Observation
15mm vs 20mm Thickness Plywood
Sound Comparison for Open Baffle
Using Fostex 103e
Both boards were cut to same size, about
80 cm x 90 cm.
Conclusion first :
20mm Plywood is not too good a match
for this particular Fostex 103e fullrange spkr.
15mm Plywood sounds MUCH Cleaner.
By Cleaner, I mean to say that one can Effortlessly
Hear MICRO DETAILS on the thinner 15mm
Plywood, which are simply LOST on the thicker
20mm plywood. The 3 D Magic is Almost Gone
on the thicker plywood.
I would Guess that the heavier, and denser thickness
Means that certain Absorptions take place, and
Important MICRO DETAILS are gone, thereby
Greatly Killing the Reason of going OB in first place.
Micro Details means Micro Vibrations, carrying
Most meaningful Micro INFORMATION on
DETAILS recorded, be it low amplitude info,
Or Phase info, etc etc,
All this Important Golden Information is simply
Killed, or Damped by the thicker , heavier board.
Yes, ladies and gents.
It is becoming apparent that the Art of Loudspeaker
Design is very much the same as Art of Guitar or
Cello or Piano design�c. THE WOOD MATTERS
In many More ways than we care to think.
I would further like to Playfully Challenge Those
That are Wood Musical Instrument makers to try to
Make a very Accurate and very Musical Loudspeaker.
I bet they can.
In this observation, the Deadening effect of the 20mm plywood
Is not as bad as MDF, but it is going in that Same direction.
I am going back to 15mm Plywood for the moment.
Now it would be fun to test different Height vs Width
For this thickness For OB.
Oh. One more thing. I wish I had a sensitive accelerometer
Or some such device to see on my oscilloscope, what my ears
Are telling me.
When one Gently TAPS almost Anywhere on the 15mm
Plywood, one can hear Good Consistent Strong Tap sounds
Anywhere One taps, even if one ' s ear is at one extreme end
of the OB Board. Trying this same TAP test on 20 mm
tells one Two things immediately :
The Sound is totally different, by being Very Much Muffled.
Next, as you TAP progressively away from your ear
Position and Tap Onwards, the energy reaching your ears
Really dimishes fast for every few inches moved.
On 15mm Plywood, no matter where you Tap, the energy
Hardly dimishes�c
This means, that VIBRATION is needed to make OB work.
At least to some extent of achieving good Balance.
Put your Ear an inch away from the OB.
Put your left hand ON any part of OB, perhaps
The top edge.
Start tapping with Right hand knuckle.
As your Right hand moves away Tapping here and there,
Note that your LEFT hand tells you there is much
Vibration on the 15mm plywood no matter where you tap.
However, for the 20mm, as your Right hand moves away,
even by few inches at a time,
The vibration reaching your Left hand , really dimishes
Quickly.
I further guess that the resonant frequency or frequencies
Of the 15mm are one matter, where as the 20 mm is
Quite another matter. I am not a Pro Musician , but
The difference is like going down 1 or more octaves
On the 20 mm and
Very Much Muffled Damping going on also.
All this , is also about DAMPING, be it
Just Right, or OVER or UNDER. Call it
Ringing, or vibration or resonant points, or
Whatever, but the principle is similar to building
A good sounding guitar VS. a very poor sounding one.
The WOOD MATTERS a LOT.
Pls note the obvious for
Basic Plywood OB and 103e system such as this,
Pls make sure the bottom of OB IS TOUCHING THE FLOOR.
Full Contact must be made. This mechanical coupling is a must.
OB seems to be about FREEDOM and Simplest Design Possible,
Using Most Logical Best materials matched to the speaker at hand.
Be good
k.
15mm vs 20mm Thickness Plywood
Sound Comparison for Open Baffle
Using Fostex 103e
Both boards were cut to same size, about
80 cm x 90 cm.
Conclusion first :
20mm Plywood is not too good a match
for this particular Fostex 103e fullrange spkr.
15mm Plywood sounds MUCH Cleaner.
By Cleaner, I mean to say that one can Effortlessly
Hear MICRO DETAILS on the thinner 15mm
Plywood, which are simply LOST on the thicker
20mm plywood. The 3 D Magic is Almost Gone
on the thicker plywood.
