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Thread: Adjusting room sound using DSP (not damping)

  1. #41
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    Default Dpa

    hi,

    yes, i use the lyngdorf DPA-1 preamp (including room perfect) feeding an electrocomapniet AW250-R amp and my M40.1. for me the room correction is simply the BEST tuning device in hifi-business. you will no longer think about cables or other negligibilities. in my (somewhat difficult) room the lyngdorf allows for 31 Hz (-2dB) without any frequency artifacts.
    given the very cheap prices for lyngdorf stuff it is simply a must for any critical room.
    btw: i just saw that mc intosh now released a room equalizer with lyngdorf technology (costing double the price as lyngdorf here in germany)...

    the only "problem" with the lyngdorf i can think of is: if you are a hardcore analogue user you might (more psycologically) have a problem with the d/a conversion of analogue signals.

    best,
    delgesu

  2. #42
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    Default TACT room correction & how to interpret graphs

    I have just purchased a second hand Tact 2.0 RCS and am about to start on trying to use this in my room with my Harbeth Compact II units. I appreciate what Alan says about the rigour when using any RCS set up and that it is based on a single postion but looking at the TAct at least this does not need to be the case. There is a facility to take average measurement for the main listening position but you can also combine doing measurements from a number of positions then combing them and getting a filter option that optimises the sound averaged for all the positions. Now of course this will be a compromise but as I view using this as something to help with room problems then it should be effective.

    There is also the option on the Tact to set up to 20 different filter / adjustment memory settings so you could have one set up for just solo listening one for when there are two sat next to each other and another for when there are a number of people listening (probably not that critically) . each could then be used as needed.
    I am not expecting the Tact to solve all my problems nothing ever does but if I can get it to let the Harbeths just get on with their job then it will be worth it.

    If anyone knows of any primer (or even simpler) articles on how to read a signal frequency graph then add some links as I have no problem in admitting I am not that knowledgeable in this area .

  3. #43
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    Default Fiddling with inter-channel phase ....

    A newly joined member says that he has had good results with this DSP room correction system here: http://www.audiovero.de/en/

    It seems that they have a demo version?

    One thing I have to report about a DSP system I've been experimenting with: the system calculates and introduces an inter-channel time delay of a few thousandths of a second. This significantly changes the quality of voice, 'cleaning it up' etc. etc.. However, if the DPS remains in circuit but this delay is overwritten and set to zero, voice returns to its normal characteristic, and even though the overall speaker/room response remains a flat line (or whatever line you program).

    The worrying thing is that the magic effect and definitely audible change is seemingly related to nothing more than the inter-channel phase difference, the ear being astonishingly tolerant of all the normal room's usual sonic lumps and bumps. Was I disappointed ....
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  4. #44
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    Default It really works - free trial

    Quote Originally Posted by A.S. View Post
    A newly joined member says that he has had good results with this DSP room correction system here: http://www.audiovero.de/en/

    It seems that they have a demo version?

    One thing I have to report about a DSP system I've been experimenting with: the system calculates and introduces an inter-channel time delay of a few thousandths of a second. This significantly changes the quality of voice, 'cleaning it up' etc. etc.. However, if the DPS remains in circuit but this delay is overwritten and set to zero, voice returns to its normal characteristic, and even though the overall speaker/room response remains a flat line (or whatever line you program).

    The worrying thing is that the magic effect and definitely audible change is seemingly related to nothing more than the inter-channel phase difference, the ear being astonishingly tolerant of all the normal room's usual sonic lumps and bumps. Was I disappointed ....
    Alan,

    I've known Uli Brüggemann for a number of years and his software is not a sham at all.

    The easiest way to get an impression is to measure your system in room with the SW you can download for free. Then you send him a couple of pieces of music of your own own choice and he will convolve them for you and them back. You can then compare as you like.

    I understand your careful approach to this issue, but beyond the reality that you must re-measure when you make changes in your room I can only say that I find the results I have heard with acourate very impressive.

    I have heard acourate applied in a room that was totally unacceptable with lots of hard surfaces and I would not have thought that possible.

    I have no financial or other interests in these products except as an enthusiast of good sound.

    Greetings from Brussels

    Robert

  5. #45
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    Default Audiolense DSP system

    Alan,

    I had been used Harbeth M40 for about two years and found its bass was too much in my 20" x 16" listening environment. Eventually, I solved the bass problem by using another room correction software called Audiolense which is very similar to Acourate.
    The sound is still Harbeth sound but the bass problem disappeared and did not bother me anymore. Moreover, the sound is really transparent and has no electronic signature at all.
    It also has time domain correction which makes the sound image very stable and well defined.

    I am very happy with the result.

