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Zippy is a Busy Boy.... - Page 3  

post #61 of 179
Quote:
Originally Posted by cjwhitehouse
Bosso,

I exchange e-mails with Bruce Hall fairly regularly so I know they took the problem on board. Curt acknowedged that the cancellation issue had been addressed in the v2.2.0 software update here . So the problem was genuine. ;)

To be fair, when we tested the 1812, we loaded a beta version of v2.1 software into it in the field (on the instruction of Bruce himself) and tested it exactly how we found it. I'm guessing here but I think the problem may have come about because in version 2.0 they allowed the LPC to be set to 'OFF' and prior to v2.1, the 1812 had its own software version. I suspect that they hadn't specifically tested the 1812 with version 2.1 and the 1812 did not cater for the OFF setting properly which then led to the apparent cancellation problem. Pure supposition on my part.

I would like to re-test the 1812 with the new software. I just need to persuade the UK importer to get hold of another example for me to test as he sold the previous demonstrator that he had! How inconsiderate! :p
I appreciate the heads up, my friend.

If you find yourself in possession of an 1812 to retest, please give us yanks a heads up. I, for one am very interested in the outcome. :)

BTW, I have used your sub test results as a reference many, many times. A gigantic hats off to ya for sharing the info! :cool:

Bosso
post #62 of 179
Quote:
Originally Posted by cjwhitehouse
Presenting the weighted relative level of each harmonic as an equivalent % takes a certain amount of trying to get your head round. :confused:

I was impressed that he tried to incorporate the distortion weighted CEA guidelines though judging from many of the posts here and at other sites that weighting was not appreciated or overlooked by many readers. In fact most posters did not appreciate that they were weighted despite the description. A better way to have presented the information would have been to actually graph the CEA step function so readers could see from the graph if measured THD was in "offensive" territory or not.

The IMD tests are not very meaningful as he lacks the proper equipment and the two-tone test as conducted is likely catching other distortions including THD. Without a Klippel Analyser ( very expensive I know) it would be near impossible to isolate the modulation components using Illka's methodology. It's not that simple since subs with high excursion drivers will usually have greater amounts of non-linearities to contend with, some non-linearities incapable of being measured directly using his procedures. One cannot conclude that subs with low THD have low IMD since despite his attempt its unclear whether THD has been removed from the test results.

The inclusion of the spectral contamination charts may be useful in helping identify other non-linear effects as well and its good to see those charts in his analysis.
post #63 of 179
Quote:
I was impressed that he tried to incorporate the distortion weighted CEA guidelines though judging from many of the posts here and at other sites that weighting was not appreciated or overlooked by many readers. In fact most posters did not appreciate that they were weighted despite the description.
Yeah, the first reaction is that something's quite wrong. I was impressed/surprized by the inclusion, also.

Quote:
A better way to have presented the information would have been to actually graph the CEA step function so readers could see from the graph if measured THD was in "offensive" territory or not.
That'd be cool.

Quote:
The inclusion of the spectral contamination charts may be useful in helping identify other non-linear effects as well and its good to see those charts in his analysis.
As I mentioned, it'd be interesting to try and correlate the SC data with subs for which we already have listening testimony to see what it reveals. Especially with models that tend to be on opposite sides of the subjective musicality opinion fence, it'd be fun to see how much of this apparent signature is obvious from the SC charts.
post #64 of 179
Quote:
Originally Posted by Jack Gilvey
Yeah, the first reaction is that something's quite wrong. I was impressed/surprized by the inclusion, also.
My apologies for having erred on this. Several guys on the Hsu forum were talking about some of the huge distortion numbers which were present in some of the subs. There was, at the time, no English explanation of what the H2, H3 ... etal ... numbers meant... it looked as if it was raw data, not a % of the corresponding THD numbers.

It would have been nice to have had the info regarding what those numbers meant before the test, but it certainly is useful information.

Quote:
Originally Posted by jackgilvey
As I mentioned, it'd be interesting to try and correlate the SC data with subs for which we already have listening testimony to see what it reveals. Especially with models that tend to be on opposite sides of the subjective musicality opinion fence, it'd be fun to see how much of this apparent signature is obvious from the SC charts.
Simple ... let's arrange for a blind listening test using the players in this test. Have the listeners post results on each subwoofer, then look at the graphs.

