How to use phase to better align subwoofer
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- čas přidán 9. 11. 2023
- A little trick I found while playing with time alignment.
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Excellent subject of phase alignment
Excelente información como siempre. Gracias por compartir esos pequeños detalles pero que hacen la diferencia
Great video
I prefer REW (you know this). I find the "level phase at cursor" very helpful to match slopes.
Wow !!! Great video
This is crazy! Thanks!!!!
GOOD INFORMATION SIR THANKS
Can’t wait to play with my new Alpine c60 dsp
If you really want to go down a rabbit hole learning about phase and phase coherency, try reading up on the LeCleach method. I don’t really understand it but here’s a simplified version I copied and pasted from Diymobile.
“As it turns out there’s a method to maintain phase coherence throughout the system when using LR 24 crossovers.
Every high-pass/low-pass filter in the system needs to be represented in every driver, in one form or the other.
For 80-300-2700 Hz crossover points, the set up would be as follows:
Sw-80 Hz LPF, 300 Hz 2nd-order all-pass, 2700 Hz 2nd-order all-pass (0.707Q on all-pass)
MidBass- 80Hz HPF, 300 Hz LPF, 2700 Hz 2nd-order all-pass (0.707Q on all-pass)
MidRange-300Hz HPF, 2700 Hz LPF, 80Hz 2nd-order all-pass (0.707Q on all-pass)
Tweeter-2700 Hz HPF, 80 Hz 2nd-order all-pass, 300 Hz 2nd-order all-pass, (0.707Q on all-pass)
This may require flipping polarity on every other driver set: MidBass inverted, Tweeter inverted.
Remember, Linkwitz-Riley 24 db/octave xovers and 2nd-order all-pass with 0.707 Q.
This one is definitely less complicated than the LeCleach method. Try it!”
Personally I haven’t tried it yet mainly because I don’t quiet understand the concept. Maybe Nerijus can do a video on it. 😀
I checked with Helix, without all-pass the phase will only change at drivers x-over point. With all-pass filter as you mentioned, at every xover point the phase will change, that will have all drivers in phase.
I was going to buy Dirac Live for my MiniDSP 8x12, figuring it would get my system close enough to sounding good (I won't be competing), and I want to setup multiple tunes. But I'm starting to think it would be better to buy the additional equipment I need to test and tune the car myself. I enjoyed tuning with the limited Dayton DSP in my last build, but since I don't compete, I don't really know if it "sounded proper" since I didn't have a reference.
I'm literally in the same boat with same DSP. Don't know which route to take.
Hi! I've been following your videos since 3 months ago. Great videos by the way! I have a trick for you to test, look at @10:11 and watch your graph, your sloping down green line's degree of inclination is not the same as the brown/orange one. Now the trick: match the degree of inclination between both slopes and watch your phase graph (meaning adjusting the crossover slope from eg. 24dB/oct to 18db/oct or whatever), make the two to have the same inclination. Another trick, use Open Sound Meter app to speed up your tuning speed.
Thanks for the advice ! So is it correct that from one highpass to the other lowpass u can get correct phase if they both have the same incline ? But wouldn’t this imply that the sub need to have a higher bandwidth. Isn’t it better than to cut a bit more from the brown front sub and give it a higher acoustical slope? But if the back sub is crossed steeper it would imply that he supports the front sub less. It the other way round with a steeper highpass from the front sub it would support the back sub less ?
@@Niclas0299 a filter in digital domain works by shifting phase at a frequency, so to have a good phase alignment you will need to have a similar slope. A properly made subwoofer driver should have more than enough bandwidth if we are talking about ~100hz or less, so it should not be a problem. And yes, you can either cut more from the brown curve or change the green curve to have less incline, make the incline as similar as possible. Difference in filter steepness will result in more phase problems, not which driver supports which driver...
@@zzz2496Thanks for your response ! I know it is a typical myth that you need to cross your midbass low to get more low end. I personally have a acoustical crossover at 80hz on midbass. It harms my subbass more when I cross it lower to (support) my subwoofer. So this is a result of phase issues. My midbase cancels out some of the reponse of my subwoofer and the opposite happens. It takes spl away and my sub can be located rather than integrated. Somehow I have seen that the other way round it can be beneficial to cross the subwoofer higher to support the midbass. Now there are phase issues which can be reduced by switching the phase slightly. If both subs back and front are in phase the sub in the back ads up to the front and everything is perfect.
