[dkd7]

Now I want to speculate i'm getting acoustic feedback but not sure. Granted my TT isn't in the best location but i'm hoping there's a way to make it work, at least better than it is now. 

I experienced some odd speaker distortion that is believed to be rumble but given the placement of the components I think I need to isloate the TT better.

My TT is a 1200 Mk5 and I have changed the stock RCA's to 5' of Blue Jeans LC1. My Pre is a Yamaha CX-1000 and i'm using the same LC1 to feed the B&K 202. Given the layout of the room, i'm very limited to placement but in a pinch, I could possibly construct a shelf on the wall for the TT.

Should I remove the glass shelf the TT sits on and if so, what is the best material(s) to use to make another shelf? The rack is a Bell'O ATC-2101 and will support 50 lbs per shelf, lots of room for a heavy shelf.

Also, I have a hinged lid and it seems when closed provides better isolation than with opened, or at least less feedback. My cart is a Denon 301 Mk2 and I want to add, there is a top glass shelf above the TT as well. Attached is a pic of the setup, TT is on the top shelf.

All opinions welcomed, don't hold back.....thx.

[neobop]

Given the layout of the room, i'm very limited to placement but in a pinch, I could possibly construct a shelf on the wall for the TT.

Hi,
The 1200 is known for its isolation - immunity from feedback/rumble.  A wooden shelf and exotic feet or coupling might help, I don't know.  A wall shelf is a better solution IMO.  It could be high enough to keep little children away and still convenient. If you're constructing it yourself, you can get 20" brackets at home improvement.  Use long drywall screws and anchor it in the studs (normally 16" apart). First put up one bracket at height you want it, then hold the other bracket in place with the shelf and a level on top. Mark the screw holes on the second bracket.  It's better if you don't bolt down the shelf. Just lay it on top of the brackets w/o touching the wall.  Hope this helps.

[simoon]

I can't speak for the performance of your particular turntable, but bass is reinforced in corners. I can't tell for sure, but it looks like your TT is pretty much in the corner.

So, if your TT is susceptible to feedback, it will be more so in the corner.

3db per wall. That's 9db at bass frequencies.

[LM]

Also, I have a hinged lid and it seems when closed provides better isolation than with opened, or at least less feedback.

I have a similar deck and agree with neobop that these TTs are designed to be fairly immune from feedback, however there were a few things I did to minimise mine being directly in the firing line and these changes really did make a positive difference.  I'm not suggesting all (or any) will be practical for you particularly with your nice existing cabinet, however here goes.

Firstly, the lid.  I used to play mine closed as open it acted like a big ear lobe catching the sound waves and there was noticeable feedback.  After some experimentation with tapping the lid, plinth and other parts of the TT, I found there was a further worthwhile improvement by removing the lid entirely whilst playing.  It may not be practical for you but on an open top shelf, this takes 2 seconds and of course the lid goes back on as a dust cover when finished.  Big difference.

Secondly, as simoon says, there are better and worse places to locate a TT.  I originally had it (and my previous suspended TT) on top of a corner cabinet (containing my electronics) rather like your situation but found it best when I moved the Technics to a rock solid shelf further away from the corner.  Big, in fact very big, difference again after just a few minutes to find the best place.

Finally fitted Isonoe feet.  A very nice if relatively small improvement and simply icing on the cake seeing I did this last.  Well worth it to me for a final refinement but they cost whereas the first two changes did not whilst giving by far the most improvement overall.

By the way, I also had a KAB damper fitted whilst still on the original cabinet and whilst not directly made to mitigate such feedback, I'm sure it probably helps too.  Anyway, bottom line is that my set up with the above refinements sounds really clean now and a big improvement on day 1.

[dkd7]

I will try pulling the lid and note the changes, since it has been in the rack, it has been hinged.

When I tap on the TT, there is barely any, if none at all, feedback through the speakers. When I lightly tap the glass shelf it sits on...the speakers really thump, same as the lid.

While this may not be directly related, it's what made me research any noise issues. This is the vid I took of the speakers at a decent listening level....maybe 10 O'clock on the dial, Distortion begins at :19 I reduced the volume at :30

http://www.youtube.com/watch?v=veToMx-9BqI

[LM]

Not nice, I couldn't live with that.   Sounds like the shelf/TT location might be your primary issue rather than the lid.  I'd be trying some temporary relocation sites such as a small solid furniture item to act as a TT shelf and investigate further.  Best of luck.

[neobop]

You're getting feedback.  Woofer pumping is caused by subsonic signals being sent to the speakers.  This is not good. Long term or high excursion pumping can damage the speakers and it sounds bad.  An immediate fix for pumping might be a subsonic filter.  This is a band-aid approach but it should help. IMO you need to relocate the table to a more suitable location. See my first post for best solution.  If you need slightly longer cables it should be OK.  Your cart is a MC and is immune to capacitance affects + you're using Blue Jeans, but very long (like 15 or 20') are never recommended. 

