Tell me this isn't strange (1 Viewer)

[Dereck Graefer]

OK. My head is really spinning right now. I bought a pair of JBL S310II's a while ago with a Denon 1602. The left speaker was distorting and I was under the assumption that I clipped the speaker with the low powered Denon. So I took the speaker back, and replaced the Denon(With a Yamaha RX-V730). I needed a receiver with pre-outs to add an amp so I wouldn't have to live in fear of clipping anymore. Anyways today my replacement JBL came in. I went down, picked it up, and guess what - same problem. When output hits about 80dB, I can hear the replacement speaker distort while listening to classical music. I haven't pushed these speakers hard since I got the replacement(The highest they have gone is 80dB). At first I thought maybe they just re-packaged my old speaker and gave it back to me, but they ARE different speakers. (I know because I used pledge dust remover on the speaker I returned. If it was my original speaker, it would still smell like pledge.) I've tried many different configurations and the distortion sticks to the one speaker. I've switched channels. I've moved the speakers to other parts of the room. Replaced every cable. Tried a different CD player. Pretty much every thing I can think of. I'm pretty sure I didn't wreck the replacement(Im even starting to think I didn't wreck the first one). My logic is as follows:

My Yamaha is not the highest powered receiver, but it should have no problems pushing a single S310II to 80dB peak at 1m. in fact, this requires me to turn the receivers volume almost half way. So, i'm pretty sure I didn't clip the replacement speaker. Now, the original speaker, was pushed to about 105dB on my Denon. Is it possible I clipped the original speaker? I think it's possible. But after getting a second bad speaker, im starting to think it was wrecked to begin with. Also, what about the other speaker .. it sounds great. If I wrecked the first one, wouldn't the second speaker be wrecked too?

Has anyone else had this sort of problem with speakers? Two bad speakers in a row seems odd.

I have a feeling that my dealer is going to think im nuts when I return this second speaker. I would feel better if I knew that this kinda thing happens frequently. Also, some people say i'm very picky with what I hear. Is it possible for two same model speakers to sound different? One sounds clear, the other distorts a tiny bit? Should I just stop being picky and live with what I think is a problem? Anyways, any insight would make me feel better.

 

[Chris Tsutsui]

Unless the distortion only comes from one speaker no matter which way you wire it, I think that it is highly likely that the distortion is being caused by the receiver or source player.

I too noticed something similar in that sometimes the soundstage will sound shifted slightly to the left even if I swap front speakers. At first I thought that it was a speaker flaw or one of my amp channels had a problem but then I isolated the problem to the pre/processor.

Just like you I suspected the speaker to be the culprit first as I swapped them and ended up with the same shifted sound stage.

Believe it or not, speakers can really take a beating, especially those JBLs. You can clip the amp hundreds of times and bottom out the driver and I still don't think the speaker's performance would be in any way affected.

Good luck

 

[Dereck Graefer]

This makes me feel better. Im so paranoid about clipping. Thanks.

 

[Brian Fellmeth]

You have done all of the right diagnostic manuvers and your conclusion that both your original left and the replacement left are malfunctioning is inescapable. One thing to check though is if your receiver is damaging the speakers with an inaudible DC offset. Do you have a volt meter to check this ?

 

[Dereck Graefer]

Well Brian, I can use a multimeter to check the voltage. I'm just curious to the procedure for the test. What is the process of such a test? I know how to measure voltage, just not sure how I should set the receiver and such to take readings.

 

[Bill Mullin]

both your original left and the replacement left are malfunctioning

I purchased a JBL S120Pii sub and found that it had two very serious defects. So I returned it for a replacement, and the new one had exactly the same problems. Rather than mess with this any longer, I returned the JBL and purchased a Velo HGS-12, Series II.

I realize that subs and speakers are not quite the same, but this experience and yours has me wondering about JBL's quality control! FWIW, my fronts and rears are JBL - all are fine.

- Bill

 

[Dereck Graefer]

I am definitely starting to question JBL's quality control. I've gotten bad JBL product before, but that was 5 years ago and a totally different product line(Car Sub-woofers). I'm looking into this DC offset Brian mentioned. But I doubt it's that. I say this because in addition to having two different speakers, im using different receivers. If DC offset was the problem, then my Denon receiver wrecked my first speaker, and my new Yamaha wrecked my replacement speaker. Different speakers and different receivers, same problem. The chances that both receivers have a DC offset is nil. I'm still going to investigate the DC offset idea though. I'm willing to try anything.

 

[Brian Fellmeth]

The chances that both receivers have a DC offset is nil.

Agreed. This is a rare malfunction in a receiver. Also, I expect it would have fried your good "right" speaker when you tested it on the left channel. But FYI, the way to check the output is just what you would expect. Put volt meter on a very sensitive range. For maximum sensitivity, remove speaker wires from lugs and check for a measurable DC voltage while the receiver is active and sending a signal. Should read well under 1 volt.Examine both polarities. don't short the speaker leads while receiver playing !

 

[Dereck Graefer]

Well I did a voltage measure. The readings from both the left and right channel were well under 1 volt. While taking readings, I found an inconsistency between the left and right channel. With the receiver just turned on and muted, I found that the left channel has a higher voltage reading than the right. I don't know much about electronics, but would I be correct in saying that both channels should output a voltage that is approximately the same while the receiver is in mute mode?