T39 dual 12 @ 29 wide vs single 12 @ 28 wide

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SethRocksYou
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T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#1 Post by SethRocksYou » Mon Mar 12, 2018 10:29 pm

Is there a chart that shows the response of the T39 in a single 3012 28" wide compared to a dual loaded 29" wide?

Looking at the chart below, just going from minimum width to max looks to be roughly the 6 more average dB I'd expect to see with a 2nd driver in roughly the same package. I'd like to see an overlay of the two if it exists.

Image

Thanks guys.

-Seth-

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Re: T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#2 Post by Grant Bunter » Tue Mar 13, 2018 4:43 am

28" wide is the new 30" wide. You can take say 1dB (maybe 2dB) off the 30" wide chart to get a 28" chart.
Adding an extra inch in cab width for a dual loaded will be almost insignificant, but add 6dB for the 2nd driver.
Going from 28" single loaded to 29" dual loaded is probably going to use up maybe another half sheet of 8 x 4 ply.
2 x single loaded 16" wide will beat the dual loaded 29" wide.

If you're going to up your driver count, you want to significantly increase your mouth area at the same time to get the biggest benefit.
And the moment you start dual loading you start having to manipulate impedance.
Just because you have a 2 ohm capable amp for example, doesn't mean that's where you want to run that amp.

By and large, dual loading is about maximizing cab count per amp channel, through series in cab and parallel cab to cab wiring...
Last edited by Grant Bunter on Tue Mar 13, 2018 11:43 pm, edited 1 time in total.
Built:
DR 250: x 2 (melded array) with March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...

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Bill Fitzmaurice
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Re: T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#3 Post by Bill Fitzmaurice » Tue Mar 13, 2018 6:55 am

Grant Bunter wrote:
Tue Mar 13, 2018 4:43 am
By and large, dual loading is about maximizing cab count per amp channel, through series in cab and parallel cab to cab wiring...
Gee, that seems familiar. Oh yeah, T39 plans, page 2: When considering a 2x cab keep in mind that two 1x cabs will have the same response as one 2x cab of twice the size, and that carrying two smaller cabs is a lot easier than one larger one. The main reason you’d use a 2x cab is to wire the drivers in series, for a higher impedance load. That allows using twice as many cabs per amp channel, which can be beneficial with a large system.

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Re: T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#4 Post by SethRocksYou » Tue Mar 13, 2018 2:12 pm

Grant Bunter wrote:
Tue Mar 13, 2018 4:43 am
28" wide is the new 30" wide. You can take say 1dB (maybe 2dB) off the 30" wide chart to get a 28" chart.
Thank you for the response grant. The two widths in question are the maximum for a single and minimum for a double, per the plans. The chart is just the best illustration I could find
Grant Bunter wrote:
Tue Mar 13, 2018 4:43 am
Adding an extra inch in cab width for a dual loaded will be almost insignificant, but add 6dB for the 2nd driver.
So, here's where the question comes up for me... Adding 6dB to the "wide" trace doesn't seem right. Wouldn't it be more like add 6dB to the "slim" trace? (Which essentially puts it very close to what the single loaded "Wide" trace is)

Other than the other points you guys made about balancing loads and maximizing cabs per amp channel, it seems, if the double loaded doesn't add much in the way of sensitivity, that it would only add 6dB on the top end. Is that about right?

Thanks guys.

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Re: T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#5 Post by Bill Fitzmaurice » Tue Mar 13, 2018 2:48 pm

Double loaded doesn't add power sensitivity compared to single loaded in the same width, because that's mainly the product of the mouth area. It adds 6dB maximum SPL by the doubling of the driver Vd.

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Re: T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#6 Post by SethRocksYou » Tue Mar 13, 2018 9:12 pm

That's essentially what I was getting at. Thank you Bill.

After rereading Grant's post, I think that's what he meant too.

