"Room compensation for loudspeaker reproduction using a supporting source"

[Bjorn]

While it works to add spaciousness, it also adds comb filtering plus lobing between sources. Clearly less audible though due to the lower level.

But the accurate way is using phase grating diffusers.

 

[Duke]

While it works to add spaciousness, it also adds comb filtering plus lobing between sources.

No moreso than if those reflections had been natural ones rather than being added after a time delay by the supporting speakers. To put it another way, there is enough delay between the direct sound and the arrival of this additional reflection energy that I don't think comb filtering and lobing would be of audible significance under normal conditions.

Clearly less audible though due to the lower level.

Yes, getting the level adjusted correctly during initial set-up is important. Ime it's not difficult to do by ear.

But the accurate way is using phase grating diffusers.

It's not necessarily either/or. One could do both.

Supporting speakers as described in this thread offer a means adding and manipulating the level, frequency response, arrival time, and/or arrival direction of a substantial amount of late-onset reflection energy. And being able to do this can be beneficial.

I don't know how much phase grating diffusers alter the frequency response, but if it's audibly significant, supporting speakers aimed into phase grating diffusors could be equalized accordingly. Whether or not such EQ is useful, I think that using both supporting speakers and phase grating together might work really well.

 

[levimax]

Since you quoted me in the post where you asked that question, presumably I'm one of the people you were asking.

I don't use omnidirectionals for my supporting speakers. I use horns because I think their directivity control is beneficial, and because they cover the portion of the spectrum that I want to focus on.

What are your main speakers, if you don't mind me asking?

Neuman KH 310 and 2 big colocated subs. I asked about the omni speakers because that was in the paper.

 

[Duke]

Neuman KH 310 and 2 big colocated subs. I asked about the omni speakers because that was in the paper.

Thanks.

Ime the arrival direction of the supporting late-onset reflection energy matters (though not as much as having adequate time delay).

Figure 7.8 in the 4th edition of Floyd Toole's book gives applicable guidance, as it's indicating which multispeaker set-up configurations are the best for conveying envelopment. I try to do something like (b) in Figure 7.8; (d) is just as good from the intended listening location, but results in a greater change to the relative path length distances as you move farther away from the main speakers (and therefore closer to the rear, supporting speakers), and I prefer to err on the side of having a larger listening area:

The set-up geometry in the paper described in the initial post is like (f) above, which did not score among the highest for envelopment, so maybe there is room for improvement by using a different set-up geometry.

Eyeballing the horizontal and vertical polar maps for the KH310, I wouldn't want to add energy to the reflection field below 500 Hz or so because the radiation pattern is widening significantly down there already. And I probably would not want to add very much between 500 Hz and about 1.6 kHz.

Just my opinion.

 

[john61ct]

Interesting! My noobish understanding is like transients performance ("crisp tight" vs smeared)

smoothing for a larger sweet spot is directly opposed to enabling (increasing the odds of) envelopment

 

[Duke]

smoothing for a larger sweet spot is directly opposed to enabling (increasing the odds of) envelopment

I don't understand this. Could you elaborate?

 

[john61ct]

I don't understand this.

You and me both! LMAO

Just a trade-off that (perhaps falsely) has gelled in my mind after reading thousands of posts, not finished dr @Floyd Toole 's 4th Ed book yet, no hands-on

And I'm certain the "natural only what's embedded in the content mix" side is convolved in my brain with the synthetic "simulation using DSP" possibilities.

As an example, MIMO approaches to using lotsa LF drivers to expand the resonance "smoothing" over a wide multiple LP area

apparently may work against one or the other ways to strive for that spatial "perception of envelopment"

I'm afraid that's all I got.

The small listening room vs bigger ones

and correlated vs de-

are further complications I'm only vaguely aware of.

