GM said:
Having seen GM post that somewhere before led to the deliberate choice of a high aspect ratio port in the miniOnkens and can be clearly seen in the impedance plot where the lower of the 2 BR impedance bumps is heading towards dissappearing (blue) ... and stuffing the port reduces it even further (red). Add enuff and it would go away completely.
dave
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Dave,
how about a subsonic filter for the FR125s in vented Cabinets. As far as I undertstand it, for all vented designs (including aperiodic), there is no more mechanical damping below the tuning fr, which means uncontrolled cone movement.
Don't you think, with the enormous xmax of the driver and the uncontrolled cone movement in subsonic frs, intermodulation-distortions (is that the correct translation?) through doppler-effect might be an issue to be adressed -- with the benefit of better, clearer hights?
And if so, would the Line level filters from your tt-linespeakers site be a possible solution?
best, martin
ps. sorry for bad english, this tech stuff is far beyond my normal use of this beautifull language.
how about a subsonic filter for the FR125s in vented Cabinets. As far as I undertstand it, for all vented designs (including aperiodic), there is no more mechanical damping below the tuning fr, which means uncontrolled cone movement.
Don't you think, with the enormous xmax of the driver and the uncontrolled cone movement in subsonic frs, intermodulation-distortions (is that the correct translation?) through doppler-effect might be an issue to be adressed -- with the benefit of better, clearer hights?
And if so, would the Line level filters from your tt-linespeakers site be a possible solution?
best, martin
ps. sorry for bad english, this tech stuff is far beyond my normal use of this beautifull language.
Greets!
As I noted on one of the other FR125S threads, you'll need to design a 6th order alignment, which requires a specific cab alignment and active subsonic 'rumble' filter: http://www.highefficiencyloudspeakers.com/SchematicDiagrams.html
This was a 'knee-jerk' response (the politically correct definition being speaking before fully engaging brain) on my part though. Frankly, if a low Fc BLH or similar isn't used, then I recommend either a bipole or max flat impedance (MFA) alignment/separate woofer system if max performance is desired from this driver. In a corner, just the MFA may suffice depending on your listening preferences. For smaller rooms or nearfield, then the aperiodic is probably best.
GM
As I noted on one of the other FR125S threads, you'll need to design a 6th order alignment, which requires a specific cab alignment and active subsonic 'rumble' filter: http://www.highefficiencyloudspeakers.com/SchematicDiagrams.html
This was a 'knee-jerk' response (the politically correct definition being speaking before fully engaging brain) on my part though. Frankly, if a low Fc BLH or similar isn't used, then I recommend either a bipole or max flat impedance (MFA) alignment/separate woofer system if max performance is desired from this driver. In a corner, just the MFA may suffice depending on your listening preferences. For smaller rooms or nearfield, then the aperiodic is probably best.
GM
Greets, part deux!
Hmm, apparently I'm still in 'knee-jerk' mode...........
Yes, the 2nd order PLLXO will work fine as a subsonic filter to limit amplitude modulation distortion (AMD) due to any driver non-linearities. Still, based on the comments of others (mine are still in open cell foam 'boxes', so max aperiodic), intermodulation distortion (IMD) (aka frequency modulation distortion (FMD)) due to the Doppler effect (harmonic modulation) is apparently a real problem in ~max flat MLTLs even when BW limited below Fb due to its high Xmax, hence the theoretical need for a 6th order alignment and my previous recommendations to alleviate its shortcomings.
As always though, YMMV.
GM
lovechild said:
Hmm, apparently I'm still in 'knee-jerk' mode...........
Yes, the 2nd order PLLXO will work fine as a subsonic filter to limit amplitude modulation distortion (AMD) due to any driver non-linearities. Still, based on the comments of others (mine are still in open cell foam 'boxes', so max aperiodic), intermodulation distortion (IMD) (aka frequency modulation distortion (FMD)) due to the Doppler effect (harmonic modulation) is apparently a real problem in ~max flat MLTLs even when BW limited below Fb due to its high Xmax, hence the theoretical need for a 6th order alignment and my previous recommendations to alleviate its shortcomings.
