It's about time I got spikes for my sub. It don't vibrate much cos its
such a heavy bugger, but coupling can only improve the sound, right? The
sub already has the inserts.

I've looked around. Richer have some for a fiver but out of stock, every
other site I try only has magic spikes for £35 or more.

And GOLD PLATED speaker *SPIKES*... man, who buys this stuff?!

--
Jim H

Jim Lesurf in uk.rec.audio:

First off, it doesn't decouple it from the floor, it more tightly
couples.

At low frequencies I would be inclined to agree.

There's also the matter of how sturdy the floor is. I'm not on the ground
floor, and this is a relatively new, relatively flimsy building. I'd
imagine there is at least less give in the floor than there is in the
carpet.

The spikes may have an effect. However I think it is not as clear-cut
as the proponents of 'spikes' tend to claim. Also if they *do* have an
effect, it might just as well be 'worse' rather than 'better',
depending upon the circumstances.

Since spikes use standard threads, maybe there is some non-hifi, spike-
shaped thing that'll screw in. I'll take a look down the diy shop.

If the spikes are cheap enough there may be no harm in trying them,
but perhaps being doubtful whilst doing so. You may end up with holes
in the carpet, though. :-)

Falcon accoustics have some here http://www.falcon-
acoustics.co.uk/pl28p9.htm for £2.60, acceptable cost for an experiment,
but I'm not sure I want to order from a company with, frankly, such an
amatuer website (sorry if anyone here works there etc). Anyone have
experiance in ordering from them?

--
Jim H

Jim Lesurf in uk.rec.audio:

In article , Arny Krueger
wrote:


My point with the fishing line example is that the box doesn't move
that much, especially compared to the cone. If the box were
suspended, the rule of equal and opposite reactions would hold. Then
motion of the box and the motion of the cone would be proportional to
their respective weights or masses.

If I *could* suspend the sub off the floor I'm sure the people downstairs
would be happy!

I agree with most of the above, but have a slight uncertainty about a
few points... :-)

I'd agree that the action and reaction forces will tend to be equal
and opposite (Newton). However although the movements of the box/floor
will be small in terms of amplitude compared with the speaker cone I
wonder about the radiation efficiency once the floor area is coupled
to the box. Although the displacements are small, the area moving may
be much larger than the area of the speaker cone. Hence I am not yet
sure that the sound levels radiated are simply in proportion with the
masses.

Another point is that the cone/motor is not the entire mass against
which the motor applies force as this must include the moving air mass
loading. That said, I'd expect this to become a tiny contribution at
LF for a typical boxed speaker. However I also wonder how heavy the
cones and motors are for subwoofers as they may need to be very
stiff/strong if the speaker is an infinite baffle.

I'm not sure exactly what the configuration of this sub is called. Quick
bit of ascii art should speak 1k (fixed width font). I think this may be
a 'bandpass' enclosure?
_______
f |__ | | behind the driver is enclosed, with ported enclosure
r | | to the front of it. The port goes very near the middle
o |¯¯ | | wall.
n | \ |
t | D | D = driver
| / |
¯¯¯¯¯¯¯
I'd imagine that the force of compressing the air behind the driver is
considerable, as is the friction of moving air on a non-straight path.
Then again, I've never studied liquid dynamics, so this is really just
guessing.

Not seen any figures / calculations / models of this, but I do wonder
about it. When I fitted spikes to the stands of my ESL63's I did form
the view that the bass was altered. That said, an ESL is a very
different case to a boxed subwoofer, and the ESL63 is pretty light
compared with a typical large boxed speaker, so this might not be a
reliable guide to the general situations.

It'd be hard to imagine that changing the speaker to the size of the
floor wouldn't change the sound at all.

I think the problem is that nobody seems to be able to explain exactly
what is happening, other than the sound is changing. I've read in hifi
mags that spikes DEcouple the speaker by reducing contact area with the
floor. lol!

