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Discussion Starter · #1 ·
Does anyone know if the test was done outside, at 2 meters like Ed's tests?
 

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No, it was tested in JJ's lab. His neighborhood isn't the best for outdoor measurements - too much ambient noise and nearby reflective surfaces.
 

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I can't believe that he commended the EQ.


The before/after plots track quite closely, and leaving aside the null in the mid-50's, it does almost nothing to correct the nearly 10 dB response variation.
 

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Discussion Starter · #4 ·
Thanks Ed. But it was done at 2 meters?


Do you have an guesstimate as to which SVS that would give you the same SPL?
 

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Quote:
Originally Posted by ManicMiner
Thanks Ed. But it was done at 2 meters?


Do you have an guesstimate as to which SVS that would give you the same SPL?
He measured the in-room FR at the listening position, about 10 feet from the subwoofer. The 55 Hz null not withstanding, this graph clearly shows a rise in the response below 50 Hz, with the 25-35 Hz level being about 10 dB more than the rest of the pass band. We can't really tell how much of this bump is derived from calibration, room gain, or the native quasi-anechoic FR of the subwoofer.


I'm not sure at what distance he measured the maximum SPL - I'm assuming it was at the listening position. He pulled the sub away from the corners, so that may have an influence on the maximum SPL reading. And Sunfire does not list a distance or a room size; they simply state "116 dB peak with room gain".


He measured THD at 12" from the active driver or 12" from the PR, depending on the test frequency. There are so many variables between the two test environments, it wouldn't be possible for me to accurately extrapolate to other models - sorry.
 

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Discussion Starter · #6 ·
Thanks again Ed.


I was hoping that you had some experiences with the sub of your own, not that you could extrapolate the data, I guess that would take magic :)


But since I already have your attention I have one more question ;)


In the Velo SPL test the SPL1200 peaks at 116db at 1'. Based on that, could you say that it would do about 106db at 2 meters, and therefore just a tad more then the PB10?


Sorry about all the stupid questions, but I'm curious, and I'm trying piece together my own mental picture of the performance of some of the most common subs on the market. And I can not really find anything much on the SPL, and the small Velodyne DD subs
 

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Without question, AV Talk has the best compilation of test data (1/2 space at 2 meters) for Velodyne subwoofers. I would refer you there for further research.

http://www.avtalk.co.uk/forum/index....&SQ=1117485664


They tested the SPL800, the HGS10, and the CHT-10R.


For example, the SPL800 played at 86 dB @ 30 Hz @ 25% THD (the purple sweep line). You need to double the amount of existing subwoofer for a 6 dB increase in volume. So you would need about eight colocated SPL800s to play 30 Hz @ 104 dB at the same 25% distortion level:


2 SPL800 = 92 dB @ 30 HZ @ 25% THD

4 SPL800 = 98 dB @ 30 Hz @ 25% THD

8 SPL800 = 104 dB @ 30 Hz @ 25% THD


Moving higher in the pass band, the SPL800 measured 90 dB @ 40 Hz @ 10% THD (again using the purple sweep line).


Using the same method as above:


2 SPL800 = 96 dB @ 40 HZ @ 10% THD

4 SPL800 = 102 dB @ 40 Hz @ 10% THD

8 SPL800 = 108 dB @ 40 Hz @ 10% THD


While it's not the SPL1200, at least it gives you some frame of reference (within the same brand and family line-up) in which to operate and make comparisons to other products which were also measured in 1/2 space at 2 meters.
 

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Discussion Starter · #8 ·
I thought that you could add 6db for every meter you moved the mic closer to the sub, and therefore could subtract 6db for the first meter, and 4db for the last two feet? Guess I'm missing something :)


When buying a subwoofer I usually find some candidates within a given pricerange, and the next thing I do is to try and find out how loud, and how deep can they go. I know that subwoofers are about more than that, but i think that you first need to find a sub that plays loud and deep enough for your liking before you start focusing on other qualities.


Few manufacturers provide SPL numbers, and judging by the accuracy of the frequency numbers some of them provide it is just as well.


Thats why tests like yours, avtalks and others become so important when buying a sub. The only problem I have with the Avtalk tests is that they test SPL in 5db intervals instead of testing the maximum SPL for a given frequency, so that a sub that could do 104db ends up looking no better then a sub that could do 100. Other then that it's top notch.


