Built some Khanspires, now having some distortion problems.

[gdub25]

I built a set of Khanspires for my theater mains and they are awesome. Thank you to everyone here who helps beginners like me be able to build speakers of a high quality that I would otherwise never have the chance to own. Special thanks to CJD and ---K--- for taking the time to help me decide on the Khanspires in the first place and then answer specific questions regarding my personal setup. I think the Khanspires were a perfect choice for my theater, and the sound from them is better than anything I've ever heard before. I really can't say enough good about them.

Now to my problem. These speakers are about three months old. I was listening to some heavy metal and turned the receiver up really loud and after a few seconds I heard a lot of static/crackling from the speakers and then the receiver shut off. I assume I was pushing it way too hard and it overheated? Ever since that happened I have been noticing some poor sound quality with certain songs. Things sound nice and clean until a certain note or frequency is reached and then it sounds like the cone of one of the drivers is vibrating up against a trash bag or tin. It is particularly noticeable with drawn out notes. Best I can tell I get this coming from both the left and right speakers. Any ideas what the problem is? I'm guessing it's a driver problem. Easy enough to replace but I don't want to waste money buying new drivers if that's not the cause.

Also, here are a few pictures of the build.

[Drew_V]

You didn't show any pics of the drivers, but could it possibly be lead slap? It might produce the sound you were hearing.

Also, what sub are you running? Is that a Tuba HT? How much power are you feeding it?

I would isolate each speaker and run it up to volume, without the sub. That way you can see if it's coming from both speakers or just one. Turn up the volume gradually to see if the vibration/noise comes at higher volumes or if it's there all the time.

[Ed H]

I am no help, but I did want to say,

Damn nice home theater, and speakers!! So jealous.

Hopefully you get this fixed soon. I will be watching / learning.

[gdub25]

You didn't show any pics of the drivers, but could it possibly be lead slap? It might produce the sound you were hearing.

Also, what sub are you running? Is that a Tuba HT? How much power are you feeding it?

I would isolate each speaker and run it up to volume, without the sub. That way you can see if it's coming from both speakers or just one. Turn up the volume gradually to see if the vibration/noise comes at higher volumes or if it's there all the time.

The speakers are behind my screen and since it's such a huge pain to take the screen down I haven't physically inspected anything yet. After all, the problem is only transient and heard at certain times, so it hasn't totally killed the sound. I can still enjoy a movie.

I just assumed I had damaged the drivers or reciever since I had turned it up so loud and had the amp shut off just after some bad noises came from the speakers. I kind of thought people here would read my description and say "well obviously the problem is...". I will do some close listening tonight and give more detailed information.

Yes, that sub is a Tuba HT. I have nothing to compare it to in terms of sound quality as this is the first home theater/surround sounds system I've ever had, but I can say that it has some major output. I've had some serious compitetion quality subs in various cars of mine and didn't expect I would be as impressed with the Tuba HT as most people. I was wrong. I have an O-Audio Bash 300W amp powering it and it's too much. I have to keep it turned nearly all the way down to get it calibrated with my system, otherwise it's just too overbearing.

Ed H
I am no help, but I did want to say,

Damn nice home theater, and speakers!! So jealous.

Hopefully you get this fixed soon. I will be watching / learning.

Thanks. I built everything myself. Good learning experience. Now that I have this one under my belt I'm ready to build a real Home Theater.

[cjd]

I had to replace an RS150 on the Garnacha I built my sister, and it sounded an awful lot like you're describing; It was fine except on certain notes - and worse at higher volume. In this case, it turned out the voice-coil former was not fully glued to the cone.

I'm going to guess the crackling you heard was bottoming out something - tweeters being by far the most likely given the mids are in series. This will bottom the voice coil and can trip a protection circuit - but if you have an amp that's not rated 4ohm it will also hit thermal shutdown at high output levels, and the clipping that can occur internally can also damage speakers. It's possible it was some other driver that had glue issues at excursion, so my next guess would be one of the RS225's.