--
Jim H

"Jim Lesurf" wrote in message

In article , Arny Krueger
wrote:


My point with the fishing line example is that the box doesn't move
that much, especially compared to the cone. If the box were
suspended, the rule of equal and opposite reactions would hold. Then
motion of the box and the motion of the cone would be proportional
to their respective weights or masses.

It turns out that the moving mass of a woofer cone is often
specified, and it's on the order of 15 grams for a large woofer. A
subwoofer and its enclosure weighs at least 15 kilograms, so the
mass ratio is at least 1000:1. Often it is more, far more.

That means that the box moves a thousandth of a millimeter or less
for every millimeter that the cone moves. Got the picture? The box
moves so little that its motion is practically irrelevant to sound
quality.

I agree with most of the above, but have a slight uncertainty about a
few points... :-)

I'd agree that the action and reaction forces will tend to be equal
and opposite (Newton). However although the movements of the
box/floor will be small in terms of amplitude compared with the
speaker cone I wonder about the radiation efficiency once the floor
area is coupled to the box.

If you couple the floor to the box, then that increases the effective mass
of the box, right?

Increase the effective mass of the speaker box and you further decrease its
motion.

In the end it comes down to the mass/area ratio of the floor versus the
mass/area ratio of the speaker box presuming the coupling to the floor is
perfectly rigid. Based on what I know about how speaker boxes and floors are
made, I'd say that floors are more massive per unit area than your typical
speaker box.

Although the displacements are small, the
area moving may be much larger than the area of the speaker cone.
Hence I am not yet sure that the sound levels radiated are simply in
proportion with the masses.

Per my analysis above, adding in the floor probably strenghtens my argument,
no?

Another point is that the cone/motor is not the entire mass against
which the motor applies force as this must include the moving air
mass loading. That said, I'd expect this to become a tiny
contribution at LF for a typical boxed speaker.

Yes, we know that the air mass contributes very little to the loading on the
cone except in horns. That's why horns show the benefits that they do.

However I also wonder
how heavy the cones and motors are for subwoofers as they may need to
be very stiff/strong if the speaker is an infinite baffle.

The mass number I cited was for a driver that could easily be used in a
subwoofer.

Not seen any figures / calculations / models of this, but I do wonder
about it. When I fitted spikes to the stands of my ESL63's I did form
the view that the bass was altered. That said, an ESL is a very
different case to a boxed subwoofer, and the ESL63 is pretty light
compared with a typical large boxed speaker, so this might not be a
reliable guide to the general situations.

I'd agree that you had the perception that the bass was altered. However,
was the bass *actually* altered?

;-)

In article , Jim H
wrote:
Jim Lesurf in uk.rec.audio:


If the spikes are cheap enough there may be no harm in trying them,
but perhaps being doubtful whilst doing so. You may end up with holes
in the carpet, though. :-)

Falcon accoustics have some here http://www.falcon-
acoustics.co.uk/pl28p9.htm for £2.60, acceptable cost for an experiment,
but I'm not sure I want to order from a company with, frankly, such an
amatuer website (sorry if anyone here works there etc). Anyone have
experiance in ordering from them?

Afraid I have not had any dealings with them so can't comment on that.
However the spikes seem cheap enough to be 'disposable' if you conclude
they don't do anything useful.

I would not judge a company by its website being poor. Many company sites
are exceedingly flashy and irritating, but this just tells you about the
site designers. Those running the company may have no knowledge of this
area so leave it to 'experts' sic.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article , Jim H
wrote:
Extending from what you said, Arny, do you think there is no value in
any stands that attempt to tightly couple speakers to the floor/wall?
What do you think of filling things with sand?

I'm not Arny, but I'll risk some comments of my own... :-)

Filling stands with sand may well have an effect at higher frequencies. For
example, the stands I am currently using with the DVD system in the living
room have metal tubular verticals which ring like cow-bells when I tap
them. This may well mean they are ringing along with the music. Not yet got
around to filling them with sand, but this would probably deaden any
contributions they might be making to the sound. :-)

I filled mine with sand, but because I live overlooking the sea and
thought I might as well. I can't say if the sound improved because I
didn't listen to them empty. If I lived anywhere else I don't think I'd
have bothered.

