Just by bad luck, your turntable may be sitting in an energy hotspot, despite your best efforts to avoid feedback. Sometimes moving the turntable a few feet from where it is sitting will make the difference. Trial and error. Re-positioning the speakers, by even a few inches, may help as well.
Feedback through turntable
My system consists of a McIntosh C2300 preamp, MC452 amp, MCD500 SACD player, VPI Aries 3D with Ortofon Cadenza MC cartridge, Manley ChinookSE phono stage, PS Audio P5, Sonus faber Cremona Auditor M speakers and REL B1 Sub bass system. My issue is with turntable use only; SACD has no issues. On my pre when volume is +55 (peak at 45watts) I start to get feedback through the turntable - a sort of low freq sound, back off volume and it goes away. My Auditor M speaker is about 3 ft away and in front of turntable. I do have a rumble filter (KAB) installed between preamp and phonostage to help with sub woofer pumping. Due to room layout I cannot rearrange the setup/move turntable. My turntable is on a 2.5" block of wood and that sits on 4 isolation blocks via spiked feet. Any thoughts how I can eliminate this problem? Harry Weisfeld with VPI states he has 4 15" woofers (JBL Everest) near his Prime Signature setup with no issues at all. Why am I having this problem and how can I eliminate it? Thank you in advance for all feedback.
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As lewm pointed out could very well be a room issue, If you walk around the room, even behind your speakers do you notice any exaggerated frequencies? Does the the issue arise even when not using the sub? Room treatments may be the solution or hold on to your hats adding another sub, as in "distributed bass" and room mode anomalies. |
@miner42, you are not isolating anything with rigid materials like brass cones and spiked feet. Once you realize that most of that is useless BS, you can start to look at real isolation methods. Browse through some industrial catalogs and look at how isolation feet are designed and what materials they use. See how sensitive lab equipment is isolated. http://www.newport.com/c/vibration-isolators |
rotaries is absolutely correct; cones and spikes are not isolators, they are couplers---at least, in the very low frequencies needed for turntable isolation. The idea that cones and spikes provide wideband isolation seems to be a deeply-entrenched misconception amongst hi-fi fanatics, one that persists in spite of overwhelming proof to the contrary. Cones and spikes DO provide some isolation above around 10Hz, but below that frequency couple, not decouple, two physical bodies (such as a table and the shelf/platform it is sitting upon). The Newport and MinusK isolation tables are state-of-the-art (providing deep isolation to at least 2Hz), but rather expensive (over $2000). A cheaper, and admittedly less effective, method of achieving isolation is with a combination of lateral and vertical decouplers---roller bearings for the former, air springs (or metal ones) for the latter. A mid-priced solution is the Townshend Audio Seismic products, available as single pods, platforms, and speaker stands. Audiogon member Folkfreak employs the Townshend Seismic products in his excellent system. |
Thank you to everyone who has contributed their thoughts. I will start by removing the cones and allowing the platform to sit directly on the isoblocks. I will also move the right speaker a bit at a time to see if I can eliminate those airborne vibrations. I think I know the answer but will ask anyway - would keeping my acrylic cover on during sessions help or hinder my issue? |
No cover. The cover itself will resonate, if the issue is airborne, and could make matters much worse. As a general rule of thumb, I would never ever use a cover during play. The stylus/LP interaction itself elicits vibrations that are best dissipated, not trapped under a cover. Having said that, try it. I am interested to know whether my negative feelings about covers are operative in this instance. I have five turntables and none of them has a cover except the Kenwood L07D, which has a clever lucite, LP-shaped cover that sits down over the spindle directly on the mat and not over the whole top surface. |
"Run longer speaker cables and move your source away from your speakers." No, I beg to differ. Run longer interconnects(balanced if possible) and keep your power amp only between the speakers. Keep speaker cables short. Don't go down this road until trying all the simpler solutions suggested first. Cheers, Spencer |
Having feed back issues and running the table with a cover is never a step in the right direction. I can't believe I needed to say that. Step back and look at where the problem begins the acoustic characteristics of your room and what you are adding to it. Start with implementing room treatments rather than applying this or that band-aid. The gains will far outweigh other options. |
Totem, You wrote, "Start with implementing room treatments rather than applying this or that band-aid." Isn't there an internal contradiction in that sentence? Some would classify room treatments as a bandaid. Not that there's anything wrong with that. The simplest first steps would be to make small changes in the positions of the speakers or the turntable, respectively, and determine what that does. Such experiments cost nothing. The OP has such plans afoot, I should hope. |
