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  #95   Report Post  
Tony Pearce
 
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Default Speakers testing

"Svante" wrote in message
om...
So, 2.5 way would have two speakers playing bass, of which one also
manages the midrange? Have you ever seen how such a crossover filter
is designed?

It's just two separate low pass filters, one for the bass and another for
the bass/mid, and a high pass for the tweeter. Nothing special required,
other than to match levels.

TonyP.



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  #96   Report Post  
Tony Pearce
 
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Default Speakers testing

"Svante" wrote in message
om...
So, 2.5 way would have two speakers playing bass, of which one also
manages the midrange? Have you ever seen how such a crossover filter
is designed?

It's just two separate low pass filters, one for the bass and another for
the bass/mid, and a high pass for the tweeter. Nothing special required,
other than to match levels.

TonyP.



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  #97   Report Post  
Tony Pearce
 
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Default Speakers testing

"Svante" wrote in message
om...
So, 2.5 way would have two speakers playing bass, of which one also
manages the midrange? Have you ever seen how such a crossover filter
is designed?

It's just two separate low pass filters, one for the bass and another for
the bass/mid, and a high pass for the tweeter. Nothing special required,
other than to match levels.

TonyP.



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  #98   Report Post  
Dick Pierce
 
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Default Speakers testing
"Tony Pearce" wrote in message . au...
"Svante" wrote in message
om...
So, 2.5 way would have two speakers playing bass, of which one also
manages the midrange? Have you ever seen how such a crossover filter
is designed?

It's just two separate low pass filters, one for the bass and another for
the bass/mid, and a high pass for the tweeter. Nothing special required,
other than to match levels.

That's one way to do it. Another is to cascade two low-pass filters.
The first, say a second order low pass at, oh 2500 Hz, drivers the
main mid-bass driver and the input to a second low-pass filter set
to something lower, like 200 Hz.
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  #99   Report Post  
Dick Pierce
 
Posts: n/a
Default Speakers testing
"Tony Pearce" wrote in message . au...
"Svante" wrote in message
om...
So, 2.5 way would have two speakers playing bass, of which one also
manages the midrange? Have you ever seen how such a crossover filter
is designed?

It's just two separate low pass filters, one for the bass and another for
the bass/mid, and a high pass for the tweeter. Nothing special required,
other than to match levels.

That's one way to do it. Another is to cascade two low-pass filters.
The first, say a second order low pass at, oh 2500 Hz, drivers the
main mid-bass driver and the input to a second low-pass filter set
to something lower, like 200 Hz.
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  #100   Report Post  
Dick Pierce
 
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Default Speakers testing
"Tony Pearce" wrote in message . au...
"Svante" wrote in message
om...
So, 2.5 way would have two speakers playing bass, of which one also
manages the midrange? Have you ever seen how such a crossover filter
is designed?

It's just two separate low pass filters, one for the bass and another for
the bass/mid, and a high pass for the tweeter. Nothing special required,
other than to match levels.

That's one way to do it. Another is to cascade two low-pass filters.
The first, say a second order low pass at, oh 2500 Hz, drivers the
main mid-bass driver and the input to a second low-pass filter set
to something lower, like 200 Hz.
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  #107   Report Post  
Dick Pierce
 
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Default Speakers testing
(Svante) wrote in message . com...
 (Dick Pierce) wrote in message om...

That's one way to do it. Another is to cascade two low-pass filters.
The first, say a second order low pass at, oh 2500 Hz, drivers the
main mid-bass driver and the input to a second low-pass filter set
to something lower, like 200 Hz.

Would not those approaches give problems with the frequency response
and electrical impedance? Below the lower crossover frequency we would
have two drivers playing = + 6dB and also an impedance of half the
electrical impedance of one driver.

First, we would you tthink the electrical impedance issue is an
important one? Remember that we're driving our speakers from
pretty good approximations of voltage sources, and we are designing
our speakers (hopefully) to have flat frequency when so driven.

As to the frequency response problem, consider one scenario where
this method actually solves a problem. Depending upon the baffle
dimensions, below a certain frequency, one loses about 6 dB of
axial output due to what's called the baffle diffraction effect.
This is a result of the dispersion going from hemispherical at
higher frequencies to spherical at lower frequencies. You get,
essentially, a step in the response where below this frequency
your output is lower than above.

Fine, so you arrange your "2 1/2" way crossover such that both
drivers are operating below that frequency, and only one is working
above. You can, with careful design, thus arrantge so that the step
in output of the speaker compensates for the roughly opposite step
in response due to diffraction loss.

