• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Poor ReFoam? Boston Acoustics A150

P

pd360

New Member
I have just purchased some A150's series 3 and the refoam job seems poorly done, with bits of old foam sticking out. It just indicates to me that the job was done rather sloppily and I am wondering if I should go ahead and refoam them again with more care? Thoughts?
 

Attachments

  • IMG_3024.jpeg
    IMG_3024.jpeg
    87.4 KB · Views: 91
Register to hide this ad
Thank you for the welcome, I am a longtime reader and have learned a lot from this forum.

Ok new mystery. I pulled everything apart to give the speakers a good cleaning and I suspect that one of the woofers is not original. When I first pulled it out it looked suspiciously clean. And sure enough the other one looks older and has "Boston" stamped into it. The "newer" one looks almost identical. I have since put that one back together so I don't have them side by side. I certainly don't want a pair of mismatched drivers.
 
Honestly speakers are sort of a generic thing. As long as the magnets are the same weight and the voice coils are the same gauge of wire, and the paper cones are ... well ... paper, there's not much that will differ between an original speaker and the replacement. There is a store in Wisconsin that builds reproduction speakers for BA70's and other BA models, you might have one of their reproductions.
 
Don Gillies said:
Honestly speakers are sort of a generic thing. As long as the magnets are the same weight and the voice coils are the same gauge of wire, and the paper cones are ... well ... paper, there's not much that will differ between an original speaker and the replacement. There is a store in Wisconsin that builds reproduction speakers for BA70's and other BA models, you might have one of their reproductions.
Click to expand...
This is categorically wrong. Building speakers is alchemy, and the tiniest change in materials including the thickness/width of individual parts can make vast changes to the sound.
 
Kenny Green said:
Hi
"Honestly", speaker (drivers) are NOT a "sort of" generic thing and that is really a careless thing to say
I generally do not like to cite "wikipedia" but in this case the article is factually accurate
You're a smart guy, give it a look
https://en.wikipedia.org/wiki/Thiele/Small_parameters
Kenny
Click to expand...
Apologies - It was poorly stated. What I meant to say is that I believe you can clone a woofer driver rather easily. It's not like a VLSI chip where the doping compounds and concentrations are difficult to measure in the 18-35 different layers of the silicon on a VLSI substrate.

If you copy the physical parameters of the woofer accurately (magnet dimensions, strength, wire turns, gauge, and resistance, cone dimensions, mass, basket dimensions and mass, rubber dimensions and mass, and use a basket with generally similar attachment points and clearances), I believe that the sound characteristics are likely to be identical.

The real magic is in selecting drivers and a suspension enclosure and crossovers that are all tuned together to produce a flat (or colored, for some companies like Cerwin Vega) frequency response over a desired frequency and power range.
 
Last edited:
Don Gillies said:
Apologies - It was poorly stated. What I meant to say is that I believe you can clone a woofer driver rather easily. It's not like a VLSI chip where the doping compounds and concentrations are difficult to measure in the 18-35 different layers of the silicon on a VLSI substrate.

If you copy the physical parameters of the woofer accurately (magnet dimensions, strength, wire turns, gauge, and resistance, cone dimensions, mass, basket dimensions and mass, rubber dimensions and mass, and use a basket with generally similar attachment points), I believe that the sound characteristics are likely to be identical.

The real magic is in selecting drivers and a suspension enclosure and crossovers that are all tuned together to produce a flat (or colored, for some companies like Cerwin Vega) frequency response over a desired frequency and power range.
Click to expand...

It is possible to "clone" a speaker to be somewhat close to another, but it is not easy. Every speaker is different, and in order to properly copy them, you need at least a dozen of the same speakers to analyze before you can properly match the sound characteristics. Hi-Fi speakers are easier than say guitar speakers, but that isn't really the point. Just because you use similar components in size and mass, doesn't mean the outcome will be the same. What you end up with is like a bad Xerox copy of the original speaker. It's kind of like the other one, but not really.

Jenson speakers spent millions of dollars trying to clone their old guitar speakers when they got back into that game. They hadn't kept any of the paper files on how the originals were done, and had to reverse engineer them from scratch.
 
Kenny Green said:
Hi
How do you do that? Not have them "side by side" that is?
Is it foam or just trash from the gasket where they had difficulty removing it?
The glue job on the cone looks decent, best as I can tell from a picture
Is your other woofer a smooth cone or does it have ribs (earlier version)
The one in your picture looks like a series III version
Don't know if there's a sound difference or not
Kenny
Click to expand...

Yes, series III. Not having them side by side I meant that they look the same from the front, and I had already reassembled them. Anyway, I popped them both out again and took some pictures. It should be obvious which one is the "newer" one. It as some printing on the cone that I googled and I didn't get any hits. Older one has a dated sticker on it 10/7/88.

IMG_3026.jpeg IMG_3027.jpeg
 
The later replacement woofers from BA were poly cones, not sure what you have but they were visually different than the originals.
 
@Don Gillies they jumped on ya hard for your transgression, tho somehow I knew what you were attempting to say.

With that said, can the OP hear a difference??

Let's all remain civil.

Edit - While I would never be able to rest until both woofers were identical, I didn't see the need to be obtuse and not see the truth in Don Gillies statement. He did say that if woofer size, vc size, and materials were the same, then....

Apparently, my comments set some purists on edge. That was not my intention.
All audio, no attitude, and that includes moi.
 
Last edited:
onwardjames said:
@Don Gillies they jumped on ya hard for your transgression, tho somehow I knew what you were attempting to say.

With that said, can the OP hear a difference??
Click to expand...

No, I cannot hear a difference, and yes ultimately how they sound is whats most important (they sound great!). I am running them off a Nakamichi SR-2A and the sound/value ratio of this setup is fantastic.

Honestly I think its fun to try to figure this stuff out, trace the history, what happened etc.. For instance here is another mystery, the mid has a plastic baffle. On one speaker there is a machine screw attaching the baffle to the driver, the other one has no screw, and there isn't even a hole there, so its not like the screw went missing at some point. They are both series III, but now I suspect they might not be an original pair. Like I said I just find it interesting. Part of the fun of this vintage stuff is its history for sure.
 
pd360 said:
No, I cannot hear a difference, and yes ultimately how they sound is whats most important (they sound great!). I am running them off a Nakamichi SR-2A and the sound/value ratio of this setup is fantastic.

Honestly I think its fun to try to figure this stuff out, trace the history, what happened etc.. For instance here is another mystery, the mid has a plastic baffle. On one speaker there is a machine screw attaching the baffle to the driver, the other one has no screw, and there isn't even a hole there, so its not like the screw went missing at some point. They are both series III, but now I suspect they might not be an original pair. Like I said I just find it interesting. Part of the fun of this vintage stuff is its history for sure.
Click to expand...

Sounds like you're having fun, enjoying what is a hobby. I was wrong to get involved in the back and forth, my apologies.
When someone is new to this forum, sometimes we older members tend to be a bit overprotective, wanting the new members to see what a great place it is.
The people posting to you meant the best, and that's what mattered.

Enjoy your speakers, they're truly a great set. I didn't need mine, only reason I sold them.
 
You must log in or register to reply here.
Back
Top Bottom