DSP/room correction a good idea with Naim stuff? Or bass traps?

Said most in header.

Interested in open discussion (but in my case the room is 4m x 5m and 10 ft high; 2 windows on one long wall (exterior wall) and mostly "Venetian plaster" the other long wall. The 2 other, short, walls = solid but with a 230 sq cm fancy plastic pane for picture frame, and the same at 650 sq cm, also mirror 170 sq cm. Oak floor with a third of exposed area covered with a rug).

Original Post

I would do everything possible to improve room acoustics with layout, speaker position, soft furnishings, bass traps etc. before resorting to DSP. Then, if you’re not satisfied, I might consider running a sub connected to a pre out via dsp rather than using it to process the signal running to your main speakers. 

DSP will alter a bit perfect data and therefore aways degrade sound quality.

Unless you're willing to fill your room with massive quantities of sound absorption material then no bass trap will be effective below 100hz (where most room bass issues are).

The best solution is speaker and listening chair positioning and matching speaker to room, the hardest thing in this hobby to get right imho.

I've had good responses in my 4.3m x 4m room with ATC SCM19 and Harbeth 30.1 speakers. Both work well without over exciting room modes. Basically stand mount sealed or front ported speakers will work best in problem rooms.

I’ve recently done an experiment with Dirac on a laptop. In that room, the improvement was quite impressive. It takes less than an hour to download the Dirac demo version and calibrate the room. Then you can compare by playing some music with and without Dirac and decide if the impact is positive in your room.

I see no problem in using dsp for bass frequencies ..... I use a small velodyne dd10+ sub from output of my 552 ..... it is fantastic. The main speakers still get an unaltered full fat signal ..... the trick is to use small speakers and augment subtly ... my little pmc 20.21s sound fantastic.....this on the end of a 500 system..you must not oversize your speakers in problematic rooms. Another approach would use say an nd555 into Kii fully active full dsp speaker....there are allot of positive reviews on this revolutionary speaker.

 

You can also use the DSP in Roon, although as a sort of glorified digital graphic equaliser, I’m a little concerned that there will be a price to pay in sound quality. With a new Naim streamer, it would be useful as a means of assessing the effect of reducing any bass nodes caused by the room. 

Gazza posted:

Jason from Naim was asked at a ND555 demo.......if the door is a problem sound wise, change the door or do something to improve the door/acoustics. Whatever you do , do not mess with the sound signal........a Roy George mandate.

Absolutely, if you understand to what extents Naim design their implementation of a relatively  modest single low pass filter DSP function in their DAC/Streamers so as to cause minimal signal distortion and side effects, I think that engineering effort would need to be multiplied severeal times to have a cascade of filters required for room correction so as to cause minimal distortion. Each filter also adds digital noise albeit if well designed at very small levels.

if one was going to do this I suggest the the best place would be as part of the DACs inline DSP function where one has already oversampled and increased the sample word size so as to reduce the impact of arithmetic errors.

Sadly D48Rs will always reveal the bass resonance of that room unless you use quite dramatic DSP filtering (which will also induce unwanted side effects).  It will be best to use much smaller speakers and a sub that's controlled by a DSP; even then to completely eliminate the bass resonant peak, you will still need bass traps (but this way they can be a fraction of the size they would need to be to handle the output of D48s at the resonant frequency of your room).

The other thing you'll find of considerable benefit is to do is use room treatment (such as diffusers and absorbers) to deal with the reflections.  Dealing with acoustic problems in a room with acoustic solutions (i.e. eliminating the issues where they occur) will always give a better result than trying to compensate for the acoustic problems by mucking about with the electrical signal.

Some people seek to avoid bass tesonances by choosing speakers that simply don’t go low enough to be a problem - but if you value the bass in the music that clearly is not an option. Otherwis, particularly when considering existing speakers that you like and don’t want to change, you should seek to optimise speaker and listening position first, then consider room treatment, and only when you have done whatever is possible and domestically tolerable DSP may be of assistance to improve things if significant problems remain.

The balance then is any negative effect of the DSP on sound quality, which may or may not be evident to you, vs the negative effect of room issues. Reducing bass where there are peaks in response at the listening position can be quite effective, and to some extent noosting dips, but beware that boosting  can much more seriously affect system performance, and can even Damage speakers, while if a the problem is a cancellation effect it will never actually be able solved by boosting.