I'd start by trying to find something that will trigger the noise easily and at lower volumes so you don't go deaf tracking it down. Isolate which speaker it is by playing only one at a time. From there, verify what driver is the source of the trouble. It may be easiest to do this by swapping a driver from one of the other speakers.

Of course, it's possible more than one was damaged If you were listening with all 3 front stage speakers, start with the center; It will often get a mix of LR and end up a little hotter.

C

[gdub25]

I've spent the last hour carefully listening to each speaker and although it's very hard to tell exactly, I think I have several bad drivers. The worst for sure is one of the RS150s. It clearly distorts and has a buzz with certains notes. With the others it's really hard to tell. I'm wondering if most of them are affected to differing degrees. I am able to say with some amount of confidence that it's limited to the tweeters and RS150s. I don't think the RS225s have any problems.

The center channel actually sounds the cleanest, but I still don't think it's perfect. Could be that I'm just listening closer than before.

Only option I see is to buy a few new drivers and put them all in one speaker and take a listen. One speaker with all new drivers would give me a baseline to compare against. However, if the problem is in the amp I'd be wasting time and money. Again, I may be listening too hard, but it does seem like when I have both the left and right channels connected to the amp the sound is worse in each speaker as compared to only having one of them connected.

[cjd]

Before we go chasing down new parts, a few more things to try:

A different amplifier. I haven't seen you mention what you're using, but it is possible something has gone awry here.

A different source (Johnloudb recently found that his source of distortion was the iPhone he was using as a source

While it is possible the RS150's are the root of the problem, I would be surprised - again given the fact they're wired in series, so should be seeing significantly less power per driver at any given signal level than the tweeter or the woofers.

Finally, before you go replacing drivers, DO take some time to swap drivers around to see if the problem follows the driver or not.

C

[gdub25]

Receiver is a Denon 2312CI, and I'm playing music through iTunes on a Mac Mini. The connection from the mini to the receiver is HDMI. I don't have another amp and can't think of anyone I know that does.

After more listening tonight, I'm becoming more worried that all of the tweeters may be bad. Listening to Nora Jones, there are several tracks that have symbols played throughout. They sound very scratchy, almost like white noise at times. The center channel has the least problems. I think both of the RS150s are fine there, but not sure about the tweeter. The left and right speakers both have bad RS150s I beleive, at least one bad on each speaker.

One thing that makes me doubt the problem is the amp is the fact that when listening to one speaker, I can definitely hear the problem in one of the RS150s but not the other. However, CJD, you mentioned clipping and thermal shutoff earlier. It's very likely this played a part...I think. My receiver is stable at 8 ohm, and I was pushing these speakers pretty hard. When the amp shut off it was extremely hot and only turned back on after I pointed a box fan at it for about 10 minutes.

I will take what I feel is the worst of the RS150s and switch them out with the RS150s I can't hear any problems with and see how that does. I'll also try finding another amp to put on them, as well as try a different source and will get back with results.

[cjd]

This sucks

I'm going to guess the tweeters bottomed out and are probably the root cause of all your troubles. Can you find a sin sweep (or software to do sin steps) and see if you can isolate further that way?

I have never really appreciated just how good the thermal shutdown is in the LM3875 I guess.

C

[gdub25]

Just tried a few sweeps as well as various test tones. Couldn't really tell too much from the sweeps, but with the test tones I tried (500, 1k, 2k), 1k was where I could hear it. It wasn't near as pronounced as compared to listening to music though. I swapped drivers around and the problem appears to be driver specific with a couple of them being obviously worse than others. I can't be sure that any of them are undamaged though. Looks like my next move is to order a few drivers and replace them in one of the speakers and compare the sound?

[cjd]

Without measurement equipment, that may be the most direct route to finding a solution.

Do a visual inspection - if it's an issue similar to what I found on the RS150 I had troubles with here, it'd be a warranty issue.

[---k---]

I got more amp power than you. Based upon how hard I've pushed mine, I have a hard time believing that you have damaged the drivers without help from an amp failure.

