speaker phasing

[dave]

On 12/06/2013 07:32 AM, Pat wrote:

On Fri, 6 Dec 2013 09:16:21 +1100, "Phil Allison" <phil_a@tpg.com.au



ESS also had a version where the passive radiator was on the rear. (I
think it was AMT 1's vs. my AMT Monitors). I had previously wondered
how the rear facing passive in the AMT 1 and the front facing passive
in the ATM Monitors both could work well. Now, I think I understand.

Thanks,
Pat

Why not just put balloons inside a sealed box? Or maybe a hydraulic
shock absorber.,..,

 

[William Sommerwerck]

"dave" wrote in message
news:I7CdndBnRJT7nD_PnZ2dnUVZ_rSdnZ2d@earthlink.com...

Why not just put balloons inside a sealed box? Or maybe a hydraulic shock
absorber...

It's been done. William Michael Watson Dayton-Wright built conventional
dynamic speakers with bags of SF6 in the woofer box. He got clean bass to
below 16Hz from a small cabinet.

 

[dave]

On 12/06/2013 11:18 AM, William Sommerwerck wrote:

"dave" wrote in message
news:I7CdndBnRJT7nD_PnZ2dnUVZ_rSdnZ2d@earthlink.com...

Why not just put balloons inside a sealed box? Or maybe a hydraulic
shock absorber...

It's been done. William Michael Watson Dayton-Wright built conventional
dynamic speakers with bags of SF6 in the woofer box. He got clean bass
to below 16Hz from a small cabinet.

We learned 16 Hz is perceived more as a train of pulses and less like a
sinusoidal tone; it is right on the border of flatulence.


These are the jokes, folks. No tirades if you can suppress the urge.

 

[William Sommerwerck]

"dave" wrote in message
news:_IudnaaUYK9ntD_PnZ2dnUVZ_qKdnZ2d@earthlink.com...

We learned 16 Hz is perceived more as a train of pulses and
less like a sinusoidal tone; it is right on the border of flatulence.

When I put 16Hz through the Watson woofers in my concrete-slab apartment...
//nothing// audible came out of the woofers. But everything in the room
rattled.

 

[gregz]

Pat <pat@nospam.us> wrote:

On Sat, 30 Nov 2013 07:00:29 +1100, "Phil Allison" <phil_a@tpg.com.au
wrote:


Phasing similar speakers is all about making the low frequency output from
each *reinforce* the others rather than cancel.

Compared to the wavelengths of low frequency sound, woofers are a point (
hence omnidirectional ) source of sound pressure - so it is irrelevant
which way the cone faces.


... Phil


Hi Phil,
I was away for a while, so this thread is new to me today. Your
comments above make sense, but bring up a question I have had for many
years. I own a pair of ESS AMT Monitor speakers that I purchased new
back in the 80's. Each has a pair of 12" woofers - one active (ie, a
normal speaker) and the other passive. I would think that when the
active one is compressing the air in the cabinet, the passive one
would be pushed out thereby appearing to be out of phase to a
listener. That doesn't appear to be the case because these speaker
have a great low end sound. Can you explain why they work? (I am
just picking you because you seem to know something about the subject,
but others are welcome to explain my misunderstanding as well.)

Thanks,
Pat

I heard the ess once, in a Vegas disco, of all places. Just a fill in
speaker.

On a port or passive, most of the output is from the port or passive, so
they don't cancel. This is around th tuned frequency. Woofer movement
becomes minimal. If you drove it with an oscillator you could probably find
this out.

Greg

 

[gregz]

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote:

"dave" wrote in message news:_IudnaaUYK9ntD_PnZ2dnUVZ_qKdnZ2d@earthlink.com...

We learned 16 Hz is perceived more as a train of pulses and
less like a sinusoidal tone; it is right on the border of flatulence.

When I put 16Hz through the Watson woofers in my concrete-slab
apartment... //nothing// audible came out of the woofers. But everything
in the room rattled.

I used to rattle things in my old basement. It resonated around 30 hz, but
16 hz will shake things. With 30 hz in the basement, you had to be in the
right spots to hear or not hear 30 hz.

Greg

 

[dave]

On 12/06/2013 12:02 PM, William Sommerwerck wrote:

"dave" wrote in message
news:_IudnaaUYK9ntD_PnZ2dnUVZ_qKdnZ2d@earthlink.com...