I know this seems like a PIA, but you'll be rewarded for you efforts.  You have a nice table and cartridge.  The 1200 is a stable platform and the 301 is a good cart.  I think your best solution is getting it out of the rack.  You'll be amazed at improvement in sound.  The chance for this kind of improvement by fixing the shelf in the rack, is slim.  There are pre-made TT shelves available, or end table types are sometimes used.

[dkd7]

Would mounting the TT along the right wall, still near the speakers pose any threats? I believe there is enough cable to get it there and possibly even behind the equipment but i'm thinking behind would inherit even more noise.

The cables are soldered to the the IC board of the TT but I could possibly add lengths through another female/male connection and I don't think it would really add much, if any resistance that's even noticeable if only a couple feet.

The Yamaha CX-1000 does have a subsonic filter but i'm sure there are other options since it apparently needs more filtering. Can I add another SH filter in conjunction and if so what brands are recommended?

[neobop]

Along the right wall in front of the rack should be good. It might be a little tricky positioning everything so the cables reach.  I think it can be done if the table is slightly lower than it is now, closer to the height of the preamp.  Another option is to mount the pre under the table and angle it so you can use the remote.  That one might be messy with all the other cables, but if your shelf is 20" or a little more you could put it sideways facing the couch.

There should be a stud by that electrical outlet in front of the rack?  Perhaps you could figure most of it out in advance. You could move the rack a little forward or back to accommodate the TT shelf.  It's important IMO to use the studs.  If you're going DIY those 20" brackets have steel braces going from corner to corner.  They're very sturdy but those braces can block the remote, well, make it awkward anyway.  There's quite a bit to consider. You have to be able to get into the rack, use the remote and keep the table close.  Do you have glass doors on the rack?  The cables should probably come in from the front.  Did I mention this is a PIA?  It's worth it.  If you do this right, it will sound like a million.

You'll probably get other opinions, but I think you'll be OK if you have to add a foot or 2 of cable.  I've done it with shorter cables with no apparent degradation.  Make sure you get high quality cables that make a good and tight connection.  Avoid this if possible, but the benefits of relocating far outweigh any possible degradation IMO.

By all means, use your filter until you move the table.  If you're going to move the table don't waste your money on other filters.  In fact, you should check out the new set-up w/o the filter. I'm thinking you'll no longer need it. Once the wound has healed, you don't need band-aids.

[dkd7]

I will figure out the best mounting position and create a preliminary shelf, I can make it more asthetically pleasing later. Just to explore another option, and I can't think that it will match a shelf in terms of isolation....but what about a heavy stand with spiked feet?

I think that being heavy will ensure it will remain level, I will place it on the same right wall but will being about 2' above the floor still keep it susceptible to noise issues? Just an idea but I can build it with whatever materials that are designed for this application also the floor is concrete...not sure if that will create any issues with spiked feet.

[neobop]

A heavy spiked stand will usually work better on concrete floors.  With wood floors it's easier to get great results with wall shelves.  Wood floors act like a spring and a heavy spiked stand will move with the floor. It's not unusual to have footfalls upset tracking with such a set-up.  A wall shelf mounted on the studs is coupled to the beams/foundation and tends to be more immune to floor movement. 

Spikes concentrate weight like a high heeled shoe leaving indentations on linoleum.  This is called mass coupling.  Another technique is decoupling.  This is when you have a shelf usually, on spikes facing points up. There is also damping with specially made shock absorbing feet.  If you have a floor stand, you'll probably have to experiment.  If you have wood floors, you're more likely to get good results using the wall, w/o as much fussing.  There are a couple of past threads that discuss fine points of stand mounted tables, if you're going that route. 

[dlaloum]

Issues of isolation are complex, and the number of possible permutations and combinations of tweaks, platforms, stands, isolators, spikes, etc.... makes it very very difficult to work through and get a good solution without spending months on it...

Here is how I worked through the issues in my system
http://www.audiocircle.com/index.php?topic=106067.0

[cheap-Jack]

Hi.

Is it for BOTH audio & home theaure?

If you go much more for movies with yr family than audio, then leave as it is.

BUT but if you go more for audio, what the picure showed me is NO no good acoustically.

c-J

[Minn Mark]

Do you have an alternate cartridge  to try? I'm wondering if the Denon, or some other component in the TT signal path has become microphonic in some way, and so is now picking up noise?  just a thought...

Good hunting !

M

[neobop]

I will try pulling the lid and note the changes, since it has been in the rack, it has been hinged.

When I tap on the TT, there is barely any, if none at all, feedback through the speakers. When I lightly tap the glass shelf it sits on...the speakers really thump, same as the lid.

While this may not be directly related, it's what made me research any noise issues. This is the vid I took of the speakers at a decent listening level....maybe 10 O'clock on the dial, Distortion begins at :19 I reduced the volume at :30

http://www.youtube.com/watch?v=veToMx-9BqI

I think the problem is pretty clear.  That looks like 2 mid/woofers and a passive radiator. The M/Ws are trying to jump out of their baskets and the mids get very distorted. 

Putting TTs on/in a rack is notorious for possible problems.  Assuming Dkd7 doesn't have the option for a dedicated listening room at this time, I believe he has one of two options, wall shelf or stand. 

