The importance of time alignment for subwoofers

[Purité Audio]

8260a’s and two 7270a subs here, must be ten years ago now, the first time I had really heard properly integrated subs, having said that much preferred the Grimm LS1s .

Keith

 

[svart-hvitt]

8260a’s and two 7270a subs here, must be ten years ago now, the first time I had really heard properly integrated subs, having said that much preferred the Grimm LS1s .

Keith

"...much preferred the Grimm LS1S".

I wasn't aware that Grimm had a DSP software based bass management system for a full portfolio of subwoofers?

 

[RayDunzl]

Audiolense is the first and only software product I have used that time aligns subs correctly and is repeatable, with no manual intervention. More amazing is how they possibly can be aligned when I have them crossed over so low at 40 Hz!

A 20hz wave has a cycle time (360 degrees) of 50ms...
If phase at 20hz is shifted forward in time (negative) 740 degrees, that's 103ms...

A 60 hz wave has a cycle time of 16.6ms.
If phase at 60Hz is shifted forward in time 540 degrees, that's 25ms

Here's the phase correction (left and right preamp output) using AcourateDRC here at Neverland East for the MartinLogans and Cheesewoofers.:

The subs low-pass at about 100Hz, and the mains are run full range here, the correction is the overall signal correction.

Here's what the "corrective" impulse and step and frequency responses look like (at the preamp out)



And raw (uncorrected) impulse and step at the preamp output for comparison or reference.



Uncorrected phase and frequency response are flatlines, so not shown.

 

[dallasjustice]

"...much preferred the Grimm LS1S".

I wasn't aware that Grimm had a DSP software based bass management system for a full portfolio of subwoofers?

IMO, Bruno’s view as expressed in the LS1 manual “room correction” is typical amongst speaker designers.

Some companies apply DSP for ’room correction‘. We rather not use DSP in the LS1 for this since the effects are in uenced by the position of the listener. If we again look at the three acoustic factors: 1. First re ections are strongly dependent on the listeners‘ position, so there is no way to correct these with DSP. This is certainly true above 200 Hz where the wavelength is short. 2. The low frequency coupling effect can partly be compensated by DSP (please use the LS1 EQ for that). However in the region around 100 Hz where often energy is lowered due to the re ection being out of phase, DSP will not help since a louder tone will still be canceled by its re ection. 3. Finally, room modes are also strongly dependent on the position of the listener. Theoretically it should be advantageous to attenuate peaks in the room response that reside in the whole listening area, but all DSP solutions for this we tried so far challenged the LS1's performance too much.

To me, this demonstrates a lack of experience with so called “room correction” software.

 

[svart-hvitt]

IMO, Bruno’s view as expressed in the LS1 manual “room correction” is typical amongst speaker designers.
To me, this demonstrates a lack of experience with so called “room correction” software.

It seems like Grimm is more research oriented than science oriented?

Research and science are sometimes the same; oftentimes they are not.

"Content without method leads to fantasy; method without content to empty sophistry".
Johann Wolfgang Goethe (1749-1828)

 

[Purité Audio]

Grimm aren’t as far as I am aware great fans of room correction, they prefer to eliminate off-axis response at source, a concept developed by the Kii THREE, Beolab 90 and Dutch&Dutch 8Cs, my experience mirrors that better to minimise at source rather than try to ‘correct’ after the fact.
Keith

 

[svart-hvitt]

Grimm aren’t as far as I am aware great fans of room correction, they prefer to eliminate off-axis response at source, a concept developed by the Kii THREE, Beolab 90 and Dutch&Dutch 8Cs, my experience mirrors that better to minimise at source rather than try to ‘correct’ after the fact.
Keith

Other producers have two thoughts at once. Doing one thing doesn’t rule out another. It depends on competence including resources.

To me, it seems like less resourceful producers use tactical arguments to favour their narrower position.

 

[Purité Audio]

I thought Genelecs ‘active’ series were an advance ,that’s why I bought some , the 8Cs are a further advance and I dare say in the future innovative technology will produce an even better loudspeaker.
The ‘cardioid’ speakers here produce clearer more transparent sound quality than any other ‘traditional’ loudspeaker I have tried despite the addition of passive/active room correction EQ etc etc.
Keith

 

[Cosmik]

Other producers have two thoughts at once. Doing one thing doesn’t rule out another. It depends on competence including resources.

