Andrew (Drewan77) & Bombaywalla, thanks for your kind comments. And Bruce (Bifwynne), thanks for the suggestion about putting pillows on the floor for the speaker measurements. That is also suggested in the manual, and I'm planning to do it. I should have some time tomorrow to start playing with measurements, although I suspect I won't have anything meaningful to report for a few days or more. Regarding the manual, for my HDP-5 the 38 page user manual and the 143 page calibration ("installers") manual were on the calibration software CD. Similar if slightly earlier versions of those manuals can be downloaded from the DEQX site. (Click on the "owners" tab near the top of the home page, then "upgrades," and then scroll to the bottom of the page that appears). I printed out the manuals, 3-hole punched them, and put them in a loose-leaf binder, which for lengthy documents such as these I find preferable to viewing a pdf on a computer (unless I want to use the pdf reader's "find" function to look for a specific term). Content-wise, IMO the manuals are informative and reasonably well done. (Perhaps it was a different story some years ago when Psag and other long-term users purchased their units). Although the online session I had with Nyal Mellor was certainly a valuable supplement, in part because of suggestions he made that were in the direction of greater conservatism in the corrections than the calibration manual would seem to suggest. Bruce, a question for you: When the DEQXpert people calibrated your speakers, how far did they end up placing the microphone from them? And if you know, how many milliseconds after the direct sound arrivals did they place the point at which subsequent arrivals were windowed out? The reason I ask relates to the relatively large physical spacing between some of your drivers, which based on pictures I've seen I suspect is around 3 feet between the lowest of the four woofers and the tweeter. On my speakers, also, the two woofers are a significant distance (about 15 inches) above and below the two tweeters, which in turn are about at listening height. The reason I started thinking about that is it occurs to me that the greater the physical separation between drivers, the greater the distance should be between the speakers and the measurement microphone, which in turn (assuming the speakers are not measured outdoors) will necessitate shortening the duration of the measurement window (prior to arrival of the first reflections), which in turn will raise the minimum frequency that should be corrected and/or reduce the accuracy of the corrections. The reason I'm envisioning for that is not related to off-axis dispersion of the drivers, since the mic is placed at the level of the drivers which presumably have the narrowest dispersion (i.e., the tweeters). What I'm envisioning is that with the mic placed at tweeter level, the closer it is to the speaker the greater the difference will be between the distance from mic to tweeter and from mic to other drivers. And if the drivers are widely spaced, the amount of that path length difference will be significantly different than the difference between those path lengths as they exist at the listening position, due to the shallower angle between those drivers as viewed from the listening position. In other words, it seems to me that if drivers are spaced relatively widely, and the mic is not moved correspondingly further away from the speakers during the speaker calibration process (with the downside of shortening the "window," and hence the accuracy and/or low frequency extension of the corrections), the speakers may be corrected for a timing error that won't exist at the listening position. I've done some geometric calculations for the 15 inch distance between the woofers and the tweeters on my speakers. At a 4 foot measurement distance the path length differential between the distances of the mic to the tweeters and the woofers is 0.18 feet. At my 11.5 foot listening distance that differential is only 0.06 feet. The difference between those differences is 0.12 feet, corresponding to a propagation delay at the speed of sound of about 0.11 ms (milliseconds). Which would seem to mean that the DEQX will correct for a 0.11 ms timing error that won't exist at the listening position, if my speakers are measured at a distance of 4 feet, and a somewhat larger error than that in the case of your speakers. The planes of the baffles on my speakers, btw, are such that the woofers are mounted a little forward of the tweeters and mid-ranges, presumably to help with time alignment. But that is unrelated to the point I am describing. Also, to provide a bit of perspective on a 0.11 ms timing error, that would be readily perceivable on the step response graphs JA provides with his speaker measurements in Stereophile, those graphs having a time scale of 1 ms per major division. One of the purposes of those graphs being to provide some idea of the time coherence or lack thereof of the speaker. Apologies for the long-windedness of this post, but I hope it is clear, and that is the background for my question about the measurement distance the DEQXperts chose to use with your speakers. Best regards, -- Al |
I originally made a number of indoor measurements & the closest I managed to the result outdoor was by lifting the speakers onto a small table in the centre of the room so the driver set was roughly equidistant between floor and ceiling with the mic about 3' away and centred between the drivers but slightly higher towards the tweeter (which will be in line with your head during normal listening). Place the speaker at the extreme front edge of the table surface, even better if you have something the same width as your speaker to minimise reflections. Place as much soft material as is practical on the floor between speakers and mic, ie a mattress if possible or several sun lounger cushions etc. You will not completely kill the floor reflections and there will be some from the ceiling but it does help The measurement should show a point where reflections become apparent (very clear and distant outdoors but much less so in a room) and where the truncation can be made. For me, no matter how good an indoor measurement, the resulting calibration never managed to lose a slightly unnatural or hollow sound. Measurements outdoors, although a massive PITA, is so much more accurate if everything is done properly. Patience really pays off with DEQX - if you are inquisitive, make several attempts, take advice from Nyal and with experimentation it will be worth it in the end. You have the flagship processor so make the most of it and good luck! |
