Is DEQX a game changer?

Thanks Andrew. Based on the collective comments coming in from you and Bombaywalla, I am thinking that I am at a "stop point" with speaker evolution. If there is a next step, it may be an off the beaten track approach that Andrew has taken.

Btw Andrew, if I correctly understand your custom design, your drivers are mounted in an open baffle frame. What is your experience with back reflection from the drivers? Any wave interference and cancelation effects? Many manufactures try to damp the back reflections in damped sealed structures (e.g., Paradigm and Magico) or use a transmission line approach (e.g., Vandersteen).

Also, many manufacturers like Revel design the front baffle to minimize wave inference effects. How does your design speak to front baffle interference issues?

Back to my original point, ... I am interested in reading about Al's set up experience with the sound box. As previously posted, it is not physically possible for me to move my speakers outside for an "anechoic-type" set up. Nevertheless, perhaps Al's sound box experience will persuade me that I can approach that goal.

P.S. Although I have reported this before, I believe that the DEQX PreMate has been a high yield investment in my rig. I am dubious that dropping $30K Magicos ("sans" DEQX) into my rig would yield a lot of grins if the music doesn't "sound" quite right because of time alignment issues, or if the room twists the FR of each speaker into a pretzel.

Thanks again guys.

Bruce

Thanks again Bifwynne. Glad I was able to contribute.
Very good responses from Almarg & Drewan77 esp. his feedback from personal usage over the past 3 yrs. I've also heard Magicos sometime back & agree with Almarg's findings.

Agree with Unsound - the Joseph Audio slopes are called "infinite slope". yes, they sure appear to be brickwall filters. He often gets a best of show award & I've heard his speakers - good sound but they never stood out.

Bifwynne, it looks like you've convinced yourself that your Paradigms are at the end of the line now. Only you can tell this & we take your word for it. If you try open baffle speakers, there are a few commercially available - Emerald Physics & DIY kits from Siegfried Linkwitz of Linkwitz-Riley fame. Maybe you want to order his kit & make it yourself?? This might be another option (other than building Drewan77's design)??
At RMAF2007 Nelson Pass was there himself in one of the rooms showing off his open-baffle speaker driven by one of his First Watt amps. It was quite experimental at that time but maybe that design is mature now & ready for ordering as a DIY kit?
Thanks.

Hi Bruce, my OBs only handle 100hz and upwards - each using four mid range drivers plus ribbon tweeters. All these are physically aligned (to the originating point of each) within a flat, tall and wide baffle & the speakers also have shallow tapering 'sides' which blend to the top edge. Sound waves can pass across the front surface and away to the sides but are constrained so they also transmit (only) to the rear. Nothing else behind the speakers apart from cabling and a single protective capacitor for each tweeter

There is free space beside and behind the speakers and I have no obvious issue with back reflections or wave effects/cancellations - but that's not to say they aren't there, it's just not apparent and I have no reason to check. The music room also has a lot of diffusing and absorbing material including a great deal of vinyl (+ CD storage)

In everything I have done, listening and then adapting has been the mantra until I achieve the sound I want - this has always been referenced to natural sounding live music. Research, theory and specifications are extremely useful but the real question should be 'what does music actually sound like'?

Sure, I made mistakes and I produced multiple low cost OB prototypes - each time I heard something I wasn't happy with, I then researched that particular aspect and adapted until it sounded right. My original intention was to try out OBs, learn and then build a pair of Linkwitz-Rileys but my own developments started to sound so good that I saw no need to follow that path. Maybe I just hit lucky or it's probably more likely that DEQX is capable of fully correcting something that is nearly there already?

I am confident that in my room and with my (mostly analogue source) preferences, this system is about as good as I could hope for

I have done nothing more to my setup for at least 2 years and can find no fault (so far). For the previous 40 odd years I constantly replaced and upgraded.... 'chasing the wind' as it were. Not any more and that's why I am very happy to see Bruce, Al and others starting on the same path because I know that the end point can be so satisfying

Wanted to post a report about an interesting and enjoyable audio experience.

Several years ago, I bought a Best of Roy Orbison 2 record reissue set. I was always disappointed because it seemed that Roy's voice was shifted to the right. It got to the point that I used the balance control on my linestage to shift the imaging. But the music still didn't sound right. Imaging was smeared across the sound stage, even when I played the record in mono mode.

Well, I got bored with the record set. Actually ... disappointed. So I put the record set away. I haven't played it since I bought my DEQX PreMATE ... that is until now.

So here's the report: Roy's voice is exactly where it should be ... dead center. The background singers and band appear to be properly placed too. Also, Roy's voice is not screechy like it was when I first played the LPs (Pre DEQX). As many may recall, the guy could belt out a song and he had quite a vocal range.

Since I'm still using the same phono pre, TT and cartridge, I attribute the sound improvements in staging and voicing to the PreMATE. Just sayin' IMO.

Cheers

BIF

Hi Almarg, I'll add my voice to those interested in your DEQX results.

