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Re: DVDPlaza Subwoofer Tests Round 3

Oh er! I'm going to get through some cups of tea reading this one.

Thanks Ilkka

Russell
 

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Re: Another Face Off Thread

I want to give Illka proper credit for what I'm certain was a MAJOR undertaking. There is LOTS of very interesting data there. Definitely more information I'll add to my online "library."
 

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Elite Shackster
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Re: Another Face Off Thread

Mark Seaton said:
I want to give Illka proper credit for what I'm certain was a MAJOR undertaking. There is LOTS of very interesting data there. Definitely more information I'll add to my online "library."
Thanks Mark! I value your opinions/thoughts very much. If you have any suggestions or development ideas, I'm all ears. Hopefully we will see a certain dual 15" sub in our next session. :yes:

And yes, it was a major undertaking. The measurements itself didn't take more than two ~8 hour days, but sorting out the data the next 5 weeks. :blink:
 

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Re: Another Face Off Thread

The one suggestion for future testing might be to keep one subwoofer around as a constant to highlight any un-expected changes from test to test. It gives you a measuring stick by which to compare other tests or show where we should be cautious in comparing.

I also find the results with the multi-tone tests rather interesting. I will need some more time to read more carefully and digest all of the information, but one the spectral contamination tests do actually paint some pictures of measurable differences. The complication lies more in interpretation and what those measurements actually mean. I suspect as we have more samplings, trends will start to become more clear. An intresting example comparison is the 90 & 95dB measurements from the SVS PB12-Plus/2 in 20Hz with the 12.1 driver vs. the 12.3 driver. The spectral contamination tests do correlate to the fact that this same box design uses drivers having somewhat different characteristics.
 

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Re: DVDPlaza Subwoofer Tests Round 3

First off, thanks for doing all that work. I'm sure you're getting a lot of love thrown at you right now, but as one who's done similar (work related/non-AV) projects in the past, I know what a huge undertaking this can be. So here's some more 'love' -- Great work. :T

I've skimmed the results -- seriously reading and anylyzing the results will have to wait until later -- and noted that you left a post for your comments on the test of each sub. When do you think you might post those? I'd follow the rest of the conversations, but, well, I don't speak Finnish.

JCD
 

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Re: DVDPlaza Subwoofer Tests Round 3

Well Ilkka I do have a question. What happened to reverse sweeps? Do these test results just use the TrueRTA built-in (increasing freq) quick sweep for max SPL tests?

Bob
 

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Discussion Starter · #9 ·
Re: DVDPlaza Subwoofer Tests Round 3

bobgpsr said:
Well Ilkka I do have a question. What happened to reverse sweeps? Do these test results just use the TrueRTA built-in (increasing freq) quick sweep for max SPL tests?

Bob
Max output level and power compression

Maximum long term output level was measured using a 30 second sine sweep from 100 Hz to 10 Hz. First sweep was level matched at 90 dB at 50 Hz. Drive level was rised by 5 dB after each sweep. There was around 20 s delay between each sweep. Sweeps were taken up to the point where the output level stopped rising anymore (5 dB or more of compression). I also tried 2 dB as the last step, but usually it didn’t help. This is a very demanding test and the results should not be compared to other tests with faster sweeps etc. Power compression graph is showing the relative compression to the 90 dB sweep.
Reverse sweeps are exactly what I used also this time. I also did Quick Sweep, but its results weren't that much higher. I need to work something else for peak output tests.
 

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Re: DVDPlaza Subwoofer Tests Round 3

Ilkka,

By far the most appropriate way to do peak output tests is with the 1/3rd octave tone-bursts that Don Keele and Sigfried Linkwitz first put to use years ago. There is plenty of information on the web about the signals, but they are basically an enveloped sine wave of various filter types, typically 5-6 cycles long. I believe this is also what the new CEA testing is adopting for its stimulus. So far as actual limits, I would say both the limits defined by the CEA and simple audible thresholds would be quite useful. With these tones it is very easy to hear the onset of distortion and any resultant noises. If you look at the process Keith Yates used, he wrote down various observations (what he heard) alongside the numerical data.

