Does DSP belong in State of the Art Systems?

[ErVikingo]

I have bass traps in the corners, cloud abfussers, (edit: add) abfussers on the reflection points, carpet and diffusers on back wall.

Limited on speaker positioning due to large projection screen. Also my speakers are 4 towers.

 

[cjf]

No analogue in my system, so no ADC to mess things up!

By "no bypass" I'm referring to full-range amps that include a DSP intended to correct for room anomalies. They can't do this of course - all they can do is mess the nice flat response the amp is designed so carefully to deliver! However, as the signal is a full frequency range one, the entire signal has to encounter the DSP if its engaged, as there is no way that the bass is separated out leaving the rest to bypass the filter and be reunited after the DSP for amplification. In active systems with 2 or more amps (bass amp with DSP, others without), this can be achieved, but not with a single amp.

I've used Dirac Live, RoomPerfect and MARS and all these adjust only the bass, but of course the entire range has to encounter the filter. This for my ears (and multiple visitors) is the problem as some of the "tingle factor" that exciting music generates is diminished if the filter is engaged. As it happens, my speakers have their own built-in bass amps with a form of DSP built in so I can keep the top and mid free of DSP, while the bass can be adjusted.

OK. so it does sound like you may be talking about "boxes" with built-in DSP functionality. One example being an AV Integrated Amp/Receiver but I understand that there are other higher end examples.

But the point being; one of the many problems with those devices is that you are typically left with whatever Freq curve they can muster with their built-in processing power/software. With the good stand-alone DSP software options previously mentioned you can take full advantage of the processing power of todays computers to create/use filters with 5-6 digits worth of "Taps" for correction purposes (ie..significantly more granular).

If I am mistaken in thinking that you are referring to an AV Integrated or similar type device being used to handle the DSP work please let me know. I would be interested in seeing a specific example of the devices you are referring to in that case. I am currently only picturing either a Sub with built-in DSP and an Amp or an AV Integrated type device falling into the "No Bypass" category you mention. But since there was also mention of the High Freqs being the concern, that really only leaves the AV Integrated or similar type devices being what we are talking about.

The description you mention about how your current speakers operate with the Woofer/Sub section being an Active unit with built-in DSP and the Top section remaining "Untouched" is possible with the stand-alone DSP software previously mentioned.

In my case, I chose to correct misbehaving Freqs everywhere they were found. My thought being, why would I leave an actual measured problem alone just because its above the Sub Freq range. I can say without hesitation that my system is much better sounding now, with DSP, than it ever was without it.

Lastly, I think I saw mention that perhaps someone didn't buy a good enough speaker to begin with and now must use DSP to make up for not having bought an ever better speaker that is believed to not require such band-aides like DSP. I've seen plenty of Top dollar systems around the web "In the Raw" (ie..without using DSP or DSP/Subs) with abysmal Room/Freq plots. All I can say is, they indeed spent more but I can't imagine how they are getting their monies worth in that state of tune.

 

[ecwl]

View attachment 125299
I honestly cannot understand this one.

Hmm… If you’re 390mm from front wall and 435 from back wall, your room is 33” deep not 27”. The 40Hz & 80Hz peaks are room mode resonances from the 33” depth but you’re definitely not sitting at the room mode which is why the peaks are not that high. However, their decay time is still significantly longer than other bass notes. When you listen to music, you might feel like there is more foundation to the bass but it would also blur all your other notes slightly whenever your music hits those 40 & 80Hz notes. To me, treating that would give you a lot more bang for the buck than trying to figure out how to treat the 45Hz or 140Hz dip.
Because you’re not sitting at a room node, you can probably place multiple very big and deep bass traps at your front wall and back wall to reduce the 40 & 80Hz resonance. Unfortunately, Vicoustic doesn’t make beautiful products for this purpose as their thickest wall products are too thin even for 80Hz absorption, let alone 40Hz. The less pretty GIK products do have 7.3” thick bass traps and even 17” thick corner traps that you can line along walls that would probably be better for this purpose. I guess active bass traps like PSI AVAA C20/C214 might work but since they’re so much smaller, strategic positioning for them would be important.

