Active vs Passive Crossover design for Loud Speaker

[Jean-Pierre Dube]

I built these 4 way speakers back in my younger days.

Lots of good memories, and I'm now ready to dig them out of the basement and
revive them.

I need to replace the bass driver (maybe others) and I never really put the
crossovers (passive) together properly.

I'm thinking of going active crossover maybe 2 or 3 amps per box.

I'm looking for recommendations / postive experiences? I'm hoping a good kit
is available.

I'm not into electronics in a big way (don't own a scope) and I'm curious if
I'm in getting in over my head where after a few months of work I have
hundreds of dollars invested and I can't get the thing to work.

 

[Winfield Hill]

Jean-Pierre Dube wrote...

I'm not into electronics in a big way (don't own a scope) and I'm curious
if I'm in getting in over my head where after a few months of work I have
hundreds of dollars invested and I can't get the thing to work.

Go for it. And also go get a cheap used scope on eBay, so you
can have more fun and enhance your learning. For example, here
are a few nice analog scopes that'll be a good buy (or would
have, if I hadn't highlighted them. :>)

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3800486289
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3800463520
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3080035347

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3800316822
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2597964143

The latter is a nice digital-storage scope, which will surely
go much higher before finishing.

Thanks,
- Win

whill_at_picovolt-dot-com

 

[John Woodgate]

I read in sci.electronics.design that Jean-Pierre Dube
om>) about 'Active vs Passive Crossover design for Loud Speaker', on
Fri, 27 Feb 2004:

I built these 4 way speakers back in my younger days.

Lots of good memories, and I'm now ready to dig them out of the basement and
revive them.

I need to replace the bass driver (maybe others) and I never really put the
crossovers (passive) together properly.

I'm thinking of going active crossover maybe 2 or 3 amps per box.

For 4-ways, you really need four amps per box, otherwise you have to
have a mix of low-level and high-level crossovers, which is a real pain
to get right. The amplifiers don't all have to be high power; the powers
you need depend on your crossover frequencies, which in turn depend on
the useful frequency ranges of your drivers.

I'm looking for recommendations / postive experiences? I'm hoping a good kit
is available.

You are unlikely to get a ready-made kit that will work with your
drivers.

I'm not into electronics in a big way (don't own a scope) and I'm curious if
I'm in getting in over my head where after a few months of work I have
hundreds of dollars invested and I can't get the thing to work.

You don't need a scope, but you do need a good audio oscillator, with
accurate frequency calibration (or a separate counter) and an audio
voltmeter (not a digital multimeter), preferably with decibel read-out,
rather than volts.

I could let you have a basic crossover design with three Linkwitz-Riley
active filters, the mid-range being a wide-band band-pass, so really
four filters. You would need to duplicate that 'double' filter, with
different crossover frequencies, for your lower tweeter/upper mid-range
driver, making six filters is all. They are not complicated to build.

 

[Genome]

I built these 4 way speakers back in my younger days.

Lots of good memories, and I'm now ready to dig them out of the basement and
revive them.

I need to replace the bass driver (maybe others) and I never really put the
crossovers (passive) together properly.

I'm thinking of going active crossover maybe 2 or 3 amps per box.

I'm looking for recommendations / postive experiences? I'm hoping a good kit
is available.

I'm not into electronics in a big way (don't own a scope) and I'm curious if
I'm in getting in over my head where after a few months of work I have
hundreds of dollars invested and I can't get the thing to work.

Listen to proper music instead and enroll on a course for washing socks at
your local educational institute.

DNA

 

[Glenn Gundlach]

I read in sci.electronics.design that Jean-Pierre Dube
om>) about 'Active vs Passive Crossover design for Loud Speaker', on
Fri, 27 Feb 2004:

For 4-ways, you really need four amps per box, otherwise you have to
have a mix of low-level and high-level crossovers, which is a real pain
to get right. The amplifiers don't all have to be high power; the powers
you need depend on your crossover frequencies, which in turn depend on
the useful frequency ranges of your drivers.

You are unlikely to get a ready-made kit that will work with your
drivers.
You don't need a scope, but you do need a good audio oscillator, with
accurate frequency calibration (or a separate counter) and an audio
voltmeter (not a digital multimeter), preferably with decibel read-out,
rather than volts.