To clarify about the reverse sweep signal, I am assuming it was a reverse log-sweep? The measurements appear to track what others have measured, but I am guessing you did loopback tests to confirm TrueRTA was reading the signal as flat, correct? I'm more asking to clarify for anyone reading along. ;)
 

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Discussion Starter · #11 ·
Re: DVDPlaza Subwoofer Tests Round 3

Mark Seaton said:
Ilkka,

By far the most appropriate way to do peak output tests is with the 1/3rd octave tone-bursts that Don Keele and Sigfried Linkwitz first put to use years ago. There is plenty of information on the web about the signals, but they are basically an enveloped sine wave of various filter types, typically 5-6 cycles long. I believe this is also what the new CEA testing is adopting for its stimulus. So far as actual limits, I would say both the limits defined by the CEA and simple audible thresholds would be quite useful. With these tones it is very easy to hear the onset of distortion and any resultant noises. If you look at the process Keith Yates used, he wrote down various observations (what he heard) alongside the numerical data.
Yes, this would probably be the best option, but it's PITA to measure. I mean it takes a lot more time than a 30 second sweep. It also requires much more attention since you have to carefully listen at the subs. If I could measure only a few subs in a day...but 27 in two days? :D

To clarify about the reverse sweep signal, I am assuming it was a reverse log-sweep? The measurements appear to track what others have measured, but I am guessing you did loopback tests to confirm TrueRTA was reading the signal as flat, correct? I'm more asking to clarify for anyone reading along. ;)
It was a reverse linear sweep. Log-sweep didn't work with the THD plotting, that's why linear. And of course I looped it, that's essential with TrueRTA. And actually it needs a trick or two to even get it flat.

And I believe my absolute SPL was pretty accurate too. If you look at the Genelec 7073A results, it scored ~106 dB at 20 Hz with ~2 dB of compression, exactly the same what Yates and AV Talk measured.
 

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Re: DVDPlaza Subwoofer Tests Round 3

Ilkka said:
Maximum long term output level was measured using a 30 second sine sweep from 100 Hz to 10 Hz.
...
Reverse sweeps are exactly what I used also this time. I also did Quick Sweep, but its results weren't that much higher. I need to work something else for peak output tests.
I do not know why I did not read reverse sweep from the 100 Hz to 10 Hz text. :blush:

But the tone burst and log vs linear discussion that ensued between you and Mark made my dumb question worthwhile. The idea to push the sub starting at its more efficient frequency response area first before the lower freqs where more voice coil heating occurs seems to me to be a good way to characterize a sub's true capabilities. Did not AV Talk also change to this general idea for their most recent tests?

Using tone bursts ("enveloped sine wave of various filter types, typically 5-6 cycles long") like Mark describes sounds like it would require a much more involved test setup. A remote controlled PC or IEEE-488 controlled waveform generator working with the measuring PC?

Bob
 

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Re: DVDPlaza Subwoofer Tests Round 3

Ilkka said:
Yes, this would probably be the best option, but it's PITA to measure. I mean it takes a lot more time than a 30 second sweep. It also requires much more attention since you have to carefully listen at the subs. If I could measure only a few subs in a day...but 27 in two days? :D
At least someone can appreciate what Keith Yates went through in his Way Down Deep report. Now remember that there were 2x that many subs since he also did a similar style report for Home Theater Magazine. Of course Keith's measurements were from 5 sets of measurements for each subwoofer on different days. Oh, and he did extensive listening tests as well! I remember him grumbling a lot and mentioning something about a perfect job for a college intern. ;)

I would think that someone would be able to write script that could look for a distortion threshold such as described by either the CEA standard or a 12dB/octave approximation of it. The system could then step through ISO center frequencies noting the highest level achieved and capture the spectrum.

