Off-topic
Sometimes it is hard to be ensure absolutely everybody can tell when you are making a little joke on the web. But you'd think the connection to "applauding" previously used and the use of the comical wording "find something mean" would be a good tip-off.
Sorry if I should have been clearer.
B.
Sometimes it is hard to be ensure absolutely everybody can tell when you are making a little joke on the web. But you'd think the connection to "applauding" previously used and the use of the comical wording "find something mean" would be a good tip-off.
Sorry if I should have been clearer.
B.
Last edited:
OK, ace-bass is not MBF. MBF and bass-reflex don't go well together. Ace-bass has negative output impedance matching out the coil impedance (almost - if all, it oscillates)
Just to add to forr post, you can't have negative output impedance without the system operating as a reaction to the speaker impedance. It is logically necessary.
The speaker impedance has various components. But the component that varies and which we are interested in is back-EMF which reflects cone motion, whether normal, oscillation, resonates, noise, or other introduced errors compared to the signal.
Perhaps characteristic of engineer-think, the series resistor feedback seems to serve no useful purpose when things are working perfectly. But you have to think in terms of unruly gremlins inhabiting your driver and making it distort. Than MFB provides the correction by way of changing the output voltage (which looks like negative output impedance).
As TNT correctly says, correcting the cone (or voice coil) motion with MFB is not the same as correcting the sound output in a BR system since cone motion and speaker sound output do not track together in a BR. It screws it up the FR (although harmonic distortion is reduced).
B.
Last edited:
I believe that ACE has two fundamental advantages. the first is that it can make the woofer resonate in the box at 20hz; Second, you can do this without using purpose built speakers.
Every time ACE bass i brought up here on DIYAudio, the thread becomes about whether Karl-Erik Ståhl's ideas where worth a patent or whether is as good as MFB!
ACEBass is a solution where someone has done the work of providing a set of equations and an implementation which can be easily implemented, including easy correction of T/S parameters.
As I see it is has one major advantage over MFB: that the solution can be used together with either a passive radiator or a port, to get the output efficiency delivered by that.
Also the implementation is quite easy as the sensor is just a simple resistor.
MFB is not that easy e.g. wrt noise and the needed g force ... finding the right sensor.
Will it give better bass? ... I would guess so, also building on the fact that it needs to be a closed box implementation, with all the benefits that comes with that.
All designs and implementations are a set of compromises ..
My 2 cents
Looking forward to seeing someone building something 😉
ACEBass is a solution where someone has done the work of providing a set of equations and an implementation which can be easily implemented, including easy correction of T/S parameters.
As I see it is has one major advantage over MFB: that the solution can be used together with either a passive radiator or a port, to get the output efficiency delivered by that.
Also the implementation is quite easy as the sensor is just a simple resistor.
MFB is not that easy e.g. wrt noise and the needed g force ... finding the right sensor.
Will it give better bass? ... I would guess so, also building on the fact that it needs to be a closed box implementation, with all the benefits that comes with that.
All designs and implementations are a set of compromises ..
My 2 cents
Looking forward to seeing someone building something 😉
I ran MFB with a Wheatstone Bridge to sealed boxes and Klipschorn bass for about 45 years. Great stuff.
(VC MFB works with sealed boxes, true horns, and baffles)
B.
(VC MFB works with sealed boxes, true horns, and baffles)
B.
Ben, just curious what you used in the reference leg of the bridge? Resistor only, or some combination of resistance and rising impedance a la Werner circa 1957?
I would like to try this with a sealed sub project in the future, so looking for practical advice, others' experience, etc.
I would like to try this with a sealed sub project in the future, so looking for practical advice, others' experience, etc.
Just a pot to create balance. I thought figuring how to put a capacitor in one leg to address rising VC impedance was relevant only rather far outside the bass and outside the band where a builder would want to have to face the complicated phase from a speaker operating (no attempt at correction over say, 200 Hz).
Hint: use an amp with lower max power than the driver can handle when a bad day shows up. (Hate to say it, but tube amps inherently will limit bandwidth and power and be easier to work with even if MFB module is chips.)
Main issue for me is how to assess improvement although should be quite obvious to the ear. In 1970, I used Polaroid photos on oscilloscope traces of Dirac pulses - very obvious to the eye but hardly quantifiable. Also, Dirac pulse needs "infinite" bandwidth and some not clear why a woofer should make pulses well. But I have never figured out how to measure benefit.
No part of audio system is more needing feedback correction which is the same as saying no part harder to address with feedback due to wild phase relations.
B.
Hint: use an amp with lower max power than the driver can handle when a bad day shows up. (Hate to say it, but tube amps inherently will limit bandwidth and power and be easier to work with even if MFB module is chips.)
Main issue for me is how to assess improvement although should be quite obvious to the ear. In 1970, I used Polaroid photos on oscilloscope traces of Dirac pulses - very obvious to the eye but hardly quantifiable. Also, Dirac pulse needs "infinite" bandwidth and some not clear why a woofer should make pulses well. But I have never figured out how to measure benefit.
No part of audio system is more needing feedback correction which is the same as saying no part harder to address with feedback due to wild phase relations.
B.
Last edited:
It should reduce distortion. That would be quite straightforward to measure. Also, the feedback changes the frequency response. Also easy to measure these days. Not so much "back then".
That's just easy "shooting fish in a barrel". It's the "fast" bass that would be nice to measure.
B.
B.
Although my testing was done before the age of REW and this is just guesses, the interesting test point is the signal to the speaker. With MFB working, it should look more distorted, both for harmonic distortion and esp for pulses where all kinds of exaggerated bumps to jump-start the start of the pulse and then to hold back the end of the pulse.
My experience is that "fast" bass usually means "lacking in LF extension".
"Slow" bass is the opposite - too much VLF, usually because the designer has aimed for a flat anechoic response, and then put the speaker in a room.
Chris