21 replies to this topic

[JKent]

Next are the large Advents with masonite ring woofer. Anyone know how well the caps hold up in them? The Advents use pink fiberglass insulation for stuffing. Is it necessary to keep the fiberglass out of the woofer? If necessary, then how is that done?
Thanks
Tonedeaf (what)

You may be interested in this thread:
http://www.classicsp...?showtopic=4919

I haven't started the refoam yet, but I think replacing the caps is always a good idea. I used inexpensive Carlis and also replaced the resistors. Pete B recommends replacing the inductors as well, but that can run into a bit of money

Could you weigh the amount of fiberglass in each speaker and post it here? Mine used foam rubber--like a cut up cheap mattress I'd like to replace that with fiberglass.

Good luck.
Kent

[Mazeppa]

Thanks for the schematic, tonedeaf.

I can't help you with the 16mm hole question.

I can tell you from many years of experience as a maintenance electrician that capacitors can test well, but behave differently when passing current in application as I've remedied some vexing problems in older equipment by replacing electrolytic cap.s that tested well for capacitance value. I follow the advice I've seen many times in various forums regarding cap. replacement. If it tests bad, replace it. If cap.s test ok, but you don't think your (older) speakers sound as good as they should. replacement of electrolytic cap.s should be tried. If the new cap.s alter the voicing unacceptably, put the old ones back in. I'm not trying to say there is no value in bench testing cap.s, but it's not always completely definitive.

Woofers in stuffed enclosures usually have some type of barrier between the speaker cone and the stuffing. I copycat the method of cutting pieces of window screen mesh (I recommend the non-conductive type) and glueing them over the openings in the basket as I've seen on several OEM woofers. Another alternative would be to wrap some coarse woven fabric around the basket like I saw in my AR2a's.

Turning back to A-150s about stuffing, mine have a white polyfill similar to the "Acoustistuff" sold by Partsexpress in them, is that what y'all found in yours?

Are Boston Acoustics A-150s worth the trouble to get working right? My answer is not only "Yes", but "H-ll yes!" In my opinion they are among the best in all of vintage speakerdom.

[Mazeppa]

Could you weigh the amount of fiberglass in each speaker and post it here? Mine used foam rubber--like a cut up cheap mattress I'd like to replace that with fiberglass.

Good luck.
Kent[/font][/size]

I've not been in his game for very long, but I've done a lot of reading and never heard of foam blocks for cabinet stuffing.
My A150's have the round SEAS tweeters in them. Do yours have the older round, or newer square tweeters in them?

When I had my woofers out for refoaming it appeared the cab.s were equally full of white polyfill type stuffing. I hope to get back in for a recap soon and will weigh stuffing at that time and post the result.

Turn it up!

[JKent]

Sorry for muddying the waters by going off on an Advent tangent in the Boston section. Yes Mazeppa, Advents did use foam. The Advent 400 (radio) speakers had foam stuffing and my Original Large Advents did as well. PeteB has recommended replacing the foam with fiberglass or poly so I was wondering how much to use. Will continue this discussion in the Advent area though.
Kent

[Mazeppa]

 Boston_A150.bmp   1.37MB   843 downloads

I'm finally getting around to recapping my A150s. Refer to the attached schematic, please. I'm fishing for confirmation that the 6.8uf and the 60uf are bypass cap.s in the mid and woofer circuits respectively.

I plan to use less expensive bipolar electrolytics for bypass cap.s is the reason for my question.

Also, is the attached schematic typical for all A150s or should I open mine up to verify cap. values?

[JKent]

I plan to use less expensive bipolar electrolytics for bypass cap.s is the reason for my question.

Just a suggestion:
Looks like each speaker requires a 60uF, 20uF and 6.8uF and 4.7uF

If you go to Madisound, you can get:

4.7uF Carli Mylar for $1.25
6.8uF Carli mylar for $1.70
20uF Carli for $5.00 OR use two 10.0 mfd Polypropylene “surplus caps” in parallel, at $0.60 ea ($1.20 per speaker)
65uF Bennic NPE for $1.90 OR—if there is room—use 6 of those 10uF surplus caps. $3.60 per speaker. Pretty economical!

Too bad they sold out of the 5uF GE caps—they were a bargain at .75 ea, but the Carlis are bargains, too. CSP member RoyC turned me on to them, and he knows crossovers!

Good luck
Kent

[Mazeppa]

Just a suggestion:
Looks like each speaker requires a 60uF, 20uF and 6.8uF and 4.7uF

If you go to Madisound, you can get:

4.7uF Carli Mylar for $1.25
6.8uF Carli mylar for $1.70
20uF Carli for $5.00 OR use two 10.0 mfd Polypropylene “surplus caps” in parallel, at $0.60 ea ($1.20 per speaker)
65uF Bennic NPE for $1.90 OR—if there is room—use 6 of those 10uF surplus caps. $3.60 per speaker. Pretty economical!

Too bad they sold out of the 5uF GE caps—they were a bargain at .75 ea, but the Carlis are bargains, too. CSP member RoyC turned me on to them, and he knows crossovers!

