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Author Topic: Sub design for a 18 Sound 12" subwoofer  (Read 4731 times)

Dave Jackman

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Re: Sub design for a 18 Sound 12" subwoofer
« Reply #20 on: March 10, 2018, 10:26:38 am »

Looks reasonable. What does the simulation look like?

For what it's worth, bracing can be particularly effective when you join opposite panels. In subwoofer use, the forces acting on the panels will try to blow the cabinet up like a balloon, so physically connecting the opposite panels strengthens against that very well.

Chris

Will do. Thanks.
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Dave Jackman

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Re: Sub design for a 18 Sound 12" subwoofer
« Reply #21 on: March 10, 2018, 10:32:08 am »

It's approximately 59.5l net internal volume which should leave it tuned to about 45Hz.
That's actually not too bad at all for your driver.

However, the bigger question raised is what you mean by "light DJ work" please?
One 12" sub on its own will not produce enough bass to keep up with most of what I understand DJ'ing to be about, so you may very well still end up disappointed even if you build a box that gets the best out of this driver.

What size audiences will you be playing to, and what main PA speakers will you be using? Those 2 factiods should help narrow down what you might actually need, in case it doesn't match what you've bought.

That said, here's the predicted plot for your driver in the fEarful box. It will take around 340W to reach Xmax; at this power level vent airspeed is very good at 16.5ms-1. A 39Hz Butt24 HPF is again needed.

Cheers,
David.
150 people-no hiphop just country ,rock and roll and some pop

Tops will be EV ZLX12p or the like
How can I tune to 50hz or is the diff not even worth worrying about?
Thanks,David
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David Morison

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Re: Sub design for a 18 Sound 12" subwoofer
« Reply #22 on: March 10, 2018, 12:35:49 pm »

150 people-no hiphop just country ,rock and roll and some pop

Tops will be EV ZLX12p or the like
How can I tune to 50hz or is the diff not even worth worrying about?
Thanks,David

One 12" bass bin will absolutely not keep up with 2 12" mains if you really want it to have some impact, I'd want one 15 or preferably 18 per 12" as a starting point.

Tuning higher (by shortening the vent) tends to push the response up into a hump, which can sound unnatural due to it causing "ringing" around the tuning frequency - I've not experienced an example of it myself, only read a little about it, so can't predict how obnoxious it would be in any given case. Reducing box volume can mitigate this though - that would take you back towards the kind of smaller box I modelled earlier. Obviously, both raising tuning and reducing internal volume both cost you in terms of less LF extension.

Herewith the fEarful box with ports shortened to 20cm only in yellow (HPF increases to 42Hz, Power to 390W) and a 45l box tuned to 50Hz again wtih 42Hz HPF and power at 440W in violet.

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Ivan Beaver

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Re: Sub design for a 18 Sound 12" subwoofer
« Reply #23 on: March 10, 2018, 02:55:12 pm »

Looks reasonable. What does the simulation look like?

For what it's worth, bracing can be particularly effective when you join opposite panels. In subwoofer use, the forces acting on the panels will try to blow the cabinet up like a balloon, so physically connecting the opposite panels strengthens against that very well.

Chris
I always tried to tie the sides together, and the top and bottom together-with both of those braces tied together.

Bracing is KEY to getting a good sub cabinet.  Yes it is more trouble, and the cabinet gets heavier, but the results are far better.

I also like to put braces on individual panels as well so that the individual panel cannot flex.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Dave Jackman

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Re: Sub design for a 18 Sound 12" subwoofer
« Reply #24 on: March 10, 2018, 04:16:47 pm »

One 12" bass bin will absolutely not keep up with 2 12" mains if you really want it to have some impact, I'd want one 15 or preferably 18 per 12" as a starting point.

Tuning higher (by shortening the vent) tends to push the response up into a hump, which can sound unnatural due to it causing "ringing" around the tuning frequency - I've not experienced an example of it myself, only read a little about it, so can't predict how obnoxious it would be in any given case. Reducing box volume can mitigate this though - that would take you back towards the kind of smaller box I modelled earlier. Obviously, both raising tuning and reducing internal volume both cost you in terms of less LF extension.

Herewith the fEarful box with ports shortened to 20cm only in yellow (HPF increases to 42Hz, Power to 390W) and a 45l box tuned to 50Hz again wtih 42Hz HPF and power at 440W in violet.