The reason boosting is not adviseable other than only slightly is this:  say you have a 12dB dip - by no means an extreme example: To raise the level at that frequency by 12 dB means 8 times the power, so if you are  playing at a level where crescendos use any more than one eighth of the power amp’s maximum peak power capability before clipping, boosting by 12dB would mean any peaks in the music at that frequency  would take the amp into clipping on those peaks, risking damage to speakers and possibly amp.

IB, that's a very good point about not trying to use DSP boost nulls and dips, however you underestimated the problem...
Raising the level by 12db is 16 times the power (not 8 times).

What you say about using positioning and acoustic treatment of the room before final adjustment with a DSP is also very valid.

In terms of using small speakers, there is another option to loosing bass performance.  Use small speakers that don't excite the resonant modes of the room, then fill in the bass using a sub controlled by a DSP that reduces and evens out the resonant bass frequencies.  This way you get the advantage of DSP based control of the room modes without having the DSP filtering causing artefacts at the rest of the audio spectrum, particularly in the mid range and lower treble where the ear/brain combination are particularly sensitive to tiny changes in audio quality.

Allan Probin posted:

Wouldn't DSP applied to the sub feed introduce a small delay? if so, wouldn't an identical delay need to be applied to the main output to keep the bass signal in phase with the main speaker output?

There's a greater delay caused by the group delay of the Class D amp in the sub (typically about 2.5-4ms delay).

The answer to this is simple...
Position the sub closer to the listening position (typically about 1-1.5m closer to the listener than the main speakers are will be about right).

Allan Probin posted:

Wouldn't DSP applied to the sub feed introduce a small delay? if so, wouldn't an identical delay need to be applied to the main output to keep the bass signal in phase with the main speaker output?

I have an N-Sat + Velodyne sub combination fed by my Nova and there is no audible delay. It works very well in my 5mx5mx2m room (less than ideal!) with no treament. Bass is excellent and I do sometimes play dub reggae really LOUD!

Another way of applying DSP for those who want to tri-amp (pr bi-amp) their speakers is to use a digital active crossover with capability beyond simply splitting the signal - which can be used to tailor response in-room, regardless of whether peaks or (small) dips in response are caused by the speaker or the room.

Yes, it's the coherency through the sub's crossover region and the timing that are affected and audible (rather than the phase of the harmonics, which is a much less audible factor as the phase relationship of the harmonics of any sound source naturally varies with the distance to that source).

That's why having the sub 1-1.5m closer to the listener works better than having it co-located with the main speakers.

Huge posted:

the phase relationship of the harmonics of any sound source naturally varies with the distance to that source).

Huge, that's interesting, I haven't come across that before. It seems more intuitive to me that for a point source the phase relationship of the harmonics with the fundamental would be fixed, regardless of distance. Would it be possible to give a simple example with numbers?

OK no problem

Take a sound with a wavelength of 10m and consider the 2nd harmonic (which has a wavelength of 5m)

At source the waves are in phase,
at 2.5m the 10m wave is at +90°, the 5m wave is at +180°
at 5m the 10m wave is at +180°, the 5m wave is back to +0°
at 7.5m the 10m wave is at +270°, the 5m wave is at +180°
at 10m both waves are back to +0°

(All phases expressed relative to the source, at the same time.)

How do room correction measure the response?  If you measure the integrated response and adjust after this then you change the direct/early reflection sound. (which is not affected by the room).

Or is the room correction boxes smarter than I think they are?

I have a diffusor behind the normal listening position aand absorbents in back corners.

Huge posted:

OK no problem

Take a sound with a wavelength of 10m and consider the 2nd harmonic (which has a wavelength of 5m)

At source the waves are in phase,
at 2.5m the 10m wave is at +90°, the 5m wave is at +180°
at 5m the 10m wave is at +180°, the 5m wave is back to +0°
at 7.5m the 10m wave is at +270°, the 5m wave is at +180°
at 10m both waves are back to +0°

(All phases expressed relative to the source, at the same time.)

Ok, Got it! Thanks very much

Huge posted:

Sadly D48Rs will always reveal the bass resonance of that room

yeah, these speakers. Gotta chew what you say.