Ilkka said:
It was a reverse linear sweep. Log-sweep didn't work with the THD plotting, that's why linear. And of course I looped it, that's essential with TrueRTA. And actually it needs a trick or two to even get it flat.
The TEF measurements Keith Yates and I use are in fact a linear sweept that can be set to sweep either direction. For subwoofers it is usually better to start high and sweep low. We should remember there are slight differences that will impact compression somewhat so far as how much time of the sweep is spent over various frequency ranges. I would expect that the shaping of the magnitude you had to do actually balances this out closer to that of a log-sweep for the TrueRTA to read flat.

Now that I look at the data again, I am curious what process you are using to measure THD? FYI, if you haven't checked out WinMLS before, I think it might be a good program for you to experiment with as well. Lars Morset, the creator of the program, is a very sharp guy. If you contact him he might also have some useful suggestions towards streamlining such a measurement process.

Ilkka said:
And I believe my absolute SPL was pretty accurate too. If you look at the Genelec 7073A results, it scored ~106 dB at 20 Hz with ~2 dB of compression, exactly the same what Yates and AV Talk measured.
Indeed, the data looks to largely follow the sort of performance I would expect from the various devices tested. Again, I can appreciate how much a PITA such an undertaking is. Great Job.
 

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Re: DVDPlaza Subwoofer Tests Round 3

Looks like any reference to this work over on another forum has been nuked...typical. I nominate this forum as the place for learned discussion since the mods will actually grasp what's being discussed.

I would think that someone would be able to write script that could look for a distortion threshold such as described by either the CEA standard or a 12dB/octave approximation of it.
I nominate Illka.

Edit...one thread is still there...for now.
 

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Discussion Starter · #15 · (Edited)
Re: DVDPlaza Subwoofer Tests Round 3

Jack Gilvey said:
Looks like any reference to this work over on another forum has been nuked...typical. I nominate this forum as the place for learned discussion since the mods will actually grasp what's being discussed.


I nominate Illka.

Edit...one thread is still there...for now.
Yeah, my second visit to AVS was pretty short... Now my both nicks are banned for forever. :rolleyesno:

Also www.avforums.com deleted my thread, since they don't allow linking to another forum.
 

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Re: DVDPlaza Subwoofer Tests Round 3

Hi Ilkka,

I think you'll find that the heavy SVS following on AVF were quite satisfied with the results - apart from the PB10 owners that is. I think it had been built up on the forum to be the only sub at it's price point. Beside that, I believe they have nothing but utter respect for your endeavours.

Russell
 

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Re: DVDPlaza Subwoofer Tests Round 3

Hi Ilkka,

I think you'll find most forums frown upon "linking" to other competing forums. You may get away with it more in the states because they(forum owners) probably won't consider a finnish forum much of a "threat" to steal members/viewers. A forum in the UK could think very differently though. How long would it take for you to start another thread at AVforums with all of your data...20-30 minutes? They have already invited you to post ALL of your data on their forum(you just can't post it on a RIVAL forum and use AVForums to generate more traffic for a competing forum..:)...so why even introduce the idea that there are "hidden motives" at play here? There is so much drama in the subwoofer world as it is...I don't see any need to invent it when it isn't there...

Tom V.
SVS
 

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Re: DVDPlaza Subwoofer Tests Round 3

I know we ain't the biggest game in town right now... but we are supporting you all we can. We definitely don't mind the links... several guys from that forum post here anyway and are a big part of our success thus far. I suspect AVF is probably a little upset that you wouldn't allow them to host the actual tests and it might be a backlash of sorts. I'm thinkin' AVS is getting some feedback from some of their advertisers.

