Krix Seismix 3 Mk2 Subwoofer review (3 Viewers)

[Craig Chase]

Jack and Ed ... A serious question. Would you expect then, based on the idea that one can tell from GP measurements, that the PB10-ISD, if two are used, will sound about the same as a single PB12-Ultra/2?

Max 20 Hz @ 2 meters from two PB10 's ... 100 dB
Max 20 Hz @ 2 meters from a single Ultra ... 103 dB

Max 25 Hz @ 2 meters from two PB10 's ... 108 dB
Max 25 Hz @ 2 meters from a single Ultra ... 106 dB

Those are some examples of measurements on the 2 products, rounded to the nearest dB, from Ed's tests.

If the numbers tell all, why spend more than the $858 for two PB10-ISD's ? EDIT ... This could sound like I was being argumentative, which is not the intent. This (to me, at least) is an interesting topic. On AVS a gent posted almost identical numbers for the Velo DD-12 and DPS-12 ... both were measured by Nousaine.

He asked the same thing, other than the EQ, why is the DD-12 $2999 and the DPS-12 $549 ?

 

[Thomas Dekany]

Let me correct you Craig - Fidel Castro

 

[Craig Chase]

Tom ... I WAS actually thinking about Fidel when I typed that ... but as we cannot even travel to Cuba from the states, I decided he did not count ... ... besides, I ALSO used "RARE" ...

 

[Thomas Dekany]

Fair enough

 

[steve nn]

I'd hate to meet up with some of you guys back in the Western days

Some of you guys would most likely make Simidy Sam look like a Poster Boy.

 

[Edward J M]

This one is easy.

Look at the dynamic output limits of the PB12-Ultra/2, as measured with the Quick Sweep: 115-119 dB. The dynamic output limit for the PB10-ISD is about 105 dB. So it would take four PB10-ISD to match the dynamic output limit of one PB12-Ultra/2.

Of course four PB10-ISD would also be lower in distortion while offering the same maximum output capability. If floor space, aesthetics, and set-up ease were not considerations (and they always are), a 2x2 stack of PB10-ISD's would be a lethal combination.

It's what I've been saying all along about the PB10-ISD - its dynamic output and 10% THD limits are closer to parity than any other SVS product I've tested. If you need more headroom, just buy two (or four).

You can use the DD-18 results from the WDD series as a parallel. The servo limited the DD-18 to a maximum of 93 dB @ 20 Hz @ 2 meters @ 5-10% THD (depending on the intended sweep level). And yet he was able to generate 102 dB @ 20 Hz @ 2 meters with a tone burst before the onset of "audible distortion". Clearly the sophisticated servo will allow transient bursts but will limit steady state output.

The Quick Sweep is so brief (especially in the 48 kHz sampling mode) that it truly does approach a tone burst in the 10-200 Hz region and is an excellent tool to measure the dynamic output capability. Rather than relying on audible distortion cues, I simply observe the FR for artifacts and anomalies (obvious on the PB12-Ultra/2 graphs) and call that level the dynamic output limit.

Look at the orange line in the 20 Hz tune for the PB12-Ultra/2 - about 115 dB @ 20 Hz @ 2 meters before the onset of dynamic compression. FWIW, this onset IS quite audible when it occurs, but I'd rather show it occuring on a graph than simply rely solely on audible cues.

There is a difference though between Yates' method and the Quick Sweep; he plays a tone burst at each frequency and listens for audible cues. In comparison, I simply run the Quick Sweep at progressively louder levels until the FR becomes non-linear. I am certain Yates' method for determining peak output and my method will yield different results; to what extent I am not certain.

Regards,

Ed

 

[Craig Chase]

Ed ... Excellent response, thanks ! A followup question.... Would you then say the Quick Sweep Dynamic output limits are a pretty good barometer for what we are actually hearing from normal use of a subwoofer ?

It appears the better ANY subwoofer has done in this test, the better it has sounded, for example, in the blind listening tests you have conducted...

 

[Edward J M]

For example, I stated in my review the PB10-ISD can be driven into dynamic compression, and this was also clearly reflected in the maximum clean SPL peaks I was able to measure on DVDs. However, if you stay within its dynamic output limits, the PB10-ISD sounds extremely good in all subjective respects. It's only a matter of time before someone stacks (2x2) four PB10-ISDs and cuts loose with what will be one of the best $1800 "single" subwoofers on the planet.

 

[Craig Chase]

Ed ... The picture is bcoming much clearer with each review you do. The Quick Sweep DOES show the big 5 ... what it does not show is how long the subwoofer CAN "hold" the high levels in the big five ...