 

[sigbergaudio]

They can't do this of course - all they can do is mess the nice flat response the amp is designed so carefully to deliver!

I think there is a slight fallacy in your reasoning here. The goal should be to get that flat response all the way to your ears, and especially in the bass that's rarely what's happening. I do however agree with you that most automatic DSP systems don't do a great job at this. I guess the most notable exception I have heard is Trinnov (when configured correctly).

But what you can do is employ careful, manual EQ below say 100-150hz. This can vastly improve the bass response in most rooms. Often just 1-3 EQ points is needed.

Bjorn has shown some impressive results with room treatments. But this is not a practical approach for many, due to the amount of treatment necessary in the bass and the visual impact such treatment would have say in a normal living room.

 

[Bjorn]

The dreaded dip at 140-150 (and at 45). I have corrected most of this in my listening room. Still not perfect (thus why I am reading/educating myself about dsp options).

View attachment 125298

This is typical for most speakers. Correcting this with DSP is not a good choice. Raising the nulls, if possible at all, will increase distortion to serious high levels.

This should be resolved with a better speaker design, the use of one or two subwoofers, and doing the treatment which is possible. DSP is ok to use to adjust the bass to the gain you have from the surfaces, which will vary depending on distance to front wall and subwoofer integration. If you use DSP to correct much of the room anomalies and possible non minimum phase behaviour of the speakers, the result will not be very good.

 

[ErVikingo]

Hmm… If you’re 390mm from front wall and 435 from back wall, your room is 33” deep not 27”. The 40Hz & 80Hz peaks are room mode resonances from the 33” depth but you’re definitely not sitting at the room mode which is why the peaks are not that high. However, their decay time is still significantly longer than other bass notes. When you listen to music, you might feel like there is more foundation to the bass but it would also blur all your other notes slightly whenever your music hits those 40 & 80Hz notes. To me, treating that would give you a lot more bang for the buck than trying to figure out how to treat the 45Hz or 140Hz dip.
Because you’re not sitting at a room node, you can probably place multiple very big and deep bass traps at your front wall and back wall to reduce the 40 & 80Hz resonance. Unfortunately, Vicoustic doesn’t make beautiful products for this purpose as their thickest wall products are too thin even for 80Hz absorption, let alone 40Hz. The less pretty GIK products do have 7.3” thick bass traps and even 17” thick corner traps that you can line along walls that would probably be better for this purpose. I guess active bass traps like PSI AVAA C20/C214 might work but since they’re so much smaller, strategic positioning for them would be important.

@ecwl thanks for your feedback. Our math differs! 390 cm + 445 cm=835 cm thus 328.7 inches or 27.4 feet!

I have Seven Audio bass traps in all corners, 3 deep abfussers on the side walls, diffusers on the rear wall, cloud abfussers and a couple of ASC Tube Traps that i brought from prior listening room. Deep carpeted floors and a large down stuffed sofa. The room sounds awesome but I wonder about those nulls and peaks which remain. There is still some reflection in the room but I have always been careful not to ever dampen a room and end up with a dead room.

I am limited on how much I can move my speakers since I decided to put a huge screen for movies (with a separate audio system for that). I could post photos for reference but I'm afraid I would be detracting from the OP's thread which is about DSP.

Has anyone tried the AVAA?

 

[ErVikingo]

This is typical for most speakers. Correcting this with DSP is not a good choice. Raising the nulls, if possible at all, will increase distortion to serious high levels.

This should be resolved with a better speaker design, the use of one or two subwoofers, and doing the treatment which is possible. DSP is ok to use to adjust the bass to the gain you have from the surfaces, which will vary depending on distance to front wall and subwoofer integration. If you use DSP to correct much of the room anomalies and possible non minimum phase behaviour of the speakers, the result will not be very good.

I agree @Bjorn I wouldn't want to raise the nulls. I would use dsp to tame the bass peaks. My speakers have (IMHO) a great range and response (Infinity IRS Beta fully maintained/restored). They sounded better on the prior listening space which was wider and shorter.

I have 2 subs which are used on the movie system for LFE "vibration" (not for sound) which I could put to use on the audio system to correct room modes (if I can figure out where to place them).

