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Preliminary info on the new Jubilee


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17 hours ago, LTusler said:

I put some black electrical tape over the holes on the back side, they pretty much disappeared. 

 

I would probably at least use a small Chicago screw per hole? but for the money being discussed here I would think they could fill the holes properly before paint.

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18 hours ago, LTusler said:

I put some black electrical tape over the holes on the back side, they pretty much disappeared. 

Especially in the dark:)......but seriously I tried this last night. It does look better when you can't see through the holes. Not like night and day difference but better.

What size are the holes? I think I would like to get some fancy little black nylon plugs instead of the tape.

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1 minute ago, babadono said:

Careful it maybe modified by the chief.

 

Not sure if there is any internal change but for sure the chief has added an external phase plug.

 

 

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See https://www.grainger.com/product/GRAINGER-APPROVED-Ribbed-Push-In-Rivet-5RKV7

 

5RKV7_AS02?hei=536&wid=536&$adapimg$=

 

The K-402 mounting hole diameter is 0.3 inches (7.62 mm)

 

I used the 0.25 inch version--and that works, too.

 

20 hours ago, babadono said:

Does the veneered front panel frame for the 402 need a modified tractrix bevel?

No.  The K-402 horn itself is good down to 172 Hz before the axial length begins to approach 1/4 wavelength.  (The horn mouth itself is good down to ~40 Hz for directivity control.)  At that 172 Hz point, the wavelengths are 78 inches long, and the small mouth flange itself isn't significant.  The Celestion Axi2050 can be used down to ~225 Hz.  Roy's preliminary data sheet shows that he's crossing at 340 Hz, so you're in good shape without any tapers or "baffle step" considerations.

 

See

 

Chris

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1 hour ago, MMurg said:

Not sure if there is any internal change but for sure the chief has added an external phase plug.

That's not a phase plug--it's actually an acoustic horn lens--mounted at the horn throat entrance. 

 

Phase plugs are important to prevent high frequency cancellations, while horn lenses are used to spread out the polars via "refraction". 

 

The only issue is that you also get unavoidable diffraction from horn lenses--just like the optical varieties do, too. It's a toss up whether the diffraction overcomes the refraction capabilities of the horn lens. 

 

Chris

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43 minutes ago, babadono said:

@Khornukopia I'll bet you know the size of the holes in the 402:)

 

The mounting bolts are quarter inch diameter. Shortly after getting my K-402s, I made a decorative frame to hide the extra holes.

 

 

1676079747_IMG_6370-Copy.JPG.04afd2e93ecc080ec6c6097639760317.JPG

 

897469643_K-402onK-horn.jpg.3f2bf5af9649ff707584dfd93f8d7050.jpg

 

 

The trim improves the appearance and does not affect the sound of the horn. I like the look of the wider frame on the New Jubilee.

 

 

 

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7 minutes ago, Chris A said:

That's not a phase plug--it's actually an acoustic horn lens--mounted at the horn throat entrance. 

 

Phase plugs are important to prevent high frequency cancellations, while horn lenses are used to spread out the polars via "refraction". 

 

The only issue is that you also get unavoidable diffraction from horn lenses--just like the optical varieties do, too. It's a toss up whether the diffraction overcomes the refraction capabilities of the horn lens. 

 

Chris

 

Well, then complain to whoever wrote the text for the video because that's what it says.  🙂 

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Roy has already stated that the YouTube video is in error due to showing the Jubilees outside of room corners--which are still required. (He said the marketing guys took a few liberties in the video without asking him first.)  If you were thinking about buying a pair and pulling them away from the room corners--think again.  Adding the horn lens change is just a small concern as compared to that error.

 

Chris

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2 minutes ago, Chris A said:

Roy has already stated that the YouTube video is in error due to showing the Jubilees outside of room corners--which are still required. (He said the marketing guys took a few liberties in the video without asking him first.)  If you were thinking about buying a pair and pulling them away from the room corners--think again.  Adding the horn lens change is just a small concern as compared to that error.

