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Old 21st January 2021, 05:08 AM   #5031
mabat is offline mabat  Czech Republic
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Earl, thank you indeed for your supporting words, both here and in the recent podcast.

I'm far from understanding the physics involved and would never be able to do any analytic work (which I deeply admire) but I've seen enough to recognize when someone claims BS and it kind of irritates me. For the most part I just try to pass it but sometimes it's stronger than me.
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Old 21st January 2021, 05:22 AM   #5032
Dkalsi is offline Dkalsi  United States
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Default Measurements from a failed print job

I took some measurements of the Peerless DFM-2535R00-08 (the only compression driver I have on hand) on a failed print job of the horn included in post #4948.

Basically, the adhesion failed at the very edges of the horn. In any case, I still was curious about the performance and just blue-taped the two halves (no epoxy, no glue, nothing) - just two sides taped together. So the horn should not be judged by the measurements included below (i.e. too many imperfections in the final assembly), but just wanted to share the results nonetheless. I just took quick 0 - 60 degree measurements (approximately 900cm @ 4ms gate time). I was pretty impressed - seems to reasonably match the results posted in post #4946, despite the imperfect print job.
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File Type: jpg polar.jpg (167.2 KB, 340 views)

Last edited by Dkalsi; 21st January 2021 at 05:28 AM.
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Old 21st January 2021, 05:33 AM   #5033
mabat is offline mabat  Czech Republic
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Thanks!

As for the print, I've found that the "brim" feature of a slicer (i.e. increasing the adhesion area on the first (few) layer(s)) really helps a lot in this regard.
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Old 21st January 2021, 06:16 AM   #5034
Patrick Bateman is offline Patrick Bateman  United States
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Quote:
Originally Posted by Dkalsi View Post
I took some measurements of the Peerless DFM-2535R00-08 (the only compression driver I have on hand) on a failed print job of the horn included in post #4948.

Basically, the adhesion failed at the very edges of the horn. In any case, I still was curious about the performance and just blue-taped the two halves (no epoxy, no glue, nothing) - just two sides taped together. So the horn should not be judged by the measurements included below (i.e. too many imperfections in the final assembly), but just wanted to share the results nonetheless. I just took quick 0 - 60 degree measurements (approximately 900cm @ 4ms gate time). I was pretty impressed - seems to reasonably match the results posted in post #4946, despite the imperfect print job.
This looks like something I would do.

I salute you!
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Old 21st January 2021, 06:22 AM   #5035
Patrick Bateman is offline Patrick Bateman  United States
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Originally Posted by gedlee View Post
A very clear indication of a problem.
To me, this is one of the most notable things about the Summas:

When I bought them, I was single and I lived by myself in a giant house, and I worked at home. So I would have those speakers blasting all day and night at ridiculous SPLs. And they just don't get fatiguing.

It's a bummer that this is so hard to quantify. For instance, I've been to dozens of audio shows, and a lot of customers peek their head into a demo room, listen for ninety seconds, then leave.

In that kind of a scenario, it's basically impossible for the customer to evaluate how the loudspeaker will sound long term.

Here's a weird comparison:

Nearly all of my TVs have been purchased based on whether they are "a good deal." As I slowly move into my new house, I decided that I would *finally* get a TV that was well regarded by the reviewers. So I went down to Costco, and I came *this* close to doing what I always do, which is buy the TV that gives you the biggest screen for the least money. But I managed to resist that urge, and instead I bought a Sony that was top rated, and cost about twice as much as the competition. I got the TV home, and when I plugged it in, it was *marginally* better. But as I watched it, day after day, I began to appreciate the things it does well. After owning it for a couple weeks, my old/cheap TV is intolerable.

But until I owned a GOOD TV I was incapable of detecting what the difference was.

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Old 21st January 2021, 06:24 AM   #5036
mabat is offline mabat  Czech Republic
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BTW, don't know if the two colours of the prints above were an aim or a necessity but definitely it looks good!

So that's another degree of freedom in waveguide design
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Old 21st January 2021, 07:24 AM   #5037
David McBean is offline David McBean  Australia
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Quote:
Originally Posted by gedlee View Post
To me, that is an example of a very bad device owing to the large amount of reflections.
Just to clarify, I was thinking in comparison to an equivalent-sized Bessel, conical, exponential, hyperbolic-exponential, tractrix or spherical wave horn.

The black trace in the attachment shows the power response of the Le Cléac'h horn example used earlier. As can be seen, the ripples in the throat acoustical resistance do not significantly affect the power result. The grey trace shows the power response of an equivalent exponential horn.
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Old 21st January 2021, 07:59 AM   #5038
mabat is offline mabat  Czech Republic
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As some start to print and measure the ST260, maybe it's useful to collect (again) the results so far - this is a courtesy of Pet007 who measured virtually the same WG before (maybe there was a tiny difference, I don't really remember), with three different drivers -

Just a note - the DI as shown is calculated from the front polars only (the only measured). The "real" DI will be closer to the simulations, where it is full-space.
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Last edited by mabat; 21st January 2021 at 08:03 AM.
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Old 21st January 2021, 08:16 AM   #5039
TNT is offline TNT  Sweden
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Originally Posted by Dkalsi View Post
I took some measurements of the Peerless DFM-2535R00-08 (the only compression driver I have on hand) on a failed print job of the horn included in post #4948. ...... snip
Nice, if not fantastic :-)! What was the circumstances around the measurements... did you use EQ? Or probably normalised - can we see the actual raw FR?

I mean this is +/-0,5 dB on axis between 450Hz and 20k - I suppose you have had to - please present the EQ curve. Also, at what spl was this? Can you extract distorsion out of your measurements - if so, please post some figures.

//
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Last edited by TNT; 21st January 2021 at 08:18 AM.
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Old 21st January 2021, 08:19 AM   #5040
mabat is offline mabat  Czech Republic
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That was normalized, i.e. effectively an EQ used such that the response at selected angle (on-axis in this case) is exactly flat. It clearly describes the WG "alone", without the properties of a particular driver. In the Pet007's data this is the left lower chart. The upper left is the raw data.
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