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As much as I love the "TL" sound, for your application, use the LAb12c sealed and dial in the boost you want.
Sealed will help prevent overexcursion below Fb.
Great driver, and an amp with enough power. Make sure you have enough volume, enough bracing, and thick enough boards for the baffle.
How big of a coffee table? The old Labhorn had 2 of these in a horn and is still the best bass I've heard.
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I bet a tapped horn would do wonders over a TL sub.
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Hey, Eggguy, I REALLY, REALLY, REALLY don't think you should build a TL sub!
What about Bill Fritzwhatevers Table Tuba? I think his prefered sub is the Lab12.
Will it fit under a 36 inch diameter slab top?
What you talkin bout buddy?
https://billfitzmaurice.info/TT.html
I know its silly but I would really like some reasons, not for argumentation but for agreement. For rationality
I fired off an email to Jerry about your inquiry. I'd be curious to see what he says.
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Quarter wave @ 23Hz ----> approx 12 foot TL. Couple of folds and you'll have a nice looking coffee table. Seems reasonable to me.
Nelson pass did it with some big woofers and sonotubes.
https://passdiy.com/project/speakers/the-legend-of-el-pipe-o
That would be an awkward coffee table.
Something like this
That's one cool looking coffee table. Go for it. Oh, wait, we are supposed to talk you out of it. OK, never mind.
From Jerry-
Not sure 3 diameter is enough for a tapped horn. Please look at the PAL sub. I have built two of these and they are great down to about 40 Hz but below that they run of steam pretty fast and they are larger than 3 ft diameter.
https://www.diyaudio.com/community/threads/325-lab-12-based-pa-tapped-horn-35hz-extension.232219/
I would go with a passive radiator vented design.
McJerry
InDIYana Event Website
I think I would tend to agree with Jerry in this case. To get low, you are better off doing a dual PR design with these in the volume you are shooting for. A pair of RSS315PR, a pair of CSS 12" PR, or a single RSS390PR would likely do the job.
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OK, one of the potential problems with a TL sub would be with selecting the right xover point. A long TL will have resonant peaks somewhere in the 60 to 200Hz region, depending on the overall length. If you try to fix this problem by over-dampening the line with lots of stuffing, you will end up choking off much of the deep 30-40Hz bass output at the terminus. Your TL drawing looks like a tapered 8 ft line. The tapering will help to spread out the much higher mid bass peaks and dips above 500Hz, but the main 8 ft distance problem will remain intact. 1130/8 = 141Hz / 2 = 70Hz. So, depending on your xover frequency, you may run into a problem navigating around the 70Hz line mode. Food for thought.
So here is how I do it. I add up the straight sections and curved sections and a little bit out the terminus for end correction due to acoustic impedance mismatch and if there is a flare, half of that flare belongs to the line. 13560 divided by line length and the correction factor for a line with a taper ratio around 7 or 8 would be times .75 divided by 4 gives the fundemental. The first of the overtones that occur at odd harmonics would be three times the fundemental but due to the taper it is pushed up in frequency considerably. An octave or more depending on the amount of taper. I know there is no free lunch but a taper between 5 and 10 seems to provide enough bandwidth for subs without overly attenuating the output at the terminus. and without using fiber or the multitaper headache. Please chime in because I like it. I like all you chimey chimers out there in speaker nerdville.
While I'm still talking and you guys are still listening, I went to a concert recently and the subwoofers sounded like total dog poopy but by the end of the concert I was almost accustomed to the poopy. Not sure if I will like passive radiator sound. Could be wrong.
You guys are listening?
Best bass I've ever heard was from multiple 18" slot loaded drivers in a small venue. Second best was at a Lindsay Sterling concert.
Also I plan to apply open celled foam sheet such as AB-4 foam to the curved areas and perhaps some of the staight walls to increase friction to the sound wave and therefore increase the effective line length if necessary.
Or I could just make a sealed box and flip the 30 Hz boost switch
I'm planning a sealed rss390ho paired with the spa250dsp amp to use the peq and go to town
Best behaved bass I've heard might be those Purifi drivers at Dakota this year. Talk about stop & start on a dime!
I'll load this driver and tapered sections into the Leonard Audio TL program and see what it looks like. Most of my modeling work on TL's, so far, has been with this program or with Hornresp. These modeling programs have given me a very good match to actual near field measurements, but ONLY when looking at the completely "unstuffed" line. If I add stuffing along the line, either light, medium, or heavy, then my near field measurements at the terminus no longer match the model. The frequency of the peaks and dips no longer match. And the SPL of the peaks and dips no longer match.
Probably the best thing to do would be to build a prototype of this tapered TL using a removable top panel. Then add stuffing and take multiple near field measurements. Add a very small amount of stuffing, then measure. Add a little more stuffing and measure again. Rinse and repeat. See if you can kill off the nasty resonant peaks and dips without killing off the deep bass output at the same time. Also take NF measurements of the woofer cone and add them to the terminus to see what the overall response looks like.
I was punching the data into the Leonard Audio TL program and noticed that I do not have enough info to set up the model. The drawing that you posted is only the top view. It does not show the internal height of the coffee table. From this top view alone, I can enter each line section length, but I cannot enter the width & depth (or cross sectional area) at the beginning and ending of each segment. What is the internal height of the coffee table?
15 inches
Here is the Leonard Audio TL SPL of your coffee table sub. I used an 8 section, tapered TL model of the coffee table, which covers all the twists, tapers, and turns. I used the published LAB 12C T/S spec sheet data in the model. The woofer is offset 7.75 inches down the first tapered line section. The entire line is stuffed at a rate of 1/2 lbs. per cubic foot, using the Bob Brines 2X stuffing fudge factor for the LA TL program. As best as I can recall, I think he used a 2X fudge factor to get satisfactory results, but I can't find the old diyaudio thread where this was discussed in detail.
With stuffing:
Without stuffing:
I printed and scaled your drawing and then used it as a basic reference to set up the model (see photo below for all the sectional breakouts). If this model is accurate, this would probably make for a great coffee table sub. Flat down to 30Hz.