The magnet system in this 3" dome midrange driver is inside the
voice-coil. I was thinking that the voice coil center might be a bit
deeper inside the driver than a typical dome tweeter, which it will be
crossed over to, on the same baffle. In other words, does anyone know
how far back the center of the voice-coil is from the rear of the front
flange? I could use some info on this because I'm using them with an
Eton 8-480, and I want to have the option to use a 1st order xover, so
I will be "time-aligning" all of the drivers so that the system has
that potential. Since I can't measure phase with LMS, I will be using
the voice coil centers for now.

Many thanks,
Dave

"Davespectral" wrote in message
oups.com...

** Google Groper .......


The magnet system in this 3" dome midrange driver is inside the
voice-coil. I was thinking that the voice coil center might be a bit
deeper inside the driver than a typical dome tweeter, which it will be
crossed over to, on the same baffle. In other words, does anyone know
how far back the center of the voice-coil is from the rear of the front
flange? I could use some info on this because I'm using them with an
Eton 8-480, and I want to have the option to use a 1st order xover, so
I will be "time-aligning" all of the drivers so that the system has
that potential. Since I can't measure phase with LMS, I will be using
the voice coil centers for now.


** Why ????

The "acoustic centre" is not the middle of the voice coil.

Sound pressure originates & radiates from the *surface* of the dome or cone
concerned.

The voice coil assembly generates force over its whole area and delivers it
to the edge of a dome virtually instantaneously.





........ Phil

Not exactly. For crossover work it is more accurate to use the distance
from the gap, if you can't measure the phase. Thanks for answering
though.
Dave

"Davespectral" wrote in message
ups.com...


** Learn to post properly - you ****ing Google Groper !!!

Quote:

" The "acoustic centre" is NOT the middle of the voice coil.

Sound pressure originates & radiates from the *surface* of the dome or cone
concerned.

The voice coil assembly generates force over its whole area and delivers it
to the edge of a dome virtually instantaneously. "


Not exactly.



** What is not exactly ???


For crossover work it is more accurate to use the distance
from the gap,


** Says who ???????

Someone completely ignorant of the basic laws of physics.


if you can't measure the phase. Thanks for answering
though.


** You ARE one arrogant little ****head.



........ Phil

The sound starts from the center of the gap you stupid ****-head.
Insecure assholes like yourself wreck the Internet.

Davespectral spake thus:

The sound starts from the center of the gap you stupid ****-head.
Insecure assholes like yourself wreck the Internet.

He is a ****head.

But please explain how the sound "starts from the center of the gap". I
think he's right here. The voice coil doesn't produce sound; the cone
does. That's where I'd measure from, no matter what the application.


--
A nation of sheep begets a government of wolves.

Davespectral wrote:
The magnet system in this 3" dome midrange driver is inside the
voice-coil. I was thinking that the voice coil center might be a bit
deeper inside the driver than a typical dome tweeter, which it will be
crossed over to, on the same baffle. In other words, does anyone know
how far back the center of the voice-coil is from the rear of the front
flange? I could use some info on this because I'm using them with an
Eton 8-480, and I want to have the option to use a 1st order xover, so
I will be "time-aligning" all of the drivers so that the system has
that potential. Since I can't measure phase with LMS, I will be using
the voice coil centers for now.

You have all the equipment you need to measure it.
Just create a stereo sinewave at your chosen crossover frequency,
vary the phase between the two channels (one for the tweeter, one for midrange)
and listen for the null. The details are left as an exercise for the reader.

--
Eiron

No good deed ever goes unpunished.

"Davespectral" wrote in message
oups.com..


** **** off - Google Gropers IDIOT !!!!


The sound starts from the center of the gap


** WRONG !!!!!!!!!!

The *sound* starts from the surface of the dome or cone.

The *electromagnetic force* that drives the voice coil travels at the speed
of light !!!

The *mechanical force* that drives the edge of the dome or cone travels at
*many* times the speed of sound in air.

