Decoupling speakers from resonant floor
Franco Del Principe
This issue has been troubling me the last 12 months. I have
been following the posts on this group regarding decoupling
of speakers and went through different types of setups like
spikes, bycicle inner tubes and what have you. (I should
mention that I prefer DIY solutions because for me this is
the fun part of being an audiophile, and because I can't
afford to pay kilobucks for sophisticated vibration control
devices).
I am not satisfied at all with the low frequency control in
my listening room. The room is about 6 by 6 meters and 2.4
meters high. The floor is concrete with floating parquet.
Without furniture hand clapping lasts about 4 seconds...
Apart from resonances between 40 and 100 Hz (test disk) the
whole range of bass is overemphasized, unclear, reverberant.
The newest and promising approach I tried was from the
manufacturer of my speakers to whom I explained the problem.
To reduce floor-borne resonances he suggested the
following (as I understand there is also air-borne resonance
which has to be treated by room dampening). Move the
speakers closer to the front wall to reduce reverberance
(speakers are bipolar). Couple the speakers with spikes to a
heavy granite plate and isolate it from the floor by a 5mm
layer of rubber foam. His rationale was to increase the
speaker's mass (18 kg + 15 kg granite) and reduce
transmission of low frequency to the parquet. The effect was
clearly audible but not that satisfactory. By further
extrapolating his idea I replaced the rubber foam by squash
balls. However, the bass seems to be louder in amplitude but
longer in duration (these are all impressions, I don't have
the means to measure).
Apparently, I am setting up a high pass filter. But how can
I calculate the cut off frequency with the mass given and
how stiff should the material be under the granite plates?
Somebody likes to comment? Or offer advice? Point to a paper
or physics handbook? I am ready to do experiments...
Cheers,
Franco
Dan Shike
your situation and i'm sure help will flow forth.
it sounds to me like you can do more good with room treatment than
speaker isolation, although that can't hurt. you make it sound like
you have nothing but hard surfaces in your room...try some rugs on
the floor, the thicker the better. anything on the walls? the less
smooth the walls are, the more your sound will improve. pictures,
lamps, whatever. i've found that every time my girlfriend moves more
junk into my listening room, the sound improves.
give more details though.
good luck
dan
Ron
room will emphasize the bass in the 40 to 60Hz range. There will be
many standing waves and resonance modes from having exactly the same
length and width, and the standing waves from 6 meters is around 50
to 60Hz assuming I did my math correctly. Unless you can change the
room shape, you might want to add partitioning to reduce resonance
modes from the room dimensions. You can try to get computerized
programs to see what you can do to solve the resonance modes from the
6 by 6 meters dimension.
Ron
Franco Del Principe <franco.de...@lis.ch> wrote in message
news:ac1ck...@enews4.newsguy.com...
Charlie G
news:ac1ck...@enews4.newsguy.com...
> Hi,
>
> I am not satisfied at all with the low frequency control in
> my listening room. The room is about 6 by 6 meters and 2.4
> meters high. The floor is concrete with floating parquet.
> Without furniture hand clapping lasts about 4 seconds...
> Apart from resonances between 40 and 100 Hz (test disk) the
> whole range of bass is overemphasized, unclear, reverberant.
>
Having two or more major room dimensions identical is generally
considered a bad thing for bass performance. The fact that your room
length and width are the same is probably one of the biggest single
sources of your low frequency troubles. Practical room treatments may
not help you much in this particular area. If you have the option of
moving your system into another listening room, you might try that
first.
Another solution would be to shorten one of the 6 meter room
dimensions to 3.84 meters to achieve that golden room ratio of
1:1.6:2.5, but this probably isn't a very practical room treatment
either :-)
--
~Charlie G <cgra...@hotmail.com>
Andre Moreau
1- Decoupling speakers from the floor is important. However, metal
cones and saucers do a better job than metal spikes.
2- Speaker placement is important. The farther they are from the
wall, the better your speakers will sound, unless they are Linn
speakers in which case they should be as near as possible to the
wall.
The sound of my speakers improved when I moved then from 10" from the
wall to 24" They even sound better at 36" from the wall, but this is
not practical for me.
Experiments with different speaker placements. This is one tweak that
does not cost anything. Be creative.
3- Room acoustics. You do listen to music with furniture in the room,
don't you ? So dont worry about reverberation of an empty room.