Jack, it is clear that you want to ridicule prior listening tests done by others. Rather than do that, Why not show the courage of your convictions, and agree to attend a blind test ? You would be a welcome addition ... :)
post #65 of 179
Quote:
Originally Posted by Jack Gilvey
As I mentioned, it'd be interesting to try and correlate the SC data with subs for which we already have listening testimony to see what it reveals. Especially with models that tend to be on opposite sides of the subjective musicality opinion fence, it'd be fun to see how much of this apparent signature is obvious from the SC charts.
That correlation would add significantly to the discussion and narrow the seemingly irreconcilable gap between subjective and objective observations. Traditional measurements have not been that helpful in explaining how some subs which look good on paper are not as highly regarded in listening tests and visa-versa. By way of comparison, the SD test avoids many of the limitations inherent in measuring 10% THD and the problem with exposing all intermodulation and cross modulation artifacts using two-tone IMD tests.

The spectral contamination measurements are far more useful indicators of cross modulation products excited by multifrequency signals. Single tone based tests and sweeps are at best rough proxies of real world listening situations. Having said that I thought using the Fibonnacci multiplier to identify ten stimulus frequencies between 20 and 77HZ was quite useful, though I suspect using tones below 30hz would have biased the results between sealed and ported subs. Given the limitations of the equipment, perhaps starting the series from 30hz and opting for higher frequency tones outside of the useable band would give better comparative results.


In any event, measurements derived from multifrequency tones or CEA type one third octave bursts should align better with real world listening and it would be neat to see the tests refined to use multi-tone bursts. This SD test is really the highlight of the measurements and Illka should be commended for going in this direction.
post #66 of 179
The information has been there all along, Ilkka posted the explanation thread before he posted the results. Real men do not read the instructions ;)

But am I the only one worrying about if the testing methodologies are moving further and further from real world usage? Avtalk recently upped the sweep time to 14 seconds, and now Ilkka has topped that with a 30 second sweep. Neither 14 or 30 second long sweeps resemble anything that you will find in music or movies, so how then can we then use the results to portray what we can expect to hear when listening to music or movies?
post #67 of 179
Quote:
Originally Posted by ManicMiner
The information has been there all along, Ilkka posted the explanation thread before he posted the results. Real men do not read the instructions ;)

But am I the only one worrying about if the testing methodologies are moving further and further from real world usage? Avtalk recently upped the sweep time to 14 seconds, and now Ilkka has topped that with a 30 second sweep. Neither 14 or 30 second long sweeps resemble anything that you will find in music or movies, so how then can we then use the results to portray what we can expect to hear when listening to music or movies?
You raise a good point. Part of the problem has to do with limitations with the equipment being used. Extending sweep time does help but will only get you so far in replicating real listening. Most of the lierature on the subject tends to be moving in favour of multi-tone frequency bursts rather than single tones or sweeps as far better approximators of real world conditions.
post #68 of 179
To me this seems as if...., I'll use a car analogy, we all love them: If you were to measure the acceleration of the new Ferrari FXX, but it turned out to be so fast that your equipment couldn't keep up with it. But then all of a sudden a bright head gets an idea, let's hook it up to a trailer and fill the trailer with 4 tons of stone! That should slow it down enough so that we could get an accurate measurement.

And accurate it is, the only problem is that now you have measured the acceleration of a Ferrari FXX hauling 4 tons of stone :) And this was not the original intention
post #69 of 179
Manic ... No, you are not the only one concerned about how these tests are going further away from real world usage. There is not a disc in existence which plays bass like these tests require a subwoofer to do.

I did finally find where Ilkka's explanation was posted on DVD Plaza. As all we were provided was a link to the review, I had no idea there was another thread with the specifics ... but, as it is there, can we move along ?

THIS is some good info ... in regards to the Distortion elements ...

Quote:
Originally Posted by Ilkka'sH2-6
the masking effect of the human ear will tend to make higher order nonlinearities more audible than lower order ones. CEA 2010 standard suggests limits for different order harmonics as follows (below fundamental level): 2nd -10 dB; 3rd -15 dB; 4th and 5th -20 dB; 6th – 8th -30 dB; 9th and above -40 dB. Naturally these limits can be â€reversed†and used for already measured results like I did. Meaning for example the level of 6th harmonic was raised by 30 dB. Those levels can be also modified as allowable THD %: 2nd 32%; 3rd 18%; 4th and 5th 10%; 6th – 8th 3%; 9th and above 1%. Meaning 3% 6th order harmonic will sound as â€bad†and will be as audible as 32% second order harmonic. Keep this in mind when looking at the results.
post #70 of 179
Quote:
That correlation would add significantly to the discussion and narrow the seemingly irreconcilable gap between subjective and objective observations. Traditional measurements have not been that helpful in explaining how some subs which look good on paper are not as highly regarded in listening tests and visa-versa. By way of comparison, the SD test avoids many of the limitations inherent in measuring 10% THD and the problem with exposing all intermodulation and cross modulation artifacts using two-tone IMD tests.
And since we've already got listening and objective data on some subs, it might be possible to show a trend toward the sonic signatures ascribed to the tested subs if present.
post #71 of 179
Quote:
Originally Posted by ManicMiner
To me this seems as if...., I'll use a car analogy, we all love them: If you were to measure the acceleration of the new Ferrari FXX, but it turned out to be so fast that your equipment couldn't keep up with it. But then all of a sudden a bright head gets an idea, let's hook it up to a trailer and fill the trailer with 4 tons of stone! That should slow it down enough so that we could get an accurate measurement.

