Phase adjustment on Sub - Which frequency?

[dweeeeb2]

I'm attempting to get a better grip on room equalization and of course phase can be a useful variable for this. On my sub I have a phase dial and I've played around with it and noticed it making a difference. But it got me thinking, what is the typical association between the phase dial and the multitude of frequencies produced? Are they all phased by X deg? I've always assumed this to be the case but thought I'd ask.

 

[ernestcarl]

I'm attempting to get a better grip on room equalization and of course phase can be a useful variable for this. On my sub I have a phase dial and I've played around with it and noticed it making a difference. But it got me thinking, what is the typical association between the phase dial and the multitude of frequencies produced? Are they all phased by X deg? I've always assumed this to be the case but thought I'd ask.

Probably just a variable all pass filter instead of a time delay setting like the one on a miniDSP,: https://www.audiosciencereview.com/...ase-control-on-a-subwoofer.20889/post-1107433

Importance of the sub's phase adj. is going to be relative to your reference (i.e. main monitors).

 

[dweeeeb2]

Thanks, god I've got soo much to learn.

So, is it recommended to use the dial on the sub or use the DSP?

I've noticed some people simply altering the sub distance in their AVR's. I can see this effectively changing the phase at MLP but isn't it also effecting timing at the MLP? Sorry if this question is getting too big.

 

[ernestcarl]

Thanks, god I've got soo much to learn.

So, is it recommended to use the dial on the sub or use the DSP?

I've noticed some people simply altering the sub distance in their AVR's. I can see this effectively changing the phase at MLP but isn't it also effecting timing at the MLP? Sorry if this question is getting too big.

The variable (APF) "phase" adj. knob should not affect the "timing" of the sub at the MLP. It just increases the steepness/angle of the phase at a certain center frequency akin to what happens when you apply a HPF to your mains, for example.

I would leave it at 0 or untouched if I have some other means of applying DSP. "Altering the sub distance" in the AVR or DSP hardware/software device is the same as adding x ms of time delay.

I suggest simulating an APF or HPF etc. using REW EQ window and Overlays window view:

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Two examples of delay and polarity adj. made ~vs~ individual channel (mixed phase) FIR EQ correction:




First alignment = 3.19 ms delay added to main FR channel

Second alignment = 1.76 ms delay added to the subwoofer channel (FIR EQ was still linearizing the sub's phase! -- I forgot to disable it here)

Don't remember the individual delays used for that last one, but ~341ms of FIR EQ processing delay (32k tap at 48kHz) was the cost -- practical online streaming video playback there won't work well due to the lip sync mismatch.

 

[dweeeeb2]

Thankyou I’ll play around

 

[dualazmak]

I essentially agree with @ernestcarl's nice suggestions.

For better/best optimization of XO parameters between your subwoofer(s) and main speakers (woofers), I believe you need to measure your in-room air sound using measurement microphone at your listening position.

First, for determination of best XO Fq and the two XO slopes (low-pass for sub, high-pass for woofer), I would like to suggest you to objectively measure the transient behavior/characteristics of your sub and woofer around the possible XO Fq zones, usually 50 Hz - 120 Hz zone. It is critically important that phase/polarity "invert or not" for sub(s) would be dependent on the selection of the slopes; you usually need to invert subs e.g. if you would use second order (-12 dB/Oct) slope for both filters (usually Butterworth or Linkwitz-Riley, I always prefer the latter) at XO Fq. (Many of the DSP software nicely show you the "theoretical SPL curve" reflecting the selected slopes and "invert or not" so that you may easily select either of "invert or not" upon your XO slopes selection.)

Spoiler: just for example...

- Measurement of transient characteristics of Yamaha 30 cm woofer JA-3058 in sealed cabinet and Yamaha active sub-woofer YST-SW1000: #495, #497, #503, #507
and, example of "invert" settings;

In case if your sub(s) have remote or on-box "reverse/invert" button/switch, you should try both (invert it or not), at your listening position after finishing these XO parameter optimization since the best choice between the two would be greatly dependent on your room mode (house acoustic environment) and distance from SPs to your ears.

Second, then you may proceed to precise time alignment, less than 1.0 msec precision for sub and woofer, using validated reproducible objective method.

Spoiler: just for example...

- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-1_ Precision pulse wave matching method: #493
- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-2_ Energy peak matching method: #494
- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-3_ Precision single sine wave matching method in 0.1 msec accuracy: #504, #507
and you can observe/see semi-objectively/semi-quantitatively the delay features and room modes using REW's wavelet analysis; ref. here and here for validation as well as here and here before my precise time alignment.

Third, then you may finally carefully adjust/optimize the relative gains for sub and main SP (woofer) depending on your prefered in-room/house SPL curve which would be also depending on your music/genre preferences; I assume it would be nice for you implementing safe and flexible on-the-fly (I mean while listening to music) relative gain control between sub and main SP, more preferably between all the SP drivers including your subs.

Spoiler: just for example...

- Frequency (Fq) responses in the completed system measured by using “cumulative white noise averaging method” under the present standard crossover configurations and relative gains_Part-6_Summary, discussions, and a little step forward: #404, #405-#409
- A serious jazz fanatic friend came to my home for audio sessions using my multichannel multi-driver multi-way multi-amplifier stereo system: #438
- Excellent Recording Quality Music Albums/Tracks for Subjective (and Possibly Objective) Test/Check/Tuning of Multichannel Multi-Driver Multi-Amplifier Time-Aligned Active Stereo Audio System and Room Acoustics; at least a Portion and/or One Track being Analyzed by Color Spectrum of Adobe Audition in Common Parameters: [Part-11] Violin Music: #643

In this context, I usually fix the gain of my L&R subs at rather high level (as my base reference gain level), and flexibly adjust relative gains for other SP drives; the master sound volume for all the SP drivers would/should be controlled by the most upstream music player (in digital domain in my case, ref. here).

 

[dweeeeb2]

Thankyou very much guys. I haven’t got my dsp yet. I’m just playing around with REW. Hopefully I’ll have my unit in a couple of weeks. Ill be referring back here, thank you

 

[dualazmak]

Thankyou very much guys. I haven’t got my dsp yet. I’m just playing around with REW. Hopefully I’ll have my unit in a couple of weeks. Ill be referring back here, thank you

In case if you would use software audio player in PC or Mac (or even smartphones), you can easily test/implement system-wide "DSP software" (in my case "EKIO") for very much flexible XO/EQ/Group-Delay/Relative-gain controls even in case of using single stereo DAC and single passive (having passive LCR network) SP system and subwoofer(s); highly recommended for your tests and evaluations. In this case, you have no need of implementing physical hardware DSP unit.

Do you plan to have your "DSP unit" in analog domain? If this would be the case, you will do ADC-DSP-DAC processing which is usually inferior (in several reasons) to upstream on-OS DSP feeding into DAC (I mean only one DAC processing in the signal chain).

 

[dweeeeb2]

In case if you would use audio player software in PC or Mac (or even smartphones), you can easily test/implement system-wide "DSP software" (in my case "EKIO") for very much flexible XO/EQ/Group-Delay/Relative-gain controls even in case of using single stereo DAC and single passive (having passive LCR network) SP system and subwoofer(s); highly recommended for your tests and evaluations. In this case, you have no need of implementing physical hardware DSP unit.

I’m waiting on the miniDSP HTx. I considered PC but I could not find a solution for sub out or for watching tv (in a family friendly interface) It surprised me how hard it was to find dsp solutions. The HTx should be plug and play any source.
I have been playing around with equalizer APO and REW for headphone eq.
It feels like Im on the edge of a very deep rabbit hole and am weary of getting too fixated on the numbers, Im hoping the HTx will get the job done without me needing another degree!
thankyou for your assistance.

 

[dualazmak]

I considered PC but I could not find a solution for sub out or for watching tv (in a family friendly interface) It surprised me how hard it was to find dsp solutions.

Just for your reference,,,

When I would like/need watching/hearing a TV channel with excellent audio handring, I take a kind of reverse-thinking approach where I use my 55-inch 4K resolution OLED TV (actually Panasonic TH-55HZ1800) as my second PC monitor (visual only, HDMI connection from my PC) of 4K resolution and TV channel is played by software TV tuner which can receive all the available TV channels through internet optical fiber (we call it as optical TV); the audio signal of the TV channel is digitally fed into my system-wide DSP center "EKIO" for multichannel DSP processing to be played by my multichannel multi-SP-driver multi-amplifier audio rig.

If you would be interested in this TV watching/listening scheme, please refer to my post here. You may also find here my latest such audio and TV setup in detail.