One cheap solution is to use fiber accoustic panels from a home
hardware center. A 4 x 8 sheet should cost less then $15.00 Cut them
up into 2" x 3" panels or whatever size you need, cover them up with
covering material from wall-mart and hang them up like a picture
frame. Dont forget the corners. Again be creative
Another solution is to have a rug over your hardwood floor, probably
something like 6 x 8 or larger, placed between your listening
position and your speakers.
4- Listening position. How far from your speakers are you sitting.
Have you tried listening in the near field. Place your speakers about
7 feet apart and sit at 7 feet from imaginary line between your
speakers. Now toe in you speakers a little at a time. You should
always see the inside face of both speakers. Move your listening
positing closer to your speakers a few inches at a time while
lowering the volume.
5- Have a look at www.uhfmag.com There's lots of reading on this
site.
Hope this helps,
Andre
"Franco Del Principe" <franco.de...@lis.ch> a écrit dans le message de
news: ac1ck...@enews4.newsguy.com...
Mkuller
their great bass response, say that he prefers his speakers not be
coupled to the floor (spiked) because sound travels faster through
the solid floor than air and will smear the bass.
Personally, I have always preferred my speakers spiked (through the
carpet to my concrete floor). At the suggestion of Black Diamond
Racing (I am a big fan of their carbon fiber equipment Shelves and
Cones), I installed their cones at the four corners of each of my
speakers and set each cone on a round puck made of the same material,
effectively decoupling the speakers from the floor. To my surprise,
there was a general overall improvement in the sound. However, after
some consideration, I decided that the asthetics were not worth the
improvement - the speakers looked funny sitting on these black pucks
atop the light carpet. Others may have a different opinion depending
on how much audible improvement they get. I suggest this is worth a
try.
Regards,
Mike
Fr@ncuz
Maybe this site help you:
http://www.hunecke.de/calculator/hifi/room-acoustics-hifi.htm
Of course this is only computer simulaton, but for the begining is
better than nothing.
Best regards Fe@ntz
dangling entity
Something that I discovered works well to circumvent bass reverberant
room effects- put the subs as close as possible to your seating
position (at least on your side of the room, instead of across the
room). With the subs close to you, that's the most direct sound you
can get. The direct sound will get to you before the reverberation
vs. listening to your sub after the output has crossed all of the
acoustic landmines of your room before getting to your ears.
Adjustment of lowpass filter and phase setting (if you have it) will
be more critical in such an arrangement though. In my last apartment,
it was simply fabulous bass- so worth it, I kid you not.
Franco Del Principe
Here are my thoughts
1. Yes, the build-up of resonance modes and standing waves
is favourised by the room geometry. I have furniture (sofa,
chairs, rugs, book shelves, curtains) but this helps only
for mid/high frequencies. As far as I remember: to dampen a
100 Hz wave (lambda in air = 3.44 m) you need e.g. pyramid
panels with a thickness (pyramid height) of half the
wavelength, i.e. 1.7 m... say no more.
2. An electronic solution like equalizer or DSP is not an
option for me. (Yes, I am a fan of "Keep it pure and simple").
3. I thought of running a calculation with Cara software or
the service given on www.hunecke.de (no problem with german,
I live in Switzerland :-) However, there is no data about my
speakers (Rowen R3 MkII, bipolar). Maybe I should ask the
swiss manufacturer to provide the data to plug into the
software.
4. Room treatment:
Well, my listening room is the living room which I have to
share with my wife, two daughters and two cats. So, although
they have much comprehension for my hobby, a treatment with
absorption panels, corner triangles or bass traps is out of
the question.
There are still some open questions I would like to discuss.
a) When I put glass marbles instead of squash balls under
the speakers/granite the imaging improves a lot. And the
bass is less smeared. As I understand, the marbles provide
stiff coupling in the vertical direction, while having two
degrees of freedom in the horizontal plane (corresponding to
the movement of the driver membranes). This is due to the
placing of the marbles into spherical wells which allows for
a small free movement while keeping the marble in place.
Is my interpretation correct when I say that with marbles
(and not with squash balls) the air-borne resonances are
reduced and only floor resonances remain? Any explanations
or expert opinion?
b) The 6 x 6 m geometry enhances the creation of standing
waves. If I move closer to the near field the bass
definition improves indeed, but unfortunately also decreases
the depth of imaging of my bipolar speakers.
To take this a bit further: If I would place the speakers
"over the corner" so that they would radiate in an oblique
angle (say around 45 degrees) into the room how would the
resonance modes change? Would I have less standing waves?
Less maxima at my listening position? Or just a different
distribution of the maxima?
