Trinnov Altitude / JBL SDP-75

[QMuse]

That's the problem and probably why FIR is rare in AVRs

Yes, that is the reason.

 

[QMuse]

Makes sense... Most systems I have seen do not delay the video as there is usually so much more delay in video processing that audio always "hits" first. Stick in some 100 ms FIR filters and likely that is no longer true... Where I have run into latency issues in audio is on the recording side or DAW (digital audio workstation) when you introduce filters in one channel and all of a sudden transients get a little "smeared".

Just as an example: FIR filters I'm using have 65536 taps at 44.1kHz and have delay of 743ms. They do the job very nicely at LF but such delay would cause issues with lipsync.

 

[mitchco]

Makes sense... Most systems I have seen do not delay the video as there is usually so much more delay in video processing that audio always "hits" first. Stick in some 100 ms FIR filters and likely that is no longer true... Where I have run into latency issues in audio is on the recording side or DAW (digital audio workstation) when you introduce filters in one channel and all of a sudden transients get a little "smeared".

Makes sense for AVR's but I watch movies too and using JRiver takes care of the FIR filter delay, so there are no lipsync issues. EDIT: and really shines though on movies with good low frequency content. For example, the Sony intro (is the new THX intro) to Spider-Man: Into the Spider-Verse ramps up like the room is going to explode - literally the whole house shakes with the waves as my subs get down to 6 Hz. Lot's of fun!

 

[fitero]

I only have one anecdotal experience with the SDP-75. A buddy recently got a SDP-75 and a pair of M2s. We set is up as best we could until the guy from Harman could come and do the full calibration of the unit/speakers/room. We both make a living installing home theater and stereo gear. Frankly, before the Harman calibration was accomplished we both were somewhat let down with the quality of music compared to that from his previous JBL K2 S9900 speakers and Lexicon MC 12 HD Processor.

Once the Harman calibrator finished I began to listen to favorite tracks. We were both floored. Wow. I've never heard a stereo, much less a surround sound room sound this good. Listening through favorite music via Auro 3D was even more fun. Oh, and I have a pair of M2 speakers in my much more modest stereo system at home, so I am used to hearing them.

I would never have purchased a surround sound processor for a stereo system. Now, I honestly believe that my buddy's system is as stellar as a stereo system as well as a gut wrenching Home Theater system. That is a novelty for this calloused melophile.

 

[QMuse]

Makes sense for AVR's but I watch movies too and using JRiver takes care of the FIR filter delay, so there are no lipsync issues.

Jriver has some nice software algorythms to fix it within video player and horsepower of processors in PC to do it. Not so with AVRs..

 

[Olli]

Makes sense for AVR's but I watch movies too and using JRiver takes care of the FIR filter delay, so there are no lipsync issues.

If only Jriver would support Atmos/Auro etc...

 

[DonH56]

I only have one anecdotal experience with the SDP-75. A buddy recently got a SDP-75 and a pair of M2s. We set is up as best we could until the guy from Harman could come and do the full calibration of the unit/speakers/room. We both make a living installing home theater and stereo gear. Frankly, before the Harman calibration was accomplished we both were somewhat let down with the quality of music compared to that from his previous JBL K2 S9900 speakers and Lexicon MC 12 HD Processor.

Once the Harman calibrator finished I began to listen to favorite tracks. We were both floored. Wow. I've never heard a stereo, much less a surround sound room sound this good. Listening through favorite music via Auro 3D was even more fun. Oh, and I have a pair of M2 speakers in my much more modest stereo system at home, so I am used to hearing them.

I would never have purchased a surround sound processor for a stereo system. Now, I honestly believe that my buddy's system is as stellar as a stereo system as well as a gut wrenching Home Theater system. That is a novelty for this calloused melophile.

Good feedback. On-site or remote calibration?

Edit "guy... could come" so I assume on-site. Did you have someone from Harman come or was it one of the "other" guys? I only know of a couple or three calibrators that always seem to be mentioned.

 

[QMuse]

I only have one anecdotal experience with the SDP-75. A buddy recently got a SDP-75 and a pair of M2s. We set is up as best we could until the guy from Harman could come and do the full calibration of the unit/speakers/room. We both make a living installing home theater and stereo gear. Frankly, before the Harman calibration was accomplished we both were somewhat let down with the quality of music compared to that from his previous JBL K2 S9900 speakers and Lexicon MC 12 HD Processor.