Thanks guys

Richness
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Re: T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#7 Post by Richness » Sun Apr 15, 2018 6:47 pm

Good day. Just doing some Sunday reading and notice nearly everyone saying it's not a good idea to build dual loaded T39s. I disagree because it would take you much longer to build 2 singles than it would to build 1 dual. I built 2 dual loaded 30" and saved a ton of time and work since I didn't have to build 4 cabs to get the same result. So time and work here for me was a huge advantage. They are light and easy compared to the LS801s. So much easier to load and move (wheels). If you have the pack and carry space you get the same output with at least a week less work. Yea I am lazy but will be building another pair to knock down bottles in the bar.
2xT39 30'' 3012LF Dual
1xT39 38" 3012LF Dual

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Re: T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#8 Post by Grant Bunter » Mon Apr 16, 2018 3:03 am

Richness wrote:
Sun Apr 15, 2018 6:47 pm
Good day. Just doing some Sunday reading and notice nearly everyone saying it's not a good idea to build dual loaded T39s. I disagree because it would take you much longer to build 2 singles than it would to build 1 dual. I built 2 dual loaded 30" and saved a ton of time and work since I didn't have to build 4 cabs to get the same result. So time and work here for me was a huge advantage. They are light and easy compared to the LS801s. So much easier to load and move (wheels). If you have the pack and carry space you get the same output with at least a week less work. Yea I am lazy but will be building another pair to knock down bottles in the bar.
Not saying that at all!

We're saying don't build dual loaded cabs at the minimum width. Apart from time to build, there's no amazing output benefit (compared to 2 single loaded cabs 15" wide), so why do it?
The reason to do it is impedance manipulation to maximise cabs per output amp channel, and really that's about it.
So if you were going to do that, why wouldn't you also build to max width to maximise output?...
Built:
DR 250: x 2 (melded array) with March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...

Richness
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Re: T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#9 Post by Richness » Mon Apr 16, 2018 6:55 am

Good morning. Fair enough. I should have visited this before building my 30”s. The widest I could have possibly gone was maybe about 34”. I stand them on edges to fit both in my Honda Oddysey. What is the max width anyway and is there enough spl benefit to go even wider than 34”. I am planning to build another pair of dual loaded T39s. Thanks Grant.
2xT39 30'' 3012LF Dual
1xT39 38" 3012LF Dual

Grant Bunter
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Re: T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#10 Post by Grant Bunter » Mon Apr 16, 2018 3:31 pm

Richness wrote:
Mon Apr 16, 2018 6:55 am
Good morning. Fair enough. I should have visited this before building my 30”s. The widest I could have possibly gone was maybe about 34”. I stand them on edges to fit both in my Honda Oddysey. What is the max width anyway and is there enough spl benefit to go even wider than 34”. I am planning to build another pair of dual loaded T39s. Thanks Grant.
The max dual loaded width would be 55" wide all up for 12" drivers, or 39" for 10's.
Yes, there would be an output benefit beyond 34", and it would be significant, not just some, in a dual loaded cab.
It's moot though, you don't have the pack space.

Did you parallel wire your current cabs?
If you build another pair, you would need to series wire them plus your old ones, then parallel, for a pair per amp channel.
You would also then need an amp capable of over 100V/channel to run the cabs to max output...
Built:
DR 250: x 2 (melded array) with March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...

Richness
Posts: 19
Joined: Mon Dec 04, 2017 10:16 am

Re: T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#11 Post by Richness » Mon Apr 16, 2018 8:49 pm

Thanks so much for reply Grant. I measured the van again today and found out that I can add another dual 12 T39 at 36". Now u r making me think that is not wide enough and I should just pull the trigger and get a trailer and build another 2 or 4 single T39s at 26 or 28". :bash:

I wired the dual in Parallel. One Neutrix at 4Ohms. I don't have to worry about manipulating impedience because I am running each Dual Cab in Bridged mode on 1 Crown XLS 1500 amp. Specs-1550W @ 4 Ohms. I took the forums advice on limiting with the DriveRack as well at 55V. If I build 2 singles or 1 more dual then I would just get another XlS 1500. This was the best economical option for me.
2xT39 30'' 3012LF Dual
1xT39 38" 3012LF Dual

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Re: T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#12 Post by SethRocksYou » Mon Apr 16, 2018 8:57 pm

After rolling it all around in my mind, here's the conclusion I came to. I'll try my best to explain my thoughts. Sorry in advance if it doesn't make too much sense. Hard to put into words.

At essentially the same width, the thinnest double loaded will only outshine a full width single loaded in peak output. I wasn't seeing an advantage in the dual option when taking into consideration the tops I would likely use (OTop12's) wouldn't outrun the full width single loaded T39 option when the number of each cabinet balance sensitivities.

