LSi25 Problem

xkepir2!

After a significant effort at trouble shooting, I have isolated a system issue to my left Polk LSi25 speaker. The speaker causes the amplifier to shut down at reference volume levels. The problem can be repeatably reproduced with specific passages of music and happens independent of the source component. All upstream components have been eliminated via repeated testing and swaps including connections/wiring.

I believe that there is a short somewhere in the speaker and it has to be with one or more of the following components: Mid-range drivers, tweeter, crossover, or associated wiring. I have taken the built-in subwoofer off line and the problem persists.

As my next step, I plan to pull each driver independently and check them with an ohm meter to see if I can isolate the problem.

I have two questions:

1. Is this a logical next step?
2. Has anyone else experienced this problem and if so how did you resolve it?

Component List
Marantz Pre-Amplifier AV7005
Carver Amplifier (Front Effects) TFM-15cb
Carver Amplifier (Rear Channels) TFM-15cb
Carver Amplifier (Center Channel) TFM-25
Carver Amplifier (Front Mains) TFM-25
SVS 13" Subwoofer System PC13-Ultra
Polk Audio Speaker Floor speaker; Built in subwoofer - 4 ohms LSi25
Polk Audio Speaker Floor speaker; Built in subwoofer - 4 ohms LSi25
Polk Audio Speakers Matching Center Speaker - 4 ohms LSiC
Polk Audio Speakers Surround Speakers - 4 ohms LSiFX
Polk Audio Speakers Front High Effects Speakers Rti28
Sony Blu-Ray Disc BDP-S780
Sony 55" Grand WEGA High Def TV KDF-55WF655
Belkin Home Theater Power Distribution PF60
Monster Power Home Theater Power Distribution HTS 5100
Dell Media Server Zino 410

jon s

swap the amps between the two speakers. See if the problem follows the amps. If so, the amp is the problem. If the problem remains on the same speaker, it probably is the crossover.

zane77

If this only happens at reference levels I doubt if you will be able to find this with an ohm meter. It sounds like a mechanical short in one of the drivers or a short caused when the voice coil is heated up with reference level power.

xkepir2!

I appreciate your input. But as I have stated in the original post ALL upstream components have been eliminated through that very method. What I need to know is what readings I should be seeing at the posts, the speakers terminals, etc.?

Update:
Right Speaker (Good Speaker)
Top midrange at 3.9 ohms
Tweeter at 3.0 ohms
Bottom midrange at 3.9 ohms
Reading on the posts with jumper to subwoofer disconnected at 34.1 ohms
Reading on the posts with jumper to subwoofer connected at 233.7 ohms
Reading on subwoofer posts at 233.7 ohms


Left Speaker (Suspect Speaker)
Top midrange at 3.9 ohms
Tweeter at 3.1 ohms
Bottom midrange at 3.9 ohms
Reading on the posts with jumper to subwoofer disconnected at 27.5 ohms
Reading on the posts with jumper to subwoofer connected at 233.4 ohms
Reading on subwoofer posts at 233.7 ohms

Thanks,
xkepir2!

xkepir2!

Zane77,

I agree with you on the mechanical problem. I do find it interesting that I am getting a different reading on the top posts. Any take on that?

Plus I thought that if there is a short in the driver that you will get a 0 ohms reading?

Thanks,
xkepir2!

dcjblvertec

Sounds to me like you have a dead short at your amp. Are you using bananna plugs or are you putting wire directly into your Outputs for this speaker. Have you swapped them left to right and gotten the same result?

mole'

any warranty still on the speakers??

xkepir2!

It turned out to be a fried crossover. I replaced it and life was good again.

However, I am starting to get discouraged with the Polks. Over the last 7 years, I have fried two different mid/woofer drivers, the above mentioned crosssover and now I have a bad mid/woofer on my LSiC center channel. My two channel speakers are Arum Cantus Vollas. They sound great and don't break.

BeefJerky

xkepir2! wrote: »

It turned out to be a fried crossover. I replaced it and life was good again.

However, I am starting to get discouraged with the Polks. Over the last 7 years, I have fried two different mid/woofer drivers, the above mentioned crosssover and now I have a bad mid/woofer on my LSiC center channel. My two channel speakers are Arum Cantus Vollas. They sound great and don't break.

If you're having that many bad drivers/crossovers, you need to look elsewhere for the problem. Either another component is bad, or you are overdriving your amp into clipping which can do damage to any speaker.

xkepir2!

I knew that someone would go right to the amps. Sorry, I run nothing but Carver TFMs refurbished by one of three guys in the world that know what they are doing with the amps. Very clean power and almost impossible to overdrive them at tolerable listening levels. Besides, I am using the same type of amp to power the Vollas at reference volume with no issue.

I think that the Polks are fragile. I am interested in knowing if anybody else has had issues with Polks.

Drenis

I know that Carver will push 350w at 4 ohms. The 25's are rated to 300 watts recommended max. Makes me wonder how hard you are pushing them. Sure they have gobs of power but do you think the LSi`s were designed to take 350w continuous all day? Better yet with all the headroom, how hot do you think that speaker gets after some listening time?

I can't comment on your listening habits nor am I insinuating that's the cause. But, I wouldn't rule out that you may have or may be exposing the 25's to that high power for too long of period and it's cooking things. It's a logical reason.

My speakers have seen over 500 watts, but not for constant amounts of time. Hell that's just way too loud at that point with 90db speakers.

BeefJerky

xkepir2! wrote: »

I knew that someone would go right to the amps. Sorry, I run nothing but Carver TFMs refurbished by one of three guys in the world that know what they are doing with the amps. Very clean power and almost impossible to overdrive them at tolerable listening levels. Besides, I am using the same type of amp to power the Vollas at reference volume with no issue.

I think that the Polks are fragile. I am interested in knowing if anybody else has had issues with Polks.

Not necessarily even the amps. Notice I said "another component" which could refer to things that are not amps. Seriously, if you are having that many problems with speakers, the problem is not the speakers IMO. I've only had one problem with Polks, and that was a couple of blown tweeters in some R150s. However, that was completely my fault since I literally fried the tweeter due to my own stupid error. Sorry, but I just don't see all the multitude of Polk speaker problems you are having being Polk's fault.

EndersShadow

xkepir2! wrote: »

I think that the Polks are fragile. I am interested in knowing if anybody else has had issues with Polks.

I am not and use a carver av-705x amp for my lsi 15s. I have a TFM-35 I am picking up next week that will be driving the lsi 15s and I expect no trouble.

How do you have the 25s wired?

pitdogg2

xkepir2! wrote: »

I knew that someone would go right to the amps. Sorry, I run nothing but Carver TFMs refurbished by one of three guys in the world that know what they are doing with the amps.

care to share who worked on them? The TFM25 can very easily be overdriven. Trust me I have TFM's and know them very well.

EndersShadow

^Any guess as to if its going to be Rita's, Rolland's or Vintage Hi-fi hehehe...

I am going to guess......... Rolland

Drenis

I'm glad there is a guy who repairs and services Carvers in my city! About 15 blocks from my house actually.

Enjoy that TFM Enders. Hope it's been serviced. If not, get'r done!

EndersShadow

Drenis wrote: »

Enjoy that TFM Enders. Hope it's been serviced. If not, get'r done!

Serviced 2 months ago at a local shop due to the right channel being totally out. New light meter lamps installed at the same time. Hopefully demo next week in my system to verify its working right...