Once the Harman calibrator finished I began to listen to favorite tracks. We were both floored. Wow. I've never heard a stereo, much less a surround sound room sound this good. Listening through favorite music via Auro 3D was even more fun. Oh, and I have a pair of M2 speakers in my much more modest stereo system at home, so I am used to hearing them.

I would never have purchased a surround sound processor for a stereo system. Now, I honestly believe that my buddy's system is as stellar as a stereo system as well as a gut wrenching Home Theater system. That is a novelty for this calloused melophile.

It would be interesting if you can post measurements after yours and his correction.

 

[maverickronin]

Just as an example: FIR filters I'm using have 65536 taps at 44.1kHz and have delay of 743ms. They do the job very nicely at LF but such delay would cause issues with lipsync.

Is the latency a strictly function of the number of taps or can you reduce it with more processing power?

 

[DonH56]

Is the latency a strictly function of the number of taps or can you reduce it with more processing power?

Taps and sampling rate...

 

[fitero]

Good feedback. On-site or remote calibration?

Edit "guy... could come" so I assume on-site. Did you have someone from Harman come or was it one of the "other" guys? I only know of a couple or three calibrators that always seem to be mentioned.

It was a Harman person. They keep the calibration results for themselves so I have no resultant data that I can share.

 

[maverickronin]

Taps and sampling rate...

OK so I found this...

The formula is simple: given a FIR filter which has N taps, the delay is: (N – 1) / (2 * Fs), where Fs is the sampling frequency. So, for example, a 21 tap linear-phase FIR filter operating at a 1 kHz rate has delay: (21 – 1) / (2 * 1 kHz)=10 milliseconds.

Can you just upsample to reduce latency or does that require more taps to get the same effect leaving you back where you started?

 

[DonH56]

It was a Harman person. They keep the calibration results for themselves so I have no resultant data that I can share.

Got it, thank you. I am in contact with my dealer and a (the?) Harman calibrator, just need to find a time we can all get together (more or less -- on the phone).

 

[DonH56]

OK so I found this...

Can you just upsample to reduce latency or does that require more taps to get the same effect leaving you back where you started?

If you want to correct X ms then you need that much worth of filter taps so your instinct is correct. If you upsample by two and still want to correct to 10 Hz (or whatever) you'll either need more taps or a structure that reduces the number of taps but maintains the same time span (so less resolution). There are also floating-tap schemes that allow you to place taps further "out" in time without having to have all the taps between. That is useful when you have reflections; some taps at the time of first arrival, then another batch around the first reflection point. Audio, sonar, lidar, radar systems use such arrays, along with some SerDes (chips inside your computer that sends data around, e.g. PCIe and SATA links). But latency doesn't usually change because you need to process X ms of data to correct that much range.

Processing power comes into play because something has to do all those multiplications for all of those taps so greater processing power can potentially enable more taps or more channels if needed.

 

[mitchco]

It would be interesting if you can post measurements after yours and his correction.

It would be, but I suspect it would be similar to what @Olli has already shared... The SDP-75 manual states that IIR is in use for low frequencies... so no excessphase correction for room modes. And the 100ms FIR filter setting that seems to only come on after 150Hz (manual is confusing).

@Olli yes, JRiver does not decode Atmos and so no choice if Atmos is a must...

 

[North_Sky]

Haha I would suggest the smaller the room, the more low frequency excessphase correction is required to smooth out the low frequency reflections. i.e. typically the smaller the room worsens the peaks and dips so you get +20 dB or more SPL variation at low frequencies below Schroeder. Of course, room ratio plays a major role as well as size.

As far as the h/w devices are concerned, the filter tap limitation can't be overcome as it is fixed by the DSP devices being used.

The other issue is IIR versus FIR. Unfortunately, IIR filters (PEQ's Biquad's, whatever) don't have any excessphase correction capabilities at low frequencies and therefore are not the best design for "room eq/correction." So it is a double whammy in the low end, not enough filters taps and of the wrong filter type...

Any audio manufacturer that make affordable audio hardware (pre/pros, AV receivers) with the proper software (DSPs, DACs, Room EQ system ... implementation) in one component? ...Or better go with separates; amp, preamp, Room EQ box?

Two, why are they using inferior Room EQ systems and charging a pretty sum.
...Top Denon/Marantz, NAD, Arcam, McIntosh, JBL, Trinnov Altitude, Steinway Lyngdorf, Storm Audio, Bryston, Anthem, Audio Control, Focal Astral, Legacy Audio, Emotiva, Yamaha, Krell, ...

