Lets call your phenonomen "acoustic breakthrough" instead of feedback. You also have a rumble problem. This is not unusual with less expensive lightweight turntables.See if the problem is worse with your speakers closer to the TT and less so when further away.If so, them you will have to find some means to isolate the TT from the speakers as well as to see if lubrication can reduce the rumble. Don't try to hide the problems with a filter until you reduce them by other means. You may also at some point try to isolate the speakers from the floor.
Strange turntable/speaker issue
OK, this is going to be lengthy, but here goes....
I have a feeling someone else has experienced this, and want to get some advice in how to correct this issue.
Some background; I could not keep myself from wondering just how good the old vinyl I had boxed up for years would sound compared to my digital set-up, which sounds pretty good to me right now. But, out of curiosity, I finally dragged up my old turntable that has been stored in my basement for 15 years (since I moved in), and probably have not used it in at least 25-30 years total. Originally purchased in the mid 70’s, it is a basic Kenwood KD-2055 with the heavy composite ‘granite’ base. After getting it set-up, I realized very quickly the old Ortofon OM 5E cartridge I installed in the mid-80’s was not going to ‘cut it’, and could not compete with my CD’s, files, or streaming set-up. So, after doing a bit of research, and not knowing yet if going back to some vinyl listening would stick, I purchased a Grado Premier Red, mounted it in the shell, set it up, and yes, it is a vast improvement. Much better overall dynamic range, soundstage, imaging, etc. than the Ortofon 5E. I thought to myself, ‘this may just work’. But, as I was checking some things out, I realized my Vandersteen 2CE’s were actually moving quite a bit (volume was a bit high, but not overly so). That is no easy task. I got back behind the Vandy’s and the rear 10” acoustic coupler was actually moving in and out at a fairly rapid speed, thus causing the speakers to actually move on the anchor stands quite noticeably. Now, this was not really effecting the sound, or creating sound in and of itself, but it can’t be good. First thing I thought was I had misconnected the cartridge leads at the shell, so double checked, and they are connected as per the Grado instructions. BTW, this could have been happening with the old Ortofon as well, but I may not have noticed. Overall, while playing music, the turntable also seems highly sensitive to moving/walking around as the music was playing without distortion. I don’t have to tell you, this does not happen with CD’s or digital files.
I have my turntable on top of a pretty beefy steel frame with wood shelves 60” long ‘TV stand’, as yes, my system also acts as a ‘home theater’ setup, as well as a 2 channel set-up for music. The Vandy 2CE’s are my ‘front’ and 2 channel speakers driven separately by a B&K 125.2 power amp. The lowest shelf of this unit consists of CD storage, the middle shelf my B&K amp, Yamaha V871 receiver (I use as my pre in 2 channel, although it does little as the front channel pre-out’s go directly to the B&K, and while playing music I run in ‘pure direct’), CD player, and PS Audio DAC which all my CD’s, files, and streaming runs through. The top shelf is my TV, Elac center speaker, and my turntable. At this time I am using the Yamaha phono stage (that could change soon, as I think a dedicated phono pre-amp would help things a lot). The TV/equipment stand sits directly to the side of the right speaker, not between the Vandy’s, as they are on each side of my fireplace. The turntable is about 4 1/2’ from the right speaker, and right about the same level of the Vandy’s front 8” woofer.
So, all that said, I have a feeling what I am getting is sonic feedback between the speaker and turntable, perhaps with the cartridge acting as a microphone getting hit with the sound waves from the right speaker, even with the dust cover down. Because of room and layout constraints, I have very limited locations for all this stuff, so not sure a relocation of the turntable is really possible, and if I did, would have to get long male/female RCA interconnect extensions to get back to my Yamaha, or any future phono pre-amp, which would still have to run back to the Yamaha probably utilizing the analog Audio 2 inputs, as the Audio 1 inputs are serving the PS Audio DAC.
So, is sonic feedback what I am witnessing? Or could it be something else? And is there any easy solution? I doubt isolation feet will solve anything if feedback between the right speaker and turntable is the problem.
