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Looking for help with RCF MB15N351 plan

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Simplex31 View Drop Down
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    Posted: 19 November 2020 at 8:26am
Hello, 

After a long time of reading, I decided to build a new system using drivers that were lying around from older projects.

I Have 4 RCF MB15N351 that I want to put in a ported enclosure. I have calculated the following:

59 liter (net volume)
port size: 45,5cm wide, 20,8cm deep, 3cm high, tuned at 48hz

Would it work? I would like to run it from 80-ish to 1000-ish hz. After that an BMS 4592 takes over. Low end is 18sound LW1400 dual 18" BR.

Thanks in advance for any advice!

Regards,

John


Edited by Simplex31 - 19 November 2020 at 8:29am
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smitske96 View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 19 November 2020 at 9:05am
I would tune the RCF MB15N351 a bit higher, it would be somewhat limit down low due to its xmax (60Hz for example, and sufficient for full range). Also the crossover point is very high for a driver like the 4592, 650/700 Hz would be more logical for that setup.

Also note that you would need quite a few 18LW1400's to keep up with such a top cabinet, its getting quite outdated.
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Simplex31 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Simplex31 Quote  Post ReplyReply Direct Link To This Post Posted: 19 November 2020 at 11:26am
Thank you for your reply! 

Yes, I am aware that the 18LW1400 is an somewhat older driver, but there are 4 doing not much here at the moment. Smile

I chose the 48hz, because it is relatively close to the Fs of the speaker, benefiting the response. I do not plan to use it full range.

My goal is not persé max SPL, but more a hifi-like sound. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 19 November 2020 at 11:46am
What would you in this gain with tuning close to fs, if the volume is to small, and don't use it fullrange?
If you want less distortion, go for an arrangement that gives you less cone travel. Which results in less distortion.

Besides tuning, processing should be the next big step to get a different sound than most DIY speakers.
What do you have available regarding amps/dsp?


Edited by smitske96 - 19 November 2020 at 11:49am
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Simplex31 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Simplex31 Quote  Post ReplyReply Direct Link To This Post Posted: 19 November 2020 at 12:29pm
DSP will be Xilica XP3060, I am planning to use the BMS own crossover for the coax driver.
Amplification will be Bittner/Crest

What kind of volume and port would you recommend I use? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 19 November 2020 at 12:53pm
If you want it somewhat flat to 60Hz you're looking at >80L.
Port area I would go for something like 300/350 cm2 if you still want it to be able to play fullrange.
If not you can go somewhat smaller like 250 cm2. Also note that of you use a slot port that runs besides 
some cabinet walls the port should be made shorter then the winISD prediction (around a factor of 0.8).


What kind of horn are you using for the 4592?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Simplex31 Quote  Post ReplyReply Direct Link To This Post Posted: 19 November 2020 at 1:36pm
The horn will be the BMS 2236. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote VECTORDJ Quote  Post ReplyReply Direct Link To This Post Posted: 20 November 2020 at 12:09am
Hi, If You are crossing at 100 Hz with the industry standard 24 dB slope there will be little power at the tuning point. Moving the tuning point up or down or even sealing the box will make very little diff. I would use 45 Hz.  800 Hz to 1000 Hz will sound good for the high cross point. I have some in My parts stock.  Use the BMS VHF crossover. Make sure to match the BMS crossover to the ohms of the driver. BOTH the driver and crossover are sold as 8 or 16 ohm. I would use four 18s a side. Keep Rockin.................................... 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 20 November 2020 at 12:00pm
If you're certain that you are going to cross it around 800-1000, I would look for a different horn.
Personally I don't have experience with the BMS 2236, but have read enough comments about it not being top notch regarding sound. The 18sound XR2064 would be a nice one, or some of the Limmer horn options would be suitable.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote monkeypuzzle Quote  Post ReplyReply Direct Link To This Post Posted: 20 November 2020 at 12:06pm
I can vouch for the 2236 horns, I’ve got 4 with RCF ND950’s in them and they do the job very well. I haven’t yet found the best array angle for them so setup of two a side can have a few slight dropout areas at certain frequencies but I mostly just run one a side. They are clear and easily loud enough for my purposes.
blah blah blah blah blah......
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