Thanks again.
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Dave Jackman

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Re: Sub design for a 18 Sound 12" subwoofer
« Reply #25 on: March 10, 2018, 04:19:02 pm »

I always tried to tie the sides together, and the top and bottom together-with both of those braces tied together.

Bracing is KEY to getting a good sub cabinet.  Yes it is more trouble, and the cabinet gets heavier, but the results are far better.

I also like to put braces on individual panels as well so that the individual panel cannot flex.

Will certainly bear this in mind.
Thanks Ivan.
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David Morison

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Re: Sub design for a 18 Sound 12" subwoofer
« Reply #26 on: March 10, 2018, 05:24:32 pm »

150 people-no hiphop just country ,rock and roll and some pop

Tops will be EV ZLX12p or the like
One 12" bass bin will absolutely not keep up with 2 12" mains if you really want it to have some impact, I'd want one 15 or preferably 18 per 12" as a starting point.


Further to this, there's a forum member called Dennis Wiggins who has some experience using small 12" subs for (I think) the kind of usage you have in mind - here are a couple of threads in which he mentions his setup.

http://forums.prosoundweb.com/index.php?topic=164414.0
http://forums.prosoundweb.com/index.php?topic=165126.10

You may want to PM him for some direct experience of this size of sub, rather than trusting me.

NB, your driver appears more capable than the ones likely to be in the subs Dennis uses, so you may not need quite as many of them.
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Dave Jackman

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Re: Sub design for a 18 Sound 12" subwoofer
« Reply #27 on: March 12, 2018, 01:06:25 pm »

Looks reasonable. What does the simulation look like?

For what it's worth, bracing can be particularly effective when you join opposite panels. In subwoofer use, the forces acting on the panels will try to blow the cabinet up like a balloon, so physically connecting the opposite panels strengthens against that very well.

Chris

Hi Chris,
Forgive me but I have no way of doing a simulation on the driver/enclosure design. Can you enlighten me a little here.
Cheers,
David
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Dave Jackman

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Re: Sub design for a 18 Sound 12" subwoofer
« Reply #28 on: March 12, 2018, 03:13:12 pm »

One 12" bass bin will absolutely not keep up with 2 12" mains if you really want it to have some impact, I'd want one 15 or preferably 18 per 12" as a starting point.

Tuning higher (by shortening the vent) tends to push the response up into a hump, which can sound unnatural due to it causing "ringing" around the tuning frequency - I've not experienced an example of it myself, only read a little about it, so can't predict how obnoxious it would be in any given case. Reducing box volume can mitigate this though - that would take you back towards the kind of smaller box I modelled earlier. Obviously, both raising tuning and reducing internal volume both cost you in terms of less LF extension.

Herewith the fEarful box with ports shortened to 20cm only in yellow (HPF increases to 42Hz, Power to 390W) and a 45l box tuned to 50Hz again wtih 42Hz HPF and power at 440W in violet.

Is there a schematic drawing of a sub box(es) that you are suggesting?I really want to try to have a box design that is similar to the one I posted-for ease of construction. My thoughts on this sub is that I just want to augment the low end a bit and take some of the lower-
end strain off the mains-nothing earthshaking, just a little more punch.
Thanks
David
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David Morison

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Re: Sub design for a 18 Sound 12" subwoofer
« Reply #29 on: March 12, 2018, 03:42:05 pm »

Is there a schematic drawing of a sub box(es) that you are suggesting?I really want to try to have a box design that is similar to the one I posted-for ease of construction. My thoughts on this sub is that I just want to augment the low end a bit and take some of the lower-end strain off the mains-nothing earthshaking, just a little more punch.
Thanks
David

I've started one, but haven't finished adding in the dimensions yet.
Externally it's 400mm wide, 430mm deep and 470mm tall, assuming construction from 15mm ply.

Here's the partial, I should get time to add the dimensions in tomorrow or perhaps Wednesday.
(It's one mm per pixel if you want to get an idea of the rest yourself.)

You should also know that calculating exact port lengths has a bit of art to it, not just science. The "standard" calculations all assume the rear end of the port is in free air, i.e. not built in against a box wall. Doing the latter makes the port appear as if it's longer than it really is and the extent of this virtual extension is subject to a bit of approximation. Therefore it's always recommended that a prototype is built, the actual tuning frequency measured and the port length adjusted if necessary before committing to a final build.

Meanwhile, those who know might also comment if they think my proposed bracing is in the right ballpark or not?
« Last Edit: March 12, 2018, 07:09:15 pm by David Morison »
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