I could let you have a basic crossover design with three Linkwitz-Riley
active filters, the mid-range being a wide-band band-pass, so really
four filters. You would need to duplicate that 'double' filter, with
different crossover frequencies, for your lower tweeter/upper mid-range
driver, making six filters is all. They are not complicated to build.

You might consider getting CoolEdit (I believe it is still easily
available) You can generate sweeps and accurate fixed frequency
signals. I have not tried using it in 'record' while also generating
the tones so I can't say if that works. BUT if you have a second
computer, it would be a pretty nice test system. It can certainly be
used for relative measurements of an active filter system.
GG

 

[John Woodgate]

I read in sci.electronics.design that Glenn Gundlach
ogle.com>) about 'Active vs Passive Crossover design for Loud Speaker',

You might consider getting CoolEdit (I believe it is still easily
available)

No, it's been bought by Adobe and priced out of sight; $$$.

 

[Ben Bradley]

In sci.electronics.design, "Jean-Pierre Dube"

I built these 4 way speakers back in my younger days.

Lots of good memories, and I'm now ready to dig them out of the basement and
revive them.

I need to replace the bass driver (maybe others) and I never really put the
crossovers (passive) together properly.

I'm thinking of going active crossover maybe 2 or 3 amps per box.

I'm looking for recommendations / postive experiences? I'm hoping a good kit
is available.

There are surely active filter projects in old Speaker Builder and
Audio Amateur magazines (now audioxpress.com), but 'preassembled'
active crossovers are available from Rane [.com] as well as others.

I'm not into electronics in a big way (don't own a scope) and I'm curious if
I'm in getting in over my head where after a few months of work I have
hundreds of dollars invested and I can't get the thing to work.

Another good place to ask this is on rec.audio.tech.

 

[John Woodgate]

I read in sci.electronics.design that Ben Bradley <ben_nospam_bradley@mi
ndspring.example.com> wrote (in <ohf140l6hrrluffpo9osrreqdb0dq1v18k@4ax.
com>) about 'Active vs Passive Crossover design for Loud Speaker', on
Sat, 28 Feb 2004:

There are surely active filter projects in old Speaker Builder and
Audio Amateur magazines (now audioxpress.com), but 'preassembled' active
crossovers are available from Rane [.com] as well as others.

Crossover filters MUST be tailored to the characteristics of the
drivers. It's simply no use taking off-the-shelf designs or products and
using them with drivers not specified by the filter designers. There is
almost no chance of getting an acceptably uniform frequency response.

 

[Ban]

I read in sci.electronics.design that Ben Bradley

There are surely active filter projects in old Speaker Builder and
Audio Amateur magazines (now audioxpress.com), but 'preassembled'
active crossovers are available from Rane [.com] as well as others.

Crossover filters MUST be tailored to the characteristics of the
drivers. It's simply no use taking off-the-shelf designs or products
and using them with drivers not specified by the filter designers.
There is almost no chance of getting an acceptably uniform frequency
response.

John is right, I do the crossover design with a dedicated software tool
called Akabak, which lets you simulate the loudspeakers together with
passive components or active filters. But the learning curve for this tool
is quite challenging and you will need some assistance. There is a German
book available by the author Jörg Panzer (PC-workshop...), but I do not know
if there is an English translation. The simulation programm is not a bargain
either...

 

[Ben Bradley]

In sci.electronics.design, John Woodgate

I read in sci.electronics.design that Ben Bradley <ben_nospam_bradley@mi
ndspring.example.com> wrote (in <ohf140l6hrrluffpo9osrreqdb0dq1v18k@4ax.
com>) about 'Active vs Passive Crossover design for Loud Speaker', on
Sat, 28 Feb 2004:

There are surely active filter projects in old Speaker Builder and
Audio Amateur magazines (now audioxpress.com), but 'preassembled' active
crossovers are available from Rane [.com] as well as others.

Crossover filters MUST be tailored to the characteristics of the
drivers.

Oh, gee, I guess that's what all the knobs and switches on the
front panel are for...
http://www.rane.com/ac22b.html

It's simply no use taking off-the-shelf designs or products and
using them with drivers not specified by the filter designers. There is
almost no chance of getting an acceptably uniform frequency response.