That's the thing, my infinite baffle rear sub is at it's limits with the bandwidth. The crossover is like 80Hz just to cut the top off, but the response itself acts as a 55Hz low pass. So changing the slope is not an option in my case.
@@RAW-CAt you can change the slope for the brown driver to match (if possible).
I'm still learning about phase adjustments. My DSP does not offer that option (other than flipping 180°), but my new amplifier does have an adjustable phase knob for the sub channel. I was just going to play with it and see if I can hear a difference. Lol
Could you hear a difference before and after your adjustment?
I cannot speak for him but for me the difference of in phase and out of phase is a huge one because you will 1. be able to integrate it to the front and get the back sub on your soundstage. 2. you will get more spl because both ad up. So your bass gets richer and your back sub does not catch your attention anymore when it plays a little louder. So that’s my experience I’m excited to hear other options. And correct me if I’m wrong ! I’m still learning
So in your case you would just add delay to the entire front stage if the above phase response was what showed up and you didn’t have the ability to adjust phase (this is just a calculated all pass with a centre frequency at the subs low pass crossover point and a q made to shift phase by x amount)
Is there anyway to do this with a umik-1? I do have a focusrite 2i2 and an smsl po100 if that's of any use.
Seeing a schematic of your focusrite wiring would be helpful. I could get an xlr mic if that made it more simple.
You need the 2i2, an XLR and a loopback.
@@RAW-CAt thanks. I'll get one and do some testing. Thanks.
Do you know if the electrical phase in the helix software has any meaningfulness ? Or is it only the acoustical phase that matters. If have not much clue about phase in general other than from what I see after measuring. I always have looked if my sub and speakers are in phase only by watching if speakers ad up in spl. From speaker to speaker and from left side to right side. But does the electrical phase information from helix provide any value ? Another problem I have is that my midbase speakers get their power not from my match up 8 amplifier but from a powerful 2 channel and my subwoofer is bridged with another 2 channels from the same amp (4 channel ESX QE900.4) the sub is connected via RCA to the DSP and the midbase is connected via high level. So both can be equalized but neither of them can be phase adapted other than 180 degrees and time aligned. I saw that if I time align my midbase with sub right and switch polarity by 180 degrees they sum up perfectly. But I get a new sub soon and I want to know if I can do anything to have the option to correct phase with slider in the dsp. Can anybody help me with that 😢
Not really. Acoustical phase is what matters. Amps can change phase as well
@@RAW-CAtthank you very much for the quick answer. Btw I made a pillars for my car and thanks to your video they became beauty’s. I first tried it with cloth and failed like you did. So I used raptor Bedliner and now it looks wonderful. 😊
Its hard to say without more information, but when it comes to subs, there are other factors that may lead you to believe you have a phase issue, when that's not necessarily the case. Check your subwoofer placement. Just try them in different locations and see how they sound. Even put them in places where they won't end up. The goal is just to see how much placement is effecting performance. Small changes can make a big difference. After you try several locations, you now have references. If you can't put the subs where they sound best, try to place them as close as you can to your best reference.
Another thing that is a potential red flag is your bridged amps. When you bridge 2 channels into one, its not a mono amp. Its a bridged 2 channel amp. A bridged amp sees half the resistance than when its not bridged. So, if you have a speaker that's rated at 8 ohms, the amp now sees it as 4 ohms. Of all the different segments that make up the audio industry, car audio is the only one that actually tries to make low impedance loads. Bridging beats the crap out of your amp and speakers, even if the amp is rated for it. Touching your speakers together is a 0 ohm load, commonly referred to as a dead short. So, if you give your amp a 1 or 2 ohm load, you're only 1 or 2 ohms away from a dead short. Bridging isn't always the wrong choice, but most of the time it is. The harder you push an amp, the worse it sounds. I would recommend that you try your amps un-bridged as well, and pick the one that sounds the best. An amp working too hard can easily sound like a phase or time issue. Don't worry about watts. You're going for quality, not quantity. And the way manufacturers rate their amps for power is nothing short of criminal. If you have an amp rated for 1000 watts, you're never going to get anywhere near that in the real world. They inflate their power ratings by measuring the amp on a test bench, running a test tone through it. Music is far more demanding than a test tone.
