LSIM 707 top end issue

stangman67

Looking for the speaker/crossover experts here to help me out.

I put my new phono amp into my stereo and think I have two issues, both intermittent unfortunately. I have a static/feedback sounding issue that follows an rca change from the output of the phono amp so I believe that is an issue with the phono itself.

When I first heard this feedback issue, I immediately turned off the phono which produced a very loud thump from the speakers. Since then I have intermittent crackling/cutting out of the right speaker midrange/tweeter regardless of the source. I switched left and right channels in the amplifier to check if it was an amp problem and the issue persists in the right channel regardless of config. It will not be present for a few songs and then come back for a few seconds and then will be fine for awhile again. Cannot create a situation that replicates the issue predictably.

Not really being an expert in the internal electronics of a speaker, is this more likely a crossover issue or did I blow both the midrange and tweeter? I would find it hard to believe they are blown since the issue is not present all the time but what do I know. Is there other tests I can perform to narrow it down? Unsure what the cost of a replacement crossover and tweeter and midrange is but I bet it ain't cheap and I am not sure I want to drop a bunch of money into a speaker I don't plan on keeping for awhile

Emlyn

May have been a grounding issue in the phono chain. I’d try completely disconnecting the turntable and phono pre from the system and just run a digital source to test the speakers. There should be no distortion to the speaker that way.

stangman67

I pulled them out of the circuit. It is two separate and distinct issues. The speaker issue constitutes cracking/distortion and muting of the top end of the frequency spectrum. Putting my ear next to the drivers, it seems to be present in both the midrange and the tweet. I don;t know the crossover layout of this particular speaker.

Maybe @VR3 can hop in and give some suggestions on how to go about troubleshooting the issue. I can certainly open things up if necessary and switch the crossover and/or tweet/midrange assembly from left to right and vice versa to see if I can figure out what component it is. I am a little weary of doing this as I don't want to hurt good components from the other speaker.

Open to suggestions. I would normally call the company, but we all know the black hole that is currently polk support

VR3

The way I trouble shoot issues like this, I have a fifty dollar integrated and a little hook up for my phone, this bypasses all of the gear and gets right to the speakers.

One you have narrowed down the speakers, hook your normal source to the integrated. Then a different source, repeat.

After ruling out the source, add your preamp back, going main out to the integrated inputs, etc. Then finally the amplifier.

Hope this helps

nooshinjohn

As far as the speaker issue is concerned... you likely have a slightly cooked voice coil. Call Polk CS and have them send a replacement.

stangman67

Great suggestion Trey, thanks! I am now using my 851N as a pre straight into the amp to rule out everything in the path and it has been playing like this for 30 minutes or so without issue. Will report back after a few hours playing. If it’s not the speaker, than I will be at a loss as switching the rcas from left to right on every component never moved the issue

Clipdat

Try to use the specific song that you originally heard the issue on. Sometimes blown drivers will only become evident with certain frequencies.

stangman67

I’ve done everything I can and I believe I’ve isolated the problem to the high freq crossover in the right speaker.

Additional steps taken. Check my logic please

1. Placed my 851N into preamp mode and connected directly to my B&K 200.7 amp. Problem still persisted in right speaker. This eliminates preamp and all associated wiring.

2. Since the left speaker has not exhibited the issue at all, I swapped left and right inputs at the amp end and problem persists in the right channel. This both eliminates the 851N (Especially since the issue persisted with both the 851n and turntable previously) and the amplifier

4. I swapped the mid/tweeter assemblies from my right speaker and 706c and problem persists in the right speaker. To me this indicates clearly the crossover is the issue.

Any objections?

Thanks,
Zach

pitdogg2

Pull the XO

stangman67

Here is the crossover. I don’t see anything that sticks out as a smoking gun but my eye is not calibrated to this

stangman67

I swapped crossovers between left and right speakers. Back to playing now. The problem better swap to the left speaker. Otherwise I have some black magic going on. Maybe the wiring at the terminal cup is a bit loose. That would be the next step for me I suppose

stangman67

Problem persists in the right speaker.

Bah humbug.

To wrap up. The right speaker has a different mid/tweeter in it and the crossover from the previously unaffected left speaker. The left speaker has the affected right speakers mid/tweet assembly and crossover and is now unaffected.

Next step is to pull the terminal cup and make sure everything is right there. Certainly seems like an intermittent connection problem. I guess I could swap speaker cables left and right on the off chance the speaker cable is flawed although I imagine that is highly highly unlikely

VR3

You have ran the speakers with all new gear correct, not the same source, etc

stangman67

I’ve done the best with what I have.

Only have the one amp at the moment, but it’s a 7 channel and have used three different channels on the right speaker to the same effect. Used the channel that has been powering the left speaker without any issues and problem persists.

I have used two different sources. The turntable and 851n through the Modwright preamp and associated wiring and both exhibited the issue. Right now have the 851n hooked directly to the amp and issue persists in right speaker regardless of what output of the 851n is sending signal to the right speaker. With the swapping of left and right, it’s the best I can do to narrow to the speaker.

I don’t have a third source to use

I removed the terminal plate and everything is right and solid as expected.

I guess the nuclear option here is to PHYSICALLY swap the left and right speakers and see what happens.

stangman67

The biggest issue here is it is so intermittent. Sometimes I have to wait an hour in between the symptoms so the troubleshooting effort is long and drawn out.

I unhooked the speaker wires and reconnected and swapped jumpers left to right and been playing for the last hour. I think I experienced a hint of the crackling/cutout but it was very quick and hasn’t happened again so I am not sure if I was imaging it

VR3

I can tell you with some certainty, if it is that intermittent, it is not the speakers.

Speakers just ain't that complicated

stangman67

Yea I agree with you. I just don’t know where else to go after this if it continues to persist. I guess I need to wait for my Modwright amp to come back to rule the amp out of the equation, I just don’t understand why the issue would only present to one speaker regardless of channel powering said speaker while the other speaker is completely unaffected

Anyone believe this could be the speaker cable? It’s an easy swap just haven’t done it yet

VR3

Have you tried cables? Could be a cable issue

stangman67

I’ve used three different sets of rca’s. If it persists I have a cheap pair of speaker cables downstairs in my wife’s vinyl setup that I will swap in.

stangman67

Silver lining in all of this is I have spent more time listening to my stereo over the past two than the past few months combined.

Also in between troubleshooting, I’ve managed to clean A LOT of vinyl!

The things we do for this hobby!