The reason I ask relates to the relatively large physical spacing between some of your drivers, which based on pictures I've seen I suspect is around 3 feet between the lowest of the four woofers and the tweeter. On my speakers, also, the two woofers are a significant distance (about 15 inches) above and below the two tweeters, which in turn are about at listening height.I understand what you are getting at, Almarg. These exact considerations are important when we are setting up a time-coherent loudspeaker in a listening room - the distance of the listening position relative to the driver plane is important such that the drivers integrate at the listening position to avoid a separate-tweeter-separate-woofer effect. I know that Green Mtn Audio had a heck of a time with the review magazines who never did understand the concept & almost always put the mic at the tweeter level & to their self-created dismay found that the drivers did not integrate & that the time-coherent speaker was not what the manuf advertised!! I understand that it took an enormous amt of effort on Green Mtn Audio's part to educate the reviewer. That's why if you look at the measurements in Stereophile of any Green Mtn Audio measurements they look terrible - they were mostly all done incorrectly! But the effect was devasting to the business, as you can imagine. So, I agree that you would need to push the mic further away based on the driver vertical separation BUT you run the risk of measuring reflected sound as well. I suppose that's why the manual recommends mattresses/cushions/blankets in between the mic & speaker. Maybe what's better is using some room reflection treatment material like the Owen Corning 703/705 sheets? A royal PITA but maybe worth the effort esp. if outdoor measurements are a no-go for you? I suppose you are shortening the measurement window to avoid catching the reflected sound? It's a trade-off (like all of engineering!! ;-)) In your calc - the error is 3:1 - 0.18' at the measuring distance & 0.06' at your listening position. that's a pretty big error looking at it in absolute terms but... Maybe that's not much of an issue? If I understand this correctly, the human ear cannot tell an echo (reflected sound) if the reflected sound is less than 1/15 of a second (& 0.11mS is much less than that) but, as Drewan77 stated, you could end up with a "hollow" sound if you measure indoors due to partial reflections. I also suppose that measuring outdoors is better because you have a perfect absorption environment - no echoes.... |
Al, sorry I didn't respond last night to your message. My internet was down until after 11pm. You asked: "When the DEQXpert people calibrated your speakers, how far did they end up placing the microphone from them?" My recollection was about 36 inches as measured from the tweeter. "And if you know, how many milliseconds after the direct sound arrivals did they place the point at which subsequent arrivals were windowed out?' Don't remember ... sorry. Al, what I do remember is that Larry, the DEXPert, asked me to take precise measurements of the speaker height, including the space between the drivers. In addition, Larry asked me to take precise room H,L and W measurements, including the distance the speakers were placed from the front wall and the distance my listening position was from the back wall. He also asked to me to position the mic at the precise spot of my ears. No kidding!! Please keep us informed of your progress. And have fun!! :) |
He also asked to me to position the mic at the precise spot of my ears. No kidding!!yup, no kidding! this is where you found the drivers to integrate best & the DEQXpert leveraged off that info to make the measurements. Any closer & you would have had the similar timing errors that Almarg wrote about. Makes sense.... |
Bruce previously sent me his files and Larry windowed at 24ms and 98% smoothing. My own outdoor measurements are windowed at 26ms & 0% smoothing because measuring 'anechoically', the plots are clear and have almost no reflections or impulses other than the speaker itself - it's an almost flat line until a clear and tiny reflection at 26.2ms which repeats every 3ms until fading away at 36ms However the windowing I quote is based on reflections made by Bruces' setup and will be different for yours. To be safe, I would suggest you try to look for a clear smoothish area after the main impulse and before the first obvious reflection. However, that may be difficult with a somewhat confused indoor measurement |
Thanks everyone for the good responses. I guess part of the answer to the issue I described, about the possibility of correcting a non-problem in the case of large speakers that can't be measured from an optimal distance due to reflection constraints, is that under such conditions speaker corrections would (or at least should, per Nyal's (AcousticFrontier's) recommendations) be performed only at frequencies above the point where the woofer(s) are likely to be significantly rolled off. For example, the crossover point of the woofers in Bruce's (Bifwynne's) speakers are indicated as being at 230 Hz, with a 12 db/octave rolloff above that point. (I don't know what the corresponding figures are for my speakers, as they aren't published and haven't been measured as far as I am aware). Bombaywalla, thanks for your inputs as well. As you aptly stated, there are always tradeoffs. Re your last post, though, undoubtedly the measurement they had Bruce perform at the listening position was for room correction, not speaker correction, room correction generally being done with DEQX only at frequencies below around 200 Hz or so, where room effects predominate. Speaker correction, including time alignment, would have been performed at the 36 inch distance he mentioned, and only at higher frequencies as I indicated. On another note, would anyone have any comments on the possibility of surrounding the measurement microphone during the close-up speaker measurements with two of these (four panels total, surrounding the mic on three sides). Acoustic specs are here, and look impressive. Or, alternatively, a mic baffle such as this one, which is apparently made of the same material as the large panels. Best regards, -- Al |