And accurate it is, the only problem is that now you have measured the acceleration of a Ferrari FXX hauling 4 tons of stone :) And this was not the original intention
Nice. ;)
post #72 of 179
The first acronym I learned in frequenting forums was RTFM ;) I took that to heart and have done so since, so I did indeed read Ilkka's specifics before jumping into the test results.

It was then obvious that the THD numbers should be read with a different scale in mind, but since it was the SC graphs that attracted me the most, I could easily see that the PB10 and the EP 600 are nearly identical graphs, except for a hump of activity from 35Hz to 52ishHz from the Axiom that's missing in the SVS as well as some slight differences at and above the standard crossover point.

(Maybe we can persuade Ilkka to do a sidebar of SC graphs of an EP 500 and PB Ultra and revisit the G2G descriptives. It would be interesting in the very least, IMO. :eek: )

This has led me to begin thinking that maybe the SC graphs should be done with a 60Hz, 80Hz and 100Hz (or some similar group of pre-selected corners that represent the most used crossover points) LP digital 4th order filter applied.

In any case, I've already begun a SC comparo folder and thanks very much to Ilkka for the data :) :cool:

I agree that the slow sine sweep is not only not an indication of a DUT in real world use, I would instruct that my subwoofer not be subjected to the test at all.

From everything I've read and corresponded on the subject, I think Siegfried's shaped tone bursts (Yates used them in his now famous shootout, WDD) are the closest thing available to use for compression/max output testing (as well as spectral decay and other possible tests).

A quote from an interview by Stereophile mag with Siegfried:

Quote:
One final attribute of the shaped tone burst that I find very important is that it's a particularly safe signal with which to test the maximum output of components. For instance, if you use a burst rate of 1Hz with a 5-cycle burst you'll have a very low duty-cycle, so even if you require 100 watts to clip your tweeter, the short duration of the burst -- it's essentially like a frequency specific pulse -- will prevent you from overheating the voice-coil and damaging the driver.
Bosso
post #73 of 179
Quote:
It was then obvious that the THD numbers should be read with a different scale in mind, but since it was the SC graphs that attracted me the most, I could easily see that the PB10 and the EP 600 are nearly identical graphs, except for a hump of activity from 35Hz to 52ishHz from the Axiom that's missing in the SVS as well as some slight differences at and above the standard crossover point.
That's what stood out to me with those two graphs, that the PB10 looked cleaner in the middle range. Given the subjective accounts of the two, especially in the upper musical range, it'd be interesting to explore that.

Quote:
(Maybe we can persuade Ilkka to do a sidebar of SC graphs of an EP 500 and PB Ultra and revisit the G2G descriptives. It would be interesting in the very least, IMO. )
Indeed. We've a plethora of descriptives already on the books, what's needed is data to try and correlate the various suggested indicators (GD, IMD, SC, etc.) with them. For some, we have both, so it seems a good place to start.
post #74 of 179
Is there anything we can do to get Ilkka back on this forum? I find it a tad unfruitful discussing the results without having him around.
post #75 of 179
Thread Starter 
Quote:
Originally Posted by ManicMiner
Is there anything we can do to get Ilkka back on this forum?
Write to your congressman :D
post #76 of 179
Quote:
Originally Posted by ManicMiner
Is there anything we can do to get Ilkka back on this forum? I find it a tad unfruitful discussing the results without having him around.
Start a poll. Maybe that'll get some consideration, maybe.
post #77 of 179
Quote:
Originally Posted by ManicMiner
Is there anything we can do to get Ilkka back on this forum? I find it a tad unfruitful discussing the results without having him around.
I couldn't agree more. Ilkka has come a long way and with strong recommendation from the likes of Sir Edward, he's certainly an asset to these discussions, IMO.

