THTLP Build

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Seth
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Re: THTLP Build

#31 Post by Seth »

ecut1 wrote: Tue Jan 18, 2022 2:49 pm Anyone every try making the chamber cover out of a spliced piece? I have a 12" x 60" scrap that I could splice to make my 18" x 25" chamber cover. Would the pressure be too much for a splice?

Give it a go. Splice it as mentioned in the plans, with the angled seam. You could add a strip of additional material along the seam, on the in-side of the part if you wanted peace of mind. But really, I don't foresee that chamber experiencing enough pressure swing to be an issue.


Also, is there any benefit to adding poly-fil to the chamber?

I wouldn't think so.
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

ecut1
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Re: THTLP Build

#32 Post by ecut1 »

The chamber plate was fairly easy to put together. I just dry fit the braces in place crossing over the seam then clamped the two ends. Tonight, I'll cut it to size and install it. I'll be able to get full size chamber braces on the sides and have minimal reduction in size on the bottom braces. However, I'm thinking the top chamber braces are going to have to be cut back pretty far. Another option I thought of would be to add a second layer of plywood to the majority of the top (inside the chamber) and skip those braces. Would this be an effective option or should I just cut the braces way back?

ecut1
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Re: THTLP Build

#33 Post by ecut1 »

This is what I ended up doing for chamber braces. I think it'll work just fine. I also drilled though the mounting plate and bolted the driver in with double nuts.

I had a couple hours last night to try it out for a bit. I have some new rattles in the room to chase down now! It goes noticeably lower than the TT's and there's much more "feeling" in the bass now. My kids just start laughing when they hear it, it's so ridiculously overkill with all three subs on. I'm going to move things around a bit tonight and see how well I can get it to sound without a DSP. I'm sure I'll be ordering the mini DSP for them though.
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AntonZ
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Re: THTLP Build

#34 Post by AntonZ »

ecut1 wrote: Fri Jan 21, 2022 12:51 pmI'm going to move things around a bit tonight
Save your back. Turn it up yet a bit more and things will start moving about by themselves.

ecut1
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Re: THTLP Build

#35 Post by ecut1 »

We watched some music videos last night and we were messing around switching between the THTLP and the two TT's. The THT seems to produce a much cleaner bass. One of the videos had a nice hip hop/rap bass line that when from a high bass to a mid bass to a low bass. The higher bass line and mid bass from the THT sounds so clear and pronounced compared to the TT's. Maybe the drivers in my TT's are getting tired?? Or is this a normal difference between the two?

JensToft91
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Re: THTLP Build

#36 Post by JensToft91 »

First thing that pop in to my head is a phase issue. If the TT's are not in phase, the bass notes will get slightly "elongated" as far as I've understood. All frequencies will then "hang", as one TT gets to the top of the sine wave, the other will get there slightly after. When the first one is on the way back down, the other one is just reaching the top.
Try one TT vs one THT, and see if the difference is there aswell. If it isn't, I think it's a phase issue between the TT's.

ecut1
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Re: THTLP Build

#37 Post by ecut1 »

I'll mess around with the phase knobs on the amps and see what happens. We were running both TT's together, I should probably try them one at a time. Honestly, it's something that I've never noticed until the THT was chugging away in the back of the room. WOW! :loler: I have a mic and a mini dsp on the way. It'll be interesting to get some readings on everything.

ecut1
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Re: THTLP Build

#38 Post by ecut1 »

The mic showed up tonight. I've never used one and I need to pick up an extension cord. This is measured from about 5 feet off the back wall. The graph has one line for each... TT1, TT2, THT, then all three together.
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JensToft91
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Re: THTLP Build

#39 Post by JensToft91 »

How wide are those TT's?
They are measuring more or less the same as the THT 🙄 the THT is just louder, as far as I can see

ecut1
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Re: THTLP Build

#40 Post by ecut1 »

They are 17" wide with 8 inch drivers. The THT sounds quite a bit louder though. I think I read somewhere that for every 10db it will sound or be perceived as twice as loud. I'm pretty happy with how all three of them work together though. I'm going to be setting up a mini dsp soon and messing around with them a bit more.

JensToft91
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Re: THTLP Build

#41 Post by JensToft91 »

What looks wierd to me, is that the TT's have a lower roll-off than the THT. Maybe it's a placement "issue" ?
It looks like your TT's is flat to 21 Hz or so.

Can you make a close-up measurement for me? Right in front of the horn mouth.

ecut1
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Re: THTLP Build

#42 Post by ecut1 »

Sure, no problem. Right now I can only get about 10 feet into the room. I'll measure it when the usb extension cord shows up.

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Bill Fitzmaurice
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Re: THTLP Build

#43 Post by Bill Fitzmaurice »

JensToft91 wrote: Thu Jan 27, 2022 9:42 am What looks wierd to me, is that the TT's have a lower roll-off than the THT. Maybe it's a placement "issue" ?
Anytime you're measuring in room the result is very much determined by the room, the speaker placement and the mic placement. For example: http://ethanwiner.com/believe.html

JensToft91
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Re: THTLP Build

#44 Post by JensToft91 »

Bill Fitzmaurice wrote: Thu Jan 27, 2022 10:17 pm
JensToft91 wrote: Thu Jan 27, 2022 9:42 am What looks wierd to me, is that the TT's have a lower roll-off than the THT. Maybe it's a placement "issue" ?
Anytime you're measuring in room the result is very much determined by the room, the speaker placement and the mic placement. For example: http://ethanwiner.com/believe.html
I'm aware of that - which is why I said, it could be a placement "issue". It's not an issue, that the TT'S go low. I just don't understand why it goes as low as the THT, considering, that the curves are very similar. It doesn't look like there's any big peaks or nulls in the 20-30 Hz area - the two responses are equal.

This doesn't have anything to do with believes, even though that's a great article. This is a measured response - and I'm asking directly for a close-up measurement to see if it really is the room that equals these subs.

My TT turns on like a switch at 28 Hz or so, no matter where I put it. And it shows exactly that, when I put the mic infront of the horn mouth. I know that's a wrong way to measure it - and it will gain more extension in-room.
But I expect them to show different responses, the THT rolling off slightly later than the TT - per design.
It certainly haven't failed me to use this method.

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Seth
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Re: THTLP Build

#45 Post by Seth »

Nice curves. But what about that awful dip?













What dip, you ask...












That dip! Crikey!
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Are you guys eating seal steaks and walrus burgers, or what! Brrrrr.
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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