@Al ... just an fyi. Maybe Drewan can weigh in a little, but my general recollection is that my room wreaked havoc up to 500 Hz. Plus, my speakers weren't all that flat north of 500 Hz. Another point. Larry basically cut the S8's woofers out of the picture. He used my subwoofer to do the heavy lifting below 120 Hz. Part of the problem related to the room for sure. But also, the mid and tweeter drivers are wired in reverse polarity as compared to the woofers. So he reversed the overall polarity of the signal and matched the time alignment of the mid and tweeter drivers with the subwoofer. The S8's woofers are only working from 120 Hz to about 230 Hz. The sub is picking up the load from 13 Hz to 120 Hz. That's why I described the DEQX as turning my signal into a pretzel in order to tame my system. Drewan, if you have my e mail address, send me a PM and I will send you the latest files which reflect Larry's most recent "fine tuning" adjustments that he did on December 4, 2014. Same offer to you Al. Bruce |
@Al ... just a final thought. You will soon learn how the designer of your speakers wired the cross over when you do the signal impulse test. As I mentioned, Paradigm reversed the polarity of the mid and tweeter drivers as compared to the woofer to achieve phase coherence at the cross over points. I'm sure Richard Vandersteen would cut his hands off before doing such a thing. |
Bruce previously sent me his files and Larry windowed at 24ms and 98% smoothing. My own outdoor measurements are windowed at 26ms & 0% smoothing because measuring 'anechoically', the plots are clear and have almost no reflections or impulses other than the speaker itself - it's an almost flat line until a clear and tiny reflection at 26.2ms which repeats every 3ms until fading away at 36ms However the windowing I quote is based on reflections made by Bruces' setup and will be different for yours. To be safe, I would suggest you try to look for a clear smoothish area after the main impulse and before the first obvious reflection. However, that may be difficult with a somewhat confused indoor measurement |
Apologies for the delay in response here guys as I am in Europe and there is obviously a time difference Answering the question about windowing - an indoor measurement is not as clear as one taken anechoically and those sent by Bruce are rather like that although it is not bad by any means. My own measurements are crystal clear, a strong main impulse followed by a virtually flat line with four 'tiny' fading reflections. What you are supposed to do is window just before the first apparent reflection (26ms vs 26.2ms in my case). Larry has windowed at 24ms although I see a fairly strong reflection at 19.6ms so this will be included in the calibration Regarding room correction - I may be lucky in that my music room has solid walls and floor and I am able to keep speakers and chair well away from walls using the so called 'golden formula'. Using two subs has also helped so that I need minimal room equalisation: max - 1.5dB at just 33.4hz & 36.7hz and further very slight equalisation below 219hz - bass is very tight, dynamic and uncoloured (much less eq than Larry has used in Bruces' room which is in a range of -3.7 to +4.1dB between 116hz and 1469hz) As for time alignment - I originally used DEQXperts from the manufacturers in Australia and also the Netherlands. They taught me a lot but I was never told to use unequal timing for main speakers which is what Larry has done (6.60ms LH main speaker, 6.68ms RH). Maybe it's something to do with Bruces' room or he is seated off centre? In any case time alignment needs to be checked by ear and I align the matched peaks of the subs to the first rise of the main speakers rather than the first impulse peak as Larry has done. I have listened to both arrangements and in my setup aligning to the rise rather than peak gives a natural and seamless bass response where I can clearly hear each instrument individually and especially the realistic 'growl' of a bass guitar from within the lowest frequencies And for Subs - yes it is good that they take over the lower frequencies so that all amps and driver sets have a narrower band to work with (ie cleaner, clearer), in my case at 100hz with a 48dB Linkwitz-Riley crossover. Larry has used 120hz, 24dB and Butterworth so this may be related to the combination of speakers and subs that Bruce uses. I found that my subs (Miller & Kreisel plus B&W) sound slightly unnatural if I crossover above 100hz and at below this, my Open Baffles lose some attack I must admit that I spent many months experimenting, taking advice, re calibrating and listening before I arrived at the optimum for my system so it all depends on how much time each of you can put into this. A DEQXpert (or another user like me) in a remote location can advise but only YOU know what you are listening to With that in mind, I will mail Bruce and look at his latest measurements as suggested. It's a shame that this forum does not permit embedded illustrations as I could explain this so much better by screenshots of our two setups Here to help if I can.... |