I would Guess that the heavier, and denser thickness
Means that certain Absorptions take place, and
Important MICRO DETAILS are gone, thereby
Greatly Killing the Reason of going OB in first place.
Micro Details means Micro Vibrations, carrying
Most meaningful Micro INFORMATION on
DETAILS recorded, be it low amplitude info,
Or Phase info, etc etc,
All this Important Golden Information is simply
Killed, or Damped by the thicker , heavier board.
Yes, ladies and gents.
It is becoming apparent that the Art of Loudspeaker
Design is very much the same as Art of Guitar or
Cello or Piano design�c. THE WOOD MATTERS
In many More ways than we care to think.
I would further like to Playfully Challenge Those
That are Wood Musical Instrument makers to try to
Make a very Accurate and very Musical Loudspeaker.
I bet they can.
In this observation, the Deadening effect of the 20mm plywood
Is not as bad as MDF, but it is going in that Same direction.
I am going back to 15mm Plywood for the moment.
Now it would be fun to test different Height vs Width
For this thickness For OB.
Oh. One more thing. I wish I had a sensitive accelerometer
Or some such device to see on my oscilloscope, what my ears
Are telling me.
When one Gently TAPS almost Anywhere on the 15mm
Plywood, one can hear Good Consistent Strong Tap sounds
Anywhere One taps, even if one ' s ear is at one extreme end
of the OB Board. Trying this same TAP test on 20 mm
tells one Two things immediately :
The Sound is totally different, by being Very Much Muffled.
Next, as you TAP progressively away from your ear
Position and Tap Onwards, the energy reaching your ears
Really dimishes fast for every few inches moved.
On 15mm Plywood, no matter where you Tap, the energy
Hardly dimishes�c
This means, that VIBRATION is needed to make OB work.
At least to some extent of achieving good Balance.
Put your Ear an inch away from the OB.
Put your left hand ON any part of OB, perhaps
The top edge.
Start tapping with Right hand knuckle.
As your Right hand moves away Tapping here and there,
Note that your LEFT hand tells you there is much
Vibration on the 15mm plywood no matter where you tap.
However, for the 20mm, as your Right hand moves away,
even by few inches at a time,
The vibration reaching your Left hand , really dimishes
Quickly.
I further guess that the resonant frequency or frequencies
Of the 15mm are one matter, where as the 20 mm is
Quite another matter. I am not a Pro Musician , but
The difference is like going down 1 or more octaves
On the 20 mm and
Very Much Muffled Damping going on also.
All this , is also about DAMPING, be it
Just Right, or OVER or UNDER. Call it
Ringing, or vibration or resonant points, or
Whatever, but the principle is similar to building
A good sounding guitar VS. a very poor sounding one.
The WOOD MATTERS a LOT.
Pls note the obvious for
Basic Plywood OB and 103e system such as this,
Pls make sure the bottom of OB IS TOUCHING THE FLOOR.
Full Contact must be made. This mechanical coupling is a must.
OB seems to be about FREEDOM and Simplest Design Possible,
Using Most Logical Best materials matched to the speaker at hand.
Be good
k.
I tend to agree with Cal on that. Perhaps I'm too stubborn to do all the calcs. But at the end of the day, it is our aural senses we wish to please, not the masses.
Comparing baffles with musical instuments. The sound board on a string instument is supposed to radiate sound. The strings alone don't radiate much. A baffle is supposed to be dead accustically speaking, or have I got it wrong with OBs.
If the drivers are front mounted, the thicker baffle will have a greater shielding effect. Try mounting the drivers on the rear, to see if the same applies. That's quicker than rebating or shamforing.
On the other hand, if weight or expense are an issue, a larger, thinner baffle may have an edge.
Comparing baffles with musical instuments. The sound board on a string instument is supposed to radiate sound. The strings alone don't radiate much. A baffle is supposed to be dead accustically speaking, or have I got it wrong with OBs.
If the drivers are front mounted, the thicker baffle will have a greater shielding effect. Try mounting the drivers on the rear, to see if the same applies. That's quicker than rebating or shamforing.
On the other hand, if weight or expense are an issue, a larger, thinner baffle may have an edge.
With an open baffle speaker, it's possible to decouple the driver from the baffle. Look how Linkwitz recommends that drivers be mounted to the baffles on his speakers (pressure mounted from the back).