So, you think this stuff is kinda called out for cos of these 2 babies?  A few pieces like diffusers you mentioned. But the bass traps especially important?

(I've got IsoAcoutics Gaia IIs for the spkr feet.)

Thanks

Allan Probin posted:

Wouldn't DSP applied to the sub feed introduce a small delay? if so, wouldn't an identical delay need to be applied to the main output to keep the bass signal in phase with the main speaker output?

Although it will depend on digital filter design and type the extent of the delay, which will be more typically manifest as a phase error. So yes if using digital filters in this way, you are effectively creating a digital cross over and one should use the same filter kernel sizes (taps) or equivalent for both the low pass and high pass filters.

The whole thing with DSP is quite interesting ......... consider this - the hi fi industry strives to meet very tight standards - essentially trying to attain a flat frequency response ........ however the rooms most people use.........probably introduce.......at least 5dB variation or more .......... I am sure Naim is correct DSP does alter sound quality,....... however if you get a correction benefit of 5 db or more ......... then the sq hit is more than compensated for . It is interesting that the Kii speaker is loaded with complex DSP and class D amps ......... but gains rave reviews.........

I have recently changed rooms ........ and I had a really nasty 60hz boom that i could not eradicate by placement ......... I tried Roon DSP and put a notch in at 60hz and bingo....it is terrific ......... however, listening deep into the mix I am sure it has done something......air/space/image placement seems to be marginally effected. But the gains due to the boom eradication are very very impressive . My solution ultimately - may mean a speaker change to an infinite baffle speaker such as the P3esr....and remove the DSP..... 

I have the D48R as well. I assume you are trying to do everything possible before you have to move them on for something more appropriate for your room ?

Have you tried or are able to demo. isolation feet under the speakers ? Someone here with similar speakers have Herbie Fat Gliders under theirs and swear by them. 

Richieroo posted:

The whole thing with DSP is quite interesting ......... consider this - the hi fi industry strives to meet very tight standards - essentially trying to attain a flat frequency response ........ however the rooms most people use.........probably introduce.......at least 5dB variation or more .......... I am sure Naim is correct DSP does alter sound quality,....... however if you get a correction benefit of 5 db or more ......... then the sq hit is more than compensated for . It is interesting that the Kii speaker is loaded with complex DSP and class D amps ......... but gains rave reviews.........

I have recently changed rooms ........ and I had a really nasty 60hz boom that i could not eradicate by placement ......... I tried Roon DSP and put a notch in at 60hz and bingo....it is terrific ......... however, listening deep into the mix I am sure it has done something......air/space/image placement seems to be marginally effected. But the gains due to the boom eradication are very very impressive . My solution ultimately - may mean a speaker change to an infinite baffle speaker such as the P3esr....and remove the DSP..... 

I guess it’s each to their own Richie. Jason at Naim mentioned Roy George was against DSP as they go to great lengths to keep the signal integrity for sound quality......then mess around with it? He gave a simple example if your door is affecting the SQ, do something about the door, not the signal processing. So I take from that it’s not going to be a Naim option any time soon.

Gazza posted:
Richieroo posted:

The whole thing with DSP is quite interesting ......... consider this - the hi fi industry strives to meet very tight standards - essentially trying to attain a flat frequency response ........ however the rooms most people use.........probably introduce.......at least 5dB variation or more .......... I am sure Naim is correct DSP does alter sound quality,....... however if you get a correction benefit of 5 db or more ......... then the sq hit is more than compensated for . It is interesting that the Kii speaker is loaded with complex DSP and class D amps ......... but gains rave reviews.........

I have recently changed rooms ........ and I had a really nasty 60hz boom that i could not eradicate by placement ......... I tried Roon DSP and put a notch in at 60hz and bingo....it is terrific ......... however, listening deep into the mix I am sure it has done something......air/space/image placement seems to be marginally effected. But the gains due to the boom eradication are very very impressive . My solution ultimately - may mean a speaker change to an infinite baffle speaker such as the P3esr....and remove the DSP..... 

