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The importance of time alignment for subwoofers

Thomas savage

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#1
hi,

Some of you might know I bought a room correction box anyway it’s ended up sat before two subwoofers rather than within my whole system ..

So it smooths frequency response at the listening position but that seems only part of the issue, while buggering about with placement of the subs it seems best ( contrary to some advice , namely of REL) to keep them in line with my mains..

I’m guessing this is to do with time alignment? It completely ruins the music when they are in the corners of my room behind the speakers but then in line all is well.

So why the obsession with room modes/ momentary dips and peaks etc when there seems a lot less fuss about time alignment which to me seems as important if not more so..

A visual reference as to where they are now.., they were back in that corner
317FBE76-DE2D-4751-B3AC-BCC5F89231B5.jpeg
 
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Thomas savage

Thomas savage

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Thread Starter #2
I’m running a stereo pair, placed in the present location they are set to maximum frequency range so 120hz and I can’t detect any negative from running that way.

Placed in the corners my sound stage is poorly defined no matter where i set the sub frequency range so 80hz or less still causes things to sound ‘wrong’ .

I was expecting some localisation issue running them at 120hz obviously but that never happened explicitly just ‘ smearing’ of the soundstage.

This was all a surprise to me, I know I should really have a dac with individual channels all being time aligned in software but I don’t and likely never will, more importantly most audiophiles don’t .

I often read people trying subs and leaving the idea in the rear view, maybe that’s because of time alignment rather than frequency response ? I also see plenty of pictures of audiophiles rooms with subs set well behind the main speakers..., what the hell are they listening too? Even if they have room correction on the sub it’s not time aligned with the mains ? It very possible I’m just nuts and imagining all this of course but what’s the technical dare I say scientific reasoning behind my subjective findings?
 

oivavoi

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#3
There is some research which claims that bass feels more natural when it's coming from the same direction as the mains. Can't be bothered to look it up now, perhaps later. This research is far from being canonical, though, as the established theories say that bass is omnidirectional below certain frequencies and can't be localised.

It might be that you'd perceive it as more natural if you had subs both at the front and the back. But my experience aligns with yours and goes in the direction of the non-canonical paradigm: Subs feel more natural to me when placed behind or to the side of the speakers, and it feels strange when I place them behind the sweet spot, unless crossed over really really low (like 50 hz for example) with a steep crossover.

Have only tried with two subs though, still havn't tried four, or equalizing them with advanced software for bass management. There are reports from people who use Multi-sub optimizer, for example, that it felt unnatural to them to spread subs around manually, but that it became smooth when using MSO.
 
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Thomas savage

Thomas savage

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Thread Starter #4
My reasoning for trying subs was really more motivated by going to live gigs and noticing more low content or more specifically more amplitude and greater extension. I’d go back home and have to adjust back to a more ‘empty ‘ sound ( note I get that ‘empty ‘ feel vs live music from all the systems Iv listened too so it’s not a failing of my setup particularly)

Even when listening at relatively low volume ( 85db peaks c weighted) the subs fill the sound out bringing quite unexpected benefits (it all just sounds more natural lol ) but they have to be in line with the mains it seems unless your using a complete system base management system that can treat every channel individually..
 

Purité Audio

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#5
Download REW and measure, move the subs measure again, a $100 MiniDSP processor will enable you to properly integrate your subs and then correct any room modes created by the extra bass extension.
Keith
 

Blumlein 88

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#6
I concur on the REW.

I also think 120 hz might be a bit too high.

Now it looks to me like your main speaker is too close to the rear wall, but that might be the right spot for other reasons.

Otherwise I blame it on the cable lifters. :eek:
 
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Thomas savage

Thomas savage

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Thread Starter #7
There’s no problem with the frequency response, I had a room correction box that uses a microphone.. Iv done all that. Mini dsp and rew is of no intrest to me at this time. If there’s no audible issue I’m ok with it, if I have audible issues then yes I’d be more inclined to start buying more crap and moving things about .

The issue was how important it is to have a sub in line with your main speaker and yes 120hz is too high but no it’s not if it’s setup ok. I’m not crossing over from my main speakers, the mains run separate full range no room correction.

