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Author Topic: diy single 18"s and OS  (Read 2818 times)

Mark Wilkinson

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diy single 18"s and OS
« on: May 16, 2017, 05:09:14 pm »

I built a pair of vented single 18"s, for the occasions when I just plain need to be able to carry a smaller sub than an Orbitshifter or Labhorn into place.
Had such an event last weekend, a backyard VT graduation party; and i was very pleased with them although they are a little harder to lug by myself than i hoped.

I went with the BMS 18N862 driver because Josh Ricci has posted both vented and sealed builds for this driver, and that let me sanity check my beginner modeling attempts.
The box was modeled to f3 = 31Hz, and dang if it didn't work out pretty close.

All the following measurements had a 24 BW highpass @24Hz, and a 48 LR lowpass @ 100Hz in place.  Filters were linear phase, no other eq.
I measured the pair of 18"s because I wanted to compare them to a single Orbitshifter. So it's a pair of 8 ohm nominal 18"s in parallel, against a single 4 ohm OS.
Same exact signal, levels, filters, etc to both.

First plot below is the response of the 18" diys.
 
Next is the single OS.

And then both, where:  red = diy 18"s       green=single OS      blue = both
9ms delay was added to the diys to match timing of OS

I ran LEQ's to get level differences.  DIY=91.2dB    OS=92.3   BOTH =97.4dB
Those LEQs reflect the responses shown in the given curves.

Must say I'm really pleased how well the diys are doing, and also how great the two sub types summed.
Pulling voltage and distance down to 2.83v at 1 meter, would put the pair of 18"s at 101.9dB, and the single OS at 103dB.




                                 

« Last Edit: May 16, 2017, 05:44:02 pm by Mark Wilkinson »
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Stephen Kirby

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Re: diy single 18"s and OS
« Reply #1 on: May 16, 2017, 09:27:44 pm »

Be careful with an f3 that low.  It's really easy to hit excursion limits.  While that sounds impressive, unless you're doing some crazy EDM music, getting down between 40 and 50 sounds like deep bass to most people.

I was at the local arena the other day with a 16 box hang of VerTecs and some unknown quantity of subs I couldn't see.  I noted that the walk in music seemed to have a one-note rumble going on underneath it.  So I pulled out the FFT app on my phone and there was a big bump in the low 40s.  I've been in other situations where the bass was "bumping" and it was primarily around 60Hz.
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Len Zenith Jr

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Re: diy single 18"s and OS
« Reply #2 on: May 17, 2017, 03:38:19 am »

I've been in other situations where the bass was "bumping" and it was primarily around 60Hz.

63Hz is where hiphop lives.
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Chris Grimshaw

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Re: diy single 18"s and OS
« Reply #3 on: May 17, 2017, 09:24:18 am »

I built a pair of vented single 18"s, for the occasions when I just plain need to be able to carry a smaller sub than an Orbitshifter or Labhorn into place.

Nice work!

Got any pictures of the finished cabinets?
Any impressions of how they hold up when you put some power down?

Chris
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Sheffield-based sound engineering.
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Mark Wilkinson

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Re: diy single 18"s and OS
« Reply #4 on: May 17, 2017, 01:05:01 pm »

Be careful with an f3 that low. 

Hopefully, I've done enough homework so that f3 31Hz is ok.
   
Both Jeff Bagby's spreadsheet and Hornresp show about 16-17mm excursion at 31Hz, at 1500w AES rating.
BMS specs xmax at 19mm. 
And then I keep the 24dB BW @24Hz HPF in place to prevent unloading below 31Hz.  Plus I limit voltage well below full power....before distortion and compression kick in..

It does sound really good down there.....really good !
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Mark Wilkinson

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Re: diy single 18"s and OS
« Reply #5 on: May 17, 2017, 01:27:04 pm »

Nice work!

Got any pictures of the finished cabinets?
Any impressions of how they hold up when you put some power down?

Chris

Thank Chris !

Couple of picts below...one already posted in another thread, and one showing relative size against orbitshifter.

They've held up great so far, but the most I've thrown at them is putting each one on a PL380 channel....
My guess is, for long term output, the pair hangs in with a single OS.....based on numbers below, and roughly equal power handling.

This morning, I did some quick eq work on the OS to smooth it out.
Between the boosts and cuts,  LEQ of the OS dropped 1 dB, vs a LEQ with no eq.

So today's measured LEQs:          DIYs = 92.6 = red    OS=93.4 = green      Both=99.0 = blue
I'm loving the summation

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Bill Hornibrook

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Re: diy single 18"s and OS
« Reply #6 on: May 17, 2017, 01:32:04 pm »

63Hz is where hiphop lives.

25 years ago.

Mark love those pics! Nice work! I was hoping you would post some. I was wondering... what are their outside dimensions, and have you weighed them?

I've been thinking about doing a project like this myself... maybe one more build before I'm done.
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Mark Wilkinson

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Re: diy single 18"s and OS
« Reply #7 on: May 17, 2017, 04:25:05 pm »

25 years ago.

Mark love those pics! Nice work! I was hoping you would post some. I was wondering... what are their outside dimensions, and have you weighed them?

I've been thinking about doing a project like this myself... maybe one more build before I'm done.

25 years ago agreed ;D

Thanks Bill !

They are 23 1/4 x 23 1/4 x 29 1/2 D.   15mm BB cabinet, triangular corner ports, and braces, 18mm BB baffle.  91 lbs everything included
A little bigger and heavier than this 65 year old wanted, but I can lift em into my truck and wrestle them up stairs....so all good.
I do believe they could be 10 lbs lighter if I didn't want to get down to 31 Hz with low port velocity.....
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Bill Hornibrook

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Re: diy single 18"s and OS
« Reply #8 on: May 17, 2017, 05:09:15 pm »

Size is nice and compact, and love the weight! Contemporary hip-hop is a part of what I do, so I wouldn't want to change the low frequency extension at all. That genre drops into the low 30s with increasing regularity.
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Don Davis

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Re: diy single 18"s and OS
« Reply #9 on: May 17, 2017, 06:32:42 pm »

Good job Mark! The boxes look great. I like your comparison to the OS's. Have you used them together at an event yet?

For my use I find single 18's offer the most flexibility. I've got 12 in the inventory now.

What is it about subs, when I see someone do a successful DIY project I have the urge to start making saw dust even though that's the last thing I need more of right now.    :D
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