What is Dirac/DLBC doing to my sound ?

[mcdn]

If you can, try pushing the speakers all the way to the front wall. This will push the first front wall reflection above the baffle step frequency. Also move the sub further away from the left speaker, preferably to a wall boundary.

I know this isn’t the traditional advice, but that advice was developed before room correction was a thing. The raw response will have more bass peaks, but those can be corrected by Dirac.

 

[pollock0424]

@mcdn
I wish that I could push them way back, but I have a floor raising projector that is mounted to my component table that is in between the speakers. I will try moving the subwoofer.

 

[OCA]

How do you simulate this speaker boundary reflections ? I mean the equations ?

It's basic geometry really but formulas in the XL are optimized after cancellations. All you need to know is that sound is reflected from a flat surface by the same angle it hits that surface. As an example, here's the drawing for floor reflection:

and other first reflections:

I have tested all the formulas to be correct with various online tools more than once in the past but I wouldn't bet a million dollars that they are all error free.

 

[OCA]

Not sure why this is NOT happening with the right speaker with the same magnitude, although they're symmetrical when considering ceiling and front wall.

It could be a side/rear wall peak (or its harmonic) cancelling that dip for the right speaker.

I think, your LP is too close to the rear wall. Why don't you move the seat forward a bit to 1/5th of room length (2.3ft from rear wall)? You can achieve optimal stereo separation distance between speakers (8ft), achieve more than half of the optimal (6ms) first reflection delay (3.7ms) in a configuration like below:

 

[pollock0424]

It could be a side/rear wall peak (or its harmonic) cancelling that dip for the right speaker.

I think, your LP is too close to the rear wall. Why don't you move the seat forward a bit to 1/5th of room length (2.3ft from rear wall)? You can achieve optimal stereo separation distance between speakers (8ft), achieve more than half of the optimal (6ms) first reflection delay (3.7ms) in a configuration like below:

View attachment 338972

I tried sitting 2.3ft from the rear wall. I took a measurement and it looks like I have a worse dip at 120hz although I didn't notice it during listening. The fact that I have a desk and chair at the right hand side corner and a bookshelf to the left hand side corner doesn't help the intuitive reasoning. Also, did you calculate these time bands in this picture by Distance ÷ Speed of sound ?

 

[OCA]

I tried sitting 2.3ft from the rear wall. I took a measurement and it looks like I have a worse dip at 120hz although I didn't notice it during listening. The fact that I have a desk and chair at the right hand side corner and a bookshelf to the left hand side corner doesn't help the intuitive reasoning. Also, did you calculate these time bands in this picture by Distance ÷ Speed of sound ?

Most dips are not nearly as audible as the peaks so long as they are not caused by phase differences (due to asymmetric placement) between the left and right speakers. I'd rather focus on imaging depth and width during speaker placement.

did you calculate these time bands in this picture by Distance ÷ Speed of sound ?

The algo is robust. I used a script written by Richard Taylor in asymptote vector graphics language (attached). You can run it online here:

Asymptote Vector Graphics

asymptote.ualberta.ca

Btw, 6ms optimal delay is claimed by Linkwitz. Toole thinks it's about 5ms. Very few rectangular rooms are big enough to achieve this.

 

[pollock0424]

I can generate a 2D depth map in which each pixel indicates depth from a speaker perspective or even full 3D point clouds of my space. Have you come across any software that can simulate the sound field given this data? At that point, it should be clear where the treatments have to be done, if any. Recently, I attended NeurIPS 2023 conference and I came across PhDs presenting work on how to create life like natural sound... they're measuring impulse response of the space at various locations and using deep neural networks to model the space.

 

[OCA]

they're measuring impulse response of the space at various locations and using deep neural networks to model the space

I was wondering why is this kind of work still not out there. Sound United for instance have access to gazillions of room measurements to train an AI but all they came up after 25 years since the last big thing (Audyssey) is a double bass array derivative.

 

[pollock0424]

@OCA
I also found this resource to calculate SBIR nulls/peaks. Similar to your tool

SBIR calculator

SBIR calculator

tripp.com.au

 

[davidc]

Please excuse that I am coming into this without studying the whole thread. However, if your main L/R speakers are full range capable of reproducing low bass, could the problem be that DLBC automatically puts a high pass, non-defeatable filter on the main channels?

 

[pollock0424]

Please excuse that I am coming into this without studying the whole thread. However, if your main L/R speakers are full range capable of reproducing low bass, could the problem be that DLBC automatically puts a high pass, non-defeatable filter on the main channels?

I verified that my AVR is indeed setting a crossover at 70hz as recommended by DLBC and upon doing a sweep by turning off the sub, I found that the speakers were being rolled off.

