[daddydoom]

Hi all,

I'll see if I can explain my problem without sounding stupid. When I built my listening room I went ahead and made quite a few bass traps and reflecting panels. I know that it is over damped, but since my room is so small I thought it would be best. The room is basically dead. Which I have grown to like. It does suck out a lot of the upper frequencies at low volumes, but I rarely listen at low volumes. My problem is the bass. I thought all the absorption would cure any bass problems. I get a very low frequency rumble and or thumping on just select recordings. One of the recordings is the DSOTM. it doesn't matter what the media is vinyl or digital. It kind of sound like someone walking around on the floor above me or distant thunder. Volume of the music only affects the volume of the thumping. I think my speakers may be too big for my room.

I guess I will have to take out some of the panels to see what difference that will make, but wanted some opinions before I went to all that trouble.

Room specs:

   18' x 11' x 7.6
   The room is studio quality sound proof. I am a contractor by trade.
    My equipment:  VAC amp and pre with Wilson sofia 1's

Thx

Matt

[John Casler]

Hi Matt,

Does this occur with CD's. or Vinyl?

At first glance it sounds more like Turntable Rumble.

[srb]

Does this occur with CD's. or Vinyl?

                        ↓

it doesn't matter what the media is vinyl or digital.

[John Casler]

 

Obviously I shouldn't post right after rolling out of bed.   

[avahifi]

Pull your woofer grill covers and watch them with the system idling.  Do they show excessive low frequency motion?

If so, turn the system off and disconnect the interconnect cables from the preamp to the power amp at the power amp only.  Turn the amp back on, connected only to the speakers.  Does the excess LF motion remain?  If so you have a power amplifier problem.  If not, then you may have a preamp problem.

Advise us of the results of this test here.

Frank Van Alstine

[daddydoom]

Thanks for the replies,

John that was my first thought. That's when I started trying CD's too. It seems to happen at the same part of the album. cd or vinyl. The sound has no rhythm to it so I didn't think it was in the recording.

avahifi, I keep my covers off fulltime. have not noticed flutter in the woofers. The sound was there before I went to all tubes. Just not as noticeable. I just attributed it to the upgrade of the equipment. Btw, I did try what you suggested.
Do you think I should swap my tubes in the pre. I would have thought the room was the problem. Not the equipment. Luckily the tubes in the pre are a lot less expensive.

Matt

 

[Hipper]

You could also check each speaker. Either listen close to each one as the noise is played or disconnect each one in turn. If it's from one speaker obviously you can then see if swapping its input affects things to check its the speaker or further up the line.

Are you able to carry out any frequency measurements?

I also assume that it's nothing loose on the ceiling for example? Or windows etc..

[daddydoom]

Hipper,

Moved speaker wire around as suggested and found the sound is coming from left channel. So that eliminates a room acoustic problem.
Guess I need to move this thread over to tube-o-phile to find out which tubes I need to address. Thanks for helping me narrow down the problem.

Thx again

Matt

[avahifi]

Just swapping the speaker wires from channel to channel does not narrow the issue down to the preamp only.

Next swap the interconnect cables between the preamp and amp left to right (at one end only).  If the issue swaps channels again, it is a preamp issue, if it does not, it is an amplifier problem.

When you isolate the offending component, you can swap tubes in that unit from channel to channel to discover if the problem is following a tube.  Make sure you rebias the unit if that is required when you change tubes.

Frank

[daddydoom]

Will work on narrowing it down from here tonight. got to go and cut the grass before it gets dark. Will reply once I find the culprit.

Thx again

DD

[daddydoom]

Yep, it was the pre. Will work on swapping tubes today