Selenium HL4750

Cuppa Joe

Disabled Account
2010-07-18 6:24 pm
Seattle/Tacoma
selenium-hl4750-slf-2-bi-radial-horn-40x20-4-bolt--264-329
After numerous unsuccessful attempts to get a response from Selenium / JBL concerning this particular horn (Hey, great marketing strategy, boys!), it seems that I'll need to solicit the experiences of the general public.

Selenium has always boasted a 40-degree x 20-degree coverage pattern for the HL4750, but on the spec sheet the polar plots appear to show a pattern closer to 120 x 60 degrees. What am I missing?

For that matter, is anyone familiar with the build quality? I've heard quips about the factory's QC....
 
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Cuppa Joe

Disabled Account
2010-07-18 6:24 pm
Seattle/Tacoma
I double-checked the Parts Express product link, it seems to be working fine. The spec sheet PDF is on that page. The forum won't permit me to post a PDF file directly....

I have used Selenium compression drivers in the past, no complaints. The concern is with their fiberglass skills.
 
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wg_ski

Member
2007-10-10 5:21 pm
Their fiberglass skills are fine. The only problem I've had with an HL4750 can be attributed to UPS. I just patched it and used it.

As far as their pattern control, it's about as good as you can expect a bi-radial to be. These are narrow and I'll use them in singles if say, I need it loud on a dance floor area but quiet everywhere else. And they splay like this very well without a phasey sound as you walk around. This looks like it would sound like @**, but quite the opposite. And if you do stand between the stacks, you get a spooky make your hair stand up on the back of your neck stereo image. I call that good enough.
 

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You don't need to post the pdf directly, just post a link to it:
http://www.parts-express.com/pedocs/specs/264-329-hl4750-spf-spec-sheet.pdf

I opened the data sheet from the link on their page, then copied and pasted from the address line of the pdf.

I think you are ignoring the sound levels. They quote a 20x40 degree coverage, you see 120 degrees, but 60 degrees off center is 10db down, and I would imagine they are quoting a nominal spread at much less of a drop. Spread looks a lot closer to 40 degrees at 3db down.
 

Cuppa Joe

Disabled Account
2010-07-18 6:24 pm
Seattle/Tacoma
Thanks for the input, guys! I compared the polars of the HL4750 to those of other HF horns with measured dispersions between 90 & 120 degrees, finding that the patterns were more similar than not. I tend to believe that this horn is a wide-dispersion device, while Selenium's claim may be based upon live listening tests.

I don't know why the HL4750 can be arrayed in a horizontal arc with a minimum of perceived comb-filtering. Perhaps the wavefront "softens" enough at the mouth edges that the overlap isn't an issue? Perhaps the lack of a diffractive throat lends to that effect? I can only guess....
 

wg_ski

Member
2007-10-10 5:21 pm
Because the patterns overlap less as frequency goes up. Most claim that the narrowing dispersion is a flaw in exponential horns. Low frequency overlap causes some mild irregularity, but no deep nulls. And as you go very high (10k+) you do get "holes" from the pattern being too narrow, but they are nowhere near as noticeable as it would be in the 2k to 8k range.

I've compared these horns with their 90 and 120 degree units (1" exit). HL4750 have what can only be described as a 'cone of destruction', outside of which the output drops off dramatically. On the business end, prepare to be pinned to the wall. Off to the side you can hear yourself think. Turned around as a microphone, the 4750/D3300 combo makes an excellent (but expensive) long-range listening device.
 

Cuppa Joe

Disabled Account
2010-07-18 6:24 pm
Seattle/Tacoma
Yes, I expect an exponential to beam in the higher frequencies, but I'm surprised that the polars show no such evidence (at least to 8kHz). I've often wondered if Selenium matched the wrong polars to the horn.

Anyway, I got what I wanted, the reviews of someone who has direct DIY experience with this horn. My interest is the same as yours, a horizontal arced array. I imagine that the chosen splay angle has more to do with consistent coverage of the upper frequencies than with the lower.

What is the splay of your system? It looks closer to 30 degrees than 40. With how many angles did you experiment before you decided?
 

wg_ski

Member
2007-10-10 5:21 pm
The cabs are 30 degrees. It seemed to work with that horn, which was also the right depth for time alignment. I was concerned about them being too narrow initially. My older version used wider dispersion 1" horns and 4 cone mids per cab. But that system didn't work horizontally splayed very well, and couldn't keep up with the bottom end even when stacked on top of one another. That was in use for maybe 6 months before I dismantled it and bit the bullet for 2" exit horns and drivers.