Aligning voice coils is nuts.




....... Phil

Thank you Eiron, I knew about that from the Loudspeaker Design
Cookbook, but never tried it. When measuring from the cone or dome, and
then entering it in too LEAP, the results of the crossover simulation
are not nearly as accurate as measuring from the gap and then entering
that in to LEAP. Then there is the obvious question of where on the
cone should we measure from? The center? Half way up the side? I know
the higher frequencies supposedly come out from the center of the cone.
The times that I've measured from the gap, the results in LEAP are
deadly accurate.

I asked a simple question earlier, and got attacked by Phil, an obvious
psychopath. There are many of them on the net, because in their
personal lives, they are much to cowardly to react to people that way
to their face.

Phil Allison wrote:

The "acoustic centre" is not the middle of the voice coil.

True, it is somewhere behind as its apparant location is determined also
by the units delay.

Sound pressure originates & radiates from the *surface* of the dome or cone
concerned.

Also true, but not what is asked about.

The voice coil assembly generates force over its whole area and delivers it
to the edge of a dome virtually instantaneously.

Virtually meaning with a delay comparable to - for a midrange dome - a
single digit number of inches of air travel for sound.

....... Phil


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

Davespectral wrote:

Thank you Eiron, I knew about that from the Loudspeaker Design
Cookbook, but never tried it. When measuring from the cone or dome, and
then entering it in too LEAP, the results of the crossover simulation
are not nearly as accurate as measuring from the gap and then entering
that in to LEAP. Then there is the obvious question of where on the
cone should we measure from? The center? Half way up the side? I know
the higher frequencies supposedly come out from the center of the cone.
The times that I've measured from the gap, the results in LEAP are
deadly accurate.

I asked a simple question earlier, and got attacked by Phil, an obvious
psychopath. There are many of them on the net, because in their
personal lives, they are much to cowardly to react to people that way
to their face.

You got a sensible answer from Phil, which you ignored.
You then mistook his Australian charm for an insult and started an argument.

The speed of sound in a voice coil former is about 15 times that in air
so you can use the front of the former as a reference. You don't know the
speed of sound in the two domes; it varies with frequency and will be different
in the two drivers. Your best option is to mount them in the same plane
and do some measurements.

--
Eiron

No good deed ever goes unpunished.

Eiron wrote:
You got a sensible answer from Phil, which you ignored.
You then mistook his Australian charm for an insult and started an argument.

The speed of sound in a voice coil former is about 15 times that in air
so you can use the front of the former as a reference. You don't know the
speed of sound in the two domes; it varies with frequency and will be different
in the two drivers. Your best option is to mount them in the same plane
and do some measurements.

--
Eiron

No good deed ever goes unpunished.

I ignored him because he's full of crap. Hopefully he lives over there.
The speed of sound in the coil or the cone depends on the material that
they are made from. In metal, for instance, it is about four times the
speed of sound, and even that varies with what type of metal it is. If
you take a speaker motor structure, and strip away all of the cone, and
dust cap, it still makes sound in the higher frequencies. That is the
voice coil only. Maybe I didn't make it clear enough in my original
post. PHASE is what we are really talking about here.

Phil, who is full of crap, said, "The *sound* starts from the surface
of the dome or cone." WRONG, if it even starts from the cone it would
be from the area of the cone closest to the voice coil.

Then he says, "The *mechanical force* that drives the edge of the dome
or cone travels at *many* times the speed of sound in air." As I just
said, that depends on what material the cone is made from, therefor,
varying with every cone material out there.

Phil is an unthinking, blathering, useless individual.

Peter Larsen wrote:
Davespectral wrote:

I asked a simple question earlier, and got attacked by Phil,

Phil is right, you do not know how to make a usenet post and you
probably think that google invented usenet. On the substance matter, I
am right.


