Calcutlating adaption of loudspeaker filter circuit

R

Rene

Guest
Hello to all of You,

Some time ago I decided to built myself a good speaker set for my computer.
I have already built two Visaton CT Center 81's
(http://www.visaton.com/en/bauvorschlaege/computer/856/index.html), they
sound great but need a subwoofer which is the next I will build (this one
http://www.visaton.com/en/bauvorschlaege/subwoofer/564/index.html), together
with 3 more of these little speakers (their looks are even better then their
sound, though one might think otherwise when looking at the one on the
site - I also did not use the grid).

I also wanted to build my own "5.2" amplifier (two separate amps for the
speakers in the subwoofer, that's what I meant with the .2 and the ""'s)
based on not-too-expensive integrated amplifiers but now I managed to lay my
hands on a Technics 5.1 home cinema receiver for much less money than the
diy option would cost (the sub output is passive so I will have to build an
amplifier for that, but that's no problem).

However, now I have another problem. The receiver wants surround speakers of
at least 6 ohms where the CT Center 81 is only 4. In the past there was a CT
Center 80, the difference was in the filter that was less sophisticated but
also had an impedance of 6 ohms. I could of course use that design to built
into my speakers but I think it would not improve sound quality (it won't be
just for fun that Visaton changed the design).

Unfortunately I have not much knowledge about the math behind filters. I was
hoping to find someone in this group able and of course willing to have a
look at the schematics and the technical data I have put at the bottom of my
post and see of he/she would know how I might change the values of some
components in my current filters.

Many thanks in advance!

Yours sincerely,
Rene

The filter of my speakers is:
http://www.visaton.com/bilder/weichen/gross/ct_center81_w.gif. The old
version can be seen on
http://www.visaton.com/bilder/weichen/gross/ct_center80_w.gif but as I said,
I would rather use the first one.

Data from the SC5 tweeter are here:

Nominal power handling with high pass 60 Watt (12 dB/Okt.; 6000 Hz)
Peak power handling with high pass 100 Watt (12 dB/Okt.; 6000 Hz)
Nominal impedance 8 Ohm
Frequency response (-10 dB) 1500 - 22000 Hz
Mean sound pressure level 90 dB (1W/1m)
Resonance frequency fs 2500 Hz
Magnetic induction 0,7 Tesla
Magnetic flux 33 ľWeber
Voice coil diameter 1,3 cm
Height of winding 0,18 cm
Cutout diameter 4,8 cm
Net weight 0,098 kg
D.C. resistance Rdc 6,2 Ohm
Inductance of the voice coil L 0,08 mH

And here are the data of the F8SC "woofer":

Nominal power handling 20 Watt
Peak power handling 30 Watt
Nominal impedance 8 Ohm
Frequency response (-10 dB) 80 - 15000 Hz
Mean sound pressure level 82 dB (1W/1m)
Maximum cone displacement 5 mm
Resonance frequency fs 103 Hz
Magnetic induction 0,8 Tesla
Magnetic flux 150 ľWeber
Height of front pole-plate 3 mm
Voice coil diameter 2 cm
Height of winding 0,45 cm
Cutout diameter 7,6 cm
Net weight 0,25 kg
D.C. resistance Rdc 7,7 Ohm
Mechanical Q factor Qms 3,03
Electrical Q factor Qes 1,52
Total Q factor Qts 1,01
Equivalent volume Vas 1,4 l
Effective piston area Sd 30 cm2
Dynamically moved mass Mms 2,2 g
Force factor Bxl 2,69 T ˇ m
Inductance of the voice coil L 0,35 mH
 
"Rene" <my.name@is.nobody> wrote in message
news:k_Dlk.114274$Lc6.24953@newsfe18.ams2...
Hello to all of You,

Some time ago I decided to built myself a good speaker set for my
computer. I have already built two Visaton CT Center 81's
(http://www.visaton.com/en/bauvorschlaege/computer/856/index.html), they
sound great but need a subwoofer which is the next I will build (this one
http://www.visaton.com/en/bauvorschlaege/subwoofer/564/index.html),
together with 3 more of these little speakers (their looks are even better
then their sound, though one might think otherwise when looking at the one
on the site - I also did not use the grid).