To me, it seems like less resourceful producers use tactical arguments to favour their narrower position.

I see it as just the opposite: anybody can fiddle about with 'room correction' and obtain a ruler-flat response - or whatever target they arbitrarily decide on.

Not everyone can see that a room is a complete, consistent system where every wobble in frequency response is 'explained' by precisely complementary delays, resonances, absorption of different frequencies and so on. These remain precisely consistent in three dimensions as the listener moves their head. The room can never be 'wrong' so cannot be 'corrected' by changing the source - which just sounds like a weird source in the same room.

"Aha, but it's different for the bass" you may say, but even there, what you are hearing is precisely consistent with the room's effects on the other frequencies. If you fiddle with the bass on its own, it will sound inconsistent with everything else. You can't 'fix' a poor listening room by changing the source. Just get a bigger room or effectively create a new one by moving stuff around; fitting a carpet; changing the speakers' height, etc. Most likely you are simply not in a music mood that day. After that you are probably craving a change of room rather than suffering from an 'incorrect' one.

 

[svart-hvitt]

I thought Genelecs ‘active’ series were an advance ,that’s why I bought some , the 8Cs are a further advance and I dare say in the future innovative technology will produce an even better loudspeaker.
The ‘cardioid’ speakers here produce clearer more transparent sound quality than any other ‘traditional’ loudspeaker I have tried despite the addition of passive/active room correction EQ etc etc.
Keith

Geithain have produced cardioid speakers for ages. Plus, they are coaxial and truer single-point.

In other words; nothing new under the sun.

Having said that, I like the idea of both cardioid and single-point. What I don’t like is selling something as new when the concepts have been implemented and tested for a long time. I try and avoid being fooled by «same shit new wrapping».

 

[svart-hvitt]

I see it as just the opposite: anybody can fiddle about with 'room correction' and obtain a ruler-flat response - or whatever target they arbitrarily decide on.

Not everyone can see that a room is a complete, consistent system where every wobble in frequency response is 'explained' by precisely complementary delays, resonances, absorption of different frequencies and so on. These remain precisely consistent in three dimensions as the listener moves their head. The room can never be 'wrong' so cannot be 'corrected' by changing the source - which just sounds like a weird source in the same room.

"Aha, but it's different for the bass" you may say, but even there, what you are hearing is precisely consistent with the room's effects on the other frequencies. If you fiddle with the bass on its own, it will sound inconsistent with everything else. You can't 'fix' a poor listening room by changing the source. Just get a bigger room or effectively create a new one by moving stuff around; fitting a carpet; changing the speakers' height, etc. Most likely you are simply not in a music mood that day. After that you are probably craving a change of room rather than suffering from an 'incorrect' one.

Don’t create a straw man. Nobody claims the room is unimportant.

DSP lets you listen to the room correction filter by button click so you can decide for yourself if it meets one’s preferences.

No big deal really; the proof is in the pudding.

If your position is that room correction is harmful, please provide some material support for that position.

 

[Purité Audio]

Geithain have produced cardioid speakers for ages. Plus, they are coaxial and truer single-point.

In other words; nothing new under the sun.

Having said that, I like the idea of both cardioid and single-point. What I don’t like is selling something as new when the concepts have been implemented and tested for a long time. I try and avoid being fooled by «same shit new wrapping».

Geithain’s cardioid response is bass only and their coaxial consists of placing a tweeter in front of the mid, they are also not full range until you get to the 901s so not really the same , but I am going to get some Geithains to compare.
I don’t believe EQ is harmful, sometimes it is the only solution, but I believe it is better not to create the issues in the first instance.
The benefits are completely obvious when you compare in your own room.
Keith

 

[Cosmik]

Don’t create a straw man. Nobody claims the room is unimportant.

Erm. I can only see one straw man there!

If the room was unimportant then we would listen in anechoic chambers - which would give the 'best' measurements. We choose not to do that because it sounds rubbish, and is an unpleasant environment.

DSP lets you listen to the room correction filter by button click so you can decide for yourself if it meets one’s preferences.