My system uses a TacT 2.2X to provide DRC and crossover to subs. This is a big improvement in most cases, but with about 15% of my music library, the added grain or hardness from the TacT outweighs the benefits of DRC, so I bypass it. Besides being much newer, the DEQX apparently resamples only by integer amounts, which I suspect helps. (The TacT resamples everything to 24/96).

So, thank you for documenting this and the other participants for many interesting comments, also.

Thanks for the feedback Mike_in_nc. My friend used to have a TacT - wasn't the 2.2X but an earlier version - and he sold it shortly after he bought it. I think he owned it a year +/-. He said the same thing - there was a grain/hardness & said that the in-built D/A converters were not good enough.
I believe that TacT is long gone & replaced by Lyngdorf(sp?) - it's the same designer I understand but under another company name. TacT & Lyngdorf are out of Denmark, if I remember correctly...

Bombaywalla: Peter Lyngdorf (in Denmark) was a partner in TacT, is (or was) a principal of DALI, and has been involved with several other major audio companies. An important man in the field, to be sure! And yes, TacT itself is out of business -- a combination of poor marketing, arrogant customer relations, and the general reluctance of audiophiles to adopt DSP.

The TacT 2.2X is not terrible. In my system, it is good enough that I didn't detect its flaws until my system got better. I sure would like to find something that offers its benefits without the tradeoff in ultimate sound quality.

Update: Today I performed the close-up speaker measurements.

I moved the speaker being measured close to the center of my living room/listening room, with the Persian rug you can see in my system description photos folded back roughly in half. That resulted in the front baffle of the speaker being located 10.5 feet from the large window on the front wall (i.e., the wall behind the speaker). The speaker’s left side was located about 5 feet from the fireplace on the left. Its right side was located about 7 feet from the right wall, but just 4.5 feet from the large mahogany antique radio/phono console you can see along the right wall in my system description photos (the thing that looks like a Chippendale-style bureau, which I’m pretty certain weighs in the area of 350 to 400 pounds, and which I therefore wasn’t about to move. Its shipping weight in the large wooden crate in which it was sent to me about 20 years ago was 567 pounds!). The distance to the rear wall, the middle third of which is an opening to another room, was around 11 feet. I positioned the mic at a height of 30 inches, which placed it exactly between the heights of the two closely spaced tweeters on my speakers. When I measured each speaker, I moved the other speaker a few feet to the side of its normal position, to get it as far away as possible from the speaker being measured. I placed pillows on the rug between the speaker being measured and the microphone. I closed all the windows so that the mic wouldn’t pick up bird chirping and other outdoor sounds, and I turned off all noise-making appliances that were within earshot. Fortunately a noisy rainstorm didn’t start until a few hours after I finished with the measurements.

I made a total of 9 measurements on each speaker, three different distances (2.5 feet, 3 feet, 3.5 feet), times three setup conditions (no acoustic panels, two large double-section acoustic panels surrounding the microphone on three sides and projecting somewhat forward of it, and the same acoustic panels re-positioned to surround the speaker on three sides and project somewhat forward of it).

Each of the 9 measurements of each speaker consisted of a 2.4 second sweep repeated 9 times, with the sample rate set to its 96 kHz default setting (2.4 seconds being the longest sweep time choice that appeared to be offered at the 96 kHz sample rate). I adjusted the volume such that peaks were indicated in the DEQX software as being 102 to 104 db, which my speakers and amp can handle comfortably (even at listening distances). I wore a professional quality hearing protector (the kind designed for use with outdoor power equipment) during the measurements. The software indicated a “confidence level” of about 38 db on each of the 18 measurements.

All of this took a bit more than 4 hours, most of which of course involved moving and replacing the speakers, and setting up the mic, computer, acoustic panels, etc.

After viewing the impulse response plots corresponding to each of the measurements (on a much larger screen than my laptop provides), as I had suspected the ones taken with the acoustic panels surrounding the microphone were clearly the best, with the ones taken with the panels surrounding the speaker also being significantly better than the ones taken with no panels in place. The 2.5 foot measurements looked a bit better than the 3 foot measurements, which in turn looked a bit better than the 3.5 foot measurements. But I’m inclined to go with the 3 foot measurements due to the concern I expressed earlier in the thread about timing artifacts resulting if very close-up measurements are used, given the somewhat wide spacing of the drivers on my speakers.

The next step will be to generate speaker corrections in the software, utilizing those measurements. I’ll probably create two sets of corrections, one conservative and one somewhat aggressive, and upload them to separate profiles on the DEQX. I’ll then evaluate the resulting sonics with a variety of recordings, before attempting any room corrections. My next significant update is likely to be several days or more from now.

Finally, I’ll mention that Nyal (AcousticFrontiers), from whom I purchased the HDP-5, was kind enough to contact me the other day to see how I was doing with it, and graciously offered to review and comment on my DEQX project file. I’ll probably take him up on that in the coming days or weeks.