Now, if you arrange the crossover such that the narrower band driver
and its low-pass element is in parallel with the wider band driver,
indeed you WILL get a lower impedance at lower frequencies, but,
again, pick your points right (i.e., design your system as a system,
a novel concept to many speaker "designers"), and you deal with the
fact that at these lower frequencies, the overall impedance of the
driovers are higher anyway, due to the increase impedance around
resonance. The impedance "problem" is thus not that much of a problem.

If you're worried about impedance, use drivers of an appropriate
impedance to work in the design to begin with. Also, one can
arrange system such the the drivers are driven in series, with
a pass element (like a capacitor) around one of them that provides
the low-pass function for that driver.
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  #108   Report Post  
Dick Pierce
 
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Default Speakers testing
(Svante) wrote in message . com...
 (Dick Pierce) wrote in message om...

That's one way to do it. Another is to cascade two low-pass filters.
The first, say a second order low pass at, oh 2500 Hz, drivers the
main mid-bass driver and the input to a second low-pass filter set
to something lower, like 200 Hz.

Would not those approaches give problems with the frequency response
and electrical impedance? Below the lower crossover frequency we would
have two drivers playing = + 6dB and also an impedance of half the
electrical impedance of one driver.

First, we would you tthink the electrical impedance issue is an
important one? Remember that we're driving our speakers from
pretty good approximations of voltage sources, and we are designing
our speakers (hopefully) to have flat frequency when so driven.

As to the frequency response problem, consider one scenario where
this method actually solves a problem. Depending upon the baffle
dimensions, below a certain frequency, one loses about 6 dB of
axial output due to what's called the baffle diffraction effect.
This is a result of the dispersion going from hemispherical at
higher frequencies to spherical at lower frequencies. You get,
essentially, a step in the response where below this frequency
your output is lower than above.

Fine, so you arrange your "2 1/2" way crossover such that both
drivers are operating below that frequency, and only one is working
above. You can, with careful design, thus arrantge so that the step
in output of the speaker compensates for the roughly opposite step
in response due to diffraction loss.

Now, if you arrange the crossover such that the narrower band driver
and its low-pass element is in parallel with the wider band driver,
indeed you WILL get a lower impedance at lower frequencies, but,
again, pick your points right (i.e., design your system as a system,
a novel concept to many speaker "designers"), and you deal with the
fact that at these lower frequencies, the overall impedance of the
driovers are higher anyway, due to the increase impedance around
resonance. The impedance "problem" is thus not that much of a problem.

If you're worried about impedance, use drivers of an appropriate
impedance to work in the design to begin with. Also, one can
arrange system such the the drivers are driven in series, with
a pass element (like a capacitor) around one of them that provides
the low-pass function for that driver.
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  #109   Report Post  
Dick Pierce
 
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Default Speakers testing
(Svante) wrote in message . com...
 (Dick Pierce) wrote in message om...

That's one way to do it. Another is to cascade two low-pass filters.
The first, say a second order low pass at, oh 2500 Hz, drivers the
main mid-bass driver and the input to a second low-pass filter set
to something lower, like 200 Hz.

Would not those approaches give problems with the frequency response
and electrical impedance? Below the lower crossover frequency we would
have two drivers playing = + 6dB and also an impedance of half the
electrical impedance of one driver.

First, we would you tthink the electrical impedance issue is an
important one? Remember that we're driving our speakers from
pretty good approximations of voltage sources, and we are designing
our speakers (hopefully) to have flat frequency when so driven.

As to the frequency response problem, consider one scenario where
this method actually solves a problem. Depending upon the baffle
dimensions, below a certain frequency, one loses about 6 dB of
axial output due to what's called the baffle diffraction effect.
This is a result of the dispersion going from hemispherical at
higher frequencies to spherical at lower frequencies. You get,
essentially, a step in the response where below this frequency
your output is lower than above.

Fine, so you arrange your "2 1/2" way crossover such that both
drivers are operating below that frequency, and only one is working
above. You can, with careful design, thus arrantge so that the step
in output of the speaker compensates for the roughly opposite step
in response due to diffraction loss.

Now, if you arrange the crossover such that the narrower band driver
and its low-pass element is in parallel with the wider band driver,
indeed you WILL get a lower impedance at lower frequencies, but,
again, pick your points right (i.e., design your system as a system,
a novel concept to many speaker "designers"), and you deal with the
fact that at these lower frequencies, the overall impedance of the
driovers are higher anyway, due to the increase impedance around
resonance. The impedance "problem" is thus not that much of a problem.