I know some have also experimented with suspending the driver by it's frame/magnet, and attaching the baffle by various acoustically isolated means.
If the drivers are decoupled from the baffle, the baffle materials shouldn't make much difference, you can even try cardboard or styrofoam as baffles.
I know some have also experimented with suspending the driver by it's frame/magnet, and attaching the baffle by various acoustically isolated means.
If the drivers are decoupled from the baffle, the baffle materials shouldn't make much difference, you can even try cardboard or styrofoam as baffles.
I agree with Cal. We really need to know how the driver was mounted and the shape of the driver cutout before any conclusions can be made. Without flush mounting AND a very open rounded backside of the driver cutout, the 103 will sound poor on a 20mm thick board, because the frame openings will be very much blocked by the driver cutout. I've experienced this problem with another shallow basket Fostex, the 108Esigma. On OB it sounded very "closed in" until I sufficiently opened up and smoothed the backside of the driver cutout.
I don't think plywood is good for making any musical instruments. I've experienced enough baffle vibration in test baffles to know that I don't want to attempt to build any type of "singing baffles".
I don't think plywood is good for making any musical instruments. I've experienced enough baffle vibration in test baffles to know that I don't want to attempt to build any type of "singing baffles".
"I don't think plywood is good for making any musical instruments"
What is the sound board of a grand piano made from?
Many guitars have a 3 ply top. Some, a single ply top. Even solid electric guitars are laminated. Here we want that panel to vibrate.
The baffle vibrates out of phase with the cone, if it is rigid to the frame.
That is loss of efficiency and attack. Both no no's in my book.
Not sure about cardboard providing isolation at low frequencies, which is what the baffle has to do in order to reinforce the bass.
What is the sound board of a grand piano made from?
Many guitars have a 3 ply top. Some, a single ply top. Even solid electric guitars are laminated. Here we want that panel to vibrate.
The baffle vibrates out of phase with the cone, if it is rigid to the frame.
That is loss of efficiency and attack. Both no no's in my book.
Not sure about cardboard providing isolation at low frequencies, which is what the baffle has to do in order to reinforce the bass.
factored out
Thank you all for reading .
Pls note a most important fact.
i am trying to Compare the ( sound ) Difference
of the Two thicknesses of Plywood here.
The two fostex 103e units were mounted
in the SAME identical WAY. so.......
( in fact, towards the end.. i moved around
the same driver unit from one ob to the other,
so i can be convinced that the not so subtle
differences i was hearing, was not due to the two
driver differences or stereo tube amp L vs R
difference )
experimentally speaking, this means the only
difference that i am HEARING , should be
the OB plywood Thickness difference effect.
( yes, well, the 15mm and 20mm are different
by 5 mm, so of course, there is the question
of the composition of what that 5 mm is ..too...)
for your kind info,
both were merely Screwed in from FRONT, plainly and simply,
with the four supplied screws.
the Round HOLE is a clean diameter of 97mm.
nothing special done.
anything material on our planet,
has at least one resonance point.
FFT ananlysis, musical NOTES analysis, etc...all exist,
but unfortunately i dont have them at my disposal,
to thoroughly check the full story of a plank of wood.
perhaps this plank is a C sharp, and this is a G ?
again, pls be most aware of the
micro vibration Detail robbing properties of many
materials too.
again, the idea is
how to Balance all these factors and choices
to realize a final working unit to get
Realistic Musical Synergy and Events...
in other words, to get my foot tapping as if
only the music and i exist .
i believe
if i can learn enough from these OB
experiments, i can move onto more complex
designs and cabinets in future.
be good.
k.
Thank you all for reading .
Pls note a most important fact.
i am trying to Compare the ( sound ) Difference
of the Two thicknesses of Plywood here.
The two fostex 103e units were mounted
in the SAME identical WAY. so.......
( in fact, towards the end.. i moved around
the same driver unit from one ob to the other,
so i can be convinced that the not so subtle
differences i was hearing, was not due to the two
driver differences or stereo tube amp L vs R
difference )
experimentally speaking, this means the only
difference that i am HEARING , should be
the OB plywood Thickness difference effect.