Best regards,

--Al

Congratulations Al, an excellent summary!

You have been very thorough in measuring your speakers and I am sure Nyal will give excellent advice to get the best from the system

We all look forward to your further updates

Thanks for the detailed update Almarg. Looks like you are making steady progress with the HDP-5. It's time consuming but that's the nature of the beast. The hardwork is all in the prep (pretty much like home-owner projects) to make good measurements as the correction (hence listening pleasure) is only as good as these measurements.

Drewan77- From your posts above it looks like might have some advice for me as I consider taking this route to upgrading the SQ of my system which can read about here. I am considering actively crossing over the output from the pre-amp so as not to run the field coils on the OB full range. Since my gear is in the LR, I do not have any realistic options for room treatment. I would like to insert the DEQX in the processor loop of my Doshi pre-amp because first, I love its sound, second, I use two sources, and third, I may want to use its DAC someday when my Transporter goes legs up, networked to my server. I am not a very technically oriented guy, so please keep that in mind. Also, if you think we should take this off-line, just send me a pm and I'll get back to you. One concern I do have is that the newer DEQX products seem to be very much oriented to an all-in-one PRE/DAC/EQ use and I'm not sure if that makes sense in my situation. Luckily, I have the ability to (relatively) easily move my speakers out onto a large screen porch to get speaker response measurements.

This is good stuff. Al, you are the right guy for this job! Could this be the holy grail of tweaks? On paper, to the extent I understand it so far, it (DSP done well and right) has teh potential. I can't wait to hear how it turns out.

Hi Swampwalker, I have sent you a PM with my email address

Al,

Can you copy the impulse measurements from your best test. In a perfect world, I surmise that all drivers should be in sync.

Thanks for the nice comments, guys.

Bruce (Bifwynne), I've sent you an .mzd file, containing all of the measurements and also my first speaker calibration attempts, which I'll start to assess sonically tomorrow.

Best,
-- Al

Al,

Did you happen to take a pic of the measurement setup that you can share?

Roscoe, no, I didn't take any pix while making the measurements.

Upon re-reading the description I provided of the setup, I would just add that I of course moved the chairs that are visible in my system description photos out of the room, and I mounted the measurement mic on a small professional mic stand which allowed it to be placed at the 30 inch height I mentioned.

Best regards,
-- Al

Thanks. I may try using some of the GIK panels to do something similar around the mic and compare that to the measurements without. Unless that seems like a boneheaded idea to some of you folks wiser than I.

Caution: Very long post :-)

Well, it seems that my forward progress has taken a step backward, although the step backward has resulted in discoveries that will hopefully be beneficial in the end, to me and to others who may read this.

After evaluating four different speaker correction profiles on numerous recordings, all based on measurements taken with the acoustic panels I purchased placed around the measurement microphone, I’ve concluded that even though those measurements, when viewed on impulse response plots over a reasonable time scale (e.g., 30 ms), looked considerably better than the measurements taken with no panels and with the panels placed around the speaker being measured, the panels were doing more harm than good. And I say that even though there were no points on the impulse response plots at which reflection amplitudes appeared to look greater with the panels placed around the mic than in the other plots, and at the great majority of points reflection amplitudes looked significantly smaller with the panels placed around the mic compared to the other two cases.

As will become clear later in this post, what I probably should have done was to place the panels up against the nearest reflective surfaces (the fireplace on the left and the large antique radio/phono on the right, as seen in my system description photos), rather than surrounding the mic with them on three sides, at a fairly close distance.

I’ll first say that one of those four profiles (one of the first two I tried, with the impulse response truncation window terminated 7.2 ms after the initial sound arrival, and corrections only performed between 600 Hz and 10 kHz), on most but not all recordings sounded distinctly better than bypass mode and than the other three profiles I tried (all of which had the window terminated about 18 ms after the initial sound arrival, with corrections over a somewhat broader range of frequencies).

However I noted especially on the last two profiles I tried that the image was shifted considerably to the right, even though bypass mode (as always) was perfectly centered. And that right channel boost (the difference being in the area of 2 to 6 db depending on frequency, and occurring primarily between about 200 Hz and 1 kHz) could be clearly seen when the correction profiles were viewed in the DEQX software, with the profiles for the two speakers placed on the same graph and the scale of the vertical axis suitably adjusted.

I also found while doing further experiments with the software that the volume difference between the two channels increased dramatically in proportion to the duration of the truncation window, which really puzzled me at first, and also increased in proportion to the distance of the measurement microphone from the speaker (meaning also that it increased as the distance between the mic and the panels behind it became smaller). And the volume difference was worse for correction profiles created from the measurements made with the panels surrounding the mic than for correction profiles created from the measurements made with the panels surrounding the speaker. And, as mentioned above, I found that the issue occurred primarily (although not exclusively) in the area of 200 Hz to 1 kHz, especially around the middle of that area, with the volume difference varying considerably at different frequencies.