Well, hearing one vote in favor and none opposed I've decided to order the large acoustic panels I referenced in my previous post, for purposes of shielding the mic from reflections during the speaker calibration measurements. The one slight concern I've had about doing that is the possibility that the panels might in themselves cause some low level reflections, that would arrive at the mic a millisecond or two after the direct sound. But hopefully not, and even if that were to occur to some small degree I'm thinking it could probably be minimized by some re-positioning of the panels. And although I would normally be hesitant to spend $340 on something that may end up being used only once, I'm guessing that the investment will provide benefits that are essentially permanent. Andrew (Drewan77), thanks again for your always valuable perspectives. I find it interesting and somewhat surprising that they extended the window of Bruce's speaker calibration as far out as 24 ms (about 17 or 18 ms after the direct arrival), given that significant reflections occurred earlier. Makes me a bit less worried about the reflections I may end up with. Best regards, -- Al |
Andrew (Drewan) and Al ... do you think the reason that Larry, the DEQXPert, used such a "heavy hand" with corrections to my rig had more to do with the speakers or the room?? For example, any thoughts if I were to invest in a pair of Vandies which start out time aligned? Andrew ...going back to your point about doing time alignment corrections outside, how much improvement do you think I would achieve if my speakers were aligned that way? |
This reply is to Bruces' questions - From your measurements I would say you are already using very good speakers as the response is better than I managed to achieve in-room with my original Shahinians. I guess you used quite a lot of sound absorbtion material Investing in time aligned speakers is not really the issue as the DEQX algorythm has already time aligned all frequencies that the mic picked up from your exiting pair (including the reflections of course!) I think the 'heavy hand' probably results from a combination of: - In-room measurement reflections which are included in the subsequent calibration - A poor room or placement - Your inexperience with the room equalisation and reliance on either the auto-eq or Larry trying to set this, based on your comments over the 'phone I sent you a couple of emails with screenshots & a suggestion to experiment by starting with less room equalisation based on the lower frequency peaks you can see on the software, playing music which tends to excite room bass nodes and adjusting or adding further points on-the-fly. You won't do any harm and you will also learn a lot! The amount of equalisation Larry has used suggests either that your room is really challenging or that he was being guided by you by telephone & couldn't hear what was happening to adjust himself I actually found that once the speakers are properly time aligned and using a second sub in a different position then the need for room eq becomes almost irrelevant (but setup and time alignment using step responses with the second sub etc becomes more complex). Believe me, my room created all sorts of issues back in 2011 before I started out with this. There really are none now.... so it can be done Time Alignment outside - Looking at the screenshot of my speakers, you can see how the main impulse is sharp and fades away clearly and very fast to a flat line until the first tiny reflection at 26.2ms. The speakers are at the extreme front edge of a narrow platform, DEQX and amps are on another table many feet away to the side and the ground, 3' below the speakers is soft grass. I believe the tiny reflections are actually caused by the mic & stand because when I measured one of the subs at 3' and then 6", the same reflection appears much sooner on the closer measurement Andrew (note: when I say 3', I really mean 3.28 feet, ie 1 metre but as I am an older Brit, my generation is still a bit more American than European !) |
Bifwynne, Vandersteens are not only time-aligned, they are time-coherent which is the superset & what you want in the 1st place. If you decide to pull the trigger on Vandys, get the 5A or higher. They are expensive but the sonics will surpass your present-day speaker & more & make you forget about upgrading for a (long?) while. Do audition them in your home, if possible, before buying. I've heard the 5A at a dealer's & I was not disappointed. thanks. |
Bruce, the only thing I can add at this point to the good responses that have been provided to your questions is to mention that in contrast to speaker correction, DEQX allows you to perform room correction adjustments on the fly, in real time, by inserting and/or dragging adjustment points on the computer screen while you are looking at the measured frequency response plots on that screen and while you are listening. Which is a neat and I believe pretty much unique feature. You can also click a button which inverts the room correction curve, then insert and/or drag correction points so that the inverted curve lines up with the most significant peaks and dips in the measured frequency response ("most significant" based on the combination of magnitude and width), then re-invert the correction curve and assess it sonically. Also a neat feature. In doing that you would of course not want to risk messing up the real .mzd file that is in use. The manual describes a procedure for creating a duplicate file that can be played with, but it seems unnecessarily roundabout. I've found that a simpler procedure is to copy the .mzd file to a different folder, then change its name and copy it back to the original folder. Then double-click its icon to open it with the DEQX software, or else open the DEQX software first and use "file/open." When you're done you can then re-upload the original file to the DEQX, if you want to. Best, -- Al |