Kind regards

Peter Laresn


--
*******************************************
* My site is at: http://www.muyiovatki.dk *

Please don't tell me what I think. Sorry if I'm not a usenet expert,
but I'm getting the hang of it. Frankly, the question I originally
asked was answered elsewhere. I'm not trying to be disruptive, but when
attacked,i respond in kind.

"Davespectral"



** You are a VILE pile of Google Groping, sub human ****.


A sister ****er for sure.








......... Phil

"Davespectral"


** Go straight to HELL !!!

you pompous, asinine, ASD ****ed, Google Groper cretyn !!

Never post here again.







........ Phil

"Peter Larsen"


Not really, a loudspeaker unit has an overall time delay that means that
the apparent acoustic center in terms of temporal origin (radiation
origin seem to me to be what Phil is considering) is some distance
behind the voice coil.


** Impossible - you ****ING IDIOT !!!!

It is the other way around , you pathetic wog ****WIT - since sound
travels much FASTER in the voice coil assembly !!!





......... Phil

Davespectral wrote:

Just getting steady state waves aligned will not get the
wavefronts aligned. I had some MLSSA measurements done of
a DIY kit some years ago, I had gotten the staggering
between midrange and treble absolutely right on a whim,
but the bass unit, a Seas P17RCY, had so much more delay than
expected that staggering the midrange with respect to it had
been an irrelevant complexity, even though it made the box
look cute.

Oh Oh. I was afraid of that answer.

Don't be. I have not tried this, but direct comparison of a pulse
simultanousely set to all units may be possible by recording the output
with a small omni, say the Behringer measurmente mic. You do not need to
know the absolute delay, only the relative difference. Simply looking at
the recorded waveform on screen with some suitable audio software may
provide the information, but I have not actually tried doing it.

Maybe I should by a MLSSA type system.

I am not qualified to comment on whether one is required.

At the time I bought it, LMS was the cheapest thing going.
Thank you Peter, that was not what I wanted to hear, but
it was very helpful. can you recommend any cheaper
versions such as Liberty?

I will leave commenting on currently avaiable stuff to those that know
it better than I.

Dave


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

Phil Allison wrote:

It is the other way around , you pathetic wog ****WIT
- since sound travels much FASTER in the voice coil
assembly !!!

Yees, but first there is the issue of various inductances in the
equivalent diagram and their influence and _THEN_ the coil moves.
Because of that delay it appears as if the origin of the sound is behind
the unit from a temporal point of view.

........ Phil


Kind regards

Peter Larsen


--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

Peter Larsen wrote:
Not really, a loudspeaker unit has an overall time delay that means that
the apparent acoustic center in terms of temporal origin (radiation
origin seem to me to be what Phil is considering) is some distance
behind the voice coil.

Just getting steady state waves aligned will not get the wavefronts
aligned. I had some MLSSA measurements done of a DIY kit some years ago,
I had gotten the staggering between midrange and treble absolutely right
on a whim, but the bass unit, a Seas P17RCY, had so much more delay than
expected that staggering the midrange with respect to it had been an
irrelevant complexity, even though it made the box look cute.

Oh Oh. I was afraid of that answer. Maybe I should by a MLSSA type
system. At the time I bought it, LMS was the cheapest thing going.
Thank you Peter, that was not what I wanted to hear, but it was very
helpful. can you recommend any cheaper versions such as Liberty?

Dave

"Davespectral"


** It is clear what YOU are - Dave Smith.

A dangerous, paranoid schizophrenic criminal.

A total public menace.






......... Phil

"Peter Larsen"


It is the other way around , you pathetic wog ****WIT
- since sound travels much FASTER in the voice coil
assembly !!!

Yees,


** So the ****WIT finally ses he is completely WRONG !!!


but first there is the issue of various inductances in the
equivalent diagram and their influence and _THEN_ the coil moves.


** Complete drivel.

The creation of force from current is instantaneous.

The coil assembly accelerates immediately.




