Software Crossover/Equalizer

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#61
Deodato said:
Hello Bohdan,

The general consensus (brought about by litstening tests..) is still that phase distortion is not audible under normal circumstances. Really, "mimic the firing rate of the neurons in the cochlea"?? Please let blind tests be the judge over this. I will not link to papers by my own hand as evidence. The same inaudibility probably applies to pre echos, under normal circumstances. So if pre ringing is a dead horse, so is ZP, for all audible intents and purposes. But I do find pre echo as a phenomenon repulsive because it is unnatural.
All filters in nature have their phase signature, it is an intrinsic property of filters, electic or mechanic or otherwise. If the frequency response of one filter, or loudspeaker, is compensated by another filter, then the phase response is also compensated.
A perfect compensation cannot be claimed for the ZP filters in a crossover, as the drivers usually have different radiation patterns.

And then there also is the issue of FIR and frequency resolution under 100Hz or thereabouts. Precision, (and no component tolerances etc.) is one of the merits of DSP, but in the case of FIR this precision is a tradeoff with latency; it will take more than 10000 taps to have reasonable precision at 30 Hz. Do the math for your latency and precision. And of course there is the computational overhead for all these taps, so forget about a lean "What You Play Is What You Hear" system with a DSP on a multimedia computer, it will more likely become an audio server kind of solution. Add the price of yer dongle and one might want to look at something like miniDSP gear which I think is kinda cool. But we are talking PC based here of course. And Arcgotic, maybe later I will add FIR as an experiment, if only to assess the claims myself, but not anytime soon I think.
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Hi Deodato,

I have put together a very short paper about Stamford Uni experiment. http://www.bodziosoftware.com.au/Pre_Ringing.pdf so we can be on the same page.


Regarding the “consensus”, let me quote two well known audio workers and publishars:

1. Michael Gerzon

“ The subjective effect of phase compensation of the bass from loudspeakers is very marked, giving a much tighter and more 'punchy' quality, with greater transparency, and interestingly a subjective extension of bass response of at least half an octave. The improvement is audible even on loudspeakers with a very high cut-off frequency, such as Quad electrostatic designs. . . . The benefits of bass phase equalisation are considered, by those who have heard it, to be a substantial improvement over what was hitherto possible with analog technology, and digital equalisation provides a way of improving bass performance without going to ridiculously large giant space-consuming power-hungry monster speakers, and is certainly a much cheaper route “.

2. Keith Howard describing listening test with linear phase subs.

“As I pressed Play, I didn't know what to expect: a mild improvement or a revelation. To use a curry-house analogy, I was half-prepared for korma rather than phal. But when I compared the unprocessed and phase-corrected tracks, it took only a few seconds of the latter to persuade me that here was a significant improvement. Just as Michael Gerzon described, the phase-corrected sound was both weightier and punchier, and distinctly more coherent. It simply sounded more like a bass guitar, to the extent that I almost hummed along—not something that I would normally expect to do when listening to a bass-guitar accompaniment shorn of all else (sorry, John), and certainly not an urge I felt with the unprocessed track.
Still, time-consuming as it was, this experiment involved only a single music excerpt and was conducted in mono, and so hardly offers a comprehensive insight into the full benefit of bass phase correction. But what I heard convinces me that this is an area in which the application of DSP can make a significant contribution to fidelity.”



Personally, I have tested linear-phase subwoofers quite extensively and published the results on my website. I used 2-5ms pulse, bi-polar pulse, square wave, and LFE from movies. The linear-phase bass remains seismic, deep and powerful, but is also tight and has punch to it now. In short – this bass is accurate.

Latency options are explained in http://www.bodziosoftware.com.au/UE7_Manual.pdf Page 5.

Contemporary Intel CPU runs comfortably 8in/16out DSP FIR engine with bass resolution of 1.47Hz at 96kHz. So there are absolutely no problems with processing power or performance.


I really do not have anything more to add.

Best Regards,
Bohdan
 
#62
Thank you for your sales pitch Bohdan. I would also would like to wrap up the FIR discourse here for now. I would advise anyone to look for information that is as objective as possible, or even perform blind listening tests. Siegfried Linkwitz published a list with considerations, also regarding the issues discussed here.
Frontiers
 
#67
I found the ringing problem at work, listening at headphones, i can clearly hear a difference when DirectSound or WASAPI is used. With Direct Sound, there is a problem. (my track to clearly hear this ringing is '(02) [Stan Getz and the Oscar Peterson Trio] Pennies From Heaven.flac' from album '1957 - Stan Getz and The Oscar Peterson Trio', at the beginning until second 15, when the chords of piano are hit)
SXQ is working at Direct Sound level?

I mean, if i tell Foobar to output to WASAPI Virtual Cable, in the end the processing by SXQ is done at Direct Sound level and then output to my USB card?
 
#68
Hello Arcgotic,

Ill just try and give you some answers regarding the last posts..

- SXQ only interfaces at WASAPI level, which is the lowest level interface at Win7. DirectSound is implemented atop WASAPI.

- Regarding your device channels issue: Did you configure the device in Windows as 6 channel (I suppose so, as it used to work fine IIRC). It is possible that Windows shuffles the device order after re-installations etc. If you select the SXQ I/O devices again that will be solved.
 
#69
Deodato,

I've downloaded the software (RAR file) to check it out. Have not yet installed the VAC. I extracted everything to a new directory. I could get SXQ to run.

When I tried to configure the software by pointing my browser to the address 'http://localhost:8080/pf.html' I get the error message 'Access Error: 404 -- Not Found. Cannot open document for: /pf.html'.

Can you help me get past this error?

Thanks,

-Charlie
 
#76
Deodato said:
Do you see SXQ.exe in the task manager?
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Yes
Deodato said:
How many threads?
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If you are asking how many threads my computer can run simultaneously, I believe 12. I have an i7-4930K CPU with 6 cores...
Deodato said:
Is port 8080 already in use?
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Not sure... how can I check that?

I installed the Virtual Cable driver in case that was the source of the problem. The install seemed to go fine and I rebooted my machine as suggested by the installer. I can see "CABLE INPUT (VB-Audio Virtual Cable)" listed in one of my players, so it seems to be installed. But I do not see the additional volume controls from the V-cable or SXQ in the taskbar area (this is mentioned on the SXQ web page).

I tried running SXQ as administrator. No change.

I explicitly gave permission for SQX to pass through the Windows Firewall to both private and public netwoks. No change.
 
#80
This is still showing up in the port scan without SXQ running:
CharlieLaub said:
Can not obtain ownership information
TCP 0.0.0.0:8080 AVA-413545-1:0 LISTENING
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That might have been the problem...

I tried to pull up the configuration page using address 127.0.0.1 instead of localhost but it was also 404. I don't see that explicit port assignment with my current SXQ version. Maybe when SXQ tries to set up the server at 0.0.0.0:8080 and can't it throws an internal silent error and halts? Might this explain why there is no SXQ volume control appearing anywhere?

Let me know when I can try the updated version with the web server running at that address. Thanks for all your help.

-Charlie
 
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