Hi Raimonds, good to see you here. Nice project!
I really like the idea of apply driver ports to flat baffled speakers for an acoustic low-pass. Like what Danley does with synergies, but why can't it work for flat baffles too, huh?
On a quick personal note, I finally got a PC with enough graphics capability to run APL_TDA Real-Time. I'll try to get use it side by side with my normal tuning measurement software next time I tune a new unity/syn project.
I built a quick processor schematic in q-sys shown at bottom, for the above xovers frequencies and orders, using your Option2 (ala Linkwitz style)
Here's the measured summed mag and phase, and then impulse and step.
I did not do the all-pass addition Linkwitz recommends, hence the degree of ripple.
I'm curious how you plan to implement steep IIR xovers, as we know how much they are going to muck up phase, impulse and step.
Are you eventually planning on some phase linearization of the IIR's, or maybe just using linear phase xovers???
here's the processor..
Thank you @mark100 for so nice post and questions!
And the example of post 40 - how it looks like in the C5
The approach "All filters for all ways" is in use and results are such:
Summed magnitude:
Summed Phase:
Summed Group Delay
Summed Impulse Response:
Individual IRs of all way one by one will follow.
It would be nice to know your experience with TDA RT!
And the example of post 40 - how it looks like in the C5
The approach "All filters for all ways" is in use and results are such:
Summed magnitude:
Summed Phase:
Summed Group Delay
Summed Impulse Response:
Individual IRs of all way one by one will follow.
Individual IRs of all ways one by one:
If we have summed IR of crossover, we can use it as all pass filter to lineariz the overall phase of the crossover by sacrificing a minimal latency possible.
That should be found by a trial. Let`s take some latency number that is about 1.5 times bigger max value of GD curve,
cut such part of inverted summed IR and check its magnitude`s response
Here is inverted IR with latensy "cut" of 12 ms in use.
and slightly zoomed
It has magnitude error because of cut of 12 ms
If we are happy with a particular error`s value, we have result. If not, increase or decrease the latency value to meet requirements
And all IRs after all pass filter from summary IR has been used:
As you see, they all are symmetrical which means a linear phase behavior.
And IR curves above is describing that.
It is done. The TDA curve in the post #8 is showing that.
If we have summed IR of crossover, we can use it as all pass filter to lineariz the overall phase of the crossover by sacrificing a minimal latency possible.
That should be found by a trial. Let`s take some latency number that is about 1.5 times bigger max value of GD curve,
cut such part of inverted summed IR and check its magnitude`s response
Here is inverted IR with latensy "cut" of 12 ms in use.
and slightly zoomed
It has magnitude error because of cut of 12 ms
If we are happy with a particular error`s value, we have result. If not, increase or decrease the latency value to meet requirements
And all IRs after all pass filter from summary IR has been used:
As you see, they all are symmetrical which means a linear phase behavior.
Yes, 8th order should be steep. But the beauty is to implement them not by use of IIR math but by creating virtual IIRs in FIR machine - by combining any number of IIRs necessary.
And IR curves above is describing that.
I still do not get what advantage that would bring over conventional HP filtering, other than having yet another radiating element in the baffle. Would anyone be so kind as to explain that?
That does not make sense to me: conventional LP filtering does the same thing as the total transfer function is supposed to remain the same. Furthermore, excursion above say 150Hz is so low the filtering has hardly any impact on excursion induced distortion.
It doen't for distorsion induced by loudspeaker drivers.
That is the reason some people say bandpass speaker drivers are more likely to be overdriven - you don't hear the alarming distorsion (at least not so much).
"People" say all sorts of things about audio. I am not yet convinced so far. Measurements or it did not happen.
Basically, the high frequency / high order distortion products will be acoustically filtered out.
Looks like a solution looking for a problem.
But now at least the line of thinking has become clear, but still I would like to see whether the claim that mechanical filtering offers improvement over electric filtering can be substantiated, especially since the pipes or slots may have their own issues.
But now at least the line of thinking has become clear, but still I would like to see whether the claim that mechanical filtering offers improvement over electric filtering can be substantiated, especially since the pipes or slots may have their own issues.
It does not offer improvements beside the fact that filtering prior to the main distorting element (the driver) has no/less effect compared to filtering after the distorting driver.
while ports do have their flaws they behave incredibly well if done right, also considering their huge virtual "xmax". This I found out doing my helmholtz port investigations.
Yes, the individual impulses say it all, very nice.
And sorry i didn't catch the TDA summation in post #8 showing already done.
Your DIY ability, especially with DSP and processing is truly amazing Raimonds !!
The idea as I understand it, is the level of harmonic distortion being generated by fundamental frequencies of the driver below the electrical lowpass, are reduced by the additional acoustic low-pass provided by the trapped air enclosure that using ports gives.
A transfer function shows frequency magnitude response and phase, but doesn't show harmonic distortion.
I think you could get near identical transfer functions from open cone and enclosed/ported cone.
I guess the best way to test the acoustic low pass harmonic distortion reduction would be to mount a driver in a box, and compare distortion with plates & ports put over the cone. See if the open cone has more harmonic distortion that the ported cone.
Danley has posted a bit on the acoustic low pass...you may want to search him for it..
Attention: recording engineers, producers, directors, studio owners, everyone involved in the live sound recording job
Dear friends,
I am in process of collecting initial ideas, opinions on some very fresh solution for the recording industry.
I would like to ask you to participate in a short interview that can be followed by some "test drive".
Please send me PM to apl {at} aplaudio {dot} com if you agree to participate!
Thank you,
Raimonds
Dear friends,
I am in process of collecting initial ideas, opinions on some very fresh solution for the recording industry.
I would like to ask you to participate in a short interview that can be followed by some "test drive".
Please send me PM to apl {at} aplaudio {dot} com if you agree to participate!
Thank you,
Raimonds