( yes, well, the 15mm and 20mm are different
by 5 mm, so of course, there is the question
of the composition of what that 5 mm is ..too...)
for your kind info,
both were merely Screwed in from FRONT, plainly and simply,
with the four supplied screws.
the Round HOLE is a clean diameter of 97mm.
nothing special done.
anything material on our planet,
has at least one resonance point.
FFT ananlysis, musical NOTES analysis, etc...all exist,
but unfortunately i dont have them at my disposal,
to thoroughly check the full story of a plank of wood.
perhaps this plank is a C sharp, and this is a G ?
again, pls be most aware of the
micro vibration Detail robbing properties of many
materials too.
again, the idea is
how to Balance all these factors and choices
to realize a final working unit to get
Realistic Musical Synergy and Events...
in other words, to get my foot tapping as if
only the music and i exist .
i believe
if i can learn enough from these OB
experiments, i can move onto more complex
designs and cabinets in future.
be good.
k.
Kaybee,
I appreciate what you are trying to do, however, I'm confident that the significant difference in sound that you are hearing is related more to how much the 2 thicknesses restrict the rear wave as it leaves the driver, than microvibrations in the baffle itself. The thicker baffle blocks the rear wave from free expansion to such an extent that it is affecting the operation of the driver itself, in addition to the impact on the rear wave, because it loads cone different on the back side. The thin baffle is closer to free air operation of the driver.
Significantly open the backside of those driver cutouts if you want to make a better comparison of the different baffle thicknesses.
I appreciate what you are trying to do, however, I'm confident that the significant difference in sound that you are hearing is related more to how much the 2 thicknesses restrict the rear wave as it leaves the driver, than microvibrations in the baffle itself. The thicker baffle blocks the rear wave from free expansion to such an extent that it is affecting the operation of the driver itself, in addition to the impact on the rear wave, because it loads cone different on the back side. The thin baffle is closer to free air operation of the driver.
Significantly open the backside of those driver cutouts if you want to make a better comparison of the different baffle thicknesses.
johninCR said:
John, you're absolutely right about that; what would you say about rear mounting the driver and machining a chamfer or radius on the front. On 20mm thick panel you'd end up with a short "waveguide" of sorts, and while it could be opined that this would not be a perfectly balanced load to the driver cone, I'm sure it would "sound" far more open than the highly compressed conditions that you describe above.
This is more or less what resulted with one of our variations on supra-baffles for the Ron Clarke A126 horns.
Bob,
There's no doubt that different materials impart different sonic qualities. We were just pointing out to Kaybee that there are other factors involved.
BTW, mounting from the rear even with large rounding will also produce a waveguide effect with such a small driver, and it will vary with the material thickness. I think front mounting is fine. For optimum sonics with such a small driver, flush mounting may be needed. Be sure the backside can "breathe" as freely as possible. With my 108's I had to open up the cutout so much using 18mm ply that I had concern about sufficient material thickness for the mounting screws.
There's no doubt that different materials impart different sonic qualities. We were just pointing out to Kaybee that there are other factors involved.
BTW, mounting from the rear even with large rounding will also produce a waveguide effect with such a small driver, and it will vary with the material thickness. I think front mounting is fine. For optimum sonics with such a small driver, flush mounting may be needed. Be sure the backside can "breathe" as freely as possible. With my 108's I had to open up the cutout so much using 18mm ply that I had concern about sufficient material thickness for the mounting screws.
Cal Weldon said:
Very interesting Cal. It looks like I need to research the effects of rear mounting with these small drivers. The basket and magnet structure itself probably prevents the cone from true equal loading on both sides of the cone, in addition to acting as a LP filter in back. Rear mounting may actually help balance the cone loading. Maybe something in between is ideal, eg with the cone somewhere near the center line of the baffle thickness and both the front an back flared. Then we'd get a good unobstructed as possible half space launch from both sides of the baffle.
Sorry about the hijack Kaybee, but anything that could advance OB design facinates me.
Costa Rica Man,
I should mention that they are being used as an upper mid XO'd at 1K 6dB so I can't suggest how well the set up might work if crossed lower.
The back wave is a lot more apparent as you might expect. Nice "airiness"
These drivers also received the "planet10 treament" with duct seal, phase plugs, puzzle kote and some very rare, imported under questionable circumstances, sheeps wool.
After kaybee does the testing, I would like to hear the results with driver mods in place as well.
