Using coach screws to defeat suspended wooden floor - a good support for hifi stands - Don Lodge

It's well known.  A lot of hifi buffs like to get things right. And even when things are right they like to try to get things better.  And there are may facts, myths, beliefs and fallacies connected with the subject, some of which are expounded on this Forum.

But it has been an accepted fact, that is no longer a fad, in the fraternity that what you stand your equipment makes nearly as much difference to the sound as what you paid for it.  Hifi stands of wood, glass, composite board and steel all have their disciples.  Usually these stands have some sort of adjustable spikes on the bottom to in some way conduct or dissipate vibrations to or from the floor.  (The same sort of argument applies to speaker stands).

But a floor is not a floor is not a floor.  There is no democracy amongst floors;  floors are not created equal.  It is recognised in the hifi press that solid concrete or stone floors can produce sonic benefits to speakers or equipment stood on them.  Old fashioned wooden floors can be fine, carpets and light coverings can be dodgy, and suspended wooden  or resin surfacing is a pain.

I have a suspended wooden floor in my listening room - modern enmeshing strips of wood pinned to older wooden boards with a plastic membrane between.  Almost the design specification for a primitive booming drum!

So I tried placing the feet of my Isoblue hifi rack on coins, steel discs, small tiles and  large slabs of stone.  All brought their sonic signature, just as when I replaced my glass and steel rack with the Isoblue stack the sound improved enormously. To wife-remarking levels.  Why transistor amplification can be so vulnerable to vibrations and microphonics remains a mystery:  but of its truth I am convinced.

Nothing proved really satisfactory.  Couple with this the fact that I have unwittingly developed a new slightly camp method of walking round this room while records are playing so not to cause the stylus to jump tracks.  It was becoming a liability.

I had to grasp the nettle and drill the suspended floor;  I reason that I am not going to move the hifi from its present position, and four small holes could be filled with wood or filler in the future.  Better than living with this frustration/no hifi/stripping out the lovely floor/running away to find a rich widow with better hifi.  So off I went to my local DIY superstore and bought four M8 coach-screws about 50 mm or so long.  The screws have hexagonal heads and can be spannered into wood or rawl-plugged holes in masonry. They look like this:

To do what I did, do this:

1) Unplug and remove all equipment from the hifi rack.
2) Decide where you want the rack to stay for ever....  No, seriously this time.
3) Place the rack on your nice wooden floor with no coins or protection underneath the spikes.
4) Not wishing to sound like a hooker at the bar, but must now lean heavily on your rack.
5) Move your hifi rack right out of the way - now you know where to drill holes in your floor because you have centre-punched dimples already in exactly the correct position.
6) This is where you need to get a decent sized electric drill, some bits, and courage.
7) Firstly select a wood drill of the correct diameter for the coach screw to bite tightly into.  Test on another piece of wood if necessary.  And drill your four holes.
8) Now you could pop in the coach bolts, tighten them home, and effectively be securing the top floor very firmly to the under floor in those four important places.  I tried this at first.  Things did improve - the soundstage became much firmer, image tighter (insert your own hifi magazine hyperbole here.)  But I still had to walk around lightly to avoid stylus jumps.

I went away and thought some more.  What I really needed to do was to give the hifi stand a firm grounding and leave the suspended uncoupled and free to bounce around.  I also assumed that any vibrational feedback the speakers were inducing (by being stood on the suspended floor) would be stopped also.

9) So more drilling.  Find a wood drill wider than the shank of the coach screw - so that when it is screwed in place it does not touch the sides.  Take great care when making these enlarged holes - the drill will snatch at the smaller central hole already drilled and rush through leaving you with a hole too wide to screw the bolt into.  The easiest way to overcome this is to put your electric drill into reverse - just lean on it gently and it will still cut through the top layer without too much objection.
10)  If you are lucky you will have caught a wooden under-joist in the course of your drillings - use longer bolts here for even more stability.  If you are unlucky you will have caught electricity/gas/water utilities.  Best consider this before you start otherwise consider earlier option of moving/rich widow.  If you find that your wooden underfloor is stone after all, just use a masonry drill and push a rawlplug down below the new suspended flooring.
11) When you have the four screws in place - do not overtighten to the point when the screw head touches the suspended flooring - go off and get a hammer, as drill bit (about 1/8th inch) suitable for drilling steel, a soft pencil and a centre punch.
12) Sit your hifi rack on the heads of the coachbolts - introduce it briefly to its new home.  Move it to the centre of the bolts as far as possible.  No, the points do not all match perfectly centrally on all the bolts;  just be thankful it sits on them at all.
13) With the pencil mark round the tips of the spikes on the heads of the screws.  Remove the hifi rack.
14) With the hammer and centre punch mark dimples in heads of the screws.
15) With the drill and metal drill bit make these dimples larger and about the same size.  This gives the spikes of the rack something a little bit more substantial to rest in.
16) Vac up the dust, clean floor, remove all tools, replace rack, level it using a spirit level if you are using a turntable, reinstall all equipment and listen.
17)  Enjoy firmer bass, tighter stereo image, and being able to walk around your own front room in an unaffected way again.

Don Lodge November 2009