After a lot of study of frequency response plots, impulse response plots, and step response plots, I concluded with a fair amount of certainty that the cause of the different corrections for the two speakers was that I didn’t have the panels placed in precisely the same locations when I measured the two speakers. The reason for the slightly different placements being that since I was making measurements with the panels surrounding the speaker as well as with the panels surrounding the mic, and it happened that I did the measurements with the panels surrounding the speaker last, I moved the panels aside when the first speaker being measured was moved away from the center of the room, and the second speaker was moved into that position.

Upon very close examination, the consequences of that can be seen in terms of slight differences between the timing of the wiggles of the impulse response measurements for the two speakers in the area of about 3 ms after the initial sound arrival, and can also be especially seen in the form of a roughly 1 db difference occurring at that same instant between the step response plots of the two speakers, in the cases of the measurements taken at 3 and 3.5 foot distances which I used for the correction profiles.

So, I wondered, if the issue was being caused by reflections from the panels occurring just 3 ms or so after the direct sound arrival, why would the consequences of those reflections in the correction profiles get worse as the truncation window was extended much further out in time, for instance from 7 ms to 18 ms and beyond? I’m not totally certain, but I believe the answer to that is inherent in the mathematics of the Fast Fourier Transform, some variation of which I assume is what the software uses to convert between the time domain (impulse and step responses) and the frequency domain (frequency responses).

Now if I were to redo the measurements while making a point of placing the panels at precisely the same locations for both speakers, I could evidently eliminate the inter-channel differences in the corrections. However, the fact that slight differences in panel placement caused dramatic differences in calibration profiles between the speakers would seem to say that even if I were to achieve identical profiles for both speakers, that identical profile would reflect (pun intended) significant adverse effects of the panels. So for that reason, in addition to the effort that would be involved in re-measuring the speakers, I’m not planning to do that. Instead I’m now planning to simply try some correction profiles that I’ll create based on the measurements I’ve already taken with no panels in place. If those don’t work out well, then I’ll consider re-measuring the speakers, with the panels much further from the mic and probably placed against the reflective surfaces I mentioned earlier.

Also, if I were to try to correct the inter-channel differences using the equalization capabilities of the DEQX, given the extensive variations of those differences as a function of frequency I suspect that the effort would be extremely time-consuming, and would probably result in a less than ideal set of complementary colorations.

So although my efforts have had a bit of a setback here, it’s probably a good thing that I didn’t make a point of placing the panels in exactly the same positions for the measurements of the two speakers. If I had done so I probably wouldn’t have discovered any of this, and I would very conceivably have ended up deriving less benefit from the DEQX than I hopefully will, eventually. So, undaunted, I shall persevere and carry on. Due to various unrelated upcoming activities, my next significant update will probably be in about a week. Meanwhile, just using the DEQX in either bypass mode or with the one correction profile I mentioned as being superior to the others, provides (despite a bit of channel imbalance in the case of the latter) a modest but notable improvement on what I previously had.

Best regards,
-- Al

A very interesting summary Al and I sympathise with the challenges you face

At the risk of repeating myself (apologies), are you absolutely sure that there is no chance of taking an outdoor speaker measurement?

I originally made several attempts to achieve a good indoor measurement but none came close to those taken outdoors. Once I saw the cleanness of the resulting plots, any further speakers or subs were always measured this way - including manhandling a huge Miller & Kreisel sub into the garden and then up onto the measuring platform which was a great deal of effort

It does make a significant difference and I believe that is why music created from the resulting calibrations sounds so remarkable. I am rather a 'perfectionist' so I couldn’t have rested knowing that I wasn't getting the maximum performance from DEQX

Yes, this can involve a lot of time and commitment (in my case around three hours from start to finish, moving the gear etc) but provided you use a high number of averaged measurements (I recommend 1.4s/96K x at least 18 sweeps) and the day is completely dry without much wind, the measurements only need to be taken once and are extremely accurate, virtually anechoic if done well. Any random birdsong or other faint wind noises appear to be completely disregarded by the averaging feature of the software

Somewhere I may have photographs of the setup but they are not on this computer so I will have to look for them. If anyone is interested I would try to find them plus some of the resulting measurement plots and post them as images on 'my page'

Thanks Al and Andrew. I guess I'll hold up on buying the panels for a bit. I'll wait for future reports.

Andrew, it may be that I will bite the bullet and schlepp my whole rig outside one day. Gotta tella ya though ... I am concerned about damaging gear by doing this.

As I've already mentioned, my rig is tucked away in my basement/sound-room. At a minimum, I'd have to haul up the steps: two 100 pound speakers; an 80 pound amp; and the DEQX. And what about my 110 pound sub?? I assume I can leave the other gear downstairs.