Example: 4 full width single loaded will be roughly 112dB average at 2.83v and should max out around 136dB (Average). OTop12's have the same voltage limit (with 3012HO's) and the roughly the same sensitivity AND peak output as the T39's when matched up 2:1 sub/top ratio. If we make that 4 double loaded cabs the sensitivities still match up well, but there's no use for the extra 6dB output... especially when the system is scaled to have ample headroom already.

I think, for my needs, I'd rather take advantage of the horn and let it do as much of the work as possible anyway.

Not sure that makes sense. Is that a thing, balancing sensitivities? Just makes sense to me. But, maybe it's just foolishness. Dunno

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Re: T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#13 Post by commander_dan » Mon Apr 16, 2018 10:56 pm

SethRocksYou wrote:
Mon Apr 16, 2018 8:57 pm

At essentially the same width, the thinnest double loaded will only outshine a full width single loaded in peak output. I wasn't seeing an advantage in the dual option when taking into consideration the tops I would likely use (OTop12's) wouldn't outrun the full width single loaded T39 option when the number of each cabinet balance sensitivities.

Dual option would hold an advantage in output over the same width single option when paired with OT12, because it would reduce the number of subwoofer cabs required to be built. I don't know how many T39's you're talking about here, but I would imagine it would actually be 2:1 subs:tops when comparing T39/OT12. I say this from my experience with T30's, that ratio is actually more like 3:1 because the T30 sacrifices sensitivity for extension. So, that means for this application, a pair of double loaded T39 would be a fairly even match for a pair of OT12s, just the same as a four pack of single loaded T39 of half the width would be the same match. Also meaning that a four pack of single loaded wider T39 would require more tops to take advantage of the extra output (a good problem to have!).. in my mind this give the ultimate advantage to single loaded wide cabs.. of course it depends on what the requirements and constraints are (packspace etc)

Example: 4 full width single loaded will be roughly 112dB average at 2.83v and should max out around 136dB (Average). OTop12's have the same voltage limit (with 3012HO's)

Do they though? I think you will find that they will start to break up long before you feed 55V worth of HF signal into them. IIRC I have brought mine up to breakup point and it occurs at around 36V, so have set limiters at 35V.. and that is stupid loud!

and the roughly the same sensitivity AND peak output as the T39's when matched up 2:1 sub/top ratio. If we make that 4 double loaded cabs the sensitivities still match up well, but there's no use for the extra 6dB output... especially when the system is scaled to have ample headroom already.

yes, meaning you would need more tops to balance the system

I think, for my needs, I'd rather take advantage of the horn and let it do as much of the work as possible anyway.

Not sure that makes sense. Is that a thing, balancing sensitivities? Just makes sense to me. But, maybe it's just foolishness. Dunno
Built:
6 T30 (24", 3012LF)
2 OT12 (MA, 3012HO)
2 T24 (18", 3010LF)

Running:
DCX2496
XTi 2002
XTi 4002
TRAKTOR Z2
TECHNICS 1210 Mk5's

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Re: T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#14 Post by SethRocksYou » Tue Apr 17, 2018 8:51 pm

Bill Fitzmaurice wrote:
Tue Mar 13, 2018 2:48 pm
Double loaded doesn't add power sensitivity compared to single loaded in the same width, because that's mainly the product of the mouth area. It adds 6dB maximum SPL by the doubling of the driver Vd.
Thought about this a little more...

Wouldn't a 6dB max SPL increase be achieved by doubling the count of same sized cabs? Where a double loaded 29" wouldn't match the output of 2 singles at 28". Could/Would it be that a 29" double might only have a 3dB peak advantage over the single 28"?

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Re: T39 dual 12 @ 29 wide vs single 12 @ 28 wide

#15 Post by Think » Mon Apr 23, 2018 1:09 pm

Bill Fitzmaurice wrote:
Tue Mar 13, 2018 2:48 pm
Double loaded doesn't add power sensitivity compared to single loaded in the same width, because that's mainly the product of the mouth area. It adds 6dB maximum SPL by the doubling of the driver Vd.
Which you only get when doubling the width of the box?

The graph in the first post shows that a 30" sub with 1 driver, will put out more spl at 50-60hz then 2x 16" slim subs.

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