W12gti Mkii

[Slare]

I know this is a little bit out of the target here, but I recently picked one of these subs up on a pretty good local deal. I have high hopes for it to use as a very solid 12" compact home sub.

I have a ~550 watt plate amp (which may not be stable enough for this woofer) and also an older NHT studio subwoofer amplifier which should be fine for ~300 watts x2 rms into the 6 ohm coils. So power wise, I think I'm covered.

What I'm baffled by is that JBL recommends a 1.0 cuft sealed box for this thing (which is what it came with). Can this really be right?

Hooking the plate amp up I expected more out of the woofer, but I'm suspicious of the tiny box. Any experience with these out there?

[Hoerninger]

Others have experience, you will see. :)
____________
Peterhttp://audioheritage.org/vbulletin/attachment.php?attachmentid=33635&stc=1&d=1217791723

[toddalin]

I have a ~550 watt plate amp (which may not be stable enough for this woofer) and also an older NHT studio subwoofer amplifier which should be fine for ~300 watts x2 rms into the 6 ohm coils. So power wise, I think I'm covered.


Are you planning on using two of these in parallel or series? Each speaker runs at either 12 ohms (two 6-ohm coils in series) or 3 ohms (two 6 ohm coils in parallel). You do not run one channel into each coil as with a standard dual voice coil sub.

At 3 ohms, your amp may not be stable and probably can't be bridged to this load, unless it is intended for automotive duties. At 12 ohms, you won't have enough power to get any real volume out of it. (Maybe it could be OK bridged into 12 ohms if your amp can bridge.)

I run the W15GTi in a ported 4 cu ft cabinet and use a Crown PSA-2XH that puts out ~800 watts RMS bridged into the 12 ohm load.

[Slare]

The plate amp was intended to run at the parallel 3ohm loading but after some time it seems like the clipping auto shutdown gets more and more sensitive. I was worried about the low ohm loading causing this but that doesn't make much sense to me because the impedance of the driver should go up with heat. I guess the driver load is going up, the amp puts out less power, and thus clips/shuts down faster?

I've also read that the mkii may as well be a parallel 4 ohm load.

Maybe a ported enclosure and a high pass filter would fix it.

The NHT rack amp is stereo 4 ohm stable so I can run it in dual 6 ohm mode no issues. I really wanted to use the plate amp to keep total space limited, but I guess hiding the amp would be an option, too. About the coil configuration - I can't use the NHT amp to send two identical mono signals one channel to each coil? I don't ask to be difficult, but why not?

I'm typically just fine with sealed subs but what I really want out of this sub is maximum 20-40Hz SPL from the smallest manageable enclosure. JBL's ported box seems mangeable - anyone have plans or pictures?

It will likely end up paired with L5's if I can keep the box size manageable.

[toddalin]

About the coil configuration - I can't use the NHT amp to send two identical mono signals one channel to each coil? I don't ask to be difficult, but why not?

anyone have plans or pictures?


Though it may work, it is not the way JBL says to do it. I guess both channels would need to be pretty much exactly the same for it to work properly in this configuration, but ???

Enclosure is internally separated. W15GTi gets ~4 cu ft and a 4" dia x 13" port and 2235 gets ~6 cu ft and a 4" dia x 8" port.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Revised_Center.jpg

[baldrick]

I bought 4 of those for my sub project, put them in closed boxes of 1,5 cu ft and feed them by a Crown MA3600. After a few days I put them up for sale:( It did not play as good as I was hopeing so I sold them all.

I think W15GTI in a vented box is much better suited for home use than W12GTI in sealed.

[toddalin]

I bought 4 of those for my sub project, put them in closed boxes of 1,5 cu ft and feed them by a Crown MA3600. After a few days I put them up for sale:( It did not play as good as I was hopeing so I sold them all.

I think W15GTI in a vented box is much better suited for home use than W12GTI in sealed.

These are W10GTi's in ~1.25 cu ft cabinets. A small port would have helped as it makes a big difference.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/index_0101.jpg

[4313B]

I bought 4 of those for my sub project, put them in closed boxes of 1,5 cu ft and feed them by a Crown MA3600. After a few days I put them up for sale:( It did not play as good as I was hopeing so I sold them all.

I think W15GTI in a vented box is much better suited for home use than W12GTI in sealed.Once again... these are automotive transducers and are expecting an automotive environment.

While you can get them to work in a home they are expecting "room rise" to begin at ~ 50 Hz instead of much lower as in a home environment...

In other words, that graph in the image above is going to have a hole in the response below ~ 50Hz, not quite as "bad" as the dashed line but very probably "bad" enough. Just stick the subwoofer box in a closet and it should be ok (That's about the size of free air it's looking to fire into). ;)

If I remember correctly these drivers, when used like a typical home transducer, end up in weird vented alignments with huge volumes and tons of group delay. Alot of people wouldn't care, or notice, especially if they've never heard anything better.

[toddalin]

Once again... these are automotive transducers and are expecting an automotive environment.

While you can get them to work in a home they are expecting "room rise" to begin at ~ 50 Hz instead of much lower as in a home environment...