    Link: http://www.juicehifi.com/index.html

  6. #46
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    Default Avr

    I see there are some AVR amps with room correction too.
    Maranz/denon use audissey, like the SR5007, Yamaha use his own technology called YPAO.
    Anyone tried them?

  7. #47
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    Default Post Bristol 2015 thoughts - 5: room correction software, overview

    NOTE: THIS POST (and a few relevant following posts) HAS BEEN CLONED FROM THE ABOVE THREAD AND MERGED INTO THIS THREAD>>>

    We used the Dirac system (in playouts from my Vista laptop but never on CD direct to the amp) on Friday and Saturday but not at all on Sunday, when a Windows issue concerning a USB plugged into the laptop without consent then prevented it from seeing the main external music drive and the Dirac software from loading. So if you listened on Sunday, both on playout from the laptop and from CD, the sound was direct, unprocessed into the amplifier and on to the speakers.

    I made a quick room measurement on Thursday night after we had set-up the room and furniture, and used the 'auditorium' setting, intended to give the best possible sound to a nine seated listeners in the middle of the room in a 2, 4, 3 seat arrangement rather than optimised for the more typical one or two users on a couch at the sweet spot at home. If time had permitted, it would have been interesting to try both modes.

    Moving the microphone around the listening area and making a technical measurement at those nine points in space took about 20 minutes, and the Dirac calculation of average sonic behaviour across the seats and the subsequent calculation of a best-fit room correction filter just a minute or two. At that point, the Dirac system had made a suggestion for what it thought would give the flattest response (note: it cannot know about such esoteric concepts as 'best sounding') leaving the user to accept without input the suggestion or able to tweak the solution by boosting/cutting/shaping and levelling individual frequency bands at will. There was, in effect, an infinite override, down to fractions of an octave. That infinite flexibility is both an advantage and a great danger.

    The basic low-end behaviour of the SHL5+ in the room was, as Sunday vistors would have heard (without DSP) surprisingly good. How much of that was due to the slightly dryer, tighter bass tuning of the SHL5+ relative to the previous models, how much due to the room absorber panels behind the speakers (more on that leter), and how much due to good luck we'll never know. We just plonked the speakers down where we though they looked OK in the surroundings and ticked that off the list. The DSP system was certainly capable (on screen) of perfectly smoothing the inevitable low end speaker-room lumps and bumps, not that is was a night and day experience: humans are remarkably tolerant of the bass effect of real speakers in real rooms. The issue with the Dirac which need much more study is not at the low end of the audio spectrum, it's because the Dirac is a full-range, wide band system, as capable of adjusting the signal passing through it at 50Hz or 20,000Hz with equal impact.

    Once the Dirac system has 'swept' the room at the various measuring points, it presents the user with what it measured, averaged, and a suggested correction curve across the entire 20Hz to 20kHz audio spectrum. That curve can be saved. The user is then encouraged to slightly or significantly re-shape that target curve, and to save those as alternative room correction strategies. In theory, it would be possible to have one adjustment curve for every CD/LP or even for individual tracks, giving the listener precisely the sound he wanted, not only in the bass but at any frequency across the audio band: the ultimate graphic equaliser for both room, recording and taste. A tool of that power in the hands of an inexperienced user (that is, me) can be very dangerous indeed, and I found in the hour of so that I played with drawing (in the GUI) various slightly alternative overall target curves that fractional adjustments here or there of half a dB or so had a very significant effect on the subjective mid/top presentation. Yes, the response could be made ruler flat (or not, as desired) but that did not correlate with the best sounding (to my ears).

    My impression is that restricted to the low frequencies only, say below 200Hz, the Dirac system could do a fine job of getting the best out of the speaker/room interaction that applies to all speakers in all real world rooms. However, extreme care and lots of accumulated personal experimentation is needed to confidently apply the DSP power in the midband, presence and top where unlike in the bass, the software tended towards wanting to boost the speaker output. If you do go for a room correction system then my latest thinking is that the AntiMode system with its limit of action to 500Hz or so is a much safer bet for the inexperienced user presented with an infinite possibility to screw-up a perfectly good sounding mid/top balance. The Dirac system is a fabulous tool, but it is dumb, and some weeks would be needed to learn how to tame its inherent enthusiasm to attack and smooth out every single lump and bump in the overall frequency response of the speakers in any given room when sonically, many should be left well alone, uncorrected.

    The experience as a novice of setting up and applying the Dirac system has the same feeling as giving the keys of an Aston Martin to a 17 year old who has just passed his driving test and asking him to drive it with care. The inevitable over-reaction to the power and potential is guaranteed.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  8. #48
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    Default Just another equaliser?

    Quote Originally Posted by A.S. View Post
    a Windows issue concerning a USB plugged into the laptop without consent then prevented it from seeing the main external music drive and the Dirac software from loading.
    Can't believe these things still happen!