Any good?
• http://lyngdorf.com/roomperfect/

Which audio manufacturer uses Acourate and/or Audiolense?
It's a separate software (app)?

• http://archimago.blogspot.com/2019/10/2019-update-basic-acourate-dsp-room.html

• https://audiophilestyle.com/forums/topic/38985-my-honest-review-of-acourate/

Requirement? Classes in mathematics, physics, sciences, chemistry, computer engineering, ... something easy to operate, simple setup, adjust, fine tune, auto, verification, and forget.

• https://www.thewelltemperedcomputer.com/SW/AudioTools/RoomCorrection.htm

• https://community.roonlabs.com/t/room-correction-with-acourate/22544/60

 

[Kal Rubinson]

The issue with these h/w devices is the number of filter taps available that limits the the effectiveness of their low frequency correction.
...............................................................................................................................
If I remember, the Trinnov has 4096 taps (better than miniDSP 2x4) with a maximum filter length of 100ms. I believe the JBL SDP-75 is similar...

How does this apply to the various Trinnov prepros? They range widely in features and number of channels.

 

[maverickronin]

If you want to correct X ms then you need that much worth of filter taps so your instinct is correct. If you upsample by two and still want to correct to 10 Hz (or whatever) you'll either need more taps or a structure that reduces the number of taps but maintains the same time span (so less resolution). There are also floating-tap schemes that allow you to place taps further "out" in time without having to have all the taps between. That is useful when you have reflections; some taps at the time of first arrival, then another batch around the first reflection point. Audio, sonar, lidar, radar systems use such arrays, along with some SerDes (chips inside your computer that sends data around, e.g. PCIe and SATA links). But latency doesn't usually change because you need to process X ms of data to correct that much range.

Processing power comes into play because something has to do all those multiplications for all of those taps so greater processing power can potentially enable more taps or more channels if needed.

I think I've already had this conversation with someone else but I just didn't remember the answer...

Anyway, the reason I was even interested in the latency was to know if FIR correction filters could be used for gaming besides home theater and straight music but I guess not.

 

[mitchco]

See answers in line...

Any audio manufacturer that make affordable audio hardware (pre/pros, AV receivers) with the proper software (DSPs, DACs, Room EQ system ... implementation) in one component? ...Or better go with separates; amp, preamp, Room EQ box?

Two, why are they using inferior Room EQ systems and charging a pretty sum.
...Top Denon/Marantz, NAD, Arcam, McIntosh, JBL, Trinnov Altitude, Steinway Lyngdorf, Storm Audio, Bryston, Anthem, Audio Control, Focal Astral, Legacy Audio, Emotiva, Yamaha, Krell, ...

Good question! Personally, I would not be buying any of these as they all suffer the same issues... more here: https://www.audiosciencereview.com/...ssey-room-eq-review.12746/page-10#post-380033

Any good?
• http://lyngdorf.com/roomperfect/

Amir reviewed it, liked it, but as one can see in the review, there is still 15 dB of peak to peak variation in the low end... Acourate and Audiolense can do better, not only in amplitude, but also correcting the excessphase at low frequencies towards a minimum phase target (i.e. ideal speaker response). This is what gives it the clear, focused bass sound.

Which audio manufacturer uses Acourate and/or Audiolense?
It's a separate software (app)?

Yes.

• http://archimago.blogspot.com/2019/10/2019-update-basic-acourate-dsp-room.html

• https://audiophilestyle.com/forums/topic/38985-my-honest-review-of-acourate/

Requirement? Classes in mathematics, physics, sciences, chemistry, computer engineering, ... something easy to operate, simple setup, adjust, fine tune, auto, verification, and forget.

• https://www.thewelltemperedcomputer.com/SW/AudioTools/RoomCorrection.htm

• https://community.roonlabs.com/t/room-correction-with-acourate/22544/60

There are a number of step by step guides that I have written for Audiolense, Acoruate and Dirac on my website under the DSP tab... I also wrote a book on the subject using Acourate as the example software used for the DSP concepts.

For sure, takes some effort and understanding as to what is really going on behind SOTA room correction. I wrote a basic article on it here:
http://www.enjoythemusic.com/magazi...g_Digital_Room_Correction_For_Audiophiles.htm

Sorry @DonH56 no more off topic from me.

 

[North_Sky]

Audyssey MultEQ XT32: 512 filter taps on the subwoofer(s) ... FIR (Finite Impulse Response)

Trinnov Alitude32: https://www.trinnov.com/altitude32/