I have posted a couple of screenshots under 'System' at the foot of my posts for anyone with a DEQX processor to compare the plots

The measurement shows how 'clean' the frequency plot may look relative to an indoor reading that others may have taken and the impulse response illustrates that there is only a tiny reflection from the microphone itself

(The measurement is a raw image from the mid-high range speaker before any correction & at 0% smoothing. Indoor calibrations tend to use up to 100% smoothing and a closer windowing, both of which reduce accuracy and have an impact on the sound in my experience)

Al,

Interesting findings so far.

Sounds like the good news is the unit is providing you the information needed to get it set up optimally as it should, and that you are well versed to interpret and use it.

I wonder what the general recommended apporach from teh vendor is? Is anechoic measurements the norm for geting things calibrated initially? Sounds like it. In which case, there may be no equally effective substitute for some kind of plan for accomplishing measurements outdoors as suggested. Or in some other kind of anechoic environment. How about a recording studio? Maybe there is something like taht nearby at a school or other professional facility that might be accessible. Of course, no way to avoid the pain of having to move heavy and delicate audio gear that way. So it might be a dilemma for which one practically just has to accept some kind of compromise.

I'm sure its going to work out well one way or another in due time.

Andrew (Drewan), thanks very much for providing the info in your system description thread. As I indicated there, it provides a good quantitative perspective for DEQX newbies such as myself on what is possible in the speaker calibration process.

Mapman, thanks also. Regarding DEQX's recommendations for how to approach speaker calibration, on the one hand the manual states:

The microphone should be mounted about 2 ft to 3 ft (or 60 cm to 1 metre) from the speaker and lined up with the tweeter axis. Best results will be obtained if you use a microphone stand with a boom to support the microphone. If larger speakers are used it may be necessary to mount the microphone further from the speaker, in order to reduce the angle between the drivers and the microphone (and any
associated off-axis effects). However, moving the microphone further from the speaker will potentially increase measured room effects and /or reduce the period of the measurement before the first room reflection, hence the reason for the suggested distance of 3 feet. Better results may be obtained by measuring the speaker outside, provided that a quiet location is used. One method, particularly useful for large speakers, is to rest the speaker on the ground, pointing up at a 45 degree angle. The microphone should still be lined up with the speaker's
driver axis, i.e. it will be pointing down at the speaker at a 45 degree angle. When measured with this method, the speaker measurement can be similar to that obtainable in an anechoic chamber.

But on the other hand they state:

The longer the delay for the first room reflection to arrive relative to the time it takes for direct sound to reach the measurement microphone, the more bass information can be gleaned. A minimum target would be 3 milliseconds, which will limit measurement usefulness to frequencies above about 400Hz. Doubling this to 6 milliseconds for example, achieves an additional octave of bass resolution: down to about 200Hz, which is the lower correction limit used for this case. In this example, if you attempt to correct below 200Hz phase distortion will be introduced to the filter, which will make the resulting sound dull and flat - worse than the uncorrected speaker.

The 3 and 6 ms 400Hz/200 Hz guidelines seem very aggressive (optimistic) compared to inputs that were provided to me by Nyal, and that have been cited by others earlier in this thread, and that were used by the DEQXpert people when they set up Bruce's (Bifwynne's) system. (They terminated the "truncation window" about 17 ms after the direct sound arrival in his case, as contrasted with the 3 and 6 ms figures cited in the manual. Also, the corresponding figure in Drewan's case was about 18 ms).

So it seems that given the great number of variables that are obviously involved DEQX is understandably not able to provide a specific quantitative feel for the degree of compromise that will be introduced at various points along the continuum between ideal measurements taken under essentially anechoic conditions, and points that are significantly less than ideal.

06-07-15: Drewan77
At the risk of repeating myself (apologies), are you absolutely sure that there is no chance of taking an outdoor speaker measurement?

Pretty much. Just moving my speakers off and then back onto the bases and footers I have them on, which elevate them less than 5 inches, involved non-trivial effort and careful logistical planning, as they weigh 108 pounds each. To get them to a location outdoors that is both level and not close to reflective surfaces they would have to traverse several steps and approximately 50 feet, and then I would have to provide some non-reflective means of tilting them back, to minimize ground reflections. Also, less significant additional complications would be that I would have to run about 50 feet of speaker cable (my amplifier also weighs more than 100 pounds), and a 40 foot or so XLR extension for the mic.

Well before deciding to purchase the DEQX I had realized from the comments earlier in the thread and from reading the DEQX literature that as a practical matter I would be unlikely to realize its full potential. But as long as it ends up providing me with a substantial improvement over what I had I won't be disappointed. As Mapman aptly said just above, "it might be a dilemma for which one practically just has to accept some kind of compromise."

Best regards,
-- Al

Al, outdoor measurement is mandatory, IMO. With the help of two people, we moved TAD Reference1 (almost 400 lb apiece) and four monoblock amps from my listening room to my driveway. We used a dolly, easily purchased on the internet. If you are willing to invest the time and cash on DEQX, you really owe this to yourself.

