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Discussion Starter #41
Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

.....and since you're now attenuating a range, everything else will need to fit in with this range to keep tonal balance. Each null that one addresses means you're cutting across ranges.

On the power of eq......One doesn't need to 'treat' every null. Deep and narrow nulls are less of an issue. Shallower nulls spread over a 1/3 of an octave or more are a bigger issue specially in the mid range. More than the units ability to flatten out the response, I would value the L/R balance across 2000 odd points. A eq at 1/6 octave with nice slider controls for each channel/side (assuming you stack these units), would be the cherry on the cake. Of course 1/3 to 1/6 would be a two year learning curve:)
All correct. High Q (narrow) dips/peaks are less audible than low Q (wide). Overall response (summed) isn't THAT important to get 100% either, this is responsible (no pun intended) for overall tonal balance. The L/R response however is far more important as it largely dictates how the system stages, here we have far more use for an accurate 'multipoint' FIR EQ. Any dip or peak that isn't consistent from left to right channel will cause the stage to either side. Same with absolute phase, which is inaudible. Relative phase is not however. Having phase correction (phase EQ) is invaluable in the ITD-range (below 1600Hz or so) because it can keep the center/staging calm even if the relative group delay (magnitude/phase relation) is off.

Since APL does all the corrections automatically the amount of EQ you want/need to adjust yourself is not that big actually. I found 2 or 3 areas in the initial run of APL that I manually applied some minor correction to. By all means, this is far less than I usually correcting for when fine tuning after measuring using the 'traditional method'.

Again, you already know this. You just so anal about doing everything manually xD
 

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Discussion Starter #42
Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

Sorry for the error in my previos post: delay of 16 cm, but not 16 msec, of course between left and right channels.
I haven't tested it yet but it seems from your screenshot that it can be adjusted 0-5ms. If so, 5ms ~ 170cm. Correct me if I'm wrong...
 

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Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

The more I read about the details, the more I realize that I don't quite understand. I am going to download the plugin and see what I can do with it.

I have a laptop with foobar, a Dayton Audio iMM-6 Calibrated microphone, a head unit that has a line level input and the soon to be downloaded plugin. It there anything else I need?
 

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Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

Hanatsu,
Both yes and no. If 1 ms at normal atmospheric pressure corresponds to appr. 34 cm (little bit more, indeed), so you are right. You can backup fir-flter with the max delay of 4,797 ms.
It will be a new filter: ***-fir_4,797ms. Then you can use this new file to delay it further. New file name will be: ***fir_4,797ms_4,797ms. I mean that the last one has a delay of 4,797 x 2, which is about 350 cm. I can not see any restrictions for this process. Going to ask Raimonds about this issue.

I'm now trying to tune my front again as some things have been changed (HPF, LPF, crossover frequencies and the most important - frequency response of the both fronts). If I would still use old APL-corrections made onr year ago, the sound will be more bright than necessary. I will for sure make some tests of the delayed files with TDA software.

Regarding time alignment, phase control etc. - to my opinion the majority of people underestimate its importance as they think it is not audibe. I could easily hear the stage center moving by just applying different delays between left and right speakers. It is kind of rotating image, which has its own optimal position. Do not forget about midbass and sub. For some complicated subs it is required quite siginificant optimization ion the time domain (much more than 5 ms). Try to spend your time analysing results of tests with TDA - sure you will be surprised. By the way, the latest version of this soft: TDA 9.0 gives you even more information - distortion analysis.

When you open graffs in TDA, it is possible to use a cursor for determination of exact values needed to be corrected. APL's accuracy is rather high (compared to fx. min. delay steps in my HU - 0,1mc (3,4 cm)).
 

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Discussion Starter #45
Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

Hanatsu,
Both yes and no. If 1 ms at normal atmospheric pressure corresponds to appr. 34 cm (little bit more, indeed), so you are right. You can backup fir-flter with the max delay of 4,797 ms.
It will be a new filter: ***-fir_4,797ms. Then you can use this new file to delay it further. New file name will be: ***fir_4,797ms_4,797ms. I mean that the last one has a delay of 4,797 x 2, which is about 350 cm. I can not see any restrictions for this process. Going to ask Raimonds about this issue.

I'm now trying to tune my front again as some things have been changed (HPF, LPF, crossover frequencies and the most important - frequency response of the both fronts). If I would still use old APL-corrections made onr year ago, the sound will be more bright than necessary. I will for sure make some tests of the delayed files with TDA software.

Regarding time alignment, phase control etc. - to my opinion the majority of people underestimate its importance as they think it is not audibe. I could easily hear the stage center moving by just applying different delays between left and right speakers. It is kind of rotating image, which has its own optimal position. Do not forget about midbass and sub. For some complicated subs it is required quite siginificant optimization ion the time domain (much more than 5 ms). Try to spend your time analysing results of tests with TDA - sure you will be surprised. By the way, the latest version of this soft: TDA 9.0 gives you even more information - distortion analysis.

When you open graffs in TDA, it is possible to use a cursor for determination of exact values needed to be corrected. APL's accuracy is rather high (compared to fx. min. delay steps in my HU - 0,1mc (3,4 cm)).
I agree...

If correcting for group delay in the subwoofer frequencies, we either require channel independent delay (not possible with 2ch), which means more than 1 board of APL.