If you're worried about impedance, use drivers of an appropriate
impedance to work in the design to begin with. Also, one can
arrange system such the the drivers are driven in series, with
a pass element (like a capacitor) around one of them that provides
the low-pass function for that driver.
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  #110   Report Post  
Drew Eckhardt
 
Posts: n/a
Default Speakers testing
In article ,
Svante wrote:
It's just two separate low pass filters, one for the bass and another for
the bass/mid

That's one way to do it. Another is to cascade two low-pass filters.
The first, say a second order low pass at, oh 2500 Hz, drivers the
main mid-bass driver and the input to a second low-pass filter set
to something lower, like 200 Hz.

Would not those approaches give problems with the frequency response
and electrical impedance?

Nope.

Below the lower crossover frequency we would
have two drivers playing = + 6dB

In an anechoic environment on-axis response increases 6dB once the sound
waves are short enough. It's a gradual function having about 1dB of effect for
wavelengths 3X baffle width and the full 6dB once they're 1/5th width.

This is compensated for by either a low frequency boost as in the .5 way speaker
or high frequency cut.

In-room the number is probably more like 3-4.5dB, although the bass driver can
be padded down to compensate.

and also an impedance of half the
electrical impedance of one driver.

The amp won't care.

--
a href="http://www.poohsticks.org/drew/"Home Page/a
Life is a terminal sexually transmitted disease.
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  #111   Report Post  
Drew Eckhardt
 
Posts: n/a
Default Speakers testing
In article ,
Svante wrote:
It's just two separate low pass filters, one for the bass and another for
the bass/mid

That's one way to do it. Another is to cascade two low-pass filters.
The first, say a second order low pass at, oh 2500 Hz, drivers the
main mid-bass driver and the input to a second low-pass filter set
to something lower, like 200 Hz.

Would not those approaches give problems with the frequency response
and electrical impedance?

Nope.

Below the lower crossover frequency we would
have two drivers playing = + 6dB

In an anechoic environment on-axis response increases 6dB once the sound
waves are short enough. It's a gradual function having about 1dB of effect for
wavelengths 3X baffle width and the full 6dB once they're 1/5th width.

This is compensated for by either a low frequency boost as in the .5 way speaker
or high frequency cut.

In-room the number is probably more like 3-4.5dB, although the bass driver can
be padded down to compensate.

and also an impedance of half the
electrical impedance of one driver.

The amp won't care.

--
a href="http://www.poohsticks.org/drew/"Home Page/a
Life is a terminal sexually transmitted disease.
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  #112   Report Post  
Drew Eckhardt
 
Posts: n/a
Default Speakers testing
In article ,
Svante wrote:
It's just two separate low pass filters, one for the bass and another for
the bass/mid

That's one way to do it. Another is to cascade two low-pass filters.
The first, say a second order low pass at, oh 2500 Hz, drivers the
main mid-bass driver and the input to a second low-pass filter set
to something lower, like 200 Hz.

Would not those approaches give problems with the frequency response
and electrical impedance?

Nope.

Below the lower crossover frequency we would
have two drivers playing = + 6dB

In an anechoic environment on-axis response increases 6dB once the sound
waves are short enough. It's a gradual function having about 1dB of effect for
wavelengths 3X baffle width and the full 6dB once they're 1/5th width.

This is compensated for by either a low frequency boost as in the .5 way speaker
or high frequency cut.

In-room the number is probably more like 3-4.5dB, although the bass driver can
be padded down to compensate.

and also an impedance of half the
electrical impedance of one driver.

The amp won't care.

--
a href="http://www.poohsticks.org/drew/"Home Page/a
Life is a terminal sexually transmitted disease.
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  #113   Report Post  
Svante
 
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Default Speakers testing
(Dick Pierce) wrote in message om...
 (Svante) wrote in message . com...
 (Dick Pierce) wrote in message om...

That's one way to do it. Another is to cascade two low-pass filters.
The first, say a second order low pass at, oh 2500 Hz, drivers the
main mid-bass driver and the input to a second low-pass filter set
to something lower, like 200 Hz.

Would not those approaches give problems with the frequency response
and electrical impedance? Below the lower crossover frequency we would
have two drivers playing = + 6dB and also an impedance of half the
electrical impedance of one driver.

