Well Bill, this is right up my alley, because I had 2 of the 3 different plinths you mentioned, right on my very own TT.
The acrylic base sounds nice, and looks very nice, but it is not even in the same ballpark with the wood/lead-shot base, sonically.
When I changed my plinth from acrylic to Cocobolo lead-shot weighted base, it was like I had gotten a totally new turntable. This was not a subtle change. It was very large, and probably the largest single change that has happened in my system.
First, the overall sound is just alot better in every way. The biggest things that you notice is that the bass response is a hell of alot better with the wood/shot base, and the detail is better, and the noise floor is better. So are the dynamics. The presentation is less harsh.
This is really a no contest issue. Any deaf person could hear this. It is not a debatable subject. Cocobolo with lead-shot weighting totally kills acrylic.
The plain hardwood base changes things based on how dense the wood is, and the cocobolo seems to be the winner in this category. It will do better than acrylic, and not as good as lead-shot weighted cocobolo. It kind of splits the difference.
There is a certain balance that must be achieved between a "Live" and "Dead" sound. Too much deadening, and it sounds dead. Too much liviliness, and it sounds too live(meaning harsh and in your face).
The issue of plinth materials has been a very big area of research in the Teres designs, and I can tell you that the upgrades in this area will give more sonic benefit than any other Teres upgrade. This is why I am promoting getting the wood/lead plinths at the beginning, instead of upgrading to it, if you can. It is a monster improvement, and has more impact on the sound than the weighted platter does.
My Michell has an aluminium plinth standing on plexiglass spider and weighed with lead masked with plastic for safety purposes. I placed an adjustable toes onto Walker disks also loaded with lead that dissipate even more of parasite resonance.
Overall the sound is detailed with clear midrange and musical.
Bass is almost botomless.
I believe that if I upgrade the power supply for VC I'll even benefit much more towards bass resolution and clarity.
This is a great question! And one that I had been curious about. Thanks for bringing it up!
And thanks to you, Twl (as ever) for your sharing your views and experiences.
I guess what im looking for is some kind of baseline. Its interesting to here that your lead massed cocobolo plinth is a significant improvement. But is this because of the wood or the lead? Is the lead shot in the plinth in a similar arraignment as in the platter, or is it loaded in a different way? As a wood worker my mind keeps coming around to the wood and its use in turntables. I look at Schroeder arms and his use of wood and am fascinated that this is his choice of materiel. Reading in another forum, Schroeder suggested that there was little difference(sonically) in the type of wood used in his arms and different types of wood were only used for there mass! This is very surprising to me as the difference in tap tone between cocobolo and say balsa (both used in Schroeder arms) is enormous. By the way if Shroeder arms sound ANYTHING!! like how they look they must be close to audio nirvana!! But i digress ...... So what is the biggest source of unwanted vibes in the plinth, the platter/ record vibes or the cartridge/ arm vibes?......
In the Teres, the base is shot-loaded differently than the platter. There are large holes drilled cross-wize and capped with the final sections of cocobolo after filling.
The answer to your question about which vibrations are more important to control, is "all of them". All the platter vibrations, or as much as possible, should be dissipated or channeled through the spindle and bearing and plinth to ground. In the cartridge/arm combo, the same is true. Dissipate or channel through the plinth to ground.
During the Teres project and beyond, many materials were tested for plinth usage. So far the Cocobolo and lead shot top the list. For your "baseline", the denser the wood, the better the use for the plinth. Whatever vibrations do survive the wood, are to be dissipated as heat in the microscopic movement of the lead shot. The lead shot also adds the needed mass for augmenting this style of turntable. It would be horrible on a Linn. Different designs need different things to help them work.
You first need to understand what is involved in turntable design, before you can address what types of vibrations to control, and where and how to control them. Not all design parameters are applicable to every design.
The function of the plinth is simple. It has to resist/absorb vibration, both airborne and from the ground and from within(for turntable with stand alone motor then the vibration is from the bearing only).
And common sense tell us the heavier and denser the plinth, the better. Also avoid any turntable with an empty cravity inside the plinth!
I used all of the above points to design my DIYer turntable's plinth. The plinth that I have is about 55lbs total with about 18lbs of sand and 2lbs of lead shot filled fully inside the cravity of the plinth. I use lead shot because of its high density. And sand is a very good medium to absorb/turn mini vibration(vibration from bearing, air or ground) to friction and then become harmless heat.
