Filtering Sub-sonic Frequencies

[gld1307]

Hi,

I changed my centre speakers on my 777 for some really good ones with the correct impedance. When I turn up the base beyond a certain level there is a subsonic vibration that feeds back through the tape machanism and then comes out throught the speakers, distorting the music program (i.e. making it sound wobbly). This does not happen with the original speakers, but the frequency repsonse for the original speakers is not very low (a wel known fact on this forum)

My question: Is there a simple piece of circuitry the filters sub-sonic frequencies that can be installed before the speakers in a simpilar way to a crossover? Some hi-end equipment has rumble filters for this but I believe they go into the pre-amps.

Cheers in advance guys.

 

[fins5]

I couldn't tell you about filtering circuitry, but I can say I haven't noticed anything like this with my modded GF-1000. All speakers replaced and no subsonics to be heard.

Hi,

I changed my centre speakers on my 777 for some really good ones with the correct impedance. When I turn up the base beyond a certain level there is a subsonic vibration that feeds back through the tape machanism and then comes out throught the speakers, distorting the music program (i.e. making it sound wobbly). This does not happen with the original speakers, but the frequency repsonse for the original speakers is not very low (a wel known fact on this forum)

My question: Is there a simple piece of circuitry the filters sub-sonic frequencies that can be installed before the speakers in a simpilar way to a crossover? Some hi-end equipment has rumble filters for this but I believe they go into the pre-amps.

Cheers in advance guys.

 

[gld1307]

Hmmm

Could be something specific with mine then.

Thanks for the feedback Fins5. That's useful to know.

 

[sony_apm_fan]

Sure, a high pass filter would work, 12db / octave.

So you have low frequency feedback from the speakers into the tape mechanism and back?

I have never heard of this, are you sure that the speakers are not being overdriven or the amp clipping? Can you isolate the tape deck to confirm?

Does it happen with any other source, ie line in?

 

[Jboogie2384]

I have a 767 and a 777 with different middle woofers and they both rock like all hell!! Might just be yours.

 

[gld1307]

It doesn't happen with the line in and doesn't happen when the original speakers are in.

Sony_apm_fan, when you say 'isolate the tape mechanism' what do you mean exactly?

The amp isn't overdriving; I don't tend to like distortion. I open it and tape a look again to see if there is some other vibration or resonance contributing to this. It is obviously something to do with my box. Knowing that nobody experiences this is valuable in itself.

Cheers guys!!

 

[sony_apm_fan]

Is it possible to loosen the tape mechanism whilst the feedback is occurring??

Didn't mean to (possibly) offend with the distortion comment, it sounds as though you know what you're hearing

 

[gld1307]

No offence taken at all. I don't quite know how I would be able to loose the tape machanism. I'll open it and see that everything is seated properly and tightened.

CHeers guys