First, we would you tthink the electrical impedance issue is an
important one? Remember that we're driving our speakers from
pretty good approximations of voltage sources, and we are designing
our speakers (hopefully) to have flat frequency when so driven.

Yes, sure, but two 4 ohm speakers in parallel would perhaps give
problems with the current driving capabilities. So, I guess 4 ohm
speakers are out of the question, which perhaps is no big deal, I
would agree to that.

As to the frequency response problem, consider one scenario where
this method actually solves a problem. Depending upon the baffle
dimensions, below a certain frequency, one loses about 6 dB of
axial output due to what's called the baffle diffraction effect.
This is a result of the dispersion going from hemispherical at
higher frequencies to spherical at lower frequencies. You get,
essentially, a step in the response where below this frequency
your output is lower than above.

Like you and the other posters pointed out this appears like a good
way to USE the effect, rather than having to compensate for it. Smart!
One would have to select the crossover frequency carefully of course.
I forgot about the diffraction effect, or possibly saw it as a
separate issue, which it need not be.

Fine, so you arrange your "2 1/2" way crossover such that both
drivers are operating below that frequency, and only one is working
above. You can, with careful design, thus arrantge so that the step
in output of the speaker compensates for the roughly opposite step
in response due to diffraction loss.

Now, if you arrange the crossover such that the narrower band driver
and its low-pass element is in parallel with the wider band driver,
indeed you WILL get a lower impedance at lower frequencies, but,
again, pick your points right (i.e., design your system as a system,
a novel concept to many speaker "designers"),

:-)

and you deal with the
fact that at these lower frequencies, the overall impedance of the
driovers are higher anyway, due to the increase impedance around
resonance. The impedance "problem" is thus not that much of a problem.


Agree, but it is a *potential* problem that has to be dealt with.

If you're worried about impedance, use drivers of an appropriate
impedance to work in the design to begin with. Also, one can
arrange system such the the drivers are driven in series, with
a pass element (like a capacitor) around one of them that provides
the low-pass function for that driver.
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  #114   Report Post  
Svante
 
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Default Speakers testing
(Dick Pierce) wrote in message om...
 (Svante) wrote in message . com...
 (Dick Pierce) wrote in message om...

That's one way to do it. Another is to cascade two low-pass filters.
The first, say a second order low pass at, oh 2500 Hz, drivers the
main mid-bass driver and the input to a second low-pass filter set
to something lower, like 200 Hz.

Would not those approaches give problems with the frequency response
and electrical impedance? Below the lower crossover frequency we would
have two drivers playing = + 6dB and also an impedance of half the
electrical impedance of one driver.

First, we would you tthink the electrical impedance issue is an
important one? Remember that we're driving our speakers from
pretty good approximations of voltage sources, and we are designing
our speakers (hopefully) to have flat frequency when so driven.

Yes, sure, but two 4 ohm speakers in parallel would perhaps give
problems with the current driving capabilities. So, I guess 4 ohm
speakers are out of the question, which perhaps is no big deal, I
would agree to that.

As to the frequency response problem, consider one scenario where
this method actually solves a problem. Depending upon the baffle
dimensions, below a certain frequency, one loses about 6 dB of
axial output due to what's called the baffle diffraction effect.
This is a result of the dispersion going from hemispherical at
higher frequencies to spherical at lower frequencies. You get,
essentially, a step in the response where below this frequency
your output is lower than above.

Like you and the other posters pointed out this appears like a good
way to USE the effect, rather than having to compensate for it. Smart!
One would have to select the crossover frequency carefully of course.
I forgot about the diffraction effect, or possibly saw it as a
separate issue, which it need not be.

Fine, so you arrange your "2 1/2" way crossover such that both
drivers are operating below that frequency, and only one is working
above. You can, with careful design, thus arrantge so that the step
in output of the speaker compensates for the roughly opposite step
in response due to diffraction loss.

Now, if you arrange the crossover such that the narrower band driver
and its low-pass element is in parallel with the wider band driver,
indeed you WILL get a lower impedance at lower frequencies, but,
again, pick your points right (i.e., design your system as a system,
a novel concept to many speaker "designers"),

:-)

and you deal with the
fact that at these lower frequencies, the overall impedance of the
driovers are higher anyway, due to the increase impedance around
resonance. The impedance "problem" is thus not that much of a problem.


Agree, but it is a *potential* problem that has to be dealt with.

