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Tonyk3283

Audiophyte
i have a set of b&w cdm1s. Pretty sure the crossover is fried. Anyone know of good one to to replace it with.
 
BoredSysAdmin

BoredSysAdmin

Audioholic Slumlord
crossovers don't usually get damaged, you're much more likely damaged one of drivers
 
highfigh

highfigh

Seriously, I have no life.
And when a crossover is damaged, you don't just buy another from a list in a catalog or off the shelf- they're designed for the drivers and configuration used. If you killed drivers or a crossover, you need to operate within the capabilities of the speakers and other equipment, or get equipment that will produce the SPL that you want.
 
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Tonyk3283

Audiophyte
I had a a sales rep for b&w tell me that the crossovers are usually the first thing to go. It's weird I only get sound out of the driver and nothing from the tweeter. The driver sounds a little muzzled sounding.
 
Swerd

Swerd

Audioholic Warlord
I had a a sales rep for b&w tell me that the crossovers are usually the first thing to go. It's weird I only get sound out of the driver and nothing from the tweeter. The driver sounds a little muzzled sounding.
Telling you that the crossovers are the first thing to go, is clearly wrong. From what you describe, I think you have a blown tweeter.

Try doing this: On the back of your speakers are two pairs of wire binding posts:


Turn off your receiver or amp, and disconnect the wires. Remove the brass links between the upper and lower posts. Then reattach the wires, first to the upper set which should drive only the tweeter, and then to the lower set which should drive only the woofer. Do that for both of your speakers. If the tweeter is blown, replace it with a new one specifically for CDM1s. That probably will not be cheap.

It may be just my opinion, but it seems that many people come here with major misinformation they learned from B&W salesmen.
 
highfigh

highfigh

Seriously, I have no life.
I had a a sales rep for b&w tell me that the crossovers are usually the first thing to go. It's weird I only get sound out of the driver and nothing from the tweeter. The driver sounds a little muzzled sounding.
And that's why they're sales reps, instead of service techs- they don't usually know what they're talking about.

Capacitors are rated for voltage and as long as that voltage isn't exceeded, they rarely have a problem. Most speaker crossover caps are rated at 50WVDC (Working Volts, DC) and to reach that, the amp has to put out a lot more power than the equipment owned by most people could ever produce, unless something goes very, very wrong. With an 8 Ohm load, Ohm's Law shows that the voltage will be very close to 28.3VAC and to doubling the voltage requires a much more drastic voltage increase.

Amplifier clipping is the most common cause of tweeter damage. Second is bad crossover design and if you were to look into the number of bad tweeters in that model Worldwide, I bet it's pretty rare under normal operation ('normal' meaning "not clipping". That means it doesn't fall under the title of "bad crossover design".
 
M

markw

Audioholic Overlord
I gotta go along with the others. It's highly unlikely that the crossover died. In my over fifty years in this hobby, I've never seen a crossover blow out.

Speakers, yes, but never a crossover. Which begs the questions: What were they driven with, and how loud were they played? If one tried to force heavy bass from then, then they were courting disaster.
 
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Tonyk3283

Audiophyte
So I hooked up the cables just to the tweeters and the sound is really faint. Can barely hear anything. I tested the drivers and I'm getting 4.5 ohms out of both of them. They are rated at 8ohms so I'm sure that is a problem.
 
M

markw

Audioholic Overlord
That reading isn't abnormal for 8 ohm speakers. 8 ohms is it's (AC) impedance. You measured DC resistance, which is not the same thing. It's possible that overpowering might have fried the voice coils, but not to the point of breaking continuity.

But, anything is possible. If the crossover is bad, that would be a first for me. IF you DO order one from B&W, make sure you can return it id that's not the problem. After all, you're just following their sales reps advice and, hopefully, they stand behind them.
 
highfigh

highfigh

Seriously, I have no life.
I gotta go along with the others. It's highly unlikely that the crossover died. In my over fifty years in this hobby, I've never seen a crossover blow out.

Speakers, yes, but never a crossover. Which begs the questions: What were they driven with, and how loud were they played? If one tried to force heavy bass from then, then they were courting disaster.
You should have been working in audio in the late-'70s when lots of crappy speakers were the norm and people wanted loud from equipment that was only able to do "kinda loud". Omega (Schaak's cheap line, below DLK) used to have one cap for the tweeter and nothing else & this was rated for 25WVDC, so it was common to have little burn-outs stumble in on Monday mornings with a handful of blown drivers, or their cabinet than smelled funny. We saw a lot of toasted drivers and crossovers- all of them were courtesy of dishonest salemen, reviews and ads that made these kids think they actually COULD take 100W, or more.

Low power and cranked volume & tone controls and/or a graphic EQ with no clue about how to properly adjust it is just about a guarantee for killing speakers Another one was the RG processors that were sold by Pioneer- they enhanced dynamics and sometimes, it was more than the speakers could handle.

Almost nothing likes having the volume cranked when the needle drops.

I went to Summerfest last night and one of the bands was Kansas. They started one song with a low synthesizer note and as soon as it started, I could hear the voice coils scraping. My first thought was "Oh, SOMEBODY is gonna be
repairing a lot of speakers this week!"
 
highfigh

highfigh

Seriously, I have no life.
So I hooked up the cables just to the tweeters and the sound is really faint. Can barely hear anything. I tested the drivers and I'm getting 4.5 ohms out of both of them. They are rated at 8ohms so I'm sure that is a problem.
That's low for an 8 Ohm speaker and it's the reason the output is low. In order for the speaker to operate, the current conducted by the voice coil has to create a magnetic field. If the voice coil is intact, it will produce a magnetic field that's based on what the coil's properties dictate. If this coil is damaged and a short circuit occurs, the magnetic field will be weaker and the output will decrease, but only if the short isn't connecting one end of the coil wire to the other- if this happens, no magnetic field will result.
 