....... Phil

Phil Allison wrote:
"Peter Larsen"

It is the other way around , you pathetic wog ****WIT
- since sound travels much FASTER in the voice coil
assembly !!!
Yees,


** So the ****WIT finally ses he is completely WRONG !!!


but first there is the issue of various inductances in the
equivalent diagram and their influence and _THEN_ the coil moves.


** Complete drivel.

The creation of force from current is instantaneous.

The coil assembly accelerates immediately.

Einstein disagrees.

Dirk

Phil Allison wrote:

** Complete drivel.

The creation of force from current is instantaneous.

The coil assembly accelerates immediately.

With all the reactances in the equivalent diagramme of a loudspeaker it
is somewhat unlikely that instant generation of sound should happen
without being preceded by a time delay.

...... Phil


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

On 20 May 2006 03:00:26 -0700, "Davespectral"
wrote:

Eiron wrote:
You got a sensible answer from Phil, which you ignored.
You then mistook his Australian charm for an insult and started an argument.

The speed of sound in a voice coil former is about 15 times that in air
so you can use the front of the former as a reference. You don't know the
speed of sound in the two domes; it varies with frequency and will be different
in the two drivers. Your best option is to mount them in the same plane
and do some measurements.

--
Eiron

No good deed ever goes unpunished.

I ignored him because he's full of crap.

Actually he's not, he just has a terminally bad atitude.

Hopefully he lives over there.
The speed of sound in the coil or the cone depends on the material that
they are made from. In metal, for instance, it is about four times the
speed of sound, and even that varies with what type of metal it is. If
you take a speaker motor structure, and strip away all of the cone, and
dust cap, it still makes sound in the higher frequencies. That is the
voice coil only. Maybe I didn't make it clear enough in my original
post. PHASE is what we are really talking about here.

You made it clear, but you were wrong.

Phil, who is full of crap, said, "The *sound* starts from the surface
of the dome or cone." WRONG, if it even starts from the cone it would
be from the area of the cone closest to the voice coil.

No, you *specifically* asked about the acoustic centre of a Dynaudio
D76. It's a little way forward of the edge of the dome, nowhere near
the magnetic gap or the centre of the voice coil.

Then he says, "The *mechanical force* that drives the edge of the dome
or cone travels at *many* times the speed of sound in air." As I just
said, that depends on what material the cone is made from, therefor,
varying with every cone material out there.

Phil is an unthinking, blathering, useless individual.

No, that would be you. Phil is a foul-mouthed individual, but that
doesn't make him incorrect.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

Posted Via Usenet.com Premium Usenet Newsgroup Services
----------------------------------------------------------
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On Sat, 20 May 2006 01:05:51 -0700, David Nebenzahl
wrote:

Davespectral spake thus:

The sound starts from the center of the gap you stupid ****-head.
Insecure assholes like yourself wreck the Internet.

He is a ****head.

But please explain how the sound "starts from the center of the gap". I
think he's right here. The voice coil doesn't produce sound; the cone
does. That's where I'd measure from, no matter what the application.

Quite so. Phil may be a dickhead, but he's right about this and
'Davespectral' is wrong. The acoustic centre of that Dynaudio dome is
just ahead of the dome edge.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

Posted Via Usenet.com Premium Usenet Newsgroup Services
----------------------------------------------------------
** SPEED ** RETENTION ** COMPLETION ** ANONYMITY **
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On Sun, 21 May 2006 14:05:31 +0200, Peter Larsen
wrote:

Phil Allison wrote:

** Complete drivel.

The creation of force from current is instantaneous.

The coil assembly accelerates immediately.

With all the reactances in the equivalent diagramme of a loudspeaker it
is somewhat unlikely that instant generation of sound should happen
without being preceded by a time delay.