Just wanted to say that I have used the technique of building a "box" of acoustic panels around a speaker for in room measurements. I have a bunch of Realtraps HF (not the standard kind) I use for this, mostly because they have metal frames and so stay upright and don't mind being transported from place to place unlike regular resin hardened panels which are not fully wrapped on the back side with fabric. |
There is a much simpler way to create a duplicate or modified file: open your original file as normal in the software then immediately click 'save as' from 'File' on the menu bar (top LH corner) When the smaller window appears, simply change the file name and save. It will then create another identical .mzd file in all but name into the same root folder as the original Provided this file remains open while you modify or add anything, any further mods or saves will apply to this, not the original. My 'working' .mzd file was built up by multiple saves this way and eventually I went back and deleted all the older, no longer needed versions |
05-20-15: Bifwynne Hi Bifwynne, if you haven't already, you might want to read the following Vandersteen Seven loudspeaker review in the Speaker forum. Looks like a really good review by a user (not a reviewer) http://forum.audiogon.com/cgi-bin/fr.pl?cspkr&1431987937&&&/Vandersteen-Seven-Review |
Thanks Bombaywalla. The Vandy 7s are a non-starter for me. Too da*n expensive. Also, my basement/sound room isn't big enough ... not even for the 5As. The Quatro Wood CTs might be an option. Drewan thinks that the DEQX already time aligned my speakers. If so, any marginal improvement might be theoretical. My guess is that it might come down to the quality of the drivers. And Paradigm's Signature line uses very good quality innards. The tweeter uses a Be dome and the mid uses a Co/Al alloy cone. Both drivers are quick on the draw. I might try and arrange a trip this Summer to Verona and check out the Quatros at Johnny's place. He is also an ARC dealer and might be able to match up an ARC Ref amp with the Vandies. In the meantime, I'm thinking about the sound box idea that Al and Acousticfrontiers mentioned above. It might enable Larry, the DEQXPert, to do a better job with time aligning my speakers. Btw, you referred to "time alignment" and "time coherence." What is the difference between the two terms? |
Bruces' question: 'Btw, you referred to 'time alignment' and 'time coherence'. What is the difference between the two terms?" My explanation is a bit lengthy (as usual!) and I cover phase coherence as well. They are inter-related.... Simple answer... You time align speaker drivers or driver sets to each other to 'achieve' time coherence Now the detail... When everything starts and stops at exactly the same millisecond, such as a woofer & a tweeter or a main speaker & a sub, they are then moving in a time-coherent fashion (and are also phase-coherent) When the BEGINNING portion of each driver or speakers' pulse arrives at the listening chair microphone or listener ears at the same instant, these are time coherent speakers. I discovered a long time ago that on my system, using the DEQX viewer and the Step Response facility, time-aligning the START of the sub(s) pulse with the start of the main speaker pulse gives by far the most natural integration and bass response. Larry has aligned Bruces' sub peak with the first impulse peak of the main speakers and both appear to start at about the same time so it should be similarly so None of this can be relied on purely by measurement & the DEQX viewer alone however because, if you think about it, the impulse plots of any speaker or sub contains ALL the frequencies emitted by those drivers and the plot just shows one combined response against Amplitude/Milliseconds Sound waves travel at different wavelengths/speeds from the lowest/slowest to the highest/fastest frequencies so what you are aligning to is a subset of all. Rest assured however that DEQX DOES minutely time align all frequencies WITHIN any single speaker it measures. It's just the manual bit in adding subs or anything from a diffrent measurement that needs careful interpretation to achieve the goal of 'time coherence' That is why I have found it is best to use the plots as a guide and then fine-tune adjust by ear until 'perfect' but based on several room measurements and step responses in the viewer. It was pretty easy for me once I got to that spot because every piece of music I throw at my system sounds crisp and clear with no hint of bass bloom or a crossover Note: with a single full range speaker containing passive crossovers, or a 2-way, 3-way measured accurately at once (ie without requiring subs), then an appropriate DEQX processor will do everything for the user and it automatically becomes time and phase coherent. All that's left to do is basic room eq or maybe time align an unequally placed speaker pair Phase coherence means simply that the twin peaks and valleys of a test tone (such as created by DEQX during measurement), exactly line up at your ear. When those different waves also start and stop at the same time, you then have a speaker that is both phase AND time coherent While basic 'phase coherence' is often used when setting up subwoofers, particularly 'simple' AV home setups, a phase-coherent speaker/sub may not be time-coherent. I know that because before I purchased the HDP3, my M&K sub WAS phase coherent with the main speakers & in an ideal position but the result in the room was pretty annoying to say the least. It has never moved from that spot but since setting my system up as described, it has audibly 'disappeared' |