Just as randomly playing with a graphic equaliser does. You may even like the novelty as you switch it in and out, and gasp at the extra detail you can hear on the violins or whatever. But it won't last.

 

[svart-hvitt]

Geithain’s cardioid response is bass only and their coaxial consists of placing a tweeter in front of the mid, they are also not full range until you get to the 901s so not really the same , but I am going to get some Geithains to compare.
I don’t believe EQ is harmful, sometimes it is the only solution, but I believe it is better not to create the issues in the first instance.
The benefits are completely obvious when you compare in your own room.
Keith

I have compared (K3 vs 8351 in room). No big deal. Both are great. The 8351 sounds bigger and has better bass.

 

[svart-hvitt]

Erm. I can only see one straw man there!

If the room was unimportant then we would listen in anechoic chambers - which would give the 'best' measurements. We choose not to do that because it sounds rubbish, and is an unpleasant environment.

Just as randomly playing with a graphic equaliser does. You may even like the novelty as you switch it in and out, and gasp at the extra detail you can hear on the violins or whatever. But it won't last.

I see your argument. But I can’t see your providing material support for your position that room correction is harmful in Hippocrates sense.

 

[Purité Audio]

I have compared (K3 vs 8351 in room). No big deal. Both are great. The 8351 sounds bigger and has better bass.

Me too, I thought the Gens were good for close up a metre or so, but after that bass just became diffuse, the Kiis have a fairy narrow ‘band’ of soundstage, yesterday we compared the Kiis and 8Cs at a guys studio ( the chap posted his thoughts on the Gearslutz 8C thread) the 8Cs have a much larger in terms of depth and height soundstage.
I suppose ultimately it is your preference.
Keith

 

[dallasjustice]

The benefits are completely obvious when you compare in your own room.

The benefits don’t look very obvious from your own measurements. From your blog, your room has a gigantic mode at 40hz with the kiiaudio speakers. It also shows the mode with ATC speakers. In fact, it appears the 40hz mode is much worse with kiiaudio speakers.

Maybe kiiaudio can control off axis above 100hz. But it appears ineffective at controlling room modes below 100hz.

This thread is about how subs can improve fidelity. One of the important things subs can do that no 2CH system can NOT do is control room modes.

 

[Purité Audio]

The controlled directivity of the Kiis is from around 80Hz- 2kHz but yes they don’t help with low bass room modes , the 8Cs are effective to round 60Hz I believe and they include built in EQ which is useful in my larger room.
I am quite keen to try a sub /sub with the 8Cs ( they include software integration and physical connection ) not to extend bass, they don’t need it but to actively destroy that mode.
Perhaps in the New Year.
Keith

 

[Cosmik]

I see your argument. But I can’t see your providing material support for your position that room correction is harmful in Hippocrates sense.

It's just by the power of thought experiment alone.

If I got a singer to perform in an anechoic chamber and analysed their FFTs at my listening position, and then got them to repeat the performance in my listening room, would they sound better
(a) Unmolested?
(b) Their voice supplemented with one of those headset mics, real time DSP box, and a speaker, allowing us to perfectly match the FFTs with those recorded in the anechoic chamber, at the listening position?

In the world of 'room correction', the difference in FFTs (measured using consistent parameters between the two situations) is considered an 'error', and 'correction' is used to make the FFTs match. This would be the (b) option.

If you think (a) might be the better answer, then you are saying that on this occasion, at least, you think that 'room correction' would be a mistake and that letting the room do what it's going to do would give the better result.

 

[Fitzcaraldo215]

Not sure where this experiment might lead. Both a and b have their problems so possibly neither would sound good, and the choice might be moot.

I do not think DSP room correction is a perfect or precise solution to the messy and very complex problem of room acoustics. Nothing is. All I know is that it is a sonic revelation offering much preferred performance with recordings I enjoy. I would never be without it. And, it is cheap relative to what it achieves, in my view.

Yes, we may adapt to the sound we have in our rooms if we choose to. But, there are limits to that, which you don't seem to wish to acknowledge. I would rather adapt to sound that measurably corrects for some, if not all, of the problems in the room than a system which does not. The good may be good enough, even if imperfect. Room correction might even do some harm, but never have I heard it do so with proper calibration compared to no correction. The latter does more obvious harm in my experience.