Understanding subwoofers

[ppierre]

I believe it is settled science that a wave front from a point source has higher impact than a wave front from distributed sources. I also know the room messes up point source wave fronts but it also messes up distributed source wave fronts so it still makes sense that a point source wave front will have diminished but still greater impact than a distributed source wave front at the LP.

Maybe you can revise your point of view on "distributed source wave fronts". If the delay of each source is settled right. It shouldn't be less impactful than colocated sources.

A other point of view is to see distributed sources as a virtual source of bigger size. Making irrelevant the standing waves shorters than the size of the virtual source.

 

[3ll3d00d]

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

It seems to refute it's own conclusion by saying the room dominates below 100Hz and not answering how to solve that (which is typically where multiple distributed subs come in) so seems like you're back to square one.

Just to throw another angle into the mix I remember long threads back in the day on optimising for particle velocity for mid bass slam which led to a lot of people experimenting with near field ported mid bass modules and some discussion around how to try to measure this. I think https://www.kvalsvoll.com/blog/foru...ties-relevant-for-low-frequency-reproduction/ goes into some detail (he used to post here at one point)

 

[Mort]

but I have only noticed it in two circumstances:

Maybe you are just accustomed to the null? I also have one sub. I don't notice what was never there...

 

[thcdru2k]

From experimenting with both approaches, I think “slam” and “overall integration” are related but not identical goals.

An older 4-sub system I had including an HSU MBM-12 at chest height definitely hit harder in the 50-100 Hz region and felt more visceral. My current dual-sub system sounds smoother, more immersive, and less localized, but less physically aggressive in that specific way.

Just my subjective experience. I still kind of miss the old system sometimes, but my wife definitely does not miss having four different subwoofers stacked around the living room.

 

[Vladimir Filevski]

They were just stupid enough to bolt the mains to the subs.

Or, just smart enough. Otherwise, they could not charge $778k for that.

 

[levimax]

Maybe you can revise your point of view on "distributed source wave fronts". If the delay of each source is settled right. It shouldn't be less impactful than colocated sources.

I can't be 100% sure as I had AI do the programming but I did some modeling and point source subs had ~ 40% higher "impact" i.e. dp/dt compared to distributed subs. Just a small change in timing makes a huge difference in impact. It isn't just arrival times it is also the shape of the wave front that has an effect as dp is "pressure change". Just like a coaxial mid and tweeter have a better wave front than a time aligned but separate mid and tweeter that have separate lobes. Another example is when setting up a DBA or similar, the hard part is to achieve an effective wavefront for cancelation by careful multi-sub sub placement otherwise it doesn't work very well. All this theoretical stuff only applies, if at all, to sharp transients and trying to ABX collocated vs distributed subs is extremely difficult. I do have quick switching ability between Linear Phase and IIR crossover and that is a noticeable difference to me. Since IIR vs Linear phase create a similar change in time domain behavior as distributed vs point source subs and I am currently trying to maximise slam I think it is a reasonable choice. There is no right and wrong here and the room makes a mess of all of it but if I do have a point to make it is that people are very quick to dismiss full range/ point source speakers and embrace distributed subs as the only scientifically valid option which to me is an oversimplification. Ideally I would like to have it all i.e. smooth FR and perfect time domain behavior so while waiting for ART for PC's to try I am also playing around with DBA but my room is making it hard and I don't really have enough subwoofers.

 

[ppierre]

I understand, but I speak up for distributed sources for frequency lower than 80hz. Where your "dp/dt" does not seam to me a proved effect.

"Impact" seem to me generally associated to higher up in frequency. Ence some woofer colocated with the speakers and crossed higher.

But as someone said : differents compromises.

 

[3ll3d00d]

It isn't just arrival times it is also the shape of the wave front that has an effect as dp is "pressure change". Just like a coaxial mid and tweeter have a better wave front than a time aligned but separate mid and tweeter that have separate lobes

These are physically different effect, at sub frequencies the "wavefront" is physically large enough to be a standing wave and your senses perceive it differently using different mechanisms to how 2kHz (or whatever, the specific frequency is irrelevant) propagates. But still the point remains that at low frequencies concentrating on the ear is missing a significant element of "impact" (cf. standing a bit too close to some array at a gig and have your chest pummelled or really cranking to your subs at home and having the room talk to you)

 

[audiofooled]

"Impact" seem to me generally associated to higher up in frequency.

