I've taken the plunge to remove all passive crossover and build an active one. The circuit is 24dB/octave Linkwitz-Riley based on the design at http://sound.westhost.com/project09.htm. For a $50 project it's a tempting gamble 😀
The system was previously based on 1st order passive crossover so the phase coherency was already good. However upon powering up the active system there is much much improvement in transparency of the sound. Everything sounded 'easier' the bass even reminded me of my open baffle setup, but much..much power 🙂
At the moment i'm using 2 channel LM3875 build and a spare dared gainclone with tube stage (to drive the tweeters). But tonight I'm going to add additional channels using similiar LM3875s 😎 ... we'll see how it sounds...
The system was previously based on 1st order passive crossover so the phase coherency was already good. However upon powering up the active system there is much much improvement in transparency of the sound. Everything sounded 'easier' the bass even reminded me of my open baffle setup, but much..much power 🙂
At the moment i'm using 2 channel LM3875 build and a spare dared gainclone with tube stage (to drive the tweeters). But tonight I'm going to add additional channels using similiar LM3875s 😎 ... we'll see how it sounds...
What speakers are you using? Be warned, changing from passive to active crossovers may require a change in the size of the box, particularly if it is a ported design! 
I wonder why I need to change the box size?
It's a pair of Jensen SPX-7. The original crossover was pretty crappy, simple 1rst order with no Fs compensations and sounded pretty harsh. Managed to upgrade the crossover to proper cutoff frequencies, but did not like the inefficiencies of notch filters...
It's a pair of Jensen SPX-7. The original crossover was pretty crappy, simple 1rst order with no Fs compensations and sounded pretty harsh. Managed to upgrade the crossover to proper cutoff frequencies, but did not like the inefficiencies of notch filters...
It's to do with removing the passive crossover and changing the alignment of the whole box+crossover. It may not make enough difference to hear but is always worth remembering if you want optimum performance!
In the case of a speaker I went active with, box volume changed from 27 litres to 32 litres before it sounded its best!
Ok... managed to cram 4 channels of 3875 amps into this little box. Believe me this thing SINGS 😀
However I'm pulling my hair as the new pair of amps have hums. It's also running noticeably hotter than the old pair 😕 They are the exact same design except changing the R from metal film to carbon ...
However I'm pulling my hair as the new pair of amps have hums. It's also running noticeably hotter than the old pair 😕 They are the exact same design except changing the R from metal film to carbon ...
It's 160VA and does not seem to strain even when playing loud ... not sure what the correct requirements for 4x 3875s though... anyone have any ideas ?
gainphile said:
Many people incorrectly assume you need a huge transformer to play "loud". While this is true to some extent, and a beefy power supply certainly won't hurt (except maybe your wallet), you really need to factor in the sensitivity of the speakers. Take the simple example of an LM3875 driving 85dB @ 1W/1m speakers or 94dB @ 1W/1m speakers. To achieve a loudness level of 103dB @ 1m with both sets of speakers the LM3875 will have to supply 64W to the 85dB speakers but only 8W to the 94dB speakers. Clearly, the lower sensitivity speakers will stress the power supply quite a bit more in order to play "loud".
- Status
- Not open for further replies.