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Old 30th May 2015, 09:09 PM   #1
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Default Design service required

I am hoping to build folded horn boxes for my two Celestion FTR18-4080FD drivers.

Is there anybody in the forums is can do this design work for me and what would the design fees be? I am confident to do a regular vented box design using the software available but I haven't done anything like a horn design and want to make sure it's perfect before I build it.

They will be used in professional sound reinforcement in medium to large indoor spaces plus some small to medium outdoor spaces. I will initially build two, then add more in the future.

I believe my drivers are okay for a horn design but let me know if I'm better off with a regular vented box instead.

thank you in advance for your help. Can pay with PayPal.

Last edited by aussie123; 30th May 2015 at 09:46 PM.
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Old 30th May 2015, 09:55 PM   #2
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Maximum size, desired LF response?
When you say "folded horn", do you mean a front-loaded horn specifically, or just some kind of horn?

Chris
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Old 30th May 2015, 10:06 PM   #3
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Originally Posted by chris661 View Post
Maximum size, desired LF response?
When you say "folded horn", do you mean a front-loaded horn specifically, or just some kind of horn?

Chris
Chris, I'm not an expert on these designs. I only know that some horn designs will give better projection of the low frequencies in larger spaces. I suppose I'm after the best solution for this intended use.

Regarding the LF response, I would be happy with around 33 to 36z at -3db, if that's possible considering the drivers I have and the intended use. I'm happy to have a big-ish cabinet if it helps get the desired result.
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Old 30th May 2015, 10:56 PM   #4
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You can get custom speaker cabinets built on ebay.
Not sure if they would do the crossover as well though.
Its worth a look.
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Old 31st May 2015, 10:04 AM   #5
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Okay, running it through Hornresp quickly, you can get 125dB per box down to 36Hz, seriously excursion limited - its hitting Xmax with a few hundred watts. A TH with a 2:1 compression ratio (probably about as high I'd go with these 18"s) manages it, in a 342L box.

IMO, for anything sensible-sized, you need to tune quite high. I can get 128dB down to 50Hz from a similar-sized box.

Alternatively, you can do a really big front-loaded horn. A stack of 4x 750L front-loaded horns will do around 135dB down to 34Hz. Not bad.


Will you be using large stacks all the time, or would you prefer something that works well in small numbers?


Chris
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Old 31st May 2015, 11:23 AM   #6
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Chris, there's some tough decisions to make here. These Celestion speakers may not be ideal for this purpose. What do you think? Will regular vented cabs be a better use for these drivers?

I would prefer if they could be used in smaller numbers, and not require large stacks. Am I asking the impossible?
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Old 31st May 2015, 01:14 PM   #7
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They're a bit behind the curve, IMO, compared to the top-end B&C/Beyma/RCF drivers. Still decent, but the linear excursion leaves some to be desired. IIRC, the B&C 18SW115 (a very good driver) has roughly twice the linear excursion, meaning one of those will do the same output as two of those Celestions. Now, if the Celestions are cheap enough and you've got the space to have a lot of cabinets, the Celestions represent the better purchase. However, if space is limited, I'd take the more expensive driver to get the last bit of output for a given box size.

If you'd like something that'll still work in smaller numbers, that narrows it down to either a vented cabinet, or a tapped horn. A front- or back-loaded horn needs large numbers to effectively increase the mouth side to create useful low-frequency gain.

I'll model up a couple of cabinets that'll hit mid-30s and see what's what.

Chris

Edit - 200L ported box per driver gives 121dB flat to 40Hz, -3dB at 35Hz.
A bigger tapped horn will give you more, but not a lot - excursion is easily the limiting factor as I'm only putting a couple of hundred watts in. A pile of 4 taped horns will break the 130dB barrier, and play well down to 35Hz.

Last edited by chris661; 31st May 2015 at 01:24 PM.
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Old Yesterday, 02:03 AM   #8
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Thanks Chris. I think I need to stick with the speakers I have. I bought them from Parts Express in the US and sending them back (from Australia) would be costly.

Just a note on the xMax, On the Parts Express website it says that xMax is 10mm, on the Celestion website it says 6mm. If Celestion says it's a 1000 watt speaker, 10m might be the right number. What do you think? I've contacted Parts Express for more info.

thanks again
Peter
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Old Yesterday, 08:31 AM   #9
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It's 6mm + 2.5mm = 8.5mm (70%Bl point)
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Old Yesterday, 08:58 AM   #10
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I would look at Art's Keystone subwoofer.
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