Dozens of subwoofers in a single session with added tests that are not available through any other venue is simply remarkable. Add to that, commentary from the horse's mouth and how ya gonna beat that?...You ain't. :)

If we can't persuade Bott to reinstate, maybe we can persuade Ilkka to open a thread at HTF...

Bosso
post #78 of 179
post #79 of 179
Quote:
I couldn't agree more. Ilkka has come a long way and with strong recommendation from the likes of Sir Edward, he's certainly an asset to these discussions, IMO. If we can't persuade Bott to reinstate, maybe we can persuade Ilkka to open a thread at HTF...
I'm not so sure if Bott relaxed his position that Ilkka would follow suit?..it certainly would be nice though. You know whats wrong with trying again, it's something we all have to. Whats that called?..Do unto others as you want? no thats not it..Do unto others as they deserve!..no something still seems off. Whatever it is, I put my vote in the ballot box to see br Ilkka reinstated.
post #80 of 179
Quote:
Originally Posted by jakeman
The IMD tests are not very meaningful as he lacks the proper equipment and the two-tone test as conducted is likely catching other distortions including THD. Without a Klippel Analyser ( very expensive I know) it would be near impossible to isolate the modulation components using Illka's methodology. It's not that simple since subs with high excursion drivers will usually have greater amounts of non-linearities to contend with, some non-linearities incapable of being measured directly using his procedures. One cannot conclude that subs with low THD have low IMD since despite his attempt its unclear whether THD has been removed from the test results.
I'm keen to learn here. Can you give us some reasons why the Klippel Analyser would be better suited to isolating and measuring modulation components than Ilkka's method?

Without Ilkka being able to respond here himself, it is more than a little churlish to start questioning his methods. So I will restrict myself to a few observations regarding his latest tests and some of the reactions here to them.

Firstly, I am a little concerned that he has pushed a number of these subs into very serious compression. When I test a sub, I generally stop when power compression exceeds 3dB unless I am sure that the sub's limiter can handle it. So far I have had no "casualties" but I am always mindful that many of the subs I test are the property of private individuals. They have the ultimate veto on how far we go. Testing to destruction is not something I would recommend. Hence some of our maximum outputs do not reflect absolute maximum output levels. Measurements of distortion products where they go off the scale are of limited value anyway, I feel.

The IMD tests are interesting, but the problem with measuring IMD in the subwoofer range is that the restricted frequency range available to us means that IMD and HD components do tend to end up overlapping. This seems unavoidable. We need to see more examples to be able to draw any meaningful conclusions as to whether high HD and high IMD do in fact correlate.

As others have noted, the spectral contamination tests do look to be the most interesting innovation he has introduced. But when it comes to any comparison to real-world signals, individual sine wave frequencies separated by a Fibonacci ratio would not correspond with any kind of music that I am familiar with or would ever wish to be. :p

None of these test signals we are using closely mirror any real-world signals that a typical subwoofer would be expected to reproduce. Shaped tone bursts are just another artificial signal. Very short tone-bursts are problematic to record while still maintaining adequate signal-to-noise ratio. Longer sine wave sweeps allow better S/N ratio and accuracy in the results. We used a longer sweep for reverse sine sweep testing at AV:Talk because it was a requirement of the software we are using (WinMLS) to extract the harmonic distortion components from the resulting impulse response while still retaining adequate S/N ratio.

If Ilkka were to plot his harmonic distortion by component and overlay it with the CEA stepped limit thresholds, he would have had to plot separate spectra for each of the 1/3 octave frequencies he chose to plot. That's 7 graphs as opposed to 1. Bandwidth on the hosting site is not limitless.

Since we are on the topic of the CEA-2010 standard, I am slightly puzzled as to why some people seem to think this will advance the state of knowledge very much. As far as I can see, the standard only requires test results to be stated in terms of 2 numbers: maximum SPL in the low bass and ultra-low bass region. There is no requirement to show the underlying graphs or the actual limiting-factor in each case. In the absence of any other published information from manufacturers, this might just be a small step forward. But as a replacement for some of the measurements that reviewers are trying to give you (for free in the case of Ilkka and myself, I might add!) I doubt that it will really give you more insight into the performance of any given sub. :confused:

While the SC plots are interesting, what is very hard to glean from them is what correlation they have to what sounds good. While it is possible to say that the absence of visible "mush" in the output between the original drive frequencies should correlate with "cleaner" reproduction, where there is such mush present, it is impossible to say whether it would sound objectionable or even be perceived at all without doing a lot of corresponding listening tests. :cool:
post #81 of 179
That Hometheatreshack forum seems like a laid back place, I think I'll register over there. "If Muhammed can't come to the mountain, etc. etc...."
post #82 of 179
post #83 of 179
Thread Starter 
The Tests thread is everywhere - Reminds me of the “wandering soul†who can’t get back home :D
post #84 of 179
i doubt very seriously that Ilkka is losing sleep over not being reinstated here; this is not his "home", not by a long shot...he is sharing the results in many forums because many people have asked him to; I know of at least 2 forums were he was asked to put the results for others to see (look at his post count on such forums).

