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Author Topic: JTR Triple 12 and Orbit Shifter  (Read 30542 times)

Art Welter

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Re: JTR Triple 12 and Orbit Shifter
« Reply #40 on: January 24, 2011, 03:19:16 pm »

Jeff Permanian wrote on Mon, 24 January 2011 09:02

Art Welter wrote on Wed, 19 January 2011 18:00


But now I know the one watt one meter sensitivity of four front loaded dual Lab 12s is only around 98 dB, I want a pair of DSL TH -218, their sensitivity is 10 dB higher !

Art Welter



Art, Since you've take quite an interest in my specs maybe you should take a look at other manufactures. DSL doesn't make a TH-218 but they do make a TBH-218, rated at 112db sensitivity, 2.83 volts, 2 ohms so minus 6db for a 1 watt sensitivity.

Thanks for catching that mistake  Embarassed .
The TBH-218 is too big, heavy, and physically too deep for me to want to use it, it's the size of four of my subs.
I should have wrote "I want a pair of DSL TH-118, their sensitivity is 10 dB higher".
The TH-118 is rated at 108 dB 2.83 v, so the four ohm cabinet is 105 dB one watt one meter, a pair 108 dB one watt one meter.

One of my dual Lab 12 is around 92 dB one watt one meter from 40 Hz to 100 Hz, a pair is 95 dB, four (eight cones) is 98 dB one watt one meter.

They won't win any sensitivity battles, but unlike most subs, can take full power down to their F3 without lots of distortion.

Art Welter
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Phil Lewandowski

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Re: JTR Triple 12 and Orbit Shifter
« Reply #41 on: January 24, 2011, 03:27:51 pm »

Art Welter wrote on Mon, 24 January 2011 15:19

Jeff Permanian wrote on Mon, 24 January 2011 09:02

Art Welter wrote on Wed, 19 January 2011 18:00


But now I know the one watt one meter sensitivity of four front loaded dual Lab 12s is only around 98 dB, I want a pair of DSL TH -218, their sensitivity is 10 dB higher !

Art Welter



Art, Since you've take quite an interest in my specs maybe you should take a look at other manufactures. DSL doesn't make a TH-218 but they do make a TBH-218, rated at 112db sensitivity, 2.83 volts, 2 ohms so minus 6db for a 1 watt sensitivity.

Thanks for catching that mistake  Embarassed .
The TBH-218 is too big, heavy, and physically too deep for me to want to use it, it's the size of four of my subs.
I should have wrote "I want a pair of DSL TH-118, their sensitivity is 10 dB higher".
The TH-118 is rated at 108 dB 2.83 v, so the four ohm cabinet is 105 dB one watt one meter, a pair 108 dB one watt one meter.

One of my dual Lab 12 is around 92 dB one watt one meter from 40 Hz to 100 Hz, a pair is 95 dB, four (eight cones) is 98 dB one watt one meter.

They won't win any sensitivity battles, but unlike most subs, can take full power down to their F3 without lots of distortion.

Art Welter



I would say that full 3rd party measurements of the JTR speakers would take care of most of the debate over this, which would be awesome.

Jeff, Are you by chance taking them to the same place that Danley gets their 3rd part measurements done at, because that would be awesome to have as comprehensive as a spec sheet as Danley and would definitely give some big time cred to the specs and cabs.


Take Care,
Phil


P.S. I still don't think we have the Danley model right, it is the DBH-218 I believe is being talked about.
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Art Welter

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Re: JTR Triple 12 and Orbit Shifter
« Reply #42 on: January 24, 2011, 05:11:11 pm »

Jeff Permanian wrote on Mon, 24 January 2011 09:10

Art Welter wrote on Fri, 21 January 2011 18:29

The SRX subs are not measured in full space, neither were Phil's measurements of either sub. His measurements of the JBL are within 2 or 3 dB of the JBL chart, considering his microphones are not calibrated or big buck, that is pretty close.



Art Welter wrote on Thu, 20 January 2011 14:20

I have attempted to calibrate my Smaart readings, but am not sure if they are absolutly on.
I have not attempted to calibrate them with the RTA 420 microphone I was using in the above test.
I have  written several times that I can’t get my 3 meters to agree at more than one frequency..

Art Welter


Forgive me if I question the absolute level of your measurements and your correlated sensitivities.

Jeff,

You are forgiven, and I’ll be glad to answer any of your questions  Laughing .

I have not claimed any absolute levels, though I have plenty of posts saying what my meters read in various situations.

Correlated sensitivities are fairly simple.  Measure two speakers under the same conditions, and relative levels are established. If the measurements look like the specs, good!

If they don’t, either the speaker is different due to production tolerances, the measurement positions relative to boundaries was different, or the measuring tools don’t agree.

I compared one of my front loaded 2 x12” Lab subs, nominally a 3 ohm load, to a JBL SRX 728, using the same drive signal, pink noise with a 25 and 125 BW filter, the undriven sub remained by the other sub, and was shorted out. Speaker cords were swapped into the same amp channel, no levels or settings changed.

