Hi,
I have a pair of B&W DM580 speakers, and just got a new amp for them. The amp is a Yamaha RX-V1300, which is a 6 channel surround amp. It puts out 600W, 100 per channel. My speakers can handle 150W.
For some reason, when the volume is at about -27 db or so, and a deep bass note hits, one speaker's fuse will blow. I replaced it with a new 2A 250V, just like the old one, and it blew again. The other speaker, which I checked also has a 2A 250V fuse, didn't blow either time. Thinking the amp was bad, I switched the speakers, and the same one that blew before did it again, yet the other speaker is still on the original fuse. This makes me think there is something wrong with the speaker, but I have no idea what, except for possibly a loose wire or a short somewhere?
Any ideas on how to fix what is happening would be greatly appreciated.
Thanks, Mike
I have a pair of B&W DM580 speakers, and just got a new amp for them. The amp is a Yamaha RX-V1300, which is a 6 channel surround amp. It puts out 600W, 100 per channel. My speakers can handle 150W.
For some reason, when the volume is at about -27 db or so, and a deep bass note hits, one speaker's fuse will blow. I replaced it with a new 2A 250V, just like the old one, and it blew again. The other speaker, which I checked also has a 2A 250V fuse, didn't blow either time. Thinking the amp was bad, I switched the speakers, and the same one that blew before did it again, yet the other speaker is still on the original fuse. This makes me think there is something wrong with the speaker, but I have no idea what, except for possibly a loose wire or a short somewhere?
Any ideas on how to fix what is happening would be greatly appreciated.
Thanks, Mike
As you say it happens during bass notes I suspect that you may be clipping your amp, a 100 W amp will blow 150W speckers if over driven. check wiring around fuse as a hot connection will cause fuse to blow early, 2A x 250 volt = 500 w, lower voltage of use will reduce wattage of fuse but I wouldn't trust im to save my B&W's, also check with ohm meter and ear. hope this helps good luck Mark
Hello Mike 😉
You say that you only got the problems with one of the speakers, and that you have tried switching the channels from your amp...
Your problem must is absolutely be in the speaker, where the fuse keeps blowing.
Did you have these speakers from new???
Are you using slow or fast fuses???
If you have purchaced the speakers used, then the problem could be, that the former owner had replaced a slow fuse with a fast fuse in the speaker thats fails...
Or that the fuse in the speaker that works has a benn replaced (from fast to slow, and that it is your amp that clips...
Do as Mark says. Check with a ohm meter.....
You say that you only got the problems with one of the speakers, and that you have tried switching the channels from your amp...
Your problem must is absolutely be in the speaker, where the fuse keeps blowing.
Did you have these speakers from new???
Are you using slow or fast fuses???
If you have purchaced the speakers used, then the problem could be, that the former owner had replaced a slow fuse with a fast fuse in the speaker thats fails...
Or that the fuse in the speaker that works has a benn replaced (from fast to slow, and that it is your amp that clips...
Do as Mark says. Check with a ohm meter.....
I would also inspect the crossover board on that speaker and look for any signs of over heating or poor solder joints
I bought them used, and I looked at both speakers fuses. They both have a fast blow fuse, since they both have just a strand of wire in the fuse.
I will check them with my multimeter and report back. What am I looking at when measuring ohms? Too high or too low of a value?
Yes, I did switch the speakers to make sure it isn't a bad amp, and the same speaker as before blew.
I couldn't hear any clipping when they blew, and I would think these speakers could go to louder volumes than they were to when the fuse blew.
How can I get to the crossover? There aren't any screws on it's metal plate. Do I have to remove the drivers?
Thanks, Mike
I will check them with my multimeter and report back. What am I looking at when measuring ohms? Too high or too low of a value?
Yes, I did switch the speakers to make sure it isn't a bad amp, and the same speaker as before blew.
I couldn't hear any clipping when they blew, and I would think these speakers could go to louder volumes than they were to when the fuse blew.
How can I get to the crossover? There aren't any screws on it's metal plate. Do I have to remove the drivers?
Thanks, Mike
soundNERD said:
This isnt so I have bought quite a lot of slow blow fuses and they all just have a strand of wire in the fuse. Unless you are refering to a strand as a cylinder of wire and not a piece of foil with a cross sec of a coupla mm. I have got some slow blow which look like litebulb fillaments buts thats completely differnt.
