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18" reflex sub ports

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stalian87 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stalian87 Quote  Post ReplyReply Direct Link To This Post Topic: 18" reflex sub ports
    Posted: 23 August 2017 at 3:04pm
Hey everyone,

I'd to like to build 2 reflex subs to sit on top of my 2 th18's. I found this build http://www.forum.poweraudio.ro/viewtopic.php?f=92&t=9643 but was wondering how i would calculate how big i need the 4 ports in that plan to be for the B&C SW115 driver?

I'd like my TH18's to run as sub bass, 60hz and below and these reflex subs between 60-125hz for more of a punch...

thanks for any help!
sal
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kevinmcdonough Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2017 at 3:18pm
hey

download WinISD, a piece of software designed for creating reflex speakers. You'll be able to play with the sizes of the ports and see what changes that makes to the response, and decide what will suit yout driver best. 

K
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Hemisphere View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2017 at 3:24pm
If you want more punch you can probably do better than a reflex cabinet, and you certainly don't need one as large as the one you just linked to.

That's designed to play sub frequencies as well, so it won't be much punchier than what you have already.
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stalian87 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stalian87 Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2017 at 3:56pm
ok cool, I'll give winISD a try!

Hemispere, you got any recommendations for a cab to suit my needs?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2017 at 3:58pm
It seems like a bad idea. If you already have th18 build kick bins. Do you already have bc sw115? Its good subbas speaker. You need speaker for kick not subbass.
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stalian87 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stalian87 Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2017 at 4:04pm
well I've actually got 2 BMS 18N862 drivers and they really kick ass but i defo want them more for sub bass so any driver and cab recommendations would be very welcome :)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2017 at 4:09pm
It depends what sort of sound you're after. There are band-pass horn designs dedicated to that range, but they're basically designed for big systems, and they won't cross nicely at 60Hz (or even 80Hz really) with 1 per stack, and outdoors would be even worse.

If it were me I'd probably be thinking about a compact double 12", possibly reflex, possibly sealed, with a V shaped baffle.

Something like the middle enclosure in this picture:


That'll give a really punchy kick in a relatively compact box, and it'll be plenty to keep up with the TH18...but you may need to cross it a little higher than 60Hz. Unless you make it bigger or port it.

12" cones are just much tighter. You might even be able to find a 10" cone that suits your needs, and that would be even punchier still. Two good quality 10 or 12" midwoofers with high excursion in a sealed or vented v-baffle, vertically aligned as pictured, or horizontally aligned to match the width of the TH18 (it might be possible to get a perfect square front face so you could rotate them depending on preference)

I don't know of any ready-made designs that do exactly that, but It wouldn't be a huge task to design something like that. Not much harder than trying to adjust another vented enclosure for a driver it wasn't designed for, and the results would be much more suited to your needs.

Edit: What's your budget for woofers? B&C SW115 is 400 quid @ BlueAran.. 400 pounds will buy you a pair of very high quality 12's. A pair of BMS 12N620perhaps : http://www.bluearan.co.uk/index.php?id=BMS12N620L&browsemode=manufacturer
That's only about 10% less cone area than 1x18"


Edited by Hemisphere - 23 August 2017 at 4:20pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cookie-dj Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2017 at 4:20pm
RCF 4PRO is very similar to the above  

The drivers are still available too, even the 8" horn mounted speakers I believe were available the last time I checked (I was going to build these)
Edit: The mid driver is still available, but the H6000 horn flare is not.
The blue aran 8" phase plug horn & driver combo works in the same frequency band though Thumbs Up


Edited by cookie-dj - 23 August 2017 at 4:25pm
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stalian87 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stalian87 Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2017 at 4:37pm
good stuff, thank you...the double 12s with a v baffle seem like a good design maybe crossing at around 80hz.

was actually looking at the BMS driver and then also had a look at the Faital pro 12RS1066...http://www.bluearan.co.uk/index.php?id=FTP12RS1066AP&browsemode=manufacturer
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2017 at 4:41pm
If you want to run  2x12's in a sealed arrangement down to even 75hz you'll need to give them a lot of power though. 

They can do it, but we're talking about somewhere around 1250w per driver to reach 125dB @ 75Hz, 130dB at 125Hz.

BMS do a ferrite 12 with incredible excursion capacity for 147 quid,  11mm xmax by conservative calculations, probably 15mm actual. (url=http://www.bluearan.co.uk/index.php?id=BMS12S305L&browsemode=manufacturer]http://www.bluearan.co.uk/index.php?id=BMS12S305L&browsemode=manufacturer[/url])

Two of them in a vented box of 60 litres with 3000w of amp power gets up to 131.2dB, flat to 65Hz, or in a sealed box it's more like 125.5 at 75Hz and 128dB at 125Hz.

I think sealed would sound better but you could reach 128dB in a vented arrangement with 1500w, which would be safer on the drivers and cheaper. With 3000w you would need to carefully limit the RMS and peak levels.

The Faital drivers probably aren't efficient enough. In a sealed arrangement, two of them are only 89dB/watt at 80Hz. The BMS are only 2 or 3dB more efficient, but you can see it's already a struggle to get the SPL to meet the output of the TH18.

You could vent the Faital's to enhance their low end efficiency, but it would still barely exceed the efficiency of the BMS drivers in sealed, and if you can get away with a sealed design, that would be preferable.


Edited by Hemisphere - 23 August 2017 at 4:48pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cookie-dj Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2017 at 4:43pm
could you not just go double 15" reflex for upper bass/kick? Seems the easiest way to get a nice kick (although I'm unsure on what sort of kick you are going for).
Reflex is easiest, BPH kick harder and louder, 15" Straight horns kick very well, but are just stupidly long
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stalian87 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stalian87 Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2017 at 4:51pm
what dyou think of the faital pro's compared to the BMS 12S305? be nice to keep weight to a minimum as well..the faital's are lighter and seem to have better displacement than the BMS drivers, albeit with more power...

dual 15's will be simply to big for my needs. I need to compromise on size unfortunately.

EDIT: sorry just saw your faital comments :)


Edited by stalian87 - 23 August 2017 at 4:54pm
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