Some strange replies posted here. There is no harm in using a cover during play to see what the results will be, so why not experiment? As for standing waves, resonance etc., it is all very dependent on that particular system of components and materials, impossible to predict by anyone and I am sure most people giving advice here have never used a vibration analyzer, they just go by their perception. Try everything you can, experiment away:) |
You may find that seismic isolation can benefit airborne resonance issues too. Though only because it would allow the rest of the table to vibrate and dissipate the energy.. A cheap way to experiment is to use a small, partially inflated inner tube under the platform your TT is on. Simple and effective against some horizontal and many vertical vibrations. Though, if you've already ordered the springs, you may as well see how that goes. |
I feel the problem is airborne. not likely have you performed the audiophile dance yet to vet placement ? in order to give recommendations we need to know what your floor is and how it is supported. Wood floor with wood suspended beams, concrete pad, etc.... can you give some detail. stringreen how 'bout posting a youtube showing this ? |
CT0517, I have no dog in this fight, which is to say I am only guessing that the problem IS airborne. I certainly could be wrong, since my opinion is based only on the paragraph submitted by the OP. But can you say why you think the problem IS NOT airborne, with such conviction? Rotarius, There is no harm in trying the cover, I agree. But in general, I would never run any turntable with its dust cover in place. This is based on trying it both ways, over many decades and with several turntables. Could it help in this particular instance? Maybe. Anyway, trying the cover would tell us much about what is going on; if the cover makes a difference (for better or worse), the problem probably IS airborne. |
lewm - "not likely" means to me; other reasons are more likely and need to be explored. Until we have more info on his floor structure - its all guessing ********************************* Audiophile Dance. keep your turntable motor off. mute system at low volume. put on a record and lower the stylus on to the still record’s groove. unmute and start raising the volume level until it is at the high level for your listening habits. Start to Dance. any dance. jump up and down. Arm waving is optional. Do you hear anything through the speakers ? Dance around the table to determine if there is bad loading point. If all is quiet ..... that spot is ok. oh...before finishing..... try yelling at your cartridge (Baritone and Soprano voices) loud to determine if anything comes out of the speakers. |
lewm I guess it all comes down to the proverbial "chicken and the egg" If a room has particular issues ie modes that propagate and are not dealt with any amelioration down the chain is in my mind the "band-aid". In a studio or other professional venue the first thing that's considered is the room, since that will always be the limiting factor for whatever follows. Is the room in the OP's case the problem? The way to confirm is to run a sweep and determine where and why the anomalies are present. Personally the whole room treatment subject is one of the most overlooked and discounted topics considering its effect on whatever gear, tweaks or changes follow. Thats my take on it. |
Todd, the Townshend Seismic Platform (the "original" Seismic product, which I have and use, not the current "spring-in-a-bellows" Seismic Pod design) actually IS a slightly inflated inner tube inside a metal frame. The top and bottom damped metal platforms are separated by the inner tube, and it provides, as you say, a lot of vertical isolation. I then have roller bearings on top the platform for the lateral isolation they provide. The combination works real well. |
Todd, I learned of roller bearings from audiophile recording engineer Barry Diament, a leading proponent of them (using them under every piece of his gear, even his Maggie MG 3.7’s!). He had his own "cups" machined locally years ago, and on his website blog details their design. Contributors on his site have offered their homemade versions of the isolators, usually of very low cost with a corresponding reduction in effectiveness (due to the softness of the bearing cups, often of plastic, wood, or cheap pot metal). There have been a few professional/commercial companies making roller bearings over the years, most famously Symposium Acoustics with their Roller Block, it’s cups machined from aluminum. The Jr. model is the best deal, a trio of 1-7/8" double-cups with a half inch ball bearing between the upper and lower cup, priced at $180/set. The major difference between Diaments design and the Symposium Jr. is in the Jr’s use of top and bottom cups, in contrast to Diaments preference for a single cup, with the ball bearing itself in direct contact with the bottom of the component. There is a small company in Canada making two versions of a roller bearing, Ingress Audio Engineering. Their Model 2 is identical to the Symposium Jr, just without the Jr’s black anodized finish, priced at $120 for a set of three double-cups with ball bearings. They also offer their Model 3, made to Diaments specs, a single 1-7/8" Alcoa 7075 aluminum cup with a very large 2" diameter "bowl" machined into it. The gentler slope of the bowl resulting from it’s larger size results in the bearing having a lower resonant frequency, therefore possessing greater isolation properties. The cups are also polished to a smoother finish than are the Model 2. The Model 3 sells for $175 for a set of three cups and ball bearings. The Ingress email is ingressaudio@gmail.com, phone number (519)981-2031. |