Andrew (Drewan77), thanks again for your always excellent inputs. A couple of minor clarifications to your post just above, if I may: Sound waves travel at different wavelengths/speeds from the lowest/slowest to the highest/fastest frequencies so what you are aligning to is a subset of all.Although the velocity of a sound wave in air does indeed vary as a function of frequency, as I understand it the amount of that variation is small enough to be negligible for practical purposes. See the graph near the lower right corner of this paper, where it can be seen that even under the worst case condition (0% humidity) a frequency of 10 Hz is less than 0.03% slower than a frequency of 20 kHz. At a listening distance of 3 meters, that would result in a propagation delay difference of less than 0.003 milliseconds between those two extremely different frequencies. With a single full range speaker containing passive crossovers, or a 2-way, 3-way measured accurately at once (ie without requiring subs), then an appropriate DEQX processor will do everything for the user and it automatically becomes time and phase coherent.But of course only to within a degree of accuracy and over a range of frequencies that are constrained by the duration of the correction window and by reflections that may be captured within that window. Thanks again, though, for another excellent post. Best regards, -- Al |
Al and Andrew (Drewan) ... if I was inclined to put together a non-reflective sound box, do you have any thoughts about the materials I should use? I wonder what speaker manufacturers use to damp sound reflections in box speakers?? Andrew, notwithstanding the imperfect initial set up of my speakers because I was not able to do the time alignment adjustments outside, imaging and soundstage are greatly improved over what I had before. In many ways, I was playing stereo through two different speakers because of room EQ problems. I think you have a sense of what I was dealing with by looking at Larry's adjustments. |
Acoustic panels are not one of my areas of expertise either, Bruce. But if you want to DIY at a low price, the suggestions Bombaywalla made earlier of Owens Corning 703 or 705 seem worth looking into. They can be ordered via Amazon, where lots of user comments and Q&A's are provided. Also, although at higher price points and not DIY, you may want to look into the suggestion Nyal made earlier of the HF versions of some of the RealTraps. The Clearsonic panels I ordered, btw, will be arriving here on Tuesday. I may not be able to report results until the following week, though, as I'll be occupied with other things during most of the coming week. Also, I've been envisioning that when I move the speakers toward the center of the room for the close-up measurements, in my particular room surrounding the mic with the panels is likely to be more beneficial than surrounding the speakers with them. But I may try it both ways. Best, -- Al |
Thanks Al and Andrew. Al, may I suggest that you take your initial time alignment measurements a third way ... a baseline measurement. That is, no panels at all. Reason: to see how significant room reflection impact is on the speaker impulse measurements. And conversely, the extent to which your sound box ameliorates room reflections. Your results will guide me on next steps. Thanks |
Btw, you referred to "time alignment" and "time coherence." What is the difference between the two terms?sorry, I got side-tracked with my other hobby - photography. Processing some pix from a recent air-show & looking into other lens. Darn! why did I have to choose photography + audio both money sinks!! Thanks for Drewan77 for taking the lead to answer. His reply is mostly correct. Almarg has addressed some clarifications already. Time alignment is when the speaker designer arranges the drivers in such a way that their acoustical centers are on the same vertical plane. You've seen this done a number of ways: sloped baffle (BTW, that was another great thread!) with the tweeter on top & woofer at the bottom because the tweeter's acoustical center is way in front of it & the woofer's in almost on the driver itself. 2nd way, is what Focal does - makes the front baffle curved. It's an arc of a very large diameter circle. If you put drivers on an arc the distance from each driver to the listener's ear is the same. The tweeter is not on the arc recessed just a wee bit to account for its forward acoustical center. 3rd way, which is what we've seen in Dynaudio's Confidence 5, where the tweeter is at the bottom & woofer on top. The linear distance from the bottom-most tweeter is longer than from the woofer & makes up for the forward acoustical center of the tweeter. Time-coherence is when a speaker introduces no delays to any frequency in the 20-20KHz range. No driver hence no speaker is linear from 20-20K so you'll see speakers that are time-coherent in the 200-8KHz or 10KHz range. A speaker will introduce a delay in the sound - it has to since it's a causal system but what I mean here is that the speaker does not introduce more/less delay at one freq vs. another. IOW, all freq are equally delayed thru the speaker. When this happens, the leading edge of the tweeter, mid, woofer all arrive at the ear at the same time, as Drewan77 already wrote. For a speaker to be time-coherent, it will be time-aligned & will also be phase-coherent. A time-aligned speaker is not necessarily time-coherent. Simple answer...No, this statement is not fully true. Time-aligning is just one thing to ensure time-coherence. And, it's a physical attribute of the speaker meaning you can see it/touch it. The other very important thing to ensure time-coherence is to use a 1st-order x-over such that the time-delays between any 2 freq & amongst all the freq is not disturbed at all. If you don't do this, time-aligning will have no meaning. When you go thru the math, 1st order x-over ckts are the only ckts that do not disturb the phase relationship amongst all the frequencies. Many speaker manuf tout their product to be phase coherent. Yes, they are BUT only at their x-over freq & a little +/- of that. This is easy to for a speaker manuf in the biz for any length of time. The key is to make the speaker phase coherent over the entire audio spectrum. This takes special skill & the use of 1st-order x-over ckts that inherently do not disturb the phase. Otherwise you end up compensating for the x-over & by the time you finish the entire x-over is complicated & destroys the music signal totally. Hope this clarifies.... Thanks. |