    The experience as a novice of setting up and applying the Dirac system has the same feeling as giving the keys of an Aston Martin to a 17 year old who has just passed his driving test and asking him to drive it with care. The inevitable over-reaction to the power and potential is guaranteed.
    In what it is different from the equaliser function that can be found in nearly any player software, except from the fact that the starting curve could be precomputed by a tentative room correction system? I mean, this power is nowadays free for everyone to use and misuse...

    By the way: you said nothing about the PC to DAC connection, so I guess in the end you used a straight USB cable.

  9. #49
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    Default Simple DIY room correction and DACs?

    Quote Originally Posted by Nessuno View Post
    In what it is different from the equaliser function that can be found in nearly any player software, except from the fact that the starting curve could be precomputed by a tentative room correction system? I mean, this power is nowadays free for everyone to use and misuse... By the way: you said nothing about the PC to DAC connection, so I guess in the end you used a straight USB cable.
    I see your point. If the user has the means to make a technical measurement of the listening room around the listening sweet spot somehow or other, then armed with that knowledge he could use any means, including FOC graphic equaliser software built into some software media players, to negate the inevitable peaks.

    Yes, that must be true, but there is much more subtle correction that can be implemented with a dedicated room correction system. I'll see if I can find the snapshots I took of the before/after performance in-room using the Dirac to best advantage.

    One thing the AntiMode user guide mentions, and they are absolutely right about this, is that after the inevitable room-interaction bass peaks are reduced in loudness and a technically superior bass response is achieved, most listeners complain about the sound being too thin and bass light. This is because we have become so used to hearing the warming-up effect of peaked-up bass when playing ordinary speakers in our ordinary rooms that when we reduce the peaks we crave for what we're missing. The user guid then goes on to explain that after correction, they suggest applying gentle, progressive bass lift, to bring back the subjective warmth in the lower registers.

    As for the PC > DAC issue, once the dust settles I'd like to look at that subject in much more detail. Again, discussing it briefly with Martin Colloms, he and I approached the issue from radically different positions. I commented that based on an afternoon of listening and following listening, spectral analysis of the output of DACS using basic equipment, I had been able to whittle down a selection of DACs to those I considered usable for an important public demonstration and those that I could not. He stated that he had technically assessed 'hundreds' of DACs, and did not recognise from my observations the issues I had encountered 48 hours before setting-up. That was a surprise, since his knowledge and skills and doubtless test equipment far exceeds mine. The DAC I used was a Tascam US-122 Mk2 whch had a life-saving feature of an output volume control, to be sure the amplifier input was not overloaded. That's a critical point, as we've seen with CD player inputs to amplifiers elsewhere on HUG.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  10. #50
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    Default Measuring the frequency response of the Marriot Hotel Bristol, demo (bed)room No. 232

    As mentioned, out of hours I was able to use the measurement capability in the Dirac system to measure the frequency response of the loudspeakers firing into the room across three rows of seats covering most of the seated area, perhaps ten times greater area than what we would normally consider to be the audiophile's listening sweet spot. We can anticipate that the presence of the relatively hard walls, the frames of the chairs and all the other reflective surfaces in the room will greatly disturb our nice, smooth anechoic loudspeaker technical performance. And it does, and it's nothing short of a miracle that the human ear/brain can make any sense at all of the sonic confusion, let alone marvel at 'high fidelity sound'. Here is a picture of me positioning the microphone for the second attempt I had at this, at the end of Friday:

    Second sweep-sc.jpg

    You can see how close the side (and rear) walls are to the seated area, and included in the measurements, from this picture of my granddaughter on a visit to the show. I am in the rightmost seat. Note the portable panel absorbers on the right wall - they would have no effect at all at low frequencies.

    J&ABristol-sc.jpg

    Attached you will see what a mess a normal domestic-like untreated room makes of the otherwise relatively flat speaker frequency response. Each feint blue curve is the frequency response as seen by the microphone at one point across a nine-seat sample, the mic being placed in the middle of what would be the seated listener's head.

    As we can see, the bass octaves are the most troubling bands (as expected) with very large peaks and troughs because the high energy, long wavelength sounds are trapped in the room, unabsorbed, and bounce around causing constructive and destructive interference which manifests itself as peaks and troughs. All normal rooms look like that; in fact this room would have measured worse if we had not used a little sound absorbing. Also note the orange line: that is what the Dirac system has estimated would be at least a first-pass suggestion about how it would like to correct all the ups and downs in the room/speaker response. If the user so wishes he can accept that, or adjust the spots along the orange line up and down, just as he would with a graphic equaliser. We can then see what, left to its own devices, the maths in the Dirac software will do to pre-correct the signal going into the loudspeakers so that the resulting predicted measured response across the listening area will be as shown, and could be proved to be as shown. I think that you'll agree that is a truly astonishing technical achievement of pre-EQ by the exact amount of boost/cut needed at every frequency to flatten out the mess that we initially observed.