This paper shows otherwise:

https://adamjhill.com/AJHILL/wp-content/uploads/2017/05/Hill-Hawksford-AES-130.pdf

 

[ppierre]

This paper shows otherwise:

https://adamjhill.com/AJHILL/wp-content/uploads/2017/05/Hill-Hawksford-AES-130.pdf

I was alluding to this : https://audiospectra.net/kick-drum-eq/

Rumble: 20Hz to 31Hz
Sub: 20Hz to 80Hz
Punch: 80Hz to 200Hz
Mud: 200Hz to 400Hz
Clarity: 500Hz to 1.5kHz
Presence: 2kHz to 5kHz
Hiss: 6kHz - 20kHz

And I take time to make a citation, no just a link on :

Kick-drum signal acquisition, isolation and
reinforcement optimization in live sound

Not directly related. And make me lost my time to figure what you where meaning.
Please discard what I say, my opinion is mine and this discussion is sterile.

I'm out. Sorry to make you louse your time.

 

[audiofooled]

And I take time to make a citation, no just a link on

I was hoping reading the paper would make things more clear. It actually shows measurements of frequency and transient response of a real kick drum, with regards to practical problems of sub reinforcement.

It's the atonal impact that is emphasized by improving the transient response of the kick drum in case of internal damping affecting the frequencies 40-70Hz. This normally reduces ringing. In terms of energy, it's the time domain that is important, not the upper frequency band. The impact of a real kick drum is delivered by the mode 0 of the circular membrane, which does not produce any pitch or timbre quality (this is in higher modes and frequencies that come a bit later in time).

For fidelity of the transient, including impact reproduced at home, time alignment across frequency is very important. So we look at the entire frequency band as measured in the paper.

In attachment you may find a cumulative shift depicting my system maintaining the phase integrity for hypothetical delay sequence in ms, measured at 3.5 meters.

 

[john61ct]

The concepts of "punch" and "impact" are far broader than just the response of reproducing one instrument.

Just as those frequency range labels are arbitrary, there aren't such exclusive bright dividing lines in reality.

The attempt to emphasize the DEGREE of physical / emotional "impact" may be (likely is) in direct conflict with transparent reproduction of the acoustics.

"I find that very pleasing" may in general (statistically) correlate with SQ accuracy, but wrt physical "non ear" aspects I believe those becomes a lot more variable based on music genres and tastes of the individual.

I agree with Dr Toole in striving for accuracy / fidelity as much as possible to the source performance as the fundamental baseline

with the ability to tweak for user preference or exceptional content, layered "on top"

 

[levimax]

The concepts of "punch" and "impact" are far broader than just the response of reproducing one instrument.

Just as those frequency range labels are arbitrary, there aren't such exclusive bright dividing lines in reality.

The attempt to emphasize the DEGREE of physical / emotional "impact" may be (likely is) in direct conflict with transparent reproduction of the acoustics.

"I find that very pleasing" may in general (statistically) correlate with SQ accuracy, but wrt physical "non ear" aspects I believe those becomes a lot more variable based on music genres and tastes of the individual.

I agree with Dr Toole in striving for accuracy / fidelity as much as possible to the source performance as the fundamental baseline

with the ability to tweak for user preference or exceptional content, layered "on top"

Punch and Impact also called "transient attack rate" or "bass transient reproduction" is scientifically defined as (dP/dt)max with dP= change in pressure and dt = change in time. It does not just apply to drums but that is the most obvious example. Audibility can be debated but theoretically the better the time domain behavior that higher the "transient attack rate" which most people consider a positive SQ attribute.

 

[Sokel]

Which impact are we talking about?
The chest punch for example is way higher than 80Hz reaching 250Hz.