I personally agree with the others: he should be reinstated. The personal battles have come and gone, and hopefully those days are over. He brings a tremendous amount of experience and detail in his tests, and as Bosso said, if Ed is backing him up unconditionally, that in itself speaks volumes. I for one have found him to be a very knowledgeable young man, and a very bright one...

I'm very happy to see that he is also incorporating some of CEA's 1/3 octave bursts...this is really a great start in the right direction. This is exciting news, and his reports on the subs tested are very enlightening.
post #85 of 179
There was a major opportunity missed in this test. It would have been much more informative to have had just the current production models blind tested for about 1/2 hour each. Have the guys who brought the subwoofers do the listening, and post those results.

This is not a knock on Ilkka in any way, but is anyone going to seriously look at the PA sub, or the DIY subs, from this test ? The SVS 12.1 is no longer available ... and the PB10 has been tested to death. The Rel subs were already known to be boutique items, and the Genelec over priced.

Quite frankly, a shootout format with the 25-31+, BK Monolith, PB12-Plus/2 12.3, The Axiom EP-600 and the Hsu VTF-3 Mark II would have been a GREAT 5 way shootout, with real world, high value subwoofers.

Then take Ilkka's numbers ... and see how they stacked up against the listening tests, on that day, with the identical units.

As it stands, we don't have a clue what, if anything, the numbers posted can tell us about the actual listening performance and experience. Bummer ... :(

Hopefully, In the future, Ilkka will consider less quantity of subwoofers, with a more thorough test of each.
post #86 of 179
Craig, I’m afraid that you are talking to a wall here. Ilkka is just one of several engineer types who are so caught up in the science of audio that they have delegated the qualitative evaluation of audio equipment to a computer rather than their own listening experience. They seem to have forgotten the real reason for all of this interesting technology, listening to music and watching and hearing movies. If there is another use for an AV system I’d be interested in what that might be.

I will say, as you have continually said, that there is a great deal of value to a consistent and reliable test methodology for loudspeakers. We are fortunate that dedicated individuals like Ilkka put in the time to produce this interesting data. But the data alone is not what I am looking for in a “report†on the performance of a speaker. I want to hear what the person(s) heard, how it sounded to them and why. This subjective data is just as important to me as a computer measurement of a loudspeaker. One does not eliminate the need for the other, they are complimentary.

When I read a review in one of the trade rags I pay attention to the subjective part of the review. For me, it is the most interesting aspect of a review. Craig, your listening tests and the participant’s opinions have told me more about the performance of a subwoofer than any set of graphs ever will.

Oh, and may God bless America! :)
post #87 of 179
Quote:
But the data alone is not what I am looking for in a “report†on the performance of a speaker. I want to hear what the person(s) heard, how it sounded to them and why. This subjective data is just as important to me as a computer measurement of a loudspeaker
Measurements = objective
Impressions = subjective

If I wanted subjective impressions, I'd listen to the subwoofers myself, not take somebody else's word. There is much broader value in objective measurements.
post #88 of 179
Quote:
Originally Posted by SteveCallas
Measurements = objective
Impressions = subjective

If I wanted subjective impressions, I'd listen to the subwoofers myself, not take somebody else's word. There is much broader value in objective measurements.
Measurements are as objective as the national press. They are numbers which mean nothing, until we assign subjective values to them. If you don't believe this, take any one graph, outside of SPL and frequency response, and tell us what the importance is in relation to sound.

As with all other intelligent questions, this will also go unanswered by the so called "smart guys".
post #89 of 179
Quote:
Originally Posted by Einari
If I remember correctly Ilkka was banned from avs. I don't know if he has been unbanned, but I have't seen him post here since.
Wow, it has been awhile.
post #90 of 179
Quote:
Originally Posted by craigsub
Measurements are as objective as the national press. They are numbers which mean nothing, until we assign subjective values to them. If you don't believe this, take any one graph, outside of SPL and frequency response, and tell us what the importance is in relation to sound.

As with all other intelligent questions, this will also go unanswered by the so called "smart guys".
Craig, when you EQ your DD-18, do you look at the on-screen graph or just use your ears?

Personally, I find there are more productive things to do than shout at a stuck record. :D
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