Understanding subwoofers

[Keith_W]

Is this the kind of thing you're looking for?

Dutch & Dutch 8C Quasi-Anechoic Spinorama and Measurements

If the predicted in room response was the same between 2 different speakers, but they got there in different ways, would they sound the same size? They would likely not, especially not from the same space. Even speakers with the same DI/ERDI curves would sound different. Remember that for the...

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No, I specifically said in-room. I wanted to see if the cardioid pattern really does reduce irregularities in the transition zone. It looks like it does, thanks to our friend Thorbjorn.

 

[janbth]

I think beyond co-location vs time alignment, crossover point is a key variable. With higher crossovers where localization cues are stronger, placing subs near the mains helps anchor bass to the image. With lower crossovers, localization drops off and placement can be optimized more for room behavior and modal control.

I disagree with this. Much of the localization cues comes from harmonic overtones, which are typically above the crossover. If you cut the overtones from, let's say, a hard panned bass guitar, it would be much more difficult to localize - if at all possible.

 

[Satanica]

No, I specifically said in-room. I wanted to see if the cardioid pattern really does reduce irregularities in the transition zone. It looks like it does, thanks to our friend Thorbjorn.

Unless I'm mistaken they are in room measurements.

 

[sigbergaudio]

I disagree with this. Much of the localization cues comes from harmonic overtones, which are typically above the crossover. If you cut the overtones from, let's say, a hard panned bass guitar, it would be much more difficult to localize - if at all possible.

I'm not sure if I misunderstand you or the poster you quoted, but I'm not sure I see where the disagreement is?

 

[janbth]

I'm not sure if I misunderstand you or the poster you quoted, but I'm not sure I see where the disagreement is?

Maybe I wasn't clear. My point is that it doesn't matter much where the subs are placed. The bass doesn't need "anchoring" from co-location with the mains.

 

[sigbergaudio]

Maybe I wasn't clear. My point is that it doesn't matter much where the subs are placed. The bass doesn't need "anchoring" from co-location with the mains.

Right, but it feels like you agree that this was due to the overtones being above the crossover. But what he was saying is that you may need such an anchoring with higher crossover frequencies (potentially bringing the overtones below the crossover point(?)). To what extent that is correct depends on what he means by high crossovers I guess.

Personally I find even at 80-100hz it's fine to move the subwoofers away from the speakers. But if we're talking like 200hz I may be inclined to put them pretty close.

 

[thcdru2k]

I was not speaking about my own system or personal belief or preference, just looking at the systems in the thread. The main system here that is co-locating is levimax and he is running a crossover of 180 Hz

 

[levimax]

I don't think there is much point (!) of having point source behaviour below the Shroeder frequency. It's much more important to sort out the effects from room modes. Imaging and sound stage is generated by the frequencies higher up the range. I have sorted out room modes by multisub techniques - i.e. not co-located subs - and the sound stage improved noticeably. Also, the slam and punch from kick drums was much improved. I think this is a common experience.

My research and experience regarding "slam" are quite different. The research I have seen would indicate that distributed subs vs colocated subs is mostly a trade off of time domain accuracy (slam) vs frequency response smoothness. The advantages of the wave front from a point source in the time domain is settled science as far as know. Since the room is public enemy number one room treatments and or DBA or similar is going to yield the biggest improvement. Below is a summary of what research I have done on "slam". Of course my AI friend tends to go with what it thinks I want to hear so I would welcome comments of where this analysis in incorrect or oversimplification:

Edit: I am having formatting issues, looks like forum now down samples everything sorry for blurry image.

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[thcdru2k]

Keep in mind from the picture of his massive subs and monitor it looks like a single seat system so he may be less concerned with room issues. I think below 100hz room certainly dominates. I currently am experimenting with a lower crossover around 60 Hz with a stereo-bass approach using asymmetrical routing, slight delay offsets between subs, and one sub inverted to introduce controlled decorrelation

 

[janbth]

Right, but it feels like you agree that this was due to the overtones being above the crossover. But what he was saying is that you may need such an anchoring with higher crossover frequencies (potentially bringing the overtones below the crossover point(?)). To what extent that is correct depends on what he means by high crossovers I guess.

Personally I find even at 80-100hz it's fine to move the subwoofers away from the speakers. But if we're talking like 200hz I may be inclined to put them pretty close.