 

Chris

 

LOL.  That was a ridiculous gaff.  Mine are going in the corners.  Already asked Roy a bunch of questions about placement in my room (with pictures) in a Facebook group thread.  He's so great about answering people's questions.

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32 minutes ago, Chris A said:
58 minutes ago, babadono said:

Does the veneered front panel frame for the 402 need a modified tractrix bevel?

No.  The K-402 horn itself is good down to 172 Hz before the axial length begins to approach 1/4 wavelength.  The horn mouth itself is good down to ~40 Hz for directivity control.  At that point, the wavelengths are 78 inches long, and the small mouth flange itself isn't significant.  The Celestion Axi2050 can be used down to ~225 Hz.  Roy's preliminary data sheet shows that he's crossing at 340 Hz, so you're in good shape without any tapers or "baffle step" considerations.

All righty then...wasn't really expecting an answer hence the smiley face...more just goofing on everybody....it's all good ...carry on

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23 hours ago, babadono said:

Wanna make sure I understand....just so light would not come through open holes? I am going to see what visual effect this has (to me) this evening.

Yes, I found the light peeking through annoying, mine are halfway in front of windows.

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9 hours ago, Chris A said:

That's not a phase plug--it's actually an acoustic horn lens--mounted at the horn throat entrance. 

 

Phase plugs are important to prevent high frequency cancellations, while horn lenses are used to spread out the polars via "refraction". 

 

The only issue is that you also get unavoidable diffraction from horn lenses--just like the optical varieties do, too. It's a toss up whether the diffraction overcomes the refraction capabilities of the horn lens. 

 

Chris

That’s interesting. I didn’t know that....🙂

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22 hours ago, Chief bonehead said:

That’s interesting. I didn’t know that....🙂

Lol. 

 

Now @Chief bonehead I'm intrigued by this inherent "problem" associated with all compression drivers of collapsing polars ("beaming") when the wave length becomes larger than the size of the diaphram, which I think you said on a typical 2" comes into play at 7Khz. (Did I say that correctly? Is 7Khz the number for 2" CD, about 10Khz for 1"?). 

 

I remember at an event back in '07, that with the K-69 configuration (and phase plug?) that beaming didn't come into play until (can't remember the figure but it was well above 7Khz) but still a bit short of the ideal 20K. I think you also said later on the 691, with your phase plug, had even improved upon that.

 

Then another year you showed us how beaming plays out - you can localize sound. How this plays out is that beaming would allow the brain to  localize the speaker with higher frequency sound like cymbals for example. During normal passages the speakers "disappear", no localized sound source, but with a strike of a cymbal, the illusion disappears and the brain says "you Bonehead, that wasn't natural soothing sound, you are listening to a loudspeaker, and it's coming from right over there." An obvious negative.

 

Does the horn being used change the beaming frequency? Same 2" driver on a 402, 510, K-400, would the beaming all start at about the same frequency?

 

What point do the off the shelf new drivers on the K-402 start to beam without your phase plug? 7Khz?

 

Travis

 

Edit: Are those new drivers 2" or 5"? Where's the beaming start with a 5" compression driver? 

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On 6/17/2021 at 2:33 PM, MMurg said:

 

Well, then complain to whoever wrote the text for the video because that's what it says.  🙂 

Roy wrote it, or at least provided the name for it. He showed you what beaming was in the class you were at when you got off axis, and I believe in comparing a prior model to a current model.

 

That doohickey that Roy calls a (convoluted name that I can't remember goes here) Phase Plug, dramatically increases the frequency where the drivers start to "beam."  

 

 

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10 hours ago, babadono said:

Well 1/4 inch plugs are too small.......next up 5/16:)

 

The holes on the 402 horns take 8 mm (a bit less than 3/8” at .315”) bolts, so that’s your size, unless that’s too tight a fit.

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