We learned 16 Hz is perceived more as a train of pulses and
less like a sinusoidal tone; it is right on the border of flatulence.

When I put 16Hz through the Watson woofers in my concrete-slab
apartment... //nothing// audible came out of the woofers. But everything
in the room rattled.

Like when we have mild earthquakes.

 

[Phil Allison]

"William Sommerwerck"

It's been done. William Michael Watson Dayton-Wright built conventional
dynamic speakers with bags of SF6 in the woofer box.

** For what advantage ?

The speed of sound is about half in SF6 but that is no help in a sealed box
where resonance depends only on the stiffness of the volume of gas trapped
behind the woofer.

The smaller the volume or the larger the woofer, the stiffer it becomes.

> He got clean bass to below 16Hz from a small cabinet.

** Really ?



..... Phi

 

[William Sommerwerck]

"Phil Allison" wrote in message news:bgf6evF6to0U1@mid.individual.net...
"William Sommerwerck"

It's been done. William Michael Watson Dayton-Wright built conventional
dynamic speakers with bags of SF6 in the woofer box.

** For what advantage ?

The speed of sound is about half in SF6 but that is no help in a sealed
box where resonance depends only on the stiffness of the volume of
gas trapped behind the woofer.
The smaller the volume or the larger the woofer, the stiffer it becomes.

The lower speed of sound makes the bag appear to have a larger acoustic volume
than the air it replaces.


> He got clean bass to below 16Hz from a small cabinet.

** Really?

Really. The bass cabinet was about 20" by 20" by 12". At 16Hz, there was no
/audible/ output from the speaker, but everything loose in the room was
rattling.

The spec sheet for these speakers included a harmonic distortion curve. If I
recall correctly, the speaker had something like 5% harmonic distortion at
20Hz at 90dB output. (Don't hold me to the exact numbers, but the distortion
was very low.)

He also claimed that aluminum wool was a better damping material than
Fibreglas, fiberfill, or foam. He said the linearity of the driver's movement
depended in part on the thermal linearity of the damping material, and that
aluminum wool did a better job. I didn't fully understand this, so don't jump
on me.

Ever heard his SF6-filled electrostatics? We sold a pair to a man with a
large, dead basement. With each speaker powered by bridged Crown M300 amps,
the system could play at ear-splitting levels with no strain.

 

[Phil Allison]

"William Sommerwanker"

"Phil Allison"
It's been done. William Michael Watson Dayton-Wright built conventional
dynamic speakers with bags of SF6 in the woofer box.

** For what advantage ?

The speed of sound is about half in SF6 but that is no help in a sealed
box where resonance depends only on the stiffness of the volume of
gas trapped behind the woofer.

The smaller the volume or the larger the woofer, the stiffer it becomes.

The lower speed of sound makes the bag appear to have a larger acoustic
volume than the air it replaces.

** You have simply ignored question, which is the stiffness of a fixed
volume of gas.

Take a look at Boyle's Law ( PV = k )

Really. The bass cabinet was about 20" by 20" by 12".

** That is not a "small cabinet" at circa 50 litres internal volume.

Had an 15 inch woofer fitted - did it ?

At 16Hz, there was no /audible/ output from the speaker, but everything
loose in the room was rattling.

** Standing waves are a real bitch........


> Ever heard his SF6-filled electrostatics?

** Now that was done for an entirely different reason.



..... Phil

 

[William Sommerwerck]

I'm giving a respectful response, despite being called Sommerwanker. Shall I
start calling you Anuson?

It's been done. William Michael Watson Dayton-Wright built
conventional dynamic speakers with bags of SF6 in the woofer box.

** For what advantage ?

The speed of sound is about half in SF6 but that is no help in a sealed
box where resonance depends only on the stiffness of the volume of
gas trapped behind the woofer.
The smaller the volume or the larger the woofer, the stiffer it becomes.

The lower speed of sound makes the bag appear to have a larger acoustic
volume than the air it replaces.

** You have simply ignored the question, which is the stiffness of a fixed
volume of gas.

Take a look at Boyle's Law (PV = k)

As Michael Flanders put it... "The greater the pressure, the larger the volume
of hot air."