We're talking a couple of nanoseconds at the most, hardly relevant to
audio!
--

Stewart Pinkerton | Music is Art - Audio is Engineering

Posted Via Usenet.com Premium Usenet Newsgroup Services
----------------------------------------------------------
** SPEED ** RETENTION ** COMPLETION ** ANONYMITY **
----------------------------------------------------------
http://www.usenet.com

In article .com, "Davespectral" wrote:
The magnet system in this 3" dome midrange driver is inside the
voice-coil. I was thinking that the voice coil center might be a bit
deeper inside the driver than a typical dome tweeter, which it will be
crossed over to, on the same baffle. In other words, does anyone know
how far back the center of the voice-coil is from the rear of the front
flange? I could use some info on this because I'm using them with an
Eton 8-480, and I want to have the option to use a 1st order xover, so
I will be "time-aligning" all of the drivers so that the system has
that potential. Since I can't measure phase with LMS, I will be using
the voice coil centers for now.

You can use a tone or pink noise with a spectrum analyzer to find
centers.

greg

Stewart Pinkerton wrote:

First of all Stewart a Thank You for making sense of what Phil tries to
get across while he also writes all kinds of drivel.

On Sun, 21 May 2006 14:05:31 +0200, Peter Larsen
wrote:

Phil Allison wrote:

** Complete drivel.

The creation of force from current is instantaneous.

Instantaneus movemenet is not possible within Newtons laws, so it is
indeed complete drivel from Mr. Allisons keyboard.

The coil assembly accelerates immediately.

There is no such thing as immediate accelleration in this space-time
continuum.

With all the reactances in the equivalent diagramme of
a loudspeaker it is somewhat unlikely that instant
generation of sound should happen without being preceded
by a time delay.

We're talking a couple of nanoseconds at the most,
hardly relevant to audio!

I think wavelength comparison would make more sense and make it easier
to see the points than claims of instantanous action, such usually only
takes place immediately preceding an election ... O;-) ...

Anyway, to get to the facts, namely actual measurements of actual
loudspeaker units in an actual loudspeaker cabinet. The box is a stepped
baffle design, with the steps being 22 millimeters.

The treble unit is a Seas H225, the midrange a Seas 11-FM and the bass
unit a P17RCY. MLSSA measurements were kindly provided by Mr. Torben
Krogh on May 8, 1993. The acoustic centers of treble and midrange are in
the same plane, ie. the offset that came as a consequence of the chosen
board thickness, 22 millimeters, between mounting flanges is correct.
The bass however is measured to be 0.516 milliseconds, ie. 178
millimetres, late in spite of having its mounting flange 44 millimeters
in front of the mounting flange of the treble unit.

Scan of the original MLSSA printout available on request. My points are
proven with facts and Phil Allisons ramblings and assertions to the
effect that I should somehow be wrong are proven to be just that. If he
had been less busy looking for ways to assert that I was wrong and more
intent on finding out how I could possibly be right then a lot of wasted
time, effort and grief could have been spared.

Stewart Pinkerton | Music is Art - Audio is Engineering


Kind regards

Peter Larsen


--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

"Peter Larsen"

** **** OFF - NAZI CHARLATAN !!!!




** Complete drivel.

The creation of force from current is instantaneous.

Instantaneous movemenet is not possible within Newtons laws,


** But an * instantaneous force * IS - ****WIT !!!



The coil assembly accelerates immediately.

There is no such thing as immediate accelleration in this space-time
continuum.


** There IS and it is EVERYWHERE - you ASININE ****WIT.

Acceleration occurs * immediately * a force is applied to a mass.

Ever seen the formula: F = ma ????

Translates to: a = F / m

( Note lack of time delay )


Obviously the simple, physical laws discovered by Isaac Newton all those
centuries ago are COMPLETELY beyond a posturing, pig arrogant KNOB
TWIDDLING CHARLATAN & ****HEAD like Larsen.








......... Phil

Phil......you said there is no such thing as a woofer front plate
asshole. I have shown that there is. Get off this thread, and stay off
it scumbag.