After testing the amp, I probably would be inspecting the crossovers. If no damage there and they are wired correctly, I would pull each driver out and test it sitting on the table with low level sweeps looking and listening.

[cjd]

Good call on the crossovers.

Individual driver testing, if it's a resonance issue, may take sweeps up to ~2k (on mids) - or steps. I know ARTA would let you run all the sweeps, etc. you need but it's not OS X software - not sure if fuzzmeasure or anyone else has a similar free version (that's simply feature-gimped unless you license) - yeah, they're measurement packages but you can just ignore the measurement part.

If you're so inclined and it gets that far to frustrating, you can send me drivers for testing - shipping won't be cheap though. :/

[gdub25]

Thank you guys for helping me out. I would be very frustrated already if it weren't for the advice and guidance provided.

I was looking on Parts Express at replacement drivers and saw they offered free driver testing. Was considering sending them a couple to test, so I appreciate your offer to test the drivers CJD. I may take you up on it. I've accepted the fact that whatever the problem is probably wont be cheap to fix, and honestly, just spending the money to get to the bottom of it will be much better tolerated around my house than days/weeks of frustration.

I'm going to take a look at the crossovers and make sure everything there looks ok, and I'm still trying to find another amp.

I got more amp power than you. Based upon how hard I've pushed mine, I have a hard time believing that you have damaged the drivers without help from an amp failure.

So how much can these speakers take? With my current setup I like to watch a good action movie with the volume around -10 to -6, I believe +10 is the max, and with some good rock music I find myself wanting a little more. I have read a bit about clipping but am not sure I understand it completely. It sounds like maybe I need more amp and the speakers could deliver more?

[cjd]

If PE will test, I'd go that route - if any are warranty, it'll be easier all around (and no double-shipping)

I'll have to run the numbers on the RS28 but it should be the weak link (that, or the RS225's) crossover aside. Should do 110dB+ easily for a single at 1M if I recall correctly.

[---k---]

So how much can these speakers take? With my current setup I like to watch a good action movie with the volume around -10 to -6, I believe +10 is the max, and with some good rock music I find myself wanting a little more. I have read a bit about clipping but am not sure I understand it completely. It sounds like maybe I need more amp and the speakers could deliver more?

Movies at -10 to -6 shouldn't be a problem. I typically do somewhere around -14, but have done louder. Movies are usually much gentler than music.

But, if your system setup is calibrated correctly, I have a hard time imagining turning music up to +10 and wanting more. That is insanely loud. Either you're looking to feel like you're in the front row at a rock concert, your hearing is already gone, or you got something wrong. Seriously, that volume level should leave your ears ringing.

I don't know. It is hard to say without seeing/hearing it.

[gdub25]

If PE will test, I'd go that route - if any are warranty, it'll be easier all around (and no double-shipping)

I'll have to run the numbers on the RS28 but it should be the weak link (that, or the RS225's) crossover aside. Should do 110dB+ easily for a single at 1M if I recall correctly.

I'll contact them today and see what they can do. I don't really know what 110dB sounds like since I have never heard speakers and known the dB they were playing at, but from what I've read 110dB is pretty loud, correct?

Movies at -10 to -6 shouldn't be a problem. I typically do somewhere around -14, but have done louder. Movies are usually much gentler than music.

But, if your system setup is calibrated correctly, I have a hard time imagining turning music up to +10 and wanting more. That is insanely loud. Either you're looking to feel like you're in the front row at a rock concert, your hearing is already gone, or you got something wrong. Seriously, that volume level should leave your ears ringing.

I don't know. It is hard to say without seeing/hearing it.

I agree, around -14 is a normal movie level for us as well, but for action movies when we're in the mood for excitement we'll go louder.

Calibrated correctly, probably not. I'm not sure I know enough to get that right. I calibrated to the best of my ability though. I never turned it up to +10, around 0 was as high as I've gone and it was at this level that the amp shut off. Your exactly correct in saying "front row at a rock concert". That's almost where it was at, but not quite, and I was loving it...for a breif few seconds anyway. I'm probably not as elegant as some and occasionally like to put on some heavy metal and rock out. With the amp at 0, the music started to get distorted and I am assuming it was most likely the amp being pushed too hard, not the speakers. If so, perhaps a new amp is in my future.

