[Mike-48]

I have hooked up a couple of subs in my system. The best feasible location so far is not far from the amplifier (FET Valve 400R). The amp is on an amp stand, which is on a small rug.  The subs are directly on the floor and have rubber feet. I don't play a lot of loud music, but I'm wondering if routine vibration from the subs is likely to cause problems for the tubes in the amplifier. Would it be useful to

• Put Sorbothane pads under the amp's feet?
• Find a way to move the amp further from the subs?
• Order extra tubes to have on hand?
• Not worry about it at all?

Thanks!
Mike

[/list]

[avahifi]

I assume the subs are active with their own built in plate amplifiers, correct?

I doubt very much if it would be possible to induce enough acoustic feedback into the Fet Valve 400R amplifier to be even close to audible, either airborne or surface transmitted.

The Fet Valve amplifiers pass the tap test here (tapping directly on the audio circuit boards while watching the scope for tube microphonics to show up on the scope).

Frank

[JonnyFive]

Are the subs on isolating pads?  Depending on what's underneath that room I'd recommend a Gramma isolation pad or similar to decouple them from the floor.  If you were worried about the amp you could get some Herbie's isolation, or even those black sorbothane feet you can put under a washing machine (but the residue will harm your wood floor, so be careful).

You're probably fine.

Jon

[NIGHTFALL1970]

Mike,
my sub is close to my 400R and I have never had a problem.  Can you hear anything?  If not, don't worry about it.

[Mike-48]

My thanks to Jon, Frank, & Nightfall for replies.

To answer some questions:  Yes, the subs have plate amps.  They also have quite good, compliant elastomeric feet.  No problem with noise below, because under the floor are concrete and dirt -- it's a basement.

I have noticed that the amp passes a tap test involving tapping the top plate lightly and listening for microphonics through the speakers. I've never heard a thing.

Again, thanks for the help. Reassuring!  I won't worry.

[mav52]

Why not spread the subs out

[Mike-48]

Why not spread the subs out

The room is a bit narrow, and it doesn't offer many practical positions for the subs. The current spot gives the best objective and subjective results yet, in smoothness of blend with the mains and smooth LF response.

[Wayner]

Placing subs between the front mains usually produces a "pressure ridge" that inhibits proper sound-staging, by blocking the HF from the mains. Moving the subs to the outside of the main speakers will help this situation and because you would be closer to the wall, would allow you to decrease the output of the subs, thereby reducing a possible induction of vibrations to the amp and other components, especially source components.......

[Vulcan00]

Hello Mike:

Sorry off the topic question. I was interested in your absorption layout behind the speakers particularly the corner rectangles stacked from floor to ceiling. Would you explain just what those corner traps are?

Thank You Sir

[Mike-48]

... I was interested in your absorption layout behind the speakers particularly the corner rectangles stacked from floor to ceiling. Would you explain just what those corner traps are?

Thanks for asking.  They are broadband bass traps, "Soffit Bass Traps" by GIK Acoustics.  http://tinyurl.com/lqzkdpv  The half-rounds are by ASC, ordered years ago for a previous room. The diffusers are made by Vicoustic. They are about half the price, or less, of similar ones from RPG.

I have all that stuff hanging from rails so I can move it around to find the best positions without making a lot of holes in the walls. The current setup is not bad, but I may experiment more some time.

Mike

[Carl V]

Nice set-up.
Like the other posters...
I'd be inclined to move those subs off to the side near the wall.
in front of the plane of the Jantzen speakers...near those
triangle traps on the floor. Perhaps one in front one in the rear.

Regardless, nice system & set-up ...enjoy.

[Mike-48]

Nice set-up.
Like the other posters...
I'd be inclined to move those subs off to the side near the wall.
in front of the plane of the Jantzen speakers...near those
triangle traps on the floor. Perhaps one in front one in the rear.

Regardless, nice system & set-up ...enjoy.

Thanks, Carl!  If you're in Portland some time, you can come over, and maybe together we can move two 115# subs around the room and do some critical listening. I just don't have it in me to do a lot of that by myself any more. In fact, I was going to sell them, but I found that in this room, they fill a real need.

About putting them outboard: I think that is a good idea, and I tried it a while ago. I was unable to get as good a blend with the mains as in the current spot.

The subs are running in stereo, and over the years, I've found it helps to place them symmetrically with the mains. It's been suggested that I try running them in mono, then I could place them front and back, as you suggested. Some day, I may try that, but for now, I'm happy with the results in stereo, and it does give a nice illusion of the ambiance in the recording space.

OK, I'd better stop gabbing about audio and get my work done. This is more enjoyable, though. Thanks again for the thoughts.

[aln]

A simple-and cheap thing to try is to put a set of ISOBLOCKS under the amp.  Mapleshade sells them as well as ebay.  They are a cork and rubber footer and work very well.  Nice system!

[Mike-48]

Thanks to aln for the Isoblock suggestion. If they are what I remember, they are quite cost effective. Good idea.

Also, thanks to Wayner and Carl V for suggesting to move the subs. I am beginning to find that center fill has decreased since I put them inboard. I'll try outboard again when I get the time and energy to wrestle with them.

Mike

[Wayner]

Mike,

It's not easy to find the right spot for a sub. I've wrestled with this from time to time myself. I try to make the sub be an extension to my existing speakers, taking over where their bass response drops off. I only have one sub, so my cross-over is low, to help keep the sub from becoming directional.

[rcag_ils]

I used the conventional method, put the sub in your listening position, crawl around and find a pot where the sub sound the best, then move the sub over there. This method works great. Needs a little compromise for aesthetic.