    > (Note: the images may appear in reverse order in your browser, but the before/after should be obvious.)
    Attached Images Attached Images
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  11. #51
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    Default !!!

    What a little cutie and no, I don't mean Alan.

  12. #52
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    Default Graphs?

    Are there any graphs of the computed correction curve and of the actual measurements with this correction applied?

    {Moderator's comment: That is exactly what you see in the 'after' curve. A computed and implemented flat line across the averaged listening area, as shown.}

  13. #53
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    Default Measured response?

    Quote Originally Posted by Nessuno View Post
    Are there any graphs of the computed correction curve and of the actual measurements with this correction applied?

    {Moderator's comment: That is exactly what you see in the 'after' curve. A computed and implemented flat line across the averaged listening area, as shown.}
    Anticipated response and Target is written on that graph. So if I'm not misinterpreting it, they are what the controlling system aims to reach (target) as optimum and how much of that it expects to reach given the actual controlled system (anticipated response).
    I'd like to see, if it is possible, the measured response after the correction, to see if and how the anticipations are realized and the correction curve applied to get that response (I'd expect something "complementary" to the measured uncorrected response shown in the "before" graph).

  14. #54
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    Default Validation of corrected response

    Quote Originally Posted by Nessuno View Post
    Anticipated response and Target is written on that graph. So if I'm not misinterpreting it, they are what the controlling system aims to reach (target) as optimum and how much of that it expects to reach given the actual controlled system (anticipated response).
    I'd like to see, if it is possible, the measured response after the correction, to see if and how the anticipations are realized and the correction curve applied to get that response (I'd expect something "complementary" to the measured uncorrected response shown in the "before" graph).
    The Dirac system comprises two independent programs. The measuring/calculating program (graphs shown) and an implementation module which sits as a virtual sound card between the playout program (Adobe Audition in my case) and the real sound card (the USB DAC) and applies the correction in real time to the signal.

    The calculated filter is saved to disc and then loaded into the implementation module, which can turn on/off a filter at the click of a button to hear the effect. Four alternative filters can be stored and called at will.

    There is no validation process as far as I can see. That would require a secondary measuring system (PC or whatever), but I would expect the response to be fairly close to that anticipated by the measuring/calculating module recognising that it is generating a correction filter based on an average of what it measures to be the speaker/room behaviour over a number of seats. Anyway, using an independent means of verifying the in-room resulting response would be good practice.

    The issue as I see it is that extremely small adjustment of the target curve by user intervention can and does have a very significant effect on the sound we hear with correction on.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  15. #55
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    Default Very large boosts?

    If we presume Dirac takes an average of your measurements (I realise it uses an algorithm) it needs to apply a boost of around 18dB to 40Hz and 120Hz for example. If it operates on one reading it will try to add 32dB to 50Hz.

    These are large, possibly damaging increases. Does it really do this. Is there some sort of safety net that prevents excessive boosts.

    My experience is that narrow dips like the one at 50Hz don't effect the sound we hear.

    My guess is that measurements should have been made with people actually sitting on those nine chairs as that must have a big impact on the sound.

  16. #56
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    Default The realities of the room

    So the 'messy' in room readings are pink noise signals?

    That's quite something and makes a mockery of the notion of sonic signatures in amplifiers, assuming even if there are differences in inherent sound those differences would be small. It is obvious just moving around a room when music is playing that the sound changes constantly, and really quite significantly, it is easy to find a space that is swamped in bass and one where it seems almost absent, its all very interesting!

    {Moderator's comment: Could be pink, but Alan used the alternative swept sine tones}
    Getting to know my C7ES3

  17. #57
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    Default Intelligence

    Quote Originally Posted by Hipper View Post
    If we presume Dirac takes an average of your measurements (I realise it uses an algorithm) it needs to apply a boost of around 18dB to 40Hz and 120Hz for example. If it operates on one reading it will try to add 32dB to 50Hz.

    These are large, possibly damaging increases. Does it really do this. Is there some sort of safety net that prevents excessive boosts.

    My experience is that narrow dips like the one at 50Hz don't effect the sound we hear.

    My guess is that measurements should have been made with people actually sitting on those nine chairs as that must have a big impact on the sound.
    That's a good point, hopefully the software is more 'intelligent' than that.
    Getting to know my C7ES3

  18. #58
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    Default More experiences?

    Are there any more experiences on this subject? To me, this still is the best opportunity to improve home audio, and even though the technology may still not be quite mature, a lot has already been achieved.

    To me this is far more exciting than negative discussions about the subjective sonics of valves, vinyl, cables, or even vibration eaters. Let us focus on what works.

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