Nogreenmanhumming wrote:great to see someone else building these, keep us posted on how it goes!
my caps for the crossovers arrived today so Joe - a few more questions:
* should i leave a passive zobel on the tweeter or is that not now needed with the active setup?
Small fuse during testing can be a good idea and/or a 1000uF cap in series with the tweeter.* any thoughts on tweeter protection with active? I thought i'd test with the passive xover still in place the first time....
With 3 modules you have 12000uF per rail already which is heaps but if you have extra on there it does hurt anything and will help to keep the power rail impedance low.* what is the point of diminishing returns with adding extra power supply caps to the powerrails? I have an additional 4800uF on each rail plus whats on the 3 amp boards in each monoblock. Is there any point in adding more?
Usually toroids only make noise if run on higher mains voltage so the core saturates or have a shorted turn around them by the bolt in the middle joining back to the chassis which makes about 300mV at a few hundred amps.* any suggestions about reducing transformer vibration? I have encapsulated toroidal power transformers and I can still hear the damn things vibrating away softly at 50hz plus harmonics - is there anything I can do other than buy better ones?
okwell I've changed one channel to active
The passive woofer and box tuning may be out due to the series resistance of the passive crossover which is now missing. The bass will also be much tighter due to the direct damping from the amp to the woofer. Basically you can measure the resistance of the passive woofer xover and add that in series with the woofer usually 0.5 to 1ohm. Or the active bass boost can we made more but make sure you have the tweeter level correct first. Also the low mids will be different as you do not have the phase issues caused by the woofer / mid woofer arrangement. Really need a stereo pair of the active to get the 6dB low end summing and phase correct. Also it would be good to run rightmark RMAA over each speaker box (one passive and one active) with a small condenser about a meter out from the box to see how many dB the tweeter should come down etc.it works, it sounds good, but i'm not yet sure if it actually sounds better than the passive version.
certainly it is different. very hard to describe the difference, other than the tweeter level. there's actually maybe subjectively a little less deep bass. but the mids are significantly different in a way i can't describe.
The 2ohms gives me no real help as we do not know the exact impedance of the tweeter in it operating range. Try running the woofer from a left source and the tweeter from the right source and pull down the tweeter level in your DAW until it seems right or RMAA shows a balance and give me the dB down figure and I can rework the 3.3k and cap.the tweeter is too loud, i put a 2 ohm resistor in series with the tweeter to see, and that brings it about to where it should be. what increase in the 3.3k resistor would that translate into?