Just to mention the roller bearing assemblies actually provide very good isolation in not only the horizontal plane (all horizontal directions) but also the three rotational directions - twist, roll and rock, as a consequence of the shallow cup and bearing motion when forced, which are also important since the seismic vibration produced by Earth crust motion, traffic, etc. arrives at the house or building in the form of waves, like waves on the ocean passing under a boat. My first product, the Nimbus Sub Hertz Platform, isolated in all six directions and had a resonant frequency as low as 0.5 Hz! |
My main listening room is on the second floor, carpeted on a suspended subfloor. I do not have the luxury of moving the sound system away from the speakers due purely to room size (15' x 15' x 8') and layout (open on two sides - second floor game/media room). I feel my table is shielded from mechanical vibrations. The VPI Aries 3D has the mini-HRX feet, this sits upon a 2.5" layered birch platform with a cork top which is on 4 isoblocks that sit on my marble-topped audio console. |
miner42, Did you ever try ct0517's dance tip? If you are embarrassed to dance, follow his directions without the dance. If you're getting the low frequency noise this way, something in your tt isolation chain is not set-up right or is not able to isolate effectively for your particular situation. What type of audio console are you using? |
If you haven't already watched the Townshend Audio YouTube video showing how a speaker on a concrete floor reacts to vibrations, you should. (bdp24 has talked about this in other threads). Then think about if a speaker on a concrete floor has this much vulnerability to vibrations, surely your tt on a second story will be magnified multiple times over. Food for thought. |
I have been to older audio friends homes where their children have left. (yeah right - will believe it when it happens to me) ......anyway. So the couple, find themselves with an empty bedroom/s upstairs; Usually (She) doesn’t want the stereo on the main floor. So usually (He) is forced to use one of the bedrooms upstairs. All wood suspended floors have the capability to produce what I call the 6 O’Clock train effect as bass and volume increases. And the higher you go 1-2-3 suspended floors, the worse the effect can get. All it takes is one of the full range speakers and or sub to be placed above one of the same horizontal beams, as the one the turntable stand sits on. They become joined at the hip - so to speak. As the volume increases, its like that 6 O clock train going by. A suspended floor is never an ideal spot for a resolving turntable. If the problem is bad enough and keeping you from enjoying your system at those levels that get the .....endorphins flowing..... then... locate the nearest main side wall that supports the house. Not that flimsy wood studded wall between rooms. Attach a shelf/ves to one of the main support walls. Another option - a little more extreme.... is to hang the shelf from the ceiling. 8^0 ************** then there is the other fellow, same suspended floors, that puts all the gear in one room except the speakers. The speakers go in the room next door. But guess what - they are still sharing the same horizontal wood beam - so - still joined at the hip ...... guess what happens.... thats right ..choooo. choooo !! some Sat morning funny |
@bdp24, @toddverrone, FIM made a ball n" cup device as well that was priced lower than the Symposium jr. Maybe still in production??? I almost offered one of my Symposium jr. sets up for sale, thought about it and decided to keep. They were offered w/ two levels of ball bearings, one of harder strength. (Tungsten)?? I took it one level further and acquired ceramic balls. My project at this time was my VPI HW-19 mk IV that i"d taken way out of stock. The ceramic ball bearings were a step up in this particular setting, adding major transparency... the highly resonant plinth/base of the VPI was HARD to overcome! |
You both may find this of interest.. I've fabricated a 3" maple platform that I've recessed 3 Symposium jr. (cups) into (flush) w/ the top of the platform.....on the bottom, I've a 1'8" recess for my Super Stiff Springs. An effective,versatile platform that can be used in various applications. I'm currently using it in my similarly modded rack that my amp/conditioner rests on. |
I wanted to tell miner42 that, while he had the upgraded feet for his tt, that in it's center is rubber! That is what connects, (forget that) Traps! the resonances by not allowing a freeflow of these vibrations! Rubber is not your friend! This is certainly not his main concern. It is, a valid point. There, I said it. |
Good stuff Slaw. I want to get rid of the last of the rubber in my system, the inner tubes in the original Seismic platforms. I have been planning on getting some of Geoffs springs, and perhaps some of the current Townshend Seismic Pods. I find the Pods more than a little overpriced, but what else is new?! I too had a VPI HW-19, and considered it about as good as a suspended-subchassis design could go. But you're right---that MDF platform was it's weakness. I never heard the later acrylic version, having moved on to the Townshend Rock table, which certainly doesn't have THAT problem! |