 

[Duke]

You and me both! LMAO

Just a trade-off that (perhaps falsely) has gelled in my mind after reading thousands of posts, not finished dr @Floyd Toole 's 4th Ed book yet, no hands-on

Regarding your statement that "smoothing for a larger sweet spot is directly opposed to enabling (increasing the odds of) envelopment", I don't think that is the case, at least not in the context of what I was advocating (a physical layout that maintained good arrival-time separation between the main speakers and support speakers over a larger listening area, namely configuration (b) from Figure 7.8 in Toole's book).

Here are some relevant thoughts from David Griesinger which emphasize the importance of having a good arrival-time separation between the direct sound and the strong onset of reflections:

"Envelopment is perceived when the ear and brain can detect TWO separate streams: A foreground stream of direct sound. And a background stream of reverberation. Both streams must be present if sound is perceived as enveloping.... Where the background stream is easily separated from the foreground stream, envelopment is about 6 dB stronger for a given direct-to-reverberant ratio."

 

[john61ct]

I never stated any certainty around that idea, in fact what you left out was

> My noobish understanding is...

I would be VERY happy to learn that is false, just my misinterpretation.

Also, I have no idea about the further time domain issues you mention and do not see any connection between those and how MIMO solutions work for "smoothing for a larger sweet spot"?

 

[NTK]

My understanding from reading Dr Griesinger is that to have high low frequency envelopment (or in Thomas Lund's terminology, I think, auditory envelopment or AE), you want to be in front-to-back room modes (peaks) and lateral side-to-side nulls (high lateral pressure gradient) that are close enough to each other in frequencies for significant overlap. The front-to-back modes are to provide the sound pressure whilst the lateral nulls provide the ITD fluctuations.

To me it seems the conditions for LF envelopment are more restrictive than for uniform mono-bass across a wide listening area.

Source: https://audioroundtable.com/misc/asa05.pdf (I could not access davidgriesinger.com at the moment. I'd have preferred to link from his site.)

 

[Duke]

I never stated any certainty around that idea, in fact what you left out was

> My noobish understanding is...

I apologize for not acknowledging that.

Also, I have no idea about the further time domain issues you mention

Can you tell me what I mentioned that wasn't clear? I'll try again.

and do not see any connection between those and how MIMO solutions work for "smoothing for a larger sweet spot"?

Are you talking about optimizing for smoothest in-room bass over the largest possible listening area versus optimizing for best low-frequency envelopment? If so, imo there are trade-offs between the two.

 

[john61ct]

Yes that is ALL i was trying to say. Perhaps the way I phrased it was overstating that trade off.

TBH this is all so much over my paygrade I prefer to just read and keep learning

 

[Duke]

Yes that is ALL i was trying to say. Perhaps the way I phrased it was overstating that trade off.

TBH this is all so much over my paygrade I prefer to just read and keep learning

Ah, thanks. And if I came across as abrupt earlier, I really didn't mean to! The last thing I'd want to do is be mean to someone who's interested in this tiny niche of the home audio universe.

My approach to juggling the partially-conflicting requirements of smooth in-room bass and good low-frequency envelopment is briefly described in post #33. Based on two decades of use and customer feedback it seems to work pretty well, but there are probably signal-processing-based approaches that will do a better job.

 

[john61ct]

Thanks and no worries, all good

 

[john61ct]

I'm sure barely relevant

and only intended for music recordings where the bottom end has been pillaged

AudioControl has a unit called Epicenter, designed for automotive use

that uses DSP to identify remnant upper harmonics from that artificially removed LF content

and "reconstructs / restores" it, maybe just one octave lower, or maybe more ?

You must feed FR signal for it to work, not pre- filtered LP material.

Its wired remote has two level controls, overall Volume - which acts as a Sub volume depending one how you deploy the downstream output

the other varying the "intensity of the restoration" process.

The Pro version lets you set a bass boost PEQ, center frequency and width.

I plan to test it using REW + ears, between Wiim output and SYN input, on content that seems bass deficient.