Thread: FREE SUB PLAN: Dual Lab12 (Front Loaded) by Welter Systems

Originally Posted by Klaus {nojunk} Zimmermann wrote on Thu, 27 January 2011 07&#58

Originally Posted by Chris Gruber wrote on Thu, 27 January 2011 04&#58

Is there a picture of one that is real?

art,
tx 4 all.

can yo show some pix from the port/tunnel? I'm still not shure HOW it looks... :blush:

The port is triangular.
The speaker grill would reduce the port area if it were not extended inward at a 45 degree angle.



The 13.1097 inch dimension of the port angle piece (port extension) is (most likely) correct at the angle point, but it should extend towards the speaker another 3/8'' inch or so, so it would be longer.

When making that part, I find it is easiest to cut long strips from scrap, then cut the 45 degree end angles to fit. Once you get one piece cut down to fit, just duplicate the rest.

It is also a good idea to round over the front side of the grill and speaker side of the port extension to reduce port turbulence at high volume.

A center brace could be added front to back between the cones. I did not have one in my cabinets, because I recycled some old cabinets and the jack plate was located in the middle of the back.

The handle position shown in the photo was also the result of re-use, it is a poor position for the cabinet.
I'd recommend pocket handles front and back, each side.
Anyway, it's just a ported box, don't get too hung up on details.
As long as the cabinet is airtight, made of good plywood, slight deviation such as handles and port termination won't make much difference.

I tested at least 8 different real boxes before deciding on this alignment.

If the port is a little longer, the response would go deeper, and loose some of the ''port bump''.

A little shorter, and the bump would go up in frequency.

I just noticed Seth drew the right port on the top, the cabinets I built have it on the bottom.
Makes no difference, but adds to the confusion :lol: .

Looking through some notes, found the Lab 12 requires 1 inch to the grill to cover full travel to Xmax, so definitely recess the speaker.

I'm left with two options now for a "easy" diy-project, either the 2x12" in this thread, or this: http://www.bcspeakers.com/PDF/SUGG/SGG_16.pdf

Is it possible to outline the differences in these two designs AKA low frequency extension, spl and frequency response?

Originally Posted by Helge Dr. Bentsen

I'm left with two options now for a "easy" diy-project, either the 2x12" in this thread, or this: http://www.bcspeakers.com/PDF/SUGG/SGG_16.pdf

Is it possible to outline the differences in these two designs AKA low frequency extension, spl and frequency response?

Helge,

That box is too small to take advantage of the LF capability of the B&C 21SW115 inch speaker.

The BC18SW115 puts out more LF in a “too small” box than the 21SW115.

The dual Lab 12 has almost identical low frequency output in a smaller box with the same Fb as the BC18SW115.

I did not save all the interim tunings, but have included the ones I did, all using the same drive levels.
The four ohm B&C is receiving a few less “watts” than the nominal 3 ohm dual Lab 12.
The BC18SW115-4, given twice the power, will get about 3 dB louder than the Lab 2x12.

But it takes a bigger box to do it.

The exterior dimensions of the box I used to test the BC18SW115-4 are 36 x 24 x 17 inch, 8.5 cubic feet compared to 7.76 for the 2x12. In all but the 38 Fb test, the magnet was outside the box, effectively adding about .56 of a cubic foot. That said, bigger is better (until Xmax is exceeded before Pmax) but the boxes are very close in volume.

The BC18SW115-4 with the 37 Hz tuning almost exactly overlays the Lab 12, were it not for the lower upper filter on the Lab 12 , they would look more identical.

It is plain to see that the 28 Fb box trades around 4 dB of 40 Hz output for being “flat” to 30, while in actuality puts out the same level at 30 Hz as the 35 Fb tuning.
Not a good trade, unless most of your sub output needs to be that low, which is why I chose an Fb of 36 for the Lab 12 design, and I’d do the same for the BC18SW115.

The BC18SW115 in the test box are pictured next to a box exactly double the size of the 2x12.
That box, the Keystone sub, is about 6 dB more efficient than the bass reflex designs using either the Lab 12 or the BC18SW115-4 with the same low corner.

I have one pair of the dual Lab 12s for sale, anyone interested can PM me.

Art Welter

Interesting. The 2x12 looks like a serious little subwoofer, it's tempting to build one.



Thanks

Originally Posted by Helge Dr. Bentsen

Interesting. The 2x12 looks like a serious little subwoofer, it's tempting to build one.

Thanks

same here, possible over the easter weekend

Funny - I did almost the same box for an install a couple years ago. Lovely sounding. Needs some gas to get it going though due to the driver being somewhat inefficient.

Sorry the picture's not the greatest

Art has designed a very carefully thought out box, with rare care applied to the port baffling which can make a big difference in sound quality and behavior at high output.

I bet with drivers that were designed for a reflex cabinet, instead of custom built specifically for a large horn, it would be a real performer.

Originally Posted by Bennett Prescott

Art has designed a very carefully thought out box, with rare care applied to the port baffling which can make a big difference in sound quality and behavior at high output.

