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Calcutlating adaption of loudspeaker filter circuit

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

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they sound great but need a subwoofer which is the next I will build (this one
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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:

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The old version can be seen on
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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 µWeber 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 µWeber 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 · m Inductance of the voice coil L 0,35 mH

Reply to
Rene
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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

Reply to
Tom Biasi

"Tom Biasi" schreef in bericht news:Fa2dneyVFeFEkgfVnZ2dnUVZ snipped-for-privacy@giganews.com...

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.

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

Reply to
Rene

"Rene" schreef in bericht news:lZymk.227929$ snipped-for-privacy@newsfe09.ams...

And I should add: "If that is possible at all...".

Sincerely, Rene

Reply to
Rene

I think you might find more help at this forum:

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Reply to
The Phantom

"The Phantom" schreef in bericht news: snipped-for-privacy@4ax.com...

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

Reply to
Rene

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