There’s no issue with running my speakers that close to the back wall, when I used my room correction device on my main system the ‘ before’ graph ( minus subs as I was not using them) has no terrible peaks in the MLP.

I’m left with no problems at all, just I found it intresting that time alignment was often left out of the conversation when folk are setting up their subs.

Really I was not looking for advice, I just was highlighting the lack of importance time alignment seems to gather when you start talking to people about subwoofers with even some of the company’s who are making them giving bad advice when it comes to the issue .
 
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Thomas savage

Thomas savage

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Thread Starter #8
I concur on the REW.

I also think 120 hz might be a bit too high.

Now it looks to me like your main speaker is too close to the rear wall, but that might be the right spot for other reasons.

Otherwise I blame it on the cable lifters. :eek:
I can get the hoover under with the cable lifters there :D

So what about time alignment when setting up subs lol
 

Purité Audio

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#9
If you aren’t interested in integrating the subs properly , high/low pass, order freq etc and if you aren’t interested in the frequency response what are you interested in?
Just plonk them anywhere.
Keith
 
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Thomas savage

Thomas savage

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Thread Starter #10
If you aren’t interested in integrating the subs properly , high/low pass, order freq etc and if you aren’t interested in the frequency response what are you interested in?
Just plonk them anywhere.
Keith
Ok Keith, the mini dsp 2-4 box is great but Iv tried similar in my system and don’t like it. I’m using room correction on my subs only and this is how things will stay. The mini dsp dose not do BM or impulse response only offering room EQ wizard and more over it won’t fit into my current set up, I could get the new HD version and scrap my pre amp , take a digital output from my CDP/DAC but it would sound shite. I did not want to go into all that, that’s why I said it’s not for me AT THIS TIME.

This thread as the title suggest was never about me, as has been mentioned now several times. It was about the lack of importance given to time alignment of sub woofers. I merely showed how I found this out using me as a example.

I was hoping for a general discussion regarding the above and why it’s import, maybe how people can achieve it with and without BM software but mainly a explanation of what’s going on and why it matters. Not for my benefit as it was NEVER ABOUT ME, but to generally raise awareness of the issue.

If I wanted advice I’d of put ..,

Help, can’t set my subs up.

Feel free to offer your knowledge on time alignment of subwoofers and exactly what’s going on and why it’s important ( if indeed you think it is, some might not.. the basis of a discussion).
 
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Thomas savage

Thomas savage

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Thread Starter #12
I understand I tried to help, but you know best.
Keith
Christ, it’s not about “knowing best” , the thread WAS NOT ABOUT ME MY SET UP MY REQUIRMENTS WHAT I NEED .

If you want to help me you can add your understanding about time / phase alignment within a sub setup, how and why it’s important maybe a little about why it often gets ignored over focusing exclusivity on frequency response.

Maybe there’s a formula for measuring the distance from a speaker to the sub and inputting that in A delay function of a dsp box manually.. so if your sub is a meter from your speaker how many millisecond of delay do you need etc.. some theory then some technical insight but NOT FOR ME just as a function of discussion and to raise awareness in the wider Audio community.

Thanks for your excellent advice of “Buy a mini dsp box and get rew” but That’s not what the threads about keith and it does not fit in my system anyway, using REW is a excellent suggestion as practical way to achieve phase alignment etc I can’t do that right now though but again it’s not about me.
 
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#14
So it smooths frequency response at the listening position but that seems only part of the issue, while buggering about with placement of the subs it seems best ( contrary to some advice , namely of REL) to keep them in line with my mains..
That’s probably because most subs lack built-in DSP for time alignment. IMO if the choice is “either-or,” good frequency response trumps time alignment every time. It’s been a long-accepted fact that one of the benefits of subs was that they overcame a common room problem, that the best speaker location for imagine was seldom the best location for bass response.

So why the obsession with room modes/ momentary dips and peaks etc when there seems a lot less fuss about time alignment which to me seems as important if not more so..
Improper time alignment can cause dips and peaks in response.