But I'm looking forward to part 3 of the test, and hope they will test some of the smaller Velodyne DD subs, and also some SVS PB subs.


Is it correct that you are doing a test of the PB12 Plus sometime soon, think I read it in some post somewhere?
 

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Discussion Starter · #9 ·
I see one other way of guesstimating the SPL 1200II's output at 31.5hz.


Take Tom Nousaines measurement of 93db at 32hz for the SPL-R 800, and add the 6db difference between the SPL800II and 1200II from John E Johnsons test=99db at 31.5hz?


i'm also guessing that the max SPL measurements done by John E Johnson was done with THD above 10%?


Feel free to to call me dumbass, and offer me a swift kick to the ass :)
 

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Quote:
I thought that you could add 6db for every meter you moved the mic closer to the sub, and therefore could subtract 6db for the first meter, and 4db for the last two feet? Guess I'm missing something
I wasn't trying to compensate for the mic distance. I was simply illustrating how many units it would take for a given subwoofer to achieve a higher sound pressure level at the same test distance, frequency, and distortion level.


AVTalk and I both test in 1/2 space at 2 meters - except I go to the center of the enclosure and they measure to the face, which can create a small disparity depending on enclosure depth. So a comparison between anything I have tested, and anything AVTalk has tested, can be done with a relative degree of confidence.


While I woudn't expect us to be exactly the same on each product tested, we should (after compensating for the slight difference in test distance) be within 2-3 dB, which is a reasonable tolerance considering we use different test rigs and software packages.


Again, small differences aside, this test environment can give you a very good frame of reference in which to compare the relative performance of subwoofers. For example, under the same test conditions, the DD18 played 40 Hz @ 108 dB @ 4% THD, which is an outstanding performance (red curve).


As discussed above, it would take eight SPL800s to play 40 Hz @ 108 dB @ 10% THD. So even eight SPL800s couldn't quite keep up with a single DD18 at 40 Hz. It's just one way of illustrating the relative performance differences in distortion limited output between products tested under the same conditions.

http://www.avtalk.co.uk/forum/index....&SQ=1123952414
 

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Quote:
Originally Posted by Ed Mullen
Without question, AV Talk has the best compilation of test data (1/2 space at 2 meters) for Velodyne subwoofers. I would refer you there for further research.
As well they should, being OWNED by Velodyne! BIASED. :rolleyes:
 

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Discussion Starter · #12 ·
I think I found the simplest solution of them all, I measured my own PB10 at 1 foot and 31.5hz and got 118db. ;)


One question Ed about measuring subs outside. Since the mic is placed in front of the sub, will it not favor subs that are either closed, or have the port in the front?


What I'm getting at is: When inside there will be surfaces to reflect ports that are facing backwards, so that the subs who have backward facing ports will maybe gain more db's from beeing measured inside, compared to the closed subs.


This maybe be a stupid idea, because I had it just now :)
 

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Quote:
Originally Posted by ManicMiner
I see one other way of guesstimating the SPL 1200II's output at 31.5hz.


Take Tom Nousaines measurement of 93db at 32hz for the SPL-R 800, and add the 6db difference between the SPL800II and 1200II from John E Johnsons test=99db at 31.5hz?


i'm also guessing that the max SPL measurements done by John E Johnson was done with THD above 10%?


Feel free to to call me dumbass, and offer me a swift kick to the ass :)
I'll do neither, but I will state that TN measures a 2 meters indoors (7500 ft3 room) and uses a 10% THD limit and allows SPL to vary.


JJ usually uses a 100 dB test volume and allows distortion to vary, and JJ doesn't usually measure at 2 meters.


You cannot compare these two data sets, they are too different for any reasonable extrapolations.


If you want to determine how well the SPL1200 does (relative to the other products AVTalk or I have tested), you would be better off taking the AVTalk SPL800 data and adding about 4 dB to the output numbers (bigger woofer, bigger enclosure, same amp power). IOW, the SPL1200 will probably have the same basic overall performance profile as the SPL800, but it will likely play 4 dB louder across the board (at the same THD limits) and will likely extend a bit deeper too.
 

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Quote:
Originally Posted by Prozakk
As well they should, being OWNED by Velodyne! BIASED. :rolleyes:
Owned by Velodyne? Since when?
 