 

[tony22]

Has anyone tried the AVAA?

There’s at least one person on the PS Audio forum who’s been using it and has written many posts about his experiences with it.

 

[ErVikingo]

There’s at least one person on the PS Audio forum who’s been using it and has written many posts about his experiences with it.

Thanks! Tony I have read that thread. I'll have a look to see if anything has been posted on that one or on the REW Rabbithole by Luca.

 

[ecwl]

@ecwl thanks for your feedback. Our math differs! 390 cm + 445 cm=835 cm thus 328.7 inches or 27.4 feet!

I have Seven Audio bass traps in all corners, 3 deep abfussers on the side walls, diffusers on the rear wall, cloud abfussers and a couple of ASC Tube Traps that i brought from prior listening room. Deep carpeted floors and a large down stuffed sofa. The room sounds awesome but I wonder about those nulls and peaks which remain. There is still some reflection in the room but I have always been careful not to ever dampen a room and end up with a dead room.

I am limited on how much I can move my speakers since I decided to put a huge screen for movies (with a separate audio system for that). I could post photos for reference but I'm afraid I would be detracting from the OP's thread which is about DSP.

Has anyone tried the AVAA?

Haha. That was embarrassing about the inches to feet conversion. Thanks.

Yes. I have the AVAA C214. It works very well but it’s just like a bass trap. So you still need to put it at the right spot. For example, clearly your bass traps at the corner were not absorbing the 40Hz peak adequately. My gut feeling is that you’ll need to put the C20/C214 in the middle along the front and back wall for maximum impact but I honestly don’t know. You may need to stand them up or lie them on the floor. Putting them behind the speakers along the front wall or back wall might also work. You may have to walk around the room with your microphone and see where the 40Hz resonance is building up and then see if you have space for the AVAA. And even though AVAA is smaller than deep big bass traps, they are still bass traps so having more of them would absorb more resonance. But because they’re active and just like with passive bass traps, you can sometimes get in situations where they absorb too much sound.

Since you have optimized everything else, AVAA is probably the way to go, as long as it fits within your budget and you can place them in the appropriate spots in the room. AVAA is definitely not the best bang for the buck but for those of us who are space limited, they can be a huge space saver.

 

[wil]

This is incorrect. It's aboslutely possible to treat room nodes/bass nulls. But treatment needs to be sufficiently efffective. A lot of sold commercial products out there aren't, and for very low frequencies surface area is very important.

I have shown several examples already where rome nodes and antinodes have been treated. Here's another example.

Before and after treatment.
View attachment 125250

View attachment 125251

Has anyone here looked at the BAACH foray into dsp or room correction? It's called ORC. Unfortunately, it looks like it is Mac based only.
One thing that sets it apart from other dsp's is the use of in-ear measurements.

BACCH-ORC

BACCH-ORC, A New Paradigm in Room Correction.

www.theoretica.us

 

[Bjorn]

Like Don Davis said many years ago: You can EQ the speaker but you can't EQ the room.

However, we can make adjustment of the speaker to fit the boundary and listening distance in the room. Room gain of lows will vary depending on both type of wall/surface and proximity of placement. And the treble falls more with distance. So this is something we can adjust the speaker for. We're not correcting the room, but simply giving the speaker the correct level in regards to the room gain and listening distance we have.

 

[PGA]

I wish that was generally true but, most often, it is not possible.

After fiddling with my system for 40+ years I must agree with Analog Scott and Kal.

I tried everything, including having my room professionally treated with RPG abfusors, diffusors and bass panels. Also went through many speakers including Wilson, Cello, Dunlavy, TAD and Magico. And many DACs and amps from Spectral, Cello, Levinson, MSB, Berkeley and Pass. For the most part the improvements (or better said, differences) were subtle.

At the behest of folks at Berkeley, I tried implementing EQ in the analogue domain, using high quality pro gear. That helped, but nothing really got me to where I wanted until I had Mitch Barnett design a convolution filter that in my system runs on Roon.