 

[davidc]

I verified that my AVR is indeed setting a crossover at 70hz as recommended by DLBC and upon doing a sweep by turning off the sub, I found that the speakers were being rolled off.

This is the reason that I have decided not to use DLBC in my system as my main speakers are fully capable of reproducing bass as good as any subwoofer. I am anxiously awaiting ART to become available for my Denon AVR.

I posed the question of the high pass filter that DLBC applies to DIRAC, and received a reply from Flavio, who usually goes by "flac" on the forum. Here is his reply.

Flavio Fellah commented:
Hello,
yes, Dirac Bass Control applies a high pass filter but you can define at which frequency... very low if desired, please take into account though that the capabilities of reproducing the lowest frequencies at a relatively high volume are often very limited (hence a subwoofer is used)
However, if you want to take full advantage of all the capabilities of all speakers, then you need ART (Active Room Treatment) as it doesn't use crossovers.
It's possible that your Denon will support it but if/when are questions for Denon itself to answer

Kind regards,
Flavio

 

[pollock0424]

This is the reason that I have decided not to use DLBC in my system as my main speakers are fully capable of reproducing bass as good as any subwoofer. I am anxiously awaiting ART to become available for my Denon AVR.

I posed the question of the high pass filter that DLBC applies to DIRAC, and received a reply from Flavio, who usually goes by "flac" on the forum. Here is his reply.

Flavio Fellah commented:
Hello,
yes, Dirac Bass Control applies a high pass filter but you can define at which frequency... very low if desired, please take into account though that the capabilities of reproducing the lowest frequencies at a relatively high volume are often very limited (hence a subwoofer is used)
However, if you want to take full advantage of all the capabilities of all speakers, then you need ART (Active Room Treatment) as it doesn't use crossovers.
It's possible that your Denon will support it but if/when are questions for Denon itself to answer View attachment 340994
Kind regards,
Flavio

Unless you have very expensive speakers and monster power amplifiers that can handle the low end easily, I recommend getting a subwoofer or two! On top of that placement of low frequency reproducers is the key to attaining good LF response. Now, if the speakers+amp combo is capable you're still limited by placement hence the separation of LF from everything else. ART and DLBC all of these Wizz bang gizmos do help but you can't get a software to replace physical arrangement of reproducers/speakers. Please look into Fletcher Munsor curves and their implications for LF energy requirements. Most of the time in an untreated and not properly placed system, what you hear is the room boom, may not sound boomy but still the room dominates. Subwoofers have come a long way and my Rythmik E15HP changed my mind, even when considering that my speakers are rated for 25hz@-3db. Not to mention, my sub alone has a power reserve of 600 watts. 15 inch servo controlled cone mated to a 600 watt amplifier, you'll have to spend a LOT to get this kinda response/SPL from a full range speaker.

Just my reasoning for doing things the way I'm doing. Some of it probably doesn't apply to you..

 

[davidc]

Unless you have very expensive speakers and monster power amplifiers that can handle the low end easily, I recommend getting a subwoofer or two! On top of that placement of low frequency reproducers is the key to attaining good LF response. Now, if the speakers+amp combo is capable you're still limited by placement hence the separation of LF from everything else. ART and DLBC all of these Wizz bang gizmos do help but you can't get a software to replace physical arrangement of reproducers/speakers. Please look into Fletcher Munsor curves and their implications for LF energy requirements. Most of the time in an untreated and not properly placed system, what you hear is the room boom, may not sound boomy but still the room dominates. Subwoofers have come a long way and my Rythmik E15HP changed my mind, even when considering that my speakers are rated for 25hz@-3db. Not to mention, my sub alone has a power reserve of 600 watts. 15 inch servo controlled cone mated to a 600 watt amplifier, you'll have to spend a LOT to get this kinda response/SPL from a full range speaker.

Just my reasoning for doing things the way I'm doing. Some of it probably doesn't apply to you..

These are all excellent points. I agree that main speakers that can reproduce the bass output of good subs are rare, but luckily, I have them. See the link below for the description of the VMPS Super Tower III's. Regarding the power needed for these, they are very efficient (96 dB/watt/1m) and each channel is driven by a bridged Carver PM-2400 amp (before anybody goes quoting the review of the non-refurished Carver amp that was recently tested here, mine have been refurbished). Bridged, the amp produces
Good Morning,

One last question regarding DLBC and the Denon AVR’s.

Gene Scala of Audioholics and Phil of Masimo mentioned that DLBC will put a high pass filter on the main L/R speakers when implemented. Given that I have main speakers capable of handling the bass, if I used even one subwoofer and DLBC, I may be sacrificing.

Does DLBC use a non-defeatable high pass filter for the main channels?

Thank you.