SO ..... It would appear that, after looking at the Quick Sweep Dynamic Output Max (the point at which you note power compression beginning), the next parameter would be your 5 second sine waves for max SPL at each frequency ( ie.. 20, 25, 32 ... etc...)

There ARE occasions that the deep bass spectaculars last for several seconds, though most are much shorter.

The Velo excels at the shorter term stuff, but does seem to "hold back" when the signal lasts for several seconds ... which you noted in the differences in the short term pulse signals vs. longer term signals in the WDD test. The servo starts limiting the output...

Another example, on many discs, the STF-2 would match up well with the PB10, but throw, for example, the talking "King of the machines" scene from "Matrix:Revolutions" at both subs, and the PB-10, with its FAR higher longer term max SPL capacity in the deep stuff, will distance itself from the STF-2.

 

[Edward J M]

I would break down "The Big Five" in terms of tests in this manner:

1) Flat: Frequency response test, looking at the overall shape of the curve.

2) Deep: Frequency response test, looking specifically at the -3 dB roll-off point.

3) Clean: Distortion limited (10%) output at 1/3 octave intervals.

4) Linear: How linear is the distortion limited output across the entire pass band (the bandwidth linearity calculation).

5A) Loud: Short-term (dynamic burst) output limits (increased until FR becomes non-linear). Represents typical music and movie transients - a good indicator of "headroom" and "effortless bass".

5B) Loud: Longer term (30-60 second) power compression limits (increased until FR starts to compress due to thermal, limiter, or servo restrictions). A good indicator of how well the subwoofer will sustain output and accurately convey amplitude changes under sustained heavy DVD passages.


Didn't know you had an STF-2 for evaluation? I think what you are hearing here is a combination of tests #2 and #3. The PB10-ISD has more output below 25 Hz simply because the FR extends deeper, and the PB10-ISD also has higher clean (i.e., distortion limited) output capability, so you are also hearing a more accurate representation of the signal, with more of the fundamental notes and less of the distortion harmonics.

 

[Craig Chase]

Ed ... I actually had an STF-1 here ... and based on what I measured here, with it and the PB-10, the STF-2 falls in between them in dynamic power ... not surprising, with an 8 inch driver in the STF-1 vs. the 10 inch in the STF-2.

And the "Big Five" is definitely going to help a LOT of people read a review and truly get a feel for what the subwoofer can do.

The next question .. Could a point system be developed around the big five .. ???

 

[Edward J M]

Sure, but are you talking absolute performance scores, or weighted performance scores with price, overall size, weight, footprint, etc. as considerations?

 

[Craig Chase]

Ed ... I would think absolute scores. Price, size, weight, footprint .. etc... are all items which are easily found by the consumer. The type of information your are providing is not easily found.

For example ... The STF-2 had 102-103 dB dynamic compression thresholds from 25 Hz on up, where the Acoustic Visions MRS-10 had a 97 dB dynamic compression at 30 Hz , and finally the PB-10 had apppx 104 dB from 20 Hz and up ... scoring all three is doable on an outright scale ...

Of course, the PB12-Ultra/2 would be FAR superior to any of these ...

Also, once done, it would be easy (for a potential purchaser) to take the price of the product and divide it into the point score for a $$$$ per point ratio.

 

[Mark Seaton]

I would think such a scale would require many presumptions and assumptions which would eventually have to be re-adjusted.

We need to remember that these various factors are not absolute in any situation.

One obvious matter with #2 is that a single number very poorly represents the subjective low frequency capability. If we wanted quick numbers to reference the graph which is really needed, I would note the -3dB and -10dB points, as this gives you some insight into the nature of the roll-off. Then, depending on where these points fall in frequency you can determine what effect your confined space may have on the results you will observe in your room. There is also the factor that many listeners would be extremely happy with strong 22-25Hz extension, while looking at spectrographs posted in Keith's review or here on HTF would suggest that even 5Hz extension could prove useful. I know that when Tom Danley had to reproduce a sonic boom for NASA, the requirement was for reproduction to 5Hz... outside.

Realities of space and size make trade offs of extension and output a certainty. The question the brings up the question of what is better? More linear output with somewhat limited extension vs. deeper extension with lesser output?

There are many factors which effect individual subwoofer output requirements. Room size, location, acoustics, main speaker capability, setup varations, subwoofer overload characteristics, as well as good old listener preference all contribute to our decision of where we set and leave the volume.

On the matter of distortion, Linkwitz's tone bursts to audible limits like Keele and Keith Yates used in their tests are probably still the most accurate determinants of useful audible output limits when combined with differing length displays of compression. Earl Geddes has done preliminary testing which strongly suggests that a single THD number is not an all encompassing measure of percieved sound quality. Don't get me wrong, lower distortion is certainly something to strive for, but direct comparison of numbers will generally be most applicable with more similar systems where distortion and overload characteristics are more similar.