Now with the convolution filter the system sounds truly fantastic, even after I sold all the expensive cables, power conditioners and ultra expensive Constellation amps and Berkeley DAC. I have a more humble Meitner MA3 and a Pass XVR1 feeding four Benchmark amps, all with Benchmark wiring powering modified TAD R1s. And I've never been happier.

DSP will not eliminate distortion, deep nulls, flutter echo and reflections, so paying attention to the room is important. You should have a system capable of playing reasonably loud without compression or distortion across the frequency spectrum. And also unless you want to spend many hours trying to learn a fraction of what Mitch Barnett forgot about DSP, you're probably better off staying away from DSP. But given the processing power that's available today, DSP done right can be truly transformative.

For me the acid test was when I invited over a dear old friend that is a big analogue buff, with vintage tubes and horns. I expected he was going to literally throw up listening to my 100% digital system. But instead he was totally amazed. Paraphrasing his comments after listening for a couple hours he concluded that maybe there was a thing or two he liked better in analogue, but there were many many things my system did much better.

Again you have to start with a low distortion system that covers the frequency range, you need to get the room as good as you can (but not to the point of going nuts with room treatments) and you need a professionally designed DSP filter made for your room/speakers.

Having said this, I use a Denon receiver as a pre-pro running DIRAC for home theater in this room. It triggers a custom XLR AB switch bypassing the Meitner DAC. DIRAC is quite good, it's not as good as Mitch's convolution filter on Roon, but for special effects on an action movie it is more than fine. And it images extremely well even without a center channel.

 

[Analog Scott]

After fiddling with my system for 40+ years I must agree with Analog Scott and Kal.

I tried everything, including having my room professionally treated with RPG abfusors, diffusors and bass panels. Also went through many speakers including Wilson, Cello, Dunlavy, TAD and Magico. And many DACs and amps from Spectral, Cello, Levinson, MSB, Berkeley and Pass. For the most part the improvements (or better said, differences) were subtle.

At the behest of folks at Berkeley, I tried implementing EQ in the analogue domain, using high quality pro gear. That helped, but nothing really got me to where I wanted until I had Mitch Barnett design a convolution filter that in my system runs on Roon.

Now with the convolution filter the system sounds truly fantastic, even after I sold all the expensive cables, power conditioners and ultra expensive Constellation amps and Berkeley DAC. I have a more humble Meitner MA3 and a Pass XVR1 feeding four Benchmark amps, all with Benchmark wiring powering modified TAD R1s. And I've never been happier.

DSP will not eliminate distortion, deep nulls, flutter echo and reflections, so paying attention to the room is important. You should have a system capable of playing reasonably loud without compression or distortion across the frequency spectrum. And also unless you want to spend many hours trying to learn a fraction of what Mitch Barnett forgot about DSP, you're probably better off staying away from DSP. But given the processing power that's available today, DSP done right can be truly transformative.

For me the acid test was when I invited over a dear old friend that is a big analogue buff, with vintage tubes and horns. I expected he was going to literally throw up listening to my 100% digital system. But instead he was totally amazed. Paraphrasing his comments after listening for a couple hours he concluded that maybe there was a thing or two he liked better in analogue, but there were many many things my system did much better.

Again you have to start with a low distortion system that covers the frequency range, you need to get the room as good as you can (but not to the point of going nuts with room treatments) and you need a professionally designed DSP filter made for your room/speakers.

Having said this, I use a Denon receiver as a pre-pro running DIRAC for home theater in this room. It triggers a custom XLR AB switch bypassing the Meitner DAC. DIRAC is quite good, it's not as good as Mitch's convolution filter on Roon, but for special effects on an action movie it is more than fine. And it images extremely well even without a center channel.

Be careful who you agree with. I was banned for expressing these things here on this forum. This place should be renamed "What was sometimes best 40 years ago" forum. The tribalistic promotion of antiquated technology and straight up audio mythology and attacks on any perspective that does not toe this line is not for anyone who would be looking for true state of the art audio playback through DSPs such as the BACCH Crosstalk Cancelation filter or their ORC DSP.

As an aside TAD makes legit excellent speakers. I'm sure you are getting great sound.