Should help matters when you play VW's 1st symphony or some Britten operas.
Help these pieces to feel at home.. ;-

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article , Arny Krueger
wrote:
"Jim Lesurf" wrote in message



I'd agree that the action and reaction forces will tend to be equal
and opposite (Newton). However although the movements of the box/floor
will be small in terms of amplitude compared with the speaker cone I
wonder about the radiation efficiency once the floor area is coupled
to the box.

If you couple the floor to the box, then that increases the effective
mass of the box, right?

Agreed.

Increase the effective mass of the speaker box and you further decrease
its motion.

OK.

In the end it comes down to the mass/area ratio of the floor versus the
mass/area ratio of the speaker box presuming the coupling to the floor
is perfectly rigid. Based on what I know about how speaker boxes and
floors are made, I'd say that floors are more massive per unit area than
your typical speaker box.

I'm not sure of this, or of the relative flexibilities, radiation
efficiencies, etc. I am also not sure of how/if it may matter changing
from one form of speaker to another - e.g. a downward firing IB sub
to/from a ported side-firing design.

Although the displacements are small, the area moving may be much
larger than the area of the speaker cone. Hence I am not yet sure that
the sound levels radiated are simply in proportion with the masses.

Per my analysis above, adding in the floor probably strenghtens my
argument, no?

I am not sure of this. I would need to do a proper analysis or measurements
to decide. Your argument is perfectly plausible, but I am not certain it is
the whole story.


Not seen any figures / calculations / models of this, but I do wonder
about it. When I fitted spikes to the stands of my ESL63's I did form
the view that the bass was altered. That said, an ESL is a very
different case to a boxed subwoofer, and the ESL63 is pretty light
compared with a typical large boxed speaker, so this might not be a
reliable guide to the general situations.

I'd agree that you had the perception that the bass was altered.
However, was the bass *actually* altered?

;-)

Pass. :-) Certainly possible that my impression was misleading.

FWIW I did do some before and after measurements and they showed a
difference in response. However I am not at all sure these measurements
were reliable enough as it is very hard to measure such things in a real
room situation and I am not sure I did this well enough at the time.

The ESL63 is something of a special case in this area as both the diaphragm
and the body have quite low masses, and the speaker is dipolar. Hence the
situation is very different to using an IB subwoofer. As a result, even if
it did make a change I am not sure this means a similar change would be
audible with a conventional speaker or subwoofer.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Sea shore sand is generally accompanied by corrosive sea salt unless its
washed & well dried. Internal surfaces of undipped stands unprotected
against corrosion. Kids play sand is very clean + cheap enough, saves all
that hassle. Vaughan Williams Sea Symphony will sound okay then.

Mike

"Jim H" wrote in message
...
Extending from what you said, Arny, do you think there is no value in any
stands that attempt to tightly couple speakers to the floor/wall? What do
you think of filling things with sand?

I filled mine with sand, but because I live overlooking the sea and
thought
I might as well. I can't say if the sound improved because I didn't listen
to them empty. If I lived anywhere else I don't think I'd have bothered.

--
Jim H

Jim Lesurf in uk.rec.audio:

But a comerce site should be plain and functional but not flashy, in order
to earn the trust of the user. I've spent the last few weeks writing xsl to
this end.
Anyway, I've emailed them asking a few things. If I get the spikes I'll
post here how I get on. I'd imagine any changes will me minimal. Most
likely very small or no improvement, but not a worse sound.

Of course, after the speaker cable thread, the listening will be double
blind :-)

--
Jim H

Using a freeware sweep generator I found a frequency that made them
vibrate. There was a definate ring in the legs which stopped when held,
but this could only be heard with my ear very close.

Was it the same note that rang out when you gave them a tap? :-)