Polk RT800i's weird music flutter/vibration

thejck

So I picked up some RT800i's on craigslist and a parasound A51 5 channel amp that will eventually go in my HT rig.
I hooked 2 channels of the amp to my RT800i's and was using my liteaudio dac and Halo P3 pre amp and listening to Seal's Love's divine. I am playing it as a flac file from my PC using optical out to the DAC using foobar and kernel streaming for bit-perfect.
Around 1:30s into the song there is a piece that has some thunder and some vibration and I hear this vibration coming from the speakers like it cannot handle the frequency. I tried swapping the channels and it seemed like the vibration moved over to the other side.
Any thoughts?
1. Are the speakers bad?
2. The amp is too powerful for the speakers?
3. The song file I have is messed up?
4. The speaker is just not built to handle this (a really low note)?

newsman

I never had RTi 800 bottom out like that and just vibrate. And I was running them full range for some time. Don't know what to say, try swapping out cables going to the amp to make sure it's not amp channel that is at fault.
Who knows maybe you found a resonant frequency for these speakers. But otherwise i would say RTi 800 are one of the best speakers Polk Audio have made.

thejck

I went though all 5 channels that the amp has and it was the same. i thought at first it was the one speaker but then when i swapped them i heard it on the other speaker too. maybe the flac file i was playing has a bad spot (i hope). I have some big rti12's that i will try to see what it does with the same setup.

thejck

Does anyone thing it could be a problem with the amp?

thejck

Another thought is that the speakers could have been driven hard by the previous owner would i see something like this typically if that was the case?

newsman

Blown drivers is a possibility. I had this happen on bran new Monitor Audio speaker. Also check to make sure all drivers a securely fastened to the cabinet/baffle.

Cpyder

Without more information, I can't say for sure, but I'm betting it's the source material. What your hearing is likely in the recording.

Edit: Are you saying that whatever speaker is on the right channel, for example, has the oddity?

thejck

yes actully it started with the speaker hooked to the left channel and then when i swapped channels it it moved to the speaker on the right channel. I did the swap before the amp stage so its not a problem with just one of the amp channels.
I was hoping it was the source.
I seriously doubt its the amp and the fact that it moved to the other speaker makes me hopeful that its not the speaker.