Speaker issues.

[nino]

Hello everyone,

I was hoping someone could shed some light on what just happened to my beloved set of mission 737Rs. I have them hooked up in my main system an apt holman pre/power amp and a kenwood record player. I often stream music also. I noticed the sound coming from the right speaker was a little off to start( started about 10 days ago) but would become normal after the first song was played. I figured since it was older equipment it was somewhat normal. Today I hooked it up to my Ps audio 5.5 pre amp/ ps audio cx200 power amp and played it with the same record player and streaming device. After the first side of the record I noticed that the woofer was no longer working. The woofer is stiff and will not move.

I understand the woofer is fried, but why? To trouble shoot I had switched the speakers left and right hook up on the amp. The left speaker worked perfect with both sides. Yes I understand the speakers are about 30 years old.

Thoughts? suggestions? Should I go get my amplifers checked out? Would rather not fry another set of speakers.

Cheers,
Nik

[davef]

Hello everyone,

I was hoping someone could shed some light on what just happened to my beloved set of mission 737Rs. I have them hooked up in my main system an apt holman pre/power amp and a kenwood record player. I often stream music also. I noticed the sound coming from the right speaker was a little off to start( started about 10 days ago) but would become normal after the first song was played. I figured since it was older equipment it was somewhat normal. Today I hooked it up to my Ps audio 5.5 pre amp/ ps audio cx200 power amp and played it with the same record player and streaming device. After the first side of the record I noticed that the woofer was no longer working. The woofer is stiff and will not move.

I understand the woofer is fried, but why? To trouble shoot I had switched the speakers left and right hook up on the amp. The left speaker worked perfect with both sides. Yes I understand the speakers are about 30 years old.

Thoughts? suggestions? Should I go get my amplifers checked out? Would rather not fry another set of speakers.

Cheers,
Nik

A stiff woofer, as you have described, happens with the voice coil burns and fuses to the pole piece or magnetic gap. Typical cause for this is a DC offset in your amp (amp needs to be repaired) or pushing the woofer to hard with very deep bass and too much power. Being that the woofer is at least 30 years old, it is also possible that the voice coil adhesive has broken down causing the coil to unwind and then short.

First step is to check out your amp - if it is bad, it will continue to damage speakers.

[nino]

I appreciate the reply Dave! Not sure if you are familiar with the PS audio Cx200, but on the rear of the amp it has DC input and AC input from the preamp. Would it have fried because it was hooked up to the DC input?

Would it be hard to diagnose the amp? just trying to figure out how much that should or will cost me.

[davef]

I appreciate the reply Dave! Not sure if you are familiar with the PS audio Cx200, but on the rear of the amp it has DC input and AC input from the preamp. Would it have fried because it was hooked up to the DC input?

Would it be hard to diagnose the amp? just trying to figure out how much that should or will cost me.

DC input? This doesn't make much sense to me. Please post a picture of the back of your amp.

[MusicHead]

The OP is referring to the input coupling, DC or AC:

http://img.canuckaudiomart.com/uploa...udio-200cx.jpg

[Mag_Neato]

The OP is referring to the input coupling, DC or AC:

http://img.canuckaudiomart.com/uploa...udio-200cx.jpg

That's a new one on me.

what Dave is referring to is DC Offset. On my amp I measured this with a millivoltmeter placing the two probe leads across speaker output. The spec for my amp is 0mV +/- 10mV.

[MusicHead]

That's a new one on me.

what Dave is referring to is DC Offset. On my amp I measured this with a millivoltmeter placing the two probe leads across speaker output. The spec for my amp is 0mV +/- 10mV.

Yes, I know what Dave is referrring to Just wanted to clarify what was said about the amp, so that we get that out of the way and focus on what the real issue might be.

[Mag_Neato]

Yes, I know what Dave is referrring to Just wanted to clarify what was said about the amp, so that we get that out of the way and focus on what the real issue might be.

Ah, perhaps I snagged the wrong quote. I was directing this at the OP.

With the age of my Adcom it is something I monitor on occasion.

[davef]

I appreciate the reply Dave! Not sure if you are familiar with the PS audio Cx200, but on the rear of the amp it has DC input and AC input from the preamp. Would it have fried because it was hooked up to the DC input?

Would it be hard to diagnose the amp? just trying to figure out how much that should or will cost me.

Not likely.. The DC and AC inputs are just the coupling - the AC coupled input likely has a capacitor in series with the input which would block any DC from reaching the internals. It is possible that another component in the signal chain located before the amp is producing DC, in which case connecting to the DC coupled input would allow the DC to reach the amplification stage - but this is highly unlikely as it is much more common for the amp itself to produce DC, especially if the power supply filter caps start to go bad (electrolytic caps have a finite lifespan)

You can measure the DC offset of the amp with a simple voltmeter.

[nino]

Thank you for all the responses. That is the back of the amp. I have since used a volt meter and yes the amp has gone in for repairs. I appreciate all the help!