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In Reply to: RE: "just filter out the bass feeding the amp" posted by Tre' on July 07, 2015 at 18:47:39
I did try to find what I'm about to relate, but couldn't. I know it's somewhere in the Electro Voice white papers or PA Bible.
I remember EV writing that one of the benefits of bi-amping is that when you are talking about a full range audio signal the mids somehow ride on top of the bass signal. This results in the midrange signal being modulated by the bass signal. This modulated signal is a distorted signal. Therefore, if you can remove the bass signal before it gets amplified by the power amplifier, then the distortion is not amplified. That's how I remember it anyway.
I think connecting the amplifier directly to the driver solves many damping issues, and damping is only really important with the bass, and it can be tailored by the amp designer. Lack of power can addressed by higher efficiency.
One day I would like to have one SET amp optimized for bass, and one optimized for mids/treble. It's possible that eliminating the sub bass is the key. I get your point about the Voltsecond article.
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Big speakers and little amps blew my mind!
Follow Ups:
Thanks for you input.
Paul made some good points as well but the point that I'm not sure everyone is getting is this,
All other frequencies are riding along with the lowest frequency at that moment.
If the load line has turned to an ellipse (or worse, a beach ball) because of a lack of inductance then all the frequencies are traversing that bad load line.
Removing just a little of the low bass (and using a more suitable amp and speaker for that low bass) can make a big improvement in the load line for the rest of the music.
My JBL 2118 midrange speakers only play down to 200Hz so that's where I cut the bass to the SET and use a SS amp into a pair of 15" JBL 2231's for the bass.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
If the load line has turned to an ellipse (or worse, a beach ball) because of a lack of inductance then all the frequencies are traversing that bad load line.
I'm not convinced this is as bad as everyone says it is. A while back I looked (in spice) at some small signal 1Khz and 10Khz sine waves added to a large signal 20hz sine. I then used a steep filter to cut out everything below the 1Khz (or 10Khz) and looked at the distortion as I varied the amplitude of the 20Hz signal. Sure I saw a difference with the larger amplitude 20Hz causing slightly more distortion at higher frequencies but unless I was current clipping, I didn't find the results ground breaking enough to interest me.
dave
> "but unless I was current clipping, I didn't find the results ground breaking enough to interest me."
Was there anything remarkable when it did clip? It's hard not to clip with a 2A3 amp.
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Big speakers and little amps blew my mind!
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