M

markw

Audioholic Overlord
You should have been working in audio in the late-'70s when lots of crappy speakers were the norm and people wanted loud from equipment that was only able to do "kinda loud". Omega (Schaak's cheap line, below DLK) used to have one cap for the tweeter and nothing else & this was rated for 25WVDC, so it was common to have little burn-outs stumble in on Monday mornings with a handful of blown drivers, or their cabinet than smelled funny. We saw a lot of toasted drivers and crossovers- all of them were courtesy of dishonest salemen, reviews and ads that made these kids think they actually COULD take 100W, or more.

Low power and cranked volume & tone controls and/or a graphic EQ with no clue about how to properly adjust it is just about a guarantee for killing speakers Another one was the RG processors that were sold by Pioneer- they enhanced dynamics and sometimes, it was more than the speakers could handle.

Almost nothing likes having the volume cranked when the needle drops.
I hears ya. I worked for Tandy/Radio Shack several times between '68 and 2000 but the time I remember most is from '80 - 84 when I was going to computer school.

One of the big sellers was those under-dash auto power boosters with built-in graphic equalizers and two and three way coaxial 6x9 speakers. The boosters were rated for about 20 watts and the speakers were rated for somewhat higher, I think 50 watts..

Like you say, they walked out grinning but, like clockwork, a few days later, they would be in screaming the tweeters blew out. why? They were rated for 50 watts but the booster only puts out 20. They want a new speaker. This was constant.

Invariably, the eq was set in the ubiquitous "smiley face" configuration and they cranked those things to eleven!!! some of the smarter ones learned that when you drive an amp into hard clipping, it can send tremendous HF noise to a tweeter and fry it in a matter of minutes. This was explained to them and some actually learned from this. At one point, we explained this when we sold the stuff but still some would come back.

We would replace one speaker. After that, they were on their own.
 
highfigh

highfigh

Seriously, I have no life.
I hears ya. I worked for Tandy/Radio Shack several times between '68 and 2000 but the time I remember most is from '80 - 84 when I was going to computer school.

One of the big sellers was those under-dash auto power boosters with built-in graphic equalizers and two and three way coaxial 6x9 speakers. The boosters were rated for about 20 watts and the speakers were rated for somewhat higher, I think 50 watts..

Like you say, they walked out grinning but, like clockwork, a few days later, they would be in screaming the tweeters blew out. why? They were rated for 50 watts but the booster only puts out 20. They want a new speaker. This was constant.

Invariably, the eq was set in the ubiquitous "smiley face" configuration and they cranked those things to eleven!!! some of the smarter ones learned that when you drive an amp into hard clipping, it can send tremendous HF noise to a tweeter and fry it in a matter of minutes. This was explained to them and some actually learned from this. At one point, we explained this when we sold the stuff but still some would come back.

We would replace one speaker. After that, they were on their own.
We taught a lot of people about what happens when an amp distorts and some of those kids still own the last equipment they bought almost 30 years ago (I left that store in '88). I had one kid come in with a pair of Jamo J101 speakers that had most of its drivers blown. That model had poly-switches, which were there to protect the mids and tweeters and he still killed them. I explained that blowing more than one driver is considered 'abuse' and that we'd have to charge him for the repairs. His dad showed up, extremely PO'd, telling me that we were dishonest, it was illegal, his kid doesn't crank the stereo that loud and "wait till you hear from my lawyer!". I told him that I had a pair of that model, two of the others who worked there had them, a lot of our friends had them and that we had sold literally hundreds of pairs of that brand without a single one coming in with that much damage. He calmed down amazingly quickly after I asked "Are you at home, all the time?" and said "Let me know when they're done".

That was the time to teach the lad a lesson (he was there at the time) and I explained that full power isn't achieved when the volume control is at WOT, but closer to 1:00 on the dial. We were the second Jamo dealer in the US, so we had a lot of leeway WRT honoring warranties when we wanted and we covered the repair.

About 5 years ago, I was at Summerfest and during a break in the main act's show, I went out to get something to drink and heard someone ask if I was Jim, from that store. I turned around and he introduced himself, saying he used to hang out with certain people and when I couldn't quite figure out who he was, he reminded me about the blown speakers and I immediately knew who he was. He just hung his head when I said "I remember you!".
 
highfigh

highfigh

Seriously, I have no life.
We used to see the Happy Face with cranked Bass & Treble controls. We also had a guy who wanted a used EQ in the worst way and at some point, we noticed that some of the knobs were missing. As the week went on, more went missing and that Friday, he came in and asked if he could get it for a better price, since it was missing some of the knobs. We knocked off some of the price and he bought it. The next Monday, he came back to return it and, wonder of wonders, it had all of the knobs. He just wanted it for a party.
 
agarwalro

agarwalro

Audioholic Ninja
So I hooked up the cables just to the tweeters and the sound is really faint. Can barely hear anything. I tested the drivers and I'm getting 4.5 ohms out of both of them. They are rated at 8ohms so I'm sure that is a problem.
IMO, take the whole speaker(s) to an authorized B&W repair shop and have them give you an estimate for the repair. In the meanwhile see what they are selling for on the used market. No point paying more than the cost of buying a used pair.
 
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