In other words, that graph in the image above is going to have a hole in the response below ~ 50Hz, not quite as "bad" as the dashed line but very probably "bad" enough. Just stick the subwoofer box in a closet and it should be ok (That's about the size of free air it's looking to fire into). ;)

If I remember correctly these drivers, when used like a typical home transducer, end up in weird vented alignments with huge volumes and tons of group delay. Alot of people wouldn't care, or notice, especially if they've never heard anything better.


Why not plug the T/S parameters of the W15GTi in a 4 cu ft box with a 4" dia x 13" port into the WinISD for all to see? I bet you would be suprised how smooth the curve is and how low this speaker can go with authority.

[grumpy]

... if someone wants to do this, make sure to compare group delay with
another non-automotive LF driver. May not be an issue for all, but you
don't get sumthin for nuthin.

[Robh3606]

... if someone wants to do this, make sure to compare group delay with
another non-automotive LF driver. May not be an issue for all, but you
don't get sumthin for nuthin.


Just drop in a 2235 to compare. Night and day especially in the same volume.

Rob:)

[toddalin]

Just drop in a 2235 to compare. Night and day especially in the same volume.

Rob:)

Was night and day that the W15GTi went lower, smoother than the 2235 when both in the same sized cabinets (4 cu ft) with the same port configuration. I posted that data here a few years ago.

Could not monitor group delay though.

[Slare]

In the tiny 1.0cft box I have the sub in (with acoustistuff) the sub actually "subs" quite well. It is every bit as loud as any commercial home sub I have heard in the ~$300 range and to my ears isn't a one note box at 40-50Hz like the free air response would suggest. I will admit that room is a nightmare though so I'm probably used to less than ideal response at my listening position. I can only qualify by saying it is not a fixed one note box like a Onkyo HTIB sub, there's lots of healthly output at 25-30Hz.

The bigger problem I have is my ~550 plate amp won't drive the 3 ohm load without clipping into protection shut down; it seems 4 ohms is really the hard limit for it. So I think the sub is going to find a new owner. I could use the NHT amp but by doing so I lose my stealth tiny install and the project becomes much less attractive to me at the moment. Bleh.

[Robh3606]

same sized cabinets (4 cu ft) with the same port configuration.

Hello Toddalin

Did you ever redo the ports?? They shouldn't be the same for those drivers. You should have tuned the W15 lower than the 2235 to get the most LF extension out of it. The group delay goes up but it always will when you lower the tuning frequency. If you look at them in the same box and tuned to optimize a 2235 the difference in group delay isn't as much but you are not getting the most out of the W15 if you do that. You also have a peak in the W15 response that tuning lower helps smooth out.

Rob:)

[toddalin]

Hello Toddalin

Did you ever redo the ports?? They shouldn't be the same for those drivers. You should have tuned the W15 lower than the 2235 to get the most LF extension out of it. The group delay goes up but it always will when you lower the tuning frequency. If you look at them in the same box and tuned to optimize a 2235 the difference in group delay isn't as much but you are not getting the most out of the W15 if you do that. You also have a peak in the W15 response that tuning lower helps smooth out.

Rob:)

Yes, I redid the cabinet since those data were obtained. The W15GTi now gets 4 cu ft and a 4" dia x 13" long port. The 2235 gets 6 cu ft and a 4" dia x 8" long port.

[4313B]

Why not plug the T/S parameters of the W15GTi in a 4 cu ft box with a 4" dia x 13" port into the WinISD for all to see? I bet you would be suprised how smooth the curve is and how low this speaker can go with authority.The W15GTi wants a 6.5 to 9.0 cubic foot box tuned to around 20 to 18 Hz based on its TS parameters whereas the 2235H is looking for 3.2 to 6.6 cubic feet tuned to around 28 to 22 Hz (Keele and Co state that the optimum for the 2235H is 4.5 to 5.0 cu ft tuned around 28 to 30 Hz and that ends up being time tested tried and true).

One can force it into smaller volumes when used in an automobile to get that desired very low frequency "bloom".

Note in the specs that JBL uses xmech for xmax. ;) Can't really blame them considering the crowd they are appealing to.

Comparison of 2235H (yellow) and W15GTi (red) in the ubiquitous 5 cubic foot volume tuned to 30 Hz. As we all know, this is a one-eighty from how Greg currently tunes all the home loudspeaker systems. Even the venerable 2235H comes up way too strong on the bottom end.

[4313B]

Retuning the 5 cubic foot box down to 22 Hz for the W15GTi (where it wants to be tuned in that volume) we get the following:

With respect to group delay, alot of people argue that group delay down that low doesn't really matter. Some engineers beg to differ and just don't go there anymore. Whatever floats your boat.

[4313B]

Here it is very well behaved in the 1.75 cu ft sealed box:

The fourth graph is with a 2nd order filter set at 80 Hz.

[toddalin]

This is also what my data showed when I did the SPLs at the cones and ports and added them in accordance with their area contribution. If you run 4 cu ft with a 13" long port, you get a nice curve on the W15GTi in a manageable sized box. You just need lots of power to get the volume.