Dk,
If you want to try a stand, maybe you could copy Davids and tweak it for your situation.  His was developed for his system/space and it's no doubt very different.  There's also no guarantee with a wall shelf.  Some walls are flimsy and either one might have proximity issues because of your rack location and need to keep it close. From the picture, it doesn't look like you might have much of a choice.  If you could move the rack and table away from the speakers, that might help immensely.  Don't be discouraged.  Even if your set-up isn't ideal, few are.  I really think that with some effort you can get the woofers to stop pumping and enjoy your records much more. 

[dkd7]

Hi. Is it for BOTH audio & home theatre?

Yeah, pretty much...however the HT aspect of it has been reduced slightly as I have biased the setup more for 2ch listening.  Once I get the speaker placement and treatments dialed in more then I will try to readapt more of the HT components. The center is disconnected as is the AVR, only using a 2CH amp currently, the SDA's do a wonderful job of providing a wide soundstage which currently keeps the center channel less of a necessity, but still needed down the road.

Do you have an alternate cartridge  to try?

I have a DL-110 but with a case of dumb-thumbs, I bent the cantilever while closing the guard. It works but I don't want to risk damaging any vinyl....may try it on an old LP. With how sensitive the glass stand it sits on now, i'm sure that's the bulk of the problem, it's literally a microphone when I tap on the shelf.

Dk,
If you want to try a stand, maybe you could copy Davids and tweak it for your situation.  His was developed for his system/space and it's no doubt very different.  There's also no guarantee with a wall shelf.  Some walls are flimsy and either one might have proximity issues because of your rack location and need to keep it close. From the picture, it doesn't look like you might have much of a choice.  If you could move the rack and table away from the speakers, that might help immensely.  Don't be discouraged.  Even if your set-up isn't ideal, few are.  I really think that with some effort you can get the woofers to stop pumping and enjoy your records much more.

I think I will try a stand first and i'm looking at a granite top, about 1-1/4" thick.....just tough choosing a pattern.

I think I can tuck the stand in behind the first reflection but that may or not be an issue. The room is less than ideal for critical listening so it will surely involve some tweaks.

[dlaloum]

An open frame stand is good as there are no panels to reverberate!

The single biggest improvement in my case was the 36kg concrete paver sitting on sorbothane pads.

But then my biggest problem was vibrations transferred via the floor...

Still a massive paver (costing all of $10) and some sorbothane pads provides a base platform with a very low resonant frequency.... makes it very inert - and a good place to start from!

Then add an open frame stand, and use spikes to sit it on the concrete slab (so it becomes a single item so to speak).
Then you can see whether more isolation is required at the next level...

The beauty of the concrete slab/sorbothane and Ikea Lack table, is the whole setup is dirt cheap.
Not much to lose if it bombs - lots to gain if it works! 

[cheap-Jack]

Hi.

Hi.

Is it for BOTH audio & home theaure?

If you go much more for movies with yr family than audio, then leave as it is.

BUT but if you go more for audio, what the picure showed me is NO no good acoustically.

c-J

YOU did NOT reply to my above question so that I give you an effective solution.

IF you are really serious to get it sound right, you NEED to go for a major re-location of yr TV & audio stuff. Any minor tweaking, like taking away the TT lid, etc etc, would NOT change the sound picture.

YOU only waste yr time acoustically..

c-J

[dkd7]

Hi.YOU did NOT reply to my above question

I did.

Quite thoroughly I thought.

[/mp]

Corner location bad. However, in front of speaker also bad. Try a few ine*pensive tests before marring wall. Also, 3db loss of signal to noise per junction. Recommend avoiding TT to Pre e*tentions if at all possible. Go with TT in same rack as Pre or on wall mount shelf above rack. Rack can always rotate to face desired direction (e.g. best reception of remote control signal).

Suggest following free/very cheap mechanical isolation tests:
Remove lid entirely while playing; use it only as dust cover.

Airborne vibration isolation: Styrofoam sound shield; one of those largish ultra cheap Styrofoam coolers should be adequate for Mk.1 test. Set Styrofoam cooler on TT shelve open end facing forward & TT inside cooler, rack in current location. Styrofoam will partially isolate TT from sound waves reinforced from corner location. (N.B. Inside open faced bo* bad in principal as it increases reflected sound inside of bo*; however, Styrofoam sufficiently acoustically dead material, unlike hard plastic dust lid, that it should be adequate for this purpose.)

Floorborne vibration test: Squash ball & board subshelf. Slice 2 squash balls in half. Spread out 3 rubber half spheres on current TT shelf, c. shelf sized board on on rubber half spheres & TT on board. Rack in current location. TT subshelf will partially isolate TT from floorborne & airborne sound waves vibrating rack.

Repeat tests with rack in location other than corner. (May require longer speaker wire.) Suggest rack, or at least open side of cooler face away from speakers.

If tests show promise, follow up with pricing foam bass absorbing acoustic tiles. Foam can be layered under cloth tapestry/drapery for higher wife acceptance factor.   

Good luck & Happy listening,
Mark
/mp