Small ported 12 for PA use

[chips and palsa]

Hello everyone! this is my first post on the site an after some looking I could not find what I hope to be a relatively simple answer.



I am building a large 24 x 45 x 18 (BFM Tuba45) folded horn LAB12 Loaded Sub for PA use. However, I'm sure I'll realize that for the occasional house party, it will NOT be needed.



I would like to build a small but potent ported 12 for a few reasons:

-much smaller than a horn loaded box and easier to move (even the smallest BFM sub - Tuba24 - is still 24 x 24 x 16 and only plays down to 45 Hz)

-still flat to mid 30's (DJ use; house/trap/dubstep)



I don't need anything in the 20 Hz region so this would definitely be considered more of a PA build than a HT build. Therefore, if I can sacrifice that EXTREME low end for a little less box volume, I'm all about it!



Last notes, I have heard that the LAB12 is an excellent driver that can handle a beating, but since I wont be horn loading in this case, should I opt for a more efficient 12? (LAB is something like 89 dB sensitive) I have heard that the LAB makes a hell of a lot of nice noise when you throw enough power at it in a small boxes and powering it wont be a problem.



I will be driving it with the same QSC GX5 that I run the rest of my system with.



THANKS FOR THE HELP GUYS!!!

[Sydney]

Re: Small ported 12 for PA use

...I am building a large 24 x 45 x 18 (BFM Tuba45) folded horn LAB12 Loaded Sub for PA use. However, I'm sure I'll realize that for the occasional house party, it will NOT be needed.

I would like to build a small but potent ported 12 for a few reasons:

-much smaller than a horn loaded box and easier to move (even the smallest BFM sub - Tuba24 - is still 24 x 24 x 16 and only plays down to 45 Hz)

-still flat to mid 30's (DJ use; house/trap/dubstep)

I don't need anything in the 20 Hz region so this would definitely be considered more of a PA build than a HT build. Therefore, if I can sacrifice that EXTREME low end for a little less box volume, I'm all about it!
... should I opt for a more efficient 12? (LAB is something like 89 dB sensitive) ...

I don't know if you have compared the PE woofer selection guide and examined the 12" woofers. There are at least 55 models.
Comparing them will show the compromises involved.
As a consequence of Physics ( expressed by concepts such as Hoffman's Law ): To get low response and High output a box has to be big.
By far the majority of woofers used in Pro Sound are designed with high output and do so by sacrificing LF output.
To get

flat to mid 30's

forces a certain cabinet size range that isn't small without accepting a compromise elsewhere.

I.M.O. A single bass module that handles the bottom 2 octaves and 2 small boxes that handles the upper 8 octaves is a more practical approach

[billfitzmaurice]

Re: Small ported 12 for PA use

The Lab 12 sensitivity in a ported box isn't adequate for pro-sound use. Take a look at my Simplexx 15 Sub for as small a sub as it makes sense for with pro-sound. Anything smaller just won't hack it, Hoffman's Iron Law won't be denied. However, I believe once you hear the T45 you won't want to settle for anything less.

[chips and palsa]

Re: Small ported 12 for PA use

Sydney, I'm feelin what you're saying about Hoffmanns iron law. In this occasion I would be willing to give up the efficient option for low and small since I would still have 500w to drive it with. I'll check the comparisons!

And hello again Bill! I've gotta say, having built the AutoTuba I've become rather snooty when it comes to horn loaded over BR boxes =) this occasion is the only exception since the application would be for a small house party where the T45 would be extreme overkill. However there is a chance I'll overcome the hauling gripe for sound quality. I'll look into that Simplexx some more.

[Sydney]

Re: Small ported 12 for PA use

Sydney, I'm feelin what you're saying about Hoffmanns iron law. In this occasion I would be willing to give up the efficient option for low and small since I would still have 500w to drive it with. I'll check the comparisons! ...

With the 3 variables in the design; there is flexibility.
There was no mention of size range in your original request, nor form factor or implementation.