Al,

Were you to decide to undertake the task I would gladly volunteer to help with the schlepping. PRoblem is I do not live very close. Maybe there are some other strong and trustworthy folks out there who live a bit closer that might be willing to lend a hand as well if it comes to that.

Psag and Mapman, thanks very much.

Obviously I don't have to finalize any decisions just now, and we'll see how things develop in the coming weeks. But while I certainly value the experience-based inputs from Drewan and Psag, and while it's certainly clear that realizing the full potential of DEQX requires an essentially anechoic measurement, what doesn't seem clear (and probably can't be, given how many application-specific variables are involved), is the degree of compromise that will result in any given situation from doing the measurement indoors.

Obviously Drewan and Psag are strong advocates of outdoor measurement. On the other hand, though, in this post by Forrestc, who also seems very experienced, indoor measurement is described as "by no means a deal breaker." And in Kal's (Kr4's) review in Stereophile the speakers he calibrated on his own, and I presume also the other pair he used, which were calibrated remotely by DEQX, were done indoors. The pair he did himself, with good results, were done with the impulse response truncated at only 5.5 ms after the direct sound arrival, and with the correction performed down to 200 and 150 Hz in the two profiles he created, with the latter even being slightly preferred!

Perhaps one relevant variable influencing the degree of compromise resulting from indoor measurement, btw, is how much correction is needed by the particular speakers that are involved. In that regard I've noted that the impulse and step responses I've measured on my speakers, during the first few tenths of a millisecond or so and with no panels near them or the mic, seem to me to look pretty good. Relative, that is, to the step response plots I've seen JA present in Stereophile in conjunction with reviews of other floor-standing speakers which do not use first order crossovers.

So we shall see. Thanks again for your inputs.

Best regards,
-- Al

I'd love to hear other folks POV on the cutoff frequency that worked best for their speaker calibration.

I can only report my own experience and with music playing, it sounds totally believable from the outdoor measurements. Using the same settings from calibration to configuration with the best indoor readings I could achieve, music and especially mid-bass had a slight hollow-nasal quality to it and was not as natural

I am using Open baffle speakers which I appreciate are very different to those being used by Al, Bruce etc but this quality was also present in the full range Shaninians when comparisons were originally made

I feel at a loss to convey with words just how close to perfect a well set up DEQX enabled system can get. For sure there are still going to be a lot of very satisfied users provided measurements are taken to the optimum in the environment available

For sure there are still going to be a lot of very satisfied users provided measurements are taken to the optimum in the environment available
Drewan77

the fact that anechoic or outdoor measurements is the only way to get the best out of the DEQX has to be considered a (big) down-side to this piece of software. The people at DEQX are obviously smart (since they've come up with this clever DEQX box). At the same time don't they realize that audio gear is almost always very heavy esp. speakers? They've got to realize that 99% of people will simply not have the opportunity to take their gear outside or to an anechoic chamber for many reasons. This, then, would create a sub-optimum DEQX setup & would eventually count against DEQX in the long run. It's also going to be a (big) deterrent for many others reading this thread & realizing that there's no way to get the best from or the most natural sound from DEQX unless they carry their gear outdoors/anechoic chamber...
In my books this is a major ding against DEQX.

I'm sorry to say that I don't quite agree with that last sentiment Bombaywalla. Unless someone has heard this themselves, they may not understand how good the resulting sound can be from a good indoor measurement and the majority of people will be extremely satisfied with that

Its a bit like saying that someone buys a top-range sports car but only drives it to 60% of its speed-handling capability. Another owns the same car but takes it to track days at a local circuit. Who is to say which owner gets the most pleasure?

DEQXs' main selling point is the ability to tame the room/speaker interface and it does that better than anything else I have experienced - we are talking about degrees of perfection here and each user will have different expectations

I mentioned a slight nasal quality to mid bass and by 'slight' I really do mean that. Many people probably wouldn't even notice or worry about it. I have listened to two other European DEQX setups, both sounded amazing and the owners were very pleased. Neither sounded quite as smooth or natural as mine does....to MY ears and MY tastes, which is the point I am trying to make

Happen to agree with Andrew's last post. Let's be patient while Al noodles his way in setting up his HDP-5. I surmise Al will be able to put this issue into perspective.

Almarg. Quick question. Do you have a maths or philosophy background?

Ptss, no, my background is in EE, although way back when I certainly had my share of math courses, and a few that touched on philosophy. I also have a law degree, although I haven't practiced as such.

Best regards,
-- Al

DEQX is a lot of time and expense. The whole point of going through that is to get correct output from one's transducers. That requires outdoor meaurement. Without correct setup, I personally don't think its worth the effort.

Drewan77,
OK. thanks for the clarification. So, we are talking degrees of perfection here & not something that blatantly wrong when doing an indoor correction.
And, judging by your last post, it seems that if one of us listened in your room with your indoor correction, we, not knowing your system, might not even be able to tell the slight nasal quality to the mid-bass. You are aware of this since you have done an A/B comparison many times. "Slight" is a fuzzy term but I'll take your word that it's hardly perceptible & maybe only if you point it out to the listener.