I found the spec sheet. He describes the SF6 as performing a linearizing
function. He says nothing about increasing the cabinet's "apparent" volume.
I'll call a friend who designs speakers and have him put me right -- if such
needs be done.

http://www.dayton-wright.com/WATSON-10_.html

> Really. The bass cabinet was about 20" by 20" by 12".

** That is not a "small cabinet" at circa 50 litres internal volume.

I consider it "small", as it was the bottom structure of a floor-standing
speaker. That's not a large enclosure for a speaker that gets to 20Hz and
lower with low distortion.


> Had an 15 inch woofer fitted -- did it ?

Nope. Two oddball 10" drivers -- with pie plates glued to them! See the photo.

At 16Hz, there was no /audible/ output from the speaker, but everything
loose in the room was rattling.

** Standing waves are a real bitch...

Oh, I walked around to see if I could hear any subsonic output. There was
none. Assuming you believe the spec sheet, note the ridiculously low LF
distortion.


> Ever heard his SF6-filled electrostatics?

** Now that was done for an entirely different reason.

 

[William Sommerwerck]

I just found the following quote:

"Only the woofer/subwoofer were not bipolar. These relied in the use of SF6
(sulfur hexafluoride) gas (which is inert), to increase the virtual volume of
the enclosure. As SF6 is an 'ideal gas', it operates as an 'isothermal'
spring, thus avoiding the problems with 'acoustic-suspension' loudspeakers
that operated partially as an isothermal and partially as an adiabatic system.
Some designers seemed to lave little knowledge of Boyles Law or the Laws of
Thermodynamics.

"In effect, the use of SF6, increases the virtual volume of the enclosure by a
factor of 27! As can be appreciated, this both lowers the distortion as well
as permitting a lower resonant frequency of the woofer."

It's here...

http://www.dayton-wright.com/WATSONLABS_.html

I should point out that the bass cabinet is not completely filled with SF6. If
I recall correctly, the gas bags were separated with foam sheets.

 

[Phil Allison]

"William Sommerwerck"

It's been done. William Michael Watson Dayton-Wright built
conventional dynamic speakers with bags of SF6 in the woofer box.

** For what advantage ?

The speed of sound is about half in SF6 but that is no help in a sealed
box where resonance depends only on the stiffness of the volume of
gas trapped behind the woofer.

The smaller the volume or the larger the woofer, the stiffer it becomes.

The lower speed of sound makes the bag appear to have a larger acoustic
volume than the air it replaces.

** You have simply ignored the question, which is the stiffness of a fixed
volume of gas.

Take a look at Boyle's Law (PV = k)

As Michael Flanders put it...

** You have ignored the question AGAIN !!!!!

I found the spec sheet. He describes the SF6 as performing a linearizing
function.

** Pure marketing hype.

Really. The bass cabinet was about 20" by 20" by 12".

** That is not a "small cabinet" at circa 50 litres internal volume.

I consider it "small",

** Yawnnnnnnnnnnnnnnnnn....

It is not small - a 10 litre box is small.

And Boyle's law makes all the claims re SF6 all wrong.



..... Phil

 

[Phil Allison]

"William Sommerwerck"

I just found the following quote:

** I found it two days ago and roared laughing.

It is the greatest pile of * bullshit * I have ever seen about woofers.

"Only the woofer/subwoofer were not bipolar. These relied in the use of
SF6 (sulfur hexafluoride) gas (which is inert), to increase the virtual
volume of the enclosure. As SF6 is an 'ideal gas', it operates as an
'isothermal' spring, thus avoiding the problems with 'acoustic-suspension'
loudspeakers that operated partially as an isothermal and partially as an
adiabatic system. Some designers seemed to lave little knowledge of Boyles
Law or the Laws of Thermodynamics.

"In effect, the use of SF6, increases the virtual volume of the enclosure
by a factor of 27! As can be appreciated, this both lowers the distortion
as well as permitting a lower resonant frequency of the woofer."

It's here...

http://www.dayton-wright.com/WATSONLABS_.html

** Marketing hype - not engineering fact.

The very next line is soooo telling:

" But to use this, a larger cone mass is needed and the suspension has to be
much more compliant."

Cos it contradicts the rest of the hype.

If SF6 worked as claimed, standard woofers would be all that was needed.

It doesn't.



..... Phil

 

[William Sommerwerck]

Unfortunately, Mr Anuson, I owned these speakers and can vouch for their
performance.