I built a T24 ( back around 2006? ) and you are "fairly" correct about the LF response.
It is not small ( from 4. 5 - 6 cu ft ) and is unwieldy.
( The T45 you mentioned is approx. 12 cu ft. )

Consider the size of the driver ( Sd ) and it's output capability can be calculated.
An advantage a larger driver has is the much larger piston area; so a larger driver has to move less distance to generate the same SPL. Intrinsically less distortion produced.
To get the same output at 35Hz as at 70Hz the driver has to move 4 times as far.
Again modeling will show the limits of a 12" piston @ 35Hz.
Presuming that this design will have to be elevated to ear level or higher; raises the logistics issue of lifting and supporting a cab with a 12 large enough to support 35Hz at acceptable SPL.

There are plenty of 12" High sensitivity Mid Bass Drivers that work in small boxes ( approx 1 cu ft ).
A good 18" in a 6 cu ft box has a greater Sd that 2 12" drivers.
So a 3 piece modular system would occupy approx 9 cu ft with greater sensitivity and superior performance than a "traditional" 2x PA box.
Before dismissing sensitivity; consider a driver that has a 6db advantage will use 1/4 the power. Less power used - less wasted on heating a voice coil and less risk of damage.

[billfitzmaurice]

Re: Small ported 12 for PA use

the application would be for a small house party where the T45 would be extreme overkill.

You can never have too much bass.

[Cuppa Joe]

Re: Small ported 12 for PA use

You can never have too much bass.

Damn! You beat me to it....

[chips and palsa]

Re: Small ported 12 for PA use

Wow, after looking at a pair of 12's again I realize I'm asking a lot from one of those. An interesting point was brought up about less distortion from less cone movement so a 15 is an attractive option over a 12. I have actually been considering using the AutoTuba!

How does corner loading work with BR boxes, less improvement or the same compared to horns?

[Cuppa Joe]

Re: Small ported 12 for PA use

Wow, after looking at a pair of 12's again I realize I'm asking a lot from one of those. An interesting point was brought up about less distortion from less cone movement so a 15 is an attractive option over a 12. I have actually been considering using the AutoTuba!

How does corner loading work with BR boxes, less improvement or the same compared to horns?

I corner-load my 1x15" DIY home stereo subwoofer, driver facing the wall, & it performs better than other placements I've tried; however, room modes still come into play. Regardless, it's no match SPL-wise for a properly designed horn sub!

[Sydney]

Re: Small ported 12 for PA use

...How does corner loading work with BR boxes, less improvement or the same compared to horns?

http://www.prosoundtraining.com/site/author/pat-brown/how-boundaries-affect-loudspeakers/

Bass Bromides aside - There can be Too much at ANY frequency ( feedback, noise pollution, etc ) :p

[billfitzmaurice]

Re: Small ported 12 for PA use

I have actually been considering using the AutoTuba!

Corner loaded it may be adequate. Just watch out for over-powering it.

[chips and palsa]

Re: Small ported 12 for PA use

Corner loaded it may be adequate. Just watch out for over-powering it.

Makes sense, this will give me a chance to set up the limiter on my PX. When finding a voltage limit, can I take sqrt(continuous power x impedance)? Not sure if the 250W from my drivers TS specs is thermal or mechanical

[joeybutts]

Re: Small ported 12 for PA use

I would still want 20's playing that style of music.....but that's me, basshead for reals. :D

[Cuppa Joe]

Re: Small ported 12 for PA use

http://www.prosoundtraining.com/site...-loudspeakers/

Bass Bromides aside - There can be Too much at ANY frequency ( feedback, noise pollution, etc ) :p

Well, OK then.... You can never have enough GOOD bass.

[Sydney]

Re: Small ported 12 for PA use

Well, OK then.... You can never have enough GOOD bass.

haha
Unless it causes structural damage or a pneumothorax

http://news.bbc.co.uk/2/hi/health/3614180.stm

:eek: