A1 Evo AcoustiX - custom filters on Denon X1800H (potential bug)

[wanjce]

Hi @OCA , thanks for AcoustiX. On my Denon X1800H, I noticed that no matter what combination of settings/filters I try, the custom filters only get applied to the Surround Left channel on my 5.2 system. Flipping between Flat/Reference audyssey profiles does not change the sound of FL, C, FR or SR; just SL. I've tried extremely audible -12dB and -24dB filters (HS and PK) for testing purposes to no avail.

I've eliminated:
1. User error. I create custom filters using REW EQ as intended and described in the OCA's video. SL gets consistently applied as intended.
2. Transfer errors. According to the logs, there are none.

I have not eliminated:
1. A glitch/bug with regard to the AVR model.
2. A bug in the AcoustiX code.

Can anyone else with the Denon X1800H reproduce this? @OCA have you witnessed this so far?

 

[wanjce]

A1EvoAcoustiX_Jul28_0035.zip

drive.google.com

Here are the files for debugging purposes. The FL channel is the only one differing between Flat/Reference, for testing purposes. All these files are openable by JSON readers.

 

[OCA]

If you are trying to add custom filters below 375Hz, they will be ignored, not by A1 Evo but by the device itself. X1800H is MultEQ Basic and as such can only process 128 taps of FIR filters at 48kHz sampling rate giving it a filter resolution of only 375Hz. If you have bass EQ, apply it on the sub. It gets pretty high resolution even in multEQ basic.

This doesn't eliminate the possibility of a bug in the code though if your filters were already above 375Hz. I will look into it when I can, deeply involved in a new app release at the moment.

 

[wanjce]

If you are trying to add custom filters below 375Hz, they will be ignored, not by A1 Evo but by the device itself. X1800H is MultEQ Basic and as such can only process 128 taps of FIR filters at 48kHz sampling rate giving it a filter resolution of only 375Hz. If you have bass EQ, apply it on the sub. It gets pretty high resolution even in multEQ basic.

This doesn't eliminate the possibility of a bug in the code though if your filters were already above 375Hz. I will look into it when I can, deeply involved in a new app release at the moment.

Thanks, I was adding filters above 375Hz..

Looking at the .oca file, it seems the FL channel is the only one correctly receiving some filter in Reference that's different from its Flat filters. But it either isn't the correct custom filter in terms of frequency/Q, or isn't getting transferred to my X1800H, or isn't getting applied correctly. There's no audible difference and there should be, clearly, if you check the FL EQ in .mdat. It's an extremely audible filter.

If I instead apply the same filter but to the SL channel - it works seemingly as intended. SL is the only channel that gets custom filters applied in my setup.

 

[OCA]

Since the new app will be strictly for XT32 models only, I am planning to make some improvements in A1 Evo AcoustiX specifically for multEQ Basic and XT models and that custom filter bug is also duly noted in the to do list.

 

[wanjce]

Since the new app will be strictly for XT32 models only, I am planning to make some improvements in A1 Evo AcoustiX specifically for multEQ Basic and XT models and that custom filter bug is also duly noted in the to do list.

Thanks.

From what I could gather, there are three tiers: MultEQ, XT and XT32. I think my X1800H has the middle one (XT); I can see non-LFE outputs limited to about 90Hz crossovers. I guess 375Hz is the limit for the basic MultEQ.

 

[wanjce]

...or simply shell out more for a solid receiver with the top-tier Audyssey XT32 in it.

@OCA is it fair to say that AcoustiX was developed with XT32 in mind, primarily?

 

[OCA]

Thanks.

From what I could gather, there are three tiers: MultEQ, XT and XT32. I think my X1800H has the middle one (XT); I can see non-LFE outputs limited to about 90Hz crossovers. I guess 375Hz is the limit for the basic MultEQ.

Yes I stand corrected, your model is XT and its speaker resolution is higher with 512 taps at 48kHz (93.75Hz minimum)

 

[OCA]

...or simply shell out more for a solid receiver with the top-tier Audyssey XT32 in it.

@OCA is it fair to say that AcoustiX was developed with XT32 in mind, primarily?

It's not AcoustiX, it's Audyssey/D&M leaving XT and Basic models unable to use proper EQ for speakers. XT is manageable but you need to set crossovers at 90-100Hz minimum so all bass is managed by the sub but for the basic, there's by design a non-correctable gap between 250Hz and 375Hz even when you crossover all speakers at 250Hz and leave bass below that to the sub.

XT32 only has double the filter taps of XT but it processes filters through multi-rate decimation. With that technique, 1,024 taps are more than enough to EQ the full range efficiently because lower frequencies are down-sampled. Dirac ART uses the exact same approach with the same tap count. But they omitted multi-rate decimation from XT and Basic entirely, forcing those models to process filters at a fixed high rate. Since that restriction is baked into the AVR firmware, there's nothing A1 Evo can do but replicate the same crippled procedure.

 

[wanjce]

It's not AcoustiX, it's Audyssey/D&M deliberately leaving XT and Basic models unable to use proper EQ for speakers. XT is manageable but you need to set crossovers at 90-100Hz minimum so all bass is managed by the sub but for the basic, there's by design a non-correctable gap between 250Hz and 375Hz even when you crossover all speakers at 250Hz and leave bass below that to the sub.

XT32 just uses only double the taps of XT for speakers but correctly processes filters through multi-rate decimation where 1024 taps end up more than enough to EQ all frequencies efficiently by down-sampling lower frequency regions. Even Dirac ART uses the same 1024 taps per speaker with the same technique. But somehow, they decided to skip that technique altogether for XT and Basic models and their filters are processed at a fixed high frequency rate. When it has no reverse in the AVR firmware, there's nothing A1 Evo can do but just replicate the procedure.

Understood, what I meant was - if I had the XT32, would the Custom Filters work as intended?

 

[OCA]

Understood, what I meant was - if I had the XT32, would the Custom Filters work as intended?

Yes, there's no reported bug in XT32 custom filter processing. But it should work also with XT (if above 90Hz) so that's something I need to fix.

 

[OCA]

Btw, you should not need (and probably shouldn't since these are min phase filters that will suffocate the sound above the room transient) to add custom filters if you use "Interactive target leveling" option in the custom menu to adjust bass/treble balance.

 

[wanjce]

Btw, you should not need (and probably shouldn't since these are min phase filters that will suffocate the sound above the room transient) to add custom filters if you use "Interactive target leveling" option in the custom menu to adjust bass/treble balance.

Thanks, could you explain that a bit more?

What I'm trying to achieve is a more cinematic, darker sound, possibly with a High Shelf around 2-5kHz, sloping downward. Kinda like the "Cinematic EQ" setting by Denon, but less aggressive. Ideally, I'd be able to darken the Surround L and R more than the fronts (independently), because these are 40-50cm from my ears and are way too bright (given the default setup cranks them up).

I've tried using a custom-made target curve, but naturally, AcoustiX doesn't correct anything past a 500Hz maximum.

 

[OCA]

Try the advice above and you will understand. Move the calculated target 1-2 dB up using buttons in the pop up window.

 

[wanjce]

Try the advice above and you will understand. Move the calculated target 1-2 dB up using buttons in the pop up window.

I understand, but that doesn't correct >500Hz?

I think what I'm after is a high shelf slope.

 

[wanjce]

@OCA just FYI, I've tried:
- factory reseting my X1800H
- transferring the .oca to the AVR using Acoustica instead of AcoustiX

...and the custom filters still didn't get applied aside from Surround L. Hope this helps narrow the problem down.