I also wanted to build my own "5.2" amplifier (two separate amps for the
speakers in the subwoofer, that's what I meant with the .2 and the ""'s)
based on not-too-expensive integrated amplifiers but now I managed to lay
my hands on a Technics 5.1 home cinema receiver for much less money than
the diy option would cost (the sub output is passive so I will have to
build an amplifier for that, but that's no problem).

However, now I have another problem. The receiver wants surround speakers
of at least 6 ohms where the CT Center 81 is only 4. In the past there was
a CT Center 80, the difference was in the filter that was less
sophisticated but also had an impedance of 6 ohms. I could of course use
that design to built into my speakers but I think it would not improve
sound quality (it won't be just for fun that Visaton changed the design).

Unfortunately I have not much knowledge about the math behind filters. I
was hoping to find someone in this group able and of course willing to
have a look at the schematics and the technical data I have put at the
bottom of my post and see of he/she would know how I might change the
values of some components in my current filters.

Many thanks in advance!

Yours sincerely,
Rene

The filter of my speakers is:
http://www.visaton.com/bilder/weichen/gross/ct_center81_w.gif. The old
version can be seen on
http://www.visaton.com/bilder/weichen/gross/ct_center80_w.gif but as I
said, I would rather use the first one.

Data from the SC5 tweeter are here:

Nominal power handling with high pass 60 Watt (12 dB/Okt.; 6000 Hz)
Peak power handling with high pass 100 Watt (12 dB/Okt.; 6000 Hz)
Nominal impedance 8 Ohm
Frequency response (-10 dB) 1500 - 22000 Hz
Mean sound pressure level 90 dB (1W/1m)
Resonance frequency fs 2500 Hz
Magnetic induction 0,7 Tesla
Magnetic flux 33 ľWeber
Voice coil diameter 1,3 cm
Height of winding 0,18 cm
Cutout diameter 4,8 cm
Net weight 0,098 kg
D.C. resistance Rdc 6,2 Ohm
Inductance of the voice coil L 0,08 mH

And here are the data of the F8SC "woofer":

Nominal power handling 20 Watt
Peak power handling 30 Watt
Nominal impedance 8 Ohm
Frequency response (-10 dB) 80 - 15000 Hz
Mean sound pressure level 82 dB (1W/1m)
Maximum cone displacement 5 mm
Resonance frequency fs 103 Hz
Magnetic induction 0,8 Tesla
Magnetic flux 150 ľWeber
Height of front pole-plate 3 mm
Voice coil diameter 2 cm
Height of winding 0,45 cm
Cutout diameter 7,6 cm
Net weight 0,25 kg
D.C. resistance Rdc 7,7 Ohm
Mechanical Q factor Qms 3,03
Electrical Q factor Qes 1,52
Total Q factor Qts 1,01
Equivalent volume Vas 1,4 l
Effective piston area Sd 30 cm2
Dynamically moved mass Mms 2,2 g
Force factor Bxl 2,69 T ˇ m
Inductance of the voice coil L 0,35 mH
Click to expand...
Hi Rene,
You are asking for someone to design your system for you.

Look up "crossovers" to get some design info.
The biggest concern is the speaker enclosure, get a box building program.
The box designer will ask for the specs of your speakers.

Good Luck,
Tom
 
"Tom Biasi" <tombiasi***@optonline.net> schreef in bericht
news:Fa2dneyVFeFEkgfVnZ2dnUVZ_hqdnZ2d@giganews.com...
You are asking for someone to design your system for you.
Click to expand...
Well, not exactly, I am asking if someone with knowledge about AC
calculations could and would calculate for me how to change the values of
the components in an _existing_ design so the impedance of the complete
circuit is increased by two ohms.