 

[Tim Link]

And also unless you want to spend many hours trying to learn a fraction of what Mitch Barnett forgot about DSP, you're probably better off staying away from DSP.

After many hours of trying to learn a fraction of what Mitch Barnett forgot I'm inclined to agree with you. I don't mind experimenting a lot, and being disappointed a lot, so I'm OK with it. I've heard some interesting things come out of my system with various DSP implementations. My best results have come from only using convolution to correct a driver/horn combination's anechoic response. Trying to get a whole speaker and room combination into the convolution is always giving me some kind of artificial effect I don't like. There's just so much going in to a measurement taken at the listening position, and some of it is OK to correct and some is not. It's really tricky to know what to do there, and the measurement needs to be very clean, supporting what you said about a very good, clean, low distortion system and adequately treated room to start with. You don't want measured distortion or noise in any way impacting the convolution measurement. Garbage in, garbage out.
After reaching a point where I think I'd made some real progress, I turned it all off and just listened to the raw response. A little lumpy in a few spots but actually very easy to listen to. A few minor adjustments with basic EQ, and it sounds and measures at the listening position about as good as any of my more sophisticated approaches. Maybe better in some ways. It's really easy to over-do it with DSP.

 

[Tim Link]

Has anyone here looked at the BAACH foray into dsp or room correction? It's called ORC. Unfortunately, it looks like it is Mac based only.
One thing that sets it apart from other dsp's is the use of in-ear measurements.

BACCH-ORC

BACCH-ORC, A New Paradigm in Room Correction.

www.theoretica.us

I've been interested in that system. I have not used it myself but I do use a cross talk reduction method, and I'm a big fan of reducing inter-aural crosstalk between speakers. I've come up with my own system that can be done in the analog domain, similar to what Polk does with it's SDA method, and probably what Carver does with sonic holography, although I don't know much about how that works. I use an array of 3 speakers in the middle of the room. It works really well, and I don't see myself abandoning this setup unless I get something like BAACH at some point. I already have the Mac in my audio system so I'm part way there. There's another product called SoundPimp that uses a similar scheme as BAACH although not as thoroughly sophisticated. SoundPimp can produce a wider soundstage than my array, often too wide. I don't think the violin soloist should be completely off to my left, as entertaining as that effect is.
What I've found is it's mostly the comb filtering above 2000 Hz that's the problem. Maybe a little lower than that if your speakers are spaced wide apart. So below that a standard 2 speaker setup does enough for anything but extreme special effects, like sounds seeming to be right next to your ear. Above that there really is some serious degradation that is still, I think, greatly underappreciated in the high end world for the problem that it is. DSP is one way to fix it, but not the only way. I know there's a lack of agreement about how much of a problem it is. For many I think the sound of that crosstalk and the associated strong comb filtering and phase reversals have become an accepted norm, as essentially correct at best, or at worst not a serious issue.
Once the speaker crosstalk is dealt with, treatment of early room reflections seems to have more upside potential. My earliest reflection is the wall behind me. I treated that, and it's been a big step up in terms of imaging. Next is the ceiling. I experimented by just blocking the path to my ears with a cushion and I'm convinced it's the next thing I'm doing. The sidewalls are a ways away in my setup, so I assumed they weren't too important. But recent experiments with using cushions to block those along with the ceiling wowed me, so after I get some excess furniture out of the listening room I'm going to be getting after those side walls.

 

[pjwd]

T

After many hours of trying to learn a fraction of what Mitch Barnett forgot I'm inclined to agree with you. I don't mind experimenting a lot, and being disappointed a lot, so I'm OK with it. I've heard some interesting things come out of my system with various DSP implementations. My best results have come from only using convolution to correct a driver/horn combination's anechoic response. Trying to get a whole speaker and room combination into the convolution is always giving me some kind of artificial effect I don't like. There's just so much going in to a measurement taken at the listening position, and some of it is OK to correct and some is not. It's really tricky to know what to do there, and the measurement needs to be very clean, supporting what you said about a very good, clean, low distortion system and adequately treated room to start with. You don't want measured distortion or noise in any way impacting the convolution measurement. Garbage in, garbage out.
After reaching a point where I think I'd made some real progress, I turned it all off and just listened to the raw response. A little lumpy in a few spots but actually very easy to listen to. A few minor adjustments with basic EQ, and it sounds and measures at the listening position about as good as any of my more sophisticated approaches. Maybe better in some ways. It's really easy to over-do it with DSP.

