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In the Forum: Horn-Loaded Speakers
In the Thread: Macondo’s lowest channel.
Post Subject: Line-level passive vs. active ULF filterPosted by Romy the Cat on: 5/6/2011
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My sub-bass amp is back but I am not sure if I am comfortable with it. The guy from QAudio did a wonderful job to fix my modified B-2 power amp and now I have my amp for ULF with passive line level filter in it. So, Now I have two identical, fully functional B-2 power amp, one with line-level passive filter and another is with active filter. Of close the passive line level filter is way more preferable option but there are some “issues”. When I removed the active crossover and went to line-level passive then I got better very lover bass but I am not sure if I got better Sound. The ULF from line-level passive is more dynamic and more articulate but in a way more I would say “electronic”. The bass from active crossover is more lush, has more second harmonics and more organically tight with Macondo, even thought the ULF itself is not as “impressive”. I am sure that I will be looking more into it but as not it is not clear to me what is going on.
Most likely the answer is that with line-level passive I use “crooked filter”. It has 3 sequential first orders but the circulation of them a bit different as they work all together. With my active crossover each filter acts individually properly and do perfect Bessel curve. It might be the constitutive effect of the tubes in the active crossover - they are 12AX7 use as cathode followers. The 12AX7 not the best tubes for the application – I might play with it but I truly would like to get rid of active crossover. The line-level passive for sure more load my preamp-s, this is what I keep the first resistor high and the input impedance over 25K. The active crossover has input impedance over 1mR, so the preamp does not even acknowledges it. Remind you that my preamp driver 7 channels per side and each channel has input filter – a VERY heavy and very complicated duty.
Anyhow, I need to revise what I do in order to make my line-level passive to work, or more properly to say to sound more to my liking. I am sure that in one way or other I will eventually come to it and will find a proper configuration but it requires apparently having some initial pain….
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