Peter Larsen - Thanks for contributing. I'm glad to see that there is
someone else here who has at least worked with loudspeakers.

"Davespectral" wrote in message
oups.com...


** WARNING, WARNING - PUBLIC MENACE ON LOOSE .

Posing as yet another Google Groper ****wit !!!!



Phil....


** Get ****ed - Dave.


.... you said there is no such thing as a woofer front plate


** The rabid, autistic, criminal ****head is now totally delusional.

Needs to be shot on sight.

One bite form it could prove fatal.






........ Phil

PHIL ALISON: Throw your Kangaroo out of bed, and see a shrink asshole.
Put the .45 to your own head you miserable piece of crap.

"Peter Larsen"

** **** THE HELL OFF -

YOU ASININE KNOB TWIDDLING CHARLATAN !!!!!!!



Ever seen the formula: F = ma ????

Translates to: a = F / m

( Note lack of time delay )



** NOTE LACK OF SANE REPLY !!



Proof of measured time delay has been provided,


** LIKE HELL IT HAS !!


**** THE HELL OFF -

YOU ASININE KNOB TWIDDLING FAGGOT !






......... Phil

Davespectral" wrote in message
oups.com...


** WARNING, WARNING - PUBLIC MENACE ON LOOSE .

Posing as yet another Google Groper ****wit !!!!

This rabid, autistic, criminal ****head is now totally delusional.

Needs to be shot on sight.

One bite form it could prove fatal.





........ Phil

Davespectral" wrote in message
oups.com...


** WARNING, WARNING - PUBLIC MENACE ON LOOSE .

Posing as yet another Google Groper ****wit !!!!

This rabid, autistic, criminal ****head is now totally delusional.

Needs to be shot on sight immediately

One bite form it could prove fatal.




........ Phil

Phil Allison wrote:
Davespectral" wrote in message
oups.com...


** WARNING, WARNING - PUBLIC MENACE ON LOOSE .

Posing as yet another Google Groper ****wit !!!!

This rabid, autistic, criminal ****head is now totally delusional.

Needs to be shot on sight.

One bite form it could prove fatal.

....... Phil



PHIL: It is not fair to your daughter, to keep bringing her up.
LOL!!!

Davespectral" wrote in message
oups.com...


** WARNING, WARNING - PUBLIC MENACE ON LOOSE .

Posing as yet another Google Groper ****wit !!!!

This rabid, autistic, criminal schizophrenic is totally delusional.

Needs to be shot on sight !

One bite from it frothing mouth could prove fatal !!




........ Phil

On Thu, 25 May 2006 16:02:52 +0200, Peter Larsen
wrote:

Stewart Pinkerton wrote:

First of all Stewart a Thank You for making sense of what Phil tries to
get across while he also writes all kinds of drivel.

On Sun, 21 May 2006 14:05:31 +0200, Peter Larsen
wrote:

Phil Allison wrote:

** Complete drivel.

The creation of force from current is instantaneous.

Instantaneus movemenet is not possible within Newtons laws, so it is
indeed complete drivel from Mr. Allisons keyboard.

Actually, any drivel is generated by your failure to notice that no
movement is mentioned, only force. In this respect, Phil is quite
correct, the generation of the force occurs instantenously with the
arrival of the current. It does take the current some time to build
up,of course, but that's not the point.

The coil assembly accelerates immediately.

There is no such thing as immediate accelleration in this space-time
continuum.

Yes, there is. The cone doesn't have to be moving to experience
acceleration - although it's certainly impossible to *measure* the
acceleration until it *has* begun moving. A=f/m has no time parameter.

With all the reactances in the equivalent diagramme of
a loudspeaker it is somewhat unlikely that instant
generation of sound should happen without being preceded
by a time delay.

We're talking a couple of nanoseconds at the most,
hardly relevant to audio!

I think wavelength comparison would make more sense and make it easier
to see the points than claims of instantanous action, such usually only
takes place immediately preceding an election ... O;-) ...