I bet with drivers that were designed for a reflex cabinet, instead of custom built specifically for a large horn, it would be a real performer.

Drivers designed for bass reflex tend to have lighter cones, and may put out more in the upper sub range, but at the expense of low frequency distortion.

Super drivers like the BC18SW115 can put out more level given more power, but require a larger box to acheive the same sensitivity as the dual Lab 12.

So far, I have not seen any alignment using a low cost speaker that is capable of more LF output in a box as small.

Anyone considering making these cabinets as powered versions should check out this review:
http://www.soundforums.net/live/thre...0230#post10230
The Torpedo is a high quality, high power amp.

Optimized for low frequency use, it handles the nominal 1.5 ohm load of four Eminence Lab 12 without getting warm.

It does have plenty of power to heat up the speakers !

Art

Is there a way to use the Lab 15 drivers or would that pretty much entail starting from scratch? I know pretty much nothing of speaker design so I was curious if it would be worth it to use dual 15" drivers rather than 12".

Originally Posted by Justin Waters

Is there a way to use the Lab 15 drivers or would that pretty much entail starting from scratch? I know pretty much nothing of speaker design so I was curious if it would be worth it to use dual 15" drivers rather than 12".

That would be a completely new box. The LAB15 is a totally different woofer.

Originally Posted by Silas Pradetto

That would be a completely new box. The LAB15 is a totally different woofer.

Theile Small parameters-wise the Lab15 will do fine in this box, but it won't physically fit.

Originally Posted by Phil Graham

Theile Small parameters-wise the Lab15 will do fine in this box, but it won't physically fit.

Right, I didnt know if you could just increase the dimensions so the Lab 15 would fit, or if new port lengths and sizes as well needed to be calculated.

Originally Posted by Justin Waters

Right, I didnt know if you could just increase the dimensions so the Lab 15 would fit, or if new port lengths and sizes as well needed to be calculated.

If you change the volume of air in the cabinet, you will also have to change the port air mass. Also, as Art will attest, the port area of this box is marginal as is, and would have to be expanded to utilize a larger Vd driver like the LAB15

Originally Posted by Justin Waters

Is there a way to use the Lab 15 drivers or would that pretty much entail starting from scratch? I know pretty much nothing of speaker design so I was curious if it would be worth it to use dual 15" drivers rather than 12".

The Lab 15 requires a larger box and more power to put out almost the same amount of low frequency as the Lab 12. Not as good a choice in my opinion.

My apologies to Art. I was going to build some 2x12"s, but I got sidetracked and ended up with two labsubs, and six more under construction.

Originally Posted by Helge Dr. Bentsen

My apologies to Art. I was going to build some 2x12"s, but I got sidetracked and ended up with two labsubs, and six more under construction.

No apology needed, if I could afford the trucking and storage and could fit multiple huge, deep FLH cabinets in the venues I work, I'd use them too.

You can fit almost 24 of the front loaded dual Lab 12 in the same space as 6 Labsubs, but unlike a FLH, you only need one to have full frequency response.

Hey all,

Good to see the design files still floating around... I regretably lost most of the CAD work in a poorly-backed-up disk failure about a year ago, and stumbled onto this thread this morning searching around to see what was online when a friend was interested in the project.

It almost looks like what is posted is a mix of Art's original design (which was constrained to working with existing w-bins that were being converted, if I remember right) and the slightly modified version of his work that I built since I was going from the ground up. That might explain some of the errata. I was working on documenting both versions at the same time, but nearly two years ago now, so I can't remember which I might have posted/sent.

At any rate, I should hopefully have time next week to recreate the CAD documents if anyone would like them, but, if someone has the original DWG files (I can't remember if I sent those to Art, or just the PDFs) that would be a great base to work from. I'm sure I have the Bassbox Pro simulation files if those are of interest, too. They weren't lost when the drive let out its magic smoke...

FWIW, I've also built a half-size (single Lab 12) that is fundamentally very similar as it basically started out as building half this box, and tweaking the port design slightly. I'd be able to share that as well.

--Seth

I have some JBL 2206's laying around. How do you think the Dual Lab 12 would work with them?

Seth, I would be interested in your single Lab 12. Do you have that in a PDF file and/or photos?

Originally Posted by Chuck Simon

I have some JBL 2206's laying around. How do you think the Dual Lab 12 would work with them?

They are considerably different driver designs. For example, the fs of the lab12 is 22Hz, while it's 52Hz for the 2206. It will make noise, but you'll get very different, non-ideal response with the 2206's in a box that size. You'd be much further ahead to sell the 2206's to pay for a set of Lab12 drivers in this case.

Originally Posted by Chuck Simon

I have some JBL 2206's laying around. How do you think the Dual Lab 12 would work with them?

Seth, I would be interested in your single Lab 12. Do you have that in a PDF file and/or photos?

2206s aren't subs. Adrian Genovesio actually needs one for a speaker he's working on...PM him...