I should mention that they are being used as an upper mid XO'd at 1K 6dB so I can't suggest how well the set up might work if crossed lower.
The back wave is a lot more apparent as you might expect. Nice "airiness"
These drivers also received the "planet10 treament" with duct seal, phase plugs, puzzle kote and some very rare, imported under questionable circumstances, sheeps wool.After kaybee does the testing, I would like to hear the results with driver mods in place as well.
Cal Weldon said:Costa Rica Man,
I should mention that they are being used as an upper mid XO'd at 1K 6dB so I can't suggest how well the set up might work if crossed lower.
The back wave is a lot more apparent as you might expect. Nice "airiness"
After kaybee does the testing, I would like to hear the results with driver mods in place as well.
Cal, I've always believed Dave when he said the sheep were of legal consenting age.
all about Good Balance
diyaudio.com Nov 16 2006
weather : we have some.
Observation of Sound Differences
20mm vs 15mm Thickness plywood.
Had time, so did the tests you all requested.
20mm thickness plywood test :
Attaching the Fostex 103e to BACK of OB,
results in More Qty of Reflections into the Room.
Altho i did rounding out / chamfering ? of the
97mm diameter hole, i note that the Absorption
part of problem , remains the same. This wood
just sponges in the sound, and very little fun is
let out. this 20mm wood will be used on furniture,etc.
15mm thickness plywood test :
Attaching the Fostex 103e to BACK of OB,
results in More Qty of Reflections into the Room.
More careful tests will be done to see which i prefer
and for which type room.
Overall LIVENESS and 3 D magic of 15mm board
is not diminished.
New News.
I had very recently Bought some MORE 15mm
plywood. Please note that there is obvious
Weight, Quality, Finish Difference between this
Lot B vs. the above original 15mm board. ( herein
known as Lot A )
Now we talk of Same thickness, same size boards,
but different Qualities of Plywood.
Taking a screwdriver, i tap it gently on different parts
of both boards, Lot A and Lot B, Noting completely
different resonances.
Original Lot A had a Deeper, more Throaty sound
which i like and i perceive to be more accurate
for voicing 1 kHz and down. New Lot B has
a Lighter more shrill kind of character.. and bass
tone or heavy envelope sound is Less apparent.
Very THIN sounding you might say ?
Sticking in the two Fostex 103e ( and switching them
around later ) proves this point further more.
The new lighter, Lot B plywood is not as Harmonious ?
as the original heavier Lot A wood.
Sound difference is now like between Good
Throaty Guitar and cheap 8 dollar guitar.
this is so apparent to hear.
On the Lighter Lot B wood, not much volume is needed
to reach 90 dbC levels. On heavier Lot A wood,
you must turn up volume control a bit more to reach
same level.
Another thing, on lighter, Lot B wood, TOO much VOlume
and loudness comes Quick. Sound is almost compressed.
NOT fun to listen to , at high volumes.
On Lot A good wood, one feels like pushing for more
and more volume as the Feelings of Music get
Physcologically more INtense and Fun. One can
enjoy both Really Low volume and Really High Volume
Listening on this kind of perfectly Damped Wood.
Again,
the Original Lot A is a Better, Heavier, Denser
Quality than Lot B, despite identical physical
dimensions. Measureable difference here is weight.
Density, therefore is different, and perhaps
also HOW they were made / processed and
what types of woods are sandwiched between
the plywood layers.
So here, we come down to Quality again.
Huge difference comes about in sound character.
I will be talking to violin and other types of
Luthiers to see what kind of help i can get in
achieving a reasonably Repeatable strategy
for getting consistent Quality Wood.
I was thinking of Acrylic, but it seems that
it is in same family of absorbers like MDF, and
i must find some possible alternatives to
wood, perhaps heavy glass, or special metal
or special matrix plastic ? dunno yet.
i wish to work on materials that Vibrate in just
the right way, with good resonances. Besides
wood, can there be other options ?
since i can converse in japanese, i called up
fostex japan to talk to some people on
different days.
they agreed on some things �c.
Plywood would be more enjoyable and more
representative of fostex full range drivers.
going over 30mm thickness probably has no more merit.
Quality of wood used is the single HUGEST factor.
they have not tested or heard of successful tests
using other materials besides wood.