[cjd]

110dB is uncomfortable for more than a very short while - it's into dangerous territory. There's a chart if you scroll down here: http://en.wikipedia.org/wiki/Sound_pressure. A rock concert is probably pushing 115dB in the front row. OSHA says 15 minutes or less of that a day. NIOSH says zero (their 15min mark is at 100dB)

For that matter, I have pushed the system in my living room to 115dB and the RS28A is crossed at 1600Hz there It's past the point where I have any objective observations since my ears hurt and nothing sounds good, and I have to wear earplugs to do this. However, only occasionally do I find an RS28 bottoms out (they pop when the VC hits the back.) A pair of Emotiva XPA-1's (1000W+ into these speakers) so plenty of power. This system can get loud enough I can't listen for too long without the little lights on these amps dancing, so that should give you some sense of scale (perhaps.)

That amp appears like it should be pretty hard to push into protection mode, though its scaling to 6ohm isn't great at their ratings, so I'm guessing that's max not RMS. It's unclear if the power supply can deliver that much to the 3 front channels. Clearly, it didn't like how hard it was being pushed, which is unfortunate.

You wanted an XPA-3 anyway, right? Drive the front from an external amp, run surrounds off the Denon... Does the amp have adequate airflow?

On the other hand, the fact you kept cranking it and things only fell apart when the amp started hating things...

[gdub25]

Well, after talking with PartsExpress today, I decided to go ahead and buy 2 new RS150s and a new RS28 and put them in one of the cabinets. This will hopefully let me determine once and for all if the problem is the drivers. Still couldn't find anyone around that had an amplifier I could borrow. It will be a week or so before I get them, but I will post back with results.

So that explanation helped for sure, as well as the chart. And yes, I now want to buy an XPA-3.

As for the airflow of my current amp, I would say that it does have adequate airflow. It sits in a built-in cabinet but it has about 16 inches of space above it before the next shelf and nothing below it. It's the only thing in the shelving that produces any heat. It definitely got really hot when it shut off though, almost too hot for me to touch. I sniffed around and never did smell anything burnt.

[---k---]

Before you go adding the new drivers, do double and triple check your crossovers. Look for something that is miswired or anything that could be causing a short. I've read where people have killed an amp by not having the crossover wired correctly. And trust me, just because they sound good doesn't mean everything is wired correctly. I've showed up to CJD's before with a tweeter wired backwards. Its easy to make a mistake. A woofer tester comes in handy here to check to make sure everything is behaving as it should. ... but that is another $100, unless you can get JonW to ship you mine that he is currently borrowing. Might also want to double check driver polarity with a battery. Do the woofers together, then the mids together.

I'm throwing out everything that might make the load on the amp rougher or make you want to turn them up louder than needed. These are pretty efficient speakers and you appear to have a small to medium size room. Should be easy to get them loud.

Also,while you have everything opened up, might want to make sure you have good air flow around the mids. Your wall insulation looks like it might come real close to to the RS150s. I held the insulation back and then tampered it a little so that the mids had lots of room to breathe. Maybe even experiment with taking some out when you got all your other problems solved. This isn't related to your current problems. Just might help you fine tune the sound.

Good luck. Talk to JonW about the woofer tester. Just PM him, show him this as my authorization. He's a busy guy, but hopefully he can find time to drop it in the mail. You can then ship it back to me some day or to some other needy soul.

[gdub25]

---k---, thanks for the additional things to check. I have a couple days in a row off coming up in early Jan and will have time to devote to finding the problem. I'm making a list of things to check and will start eliminating them one by one. While I'm at it I may go ahead and post up the build log I've been meaning to do so you guys can see how I built the things and make any suggestions on things I may be able to improve upon.

I appreciate you offering the woofer tester. I may get ahold of JonW and see about getting it sent to me, but will wait until I get the drivers in and take the crossovers out for inspection to rule that possibility out.