It takes high mass/density to combat vibration both from the air and from the ground and lead/sand to destroy them.
As for Twl, may be you should built yourself a bigger, denser and heavier plinth with sand/lead shot mixture filling the cravity. It will for sure have better performance than the stock Teres plinth.
Edle, I'm coupling my plinth with cones to a very heavy base with similar ideas you used in your plinth. The mass coupling to the base will provide similar results.
I'm glad you are DIYing with your TT. We need to see more of people like you, who are reaching out beyond the normal boundaries, and into the experimental world.
I realize that there are many variables in design and suspended is one that im not about to attack(build). In general im referring to the slab o plinth type of table. So if i understand right whether its a light or a heavy plinth the ideal material would be one that absorbs vibration without vibrating its self, and/ or transmits vibrations away from bering/ arm(one way) to another location?. Question ... can you induce sound to travel in one direction. Say with different layers of materiel with the most resonant being the farthest away(or some other arrangement)?
As for the mass issue i have a hard time believing that the more mass is better argument. All mass is not created equal. Some would absorb and some would reject sound. I believe how you use the mass is the most important thing. Also a 300 lbs. turntable is not an option!(for me at least)...... On the other hand ... anybody know were i can get my hands on a few hundred lbs. of depleted uranium? .. ; ) ...
All we are dealing here is physic. Very simple.
It takes high mass and density to combat vibration.
Of all the best turntable available now, the Rockport is 600lbs, the Walker is 300lbs??!!!. And there is a reason behind it.
Yes, depleted uranium is probably the best material. But it is hard to find and you might get radiation sickness or cancer from it!!!
But if I can find a way to seal the plinth completely. I think mercury is the next best material......
I am building a turntable now and using two pliths using Lexon(bulletproof plexy) I am going to fill with lead shot and try this. The platter will be of Lexon also(All 1" thick). Let you know later. Gets the parts back on Monday.
Bill, you pose a good question. There are some significant misconceptions about the resonant properties of different materials. Acrylic is NOT non-resonant at all. It does in fact have a significant low frequency resonance. When you tap on it there is a "bong" resonance that often is thought of as being dead. This is actually good and bad news. A low frequency resonance is much more benign and even can be a little euphonic, sounding warm. But it clearly does obscure detail and adds coloration. The bad news is that a low frequency resonance is nearly impossible to control. Adding damping helps little. The only way to effectively control a low frequency resonance is to add rigidity. Mass loading can easily make things worse.
Very hard, dense woods like cocobolo have a pronounced high frequency resonance. When you tap it is "pings". In spite of the resonance it sounds surprisingly good as is. Can't say that I understand why. Unlike acrylic a little lead completely eliminates the resonance. Tap on a lead loaded cocobolo base and it is really dead, as opposed to the "bong" that you get from acrylic. As TWL so generously has pointed out, the sound of a wood/lead base is significantly better.
I should also point out that I have tried lead loading an acrylic base. It does help a small amount. However, with a wood base adding the lead is a major transformation.
Metals, like wood are rigid with a high frequency resonance that is likewise easy to control. But for reasons unknown to me they don't sound all that good. I have tried using very well damped aluminum and steel. Steel usually sounded better than aluminum but neither were very satisfying. Clearly there are important factors other than simple resonance that are not understood, at least not by me.
I mostly agree with Edle's point that a heavier base is better. Just adding more mass is not a good idea. But if you add both mass and rigidity at the same time the results are very good. The upcoming Teres 340 has a 80 lb. base and does sound considerably better. However, it adds a lot of extra rigidity along with the mass.
Why not use ironwood? Very hard to work with but can be possibly better than cocobolo.
I rebuilt the plinth for my Well Tempered Classic out of Granite. 3 layers of 1.25 inch granite slabs that allowed me to preserve the WTC layered look totaling 3.75 inches thick and custom made (3) 2 inch diameter cone legs totaling at 132 pounds. It's dead quiet.
This forum encourages me to make a plinth out of solid slap 2x9x21 inch cocobolo. This plinth beats the VPI HW19 MK III badly. Then I added 15 lbs of lead to the plinth. This even provided tighter more defined bass, extended highs, more present mids, better focused image, darker back ground. I also used cork footing to reduce the sound echo from cocobolo material.