Hey... you turned us down too... I suspose we'll have to delete your threads too, huh? heehee... :sarcastic:

You are always welcome to post the links here, but do remember the offer is open if you decide you want a forum for your tests and you want to moderate it... you can have it right here. I do think it would be nice to have a U.S. forum to post the tests results in addition to the Finnish forum.
 

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Discussion Starter · #19 · (Edited)
Re: DVDPlaza Subwoofer Tests Round 3

Tom Vodhanel said:
Hi Ilkka,

I think you'll find most forums frown upon "linking" to other competing forums. You may get away with it more in the states because they(forum owners) probably won't consider a finnish forum much of a "threat" to steal members/viewers. A forum in the UK could think very differently though. How long would it take for you to start another thread at AVforums with all of your data...20-30 minutes? They have already invited you to post ALL of your data on their forum(you just can't post it on a RIVAL forum and use AVForums to generate more traffic for a competing forum..:)...so why even introduce the idea that there are "hidden motives" at play here? There is so much drama in the subwoofer world as it is...I don't see any need to invent it when it isn't there...

Tom V.
SVS
I apologise my wording. It was not needed. I have edited my post accordingly.

I just can't understand how a 99.9% Finnish forum (they have one section for English speaking people) could be a threat to any English speaking forum? They can't read any post, they can't make posts or join in any conversations.

If forums don't allow linking to other forums (our DVDPlaza doesn't have any problems with that), that would basically mean that I would have to post my results on EVERY forum. If you have checked the subwoofer tests forum over at DVDPlaza, you will see that it's impossible to post that data on every forum. It can not be posted in one thread, it needs its own forum section. Yes, Sonnie has offered me my own section here, but what would it really help? This forum is very small (this thread has now 183 views, my DVDPlaza thread has around 47,000) and I couldn't link this site to (for example) AVForums etc.

Imo it's more professional to have the results posted only in one place. For example AV Talk doesn't post their results on any other forum than their own. That way I can better reply to questions and I don't have to follow multiple threads in multiple forums. I simply don't have time for more. I know it will limit the discussion and less people will see my results, but I have to draw the line to somewhere. Keep in mind that I don't get a single penny from these tests. Actually I have invested huge amounts of money for test gear etc. Not to mention hundreds of hours of work that it took to arrange the measurement session and sort out the results.

I'm sorry but the results will stay on DVDPlaza.
 

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Re: DVDPlaza Subwoofer Tests Round 3

Hi Ilkka,

Believe me, I can “feel your pain” in all of this subwoofer drama. I have seen you disparaged and called every name in the book by certain individuals. But now that “their” subwoofer did well in your latest test…these same folks are saying what a great guy you are..:)

Some of the SVS products you have measured did great, some just okay. We take all constructive criticism of our products very seriously and we value your measurements in helping us better all of our products. As we have been discussing in our private emails, I don’t always agree with *all* of your testing methods…but please don’t think of that as a major criticism or something unusual. I have disagreed with things Don Keele used to do, same with Keith Yates, John Johnson, ect. Tom Nousaine and I have had many debates on this very topic. And if you ever got all of those guys in the same room together...you can bet they would disagree on certain levels in this context(measuring bass) too..:)

When it comes to forums, you have to remember how expensive it is to keep a big forum running. The way they pay for that is with sponsors(ad banners). The more people that SEE the banners, the more people that click on the banners. The more people that click on the banners, the more money is generated for that forum(either directly or indirectly). So any large forum is not going to want to have their entire membership redirected to a COMPETING forum. Anyone going there(to the competing forum) is going to see different banners…and they will inevitably “click on” any banner that interests them. You can’t blame them…I would do the same. A lot of those banners will be in both English and Finnish(or have both finnish and English translations/websites for potential customers after you “click-thru”. So you are using one forum to generate income for a competing forum(or at least that is how some people will look at it).

Anyway, I hope to be able to finally look over your latest test sessions this weekend. Been too busy lately. Thanks for taking the time to provide all this data!

Tom V.
SVS
 
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