Some nice test here:

Bass: the Physical Sensation of Sound

Ever wonder why you can feel bass? We take a look behind the science of bass waves and the tactile sensations that they cause. Our bass experiments were quite revealing but don't try them at home.

www.audioholics.com

And some of the text:

 

[thcdru2k]

Which impact are we talking about?
The chest punch for example is way higher than 80Hz reaching 250Hz.

Some nice test here:

Bass: the Physical Sensation of Sound

Ever wonder why you can feel bass? We take a look behind the science of bass waves and the tactile sensations that they cause. Our bass experiments were quite revealing but don't try them at home.

www.audioholics.com

And some of the text:

View attachment 530993

That matches what I found in my experience with this discontinued product from HSU.

 

[Sokel]

View attachment 530994
That matches what I found in my experience with this discontinued product from HSU.

Chest punch is one of the things I like sometimes, so I test everything about it.
I'm talking about the light-speed sudden hit with the sharp, immediate decay.

You know the irony?
Remember those old, broad baffle speakers with large mid-bass drivers and not much extension low?

Those were usually sensitive and they would kick like mules!

Another, pro-audio, open concert subs.
These have no output below 40Hz, and they usually do well above 60Hz or so.
Well. they can throw you of the chair.

What I have seen at today's speakers , the ones that kick are usually at the big-ish size 150 liters or so, mid-bass at least 10" with strong motors crossed at 250H -500Hz, etc.
Room helps a little as well but not much up there, as opposed to the gut-rubbling, slow subs feeling.

 

[thcdru2k]

Chest punch is one of the things I like sometimes, so I test everything about it.
I'm talking about the light-speed sudden hit with the sharp, immediate decay.

You know the irony?
Remember those old, broad baffle speakers with large mid-bass drivers and not much extension low?

Those were usually sensitive and they would kick like mules!

Another, pro-audio, open concert subs.
These have no output below 40Hz, and they usually do well above 60Hz or so.
Well. they can throw you of the chair.

What I have seen at today's speakers , the ones that kick are usually at the big-ish size 150 liters or so, mid-bass at least 10" with strong motors crossed at 250H -500Hz, etc.
Room helps a little as well but not much up there, as opposed to the gut-rubbling, slow subs feeling.

Some systems may not dig the deepest or measure the smoothest but they can still be very physical in a way that adds enjoyment. Don't mean to get too subjective but for me it creates a feeling of excitement/anticipation. It probably helps I am still fortunate to be relatively lean like what you posted suggests. It's definitely not the easiest region to tune at home since that is usually where room interaction, alignment, and cancellation issues can occur.

 

[john61ct]

I'm trying to get a DIY design together for maximum reinforcement in that mid-bass range, out of a 12x12" face, maybe 15" depth.

I want front-facing only, I guess sealed for "tight bass" fast "transient attack rate", but to boost SPL have also been looking at PR-bandpass design like @Wolfs' "Overdrive 10" project aka Kilauea (although that is a trueSub) https://www.diyaudio.com/community/threads/overdrive-10-a-pr-bandpass-sub.325828

Looking for "not trueSub" driver suggestions, 4ohm preferred

Peak SPL centered within say 60-120Hz with good extension up to 200+Hz, efficient power handling maybe 200W, but higher would be OK

a deeper F3 on the low side not required but would be nice.

There will be multiple trueSubs below that point as well, the above is just "MBM Coupler" for filling in, similar to the design purpose of the Rythmik FM8, also that HSU unit above I guess.

 

[3ll3d00d]

I want front-facing only, I guess sealed for "tight bass" fast "transient attack rate", but to boost SPL have also been looking at PR-bandpass design like @Wolfs' "Overdrive 10" project aka Kilauea (although that is a trueSub) https://www.diyaudio.com/community/threads/overdrive-10-a-pr-bandpass-sub.325828

these are contradictory statements as a 4th order bandpass means a degraded transient response (but still a response described by the given frequency response so...)

 

[WillBrink]

Agree to disagree. Nothing wrong with stacking subs under mains. You are putting your mains and listening position in the 3 best acoustically "correct" locations where room modes are minimized. It can work quite well. This is how you would place a full range speaker so no real difference.

Rob

That was the only place I could put the subs in my space, but the results have been excellent.