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Old 22nd December 2012, 10:21 PM   #21
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Default Triton MLTL Versus Power Input vs. SPL and Cone Excusion Study

I have attached a set of plots that show the baseline system frequency response vs, power input levels of 1, 10, 20, and 40 watts. Also shown for each plot is the cone excursion of the mid-woofers at these power levels. The specified linear excursion of the VWR126X driver used in this design is 5.8 mm. Note that within the excursion levels are just above 6 mm at 39 Hz for the 40 watts input case.

As noted before these the system plots are in in red while the blue plots are for an infinite baffle situation.
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File Type: pdf TritonMLTLSPLPowerInput.pdf (226.3 KB, 136 views)
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Old 22nd December 2012, 10:23 PM   #22
DDF is offline DDF  Canada
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The baffle extension affects the response in a frequency range in which any changes in the mltl tuning does not overlap, so these will not trade off each other

I can guarantee that the xover would have been different if originally designed for the larger baffle, given the target if flat on axis response. While the difference is not great in dB, it spans a wide bandwidth, which makes it appreciable

I don't have access to my files, but I could show you examples of my measurements taking a baffle and merely extending the front towards the ground. The change was always significant for baffles of this width

I'm not in any way commenting on the end sound but there are a few ways to view this, depending on your philosophy
1 measurements below 500 hz don't accurately reflect tonal balance, even for a point source
2 any difference in design intent can be compensated for by room placement
3 a belief that response should be flat, so it will sound different
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Old 22nd December 2012, 10:39 PM   #23
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Default Triton MTM MLTL Stuffing Density Study

Attached is a study of the stuffing density impact on system response. Stuffing density levels of 0.25, 0.50, 0.75 and 1.0 pounds per cubic foot are analyzed. The recommended baseline level is 1.0 lbs/ft3.
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File Type: pdf TritonMLTLStuffingDensityStudy.pdf (143.3 KB, 96 views)
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Old 22nd December 2012, 11:14 PM   #24
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Quote:
Originally Posted by DDF View Post
The baffle extension affects the response in a frequency range in which any changes in the mltl tuning does not overlap, so these will not trade off each other

I can guarantee that the xover would have been different if originally designed for the larger baffle, given the target if flat on axis response. While the difference is not great in dB, it spans a wide bandwidth, which makes it appreciable

I don't have access to my files, but I could show you examples of my measurements taking a baffle and merely extending the front towards the ground. The change was always significant for baffles of this width

I'm not in any way commenting on the end sound but there are a few ways to view this, depending on your philosophy
1 measurements below 500 hz don't accurately reflect tonal balance, even for a point source
2 any difference in design intent can be compensated for by room placement
3 a belief that response should be flat, so it will sound different
Hi Dave,

I just modeled the diffraction for both the upper and lower woofers on my baffle, assuming stand mounting, and for Jim's baffle. There are differences, but not enough that it would likely have changed the crossover.

The ray distances for all drivers to three edges remains the same for both baffles. It is only the distance to the lower edge that changes. For the most part the step freqeuncy, the frequency of the first peak, and that of the first dip all remain essentially the same. I would think for all practical purposes it is probably not a concern.

Jeff
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Old 22nd December 2012, 11:35 PM   #25
DDF is offline DDF  Canada
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Subjective decisions aside, I have measured this and for a given objective target, it necessitates a change
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Old 23rd December 2012, 12:11 AM   #26
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Quote:
Originally Posted by DDF View Post
Subjective decisions aside, I have measured this and for a given objective target, it necessitates a change
OK. However, I have taken measurements too, not with the Triton but with some other small speakers - sitting on a stand and sitting on another speaker that essentially extends its baffle. I was curious of this effect too. Although there were some changes in the response they were not of a magniude where I personally would have changed the crossover.

Technically you are correct. If I am trying to overlay the response with a target line then it would change the response and would necessitate a change in the crossover to match the line. But.... if the differences are small, as I have seen, then it doesn't make much sense to make this change.

I listened to Maynard's Continuum MLTL's along with a pair of regular Continuums. The only real difference I noticed was in the bass. The midrange and high frequency balance seemed the same in both speakers. There may have been a small difference somewhere if measurements were taken but I wouldn't have redesigned the entire crossover based on what i was hearing.
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Old 23rd December 2012, 01:57 PM   #27
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I have a photo gallery on Picasa which shows some in process photos of the Triton MTM MLTL build. The link is:

https://picasaweb.google.com/1083207...TritonMTMMLTL#

Last edited by Jim Griffin; 23rd December 2012 at 02:17 PM. Reason: correction
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Old 23rd December 2012, 02:32 PM   #28
pkitt is offline pkitt  United States
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Jim, for all of these plots, the drivers' excursions are actually larger than what's depicted in terms of mm Peak, because the Y-axis units on the excursion graph are mm RMS. The drivers' Xmax of 5.8 mm Peak would therefore occur on these graphs at 4.1 mm RMS. OTOH, Vance Dickason says it's usually safe to allow an excursion 15% greater than the specified Xmax. Doing that and converting to RMS units gives 4.7 mm RMS. I would say a safe input power limit for these drivers would therefore be 20 watts or a bit more.
Paul

Quote:
Originally Posted by Jim Griffin View Post
I have attached a set of plots that show the baseline system frequency response vs, power input levels of 1, 10, 20, and 40 watts. Also shown for each plot is the cone excursion of the mid-woofers at these power levels. The specified linear excursion of the VWR126X driver used in this design is 5.8 mm. Note that within the excursion levels are just above 6 mm at 39 Hz for the 40 watts input case.

As noted before these the system plots are in in red while the blue plots are for an infinite baffle situation.
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Old 23rd December 2012, 03:15 PM   #29
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Thanks for the post and noting the differences between peak and rms values. Martin's simulations do present the RMS deflection.

The Xmax specifications for the VWR126X are 5.9 mm (Klippel) and 10.4 mm (limit). Those are (I'm assuming) peak values. A reading of some of the Klippel's papers points how he has taken speaker measurements to a new level of precise definition.
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Old 23rd December 2012, 03:23 PM   #30
system7 is offline system7  United Kingdom
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Very much enjoying this thread, Jim. Your photos are excellent:
https://picasaweb.google.com/1083207...TritonMTMMLTL#

I reproduce a few images for the benefit of the sad souls who may be missing out on diyaudio membership here.

Jim Griffin's Triton MLTL conversion to a bigger box and more bass:

Click the image to open in full size.

Jeff Bagby's original MTM Gem, in this case with rear port:

Click the image to open in full size.

The Jeff Bagby crossover designed for the interesting CSS drivers:

Click the image to open in full size.

The smaller MTM version frequency response:

Click the image to open in full size.

You must excuse some of my colleagues here. They WILL quibble about EVERYTHING.

It's an honour to have Mr. Bagby here too. Thankyou, Jeff.
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