BillFitzmaurice.info

Hi everyone.

So I decided to pull the trigger and get started on a THTLP build for my living room / home theater project. Space is limited, so I have to be smart with my design and therefor I purchased the LP version. My goal is punchy, precise bass with as much LFE possible without running into group delay issues. I wanted to follow all the recommended steps to get maximum performance, however importing two Dayton Audio rss390hf-4 15" drivers to my home country of South Africa is incredibly expensive given import costs, duties, etc, so I'll have to choose from locally available drivers. We dont have anything like a Parts Express here, so the options are chinese made "professional" style drivers or car audio.

My design has incorporated two of the 36" versions. I'd prefer not to have them 36" wide, as that means the bottom of my tv would be at least that high off the ground. I'd prefer to get it lower. I know they should be corner loaded for best performance (and I possibly have a solution for that if I can go with a slightly narrower cabinet without losing performance) but I obviously want the most low end extension I can get without losing too much of the available space in my living room. The space in between the two horn openings in the attached image are about 500mm, which is less than the prescribed 2.8ft / 850mm as detailed in this post: viewtopic.php?t=398

When it comes to driver choice, there are many posts on this forum stating the following:
Preferred driver T/S specs are fs 17 to 30Hz, Qts 0.3 to 0.55, Vas 100 to 320L, xmax no less than 9mm.
Drivers with fs on the high end of the range work best in narrower cabs, those with low fs are better in wider cabs.
Output is determined by xmax, so the longer the better.

That 2nd line caught my attention... I cannot find a locally available driver with an FS as low as the Dayton's 19, and when it gets even close to that, the QTS (damping) is way too little. It goes far over the recommended maximum of 0.55

After much research, the locally available brand who's 15" driver specs most closely match the recommended t/s parameters is Kicker Audio. I've narrowed it down to 3 candidates in order of highest to lowest XMAX.

https://www.kicker.com/app/tsparam/50CVX152.html
50CVX152
FS 26
QTS 0.321
XMAX 20.65mm

https://www.kicker.com/app/tsparam/43CVR152.html
43CVR152
FS 26.35
QTS 0.388
XMAX 17mm

https://www.kicker.com/app/tsparam/44CWCS154.html
44CWCS154
FS 25.55
QTS 0.5305
XMAX 16.1mm

Now finally, to my questions. (I know right?! )

1: Which of the listed drivers best suit my requirements, given the FS on all of them is on the higher end of the scale
2: As the FS is high, what exactly does "work best in narrower cabs" mean, given that I dont want to sacrifice low end output?

The driver Fs does not need to be 19, it needs to be between 17 and 30. Lower Qts is better than higher. The cab width is explained in the plans. Placing subs below a TV is a very bad idea. The low frequency output will vibrate the TV, the shelves and everything on the shelves. You also don't want two subs on the same end of the room. Determine the best location for the first via the subwoofer crawl (google it) then with both subs operating do the crawl again with the second sub. There's no reason to build two 36" wide cabs, with a pair of them 20 to 24" wide would suffice. Two 36" wide cabs would be sufficient for a 50 seat theater. As for group delay, that's an audiophool myth. Below 80 Hz you can't hear it. Above 80 Hz if you did hear it the speaker would be so totally flawed that you wouldn't be able to listen to it. 'Punchy' and 'precise' bass are also euphemisms used by audiophools. They don't define anything where acoustical engineering is concerned. Ask any audiophool what the correct acoustical engineering terms are for what they're trying to describe and the only sound you'll hear is crickets. As for driver sourcing, others in your area might be able to help, but we don't know where that is. You should complete your profile.

Thank you for the quick response, Bill. Great aftersales support! Well, I definitely dont want to be an "audiophool". I simply appreciate good sound. My current setup is an Anthem MRX 740 receiver in a 5.1 setup. M&K Sound LCR950 speakers all round and the subwoofer is a Bowers and Wilkins PV1D which I borrowed from a friend. My hope is to use this THTLP build in order to replace his subwoofer. It performs well, but it's output is not enough for what I'd like. The room is 14.5ft by 13.8ft with an 8.4ft high ceiling and and it opens into a large open plan area on one side. Integrating the subwoofer into the tv cabinet was my attempt at utilizing the space as efficiently as possible. I am familiar with the 'subwoofer crawl' process, but as you can see from this top down view, there really isn't any other place the sub can go other than my front wall, due to the size and layout of the couch. I suspect that it means I'd have to look at a single 15 or 12's?

Even a small TableTuba will crush that PV1D, any of the full size TableTubas even more so, while a THT is to the PV1D as an Abrams tank is to a Mini Cooper. For the smallest footprint place them upright. I only use one TableTuba 2x4 and it's plenty.

Bill Fitzmaurice wrote: ↑Thu Jul 03, 2025 10:52 am ..while a THT is to the PV1D as an Abrams tank is to a Mini Cooper.

Absolutely!

Bill Fitzmaurice wrote: ↑Thu Jul 03, 2025 7:04 am 'Punchy' and 'precise' bass are also euphemisms used by audiophools. They don't define anything where acoustical engineering is concerned.

