Wit's End

[IanB]

This really is a desperate move by me. I just joined this site a few hours ago cause I really need some help, and I've talked with electricians and the like and they can't figure my problem out.

Long story short, I've blown out three sets of floorstanding speakers in the past 4 months or so. I have always had a fairly average set up, entry level stuff, nothing fancy. At first I had 2 Polk TSi400 speakers hooked up to a Sherwood RX - 4503. Also had a Polk PSW10 sub, powered. I used 14 gauge wire I believe. This was in December of last year that I hooked it all up and started using it.

http://www.amazon.com/Polk-Audio-TSi400-Floorstanding-Speaker/dp/B0018QROHC/ref=sr_1_1?s=electronics&ie=UTF8&qid=1435718817&sr=1-1&keywords=tsi+400

http://www.amazon.com/gp/product/B001E2UKSU?psc=1&redirect=true&ref_=oh_aui_detailpage_o05_s04

Links for specs. These worked from when I got them in December til mid March 2015. I was using my iPod to listen to music while cleaning the house, using an RCA to 3.5mm adapter. Volume was a little above half, nothing too crazy. Suddenly, I smell burning rubber/plastic and notice the sound quality has dipped crazily. One of the tweeter cones actually blackened and became stiff to the touch. I cursed my bad luck, but I've been using speakers for 15 years and this was the first time I've ever had them blow up on me, so whatever. A fluke, I thought.

I got two replacements, same thing, the TSi400s. A week later, same thing. This time I was using them hooked up to my PC, since I like to use my big 60 inch TV for gaming and Netflix. Volume wasn't even half this time, and boom, they sound hollow and tinny out of nowhere. Now I know something is messed up.

So I decided to take things seriously. I got an electrician to come out a few days later, she tells me the readings from all my outlets are normal and she can't imagine why two sets of speakers would blow up on me. I had her install a whole house surge protector any way as a precaution. I bought new surge protectors for the outlets, new cables for all my inputs, new 10 gauge speaker wire, the works. Everything new except for my tv and the sub. I thought maybe the receiver was the problem, so I got a Yamaha RS - 500. Still an entry level AV receiver, but double the price of the Sherwood. For speakers, I like Polk too much to forsake them, so I decided to try a different series. I ordered two TSx 440Ts. Still not audiophile territory, but a good 150$ more than my old ones. So everything is new and fresh, the whole system has been replaced, and I've upgraded across the board. I even used a different outlet to make sure absolutely everything was different.

http://www.amazon.com/Yamaha-R-S500BL-Natural-Stereo-Receiver/dp/B0044779GI/ref=sr_1_1?s=electronics&ie=UTF8&qid=1435719728&sr=1-1&keywords=rs500

http://www.amazon.com/Polk-Audio-TSx-440T-Speaker/dp/B00CHHCBW4/ref=sr_1_1?ie=UTF8&qid=1435719720&sr=8-1&keywords=tsx+440

More links. I'm sure you guys can guess what happened next. I got three months out of this new setup, before last night. Boom, sudden drop in audio quality. They sound muffled and faraway, voices are very indistinct, murky and gross sounding bass. Barely listenable. It just suddenly happened while I was watching a Youtube video at average volume.

I don't know what to do. I desperately want to have speakers again, but this is starting to get very expensive and if I blow out a fourth set I'll go insane. Typing this out, I thought that maybe using my computer's sound card would cause a problem, but the first time it happened was with an iPod, so that discounts that theory. I also used my computer with a very similar home theater set up for ten months with no problems back when I lived with a girlfriend, so I don't think using a computer as an audio source should be a problem.

Does anyone have any clue as to why I'm getting these issues? True to my thread title, I'm at my wit's end and I would really, really appreciate any insight. If you read all this, thank you so much.

 

[Johnny2Bad]

Sounds like you are clipping the amplifier. How loud do you listen at?

The volume control is not like a gas pedal ... it's relative position does not indicate the actual power output. Most are designed to clip the amp at 2:00 if the input sensitivity of the amp equals the output voltage of your source.

If your source (eg your computer soundcard) puts out a higher voltage than the input sensitivity of your amp, you might clip at 12:00 on the volume dial or even lower. You can't go by it's position as some guarantee you are not turning it up too much ... how loud it is actually playing determines that.

