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Discussion Starter · #1 ·
Hi all,

I came across a JL 12W7 for a very cheap price. I have it in my car now, but I'm pretty done with bass in the car.

I've made some recent posts about replacing my PB12 NSD with a PB13-Ultra, but was now thinking of a DIY build.

I don't have many limitations with space or budget, but wanted some help with ported vs. PR, what kind of amp and if the output could come close to equaling the Ultra.

Any help would be appreciated.

To save some time, here are the specs on my room and subwoofer:

Room: ~3600 cubic feet
23x13x7.5
Sub: 12W7-3

Free Air Resonance (Fs): 27.2 Hz
Electrical “Q” (Qes): 0.514
Mechanical “Q” (Qms): 7.807
Total Speaker “Q” (Qts): 0.482
Equivalent Compliance (Vas): 2.33 cu. ft. / 66.0 liters
One-Way, Linear Excursion (Xmax)*: 1.15 in. / 29 mm
Reference Efficiency (no): 0.249%
Efficiency (1W/1m)**: 86.2 dB SPL
Effective Piston Area (Sd): 84 sq. in. / 0.0542 sq. m.
DC Resistance (Re): 2.47 ohm
Nominal Impedance (Znom): 3 ohm
Thermal Power Handling (Pt): 1000W
Driver Displacement: 0.14 cu. ft. / 4.0 liters
Net Weight: 45 lbs. / 20.4 kg
 

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12W7s make excellent subs for music and HT. The Fs isn't as supremely low as some of the best dedicated HT drivers, but either way these things are excellent.

For such a large room, you probably can't expect much "room gain" on the bottom end so sealed probably is not the way to go unless you've got multiple subs. The rolloff of this driver in a sealed alignment is perfect for a car but too early for a home.

As far as Ported vs PR, it's essentially a wash. For starters, a vented sub will roll off 24db/octave and a passive radiator 36db/octave below tuning. Above tuning it will be essentially the same if tuned the same. However you really shouldn't be using any bass reflex HT sub below its tuning frequency. For music it's not a big deal but when it comes to HT there's always the risk of strong content bottoming the driver. So a high pass filter is necessary, regardless of which choice.

Passive radiators cost more than making your own vent; the biggest advantages being

- no chance of vent noise (however a well designed vent will not make audible noise either)
- easily changable tuning (if you select the appropriate PRs. CSS makes some that can be tuned externally)
- no internal air volume dedicated to a vent (hence a slightly smaller box)

As for tuning, you will have to factor in many things in this decision...

-clean output
-extension
-optimal damping
-optimal HPF frequency

What I would do is around 200L tuned to 17hz. A 2nd order HPF cented around 16hz will do. A slot Vent would be something like 10 x 3.5 x 41 inches or so. This will allow you to throw around 1000w at it for roughly 110-115db @ 1m Rolloff should be smooth towards 20hz and sharp below that.

The advantage of the passive radiators with respect to shifting around the tuning frequency is a big selling point. If you were to find one alignment lacking, another alignment would be as simple as adding or removing a small weight to the passive cone. I do feel confident however that the alignment I listed would work well. It's -3db at about 26hz and -6db at 16hz. Even with minimal room gain that would clean up a bit in a real room and the real problems would be room node/mode related rather than alignment related.

So on that note, personally, I'd say you're better off spending on a second 12W7 in a vented box than a single 12W7 in a passive radiator box. It's all your choice though and I hope you end up with a sweet sub :)
 

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Hello , and what a great choice in a driver. I have been a JL Audio fan for many years and my day job is custom car audio so I have a 13w7 in my truck. I am in the process of building dual 13w6 enclosures so I can do a .2 setup. I was looking at the 13w7 for a much cheaper build design than the fathom or gotham models. Now don't get me wrong, they are absolutley amazing! But for the price they should be. You can go a couple different routes on amps and box design. I am using a butkicker rack mounted amp, it is rated at 1000w at 4ohm and 1900w at 1ohm. The only reason I went with the 13w6 pair is because I fell into them through work for 130.00 for the pair. And I didn't want to have a GIANT box in my little room. This is more of a because I can that actual usage. Once I get a bigger room than these will be much more usable. Just keep checking around but I beleive the 12w7 you have built in the right enclosure and right amp will blow you away in your HT. Thanks...Kai
 

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Discussion Starter · #5 ·
Sorry, was away for the weekend. Thank you for the great responses. A 200L enclosure sounds like the way to go. I'll most likely go with a ported build for simplicity and classic looks.

I played around with WinISD last night and it was telling me to use a 4" port 4" long. This seems small to me? MikeP, you suggested a 6" port...how did you come up with that? I'm sure i'm not using WinISD properly.

H_Roark, what Ohm load are you running your speakers at? JL makes the W7's 3ohms. do you run at 4?


GranteedEV...winISD was telling you 110-115db at 20hz? So you're saying this will outperform the SVS-Ultra? i think the ultra is 103db at 20hz. Is this attributed to manufacturers not wanting to make subwoofers too large?

As far as amps...could you make some suggestions? Behringer amps any good? what about a Dayton amp from Parts Express? are they reputable?

Thank you again,

Andrew
 

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A 4" round port would need to be 13.5" long for a 17 hz tuning in 200 liters. The problem is the port airspeed is off the charts. A 6" flared round port would need to be 32.75" long for a 17 hz tuning in 200 liters and port air speed is acceptable at 30 m/s.

The sub is 3 ohms, the impedance graph shows it dips to 3.5 ohms at certain frequencies, a 4 ohm amp will handle that.

The SPL graph shows 112 db at 20 hz, that does not account for any room gain that you may also get.

Behringer and Dayton amps are good, the 1000 watt Dayton amp has a 3rd order subsonic filter built in, yellow is with the Dayton amp, a 18 hz tuning would be best for that amp. Orange is with a Pro amp like a Behringer and an add on unit that can provide a 16 hz subsonic filter. Most add on units are 2nd order which the modeling reflects.

jl12-7.JPG
 

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Discussion Starter · #7 ·
Thanks Mike, I definitely need a bit more work with WinISD.

32" is a lot of 6" porting. can I make 2 ports 16" deep? would prefer to build the box to those dimensions.

So with the Dayton amp I wouldn't need any other filters? Sorry...adding filters isn't something i know much about...something else to read up on!

Thanks again, the numbers look impressive...really seems to be on par or slightly edge out the PB13-Ultra.
 

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The Dayton amp has everything you need, install it and plug it in. For a 18 hz tuning a 6" round port would be 28.75" long, two would need to be 62" long each. If a single 6" round port is a problem then consider a slot port made from MDF.

Here's the project file for your sub. Save it to the "Projects" folder in WinISD.

View attachment JL 12w7 200 Liters 18 hz..wpr
 

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Yes I am running my w7 at 4ohms. At least for home use. In my truck it is at 1.5ohms. But after some testing I am going to run the dual 13W6's in a .2 setup. I'll have them diagonal from each other. I hope it will be quite impressive.
 
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