Mr Anuson, name a brand and model of woofer, of the volume given, that can get
down to 16Hz with such low distortion. I'm waiting...

It's impossible to have any kind of a discussion -- you know everything.
You're polite when people agree with you, and a vicious -- I can't think of
anything bad enough -- when they don't.

 

[William Sommerwerck]

Here's the answer to your question about Boyle's Law (which you will ignore,
of course)...

PV = k assumes a constant temperature. If the temperature changes, then PV
changes. The relationship is no longer linear, and as the air trapped in the
cabinet is supposedly providing a significant part of the restoring force, the
cone's displacement will not be as linear. (Duh... Get it?)

This is what WDW is talking about when he says "As SF6 is an 'ideal gas', it
operates as an 'isothermal' spring, thus avoiding the problems with
'acoustic-suspension' loudspeakers that operated partially as an isothermal
and partially as an adiabatic system. Some designers seemed to lave little
knowledge of Boyles Law or the Laws of Thermodynamics."

There is no such thing as an ideal gas, so WDW is wrong on this particular
point. However, if SF6 is significantly closer to being an isothermal gas than
air is, * then what he says makes sense. QED.

Gotcha! Finally got ya!

You may now jump up and down, Rumplestiltskin, until you break through the
floor.

* I can't find anything on this at the moment. But I'm looking.

 

[Maynard A. Philbrook Jr.]

In article <l81tsp$u0v$1@dont-email.me>, grizzledgeezer@comcast.net
says...

Here's the answer to your question about Boyle's Law (which you will ignore,
of course)...

PV = k assumes a constant temperature. If the temperature changes, then PV
changes. The relationship is no longer linear, and as the air trapped in the
cabinet is supposedly providing a significant part of the restoring force, the
cone's displacement will not be as linear. (Duh... Get it?)

This is what WDW is talking about when he says "As SF6 is an 'ideal gas', it
operates as an 'isothermal' spring, thus avoiding the problems with
'acoustic-suspension' loudspeakers that operated partially as an isothermal
and partially as an adiabatic system. Some designers seemed to lave little
knowledge of Boyles Law or the Laws of Thermodynamics."

There is no such thing as an ideal gas, so WDW is wrong on this particular
point. However, if SF6 is significantly closer to being an isothermal gas than
air is, * then what he says makes sense. QED.

Gotcha! Finally got ya!

But But But but!!!!!


Jamie

 

[William Sommerwerck]

"Maynard A. Philbrook Jr." wrote in message
news:MPG.2d0e5cef27c0eb009896e0@news.eternal-september.org...
In article <l81tsp$u0v$1@dont-email.me>, grizzledgeezer@comcast.net
says...

Gotcha! Finally got ya!

But But But but!!!!!

Indeed. Hoist with his own petard.

The best part is that the point was reasonable, so I had to do some research.
In the process, I learned something.

 

[Phil Allison]

"William Sommerwanker"

Here's the answer to your question about Boyle's Law (which you will
ignore, of course)...

PV = k assumes a constant temperature.

** PV= k shows that it does not matter what the gas is - the same volume
changes produce the same pressure changes.

So the stiffness of an enclosed volume of gas is the same for all gasses.

The resonance frequency of a woofer will be unaffected by it.


> If the temperature changes,

** Yawnnnnnnnnnnnn.....


Dunno who is the bigger LIAR.

You or the fuckwit you are mindlessly quoting.



..... Phil

 

[William Sommerwerck]

"Phil Allison" wrote in message news:bgk6rmF8e5nU1@mid.individual.net...
"William Sommerwanker"

Here's the answer to your question about Boyle's Law (which you will ignore,
of course)...

PV = k assumes a constant temperature.

** PV= k shows that it does not matter what the gas is - the same volume
changes produce the same pressure changes.

Uh... No it doesn't. k is temperature-dependent. Sorry about that,. but all
you have to do is look it up.
If a gas isn't perfect, then compressing (or rarefying it) changes its
temperature. This causes the pressure to change more than that caused by the
volume change. The result is a non-linear restoring force.

So the stiffness of an enclosed volume of gas is the same for all gasses.
The resonance frequency of a woofer will be unaffected by it.

That's not what we're talking about, Mr Anuson.

Dunno who is the bigger LIAR.
You or the fuckwit you are mindlessly quoting.

I'm quoting physics books.