If you like it loud, you need to look at higher efficiency speakers. Your Polks are rated at 90dB/2.83V/1M. Look for speakers rated at above-average efficiency ... 93dB/2.83V/1M or higher. Typically that would be horn-loaded speakers, such as those made by Klipsch.

 

[shadyJ]

I would be looking at the DC offset in the amp. You need to measure that to be sure it isn't causing the problems. Look at this guide. An offset DC can cook your tweeter very quickly. Also, like Johny said, if there is clipping anywhere in the signal chain, it will jack up the high frequencies through distortion which can overtax the tweeter. Make sure the source voltage output is at a nominal level. Nothing should be turned up to max volume. Also, the tweeters in Polks lower end lines like the TSi and Monitor series are very poor. I don't know how you lived with them for so long, but I am betting they aren't able to take too much abuse.

 

[agarwalro]

Volume was a little above half, nothing too crazy. Suddenly, I smell burning rubber/plastic and notice the sound quality has dipped crazily. One of the tweeter cones actually blackened and became stiff to the touch.

Volume wasn't even half this time, and boom, they sound hollow and tinny out of nowhere. Now I know something is messed up.

I got three months out of this new setup, before last night. Boom, sudden drop in audio quality. They sound muffled and faraway, voices are very indistinct, murky and gross sounding bass. Barely listenable. It just suddenly happened while I was watching a Youtube video at average volume.

Ian,
Welcome to the forum. Could have probably saved you the electrician bill. Better late than never and now you have whole house surge protection .

What you consider "average volume" or "not too loud" is still driving the amp into distortion. It must be relatively low level clipping (which is why the speakers don't blow right away), but enough to kill the driver over time. Depending on what is playing (track) when it does fail, either you're blowing the tweeter (things sound muffled) or woofer (things sound tinny) or one of both.

IMO you something like this speaker, http://reaction-audio.myshopify.com/products/cx-10?variant=823614953

Ugly... yes, but I guarantee your ears will bleed (from loudness and not sound quality) before they or the amp give out.

 

[macddmac]

Get your hearing checked while you're at it-
You never know, what used to be not too loud could be screeching now without you noticing it.

 

[highfigh]

One thing that would help (or should, anyway) is using a subwoofer. Removing the low frequency content from the signal being sent through the receiver's amplifier will allow it to operate at the level that cooked your speakers without distorting. That doesn't mean that you should crank it louder, though. If you really want it loud, buy more power and speakers that can handle that power.

Bass content plays a huge part in how we perceive loudness. If a sound seems loud but the measured level is lower than it seems, that indicates the intensity of the sound. Loudness is measured and strong bass adds to the sensation of the sound, e.g., you can actually feel it, which doesn't happen with mid-range or high frequencies unless the SPL (Sound Pressure Level) is extremely high.

Raising the volume control when the amplifier isn't able to develop clean high power is similar to using a car with a low power engine to race or tow something- it doesn't work well

BTW- the Yamaha deceiver is rated at 75W/channel, so there was little chance that it would be louder than the Sherwood. If you want to save money, buy a used receiver that has a pair of preamp output jacks and then add a used power amp that's more powerful. That doesn't do anything about the speakers, though. They often have a spec called 'Sensitivity' and that tells us about the output at a specific input voltage. Since the spec is done at the same voltage for most speakers, it helps us decide if a speaker will do what we want and in this case, where loudness is a goal, this is important.

Another way to achieve higher output is to use more speakers but again, the power needs to be available. If you Keep the volume control setting a bit lower, four speakers will fill the room better than two, but it may not actually be louder.

 

[IanB]

Sounds like you are clipping the amplifier. How loud do you listen at?

The volume control is not like a gas pedal ... it's relative position does not indicate the actual power output. Most are designed to clip the amp at 2:00 if the input sensitivity of the amp equals the output voltage of your source.

If your source (eg your computer soundcard) puts out a higher voltage than the input sensitivity of your amp, you might clip at 12:00 on the volume dial or even lower. You can't go by it's position as some guarantee you are not turning it up too much ... how loud it is actually playing determines that.

If you like it loud, you need to look at higher efficiency speakers. Your Polks are rated at 90dB/2.83V/1M. Look for speakers rated at above-average efficiency ... 93dB/2.83V/1M or higher. Typically that would be horn-loaded speakers, such as those made by Klipsch.

