2 25" Lab 12 loaded T39s for a ballroom

[shane2943]

Hey y'all. Thought I'd toss up a thread to track the progress of the new T39s I'm building for a local ballroom. I'm not very far into the process but will add images and such as I go.

I opted for the Lab 12 because these will be stationary and not moved much or at all. So weight really isn't a concern.

[shane2943]

Also, is this a decent deal?

https://www.ebay.com/itm/387481604887?c ... d_source=1

[Bruce Weldy]

Also, is this a decent deal?

https://www.ebay.com/itm/387481604887?c ... d_source=1

Something feels fishy about that......new PA2s are over $500. Fake maybe? I haven't heard of those being faked, but at $200 under MAP pricing.....hard to believe. I'd ask a bunch of questions before sending $$$.

[shane2943]

Something feels fishy about that......new PA2s are over $500. Fake maybe? I haven't heard of those being faked, but at $200 under MAP pricing.....hard to believe. I'd ask a bunch of questions before sending $$$.

Good call on that. Perhaps looking for a used one would be a better bet.

[shane2943]

Got the baffles and reducers installed along with panels 3 and 4. The straps are there to help correct a little bit of warping that occurred. So far so good.

[shane2943]

Perhaps this would be a better question for the Amps forum, but what would be a decent budget amp to run these two T39's with the LAB 12's?

Would a used Crown XLS1500 be enough? The ballroom does already have an old QSC 1400 which I did test and it works. Not sure if that would have enough nuggets to power these to decent levels without clipping.

Would it be a good idea to use the QSC first and just brick wall limit it with the driverack and see if it's enough for the time being?

[Tom Smit]

Would it be a good idea to use the QSC first and just brick wall limit it with the driverack and see if it's enough for the time being?

I think that would be a good idea as it will likely be plenty since you won't be doing concerts in there. LOL.

[Bruce Weldy]

Would a used Crown XLS1500 be enough? The ballroom does already have an old QSC 1400 which I did test and it works. Not sure if that would have enough nuggets to power these to decent levels without clipping.

The QSC 1400 is underpowered. I've been running two T39s each off of my three XLS1500s in bridge mode for about 10 years.

You could certainly start with the QSC to give it a try - it will top out around 40 volts. So, while setting your limiter based on output voltage, I'd be watching the input light to be sure it's not getting over-driven at the input stage.

[Seth]

You can absolutely start with the QSC. It'll be down about 3dB in terms of peak output potential, which isn't much. Depending on the volumes you find yourself running, it may be plenty. As a matter of fact, if you find it's not enough and that you're constantly on the limiter or into clipping, you'd be better guided to build another pair of T39's instead of upgrading the amplifier. Doubling the cab count would get you 6dB increase in peak output capability on the same amplifier and 9dB (nearly twice the perceived volume) when used with an amplifier upgrade too. Where an amplifier upgrade alone will only get you a 3db increase in maximum potential output, over the "underpowered" amplifier.

But really, you are likely going to be satisfied with the underpowered amplifier. And like Bruce said, I'd set the brickwall limiter in the DriveRack to just before the amplifier clips, not a specific voltage.

[Bill Fitzmaurice]

I expect the 1400 would be fine. Don't forget that the Lab 12 is 6 ohm, and these are for a ballroom, not a hip hop club.

[shane2943]

Fair points. Thank you everyone!

I'll start with the QSC, set the limiter on the driverack and go from there.

[shane2943]

More progress! Panels 5 & 6 and the P6 extension is installed and the driver cover flanges are in place. The braces for the flanges are not installed yet. The cabs are starting to look like something!

They're not perfect, but they should be solid once done.

[shane2943]

Got more done on the T39s. Got all panels except the second side installed. I have the horn mouth braces cut out (not pictured) and mocked up now. Need to file and router them, then I can permanently attach them. Now is the time to thoroughly check for and seal up any leaks before the second side goes on so will be doing that as well. But the construction is almost complete!

[shane2943]

Mouth braces installed!

Also went through all the glue joints and added more PL wherever needed to prevent leaks. There were only a couple spots. Squeeze out looks good everywhere else inside the cab.

[Tom Smit]

Looking good!