OR

Can it do frequency dependent delay to correct a specific frequency range? If so, how's that done manually? In TDA? I'm hopefully trying out TDA this week ;)
 

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Discussion Starter #46
Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

The more I read about the details, the more I realize that I don't quite understand. I am going to download the plugin and see what I can do with it.

I have a laptop with foobar, a Dayton Audio iMM-6 Calibrated microphone, a head unit that has a line level input and the soon to be downloaded plugin. It there anything else I need?
Except the APL software... that's it.
 

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Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

I agree...

If correcting for group delay in the subwoofer frequencies, we either require channel independent delay (not possible with 2ch), which means more than 1 board of APL.

OR

Can it do frequency dependent delay to correct a specific frequency range? If so, how's that done manually? In TDA? I'm hopefully trying out TDA this week ;)
The APL Workshop measurement is showing only "real" dips (not caused by interference) and we must deal with them by ordinary means but not with a direct equalizer use at first.
We should try to find real problem causing that dip and remove it by basic tuning.
Usually such dips are caused by improper crossover tuning (including out of phase). And they are non minimum phase. The correction of non minimum phase problem (do not have ringing in its impulse response) with minimum phase equalizer (will have ringing in its impulse response) is not the best to do.
Only in the case when we can not do anything with a basic tuning we should use an eq.
And we may need to reduce a deep of that dip by 2 times (manually) to get best audible result. That was tested on problematic studio monitors where crossover bands did not overlap as needed - simply did not reach each other making huge dip at 1 kHz.


“Can it do frequency dependent delay to correct a specific frequency range?”

Yes, but it is based on TDA measurement and must be aplayed “manually” (no ready to use tool) after all work on “amplitude” is done.
Returning to Quested monitor example - delay estimation and measurement
 

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Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

Raimonds,
Does it mean that if there is a dip of -10dB, correction for avoiding it will be -20 dB for the best results?
 

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Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

An issue about use of two soundcards ( one for playback, another for recording) become actual.
Two different clocks are working in such case. And we will have time compression or expansion in our measurement data that depends of which clock is faster. Therefore the actual set of soundcards must be tested for that issue. APL Workshop Impulse Response tab is drawing all IRs in one graph. All of IRs must be on 5 ms with they max spike.



In case of time compression or expansion we will see IRs covering some time interval. It is ok if this interval goes under window (green curve).



If no, we have a problem.




The workaround for this is to accent first or last measurement (put the microphone more closely to the speaker/tweeter) that depends which clock is faster and you must find it by an experiment.
 

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Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

I agree...

If correcting for group delay in the subwoofer frequencies, we either require channel independent delay (not possible with 2ch), which means more than 1 board of APL.

OR

Can it do frequency dependent delay to correct a specific frequency range? If so, how's that done manually? In TDA? I'm hopefully trying out TDA this week ;)

I do not think TDA is able to make frequency dependent delay manualy, But is this necessary for junction of two sources (midbass and sub, for example)? Of course it will be nice to have ...
My sub is not connected to APL1 - only two front channels (2way-passive with its own crossover). I delay front left channel (quite a lot) in order to fit to the response from the sub (more than 25 ms). The same - with the pair: front right channel + sub. And it works fine, as sceene is placed just where it shoud be. No other time alignment adjustments are needed.
 

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Discussion Starter #53
I'm curious as to how it removed your 70 Hz "dip". Did it just decrease the output above and below that dip to flatten the response?
Yes as I said, there was in fact large modal peaks above and below the "dip" ;)

Sent from my Samsung Galaxy S5 using Tapatalk
 

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Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

Great news! Thanks. Even the first model of APL1 was not rather thick after my mind, but to get it smaller makes this unit more portable with the increased flexibility for installation.
 

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Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

I have a convertible which is a bit challenging because the response changes drastically with the top up and down. Luckily, I drive the car with the top down 80-90% of the time.

For that 10-20% that I have my top up, is it possible to do two separate calibrations and switch on the fly?
 

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Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

.

The rotary 16 position preset switch for APL1 can be installed anywhere in a car by use of an unshielded 5 wires cable of any length (flat cable, cable for security systems).


Anyway, please feel free to ask me more questions!

BR,

Raimonds
Acoustic Power Lab :: Home
Is this 16 position switch included? if it's not included do you have a link. i'd like to see what this looks like. Thanks
 

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Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

Yes, it is possible to do two separate calibrations (and not only two) and then switch on the fly. The switching takes about 1 second. The switching process is clear – without pops, noise or muting.
The switch is this:
BCKS1001 - LORLIN - SWITCH, ROTARY, HEX, NO STOP, IP65 | Farnell element14
The switch and flat cable of length you need are included in “16 preset” option.
 

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Discussion Starter #60
Re: Comprehensive Review: " APL1 " - Advanced DSP / EQ / Phase Correction Unit

Yes, it is possible to do two separate calibrations (and not only two) and then switch on the fly. The switching takes about 1 second. The switching process is clear – without pops, noise or muting.
The switch is this:
BCKS1001 - LORLIN - SWITCH, ROTARY, HEX, NO STOP, IP65 | Farnell element14
The switch and flat cable of length you need are included in “16 preset” option.
Where do you connect the cable btw?

There's a 5-pin connector on the board somewhere? Interested in making a switch myself.
 
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