I can't really give a real estimate on how loud I listen. I keep the receiver at around -30 to -10, and then my computer is what I use to control my volume. I keep it at about half normally, which makes the sound room filling, but not wall shaking. So above average efficiency is 93dB? Got to admit, that wasn't a spec I ever looked at when comparing speakers.

 

[shadyJ]

That doesn't seem like it should cause clipping unless there is something malfunctioning somewhere. The only way to know for sure is to test stuff. Make sure the output voltages are where they are supposed to be. Using another speaker isn't going to fix the problem if it is a matter in the signal chain or amplification. The thing is, if the issue was clipping, I would think you would hear it, as it should sound bad, even worse than how Polk's regularly sound.

 

[IanB]

I would be looking at the DC offset in the amp. You need to measure that to be sure it isn't causing the problems. Look at this guide. An offset DC can cook your tweeter very quickly. Also, like Johny said, if there is clipping anywhere in the signal chain, it will jack up the high frequencies through distortion which can overtax the tweeter. Make sure the source voltage output is at a nominal level. Nothing should be turned up to max volume. Also, the tweeters in Polks lower end lines like the TSi and Monitor series are very poor. I don't know how you lived with them for so long, but I am betting they aren't able to take too much abuse.

I lived with them so long cause I'm poor as hell lol. I may end up getting some decent stuff once I figure out what I need, however. You guys have been very helpful. I wasn't sure what sort of responses I was going to get, but I'm very happy to see that all the replies so far have been well thought out and helpful. This forum is awesome.

I borrowed a multimeter and checked the offset. Yesterday, I followed that guide and set my Yamaha up by switching it to an unused input, lowered the volume all the way, and set all the dials to the neutral positions. I checked it right away and got levels around 30 to 60. Then I checked around 20 minutes later and the A terminals were reading around 100, B's were at 30 to 60. After an hour or so, the A terminals were all reading over 150, while the B terminals were staying solid at 30 to 60. This was plugged into a surge protector that I have my tv, blu ray, etc. plugged into as well. And I had my speakers plugged into A, so I figured there's my problem, right?

Now I may be more confused than ever haha. I took my receiver into the kitchen and tried it there. Took the readings a bunch of times, now the A terminals never read over 60, same as the B terminals. I'm not seeing a crazy spike in the A's like I did when plugged into my power strip. For a final test I took it back into my living room and plugged it into another outlet. Got the same results as when it was in the kitchen. One set of A terminals consistently reads at 30, the other at 57 or 58. One set of B terminals reads at 30, the other at 58 or 59. I've been getting those same readings consistently now. I plugged it back into the surge protector where I got the crazy high readings and for the past half hour I've been trying to replicate the 150+ I was getting yesterday, to no result.

 

[IanB]

Ian,
Welcome to the forum. Could have probably saved you the electrician bill. Better late than never and now you have whole house surge protection .

What you consider "average volume" or "not too loud" is still driving the amp into distortion. It must be relatively low level clipping (which is why the speakers don't blow right away), but enough to kill the driver over time. Depending on what is playing (track) when it does fail, either you're blowing the tweeter (things sound muffled) or woofer (things sound tinny) or one of both.

IMO you something like this speaker, http://reaction-audio.myshopify.com/products/cx-10?variant=823614953

Ugly... yes, but I guarantee your ears will bleed (from loudness and not sound quality) before they or the amp give out.

I've never heard of the CX-10. I was hoping to replace my broken Polks with a much higher quality speaker, but I was looking at floorstanding. Will those work in a 2.1 home theater setup? Not sure about aesthetics either. I don't mind that they aren't the prettiest of speakers, but I think I'd need to get some stands to get them at the right height, and that means my TV area is going to look like a studio haha. I much prefer the look of floorstanding speakers next to my tv.

 

[IanB]

Get your hearing checked while you're at it-
You never know, what used to be not too loud could be screeching now without you noticing it.

Funnily enough, I just got my hearing checked a few months back. I took a physical for a new job. The nurse said I had normal hearing.

 

[IanB]

One thing that would help (or should, anyway) is using a subwoofer. Removing the low frequency content from the signal being sent through the receiver's amplifier will allow it to operate at the level that cooked your speakers without distorting. That doesn't mean that you should crank it louder, though. If you really want it loud, buy more power and speakers that can handle that power.