I would think that the best plinths would be be a high mass design composed of multiple materials with each having different vibration dampening characteristics. I don't know this for a fact, but such constrained layer designs work very well in loudspeaker cabinets and isolation shelves.
Nghiep, that's fascinating. Can you post some pix? It's good to see the DIY audio tradition thriving.
Your comparison seems to corroborate what Twl and Teres both heard. One question: have you tried a more rigid footing than cork? It would be interesting to hear you describe what a high quality set of spikes sounded like on your TT.
I guess it's time for me to get my 2 cents worth in this.
Check out the density and specific gravity of both ironwood & cocobolo. You might be surprised. Cocobolo is 1.1 & Ironwood is 1.07 density, according to my ref material. Here is a site that offers the specific gravities of some exotic hardwoods (but not ironwood):Righteous Woods
Remember, this info will vary greatly depending on where you get it.
Have you tried any solid surface materials for a plinth? I am using Staron on the next 3 I have going right now. it is 100% acrylic, but the additives they put in for color most definitely change the sonic character. Combined with lead loading, it could be very close to cocbolo. It seems to be the closest thing to acoustically inert that I have heard. I know you've done extensive materials research, just wondering about your results.
I too have the lead shot loaded base, that I built. I also have some macassar ebony in the plinth. The ebony is harder than the cocobolo. This breaks the waves as they pass through different materials. I loaded the shot top to bottom, not across. Same in the ebony armboard. I felt I could get a better balance that way, and the lead for each hole is PRECISELY measured. I also built the base like the 340, but mine only weighs about 40 pounds. i'm guessing my whole setup weighs over 100#, easy. and, I still have not built the new rack yet, that will weigh about 300# plus lead loading, and the 150# granite slab.
Cones are a must have. I tried mine with no cones under the base. No go. Sounded very flat. All of the new designs in the shop now have 2 sets of cones (you all know which cones we like, right?); One has cones under the plinth, but hidden in lead filled towers, and under the base. Should be interesting....
You are absolutely correct: "We need to see more of people like you, who are reaching out beyond the normal boundaries, and into the experimental world." After all, isn't that how Teres got started? If those who can, do, who knows what designs may happen. From $200 Home Depot tables to whatever, it keeps it interesting!
One thing that I am trying in this new batch is putting a sheet of copper over the top of the plinth. This should keep all interference away from the cartridge and arm tube. I'm trying to mix wood & Staron also. This is a bitch! but we'll have to see how it sounds. I have also tried a new cocobolo arm board on mine that is .8" thick, with cones under it, and a large handmade brass washer under the cones. This is still testing. I think there will be definite sonic differences using mixed materials. All it takes is time, money & testing. I just bought 2 more arms to make this a little easier, and am going to get a couple more cartridges too. Can't tell the diferrence if you don't use the same arm/cartridge combo!
Jphii - I would love to see and hear those different models, especially if the arm and cart are the same. Incredible research! Here's a picture of my Corian based TT (and other stuff too):
I've seen your page before, and like what you've done. A man after my own heart! I will post some pics when I finish the new ones. Proprietary secrets and all that crap.....
Seriously, how can you tell if you're doing any good or not if you don't use the same stuff? I wanted to build or buy a TT for under 2k. That's how all this "nonsense" got started. A lot of Agoners gave me a lot of good advice. That's why I ended up doing this:My Teres1My Teres2
Now of course I've got the fever. SO, we'll see where it leads!
Dougdeacon, my theory is in the tuning of TT. Whatever materials of the TT, one has to tune it to sound right. The tuning of TT is also matching it with the rest of the system. The shape of the TT is for looks. I like to make mine simple and listen to it first then gradually tuning it. That was why I didn't load lead first so I know how much improvement. Even with lead loading, one has to experiement with the location of the lead and how much. This lead loading may depend on the shape and size of the plinth. I am still experiment with the sizes and shape of the plinth. I am getting more cocobolo for my plinth. It's been fun experimenting.
My sport model Rockport uses two 1" pieces of black plexiglas separated by 1/8" of EAR material and has 1/2" of aluminum on the bottom of the sandwich.....The whole mess is screwed together and floats on active air isolaters.......This is very dead and fairly cheap to build.....I have always liked it better than the System II Sirius as found the granite to be brighter than necessary........