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Dual 15" mid/highs upgrade
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Jack_The_Ripper View Drop Down
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Points: 214 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack_The_Ripper Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2018 at 9:53pm
Originally posted by Conanski Conanski wrote:

Originally posted by Jack_The_Ripper Jack_The_Ripper wrote:

The minimum reccomended crossover frequency for the 18 Sound ND3T is 1khz. Should I use Butterworth 18db/oct or Linkwitz Riley 24db/oct slopes?
LR24 at least, shallow filters are not an option at the lowend of a drivers response. And don't forget to take into consideration the low frequency cutoff of the horns they are mounted on before dropping the crossover frequency.

What about 36db/oct Linkwitz Riley on the lower end of the compression drivers and upper end of the 15" drivers?

With crest factor I have Steinberg Wavelab Elements 9.5.
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Yes that's what I would expect. I zoomed in on some sections of heavy dub tracks where the strongest part has long full notes run slightly into clip to try and understand the actual restrictions (if any) of Powersoft style reserve power amps in real world conditions. It's always less of an issue than people expect. Extended dub notes or similar are overwhelmingly the main cause of low crest factor, anything which has gaps in it has the crest factor determined more by the gaps than anything. Plus MC mic screaming. I don't think anyone ever intentionally puts long extended clipped mids into music but maybe I'm listening to the wrong music LOL

I can understand the concern as a system operator, that some totally convention-busting track will emerge that puts all these so called musical/technical 'rules' aside and manages to sound enjoyable to some audiences in the process (think how many times that's happened!), and if they've not adequately prepared for that then bye-bye drivers ('buy, buy drivers' following soon after). An RMS limiter wouldn't be acceptable in that case as it would just dip the overall volume by a few dB, ruining the music as it was meant to be enjoyed, but if a rig ever finds itself in a situation like that it would probably be best for all concerned if the volume really did dip a few dB!


Edited by Hemisphere - 17 June 2018 at 9:59pm
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Conanski View Drop Down
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Points: 2543 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2018 at 11:20pm
Originally posted by Jack_The_Ripper Jack_The_Ripper wrote:

What about 36db/oct Linkwitz Riley on the lower end of the compression drivers and upper end of the 15" drivers?


Do you have a way of measuring your systems response in the frequency and time domains?
Crossover selection is about tradeoffs, steeper slopes offer more driver protection but introduce more phase shift. Even order filters(12dB,24dB,48dB) sum flat and produce manageable phase shift while odd order filters don't. But those odd order filters can be of use if you know the drivers raw response, when combined together you may end up with the results you want, but failing that a 24dB filter is the best compromise.
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Jack_The_Ripper View Drop Down
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Points: 214 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack_The_Ripper Quote  Post ReplyReply Direct Link To This Post Posted: 18 June 2018 at 9:55am
I have the RTA built into the dbx Driverack PA2 but i've heard it's crap.
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surely the problem with any 15" up past the 1k region is going to be dispersion rather than frequency response on axis. It may sound fine in front of the speaker but Id expect a significant hole in the upper mid as you wander off to the sides
LOUDER THAN LOUD
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Yes, 1KHz is probably about the most you want to cross at to minimise dispersion issues. Less, ideally. The same is true of most 12's though.

RCF unfortunately don't publish off-axis response, but Faital publish 45 degree plots so you can see how the recommended 15fh530 http://www.faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=151060110 (I assume they meant 530 as there is no 15fh560) performs vs the 12" midbass driver, the 12hp1020 http://www.faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=201050110

Not much in it above 1KHz (actually on second glance there is quite a bit in it..the 12 has a hole of about 7dB and the 15 one of 12dB in the same place). The 12 does a little better in the 500-1KHz range but nothing to shout about, a dB or two.

Steep slopes and low cross necessary - 1.5KHz as suggested earlier is not a good idea..a lot rests on the limitations of the HF horn in these cabs. If they can't play low you either take the hit on dispersion or rethink the whole thing.


Edited by Hemisphere - 18 June 2018 at 11:17am
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odc04r View Drop Down
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Originally posted by Hemisphere Hemisphere wrote:

I don't think anyone ever intentionally puts long extended clipped mids into music but maybe I'm listening to the wrong music LOL



Metal guitarists would like a word!
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Elliot Thompson View Drop Down
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Originally posted by Jack_The_Ripper Jack_The_Ripper wrote:

Hemisphere and Elliot...
Thanks guys I thought the RCF MB15N405 would be a better option, compression driver wise maybe the 18 Sound ND3T would be better :


I'm not sure i'd wanna put anymore than 150 watts continuous average power (what people call RMS) into the compression drivers and 3,000 watts average power into each pair of dual 15" RCF MB15N405 drivers because I play techno and some of the tracks look to have as little as a 1.5db-2db crest factor due to being very heavily compressed. I don't fancy selling the mid/highs and trying to find or getting some made a pair of dual 12" cabs I can't be doing with the hassle. 


150 watts is more than enough for any compression driver for compression drivers are not rated for a lot of power once you choose not to use an external capacitor or crossover network after the amplifier. There are many that rather use more power which, can be based anywhere from not having anything smaller in terms of wattage in amplification, or just wanting to have a lot of headroom at their disposal. 

The above scenario will always have the amplifier loafing due to the efficiency of the compression driver/horn combination. 

I tend to cross my compression drivers lower than the majority and roll off my cone drivers higher as I rather have the cone and compression drivers work together as team within the 1 kHz to 2 kHz range. My aim is more High Fidelity results in which, you may be looking more to wards a sharper ear piercing results. So what I post below is more to wards High Fidelity results. 

Roll off the RCF MB 15N 405 at 2 kHz (-3 dB point)

Roll off the Eighteen Sound ND3T at 800 Hz (-3dB point) providing your horn can play 800 Hz.

The above will allow both drivers to share the work within the 1 kHz - 1.5 kHz range.  

If you are looking for a sharper response roll off the RCF MB 15N 405 lower and cut off the Eighteen Sound ND3T higher in addition to, using steeper crossover slopes (24 dB, 36 dB, 48dB and/or higher). 

It really boils down to listening to the performance of the loudspeakers using a high quality Techno track (In your condition) and tuning to taste. 

Best Regards, 
Elliot Thompson
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Points: 214 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack_The_Ripper Quote  Post ReplyReply Direct Link To This Post Posted: 19 June 2018 at 5:38pm
Thanks Elliot mate. 
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Originally posted by odc04r odc04r wrote:

Originally posted by Hemisphere Hemisphere wrote:

I don't think anyone ever intentionally puts long extended clipped mids into music but maybe I'm listening to the wrong music LOL



Metal guitarists would like a word!
Maximum amplitude extended clipped mids!? I mean I know they're clipped in the amp for the overdrive effect but even still, the bass fundamentals in the track from drums will have to be several dB higher than those clipped mids or they'd get lost in the mix. 

The point I made earlier about ASDR envelopes necessarily having a 'bite' followed by a drop in amplitude to be percieved as louder goes for metal guitar also. 

It's a fair point though, badly mixed/produced metal could pose a risk.


Edited by Hemisphere - 19 June 2018 at 5:59pm
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