It is however true that I am asking someone to do work for me. Everybody who
posts a question to a ng does so, he or she is asking for a reply and
writing a reply is an effort as well. No one is obliged to do this, I am
merely asking politely and hoping someone will help. If not, bad luck for me
;-).

A very long time ago I learned a bit about these things, I found they were
very hard to understand back then and getting back into it (haven't used
them for many many years) takes a great deal of time and effort. Someone who
does this e.g. as a job could calculate this in a matter of minutes. I was
hoping that someone like that might read my post and would be willing to
help my out.

The biggest concern is the speaker enclosure, get a box building program.
The box designer will ask for the specs of your speakers.
Click to expand...
That would be important if I would want to change the frequency response of
the crossover, not to increase the overall impedance where this response
remains the same. The box has also already been designed by the way, I have
posted a link to the design.

Thanks anyway!

Yours sincerely,
Rene
 
"Rene" <invalid@arie.beukenoot> schreef in bericht
news:lZymk.227929$oo.129607@newsfe09.ams2...
"Tom Biasi" <tombiasi***@optonline.net> schreef in bericht
news:Fa2dneyVFeFEkgfVnZ2dnUVZ_hqdnZ2d@giganews.com...
You are asking for someone to design your system for you.

Well, not exactly, I am asking if someone with knowledge about AC
calculations could and would calculate for me how to change the values of
the components in an _existing_ design so the impedance of the complete
circuit is increased by two ohms.
Click to expand...
And I should add: "If that is possible at all...".

Sincerely,
Rene
 
"The Phantom" <phantom@aol.com> schreef in bericht
news:0lfm94l4j4cns9b5e2qh258coqss1smp50@4ax.com...

I think you might find more help at this forum:
http://www.diyaudio.com/
Click to expand...
That is a very good tip, it seems to be a very active forum. I have
immediately bookmarked it.

Yesterday I also sent a mail to the technical support team of Visaton and to
my amazement they seem support very seriously, contrary to what I usually
experience when contacting a company (people only interested in selling
stuff), this morning I found a reply. It seems not possible to alter the
impedance by just altering some components of this filter, it would require
redesigning the complete filter.

I will see what I am going to do, maybe I will build a couple of pcb's with
integrated amplifiers, they are not expensive nowadays and I already have a
big suitable transformer for the psu. The ones I have in mind will drive
speakers of 4 ohm and seem to be very good.

Thanks for Your reply!
Yours sincerely,
Rene
 
On Thu, 7 Aug 2008 11:09:42 +0200, "Rene" <invalid@arie.beukenoot> wrote:

"Tom Biasi" <tombiasi***@optonline.net> schreef in bericht
news:Fa2dneyVFeFEkgfVnZ2dnUVZ_hqdnZ2d@giganews.com...
You are asking for someone to design your system for you.

Well, not exactly, I am asking if someone with knowledge about AC
calculations could and would calculate for me how to change the values of
the components in an _existing_ design so the impedance of the complete
circuit is increased by two ohms.

It is however true that I am asking someone to do work for me. Everybody who
posts a question to a ng does so, he or she is asking for a reply and
writing a reply is an effort as well. No one is obliged to do this, I am
merely asking politely and hoping someone will help. If not, bad luck for me
;-).

A very long time ago I learned a bit about these things, I found they were
very hard to understand back then and getting back into it (haven't used
them for many many years) takes a great deal of time and effort. Someone who
does this e.g. as a job could calculate this in a matter of minutes. I was
hoping that someone like that might read my post and would be willing to
help my out.

The biggest concern is the speaker enclosure, get a box building program.
The box designer will ask for the specs of your speakers.

That would be important if I would want to change the frequency response of
the crossover, not to increase the overall impedance where this response
remains the same. The box has also already been designed by the way, I have
posted a link to the design.

Thanks anyway!

Yours sincerely,
Rene

I think you might find more help at this forum:
Click to expand...
http://www.diyaudio.com/
 
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