Bombaywalla - Without re-reading my earliest posts, I believe I may have mentioned my reaction from the very first time I played the DEQX corrected system. I swore out loud - it was that good compared to what I was familiar with. That was from the initial (indoor) measurement

Over extended listening I noticed the slight nasal quality and after re-running the measurements outside I was able to eradicate this. I expect a first time listener may not notice that, or more likely, others may not be as critical as I am

Psag, good to note that I'm not the only thinking along those lines......

It's important to realize that you do not have to use the speaker correction functionality (the part of the DSP that is best with measurements taken outside).

The DEQX has other functions - digital pre-amp, digital crossover and room correction that make it great even without the speaker correction.

The better the speakers the less improvement from speaker correction (as the drivers will be closer to flat and better pair matched).

With speakers like YG or ATC the improvements from speaker correction are small (but still noticeable).

The sound quality of the DEQX is good enough without speaker correction that I think it stands up as an exceptional product even without turning on the speaker correction.

Thanks Al. I enjoy and appreciate your posts :) In 20's I took a degree in accounting. No math; just use of an adding machine. I enjoyed Philosophy and logic and appreciate yours. KUTGW. Cheers :) Pete

P.S. Al. Dad was a civil engineer--great guy, unbelievable memory. Gave me a wonderful start and although passed in the early 90's is with me near daily. My luck.

Thanks very much, Pete, for the nice words and the interesting comments.

An update: I've created and assessed three more speaker calibration profiles, this time based on the measurements I took with no acoustic panels in place. (As I had previously described, the visibly cleanest and most reflection-free measurements had been the ones taken with panels surrounding the measurement microphone, but I found that very early arriving reflections from the panels themselves caused significant differences in the calibration profiles for the two speakers, which worsened in proportion to the duration of the truncation window. The same held true for the measurements taken with panels surrounding the speakers, to a slightly lesser degree but coupled with increased pickup of room reflections. Recall, btw, that I did not have the panels in precisely the same positions when I measured the two speakers, which fortuitously led to me discover the significance of the early arriving panel reflections).

Also, I should mention that when I performed the measurements even though I had pillows and a folded back (double thickness) Persian rug on the floor between the speaker and the mic, the waveforms captured by DEQX for all of the measurements clearly show a significant floor reflection (as can be determined based on its arrival time, beginning a little under 3 ms after the direct sound arrival). There is also evidence of a ceiling reflection arriving a little under 8 ms after the direct sound arrival, although it appears likely to consist mainly of low frequencies that I'm not addressing in the speaker calibrations.

Although all three of the new profiles sounded reasonably good, ultimately I was not satisfied with any of them. Most notably on classical solo piano, where the presentation had a slightly mechanical quality, and a slight loss of definition in the mid-treble, that were not present in bypass mode.

Given all of that, what I've decided to do is to order a third double-section acoustic panel and then re-do the speaker measurements. This time I will place one panel up against the fireplace you can see along the left wall in my system description photos; one panel up against the antique radio/phono console on the right; and one panel on the floor between the mic and the speaker being measured (positioned once again in the center of the room). In my circumstances it is reflections from the sides and the floor, and possibly the ceiling, that appear to be the main concerns. I believe that moving the speaker being measured to the center of the room gets them far enough away from the front and rear walls to allow those reflections to be windowed out without significant compromise to the calibrations.

Apologies for the slow progress to those who may be awaiting the conclusions of this adventure. I haven't even begun to address room correction yet. But from my perspective the slow progress has not been bothersome, as what I have in bypass mode and with one or two of the correction profiles is already better than what I had previously (which in turn I was pretty satisfied with). And it's been an interesting learning experience.

Best regards,
-- Al

Thanks for the update Al. I've been offline since Tuesday/Wednesday and haven't been tracking your progress. I looking forward to reading your future reports.

As you know, I already shared with you via a PM Larry Owen's general philosophical comments about speaker and room correction. I sent a copy to Nyal as well.

Al ... I intend to send you a PM with some room measurements and maybe some pics too if I can figure out to work my cell phone camera. I'm not sure I buy into the point made by Larry and PJ that my speakers and sub are too big for my room. I think my room is so crappy that it could mess up speakers of any size or quality.

BUT, the DEQX tamed my rotten room situation so that is more tolerable. In fact my stepson came in from out of town this weekend to spend father's day with me and played one of his favorite LPs. He was pretty WOW'ed (sp?). He hadn't heard my rig since the first set up attempt.

Cheers,

BIF

Yes, thanks for the updates Al. In your most recent round of speaker calibrations, where did you cut off in the low frequencies?

And in general, I'm curious what cutoff everyone made in the bass and how you arrived at that frequency...