I just did a search for the speakers in question and I see what tou mean about cabinet access. WOuld it be possible to remove those white bands around the drivers, I bet if you can the screws would be hidden beneath. Alternatevly try gainin access from the input terminals.
How much are the drivers actually having to work to produce this "note" when the fuse blows? It does sound like there is a problem with one of the speakers. But is it possible that they are working around thier power limits anyway? Or can you advance the volume quite a bit more and the other speaker plays without any problem?
The pair of B&W speakersI had would blow the GMA 2 fuse about once a week . Have you set the bass roll off of your receiver or the low end EQ If not raise the roll off and lower the bass bost EQ .Check to make sure the vioce coil is not rubbing on the offending speaker .The crossovers may have zenner diodes to protect the speakers , the one that blows the fuse my be operating normaly and the other may have an open zenner or the one that blows the fuse may be over heated .Do you have any test Equiptment ? .
The gma 2 fuse will blow at 32 watts of sustained music on an 8 ohm speaker .
A 3amp will bllow at 72 watts .
Mark
A 3amp will bllow at 72 watts .
Mark
battradio,
That doesn't quite make sense. My speakers have power handling of 10-150W, so the fuse shouldn't blow when the amp puts out 32W, right?
Also, I will need to check, but I think the fuses are GMA 2 types also. At least I think it is printed on them.
-Mike
That doesn't quite make sense. My speakers have power handling of 10-150W, so the fuse shouldn't blow when the amp puts out 32W, right?
Also, I will need to check, but I think the fuses are GMA 2 types also. At least I think it is printed on them.
-Mike
If you assume a crest factor of 20dB then in theory the 2A fuse is overrated by a factor of two, since it will allow peaks of 320W despite the 32W RMS rating. But if you are playing loud bass music, or especially if you are clipping, the crest factor could be much lower.
Indeed, a 2 amp fast blow fuse will blow if much more than 32W average passes thru it CONTINUALLY. They are counting on the rather low ratio of high energy passages to low energy passages within typical music. Typically, most of us listen to music with only a few watts of output during a large percentage of the programme and so the fuse survives. A typical 2 amp fast blow fuse with an 8 ohm resistive load will take 0.5 seconds to blow when fed with 128W sustained. You would probably be better served with a 2.5Amp fast blow or a 2 amp slow blow but having said that, I have no idea if the speakers can take the strain if you put them in that circumstance. Switch the 'good' fuse into the 'bad' speaker and put a new fuse of the same type and rating into the 'good' speaker and see if it blows. If the fuse still blows, there is a problem with that speaker somewhere. I'm almost 100% sure that that is the case already but it doesn't hurt to make sure, after all, fuses are pretty cheap by comparison.
Mike,
(1) Fuse type
Did you try swapping the fuses as SkinnyBoy suggested ? Just because it says 2A you can never be sure ....
As you point out a 2A fuse with a nominal 8ohm load will give 32w RMS (I*I*R) - this is the continious power rating (ie the thermal rating) but the speaker **should** be able to handle substatially more providing it is for a short period (guessing about 4 times). It is quite normal for speakers to be specified this way.
My guess would be that this should be an anti-surge type fuse (different from slow-blow ?).
(2) Crossover / drive units
Have you tried listening carefully to the speakers at a level somewhat below the level where the fuse blows ?
Does everything sound OK ?
If everthing sounds fine right up until the fuse blows your problem is most likely an intermitant short.
Dave
PS
It may be possible to temporarily replace the fuse with a bulb - this will protect the amp and speaker and will aid fault finding without causing further damage.
(1) Fuse type
Did you try swapping the fuses as SkinnyBoy suggested ? Just because it says 2A you can never be sure ....
As you point out a 2A fuse with a nominal 8ohm load will give 32w RMS (I*I*R) - this is the continious power rating (ie the thermal rating) but the speaker **should** be able to handle substatially more providing it is for a short period (guessing about 4 times). It is quite normal for speakers to be specified this way.
My guess would be that this should be an anti-surge type fuse (different from slow-blow ?).
(2) Crossover / drive units
Have you tried listening carefully to the speakers at a level somewhat below the level where the fuse blows ?
Does everything sound OK ?
If everthing sounds fine right up until the fuse blows your problem is most likely an intermitant short.
Dave
PS
It may be possible to temporarily replace the fuse with a bulb - this will protect the amp and speaker and will aid fault finding without causing further damage.
One general question: When driven at "safe" levels, do both speakers sound the same ?
Regards
Charles
Regards
Charles
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