T48 stack

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jakkle21
Posts: 28
Joined: Sat Oct 30, 2021 1:47 pm
Location: Flagstaff AZ

Re: T48 stack

#61 Post by jakkle21 »

Seth wrote: Mon Nov 20, 2023 10:23 am I want to help you set this rig up and get it dialed in. Over several days, I've typed up really long responses for this thread, then chosen not to post them for whatever reason.
I am definitely still lurking around the forum, and I am absolutely interested in getting this all set up right and dialed in. Ive had a few much longer and in depth posts and replys typed up that Ive either lost or just not posted so I understand that.
I've mostly just been very busy with the "day-job", getting ready for winter and doing tons of neglected car repairs.
I've also been thinking about starting a new thread over on the "pro-sound" board, tockeepcthings more organized, and not fill up my build thread with too much unrelated tech talk, but havent gotten around to it.
I'm also still saving up for the plywood to build the second pair and I've most settled on a color (or two) to paint them
Tldr: I am very interested in and grateful for any help getting this system running better

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Seth
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Joined: Thu Sep 10, 2009 8:06 pm
Location: Sacramento, California, USA
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Re: T48 stack

#62 Post by Seth »

Instead of trying to put it all into one post, I'll trickle all I have to offer in little bits over a few days or weeks.
jakkle21 wrote: Sat Sep 23, 2023 2:34 am ...I set my limiter to just over 50V...
Set your limiter to 60V. I'm not sure how you went about setting your limiter. But just to be safe, here's a quick explanation of how to do it to properly protect your drivers. You don't have to have the whole system set up to do this, you can do it on your kitchen table with just the amp, Driverack, sinewave source, and a digital multimeter.
- Disable any highpass and lowpass crossover filters on the subwoofer channel
- Disable or turn off any feedback suppression functions
- Disable Subharmonic synth
- Disconnect the speakers
- Turn the amplifier gains all the way up
- Use an online tone generator (or or any other source) and play a 60Hz sinewave.
- Turn the source volume up until the clip indicator just lights up on the amplifier
- In the Limiter settings in the Driverack, turn "overeasy" off
- Set your digital multimeter to read AC voltage and place the probes to read voltage across the amplifier outputs
- In the Driverack Limiter settings, slowly reduce the threshold until the multimeter reads as close to 60 volts without going over. It won't matter if it's a couple volts below 60, if that's the closest you can get without going over.
- Once set, reduce the volume and rapidly flick it up again a few times and verify the voltage does not exceed 60V.
- Your limiter is now properly set to protect your drivers.
I tried my best to wall/corner load them, but was kind of limited by the layout, but over all I was happy with the placement.
Very cool and educational to get to experience that first hand
I'm happy to hear you've read the placement sticky and are practicing intentional proper subwoofer placement and deployment tactics. That really is a huge step in getting the most out of your system. However, it's unfortunate that for the most part, wall and corner loading are primarily effective for indoor venues. The reason is, for a boundary to effectively reflect a soundwave it must be at least one wavelength tall and twice that in width. Where indoors, walls and corners become floors and ceilings, average size boundaries outdoors do not extend and become ceilings. In any case, I like your placement too. It looks like an appropriate spot. And if bass coverage was mostly even throughout the intended listening area with the subs there, even better.

In looking at the photo, there's a couple obvious opportunities to improve your system. The first is simply to construct a V-Plate and use it every time you're able. The second one is another simple and inexpensive upgrade. Invest in a few budget speaker stands to get your JBL Eon's up and above the listeners heads. I have no experience with the specific brand in the link.

In the pic, I like that you have the two JBL's splayed inward. It should help in minimizing comb filtering when compared to splaying them outward. :thumbsup:

That's it for now. BTW, having experienced these two cabs, are you still planning to build the second pair? I hope so. That would be awesome! Just knowing another highly capable system exists out there in the world is oddly satisfying on my end.

Image
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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