours. Once you do this, you can be pretty much sure, you're listening to the speaker in a broken-in a condition as it'll EVER achieve...

Regards,
Gordon.
 
All very good advice from the above posts... :yes:

On the possibility that the woofers are out of phase - you could
just reverse the wires at one speaker and see if the bass comes
back.

I'm leaning to the fact that the surrounds need to break in a little.

As they were deteriorating, they did it slow and over a long period
of time, so your ears never really heard a change in the sound.

Now, they have changed to the extreme and your ears notice the
difference.

Scott
 
This is somewhat illogical

Firby13 said:
Save yourself the trouble of pulling them apart and just switch from stereo to mono. (If you have that option) If the bass comes back in mono the speakers are out of phase.

Steve
Click to expand...

If the speakers are out of phase, then putting them into mono mode will have one pushing while the other is pulling - the classic physics wave mode which produces a null and much LESS bass.
 
Firby13 said:
Save yourself the trouble of pulling them apart and just switch from stereo to mono. (If you have that option) If the bass comes back in mono the speakers are out of phase.
Click to expand...
Well, that'd be wrong. The phase is the same, stereo or mono.

bowtie427ss said:
When i re-foam, i usually run the woofer for a few hours with a few watts at 30-40 hz, and then test the woofer to see that it's Fs is within a few hz of spec.................. if the specs are known. I've had cases where a significant change takes place, as well as cases where there's little change at all.
Click to expand...
Yup.

Measure, measure, MEASURE!
 
Thanks for the replies gentlemen. I've checked them and I am pretty sure they are not hooked up out-of-phase.

GordonW said:
Sounds as if the shop MAY have used a too-stiff foam surround.

Contrary to intuition, a stiff surround will NOT give "tight" bass in most cases. A stiffer surround will raise the Fs, and more importantly, RAISE THE QTS- the "resonant Q factor" of the speaker.

What this results in, in most cases, is a speaker that, instead of having a linear, smooth response down to a low frequency rolloff point, will have the bass "bunched up" in the midbass, leading to a boomy, muddy sound, with little definition and not much extension, compared to a correct softer surround on the same speaker.
Click to expand...

I think this is right-on. The foam surrounds seem awfully stiff...and I am definately experiencing "bunched up"/muddy/ill-defined mid-bass with just about zero low-bass response. I dunno if these guys are gonna break in enough to give me the sound I like.

As a result, I have ordered a new pair of woofers on ebay from vintage-AR:
http://cgi.ebay.com/ACOUSTIC-RESEAR...ryZ14991QQrdZ1QQssPageNameZWD1VQQcmdZViewItem

Hopefully these will get me back to where I want to be.
 
Please tell us how the new woofers sound. . .

I have refoamed hundreds (or so) of woofers all of them kinda tight sounding at first. My SQ always came back in short order but on occasion some took longer.

I have put newly refoamed speakers face to face thrown a big beach towel over them, put the radio on between station hiss and let them play a few days, checking from time to time that 'hiss' was still playing. Before I would use pink noise but I have no source for pink noise now. I have used pink noise in the past to 'break-in' a speaker when speaker 'break-in' was the thing to do. . . Nowdays you don't see it near as much. . . And I haven't done it in years. . .

I used to think it worked. . . I do know that stiff surrounds will loosen up after a time providing the surrounds are not some off spec odd ball that is meant to be different. . .
 
Those who have studied it say "break-in" is complete in 20 seconds or less.

I don't call it over until they've been doing bass for about 8 hours, tho.

[I pretend to hear a difference.... :p: ]
 
Just an observation here, but was breakin an issue when the speakers were new from the mfr.? I don't think so and never read anything about in all the speaker reviews in the mags of the time. So my gess is that as long as the surrounds are near as can be to the origs. in matyerial composition then breakin shouldn't be much of an issue. But I have no experience in this matter nor have ever heard a re-edged speaker, altho I hope to have the pleasuer of doing so this afternoon with a JBL LE15A. I'll be getting a refoamed one to evaluate with one of my origs. Here's hoping all goes well so I can have mine done by re-edger. I'm looking for an improvement.
 
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