Blown B&W CDM1SE bookshelf speaker w/ XPA-5 BiAmped

[quattroll]

Hi Guys,

I have a workshop set up in my garage with a DC-1 and XPA-5. I can run 5 channels out there with my UMC-1, but usually I just use stereo mode. The UMC-1 downmixes everything on its optical out, so that is a good way to keep the DC-1 happy with multiple hdmi sources. I can also use the analog in on the DC-1 to get the L&R 5.1 signals. Just thought I would mention that.

Anyway, I could not resist the temptation to BiAmp with the XLR splitter. Although I was liking the sound, it did not seem like a huge difference. Now I think that I have blown one of the tweeters, so maybe it was not a good idea? The speaker is rated for 200 watts, but I'm not sure what that really means. Perhaps because they were bi-amped I was outside of the normal clipping and therefore didn't notice until it was too late?

So a while back I looked into getting some new tweeters, and they are about $150 each, self installed. Maybe I should go back to single amplification and get them? Now I think that these are ferrofluid style and does that mean that I would be buying something that has sat on a shelf for a decade and the ferro fluid is potentially bad anyway? Also, could my woofers be susceptible to a similar condition?

These are nice speakers so I would be paying much less than a comparable quality speaker I think. Maybe after 15 years it is time to say good bye?

Part of me wants to jump into magnepan MMG, but I am pretty sure that they would not really work in the space with a confined sweet spot. Anyway, if the lounge can help me with these ideas and situation, it would be great. I'm not sure how much longer I can listen to the malfunctioning tweeter.

Incidentally I have the Sonus Faber Toy 5 channel set up and I am wondering if they are ferro fluid too? Has the ferro fluid era passed? just wondering for the sake of their longevity.

Cheers

[moko]

most 2 way bookshelf speakers are bi-wireable NOT bi-ampable. so what you did actually was paralleling 2 amps which result 400 watts @ 8 ohms into a single speaker. this isn't the reason for blown tweeter as long as you play them in normal listening volume. if the overpowering is the reason, you would have blown BOTH your tweeters, right ?

my guess is after 15 years, the ferrofluid in a damaged tweeter has dried. the ferrofluid can increase power handling for tweeter. it means to keep it cool. woofers don't use ferrofluid.

if space is an issue i wouldn't get mmg either. for $150 you can make it working again for another 15 years ?

btw those speakers are rated 120 watts @ 8 ohms.
www.bowers-wilkins.com/Downloads/Product/Archive/ENG_FP10772_CDM1-SE_info_sheet.pdf

[leonski]

Why NOT biampable? Once you remove the jumpers, you have seperated the 2 halves of the crossover, being lowpass to the woofer and high pass to the tweeter. The issue THAN, as I see it is WHERE is the crossover point. For the mythical 'normal' distribution in music, a crossover of maybe 350 or 400 hz is around the 50:50 power point. so a pair of identical amps crossed over near those values will 'bout redline at the same time. If you crossover at 2000hz, than maybe you only need 30%above and 70% below crossover.
There ARE jumpers, right?
Yep, agreed, 15 hard years will 'cook' the ferofluid out of many drivers. Too bad, too. And yes, it is still a current practice.
Speakers don't have watts. That 120 watt number is mythical. Be sensitive to distortion would be the way I'd go. And I've blown up speakers before, too. And learned my lesson! I even ran my early Magnepan MG-1 speakers RIGHT to REDLINE using over 200 a side. And it was LOUD. I would occassionally pop the 1.5 amp tweet fuse. Long term? speakers didn't like it. Back in the 80s I destroyed the Midrange on my speakers.
I'm not sure you CAN parallel 2 amps. I think you CAN wire them in series (SAME AMP ONLY) to double the voltage. Same limits as bridging apply.

And unless you can get 4 feet or better yet 5 feet BEHIND a panel speaker, I'll go with MOKO and recommend against 'em. They gotta have AIR to sound best.

[vcautokid]

Ferro fluid is about dissipating heat. If the tweeter sees DC as a result of clipping, or is run real hard beyond its design. Yep, the tweeter will expire. Tweeters usually don't need allot to be happy. You can still bi amp, but be mindful of how much power that tweeter will see. I sold B & W for years. Cooked tweeters were an often seen thing for me. Everything that is audio does have a limit somewhere.

[siggie]

Jan 29, 2015 15:55:42 GMT -5 quattroll said:

Hi Guys,

So a while back I looked into getting some new tweeters, and they are about $150 each, self installed. Maybe I should go back to single amplification and get them? Now I think that these are ferrofluid style and does that mean that I would be buying something that has sat on a shelf for a decade and the ferro fluid is potentially bad anyway? Also, could my woofers be susceptible to a similar condition?

T

B&W is nice in that they stock parts for old speakers. I could be wrong, but I do not think they are old. If you didn't find the replacement tweeters at B&W's web site, here is a link:

bwgroupsupport.com/parts/price-avail

siggie

[quattroll]

Thanks Siggie, I just sent them an email to double check, currently out of stock on site though.

[leonski]

Perhaps replace the tweeters as a PAIR? After all, BOTH tweeters were subjected to about the same amount of stress. You will than have a used / spare.
It wouldn't do to replace ONE than the other decides to crap out. Also, you might want to reconsider both the amount of amplifier power applied to these speakers as well as your listening levels. The book which specifies 'max power' to the speaker also says UNCLIPPED. Thanks MOKO for the link.
Too much power is probably NOT the problem IF you are listening for signs of distress. Also, as speakers HEAT UP during use, certain parameters change. Pro, or sound-reinforcement speakers can take that kind of abuse for HOURS. Home stuff, not so much.

How much does B&W get for those tweeters?