As always though, YMMV.
GM
lovechild said:
An aperiodic design does have some mechanical damping... between a BR & sealed.
One of the suggested alignments that someone suggested was 3rd order sealed... passive this means a huge bipolar elco cap in series with the driver -- something i find distasteful, but tis would be easily implemented with a PLLXO -- best of course would be shrinking the size of a coupling cap in the amp to act as the filter. The same could be done with apeeriodic or BR.
As i've always said -- the biggest improvement when you add an active woofer is the improvement in the midrange from releaving the mid-tweeter from those LF excursions.
dave
GM said:Greets, part deux!
Hmm, apparently I'm still in 'knee-jerk' mode...........
Yes, the 2nd order PLLXO will work fine as a subsonic filter to limit amplitude modulation distortion (AMD) due to any driver non-linearities. Still, based on the comments of others (mine are still in open cell foam 'boxes', so max aperiodic), intermodulation distortion (IMD) (aka frequency modulation distortion (FMD)) due to the Doppler effect (harmonic modulation) is apparently a real problem in ~max flat MLTLs even when BW limited below Fb due to its high Xmax, hence the theoretical need for a 6th order alignment and my previous recommendations to alleviate its shortcomings.
As always though, YMMV.
GM
Hi
Greg, I got some questions on that.
1) The max flat impedance (MFA) alignment; does that mean a RLC zobel network to flatten the impedance peak at fb? If so,I think the MFA is not needed when the acting on low level, between preamp and poweramp (or is that called line level), right?
2) When I add 2nd order PLLXO as subsonic filter on low level, doesn't that transform my 4th order BR alignment to a 6th order BR alignment?
But also some awnsers (maybe)?
I have the FR125S in 12 liter BR with a slighlty damped port, tuned to ~45Hz. From my test CD I can hear, that there is clearly audible bass down to ~45Hz. So I would think I can set the PLLXO 2nd order highpass to 40Hz.
I ran some simulation, first with active subsonic filter 2nd order at 40Hz and second with passiv filter on speaker level,with the needed zobel network (and distasteful caps) to double check.
My impression is for both activ and passiv, the subsonic filter at ~40Hz flattens the bass peak before drop off (simular to the damped port), but with a significantly reduced cone excursion below 60Hz, compared to the damped port.
So IF my conclusions and my sims are correct, the PLLXO could be the way to address amplitude modulation distortion and the intermodulation distortion, without an active network or distastefull caps on the high level (speaker level).
best, LC
Greets!
1) No, it's a prosound box alignment. Wayne Parham promotes it as a Pi Align, so you can calc one using either his DOS program or make a spreadsheet from the math in his whitepaper.
2) This is one form of 6th order alignment and sounds like you've proven its effectiveness. I was thinking more in terms of the one I listed or a specific cab alignment based on Keele's 6th order concept which requires a Q = 2 bass boost ckt. to ~preserve whatever the chosen 'ideal' alignment is.
GM
1) No, it's a prosound box alignment. Wayne Parham promotes it as a Pi Align, so you can calc one using either his DOS program or make a spreadsheet from the math in his whitepaper.
2) This is one form of 6th order alignment and sounds like you've proven its effectiveness. I was thinking more in terms of the one I listed or a specific cab alignment based on Keele's 6th order concept which requires a Q = 2 bass boost ckt. to ~preserve whatever the chosen 'ideal' alignment is.
GM
You could use another woofer with it and it'd work well, but it rather defeats the purpose of using driver over a wide range.
Since I started the thread, I figured I owe it to the community to show how my speakers turned out. I completely forgot to post it here.
See below!
http://www.audiocircle.com/circles/viewtopic.php?t=28047
Since I started the thread, I figured I owe it to the community to show how my speakers turned out. I completely forgot to post it here.
See below!
http://www.audiocircle.com/circles/viewtopic.php?t=28047
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