If you're worried about impedance, use drivers of an appropriate
impedance to work in the design to begin with. Also, one can
arrange system such the the drivers are driven in series, with
a pass element (like a capacitor) around one of them that provides
the low-pass function for that driver.
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  #115   Report Post  
Svante
 
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Default Speakers testing
(Dick Pierce) wrote in message om...
 (Svante) wrote in message . com...
 (Dick Pierce) wrote in message om...

That's one way to do it. Another is to cascade two low-pass filters.
The first, say a second order low pass at, oh 2500 Hz, drivers the
main mid-bass driver and the input to a second low-pass filter set
to something lower, like 200 Hz.

Would not those approaches give problems with the frequency response
and electrical impedance? Below the lower crossover frequency we would
have two drivers playing = + 6dB and also an impedance of half the
electrical impedance of one driver.

First, we would you tthink the electrical impedance issue is an
important one? Remember that we're driving our speakers from
pretty good approximations of voltage sources, and we are designing
our speakers (hopefully) to have flat frequency when so driven.

Yes, sure, but two 4 ohm speakers in parallel would perhaps give
problems with the current driving capabilities. So, I guess 4 ohm
speakers are out of the question, which perhaps is no big deal, I
would agree to that.

As to the frequency response problem, consider one scenario where
this method actually solves a problem. Depending upon the baffle
dimensions, below a certain frequency, one loses about 6 dB of
axial output due to what's called the baffle diffraction effect.
This is a result of the dispersion going from hemispherical at
higher frequencies to spherical at lower frequencies. You get,
essentially, a step in the response where below this frequency
your output is lower than above.

Like you and the other posters pointed out this appears like a good
way to USE the effect, rather than having to compensate for it. Smart!
One would have to select the crossover frequency carefully of course.
I forgot about the diffraction effect, or possibly saw it as a
separate issue, which it need not be.

Fine, so you arrange your "2 1/2" way crossover such that both
drivers are operating below that frequency, and only one is working
above. You can, with careful design, thus arrantge so that the step
in output of the speaker compensates for the roughly opposite step
in response due to diffraction loss.

Now, if you arrange the crossover such that the narrower band driver
and its low-pass element is in parallel with the wider band driver,
indeed you WILL get a lower impedance at lower frequencies, but,
again, pick your points right (i.e., design your system as a system,
a novel concept to many speaker "designers"),

:-)

and you deal with the
fact that at these lower frequencies, the overall impedance of the
driovers are higher anyway, due to the increase impedance around
resonance. The impedance "problem" is thus not that much of a problem.


Agree, but it is a *potential* problem that has to be dealt with.

If you're worried about impedance, use drivers of an appropriate
impedance to work in the design to begin with. Also, one can
arrange system such the the drivers are driven in series, with
a pass element (like a capacitor) around one of them that provides
the low-pass function for that driver.
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  #116   Report Post  
Tony Pearce
 
Posts: n/a
Default Speakers testing

"Svante" wrote in message
om...
Yes, sure, but two 4 ohm speakers in parallel would perhaps give
problems with the current driving capabilities. So, I guess 4 ohm
speakers are out of the question, which perhaps is no big deal, I
would agree to that.

Actually two by 4 ohm drivers in parallel (2 ohms nominal) are not that
uncommon unfortunately. The manufactuers preferring to advertise a higher
sensitivity (for 2.83V input), rather than worry whether your amp can drive
them or not. There is still a myth that drivers should never be conected in
series, even among speaker designers. As Dick points out, you can even
connect drivers in a "2.5 way" system in series if you want.

TonyP.



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  #117   Report Post  
Tony Pearce
 
Posts: n/a
Default Speakers testing

"Svante" wrote in message
om...
Yes, sure, but two 4 ohm speakers in parallel would perhaps give
problems with the current driving capabilities. So, I guess 4 ohm
speakers are out of the question, which perhaps is no big deal, I
would agree to that.

Actually two by 4 ohm drivers in parallel (2 ohms nominal) are not that
uncommon unfortunately. The manufactuers preferring to advertise a higher
sensitivity (for 2.83V input), rather than worry whether your amp can drive
them or not. There is still a myth that drivers should never be conected in
series, even among speaker designers. As Dick points out, you can even
connect drivers in a "2.5 way" system in series if you want.

TonyP.



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  #118   Report Post  
Tony Pearce
 
Posts: n/a
Default Speakers testing

"Svante" wrote in message
om...
Yes, sure, but two 4 ohm speakers in parallel would perhaps give
problems with the current driving capabilities. So, I guess 4 ohm
speakers are out of the question, which perhaps is no big deal, I
would agree to that.