You are conflating two arguments here. Sound is not generated until
the cone begins to move, which will be a few nanoseconds after the
current at the speaker terminals begins to rise, plus any delay caused
by the crossover, but such electrical effects equate to significantly
less than a millimetre of travel at the speed of sound.

Anyway, to get to the facts, namely actual measurements of actual
loudspeaker units in an actual loudspeaker cabinet. The box is a stepped
baffle design, with the steps being 22 millimeters.

The treble unit is a Seas H225, the midrange a Seas 11-FM and the bass
unit a P17RCY.

Ah good, a specific set of units!

MLSSA measurements were kindly provided by Mr. Torben
Krogh on May 8, 1993. The acoustic centers of treble and midrange are in
the same plane, ie. the offset that came as a consequence of the chosen
board thickness, 22 millimeters, between mounting flanges is correct.

Looks about right from the spec sheets.

The bass however is measured to be 0.516 milliseconds, ie. 178
millimetres, late in spite of having its mounting flange 44 millimeters
in front of the mounting flange of the treble unit.

That doesn't seem right at all. From the illustration, it looks like
the AC will be some 30mm behind the mounting flange, so the time
alignment dshould be pretty good. Were these measurements taken
without the crossover? If not, then you may have to make an allowance
for phase shift aka group delay from that source. Um, this isn't by
any chance a third-order crossover, is it?

Scan of the original MLSSA printout available on request. My points are
proven with facts and Phil Allisons ramblings and assertions to the
effect that I should somehow be wrong are proven to be just that.

Er no, the AC of a cone loudspeaker is most certainly *not* within the
voice coil.

If he
had been less busy looking for ways to assert that I was wrong and more
intent on finding out how I could possibly be right then a lot of wasted
time, effort and grief could have been spared.

Equally, had you considered other possibilities for your measurements
being the way they are, then a lot of wasted time, effort and grief
could have been spared.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Thu, 25 May 2006 18:10:29 +0200, Peter Larsen
wrote:


Anyway, to get to the facts, namely actual measurements of actual
loudspeaker units in an actual loudspeaker cabinet. The box is a
stepped baffle design, with the steps being 22 millimeters.

The treble unit is a Seas H225, the midrange a Seas 11-FM and
the bass unit a P17RCY.

Ah good, a specific set of units!

MLSSA measurements ....were kindly provided by Mr. Torben
Krogh on May 8, 1993. The acoustic centers of treble and midrange are in
the same plane, ie. the offset that came as a consequence of the chosen
board thickness, 22 millimeters, between mounting flanges is correct.

Looks about right from the spec sheets.

I just looked at the units and decided that 22 mm steps visually made
sense based on the asumption that Acoustic Centers would be
approximately at the voice coils.

False assumption, but the difference between the positions of the
acoustic centres comes out about the same in either case.

The bass however is measured to be 0.516 milliseconds, ie. 178
millimetres, late in spite of having its mounting flange 44
millimeters in front of the mounting flange of the treble unit.

That doesn't seem right at all. From the illustration, it looks like
the AC will be some 30mm behind the mounting flange, so the time
alignment should be pretty good.

My thougths exactly when going for that design in spite of the added
complexity.

Were these measurements taken without the crossover?

I can not see any spec saying this clearly, so I will have to say
possibly via the cross-over, what I can see is that the long "excess
delay" is with the bass unit inverted, with the midrange unit inverted
the bass is 0.224 milliseconds delayed compared to midrange and treble,
and they still match very well indeed.

I don't understand this. What do you mean by 'inverted' in this
context?

If not, then you may have to make an allowance
for phase shift aka group delay from that source. Um, this isn't by
any chance a third-order crossover, is it?

No, it is a stock IFM three way second order active.

OK, so we are lkeft with the question of whether time alignment
actually matters. Note that this was the 'next big thing' in the '80s,
but has mostly disappeared from the market.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

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