Leaving enough room on back of speaker is important
so room reflections can take place, in case of OB designs.
So in conclusion so far�c.stick to 17mm or sligthly LESS
thickness Plywood thickness for Small speaker full range
single driver ( such as fostex 103e ) OB designs. Make sure
you get GOOD weight plywood. Carry around a screwdriver
to tap test before buying if allowable. i will try to work out
weights and densities for you next time.
that�fs all for now folks.
be good.
k
diyaudio.com Nov 16 2006
weather : we have some.
Observation of Sound Differences
20mm vs 15mm Thickness plywood.
Had time, so did the tests you all requested.
20mm thickness plywood test :
Attaching the Fostex 103e to BACK of OB,
results in More Qty of Reflections into the Room.
Altho i did rounding out / chamfering ? of the
97mm diameter hole, i note that the Absorption
part of problem , remains the same. This wood
just sponges in the sound, and very little fun is
let out. this 20mm wood will be used on furniture,etc.
15mm thickness plywood test :
Attaching the Fostex 103e to BACK of OB,
results in More Qty of Reflections into the Room.
More careful tests will be done to see which i prefer
and for which type room.
Overall LIVENESS and 3 D magic of 15mm board
is not diminished.
New News.
I had very recently Bought some MORE 15mm
plywood. Please note that there is obvious
Weight, Quality, Finish Difference between this
Lot B vs. the above original 15mm board. ( herein
known as Lot A )
Now we talk of Same thickness, same size boards,
but different Qualities of Plywood.
Taking a screwdriver, i tap it gently on different parts
of both boards, Lot A and Lot B, Noting completely
different resonances.
Original Lot A had a Deeper, more Throaty sound
which i like and i perceive to be more accurate
for voicing 1 kHz and down. New Lot B has
a Lighter more shrill kind of character.. and bass
tone or heavy envelope sound is Less apparent.
Very THIN sounding you might say ?
Sticking in the two Fostex 103e ( and switching them
around later ) proves this point further more.
The new lighter, Lot B plywood is not as Harmonious ?
as the original heavier Lot A wood.
Sound difference is now like between Good
Throaty Guitar and cheap 8 dollar guitar.
this is so apparent to hear.
On the Lighter Lot B wood, not much volume is needed
to reach 90 dbC levels. On heavier Lot A wood,
you must turn up volume control a bit more to reach
same level.
Another thing, on lighter, Lot B wood, TOO much VOlume
and loudness comes Quick. Sound is almost compressed.
NOT fun to listen to , at high volumes.
On Lot A good wood, one feels like pushing for more
and more volume as the Feelings of Music get
Physcologically more INtense and Fun. One can
enjoy both Really Low volume and Really High Volume
Listening on this kind of perfectly Damped Wood.
Again,
the Original Lot A is a Better, Heavier, Denser
Quality than Lot B, despite identical physical
dimensions. Measureable difference here is weight.
Density, therefore is different, and perhaps
also HOW they were made / processed and
what types of woods are sandwiched between
the plywood layers.
So here, we come down to Quality again.
Huge difference comes about in sound character.
I will be talking to violin and other types of
Luthiers to see what kind of help i can get in
achieving a reasonably Repeatable strategy
for getting consistent Quality Wood.
I was thinking of Acrylic, but it seems that
it is in same family of absorbers like MDF, and
i must find some possible alternatives to
wood, perhaps heavy glass, or special metal
or special matrix plastic ? dunno yet.
i wish to work on materials that Vibrate in just
the right way, with good resonances. Besides
wood, can there be other options ?
since i can converse in japanese, i called up
fostex japan to talk to some people on
different days.
they agreed on some things �c.
Plywood would be more enjoyable and more
representative of fostex full range drivers.
going over 30mm thickness probably has no more merit.
Quality of wood used is the single HUGEST factor.
they have not tested or heard of successful tests
using other materials besides wood.
Leaving enough room on back of speaker is important
so room reflections can take place, in case of OB designs.
So in conclusion so far�c.stick to 17mm or sligthly LESS
thickness Plywood thickness for Small speaker full range
single driver ( such as fostex 103e ) OB designs. Make sure
you get GOOD weight plywood. Carry around a screwdriver
to tap test before buying if allowable. i will try to work out
weights and densities for you next time.
that�fs all for now folks.
be good.
k
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