The W15GTi certainly gives the 2245 (in a much larger box) a run for the money.

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=41856&stc=1&d=1253220048

[4313B]

The W15GTi certainly gives the 2245 (in a much larger box) a run for the money.:rotfl: Not for my money it doesn't, not by a long shot.

[Allanvh5150]

Interesting how there is no light and shade with auto subs verse pro. I have 4 2235's in my HT. they are in 10 cu ft boxes and sound pretty decent. I am currently building some subs for SR use with drivers that will remain nameless but let me say this: The cabinets are about 6 cu ft with an 18" driver tuned to about 24.5hz. They appear to be flat down to 23 and the 10db point is 17. Group delay is a bit high around 20hz but I will wait to see what the results sound like. I have the feeling they will make mincemeat of my 2235's....

Allan.

[4313B]

I have the feeling they will make mincemeat of my 2235's....Awesome! Sell the 2235H's and move on. :yes:

[Allanvh5150]

Trust me, that wont be happening! :)

[Allanvh5150]

Awesome! Sell the 2235H's and move on. :yes:

As I thought. The subs I have just completed use an 18" Blaupunkt speaker. Cheap as chips and can stroke about 4 inches by the looks. With 800 watts on 1 speaker they will out muscle a pair of 2235's without batting an eyelid. I would say that for HT use they would be quite impressive, however for music, the 2235's beat them hands down for sounding "musical". Auto subs are generally not known for being musical and these are no acception but for producing thump and moving air they work pretty well.

I will be keeping my 2235's. :)

Allan.

[Eaulive]

Others have experience, you will see. :)
____________
Peterhttp://audioheritage.org/vbulletin/attachment.php?attachmentid=33635&stc=1&d=1217791723

Is that a real JBL datasheet? :blink:
I never saw JBL, being a serious company speak of Watts RMS, is that the new strategy to appeal to the masses? :banghead:

[4313B]

Is that a real JBL datasheet? :blink:
I never saw JBL, being a serious company speak of Watts RMS, is that the new strategy to appeal to the masses? :banghead:"Car Audio Enthusiasts"... gotta speak their language to sell them the goods... gobs of power handling, xMax measured in yards, etc.

[Allanvh5150]

"Car Audio Enthusiasts"... gotta speak their language to sell them the goods... gobs of power handling, xMax measured in yards, etc.

The only time that Xmax comes into play is below the tuning of the cab. Produces lots of wind but next to no audio. Maybe someone should tell the car audio guys what a high pass filter is.....

[4313B]

Maybe someone should tell the car audio guys what a high pass filter is.....You'd have to draw a picture, none of them can hear anymore.

[Allanvh5150]

You'd have to draw a picture, none of them can hear anymore.

I fear that for some of them, a picture would not help that much.:D

[Eaulive]

"Car Audio Enthusiasts"... gotta speak their language to sell them the goods... gobs of power handling, xMax measured in yards, etc.

Oh yeah, I noticed already they love to look at their cones jumping out and about :D
Rubber surrounds that take half of the cone area :blink:

[Allanvh5150]

Having said that, I do have a 1000 watt Alpine system in one of my vehicles with the old style DDD, dual coil subs. It was designed more for Hi-Fi and not out and out thump.

Allan.

[Titanium Dome]

No question it's a world of its own and some fans are w-a-a-a-a-y out there. :beamup:

It also drives a lot of innovation and provides a rigorous, torturous test bed for things that ultimately benefit consumer and pro products. As noted in other threads, I installed a JBL system in my Chrylser's TC by Maserati, and it's a very compelling system at any output level and with any music.

No it's not as good as some of my home or office gear, but it's better than most of my friends' home or office gear–by a lot! A car is actually a very interesting and rewarding environment to work in when it comes to audio, as long as you deal with the realities.

The other thing about JBL auto sound is how much money it pumps into the corporation. We should never underestimate how health in one division buoys the entire enterprise.

[Eaulive]

It also drives a lot of innovation and provides a rigorous, torturous test bed for things that ultimately benefit consumer and pro products. As noted in other threads, I installed a JBL system in my Chrylser's TC by Maserati, and it's a very compelling system at any output level and with any music.

No it's not as good as some of my home or office gear, but it's better than most of my friends' home or office gear–by a lot! A car is actually a very interesting and rewarding environment to work in when it comes to audio, as long as you deal with the realities.

Right, a good car audio system can be an enjoyable experience for the driver and passengers. It's NEVER a good experience for those who are OUTSIDE the vehicle, especially those monstruous, awful sounding rattle boxes.

I mean, what's the point of building a system that is designed to provide music to others and that are completely unbalanced and to loud to be useful from the driver's seat.

That is beyond me. :blink:

[Allanvh5150]

I mean, what's the point of building a system that is designed to provide music to others and that are completely unbalanced and to loud to be useful from the driver's seat.

That is beyond me. :blink:

My car system can provide music for others but it does so at high quality. It does not produce 10-20 hz at levels so loud that the only sound that can be heard outside the vehicle is the sound of body parts and fasteners loosening themselves.

Each to thier own I guess....

Allan.