Any updated tutorial for this bud??
You got Focusrite audio interface but please tell me exactly which one because on the market I found a lot of versions. Thanks a lot
All of them will perform the same for this purpose.
hey , i have finished corrected my speakers but i have some cancelation in certain areas when left and right spekaers playing together , and unwanted boosts in other areas . how can i fix it so they will sum up nicely ?
Looks like your speakers are not time aligned.
when i use holmimpulse option window the offset noumber find something 5600 etc that case i am changing this number and press use butten then it not change its come back automaticaly what can i do
Don't press "use". Just enter the number and measure again.
Can I use my umik 1 in sound card via type c to xlr cable ?
No, unfortunately not. You need and XLR mic with a 2ch audio interface.
@@RAW-CAt ok thanks 🙏
Can you try a generic DSP which might not have a allpass filter and phase delay option.
Not sure what you mean by that. Try what? I just showed in the video what is happening without the phase adjustment.
I mean many DSP doesn’t come with phase slider like helix does, how can we align the phase.
@@feins you can't that's the point. If you could, I wouldn't use the phase slider in the first place.
Noted.
I've been looking at other DSPs from miniDSP and Sony, but for this reason alone, I'm leaning towards the Helix. The Sony only has time alignment via distance measurement and no phase control, and there's little to no documentation for the miniDSP. Which model do you have?
I have a Helix DSP Pro MK3. It's the newer ACO platform.
@@RAW-CAt Thank you! How many parametric EQ bands do you have per channel? I think I saw 30 in your software, but I wanted to check since I can't find a clear answer online.
@@TheMstwntdLMSV123yes, it has 30 per channel and another 30 per virtual channel. So much more than you will ever use😂
What's the software? What's the DSP?
Holm impulse and Helix.
I have also a Front Sub (10inch) and Rear Sub (12inch). I do not High pass the Frontsub, because it is not needed. Maybe one reason why i dot not face the same problem as you.
How low does your front sub play. Mine plays all the way down that I don't really need.
So the slope on your subwoofer response will rotate phase as it is effectively a very low crossover point, unless you have a flat response and then apply a crossover you won’t get a stereo typical phase response, in your case the front sub has a slant and also a crossover applied, and your subwoofer has a slanted response and a crossover applied, neither will ever give a textbook response or need timing as you have done with impulse response
Impulse just shows you the earliest arrival. It doesn’t show the frequency of that arrival… it is definitely not at the crossover point for your subwoofer or front sub… so effectively you are worrying about a time that is irrelevant, so the drivers aren’t in time. The wavelengths are so long that you should only really concern yourself with getting the best overlap and phase coherance, mids to midbass, they will be closer in that respect, but even then time of first arrival may not be perfect but sound coherant 👍🏼
So timing is important the shorter the wavelength is. Between midbase and sub frequency’s wavelength are so long that only phase plays a role. If I have 2 midbass drivers upfront and one sub in the back I basically time align the midbass to the higher frequency drivers but the sub gets no time alignment at all ? To get phase correct between sub and midbass it is important that the acoustical frequency response between both sub and midbase have the same slope. If both don’t have the same slope they are out of phase and therefore small phaseadjustemnts need to be done via the phaseknob in the dsp or the sub itself. You know that sub and midbase is in phase if you get the acoustical response of your individual drivers combined to your sumed response slopes you have imported from jazzy into REW. If they are out of phase there is a deep dip in the crossover point. If they are not totally in phase there is no dip but not really a ad up from the crossover point and one octave above and below. If they are totally in phase they ad up completely in the crossover point and one octave below and above. Is this correct ?
Correct me if I'm wrong but, crossover interact from one octave between your crossover point for 24db/Oct.
If your crossover was set for 50hz. You would see sub interaction all the way from 25hz to 100hz. Which would explain why you were having phase issues with your rear sub, as they taper off and don't play at the needed frequency causing the phase change.