Good luck
Kent

Thanks for the quick reply and good tip. I'm off to the Madisound wesite.

[Carlspeak]

I'm finally getting around to recapping my A150s. Refer to the attached schematic, please. I'm fishing for confirmation that the 6.8uf and the 60uf are bypass cap.s in the mid and woofer circuits respectively.

I plan to use less expensive bipolar electrolytics for bypass cap.s is the reason for my question.

Also, is the attached schematic typical for all A150s or should I open mine up to verify cap. values?

I believe there are 3 slightly different versions. Open yours up and verify your cap values before you run off and buy anything.
Attached is a schematic I drew of a version III. However, yours may be different.
The link below is a place to start regarding which series you have. Do more searches here and at AK to determine which you have just to nail it down.
http://www.audiokarm...coustics series

Attached Files

•  Boston_Acoustics_A150_series_III_schematic.doc   179K   297 downloads

[Mazeppa]

I believe there are 3 slightly different versions. Open yours up and verify your cap values before you run off and buy anything.
Attached is a schematic I drew of a version III. However, yours may be different.
The link below is a place to start regarding which series you have. Do more searches here and at AK to determine which you have just to nail it down.
http://www.audiokarm...coustics series

Something was telling me I should open them up first, but I got a little bit lazy. Thanks for your timely post and references.

[JKent]

Something was telling me I should open them up first, but I got a little bit lazy. Thanks for your timely post and references.

Sorry--I was not aware there were different versions . You only placed the order today, so maybe you could phone or email Mad and ask them to hold the order until you check.
OTOH maybe you'll get lucky.
Kent

[Mazeppa]

Finally back to A150 recap. Opened them up for look see at the xover and it does seem to be different than the schematic given earlier in the thread.

Bear in mind that I'm a long time electrician with a bare smattering of electronics knowledge. I checked and rechecked my schematic against the xover itself until I was cross eyed. As I'm unfamiliar w/crossover design I'm asking those more knowledgeable to check me as best as can be done with the pic. and not too pretty schematic.

I'm still trying to determine which cap.s are just for bypassing (C3 & C4?) so I can use electrolytics for those and polyesters for all in series signal path positions. Any and all help will be appreciated.




First attempt at anything but text, is this the way to go?

[JKent]

Just a suggestion--you might want to scale down those jpg files.
So there are 4 caps: two 60uF, one 10uF and one 6uF
It's a little crowded in there but you can parallel 3 Carli 20uF caps for the 60s, use a Carli 10uF and a Carli 6uF.
Or... use Solen 60uF (they are $19 each)
Or... use Bennic non-polarized electrolytics. 65uF is under 2 bux
They still have those surplus caps for .60 each, but you'd end up with 13 10uF caps plus the 6uf in each box. It can be done, but may be a bit of a hassle.
btw--after you pry all those components out of the hot-melt glue you might want to replace the resistors too. Eagles from Madisound are just $1.20 each.
good luck
Kent

[Carlspeak]

The use of 12X12X2 inch thick foam block in New Large Advents was very common. Five of them in fact.
I've done some comparison work on two NLA's now using OCFG vs the original foam blocks and each time the FG has performed better a 1 lb/cu.ft. stuffing or-so stuffing density. Lower Fc and smoother impedance & phase response.
See posts #1 and attachment at #12 here http://www.classicsp...r...c=2895&st=0

[Mazeppa]

[/quote]
Just a suggestion--you might want to scale down those jpg files.
[/quote]

I'll have to figure that out. What scale will still provide usable defintion?

[/quote]
[size=4][font="Comic Sans MS"]
So there are 4 caps: two 60uF, one 10uF and one 6uF
It's a little crowded in there but you can parallel 3 Carli 20uF caps for the 60s, use a Carli 10uF and a Carli 6uF.
Or... use Solen 60uF (they are $19 each)
Or... use Bennic non-polarized electrolytics. 65uF is under 2 bux
They still have those surplus caps for .60 each, but you'd end up with 13 10uF caps plus the 6uf in each box. It can be done, but may be a bit of a hassle.
btw--after you pry all those components out of the hot-melt glue you might want to replace the resistors too. Eagles from Madisound are just $1.20 each.
good luck
Kent
[/quote]

Thanks for the suggestions. The difference in price between the 60uf Solens and the 65 uf Bennic NP electrolytic very well illustrates why I was trying to confirm which cap.s are series in signal path (Solens) or parallel (Bennic).

[Mazeppa]

Howard & Carl,

Foam blocks for cabinet stuffing not so rare, eh? No end of things to learn it seems.

I already had a notion to try stuffing my A150s w/fiberglass just to see, hear rather, if there was an improvement over the stock polyfill. Got the idea from a very interesting report on the differences in acoustic performance of various cabinet stuffing materials. Carl, I believe you provided the link in a thread about stuffing vintage ARs. Fiberglass was found to be generally superior over acoustic polyfill and Wal-Mart poly pillow stuffing.

Knowing how I am, my test mule A150s may find themselves stuffed w/foam blocks some of these days.