As you can see, the JBL looks like it’s published specs, so the correlation is good, other than the RTA 420 microphone I used for the test reads a couple dB low at 30 Hz, and the filter reduces the LF output a bit more.

I don’t think you would suggest that a dual Lab 12 is any more than 92 dB , one watt one meter, or the JBL is louder than it’s published specification. This answers the half space or full space question that has been raised before, the SRX line is measured in half space.

The SRX 718 is basically half a 728, so three dB less sensitive, rated at 95, rather than 98 dB.

Phil Lewandowski’s measurements of his Growler and 718 come out remarkably similar to each other, which implies the Growler is the about the same sensitivity as the JBL SRX 718 in the 45-100 range.
The 2007 Prosound Shootout also shows the Growler to be about 95 dB average sensitivity 45 to 100 Hz.
index.php/fa/34854/0/

A few days ago, I was surprised to find my “quick and dirty” test position six feet outside my shop door added 4 dB in the octave around 40 Hz compared to the position I did the above test at, about 40 feet from two buildings.  

As Ivan Beaver wrote: “getting accurate measurements is not as easy as it may seem”.

Those measurements,  and the Orbit Shifter’s   2 dB (or possibly 8 dB depending on voltage applied) discrepancy between your graph and specified sensitivity are  why I asked you for distance from microphone to speaker, microphone calibration, and distance to any walls.

Art Welter
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Jeff Permanian

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Re: JTR Triple 12 and Orbit Shifter
« Reply #43 on: March 01, 2011, 12:54:43 am »

Unfortunately, the Growlers are that Pro Sound Shootout were malfunctioning. I ask Wayne very nice to please note that in the results. Here we are years later. Thanks Wayne.

There have been many who have independently validated the Growler's sensitivity.

Phil Lewandowski wrote on Sun, 27 April 2008 14:48

Hey!

Now that the weather up here in Cleveland niced up for me!! I was finally able to get outside and take some 1/2 space free air measurements on both the LA400 and the Growler!

As a forewarning:  These are not scientific by any means but I do think it really opens my eye to what EAW was measuring and I was impressed by how repeatable Jeff's data is on the Growler.  This was a very nice and fun learning experience so any advice is welcome!


My method:

I placed the sub in an open field on my property.  I measured 1 meter away from the sub pointed at it, on the ground.  The SPL meter was on slow response C-weighted.

I kept the sub not in use far away from the one being tested.

I used a QSC RMX1850HD to power both.  Both on channel one, switching from one to the other when each was tested one at a time.

I fed a sine wave using Adobe Audition on a MacBook.  I used a volt meter and used a sine wave to get an output voltage from the amp of 2.83 volts. (I just trusted that they are both nominally 8 ohms.)  Of course, I didn't run it trough any processing.  I didn't use a DSP either just to eliminate any chance of a variable.

I went through starting at 150hz going down in increments of 10hz to 100hz.  Then at 100hz down to 35hz I measure in increments of 5hz.




Here is what I found:

EAW LA400
It really enlightened me on where EAW got the sensitivity of 107dB.  It seemed like they got it around 150hz.  Which, I don't know many, if any live sound comps that cross there subs over that high!  So the rating is really irrelevant!  What I found is that the sensitivity in the range where the sub would be operating is something more like 102dB 1W/1M.  Which puts the -3dB point at about 50hz and the -10 point at about 40hz.  At least EAW seemed to get th -10dB point right on the spec sheet.  Although it isn't -10 from 107dB.   Very Happy   So the lowest usable frequency from this sub seems to be in the 45hz-50hz range and I think you can really hear that when listening!


JTR Growler:

This was very interesting because I believe for a spec sheet to be of use, the data should be repeatable.  I was impressed by the "repeatableness" of Jeff's +-1dB from 110 to 46hz claim! (Especially with my setup) Also his -1 point was spot on with what I measured!  When I asked Jeff about PEQ settings he said there was a hump around 140hz that I found.  But he said, that I shouldn't have to bother with that since I am crossing the subs over much lower than that.

I did find the -3 point to be about 44-43hz and the -10 point to be 36-37hz range.  The sensitivity was right where Jeff puts it @ 100-101dB 1W/1M.

So, I definitely give a big kudos to Jeff on really accurate repeatable data!


In all, I hope this helps some people who wanted to see some real data on the 2 subs!  Again, this was a learning experience for me and I loved it!


Thanks & Take Care!  Very Happy
Phil Lewandowski

P.S.  I am trying to figure out how to get everyone to be able to download the Exel file with all the measurements, since I can't attach it here!  For now I will just make a make-shift table!


It doesn't format well but the 1st column is the frequency, 2nd is the SPL of LA400 and 3rd is SPL of Growler.
HZ   LA400       Growler

150  107     103
140  106     107
130  106     107
120  106     104
110  106     101
100  106     100
95   105     100
90   105     100
85   105     100
80   105     101
75   104     101  
70   104     101
65   103     101
60   103     101
55   101     101
50   99      101
45   96      98
40   92      93
35   88      87
30   N/A     81

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