DEQX claim that their algorythm time aligns all frequencies within a given measured speaker, even if this is a 2 or 3 way, regardless of the crossover order or even physical placement of drivers on a flat or stepped baffle (measured at once - not so if a sub is then manually added for instance. That requires the manual 'best compromise' time alignment I have previously mentioned) Therefore it is my understanding that Bruces' speakers have been time and phase aligned during measurement and calibration - within the limits of the microphone and the accuracy of the measuring environment but including the inbuilt passive crossovers My reply relates to DEQX digital time alignment and not speakers that are physically aligned via the baffle and containing passive crossovers. Of course Bombaywalla is correct about that and the impact of the crossover order |
That's a great response Bombaywalla. So, in the absence of owning a speaker that is time coherent/aligned ... like mine which are NOT, the next best solution is DEQX. IMO, I think the DEQX really tamed my speakers and my room. One can drop all the money in the world into electronics, cables and so forth. But, IMO, I think time coherent/aligned speakers are the way to go ... PLUS, the room HAS TO BE RIGHT. My room sucks and I have no other options. The DEQX cleaned up a lot of my audio problems. Another question is driver distortion: harmonic and intermodular. I wonder if the DEQX fixes those issues too. I suspect not. As an fyi, the Magico S5 is one of the lowest harmonic distortion speakers I recall ever seeing tested. I don't recall seeing any speaker tester report on IM distortion. I wonder if it can be tested?? See this link: http://www.soundstage.com/index.php?option=com_content&view=article&id=1043:nrc-measurements-magico-s5-loudspeakers&catid=77:loudspeaker-measurements&Itemid=153 |
Al/Andrew/Bombaywalla ... any thoughts about the impact (if any) DEQX has on driver distortion? My guess is that driver distortion is more a function of crossover and driver design and build quality itself. And that it is outside the realm of the DEQX to correct such deficiencies. Just an fyi: Here's some bench test measurements of my Paradigm S8s (an earlier version #2): http://www.hometheaterhifi.com/surround-sound-speaker-systems/surround-sound-speaker-systems-reviews/a-secrets-speaker-system-review/page-4-the-paradigm-reference-signatures-on-the-bench.html Not bad ... at least in the opinion of the reviewer. My S8s (v3) use the same tweeter and mid drivers. The woofers and x-over were upgraded. Nevertheless, I assume the distortion specs would be about the same as those reported for the V2. Even still ... compare the Magico S5s in my post above. Almost vanishingly low distortion specs. I suppose the real Q is whether we can hear the difference. Stated differently, assuming the Magico S5 and Paradigm S8 were DEQX corrected, how differently would they actually sound? I gotta' believe that a 500 Hz test signal produced by the Magico sounds exactly like a 500 Hz test signal produced by the Paradigm S8. The real Q is how do the two speakers make music after being DEQX corrected??? |
Thank you for the kind works Bifwynne. Yes, correct - for those who cannot & will not buy time-coherent speakers DEQX is one answer to the problem. And, I believe the DEQX people were smart when they realized that the room acoustics play an imp part & they incl room correction as well. I think we can safely say that 99% of the people live in homes where the room sucks! Does that mean these people cannot have good sounding playback systems? No, they surely can with room correction - either passive (tube traps) or active (PARC, DEQX, Lingdorf, etc). Re. DEQX taking into account driver distortion - I think DEQX does that already. You put a mic in front of the speaker & measure. DEQX sees distortion. It does not itemize the distortion - X% from x-over, Y% from drivers, Z% from cabinet, A% from room. How does it know where the distortion is coming from? To it distortion is distortion. When it does a correction for the speaker is lumps all the distortion into one number & tries its best to fully correct it. Then, I believe, you go to the next step & do room correction with the mic at your listening position. And, this 2nd part takes out the other big contributor. So, as you are playing music, the driver is still distortion (as it always did) but the DEQX correction curve has an inverse function to straighten this out. So, I believe that driver distortion is included to whatever extent the measuring mic can pick-up & whatever is the correction capacity of DEQX. I'd be interested in others' comments too. Thanks. |
Hi Bruce, Here are the benefits of DEQX as summarized in the calibration software manual: Correcting full range passive (traditional Hi-Fi) speakers plus room correction:I'd imagine that the main benefit DEQX can provide with respect to driver distortion would be in cases where subs are being used (as in your case), or in biamped or triamped setups. In those situations DEQX could introduce very sharp filter slopes that would keep some of the drivers from having to deal with frequencies that are out of their comfort zone. And it could do that without the adverse timing and phase effects that would result if that were done in speaker crossovers or elsewhere in the analog domain. With a single-amped speaker that is being driven full-range, such as in my case, I'd imagine that any benefits to driver distortion would be incidental, due to relatively minor "second order" effects. An example perhaps being taming a frequency response peak in the bass region that is contributed to at that frequency by harmonic distortion of a lower frequency. Regarding Magico, as you've no doubt seen in various threads here and elsewhere, they tend to be controversial. While they seem to do pretty much everything right on paper, and a lot of folks love them, some find them to be unmusical. Also, the impedance characteristics of the S5 shown in the SoundStage measurements you linked to do not inspire confidence in their tube-friendliness. While their impedance magnitude is relatively flat across most of the spectrum, as you've mentioned in the past, it is around 3 ohms in a good part of the bass region, and that low magnitude is combined with a fairly severe -45 degree capacitive phase angle around 50 Hz. That said, though, I suspect that your amp could handle them better than most tube amps, due in part to their relatively low output impedance and their very substantial power supply. Best regards, -- Al |