One of the many features of an active crossover is its parameters
such as cutoff frequency and slope are more easily configurable than
changing out parts in a passive crossover.
I'd hope the original poster knows the simple method of scaling a
(active or passive R-C) filter design from one frequency to another by
changing capacitor valies in inverse proportion to the frequency
change (as explained in Active Filter Cookbook), but if not, maybe he
could learn it easily enough, or maybe he just did.
But you bring up an excellent point. If the OP wants to play around
with speakers (which was my impression), that's fine, but designing
and making truly good-sounding ones (as opposed to buying a kit for an
already designed, good-sounding speaker) does take quite a bit of
study and design effort. A four-way design such as the OP's would take
more than average effort to get sounding good, and I'd reccomend a
2-way or at most 3-way design with the 'better' drivers from places
such as madisound.com and partsexpress.com.

 

[Bryan Swadener]

I read in sci.electronics.design that Ben Bradley

There are surely active filter projects in old Speaker Builder and
Audio Amateur magazines (now audioxpress.com), but 'preassembled'
active crossovers are available from Rane [.com] as well as others.

Crossover filters MUST be tailored to the characteristics of the
drivers. It's simply no use taking off-the-shelf designs or products
and using them with drivers not specified by the filter designers.
There is almost no chance of getting an acceptably uniform frequency
response.

John is right, I do the crossover design with a dedicated software tool
called Akabak, which lets you simulate the loudspeakers together with
passive components or active filters. But the learning curve for this tool
is quite challenging and you will need some assistance. There is a German
book available by the author Jörg Panzer (PC-workshop...), but I do not know
if there is an English translation. The simulation programm is not a bargain
either...

I'm thinking that a way to characterize the response of a speaker element
would be to feed it white noise (or just sweep it with an oscillator), and
observe the response using a *good* quality microphone as the sensing
element. The response of the amplifier driving the speaker as well as the
preamplifier connected to the microphone would have to be taken into
consideration. After that is done, you would then know what sort of response
to tailor into your active (or passive) crossover.
Bryan

 

[Kalman Rubinson]

On Sat, 28 Feb 2004 13:57:49 -0500, Ben Bradley
that's what all the knobs and switches on the
front panel are for...
http://www.rane.com/ac22b.html

Nice but inadequate. Only one slope and no bandpass or phase
corrections.

Kal

 

[John Woodgate]

I read in sci.electronics.design that Bryan Swadener
02>) about 'Active vs Passive Crossover design for Loud Speaker', on
Sat, 28 Feb 2004:

I'm thinking that a way to characterize the response of a speaker
element would be to feed it white noise (or just sweep it with an
oscillator), and observe the response using a *good* quality microphone
as the sensing element. The response of the amplifier driving the
speaker as well as the preamplifier connected to the microphone would
have to be taken into consideration. After that is done, you would then
know what sort of response to tailor into your active (or passive)
crossover. Bryan

Well, you just reinvented the methods used for the last 100 years or
nearly. But you have to do the measurements in anechoic conditions
because reflections distort the measured response very badly. That means
either doing the measurements with the loudspeaker and microphone
suspended at least 10 m above ground level in free air, or in a large
anechoic room, which is in the white elephant class for cost of
ownership.

 

[Bryan Swadener]

"John Woodgate" elaborated:

I read in sci.electronics.design that Bryan Swadener
02>) about 'Active vs Passive Crossover design for Loud Speaker', on
Sat, 28 Feb 2004:


Well, you just reinvented the methods used for the last 100 years or
nearly. But you have to do the measurements in anechoic conditions
because reflections distort the measured response very badly. That means
either doing the measurements with the loudspeaker and microphone
suspended at least 10 m above ground level in free air, or in a large
anechoic room, which is in the white elephant class for cost of
ownership.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

Of course. However, the results from such a testing environment wouldn't
hold true in the environment in which the speaker will be used.
Bryan

 

[John Woodgate]

I read in sci.electronics.design that Bryan Swadener
) about 'Active vs Passive Crossover design for Loud Speaker', on Mon, 1
Mar 2004:

Of course. However, the results from such a testing environment
wouldn't hold true in the environment in which the speaker will be used.

They would hold for the direct sound, and for satisfactory sound quality
the listeners must be in the direct sound field. Haas or precedence
effect substantially reduces the effect of indirect sound.