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Old 17th June 2011, 05:24 PM   #601
doug20 is offline doug20  United States
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Quote:
Originally Posted by JoshK View Post
Very much disagree. Say, if you want to cross at 900hz, the 18 is ideal and the DE250 is perfect in this case. Perfect for crossing to 15" drivers. Check the Geddes thread where he said that an 18" waveguide would be perfect for crossing to a 15" woof.
The SEOS-15 already offers that XO point. Its foolish to get a bigger waveguide and then not allow for even lower XO Point. A 1.5" throat gives us the ability to have a bigger CD.

If someone is thinking about building bigger horns they have to understand really why they are choosing the SEOS-18 over the SEOS-15.

The decision of someone wanting the SOES-18 to XO at 900Hz still is a silly decision when the SEOS-15 gives them that and matches already with a 15" woofer and it looks far better being that the sizes match. It already takes more skill to have a quality XO at 900Hz with a 1" CD (minus TADs), why fight logic and not go with a 1.5" or 2" CD that allows for a much lower XO point??


I will ask you this, why would you buy the SEOS-18 over the SEOS-15??
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Old 17th June 2011, 05:26 PM   #602
JoshK is offline JoshK  Canada
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Well based on all the data presented so far, I'd disagree with your assessment that the SEOS-15 can do a 900hz crossover point. Sure it *can* but its lost all directivity control by then, it looks like 1.25hz is about the best it can really do.
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Old 17th June 2011, 06:14 PM   #603
doug20 is offline doug20  United States
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We will disagree, the measurements show directivity down below 1KHz (900Hz is just fine), I guess we are looking at different measurements

Go to the AVS forum and ask that question if you like, no one else has posted any opinion so far that agrees with your 1.2KHz comment.

From coctostan
Quote:
The best match for the SEOS-15 will be a 15" woofer crossed around 900-1100hz.
I like his opinion over yours so far

Last edited by doug20; 17th June 2011 at 06:22 PM.
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Old 17th June 2011, 06:37 PM   #604
doug20 is offline doug20  United States
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Also remember Geddes summa (The perfection of OS speaker design with a 15" OS waveguide with XO around 900Hz) so to debate if the SEOS-15 is suitable to be XOed at 900Hz seems to be silly considering we have the ultimate precedence set already.

Heck, the design around the SEOS-15 used the 15" Summa waveguide, 900Hz point as the starting point back when the AVS thread started. I know because I forced that reference point

Honestly, The SEOS-15 design would be a failure in my books if it lost directivity at 1.25KHz.
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Old 17th June 2011, 08:47 PM   #605
JoshK is offline JoshK  Canada
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tit for tat aside, take a look at post #591 in this thread and tell me where you think the horizontal directivity loses control. All other data that I have seen shows similar so far. Also one needs to look at impedance and distortion to show where the waveguide is really loading to. I am pretty confident that will back up what I am saying.

I think your recollection of Geddes's design specifications overlooks some critical points. His choice of 900hz was on the overall design, not proof that the 15" OS WG held exactly to 900hz. He said is that same thread that he thought 18" would be more ideal (look it up). But, even still, the axisymmetric 15" waveguide has a lot more mouth area than the SEOS15, which was a tradeoff, known from the get-go in order to more optimize on CTC spacing. There is no free lunch. More mouth area will give more loading down low all else being equal. The measurements of the round WGs versus the square ones (QSC) clearly show this if you study them long enough and fits well with horn theory. But we intended this set of tradeoffs on purpose. I know, I was one of those helping with the design in the first place.

I am not saying that you can't mate a SEOS15 with a 15" woofer and get good results, just not the compromise I want to take. You choose your own set of compromises.

You can listen to whomever you wish. I don't care if you respect the opinions of others over me (I don't give two *****, but i did find that comment extremely childish). You follow whomever you like, but if you'd like to debate facts or compromises, then I am here to discuss with you. Otherwise your on your own.
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Old 17th June 2011, 08:52 PM   #606
JoshK is offline JoshK  Canada
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P.S. also look up augerpro's measurements of the QSC horn and comments as to how low that WG held directivity and I think you'll find the same 1.25khz comment (i think Zilch said it, iirc). Seeing as the SEOS15 was meant as a replacement with some more modernization, it too should also hold to 1.25hz, and the measurements I see confirm this.
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Old 17th June 2011, 09:03 PM   #607
JoshK is offline JoshK  Canada
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umm....went looking for other measurements other than the ones posted in this thread, so we could have something concrete to discuss. I too have seen comments thrown around as to what these WGs hold directivity to and wondered if they were looking at the same things as me. (it looks like people are looking at FR going down to 900hz, not the width between subsequent angle FRs which shows directivity)

....well I came across, who other than cocostan's response that says

Quote:
The ideal for the SEOS-15 will be a 12" woofer, but a 15" woofer will work very well too.

The ideal for the SEOS-18 is a 15" woofer.

The ideal for the SEOS-12 is a 10" woofer but a 12" will work well too.
AVS Forum - View Single Post - Waveguide and Horn Delivery (Photos)
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Old 17th June 2011, 09:03 PM   #608
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It would be much easier to read if the curves were presented in a polar format, but I also agree that about 1k25 is where they look like they're collapsing.
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Old 17th June 2011, 09:06 PM   #609
JoshK is offline JoshK  Canada
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yeah, I agree, its hard to see from the FR plots at multiple angles.
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Old 17th June 2011, 09:24 PM   #610
bwaslo is offline bwaslo  United States
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Looking at the horizontal curves, post 591, between 0degrees and 60 degrees, I read the same spread at ~950Hz as at 2kHz. A few dB at most narrower at 900Hz, hardly "collapsing"?
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