Addendum to my last post ... it occurred to me that there was another factor that may have impressed my stepson other than the DEQX. Namely, since his last visit, I sprung for the SE upgrade to my ARC Ref 150 amp. As many may know, it involved switching out the KT-120 tubes for KT-150 tubes, plus ARC made some proprietary circuit changes. Now I'm not sure.

But what the heck ... my rig sounds better than before and that's what counts.

Bruce, yes, thanks for sharing these things with me. I'll look forward to the measurements and/or pics, in part because I'm curious as to what kind of room configuration they would consider to be too small for your speakers.

Roscoe, so far I've tried 7 different speaker calibrations, based on my initial set of measurements (which I will be re-doing from scratch as described above). The lower frequency limits I've used in those calibrations have ranged from 300 to 600 Hz, depending on where the truncation window was terminated.

Nyal had advised that I start out very conservatively with respect to that parameter, even as high as 900 Hz if the end of the truncation window would have to be as close as 5 ms after the direct sound arrival (with other rule of thumb combinations being suggested such as 600 Hz/10 ms, and 350-400 Hz/15 ms, if the truncation window could be extended to those points without encompassing major reflections). Those are obviously more conservative limits than the ones suggested in the manual, but he also suggested doing additional trials calibrating to progressively lower frequency limits, and trying to identify the point beyond which the sound starts to worsen.

In setting the limits I kept those rule of thumb guidelines in mind, while also, as I created each calibration, going back and forth between the screen on which the truncation window is set, and the following screen which depicts the resulting frequency response. In doing that I tried to set the lower frequency limit of the calibration above the frequency at which significant differences started to become apparent in the frequency response plot as I varied the duration of the truncation window.

Also, at the other end of the spectrum Nyal had advised that I should avoid monkeying very much with the speaker's natural rolloff at high frequencies. And in a separate conversation I recently had with Alan Langford of DEQX, (regarding an unrelated matter involving a very minor quirk I had noticed and reported in the operation of the touchscreen that is provided on the HDP-5, about which they were extremely responsive and will be resolving shortly with a couple of changes the user can easily incorporate, mainly a firmware update), he suggested limiting the high frequency limit of speaker calibration to 10 kHz. Given also that my particular speakers have a rise of a few db between 10 and 20 kHz, according to the DEQX measurements, followed by a rolloff above 20 kHz, I certainly plan to follow their advice on the subsequent calibrations. Although the ones I've done so far have had various limits ranging from 10 to 23 kHz.

As you'll realize from my previous recent posts, I can't really say much at this point from my listening experiences as to which of those limits (both at the low end and at the high end) work best with my speakers, because the anomalies caused by non-optimal placement of the acoustic panels when I did the initial measurements affected the middle frequencies and mid-treble too greatly for those other limits to matter very much.

BTW, during the course of the conversation with Mr. Langford he indicated that as a general rule of thumb outdoor calibration often tends to be less necessary for box-type speakers than for other kinds.

As for my status at this point, I've just received the third acoustic panel I ordered the other day, but most of this week I'll probably be too tied up with various family and other obligations to perform the next set of measurements. Hopefully I'll get them done within about a week.

Best regards,
-- Al

Many thanks for that great explanation and for passing along the recs you have gotten from experts on this matter. One thing I'd like some clarification on:

You say: "In doing that I tried to set the lower frequency limit of the calibration above the frequency at which significant differences started to become apparent in the frequency response plot as I varied the duration of the truncation window."

What did these "significant differences" look like. What should we be keeping an eye out for?

Good question, Roscoe, as I should have clarified that statement further.

If I position the window cursor close to the direct sound arrival, say within 3 ms or so to cite an extreme example, and then look at the frequency response on the next screen, there will be a downtrend in the frequency response below something like 500 Hz, roughly speaking. Presumably that occurs because the short duration of the window doesn't make it possible to sufficiently capture low frequency information. (Consider that 3 ms is less than one cycle of all frequencies that are below 1/0.003 = 333 Hz).

If the window cursor is then moved way out, to say 20 ms or so, the frequency response shown on the next screen will show a substantial rise in bass response at many low frequencies, with perhaps a narrow dip or two at certain frequencies.

Intuitively it seemed to me to make sense to set the lower frequency limit of the calibration around the inflection point below which that decrease or increase in bass response starts to occur for the chosen window duration.

This is all consistent with a comment Nyal had made to me that a common mistake is to correct to too low a frequency relative to the duration of the truncation window, the result being an excessive bass boost.

And consistent with various statements in the calibration manual, the subsequent room corrections should be a more suitable means of addressing the bass region, or at least most of it.

Best regards,
-- Al

Many thanks as always, Al.

Interim update: The plan I previously mentioned to re-measure my speakers has been delayed a bit, in part because last week a sudden and particularly violent thunderstorm resulted in damage to the power supply of my HDP-5. But to make a short story shorter, DEQX responded in an incredibly prompt and supportive manner, and I was back in business within a few days.

I now expect that I'll have time to perform the measurements sometime next week.

Kudos to DEQX!

Best regards,
-- Al