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The Kenwood is not a light weight turntable. Probably heavier than many in its pice class when manufactured. Again, that was it’s big selling points, the composition make-up and weight of the table. After a bit more searching for replacement feet, I’m thinking I may be looking for a solution in the reverse. In other words, perhaps the better solution is to get some type of Sorbo discs for the Vandy 2CE Sigs instead. As I have wood floors, I did not want to use the stock anchor stand spikes, nor carriage bolts as some use on wood floors. Instead I purchased, I believe, nylon disk furniture feet, made to allow for the moving of large furniture. Works great, but does not isolate the speakers from the floor at all. So, perhaps some type of sorbo discs under the furniture glide feet I installed would be an easier solution. Make it tougher to move the speakers, but not that hard to manage. I guess my concern there would be having the speakers ‘float’ to much. I believe the Vandy’s do like to be solidly sitting on the floor to perform best. From what I found doing some testing today, I don’t think filters are necessary. It’s in the physical set-up. |
bkeske, everything you did I could have told you ahead of time what would and did happen. So spare yourself more wasted effort- forget about sorbo under the speakers. All that will do is make them sound all sucky and dull and not do anything to help the turntable. Sorry but at least you are gaining experience. Simple proof of concept, if it was a problem of speakers transmitting vibration through the floor and then back up into the table, well then placing the table on the floor would have been worse not better. So its not the speakers. Not even going to get into all the misinformation about spikes and coupling and all that. Much easier if whatever you heard or think you know, just tell yourself its all wrong. Because it is. (Another proof of concept: If what you knew was right you wouldn’t be anywhere near doing what you’re doing. I mean, it hasn’t worked, has it? What did work? The floor. Just like I said. See?) The lightweight turntable story was not about yours, it was intended to learn. What you had (when new, before the suspension footers wore out) was similar to the Linn approach of light (relatively, trust me) and suspended. In all these things it comes down to a question of mass and resonance. Suspended tables like yours was (when new) are only really isolated from vibrations in the frequency range they are designed for. They are in effect tuned. A hard one for people to get. But now that suspension is shot which puts you back in the other camp, the school of mass/stiffness/damping. In that realm you get exactly the results you got- it works better just sitting flat on something solid. Wish I was there to eyeball it, whole lot easier. What I PROBABLY would do is make a sand box isolation platform. Cheap and easy yet really, really effective. Inch or so of sand, the more the better but more on that in a minute. Mixed with the right amount of mineral oil it has a beautiful consistency, almost like dry sand but slightly packable and dust-free. Tamped down you might be able to place the table directly on it. Or cut three or four MDF pads a few inches square and tamp them down level and place the table on that. Both my table and my phono stage are on something just like this. Could spend a lot and not do better. The trick to getting the most from this is getting the mass right. Look at my stand. http://www.theanalogdept.com/images/spp6_pics/C_miller_web/TTstand_1.jpg The red shelves are concrete. The gray slabs are granite. The black legs are ABS filled with concrete. Both the top and bottom shelves have about 1" of sand inside. It does move if you walk by. But it is so massive that when it does move (and it does sometimes, you can see it) it moves at a very slow sub-sonic rate. Not saying you need 800 lbs of sand and concrete and granite. Saying whatever amount (mass) you use will affect the harmonic frequency and hence degree of effect you get. Complete opposite direction of styrofoam, which I could have told you was the complete wrong direction to go. Proof of concept: find a tote or tub, pour in $2 worth of Home Depot kiddie sandbox sand, tamp it down, see how it goes. |
@millercarbon Thanks for the additional insight. I had a pretty good feeling the styrofoam, or large tiles, etc. would not work. What I wanted to see was if the material I tried had any effect at all. It did. I wanted to make sure it wasn’t just a ‘sonic feedback’ issue between the speaker and cart. As I say, what I found was that anything I put under the original feet made the problem worse, not better, nor more importantly, the same. Instead, the table became much more unstable sonically and made the rumble worse, especially with the styrofoam. That was incredibly bad, and the coupler was pulsating stronger than any other condition. I’m no expert in this, but I would think if the problem was primarily a sonic reaction between the speaker and table/cart, these physical base/feet changes would not have had the extreme results they did. After finding the failure of some of the original built-in feet isolation design, I had a pretty good idea this was more a physical than sonic problem. And that the sonic problems and instability are a result of the physical issues, not the other way around. I think. I must say, you have some seemingly odd ideas, but it may be worth a shot. I still have a bag of sand from filling my Vandy anchor stands, so that’s easy, if I can find something to put it in and test it. And yes, after thinking more about it, I don’t think I want to isolate the speakers at the feet. I think that will just degrade the speaker performance. |
Odd ideas. Good one. Made me chuckle. Thanks. You have much to learn, grasshopper. https://forum.audiogon.com/discussions/sandbox-style-isolation Between actually trying stuff however odd and trying to figure things out by reasoning alone I'll take trying stuff out any day. This site is chock full of the most horribly wrong ideas that sound good enough to have convinced people, almost always people who can't be bothered to actually check them out. So you're making mistakes but learning. Its the but learning part that counts. Good for you. Like I said these things are all tuned. What you got is like an old grandfather clock that wobbles. Can't keep good time because every time the pendulum swings it causes the whole clock to sway, the whole thing rocking back and forth. Your turntable is doing exactly that, only at a frequency and amplitude that makes it hard to see. But that's what's going on. That's why your experiments failed. What you did was just like putting styrofoam under the already wobbly clock. It only wobbles worse and more. Place that clock (or turntable) firmly in some nice packed down sand though, now its stuck. No more rocking. Remember though its not only the turntable that moves like this. The whole rack, or wherever else you put it, everything no matter what is going to oscillate. Its simply a question of how much and at what frequency. Why electron microscopes require specialized vibration control. What looks good at one scale is a nightmare at another. So on one scale you control the very fine low amplitude vibrations with the sand particles that shift against each other dissipating that vibration into heat. This requires only a fairly thin layer of sand. Mixing in oil actually helps keep the grains from packing solid while allowing them to shift microscopically, which is just what you want. But you also want stability on a larger scale, like the shifting vibrations of your old house. For this you want mass. The more mass the more energy it takes to make it move, or the smaller the movement for a given input. Most people just use as much as they have space and time and money for. But you could work it out mathematically if you know the dimensions of your rack and enough materials science and physics. So maybe not as odd an idea as it seemed at first glance. |
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