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BMS 18N862 Project

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rm31 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rm31 Quote  Post ReplyReply Direct Link To This Post Topic: BMS 18N862 Project
    Posted: 22 November 2014 at 12:30pm
Just thought I'd share the current project. As we use my system for predominantly dub, dnb, trap and dubstep nights here in deepest darkest france, the aim was to try and develop a box with:
- a limited box size (had to be able to fit one in the back of a chevrolet matiz for practical reasons)
- only one box per side due to having to be able to move the entire system in a single transit sized van
- Play comfortably at 40Hz at a respectable volume.
- Work with the amps I already had (crest cpx 2600's)

After a bit of hunting around someone suggested using the BMS 18N862 driver. A bit of messing around in winISD led to getting this:



A box with 225l tuned to 37Hz. I appreciate this is in theory so look forward to testing it properly with a rta kit. Anyway on to the build.

A quick course in sketch up led to this:





After a few weekends this ended up as this:




And then with the grills on one:







Now unfortunately due to the lead time on the drivers (ordered in October - arriving ??) I haven't got any further but will update as things progress. Smile
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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 22 November 2014 at 3:03pm
You have obviously ordered them at a wrong place :-) I hope that you will like the result. You never build the box completely until you measure the freq response first and be sure the tuning is spot on.
Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713
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corell View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote corell Quote  Post ReplyReply Direct Link To This Post Posted: 22 November 2014 at 3:22pm
im not sure if that chassis was the right choice for 37 hz tuning. have you compared to anything else?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Meat Quote  Post ReplyReply Direct Link To This Post Posted: 22 November 2014 at 4:42pm
We had my 18N850V2s in a box of similar size and tuning. They were damn good even though the sims suggested we should have them in something else. I reckon you'll be pretty happy. If it's accidentally tuned a bit lower then I reckon it'll cope with ease. Enjoy!
Don't test the champignon sound
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rm31 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rm31 Quote  Post ReplyReply Direct Link To This Post Posted: 22 January 2016 at 7:01am
So lessons learnt from phase 1:
1) Brace the box sufficiently - If it booms for any period of time after a given impulse (hit it with a hammer or block of wood and listen) you're not there yet
2) Wadd the thing - I thought I could get away not doing it but it changes everything
3) Pay attention to the selection of handles - the design above is getting new ones as the current spring loaded ones rattle horrifically
4) Work out what delay and phase it required when integrating with the rest of the system using a mic - tried it by ear and general consensus whilst setting up for a night and we settled on +4ms no polarity inversion. According to the scope, the 'right' results is +16ms and inverted. I have no idea why this is but it seems to work
5) Tuning seems to be right for my test track - Breakage - Circumference.

Time for phase 2 now - bracing, wadding and more testing
Martin Audio F2
RCF MB15N301
Martin Audio FSX
BMS 18N862
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odc04r View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 22 January 2016 at 9:07am
Good stuff, sounds like you will end up with a decent cab at the end of it all.
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rm31 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rm31 Quote  Post ReplyReply Direct Link To This Post Posted: 22 January 2016 at 12:08pm
I hope so. In time I would like 4 a side hung off an MC2 E45 to balance out the mids and highs effectively but the cost of the drivers for their sensitivity is a bit prohibitive at the moment.
Martin Audio F2
RCF MB15N301
Martin Audio FSX
BMS 18N862
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