I'm not sure why we would need anchoring even at higher crossover points, but of course I agree that there is an upper limit on the crossover to where localization effects occur. These are setup dependent. Some people may need to go low, but others - like myself - will get away with 120 Hz. I now run Dirac ART, which is not traditional bass management, but my subs contribute up to 150 Hz. And as I previously mentioned, one of these is not co-located. I can imagine cases where up to 200 Hz would work, but I admit that would be rather unusual.

 

[janbth]

My research and experience regarding "slam" are quite different. The research I have seen would indicate that distributed subs vs colocated subs is mostly a trade off of time domain accuracy (slam) vs frequency response smoothness. The advantages of the wave front from a point source in the time domain is settled science as far as know. Since the room is public enemy number one room treatments and or DBA or similar is going to yield the biggest improvement. Below is a summary of what research I have done on "slam". Of course my AI friend tends to go with what it thinks I want to hear so I would welcome comments of where this analysis in incorrect or oversimplification:

It's fine that you can get better slam with your setup by using co-location of the subs as an ingredient, but I don't see how this is true in general. I can only repeat that I do get slam from my subs - of which one is non co-located - as evidenced by measurements and listening to test tones (bursts) and music.

 

[sigbergaudio]

My research and experience regarding "slam" are quite different. The research I have seen would indicate that distributed subs vs colocated subs is mostly a trade off of time domain accuracy (slam) vs frequency response smoothness. The advantages of the wave front from a point source in the time domain is settled science as far as know. Since the room is public enemy number one room treatments and or DBA or similar is going to yield the biggest improvement. Below is a summary of what research I have done on "slam". Of course my AI friend tends to go with what it thinks I want to hear so I would welcome comments of where this analysis in incorrect or oversimplification:

Edit: I am having formatting issues, looks like forum now down samples everything sorry for blurry image.

Linear phase and time coherence is audibly positive. But say you co-locate the subs to achieve a point source, but as a consequence end up with a 6dB dip at 60hz, I suspect the perception of slam would be quite a bit better by having the subs somewhere else where that dip is not present. So it's not exactly clear cut.

 

[Keith_W]

Below is a summary of what research I have done on "slam".

Who wrote that? You?

I would be very curious to read the original articles you cited in your references if you have them. Would you be able to PM them to me by any chance?

 

[levimax]

But say you co-locate the subs to achieve a point source, but as a consequence end up with a 6dB dip at 60hz

What causes a 60 Hz dip? If this is correct then all full range speakers also have a 60 Hz dip?

 

[levimax]

My ub

It's fine that you can get better slam with your setup by using co-location of the subs as an ingredient, but I don't see how this is true in general. I can only repeat that I do get slam from my subs - of which one is non co-located - as evidenced by measurements and listening to test tones (bursts) and music.

My understanding is that a point source creates a single wave front that as it travels through air is inherently better in the time domain that seperated lobes like multiway speakers or separated subs. This is why coaxial drivers are so popular. All this stuff.is very subtle and trying to ABX colocated vs distributed for slam is more or less impossible. I can quick switch from IIR to Linear phase but it has a massive tell when going from IIR to linear phase so can't ABX blind but the switch is quick and they sound noticably different to me.

 

[sigbergaudio]

What causes a 60 Hz dip? If this is correct then all full range speakers also have a 60 Hz dip?

A full range speaker in the same position would also have the dip, yes.

 

[thcdru2k]

Co-locating means all the drivers hit the room the same way, so any dip the room creates gets reinforced instead of averaged out. I think that is one negative.

 

[levimax]

Who wrote that? You?

I would be very curious to read the original articles you cited in your references if you have them. Would you be able to PM them to me by any chance?

My AI friend wrote it and I gave full credit which is why I asked for comments. I also had AI do some simulations comparing ideal time domain behavior vs various crossovers and colocated vs distributed sub solving for dp/dt plotted against frequency and the results were consistent with what I posted. I have at least one of the studies but not all, I will look and send over later if I.find anything.

 

[levimax]

A full range speaker in the same position would also have the dip, yes.

Is that compensated for in recordings or are we all listening to a 60 Hz dip when we listen to stereo?

 

[thcdru2k]

I think he means 60hz as an example not a rule. A null depending on room geometry and placement.