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petea
31-07-2010, 15:01
Hi All,

I thought you might be interested in the outcome of a series of experiments that a friend and I performed the other evening. As I mentioned in my 'Hello" post, my system has just come back out of storage and been added to somewhat. The house in the UK is a 17th century cottage and nothing is straight and level and the living room presents some problems to ideal placement. To fit the system in requires a custom-made stand / cabinet and the purpose of the experiments was to start looking at what materials to employ that would suit it. At present the unit is housed in an off-the-shelf 'Hi-Fi' cabinet made of Ash bought just to get things off the floor and tidied away (the pictures of this are in the gallery). It's not big enough but is does for now for CD play-back.

I know that many of you will have done similar experiments and, based on what I have read elsewhere, will have come to similar conclusions. My friend is an ex-BBC broadcast engineer and is (was) a tweak sceptic! All of the experiments were confined to amplification stages. We were using the opening 2 tracks of Don Juan's Reckless Daughter by Joni Mitchell and a variety of tracks from Leave Your Sleep by Nathalie Merchant (especially Peppery Man) plus some Paul Simon (50 ways...) as test tracks. The objective originally was in part to look to extend the bass slightly and the 'speed' of instruments such as kick drums (pending new mains cables - on order) as well as to explore materials for use in the cabinet.

First experiment involved Sorbothane pads (20 mm thick x 40 x 40 mm) under the power amplifiers (Meridian 205's). Massive increase in bass. Nothing subtle here and the reason that my friend is an ex sceptic (from the first notes played). However, staging and detail were highly compromised. Second experiment placed the Sorbothane under the pre-amplifier (Onix OA31 - using OA 401 as PS). Smaller bass lift than with power amplifiers but the same loss of focus and detail (the same occurred when we popped them under the speakers at the end of the evening). The effect of putting them under the PS was minimal but I would assume that this would be quite different if we were using it as a power amplifier. Sorbothane had no impact at all either under the Isotek Sigmas or when placed between the top of a piece of equipment and a heavy, heat-treated sheet of glass (we were using these to add compression to the Sorbothane as this is reputedly important to getting it to perform well - either is isn't or we did not apply enough load, or the material was too thick to load to a significant degree). So Sorbothane looks like it is out of the design unless it exhibits remarkable properties under source equipment (I used to use them under my Meridian 206B in the past) although I might revisit thinner sheet material with and without compression. One interesting side-effect of the pre-amplifier experiment was that detailing was improved by stacking the OA 401 on top of the OA 31 (we ended up stacking them at one point to save room and improve access). No effect resulted when their positions were reversed. My guess is that this is something to do with physical damping and I will explore this with weighted materials in the future - I see Onix-Addict has used a similar approach.

The next experiments were concerned with the material on which the pre and power amplifier were standing. We looked at either wood (25 mm thick Ash and 10 mm thick heat treated-glass). The sound from each was quite different with the glass producing a much drier sound that the wood. Musically, the wood suited the test tracks much better. A brief switch to rock suggested that the glass may have suited it better but the impact was markedly reduced. It seems a review I once read where they concluded (in an embarrassed tone) that kit supported on glass sounded glassier and on wood sounded woodier (and I would add that when on rubber it sounded more rubbery!!).

The next experiments will be confined to isolation spikes (wood and metal - hopefully of several designs) and acrylic isolation platforms in combination with wood (the final cabinet will almost certainly contain wood to fit the aesthetics of the room). I will start them once the new mains cables for amplifiers have arrived and have 'bedded in".

It is possible that I may have access to some highly sensitive micro-seimometers in the next few months. That would be interesting as I may be able to actually measure what it is that is causing the changes that can be heard.

Well, I hope you find this interesting and look forward to hearing any comments and suggestions.