BTW: It would be nice to have a technique which could
visualize the location of the pressure maxima/minima. One
which comes to mind is to fill the room completely with very
small soap bubbles a observe the changes in their
distribution density to localize the different pressure
spots. Hard to do in practice, though.
Cheers,
Franco
Tim S.
> the speakers/granite the imaging improves a lot. And the
> bass is less smeared. As I understand, the marbles provide
> stiff coupling in the vertical direction, while having two
> degrees of freedom in the horizontal plane (corresponding to
> the movement of the driver membranes). This is due to the
> placing of the marbles into spherical wells which allows for
> a small free movement while keeping the marble in place.
> Is my interpretation correct when I say that with marbles
> (and not with squash balls) the air-borne resonances are
> reduced and only floor resonances remain? Any explanations
> or expert opinion?
One thing I've experimented with over the years is speaker
supports. The results have ALWAYS been consistently better
transparency and imaging when the speaker is rigidly
immobilized. The theory is that woofer movement against the
air causes the cabinet to move in reaction, affecting the
absolute motion of all drivers relative to the air. The cabinet
reacting to room standing waves might also be a factor, and
would be reduced with a really rigid speaker mounting. I am
assuming floor vibration is mostly in the vertical direction, so
it would not have a large effect on the sound since driver
motion is horizontal.
Any reviews I have seen of squishy objects under speakers
have all concluded that they made a difference, but in the
end the reviewer always preferred spikes or something solid
underneath. For best sound, you want to be able to push
gently on the top front corner of the cabinet and it simply
does not move at all. In my experience, this is one case
where theory and practice truly agree...
Tim Skene
Thomas A
> > a) When I put glass marbles instead of squash balls under
> > the speakers/granite the imaging improves a lot. And the
> > bass is less smeared. As I understand, the marbles provide
> > stiff coupling in the vertical direction, while having two
> > degrees of freedom in the horizontal plane (corresponding to
> > the movement of the driver membranes). This is due to the
> > placing of the marbles into spherical wells which allows for
> > a small free movement while keeping the marble in place.
> > Is my interpretation correct when I say that with marbles
> > (and not with squash balls) the air-borne resonances are
> > reduced and only floor resonances remain? Any explanations
> > or expert opinion?
>
> One thing I've experimented with over the years is speaker
> supports. The results have ALWAYS been consistently better
> transparency and imaging when the speaker is rigidly
> immobilized.
As a preference it may be better. There is nothing saying that the
sound is more accurate with spikes under the speakers.
> The theory is that woofer movement against the
> air causes the cabinet to move in reaction, affecting the
> absolute motion of all drivers relative to the air.
The difference in cabinet movement between spikes and soft feet are
nothing above about 100 Hz. The movement of the cabinet is higher when
using spikes in the 20-100 Hz region. It's confirmed with mathematical
calculations as well as accelerometer measurements.
> The cabinet
> reacting to room standing waves might also be a factor, and
> would be reduced with a really rigid speaker mounting.
True that standing waves may act on the cabinet and move it, and that
the effect may be higher using soft feet. However, the sum of the
cabinet movement is always higher using spikes, because of the
resonant behaviour in the 20-100 Hz region.
> I am
> assuming floor vibration is mostly in the vertical direction, so
> it would not have a large effect on the sound since driver
> motion is horizontal.
>
If there is a wood floor, the the horizontal movement need to be of
equal freqeuncy and amplitude to move the speaker straight
horizontally. Due to various stiffnes in floor and different
weight/pressure at each spike position, this is unlikely to happen,
which leads to a vertical movement of the cabinet.
> Any reviews I have seen of squishy objects under speakers
> have all concluded that they made a difference, but in the
> end the reviewer always preferred spikes or something solid
> underneath.
Not in my opinion. I prefer soft feet. Many other I know also prefer
soft feet.
> For best sound, you want to be able to push
> gently on the top front corner of the cabinet and it simply
> does not move at all. In my experience, this is one case
> where theory and practice truly agree...
Well, measurements show that cabinets move more with stiff coupling
when playing music. Spikes is only a preference, no more.
>
> Tim Skene
Thomas A
> equal freqeuncy and amplitude to move the speaker straight
> horizontally. Due to various stiffnes in floor and different
> weight/pressure at each spike position, this is unlikely to happen,
> which leads to a vertical movement of the cabinet.
>
I always seem to mix up the words horizontal and vertical ...:-)
Just exchange the horizontal with the word vertical, and vice versa.
Thomas