David Crandon

 

[davidc]

Unless you have very expensive speakers and monster power amplifiers that can handle the low end easily, I recommend getting a subwoofer or two! On top of that placement of low frequency reproducers is the key to attaining good LF response. Now, if the speakers+amp combo is capable you're still limited by placement hence the separation of LF from everything else. ART and DLBC all of these Wizz bang gizmos do help but you can't get a software to replace physical arrangement of reproducers/speakers. Please look into Fletcher Munsor curves and their implications for LF energy requirements. Most of the time in an untreated and not properly placed system, what you hear is the room boom, may not sound boomy but still the room dominates. Subwoofers have come a long way and my Rythmik E15HP changed my mind, even when considering that my speakers are rated for 25hz@-3db. Not to mention, my sub alone has a power reserve of 600 watts. 15 inch servo controlled cone mated to a 600 watt amplifier, you'll have to spend a LOT to get this kinda response/SPL from a full range speaker.

Just my reasoning for doing things the way I'm doing. Some of it probably doesn't apply to you..

Agreed. It is very rare that a main full-range speaker can reproduce bass as well as subs, but luckily, I have a pair. You can read the description of these VMPS Super Tower III's with the link below. Regarding power, fortunately, I have that covered as well. I have a pair of bridged-mono Carver PT-2400 amps (note that these are refurbished, unlike the recently poorly reviewed Carver amp on this forum). This amp is rated at 2400 watts @ 8 ohms (3000 watts at 4 ohms) RMS, 20-20kHz, at 0.1% IM distortion.

Interestingly, DIRAC has a white paper out about Bass Control that indicated they had plans to extend the DLBC to the main speakers in a system, but shelved the plan. I would have loved to have DLBC manage my main speakers as you are absolutely correct that without subs, the best possible placement is limited. But, adding more subs wouldn't sit well with my wife anyway.

VMPS Super Tower III https://drive.google.com/file/d/18wfa7-CGoPwHBxk4zJfK36Pk448BgXLM/view?usp=sharing

 

[pollock0424]

Agreed. It is very rare that a main full-range speaker can reproduce bass as well as subs, but luckily, I have a pair. You can read the description of these VMPS Super Tower III's with the link below. Regarding power, fortunately, I have that covered as well. I have a pair of bridged-mono Carver PT-2400 amps (note that these are refurbished, unlike the recently poorly reviewed Carver amp on this forum). This amp is rated at 2400 watts @ 8 ohms (3000 watts at 4 ohms) RMS, 20-20kHz, at 0.1% IM distortion.

Interestingly, DIRAC has a white paper out about Bass Control that indicated they had plans to extend the DLBC to the main speakers in a system, but shelved the plan. I would have loved to have DLBC manage my main speakers as you are absolutely correct that without subs, the best possible placement is limited. But, adding more subs wouldn't sit well with my wife anyway.

VMPS Super Tower III https://drive.google.com/file/d/18wfa7-CGoPwHBxk4zJfK36Pk448BgXLM/view?usp=sharing

Those look good. If I had those then I probably want to run them full range. What if you set DLBC crossover at 20hz. This will do HPF@20hz and your speakers will run full range. Is the problem here about Dirac "touching" the signal going to main speakers?

 

[davidc]

Those look good. If I had those then I probably want to run them full range. What if you set DLBC crossover at 20hz. This will do HPF@20hz and your speakers will run full range. Is the problem here about Dirac "touching" the signal going to main speakers?

No, I don't mind if DLBC touches the main signal. And, I didn't know you could set the crossover that low. But, that would mean any subs would reproduce only below 20Hz...which makes the use of them insignificant, right?

 

[pollock0424]

No, I don't mind if DLBC touches the main signal. And, I didn't know you could set the crossover that low. But, that would mean any subs would reproduce only below 20Hz...which makes the use of them insignificant, right?

Typically, not much content exists below 20hz even in movies but you could always use one DLBC bank this way and set other crossover points for other banks. Also DLBC optimizes the response/phase for mains+sub, surrounds+sub etc. So, you'll still get the benefit of DLBC phase optimization. If you have another bank set to 30hz, then DLBC optimizes the blend of your mains and sub at that frequency. You will still run the mains most of the full range this way. Music rarely has content below 30hz. It would be ideal if they optimize when letting mains run full range but that's not the case. You have to roll off mains.

 

[Alfachris]

I own a Pioneer lx805.....I had the same problem managing the bass on my 2 REL1508 Predator subwoofers....I realized that Dirac Live Bass Control was cutting my (large) main speakers at 70hz.....inconceivable for me!
I found that I could lower the cutoff frequency of the main speakers to 20hz....and I set the subwoofers manually to 120hz......it works very well