Tim,
I'm just starting a process of using acourate for crossover filters as a crossover ( aided by a friend) and as far as I can see getting it all as close as you possibly can prior to using acourate is the key .. I measured all drivers outside and up in the air to get halfway decent clean measurements ...in the first go with acourate it appeared ( unsuprisingly) to use room response as a part of the calculation.. esp at low fr ..I have always wondered how that worked .. I will try and do a convolution filter based on measurements and then correct from there to see how it goes.
It still is a black box of mystery to me !
Phil

 

[SeagoatLeo]

I do not want DSP in my system. I want simplicity. It's good that posters achieved great and pleasing sound using DSP. I chose to build custom listening rooms rather than throw money at gear. My last home of 28 years, I built to withstand earthquakes (100% safe in 1994 in Chatsworth) with the listening room being 25'X23'10' avg H, 5.5" 3000 psi steel reinforced concrete, staggered 8" apart 2X6's on 8" plate, dual drywall & sound board 5/8" each and 2' footings. Power in a subpanel 20 amp breakers. Etc. When I moved in 2019, I only had left with an interior of 20X15X10 but at a cost of $150K and very superior construction (not SOTA but good enough). My new speakers were set up in under 1.5 hours (typically 5 hours) because I had bass traps built into the 16" walls (activated carbon). See following for details. I chose to build the room first, then add equipment. It is on the live side with instant good feeling on entering (only 33-35 db background noise level, not as good as my master bedroom which is under 30 db).

Listening Room Construction It is custom but not SOTA materials
Floor-Poured steel reinforced to 12” 3000 lb. PSI concrete floor

Walls-
1” MDF
1/8” thick Acoustiblok vinyl sound barrier
¾” MDF
3 x 12 vertical studs, 14.5” on center
Staggered 12.6” wide 2 x 12 and 4 x 12 per vertical stud channel
13” X 4” X 48” 72lb. 4 chamber activated charcoal absorption filters staggered vertically up/down/up/down
4” Rockwool insulation over vacant stud channel area adjacent to filters Flexseal all joints
¾” cherry plywood
Doors-Same construction as Walls 17" thick swinging 84" & 96" high
Side Walls - 5X 4' X 2' X 3" wood framed acoustic absorption panels

Ceiling
4’ Sound Absorption Blankets
4” Rockwool
2 x 8 horizontal beams
5/8” X drywall paneling Flexseal all joints
1/8” thick Acoustiblok vinyl sound barrier
¾” cherry plywood
Ceiling - 6X 5' X 3' X 6" wood framed acoustic absorption panels

Recessed 9 BR 40 65 Watt LED floodlights
2 Ton HVAC split system, low speed, high volume
90+ oz. plush cut pile carpeting
Power-Separate Sub-panel for audio only outlets (Synergistic Research Blue), 10 gauge wiring, 20 amp breakers. Nothing special.

Funny thing is that my Living Room second system that came with the house is fantastic. It has french doors to the right and is 2/3rds open to the left. Filled with stuffed seating and glass&mahogany full size cabinets on front and rear walls. However, it has 2.5 walls with tufted 1" curved wall paneling. The sound is great everywhere in that room with superb imaging and sounds wonderful in the adjacent 1,600' of dining, foyer, hallway and family room. Only after purchasing the Von Schweikerts do I have that quality of even dispersion in my listening room.

 

[Ron Resnick]

Has anyone tried the AVAA?

PSI Audio AVAA C20 Active Bass Absorber

That's great! As I detailed in my system thread I bought two AVAAs! Ordered 2 of the analog 20’s today. Excited to put 2 of them in my space.

www.whatsbestforum.com

 

[iansr]

@PGA; I think you’re on the wrong forum . Don’t you know that analogue is good and digital is bad, because, because, well it just is . . .

I speak as someone who intends engaging Mitch’s services.