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RCF L18-P200N replacement

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Uwe Riemer2:

--- Quote from: Mark Wilkinson on April 25, 2021, 03:29:16 PM ---Hi Uwe, why not?

--- End quote ---
You always ask the big questions  :)

So what are the trade offs, if we put the driver in 200l compared to the 150l suggested design from B&C:
We gain extended range to the low end, which comes at the price of higher Group Delay ( and no, we cannot trade Group delay for simple delay here, we need the sound to happen now )
We lose efficiency, we lose maximum output above tuning.


But in the end you need to try out for yourself and see what you like better, or because this is a Live Sound Forum find out what is the more useful tool in SR.


Mark Wilkinson:

--- Quote from: Uwe Riemer2 on April 27, 2021, 08:07:39 AM ---You always ask the big questions  :)

So what are the trade offs, if we put the driver in 200l compared to the 150l suggested design from B&C:
We gain extended range to the low end, which comes at the price of higher Group Delay ( and no, we cannot trade Group delay for simple delay here, we need the sound to happen now )
We lose efficiency, we lose maximum output above tuning.


But in the end you need to try out for yourself and see what you like better, or because this is a Live Sound Forum find out what is the more useful tool in SR.

--- End quote ---

I looked at group delay for the B&C at 150L vs 200L and see what you mean.   Nice catch, something I'll pay more attention to on vented boxes from now on.

Re the more useful tool for live sound..... i stick to  front loaded horn subs for live, like Labhorns or Orbitshifters, so group delay is as low as it realistically gets, i think.

My bass-reflex are for home use and playback, so i can remove group delay via a boatload of FIR....and is why I never bothered to look at it before for vented subs.
That said, I'm a firm believer in the rule that 'the best designs require the least processing'.....so thanks for the pointer  :)

Helge A Bentsen:
Update on this project.
RCF confirmed that recone kits for 18P200N-II doesn't fit on the L18P200N frames. So reconing is off.
18TLW3000 doesn't fit inside the cabinet, there is some bracing in the way. It's off or I need to consider some woodworking.

B&C 18TBX100 fits and looks like a decent replacement in WinISD.
In terms of power, it looks like I can put in around 1KW per driver before I run into Xmax-limitations.
1.2KW if I use Xvar.

In terms of amplifier power, what would you suggest as a good target number per driver?
I've been looking at wiring 8 ohm drivers in pair and feeding them 2500W/4 ohm. I think this is "enough" for these boxes.

Chris Grimshaw:
A Powersoft T602 conveniently puts out 2500w/ch into 4ohm  ;)

IIRC, Xvar is what B&C would like you to use. I think that's based on harmonic distortion levels, rather than the simple motor geometry that Xmax is often based on.

I usually like to test the useful excursion of drivers myself, though. I have some Beyma 15P1200Nd drivers which are rated for 9.5mm of Xmax, but you can push them to 15mm without them complaining much - their mechanical overload is very graceful, but that's not in the datasheet.


Sizing the amplifier will depend on the program material etc - you need to keep in mind that the excursion curves in WinISD are what happens when you put in 90V RMS (or whatever level you're running at) into the drivers at one frequency. That's very rare in music, but not impossible.
I'd usually like 2x the driver's AES power rating for the amplifier, but that's not always cheap or convenient.

Chris

Helge A Bentsen:

--- Quote from: Chris Grimshaw on May 10, 2021, 04:28:57 PM ---A Powersoft T602 conveniently puts out 2500w/ch into 4ohm  ;)


Chris

--- End quote ---
Its the one Ive been looking at. Not suprised you guessed it  ;)
Agree on the 2x RMS figure, but were talking K20 or going with one amp channel per driver in 4 ohm.
Starts to get expensive and a lot of cabling/logistics.

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