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My 1st enclosure sounded very well (only under 200Hz), but as I explained, it was too big (you said that too and I agree). So how big should it be? Should I use the 1st design (rectangular top and bottom) at a smaller scale (how small?) or the 2nd design (square top and bottom) at a larger scale (how large?)? What should the volume of the enclosore be (approximately)? But it sounds great! Will it work if I use three Linkwitz-Riley bandpass (highpass+lowpass) filters in series (highpass+lowpass+highpass+lowpass+highpass+lowpass)?

Hi Audioguru, My enclosures are not glued, I used 4cm long skrews (about 50 of them for each enclosure)

I didn't want to turn the volume up more. No... I found the size of the enclosure in a book (1980s). Yup. 3m/4m/2.4m. Ok...

Hello Audioguru, I didn't say that my 8" subwoofers reached their mechanical limit and 20W was probably the average power delivered to the speakers and they ain't cheap either. I ment that I wouldn't turn the volume up more, everything in the room was shaking, I probably scared my neighbours too :D. The enclosure could support 12" subwoofer at full power ;D. For the subwoofer and the midrange I think I'm going to use something like the 10W amp in the link below but without the bass boost (for each speaker - that means four amps). http://www.redcircuits.com/Page61.htm

I don't think we're talking about the same kind of watts :-\. If you look at same types of speakers you'll se that the power stamped on each speaker is different from one manufacturer to another. For example 10" car subwoofers can be found with a power rating of 180W to 1000W :o, even if the 1000W subwoofer is less powerful than the 180W subwoofer, but their real power is probably around 40W :P. A lot of car audio systems (that include a radio and a CD player) have their power amp built with TDA 1554 IC that has a maximum output power of 4x11W single ended or 2x22W bridged, but all manufacturers write 4x45W or 4x60W on them. My 8" 8ohm subwoofers are stamped "80W RMS continous power" and "120W RMS peak power". When I tested them in properly designed enclosures with a 2x35W/4ohms or 20W/8ohms power amp they almost reached their mechanical limit below the amp's maximum power :(. My amps will have overcurrent protection ;D, so they won't allow any dangerous DC to the speakers. It seems funny but I know the Linkwitz-Riley filters from an old magazine ;D (20 years old...), it wasn't written anywhere that those filters were Linkwitz-Riley filters. Thanks anyway.

Not yet. My 3 way speaker system project is two years old now and since then it's been permanently changing, so I'm not sure what kind of filters I'm going to use for the crossover. This project is still on the "drawing board". My biggest problem is how much power should each speaker get. I'd choose 10W (RMS) for the subwoofer, 10W (RMS) for the midrange and 5W (RMS) for the tweeter and that's because I want my system to be able to withstand music played with instruments, not made by electronic means. The 10W subwoofer amp will have a peak power of 20W, so it'll be perfect for my 8 inch kevlar cone subwoofers (it says that their maximum power is 120W but I don't believe it :P). ... ::) Can you show me some schematics of those Butterworth or Linkwitz-Riley bandpass filters?

OK... :-\ So separating the frequencies for the three amps won't be a big problem. If I choose a 10W amp (per channel) for the subwoofer (20Hz-200Hz) then how powerful should the midrange speaker (200Hz-4kHz) amp and the tweeter (4kHz-20kHz) amp be?

The filters are (theoretically ::) - I haven't built them yet) six 6dB/octave high pass and six 6dB/octave low pass in series, each using a resistor and a capacitor. One high pass filter and one low pass filter in series form a band pass filter. Six 6dB/octave band pass filters in series should form a 36dB/octave band pass filter :-\. I simulated 6, 12, 18, 24 and 36dB/octave band pass filters using a computer program and the last one was the best, it sounded better than the others ;D. If I wanted to make the building of this sound system easier I would have chosen a single amp per channel and separate the frequencies with passive filters (inductors and capacitors) but I don't think it would sound better than "one amp per speaker".

The input data (what I know ;D): -Subwoofer: 20Hz-200Hz -Midrange: 200Hz-4000Hz -Tweeter:4000Hz-20000Hz The output data (what I'd like to know ???): -Subwoofer amp power -Midrange amp power -Tweeter amp power I'm using 36 dB/octave active band-pass filters to separate the frequency domains for each speaker.

OK... But I'm still going to use my NiCd batteries... :P You suggested two circuits in your first reply. How can I modify them to to get a lower/higher voltage at the output?

I have a lot of new NiCd batteries and I plan to use them. NiMH batteries are smaller ;D, but they require a more complicated charger :P than the NiCd batteries.

But if the circuit is used only six hours a day then the batteries will have to be recharged only after a week ;D. The step up circuit should be simple and compact, so the lamp will easily fit in a pocket.

I'll use 2 to 4 LEDs, each consuming about 2mA@3V. Any type of convertor will do (except the ones that include ICs) as long as it won't use more power than the LEDs :-\.

I tested the

Cheap dual op amp IC with a maximum output current of 100mA that works below 2.4V or +-1.2V? ??? I want to build a portable preamp (also to be used as a headphone amp) that is very small and simple. The batteries are GP AA NiCd 800mAh.