Actually two by 4 ohm drivers in parallel (2 ohms nominal) are not that
uncommon unfortunately. The manufactuers preferring to advertise a higher
sensitivity (for 2.83V input), rather than worry whether your amp can drive
them or not. There is still a myth that drivers should never be conected in
series, even among speaker designers. As Dick points out, you can even
connect drivers in a "2.5 way" system in series if you want.

TonyP.



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  #119   Report Post  
Michael McKelvy
 
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Default Speakers testing

"Stewart Pinkerton" wrote in message
...
On 18 Dec 2003 09:57:24 -0800, (Svante)
wrote:

"Tony Pearce" wrote in message
. au...

You still miss the point I was making. The tweeter frequencies can be
easily
measured using MLS gating systems. The problem is with multi - woofer
systems eg. D'Appolito designs commonly available these days. Near
field
measurements are made on one woofer, then MLS measurements are made for
high
frequencies. If the room height is small as it usually is, then errors
will
occur when combining near field measurements at frequencies lower than
can
be gated.

Hmm, in that case I still fail to understand what you mean. Could you
enlighten me on what a D'Appolito design is (I must confess I don't
know).

It's a vertical array with twin bass/mids and a third-order crossover,
and it's noted for a very smooth vertical dispersion pattern around
the crossover frequency. Many such 'WTW' designs are around today, but
not all are true d'Appolito arrays. Many are so-called '2.5 way'
designs, which are conventional single bass/mid designs at the tweeter
crossover point. Invented by audio legend Joe d'Apollito, hence the
name.

A minor correction. Mr. d'Appolito does not claim he invented the MTm or if
you prefer, the WTW design. This was his comment in an interview I read,
I'm sorry, but I can't recall who he said was the first. There is no doubt
that he popularized it. I recall in another article that he now prefers
implementing these designs with 4th order xovers. If I can find the source
of these atrributions I'll post it. Most likely SB.

Are you speaking about a closed box or bass-reflex.

Can be either, as the key element is the crossover region from
bass/mids to tweeter, although most commercial designs seem to be
sealed.

I realise that the time between direct sound and the first reflection
will determine the lowest frequency that can be used when gating an
impulse response, but I fail to see why this would make combination of
this and near-field measurement hard. Do you mean that it would force
us to use the near-field measurement at a too high frequency?

I believe that's what he's getting at.
--

Stewart Pinkerton | Music is Art - Audio is Engineering


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  #120   Report Post  
Michael McKelvy
 
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Default Speakers testing

"Stewart Pinkerton" wrote in message
...
On 18 Dec 2003 09:57:24 -0800, (Svante)
wrote:

"Tony Pearce" wrote in message
. au...

You still miss the point I was making. The tweeter frequencies can be
easily
measured using MLS gating systems. The problem is with multi - woofer
systems eg. D'Appolito designs commonly available these days. Near
field
measurements are made on one woofer, then MLS measurements are made for
high
frequencies. If the room height is small as it usually is, then errors
will
occur when combining near field measurements at frequencies lower than
can
be gated.

Hmm, in that case I still fail to understand what you mean. Could you
enlighten me on what a D'Appolito design is (I must confess I don't
know).

It's a vertical array with twin bass/mids and a third-order crossover,
and it's noted for a very smooth vertical dispersion pattern around
the crossover frequency. Many such 'WTW' designs are around today, but
not all are true d'Appolito arrays. Many are so-called '2.5 way'
designs, which are conventional single bass/mid designs at the tweeter
crossover point. Invented by audio legend Joe d'Apollito, hence the
name.

A minor correction. Mr. d'Appolito does not claim he invented the MTm or if
you prefer, the WTW design. This was his comment in an interview I read,
I'm sorry, but I can't recall who he said was the first. There is no doubt
that he popularized it. I recall in another article that he now prefers
implementing these designs with 4th order xovers. If I can find the source
of these atrributions I'll post it. Most likely SB.

Are you speaking about a closed box or bass-reflex.

Can be either, as the key element is the crossover region from
bass/mids to tweeter, although most commercial designs seem to be
sealed.

I realise that the time between direct sound and the first reflection
will determine the lowest frequency that can be used when gating an
impulse response, but I fail to see why this would make combination of
this and near-field measurement hard. Do you mean that it would force
us to use the near-field measurement at a too high frequency?

I believe that's what he's getting at.
--

Stewart Pinkerton | Music is Art - Audio is Engineering


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