My "FREE" Boston Acoustics A-400's

[pumpkinman]

Last Friday I picked up a pair of Boston Acoustics A-400's. (FREE) I was told that one of the speakers didn't sound right. I hooked them up and one speaker is producing little to no bass out off either of the bass drivers.
I swapped bass drivers and still the same. So I'm assuming the 8'' drivers are OK and that issue is somewhere else.


P-man




Richidoo has been tremendous help in guiding me on things to check so I can get these bad boys playing again. I ordered 4 caps for the bass crossovers (2 caps per Xover) and they should be here next week.

 I took the bass crossover out and unsoldered all it's components. Took the parts to a friend of mine with a Fluke meter so he could test the parts. The 100uf cap tested at 111uf and the 60uf cap tested at 66uf. Still I'm told that the caps still could be the culprits. The actual work is not nearly as diff. as I thought it would be. Still I don't like not fully understanding what I'm doing. 

I've posted in the past how much I hate speakers with the old spring clips. I went to eBay and found an inexpensive drop in replacement termial cups with binding posts. New jumpers made from 12 gauge OFC cable.

[richidoo]

They look happier in your room!

Glad you ordered the caps. I think that will do it. I think they are shorting the signal to ground, causing partial mute, but they have enough resistance to prevent the amp from protecting.

The caps were dead on when they were made, despite the tolerance. The tolerance describes how it will age. New quality caps are pretty close to the nominal value. Increased cap value is sign of age in caps that are usually run far below their rated voltage, 50V in this case. For speakers, loud as hell is a 10V signal. Caps which are often run close to their rated voltage, like PS storage caps, age with falling measured value.

[Response Audio]

Low.frequency section should have an inductor in series with the woofer.  Have you checked these? As long as you have it out, a few bucks for new ones wouldn't hurt. 

[etcarroll]

Yup, they're free alright! 

But I know you're digging 'futzing around' with them.

[richidoo]

From the pics I saw, looks like 3rd order filter.

>-----------coil --------------coil  -------------->
                             |
                             |
                       1R0 resistor
                             |
                     cap        cap (par)
                             |
>-------------------------------------------------->

Coils and resistor check out. Cap values measured high, but no ESR taken.

[S Clark]

I'm sure that you looked at this, but did you check the wiring at the speaker?

[pumpkinman]

I'm sure that you looked at this, but did you check the wiring at the speaker?

Yes I did
Thanks Bill

[pumpkinman]

Replaced the 2 caps in the low end xover. Now they work.
Need to remove the other xover and replace those 2 caps next

Thanks very much Rich for your help.

[richidoo]

Ayyyyyyyy... no prob





Looking forward to your review....