Hello HDT fans.
I have had plans to make some HDT's for quite some time but have watched the ongoing developements and changes to the HDT drivers and tunning so I held off.
Also, awhile ago I purchased a piece of 3/4" thick plate of what is known as "red brass" or commercial bronze (90% copper 10%zinc). It took a long time to find it (over a year) on EPay. I was hoping for "yellow brass" or what is known as "free machining" brass that is the gold color most know as brass. Nevertheless it is very difficult to find thick plate on the used market of substantial dimensions.
This piece is 45"x36" and my aim was to be able to yield several HDT top plates out of this material. As it turns out this large plate will only net 6 HDT top plates (13.5"x13.5") and many other small parts like feet or "pucks" as I would call them or other cylindrical parts like maybe knobs? This piece of metal is a "rosy golden" color and will polish up well.

My intent here is to ask if anyone is interested in having a set of these rather "HEFTY" HDT top plates cut out of this material? They would weigh around 45 lbs. each. Copper has, as some of you may know, one of the highest specific gravity numbers of all the non-exotic metals (around 550 lbs./cubic foot) and this plate is very inert and has little ring to it. Any softer thin plastic or rubber laminate on the underside would absolutley damp this metal to zero vibration in the critical frequencies. Asthetically they would be a nice touch not to mention the cabinet damping weight and energy retention (I am guessing here) the plate's weight would give the cabinet.

They would cost several hundred dollars/pair plus shipping. I am shopping price on water jet cutting and am at a price of $1 per inch right now. I would not finish them any more than a semi-coarse scuffing with a sander to get all the "haze" and patina off. They would have "hard" edges and any radius to the sharpe edges would have to be done by you. They would of course have the rounded corners as viewed from the top since the cutting operation would impart that important feature to mate with the HDT cabinet corners.

If there is not any interest I will have mine cut out and scrap the rest of the plate. It actually would net me more cash to scrap the entire plate right now and I will actually be spending money if others get the top plates with me, so this is not a money making proposal for me at all, but I wanted to offer the idea for consideration to you guys anyway.

Anyone interested?

Brad the plate I'm proposing is to add mass to the speaker and that it would be on top is a bonus. The weight further couples the cabinet to the floor and also damps vibration in the cabinet but is it audible? I don't know. The plate will for sure be an asthetic feature in my HDT build. It will be in conjunction with other metal "inlay" and corner capping that is also the same material.
I think that any weight in a speaker cabinet will improve its bass response and I've proven it time and again in my living room by adding 40 or 50 pounds to the top and hanging heavy items off the back of the enclosure on the inside of the speaker. Weight makes a difference. I did not intend to correct any vibration characteristic of the stock MDF top plate.
This is clearly a "splurge" idea and not a high payoff item in terms of improvement. It is not however a "more money than sense" idea either.
If you saw my plan you may like the look or not but it is a polished metal contrasted with fine wood veneer in a hard coat urethane finish that would be super durable and show the richness of the woodgrain and the metal finish.
Could also be a brushed finish to the metal.

BTW 3/4" thick copper alloy of any type is the ONLY metal or material of any kind/economy that could be used and still maintain under 1" of thickness like a stock HDT plate, that could add an instant 45 lbs. to the HDT and still have the identical form as and HDT top plate. It is the heaviest economical material to ad the most weight for the least amount of space taken and still be asthetically appealling. Other metals would be lead (UGLY), solid gold (twice as heavy but rediculously high price), solid silver (still rediculous use and price).

So again its asthetics, room coupling, and cabinet damping, in that order that I was aiming for.

I've thought about doing this just for asthetics, and because people (taking their lives into their own hands) place things on top of the speaker - so a more scratch proof material would be good.  I've thought about making fancy ones out of either granite (too much cutting and polishing work) or molding them out of concrete.  Not the boring concrete, the fancy stuff they make kitchen counter tops out of.  Anyway, I'll probably do neither because it's too much work.

Hello Chris,
If you've got enough material left over after you machine the top plates, I would consider also replacing the bottom plates with the brass. Brass top and bottom plates would help damp cabinet vibrations, and brass cones coupling the brass bottom plate to the floor would transfer most of whats left to the floor.

Just some food for thought.          :-*        ???

Cheers,               Bill

[quote author=RobLikesTubes  link=1148049244/0#7 date=1148150597]I made a custom stand for my gear with sand-filled Roman columns and a large rectangle of solid, beautiful polished  granite.(got  in a 'remnants’ yard'  at a local  quarry for $90.)

I  have  often thought about getting another matching  slab and  have HDT  plates  AND  bases cut.

I  think the  granite has  more  than enough mass, and would make a  perfect  aesthetic match to  my  stand  :)
[/quote]

Rob,
Rolled copper plate is 556 lbs. per cubic foot and zinc is 440 lbs. per cubic foot. At a 90% copper/10% zinc split red brass weighs in at 548 lbs. per cubic foot.
Solid granite is 168 lbs. per cubic foot.
So at 45 lbs. each for HDT top plates made out of 3/4" red brass (90/10 mix) even 1" thick solid granite HDT top would only weigh a paltry 18 lbs.

Now for something the size of your amp and equipment stand (VERY nice BTW ) granite top is plenty heavy and in fact a solid piece of copper alloy as big as what I see in your pictures of the stand would be so heavy 2 strong men would have trouble moving it or hoisting it by hand. It is extremely difficult to "manhandle" a monolithic slab of any metal over 80-100 lbs. and over 150" almost impossible for one person to control.

I agree for your HDTs the matching bases and top plate in granite would be nice. The most weight on top of the cabinet would have more benefit to damp cabinet vibration. At least thats my very humble opinion.
Do the granite though and match the equipment stand!