If we were to describe the performance of the Tubas/Titans technically correct, how would we do that? I've not been able to find the words to do them justice for someone who hadn't experienced them.

Arcane wrote: ↑Thu Jul 03, 2025 10:24 am ..there really isn't any other place the sub can go other than my front wall, due to the size and layout of the couch..

Do you already have the couch and cabinet in the image? Could you ceiling mount the sub?

Hey Keryn.
The attached image is a rendering of my current setup. My idea was to turn the room, as putting a THTLP in the front wall of the current layout, takes away too much of the room length, making it feel cramped. I like the table tuba as a space saving idea, but the wife doesn't like a cable running to it over the carpet to the center of the room and I dont think there's space anywhere else for it. That's why I settled on the THTLP. Dont have u-shape couch yet. That was the plan as my wife wants to make the area a bit more 'cozy' and she feels it'll be more inviting. I'd like to incorporate her wishes and a theatre. Not an easy task! Im not opposed to removing the window on the right and sinking the sub into it, to save even more space. It was an outside window, but an additional room was built onto the house, so it wont be a problem if it goes. One of my early ideas was to wall mount and down fire the THTLP so the sound comes from below a floating wall unit. I'll attach an image of that as well.

It seems you haven't looked at the TableTuba Longstyle, Table Tuba Two by Four and the two Small TableTuba options. I see three corners where upright placement would work, not to mention end table placement.

Arcane wrote: ↑Sat Jul 05, 2025 8:10 am The attached image is a rendering of my current setup.

It's great you've taken the time to create these images, makes it so much easier for us try to help!

Arcane wrote: ↑Sat Jul 05, 2025 8:10 am ..Dont have u-shape couch yet.

If you are set on choosing the THTLP, the cabinet could form part of your desired U shaped couch, l also suggest you consider the other smaller HT sub designs if space saving is a high priority, the THTLP form is a proper tank of a sub as Bill mentioned, you may not need all that power. We have an 8" Autotuba in our upstairs 3.1 HT in a room slightly smaller than the one you picture, and it outperformed an 11" bass reflex sub at half the power setting.. with a substandard driver! We also keep a 20" LAB15 THT downstairs for nuclear warfare

Arcane wrote: ↑Sat Jul 05, 2025 8:10 am ..I like the table tuba as a space saving idea, but the wife doesn't like a cable running to it over the carpet..

How expensive is your carpet? You could make it wireless, by running the wire underneath by way of tactical incision

The TableTuba doesn't have to be "coffee table", it can be placed in a coner as well (or along a wall).

Keryn O'Shea wrote: ↑Fri Jul 04, 2025 5:25 pm If we were to describe the performance of the Tubas/Titans technically correct, how would we do that? I've not been able to find the words to do them justice for someone who hadn't experienced them.

It's really a difficult thing to do without resorting to some of the common industry phraseology like punchy. In my opinion, with DSP now-a-days you can pretty much tune any response curve into any cab, within it's designs response limitations. Where the phraseology could be better used to describe the natural, native, non-EQ'd sonic signature of one cab compared to another. With DSP, they're all "punchy".

What set's Bill's horn designs, and all well designed horns apart from direct radiator subs when it comes to sound quality is the lack of audible distortion. I used to think my direct radiator subs were "clean". But, after experiencing a horn sub the difference is blatantly apparent. If you can close your eyes and point to the general direction of a subs location, you're hearing audible distortion.

With all the subs you've made, I'm certainly not pointing this out like you don't already know. It's really the only way to relate to someone who has never heard it themselves, "technically correct(ly)"

Another thing to relate to people that have never heard one is their sense of what is loud, is usually based on when it starts to sound even more distorted. Distortion = loud to most who don't know any better. We've had tons of people over the years say they (whatever design they built) don't sound as loud as the direct radiators they used before. They usually have to measure the SPL to "see" it and understand that the Titan/Tuba is, in fact louder. But, since it plays clean, it doesn't "sound" loud. That's usually a monumental turning point in their audio journey. After that, all they hear at any venue not using horn subs is the distortion. Once they hear what they didn't know they were hearing, they never forget.

That's pretty much the only technically correct way to relate the experience I've been able to come up with... other than being capable of creating the same volume level as a 2x18 direct radiator cab on a 1600 watts with only two 15's on 50 watts each (V-plated 36" T48's). That always says something.

Seth wrote: ↑Mon Jul 07, 2025 8:15 pm What set's Bill's horn designs, and all well designed horns apart from direct radiator subs when it comes to sound quality is the lack of audible distortion.

Right there.. that's it!

Seth wrote: ↑Mon Jul 07, 2025 8:15 pm ..But, since it plays clean, it doesn't "sound" loud. That's usually a monumental turning point in their audio journey. After that, all they hear at any venue not using horn subs is the distortion. Once they hear what they didn't know they were hearing, they never forget..

I've witnessed that moment many times when demonstrating Bill's cabs, it looks like this

Seth wrote: ↑Mon Jul 07, 2025 8:15 pm ..being capable of creating the same volume level as a 2x18 direct radiator cab on a 1600 watts with only two 15's on 50 watts each (V-plated 36" T48's). That always says something.

We'll be spreading those words over here soon, looking forward to that!