Thanks again Al and Bombaywalla. More great responses from Al and Bombaywalla. Al, I think your quote about using the DEQX with active x-over function (and I assume this entails multi-amping) answers my driver distortion question: "High dynamic resolution (reduced distortion) due to drivers operating in linear operating zone. "Reduced crossover distortion - reduced comb filtering." But I think your following comment may say it all: "I'd imagine that the main benefit DEQX can provide with respect to driver distortion would be in cases where subs are being used (as in your case), or in biamped or triamped setups. In those situations DEQX could introduce very sharp filter slopes that would keep some of the drivers from having to deal with frequencies that are out of their comfort zone. And it could do that without the adverse timing and phase effects that would result if that were done in speaker crossovers or elsewhere in the analog domain." Al/Andrew/Bombaywalla: There is only one speaker that I know of that uses super high-order internal/passive x-overs; namely: Joseph Audio. I think Mr. Joseph describes his crossovers as an "infinite baffle" types or something to that effect. I'd call them brick wall filters. I bet the DEQX would do a great job with Joseph Audio speakers. As an fyi: PJ, the DEQX National Sales Manager chap I spoke about before is also the local rep for Joseph speakers. He speaks well of them. Next to last point ... as Al and Andrew both know, I use a self powered sub (1700 watts; 3400 watts peak) that Larry, the DEQXPert, folded into my system. I think Al makes a good point that using the sub diverts low frequency signal away from my main amp, thereby reducing the power demands placed on the amp. Last point ... I wonder out loud if I should even ponder upgrading my speakers at any time in the future. Perhaps, the best next big step, which would entail taking a whole different path, is to do what Andrew has done. Namely, DIY speakers with excellent drivers ... and no internal crossover. Instead, I would use the DEQX as the cross over and I would multi-amp each speaker. Very expensive path. I wonder if Duke LeJuene (sp?) from AudioKinesis could custom build the speakers. |
Bruce: I think Bombaywalla and Al have answered your question very well, DEQX corrects exactly what it hears but, as you also suggested, it is still a function of crossover, driver design and build quality, plus 'voicing' of the cabinet as well DEQX deals with distortion as long as the user is not trying to push a particular driver beyond what it is capable of or trying to over-compensate in the software. For instance, good as it is, DEQX is unlikely to provide distortion free 10hz bass from a 4" driver! When calibrating, the user must work intelligently with the measurement plots I can report from experience with 3 very different sets of speakers that the results sound surprisingly similar in the same room. In the case of the first two, very significantly improved over the same setups used previously without DEQX and in a similar setup to the one that Bruce has. The third, my current and final configuration now uses everything an HDP processor has to offer (6 way) except the DAC 1. Shahinian Obelisks including passive inbuilt crossover driven by one amp + one M&K sub (<120hz) 2. JBL stand mounts including passive inbuilt crossover driven by one amp + two M&K subs (<110hz) 3. Open baffle floorstanders, bi amped with two amps, treble crossed at 3100khz + one M&K and one B&W sub (<100hz) Smooth frequency response, clean, tight bass and musical clarity were very similar among all three setups. If there was a shared character, I would have to call it 'transparent and neutral' The Shaninians, probably by nature of their multiple 360 degree radiating mid & treble drivers had the poorest imaging and a more indstinct soundstage but with huge width and depth. Still fabulous sounding though The JBL setup imaged extremely well and had the sense of a neat but smaller 3D soundstage and encouraged me to then move on to, what I consider one of DEQX-HDPs greatest strengths - the ability to incorporate multiple amps and steep crossovers When not listening to my home system (or with my wife!), I am normally with like minded friends listening to live music and realistic transient attack had always been my goal because that is one area I had never been able to resolve, no matter what I listened to in dealers, at shows etc - until I heard another, OB based system with a DEQX processor in it. To achieve the necessary midrange speed/cleanness I decided that I wanted to avoid any sort of cabinet colouration so started researching Open Baffle Speakers myself I prototyped various designs for a long time before commissioning a CNC workshop to manufacture the frames for my final design: 1" thick Zebrano Bamboo floorstanders with a d'Appolito configuration of Aluminium/Magnesium midrange drivers and ribbon tweeters. Large, heavy speakers but exceptional transient speed with a real sense of musical reality...in fact unbelievably so on a lot of recordings One other comment about DEQX correcting 'what it hears' - I do have experience of comparing music corrected from an in-room and outdoor measurement of both the Shaninians and JBLs and although in theory the software should correct to the same resulting sound, it does not. My in-room measurements always resulted in a slightly unnatural, nasal hollowness to music playback and with my desire to achieve 'perfection' it wasn't quite good enough |