Bass content plays a huge part in how we perceive loudness. If a sound seems loud but the measured level is lower than it seems, that indicates the intensity of the sound. Loudness is measured and strong bass adds to the sensation of the sound, e.g., you can actually feel it, which doesn't happen with mid-range or high frequencies unless the SPL (Sound Pressure Level) is extremely high.

Raising the volume control when the amplifier isn't able to develop clean high power is similar to using a car with a low power engine to race or tow something- it doesn't work well

BTW- the Yamaha deceiver is rated at 75W/channel, so there was little chance that it would be louder than the Sherwood. If you want to save money, buy a used receiver that has a pair of preamp output jacks and then add a used power amp that's more powerful. That doesn't do anything about the speakers, though. They often have a spec called 'Sensitivity' and that tells us about the output at a specific input voltage. Since the spec is done at the same voltage for most speakers, it helps us decide if a speaker will do what we want and in this case, where loudness is a goal, this is important.

Another way to achieve higher output is to use more speakers but again, the power needs to be available. If you Keep the volume control setting a bit lower, four speakers will fill the room better than two, but it may not actually be louder.

I do have a sub. I listed it in my original post, a Polk PSW10. I didn't link to it cause it didn't blow out or cause any problems.

Thank you very much for the advice. I think you're getting the wrong idea about how I listen, though. I know it sounds bad, having blown out three sets of speakers in a few months, but I have no reason to lie to you guys. I really wasn't listening that loud. Loud enough to fill the room, and audible a bit throughout the rest of the house, but that's it. I'm not looking to destroy my ears and no part of my setup, whether it was the input device or the receiver, was cranked up to max levels.

Since Monday I've been looking at different speakers, amps, and receivers, trying to find something that is hardy as all hell but also at least a little bit affordable. I'm ready to spend a few grand on something nice, but if I somehow blow them out AGAIN I'll cry. I thought of getting an actual amp and I couldn't remember if my Yamaha had a pre amp out or not. Sadly, no. It was the next level up, the RS 700, that has pre amp outs. I got the RS 500.

When I bought this stuff, I was sort of just using common sense to calculate how well these components would work together. Not the smartest, I know. I mean, those theater in a box set ups you can buy at Wal Mart and the like aren't the greatest but people use them for years and years with no trouble. My uncle has one that has lasted him a decade, no blowing out. So I figured, a $350 receiver with two $350 speakers and good quality wire should be able to last a while too, right? Again, I know that's nothing for a true audiophile. I know the Yamaha is 75w per channel, but that should have been more than enough for my needs. Or so I thought.

 

[Rickster71]

Welcome to the forum Ian.
In the spirit of trying to check every possibility; is it possible the problem is in the way the speaker wiring is hooked up? Shorted with a single strand of wire touching something?
Another possibility is too much insulation stripped off. I've seen instances where 2" of the insulation was stripped off and the remainder left dangling to short to the chassis.

 

[IanB]

Ok so ignore my DC offset stuff from before. Turns out I get the high readings (100mV+) when I have the speaker selectors off. I can select from A and B, or both. With the speaker selector set to A, which is what I was using at the time they blew out, the set of terminals I used for my left speaker are giving me 57-59mV consistently, and the one I was using for the right speaker is giving me 28-30mV consistently. It does the same thing no matter where I plug it in, so I don't think I have a messed up outlet or anything.

I hope the more electrically-minded of you can tell me what that means. The guide says below 50 is ok, and anything above may cause distortion, while 100+ may damage components.

 

[IanB]

Welcome to the forum Ian.
In the spirit of trying to check every possibility; is it possible the problem is in the way the speaker wiring is hooked up? Shorted with a single strand of wire touching something?
Another possibility is too much insulation stripped off. I've seen instances where 2" of the insulation was stripped off and the remainder left dangling to short to the chassis.

Thanks for the reply. I'm no electrician, but I use banana plugs and only strip the last inch or less. The strands are all snugly secured in the top portion, and then there may be a small amount of bare wire trailing down from the top, but the clips I use have rubber base that protects even that small amount from touching anything. Just looking at them now, there is no visible wire at all.