All of the factors under discussion more accurately make up a personality profile than any sort of all encompassing, absolute quality factor. Measurements are extremely useful in characterizing the qualities and capabilities of a subwoofer, and Ed's reviews look to be continuing what Keith had hoped might become more expected from future reviews. With Ed adding more products to his list, it will become progressively easier for readers to relate to his reviews. Ideally someone shopping for a subwoofer will be able to search out and listen to one or two of the subwoofers Ed has reviewed, which allows much more insight to the results he has documented with other products.

Best Regards,

 

[Craig Chase]

Mark (and all), There has never been a perfect system for defining absolute product performance for any venue ... cars, speakers, etc ...

But a system of SOME form would be quite valuable ... even if it is merely in chart form ... an expanded form of the old Nousaine Charts, for example.

Right now, a prospective subwoofer purchaser has no reference from which to choose.

It would take some time and effort, but as these are supposed to be support threads, it would seem a good idea to explore the creation of such a chart.

 

[Mark Seaton]

Hi Craig,

I wanted to drive home the reality of the multi-faceted characterization of a subwoofer's performance. Again, more advanced limiting and creative EQ/DSP make things even more complicated to compare. I do think we could come up with some form of numerical score for some of the aspects which could make for some easier comparison for users. Of course most magazines love to use scales which they only use the top 40%! I believe in a scale where a "perfect" score should only go to some very extreme performers while also putting the "adequate" performers at the bottom.

If you are going to do something of this sort, it should be numerically based. The largest complication comes from our hearing sensitivity and the convergence of equal loudness curves at low frequencies. In other words, while we may percieve a change of 80-90dB at 1kHz to be twice as loud, at 20Hz, 80-90dB of change is equivalent to an 80-100dB change at 1kHz. I believe a scale could be made useful, yet we need to remember that we cannot easily incorporate all factors in a single score.

Low frequency extension would seem fairly easy, as I would reference the score as a the inverse of a scale ranging from 5Hz to say 40Hz. This of course needs to be calculated with a log scale with say a 100 point range. List the score for the -3dB point as well as the -10dB point and I feel it would be useful. The problem here lies in what level the subwoofer is measured at. How exactly do you define this for something like a Sunfire, Velodyne DD, or even a Bag End. The response of a Bag End 18 will continually change above about 80dB 1w/1m. As there is no correct way to do this, I might suggest a nominal 90dB sweep which happens to be the approximate threshold of audibility at 15Hz.

For output capability measurements I would suggest a fairly agressive scale where a "decent" subwoofer might fall in the 50-60% range. If you considered 70dB as a zero point, and maybe 130dB as the top end of the scale, we could then put this to a 100 point scale based on % of the total 60dB range. What makes this a bit more useful is that doubling up on subwoofers gives you a low frequency gain of 10 points, making for rather simple comparisons. This also puts 100dB at a midpoint score of 50 and 118dB at a score of 80.

Hardly a perfect system, but it is a start to which someone could make recommendations from for various rooms and situations.

Further thoughts?

 

[Craig Chase]

Mark ... I think you have hit on a pretty good looking system here. For example, using Max SPL at 16, 20, 25, 31, and 40 Hz (@ one meter outside with < 10% THD)) ... 70 dB could score zero points, 130 dB could score 120 points ... with 2 points awarded for each dB above 70... for a possible total of 600 points. Of course, it would be impossible any sub I know of to hit the 600 points ...

The other criteria could also have a point system placed on each. Ed may want to hurt us for suggesting such a thing, though... this could be WORK ...

 

[Mark Seaton]

Actually, I was thinking 0 points for 70dB and 100 points for 130dB. Give a score for each frequency range. Since it works as a percentage of 60, a 6dB increase is 10 points higher. Of course this really is only of use to those who don't understand what the measurements and absolute levels mean by making the scale a little easier to understand, yet the ones who will probably read carefully enough to know what the numbers are referring to would understand what the normal numbers mean.

The low frequency scale can be a simple nlog(x) function adjusted for the range we are interested in. The idea was that the results could just be put in a spreadsheet with functions already entered. Of course to me the most telling graphs to me are still the slow sweeps at increasing levels, where I would prefer to see a range of 10-100Hz.

 

[Craig Chase]

Hey ... That works, too ...

 

[Edward J M]

That can be arranged.....what length would you prefer - 30 seconds? Forward or reverse? Intuitively, reverse would thermally load the VC before the nasty stuff hits - I wonder if the sub would perform differently forward vs. reverse?