Specs for Boston Ac A40 driver?

[Jim H B]

Hi,

I was curious if anyone out there knew where I could find the frequency response of the 6.5 in driver from the Boston Acoustics A40 speaker. Thanks for any help.

 

[GordonW]

I haven't measured one, and AFAIK, Boston hasn't published the parameters of the driver.

However, that being said, I know, from the crossover topology and the tweeter, that the driver HAS to be flat up to AT LEAST 4KHz, probably 5KHz. That mylar-dome tweeter is crossed over at near 5KHz...

BTW: Is it an A40 (paper cone), or an A40-II (poly plastic cone)?

Regards,
Gordon.

 

[Jim H B]

Thanks for the reply. It is the paper A40.

I purchased a pair of Baby Advent (not the Baby II) on Ebay, in "excellent condition" (please don't laugh). It turns out the crossovers and tweeters (both original) are bad.

The original drivers had been replaced with the A40's and they work fine.

The cabinets are in excellent shape. So, I'm looking to purchase crossovers and tweeters to get them working again. I was going to order through Partsexpress. Any suggestions on tweeters or crossover points would be appreciated.

Thanks again!

 

[GordonW]

These tweeters are pretty much identical in function to the original A40 tweeter:

http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=275-065&DID=7

As for crossovers, either of these should be appropriate with that tweeter and woofer:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=260-148

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=260-198

You might also want to add an L-pad to the tweeter; the 15 watt PE unit should be fine:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=260-250

I'd bet you'd have a pretty fair facsimile to an A40, once done. Those drivers are pretty well-behaved; I don't think you're going to run into any real weird issues. You may want to add a Zobel (impedence compensation network) across the woofer; if so, a 10 ohm resistor and an 8 uf (or so, it can vary a bit) capacitor wired in series, with the combo paralleled with the woofer (after the crossover) should probably cover it.

Regards,
Gordon.

 

[Jim H B]

Thanks for the excellent advice, Gordon.

A couple of newbie questions, if I might;

It looks like the original crossovers are mounted right behind the power teminals, so I have to separate them somehow, or get new terminals too.

But how do you hook up the wires from the speakers and the terminals to the crossover. Are they clips, similar to the way the wires clip to the speakers, or do you have to solder the wires to the crossover?

I also don't know if I'll be able to use the old wires (from the crossover to the woofer and tweeter) that are in there now. Would I just make new wires, the appropriate length, myself, with clips on either end? Is so, what type of wire should be used.

Thanks again, Gordon.