I also see plenty of pictures of audiophiles rooms with subs set well behind the main speakers..., what the hell are they listening too? Even if they have room correction on the sub it’s not time aligned with the mains ?
It certainly can be – just delay the main speakers.

But as you say, many audiophiles are averse to that kind of processing. In that case, there are a couple other possibilities. For one, if the crossover frequency is low enough, the omnidirectionality of the signal could be swamping any time alignment issues. Or, perhaps it just doesn’t sound all that great. You can’t tell that from a picture.

This thread as the title suggest was never about me, as has been mentioned now several times. It was about the lack of importance given to time alignment of sub woofers.
I find this a curious statement. As far as I know, time alignment for subs has always been considered important, at least since the means to correct it has been available (it wasn’t always). How old are these sources you’re talking about? Again, info from subwoofer manufactures can be discounted as they can’t all deal with time alignment.

It very possible I’m just nuts and imagining all this of course but what’s the technical dare I say scientific reasoning behind my subjective findings?
Frequency response graphs could possibly explain it, or at least help.

There’s no problem with the frequency response, I had a room correction box that uses a microphone.
Room correction can’t compensate for poor sub placement. For instance if poor placement causes nulls, no room-correction device can correct that. That’s why measurements are important.

The issue was how important it is to have a sub in line with your main speaker and yes 120hz is too high but no it’s not if it’s setup ok. I’m not crossing over from my main speakers, the mains run separate full range no room correction.
The fact you’re running your mains full range, and that you have the subs operating up so high, could indeed explain why things sound bad if everything isn’t time aligned. With both subs and mains generating below 120Hz, with the subs back in the corner you’d certainly be getting some comb filtering due to improper time alignment.

Regards,
Wayne A. Pflughaupt
 

watchnerd

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#16
Feel free to offer your knowledge on time alignment of subwoofers and exactly what’s going on and why it’s important ( if indeed you think it is, some might not.. the basis of a discussion).
The latest Dyanaudio subs have time alignment features, so I assume there is acknowledgment, at least by some, that it matters.
 
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Thomas savage

Thomas savage

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Thread Starter #17
Thanks, I was not running the subs at 120hz in the corners well I did and then adjusted it down , Iv ran my subs with a automated room correction box around the position they are in the picture and been happy with it.

I moved them into the corners ( because I’m off work and bored) and things became worse despite messing with cross over phase etc

I then came across the issue of time alignment and how having your subs inline with your speakers can help...

I thought I’d make a thread about time alignment, see if there was some insight into the subject in general , there’s people here who understand how all this works The physics of it etc

I posted the picture just as a visual reference not as a ‘ how do I fix this’ so just for context so folk could see the “ corner” I was talking about.

@oivavoi seemed to understand and answered in keeping with what I was after, then it’s all gone wrong lol

It’s ok if no one wants to talk about the subject contained within the thread title I guess.
 
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Thomas savage

Thomas savage

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Thread Starter #18
The latest Dyanaudio subs have time alignment features, so I assume there is acknowledgment, at least by some, that it matters.
Yes the sub 6 allows you to input a measurement of distance between the mains and the sub.. so many ( like my REL’s) seem to ignore it. Well they give you a polarity knob, Iv got 0 degrees and 180 .
 

sergeauckland

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#19
When I had Meridian DSP5000s and a pair of D1500 subs, I used them as Tom does, next to my main speakers, effectively creating a larger loudspeaker. However, the D1500 subs didn't have and provision for delay, just crossover frequency, level and polarity. I even thought of standing the DSP5000s on the subs, to get better horizontal alignment, but that raised the tweeters too high.

What I don't understand is why should having subs next to the main loudspeakers be any different from just having larger loudspeakers, i.e. why should the subs be sited elsewhere?
I appreciate that introducing delays to the mains might then correct the path-length difference, but that then introduces latency which may or may not matter, depending on whether there's any video sync involved, but also whatever path-length difference is set, that's only good for the one listener at the central position. Room correction similarly can't correct for every point in the room. It can either do it right for one listener, so-so for several listeners or possibly make it rather worse for some room locations.

S.
 
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