I guess it’s each to their own Richie. Jason at Naim mentioned Roy George was against DSP as they go to great lengths to keep the signal integrity for sound quality......then mess around with it? He gave a simple example if your door is affecting the SQ, do something about the door, not the signal processing. So I take from that it’s not going to be a Naim option any time soon.

Quite possibly that's an outdated view on the capabilities of DSP and could be referring to a largely analogue World.

With a digital source its theoretically possible to apply room related adjustments (ie those below 100Hz) without messing up the signal.

And don't forget, the signal has already been mangled by much worse processing as part of the production process.  It's also rather purist to think that a majority of customers can move doors or alter rooms in other ways to suit the hifi, most of us don't have that luxury.

I believe Naim are already on board with DSP in MuSo and Bentley, so I wouldn't rule it out. As long as they make it optional, that would suit everyone.

Gazza posted:

 

 Jason at Naim mentioned Roy George was against DSP as they go to great lengths to keep the signal integrity for sound quality......then mess around with it? He gave a simple example if your door is affecting the SQ, do something about the door, not the signal processing. So I take from that it’s not going to be a Naim option any time soon.

Good in theory, though I note from the system photos on  forum that not many people have treatments evident in their rooms, even with the more expensive kit, yet all rooms inevitably have an effect (not just doors), though of course some more than others. If faced with a room having objectionable adverse effects that for whatever reason cannot be fixed by room alterations (domestic harmony, other room uses, available homes etc), then DSP may well be the better answer.

And I certainly don't understand people denying themselves part of the music by changing to a small speaker with reduced bass output just to cope with a particular bass problem like a strong peak at 60Hz or whatever: to me that needs either room treatment or DSP (or both), otherwise it is cutting off one's nose to spite one's face. Any negatives of the DSP are outweighed by fully hearing the music.

I am not a fan of DSP based correction as it’s influencing the signal as such. I am myself using quite non-intrusive physical room correction. It doesn’t need to be big and ugly to be effective as you can see in my room, where most people wouldn’t immediately recognize it. And it’s not totally perfect, but it’s miles away from a room without correction. The problem as always is that you would need to change it again with change of components like me bringing in my ND555 which created more extension in bass....., but ok that’s the journey.

I am also a firm believer of adaption of your speakers to at least the room dimensions. Not saying you shouldn’t have full dimension speakers in a small room, but be a bit sensible of comparing dimensions and the capabilities of the speakers.

sunbeamgls posted:

Quite possibly that's an outdated view on the capabilities of DSP and could be referring to a largely analogue World.

With a digital source its theoretically possible to apply room related adjustments (ie those below 100Hz) without messing up the signal.

And don't forget, the signal has already been mangled by much worse processing as part of the production process.  It's also rather purist to think that a majority of customers can move doors or alter rooms in other ways to suit the hifi, most of us don't have that luxury.

I believe Naim are already on board with DSP in MuSo and Bentley, so I wouldn't rule it out. As long as they make it optional, that would suit everyone.

I already tried that approach doing DSP on the files, using various techniques, including upsampling to 24/192 before processing (and then writing the file at that resolution to avoid a second loss of quality).  In all cases the processed files lost something even in frequency areas that hadn't been manipulated.  A subtle loss was of quality was always particularly noticeable in the mid range and with voices.

This is why I only do DSP in the feed to the sub leaving the feed to the main speakers unprocessed.

Bert Schurink posted:

I am not a fan of DSP based correction as it’s influencing the signal as such. I am myself using quite non-intrusive physical room correction. It doesn’t need to be big and ugly to be effective as you can see in my room, where most people wouldn’t immediately recognize it. And it’s not totally perfect, but it’s miles away from a room without correction. The problem as always is that you would need to change it again with change of components like me bringing in my ND555 which created more extension in bass....., but ok that’s the journey.

I am also a firm believer of adaption of your speakers to at least the room dimensions. Not saying you shouldn’t have full dimension speakers in a small room, but be a bit sensible of comparing dimensions and the capabilities of the speakers.

I also have to add that I am relatively blessed with a good setting of the basic conditions. The part of the room I am listening in is 6 by 4,5 meter, so means I am about 3,5/4 meters away of the speakers. The issues with it overall, echoes and bass are pretty easy to compensate with my room correction. Only 5 small panels. Others might not be so blessed with an easy room.

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