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Quote:
Originally Posted by ManicMiner
I think I found the simplest solution of them all, I measured my own PB10 at 1 foot and 31.5hz and got 118db. ;)


One question Ed about measuring subs outside. Since the mic is placed in front of the sub, will it not favor subs that are either closed, or have the port in the front?


What I'm getting at is: When inside there will be surfaces to reflect ports that are facing backwards, so that the subs who have backward facing ports will maybe gain more db's from beeing measured inside, compared to the closed subs.


This maybe be a stupid idea, because I had it just now :)
Your 118 dB measurement isn't limited by distortion, so it's hard to make a judgement call here.


For a valid comparison, I measured 102 dB @ 32 Hz @ 10% THD @ 2 meters (acoustic center) from the PB10-ISD. Reduce that by maybe 2 dB if measuring to the face.


At 2 meters in 1/2 space, the orientation of the subwoofer has very little effect (maybe 1 dB) on the measured output, provided you keep the mic at the approximate acoustic center of the subwoofer. I told AVTalk this early in their planning stages, and it was borne out when they tested the 20-39PC+ in various physical configurations (standing vs. laying down).

Quote:
As well they should, being OWNED by Velodyne! BIASED.
I think they did a fair and honest job on the testing and I've stated that before and also at AVTalk. Yes, the shoot-out was sponsored by the largest Velo dealer in the UK, and yes many of the participants own Velo (as well as other brands). But I think that professional integrity can (and did in this case) rise above ownership preferences.


Roger (Slartibartfast) knows full well that I (or Yates, or anyone else) could in the future test one of the same subwoofers in 1/2 space at 2 meters. To fudge the test data to favor a brand would be the equivalent of professional suicide.


Sure, there will be differences due to the slight difference in test distance, and the different test rigs, absolute SPL calibration, and even the weather. But we should be very close on the FR profile, and we should be reasonably close (within 2-3 dB after accounting for slight measurement distance differences) on the THD limited output. Thus far, that has been the case with the Servo-15 V2 we have both recently tested.
 

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Discussion Starter · #16 ·
Ed: I'll copy&paste this, just in case you missed it.

One question Ed about measuring subs outside. Since the mic is placed in front of the sub, will it not favor subs that are either closed, or have the port in the front?


What I'm getting at is: When inside there will be surfaces to reflect ports that are facing backwards, so that the subs who have backward facing ports will maybe gain more db's from beeing measured inside, compared to the closed subs.


This maybe be a stupid idea, because I had it just now



And I have even one more question. The max SPL tests for the SPL series was done at 1 foot, would or wouldn't a 6db difference at 1 foot still be a 6db difference at 2 metres?


Thomas
 

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Quote:
And I have even one more question. The max SPL tests for the SPL series was done at 1 foot, would or wouldn't a 6db difference at 1 foot still be a 6db difference at 2 metres?
Not necessarily. As stated above, TN and JJ use completely different test methodolgy and mic distances. And when testing indoors, room resonances can impact the THD results; many of the subs TN tests show a marked decrease in 10% THD limited output at 40 Hz, and this is almost assuredly due to room resonances adding output at 60/80/120 Hz.


Again, a 4 dB increase over the AVTalk SPL800 data is probably a fairly accurate estimate of the SPL1200's capabilities.
 

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Discussion Starter · #18 ·
Quote:
Originally Posted by Ed Mullen
Not necessarily.
But in ½ space, would a 6db difference at 1 foot, still be a 6db difference at 1m and 2m?


I' not thinking about any particular tests, or testers, but just in theory.


PS! This will be the last question for today :)
 

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Quote:
Originally Posted by Ed Mullen
I think they did a fair and honest job on the testing and I've stated that before and also at AVTalk. Yes, the shoot-out was sponsored by the largest Velo dealer in the UK, and yes many of the participants own Velo (as well as other brands). But I think that professional integrity can (and did in this case) rise above ownership preferences.
I still doubt credibility, despite your statement. Nothing against you, by no means Ed.
 

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Discussion Starter · #20 ·
I just keep the fact that it is a Velodyne influenced forum in the back of my head, but as far as I could see the measurements of the DD18 were pretty much the same as those on UltimateAVMag.
 
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