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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Subwoofer Forum => Topic started by: Mark Wilkinson on May 16, 2017, 05:09:14 pm

Title: diy single 18"s and OS
Post by: Mark Wilkinson 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.




                                 

Title: Re: diy single 18"s and OS
Post by: Stephen Kirby 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.
Title: Re: diy single 18"s and OS
Post by: Len Zenith Jr 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.
Title: Re: diy single 18"s and OS
Post by: Chris Grimshaw 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
Title: Re: diy single 18"s and OS
Post by: Mark Wilkinson 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 !
Title: Re: diy single 18"s and OS
Post by: Mark Wilkinson 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

Title: Re: diy single 18"s and OS
Post by: Bill Hornibrook 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.
Title: Re: diy single 18"s and OS
Post by: Mark Wilkinson 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.....
Title: Re: diy single 18"s and OS
Post by: Bill Hornibrook 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.
Title: Re: diy single 18"s and OS
Post by: Don Davis 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
Title: Re: diy single 18"s and OS
Post by: William Schnake on May 17, 2017, 06:50:45 pm

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

Mark, those look fantastic. 3 years ago I had a cabinet make me a pair that are almost exactly like these.  I loaded them with some RCF 18P400 and they are my go to for shows where we are going to have 150 or less.  These are for small Corp customers with live acts.  I am always amazed at the amount of low end that they produce.

Great job and good luck with them.

Bill
Title: Re: diy single 18"s and OS
Post by: Mark Wilkinson on May 17, 2017, 08:07:48 pm
Bill, many thanks for the kind words !

I too, am a little amazed at how low, and without any holes, they go. 
I love my horn loaded subs, but it's almost like these direct radiators impart a texture to the bass that you can feel, along with the hearing. And it ain't distortion.... :)
I wanna build a block of them haha !
Title: Re: diy single 18"s and OS
Post by: Mark Wilkinson on May 17, 2017, 08:38:15 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

Thank you Don !  Good to hear from you.
Yes, I used them at a VT graduation party this weekend with a single JTR 3TX.  (PM60 would have been overkill  ;) )
I had both the subs on one channel of a PL380 and the 3TX on the other.  It all sounded super till it came time to really crank VT's fight song, Enter Sandman.
Still sounded super...just wished I had 4 subs....but a 3TX is good for a pair of OS's, so of course I needed more subs...

Hey your urge to build, and comment about 12 in inventory, are about to get me making more sawdust  ;D

edit :  I realized you were probably asking if I have used the diy 18"s with the OS, on an event yet....
Not yet for an event, but a band manager came by yesterday afternoon to check out what I can offer...
Since I had the subs already setup in the driveway for testing, I just threw a top on the sub combo betting it would work as well at volume, as in testing.
If it didn't deliver at volume I was going to pull out another OS.
But happily, it worked and sounded, excellent.

The more I think about, the more i get convinced combining different type subs shouldn't be that hard.....the wave lengths are huge.....if anything can be coupled it ought to be subs..
I mean, if they are located together, and the exact same HPF and LPF types, orders, and frequencies, are used on all the subs so that there isn't any electrical crossover phase difference, well....
.....all we have left to align is the natural phase difference of the sub type, and maybe some physical distance offset.
It shouldn't take that much FIR, if all we're trying to align is the natural phase difference between sub types. I just can't see latency being a problem.
Maybe it's a cheap way to couple existing sub inventory across different type boxes ....?????
Title: Re: diy single 18"s and OS
Post by: Bill Hornibrook on May 18, 2017, 01:36:28 pm
Mark I just noticed that one of the ways you were able to keep weight down was by using 15mm BB. Are you happy with that decision now that they are built? Were you able to keep cabinet vibration to a minimum via internal bracing?

It may be a way I'll proceed if you were successful.
Title: Re: diy single 18"s and OS
Post by: Mark Wilkinson on May 18, 2017, 03:53:24 pm
Mark I just noticed that one of the ways you were able to keep weight down was by using 15mm BB. Are you happy with that decision now that they are built? Were you able to keep cabinet vibration to a minimum via internal bracing?

It may be a way I'll proceed if you were successful.

Hi Bill, yes, I am happy with 15mm and would do it again. 
 
That said, the boxes do vibrate a lot when really cranked, but I doubt 18mm would make much of a difference.

I've read that doubling wall thickness reduces deflection by 1/4th, but reducing span by 1/2 reduces deflection by 1/8th. 
So IOW, deflection vs thickness is a squared function, span vs deflection is a cubic function.
To me this means, think about more about bracing than wall thickness....but disclaimer .....I AM A COMPLETE NOVICE here.......

FWIW, the triangular corner ports were a big part of the bracing trumps idea....
Title: Re: diy single 18"s and OS
Post by: Don Davis on May 18, 2017, 04:45:03 pm

The more I think about, the more i get convinced combining different type subs shouldn't be that hard.....the wave lengths are huge.....if anything can be coupled it ought to be subs..
I mean, if they are located together, and the exact same HPF and LPF types, orders, and frequencies, are used on all the subs so that there isn't any electrical crossover phase difference, well....
.....all we have left to align is the natural phase difference of the sub type, and maybe some physical distance offset.
It shouldn't take that much FIR, if all we're trying to align is the natural phase difference between sub types. I just can't see latency being a problem.
Maybe it's a cheap way to couple existing sub inventory across different type boxes ....?????
Yes, sorry I wasn't clear but I was wondering if you had used the OS's and single 18's together. I have seen a lot posts that say don't mix and match but if you approach it as you have with analysis and testing what have you got to lose in trying. You can always check for cancellations in Smaart. I'll bet you can get them to play nice together.
Title: Re: diy single 18"s and OS
Post by: Jeff Permanian on June 17, 2017, 05:58:25 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.                             

The Orbit Shifter does have a 10db output advantage 40hz and above which is equal to three drivers. I definitely understand size being an issue which is one of the reasons for our new Captivator 212.