My first Tuba

[BassAwdyO]

backloaded horn eh? Hmmmm...

I think I'm probably going to just go with the Tuba36 slim horizontal baffle as bill suggested and be over with it.

the way I see it is this.... my ears can hear only down to ~24hz so I want my sub to be as loud and clean as possible form there on up. Having extension down down below is really nice for like .01% of music/movies, but for everything else it just doesnt do anything. I really want to horn load the tumult. I'm tired of that lame 88db efficiency in a vented box. I dont care how deep it goes....

[BassAwdyO]

BTW the MCM will be here tuesday so I'll be done with the AutoTuba then.

And with regards to the Tumult horn, Floorspace isn't a concern here. As long as it can fit through the door and I can move it with the help of a buddy or two, I'm game. I have very cool parents. I'm sure some of you are jealous that your parents or wives dont let you get away with such things, but what can I say... I'm lucky

[paulspencer]

GM,

so you are suggesting either use the Tumult in a bandpass box for say 10 - 40 Hz or using it in a real loaded horn. If the latter, what kind of tuning would you go for and what kind of size would be necessary to achieve it?

This is not an idea I've considered for typical subwoofer drivers. If I understand correctly, it will extend the useable response downward rather than increase overall efficiency.

Do you think it's worth the extra size of the horn version when operating down that low?

[GM]

Greets!

Correct. Well, like most things, it depends. Since it has so much power handling/Xmax, you can tune it above Fs and EQ it, or since rooms tend to become sieves below some frequency, increasingingly 'bleeding off' the LF, tuning it somewhat below Fs will offset this somewhat. It has the advantage of better damping Fs, which will lower the system Qtc.

Size wise, it depends on the 'M' factor. In the good 'ol days the basshorn had to play up to several hundred Hz to keep the XO component values/size acceptable, so large, fairly fast expanding exponentials were used to keep length down at reasonably low distortion. Today this is moot and if the XO point is kept below ~120 Hz, our hearing acuity has rolled off enough that we're more interested in a good blend amplitude and damping wise than how low the distortion is. Indeed, most folks prefer some distortion down low so that it doesn't sound so 'dry'.

Anyway, ideally a BLH needs to be a very low flare rate hyperbolic, so a conical expansion is 'close enough' since it's going to be truncated well before the 'ideal' mouth expansion begins in earnest. The Tumult's mass corner is ~106 Hz, so assuming a ~aneochoic flat response to 16 Hz and an 80 Hz/4th order XO.........

L = ~300"
St = ~33"^2
Sm = ~1143"^2
Vb = ~1.02 ft^3

Excluding dividers/driver, net Vb = ~80.32 ft^3 if I did the math right, so won't be particularly cheap to build, and having such an acoustically small mouth will cause some out of BW 'ringing' that an XO won't attenuate, so either flaring the mouth or heavily damping its perimeter may be required, and of course this thing needs to be incredibly rigid.

As you shorten it Fc/gain goes up, smoothing the response a bit, but because it's getting progressively underdamped with increasing Fc, transient response suffers, while increasing it lowers Fc/gain, smoothing it, but becomes increasingly overdamped, improving transient response.

FWIW, I designed a modded 'Voigt' style pipe tuned to 19 Hz awhile back for someone locally, but AFAIK he's never built it so......

L = 240"
So = 2.694"^2 (actually terminates to a point)
SL = 464.533"^2
zdriver = 144"
vent = 12" dia. x 10" long
stuffing density = ~0.25 lbs/ft^3, though if the room 'bleeds off' too much extreme LF, then reduce it to get some peaking at Fp and/or tune it lower.

It 'only' has a ~flat aneochoic 90 dB sens. down to Fs with a ~16 Hz F3, and at ~22.55 ft^3 net definitely not small, but at least manageable enough to be a bit more flexible WRT shape/positioning than the BLH, which ideally needs to be a 'W' fold spread across the floor.

Whether either of these designs is justifiable depends on your available space, budget, performance goals. I've experienced a very efficient basement sized expo basshorn and it's quite thrilling, but so is a bunch of fairly cheap, low Qtc sealed subs spread across the front wall/floor junction to create an apparent 'wall of sound' if BW limited with an 80 Hz/4th order XO.

GM

GM

[BassAwdyO]

I wish I knew as much as you GM.....
But anyways thanks for the TL design.... I may build it sometime and if I do I'll surely let you know of the results.

Quick question for you GM....
Do you think I will be happy with the results if I build the Tuba36 slim horizontal baffle version?

[mwmkravchenko]

That means that with the corners you have to cut when trying to fit a horn into a realistic space it still performs. If you want to model a horn loudspeaker you can download the program called hornresponse. Take a cue from Bill's folding geometry. He didn't come up with it. It is in public domain. So if you designed one and folded it the same way you could end up with another good horn design.

If you wanted more low end you would have to do two things. THey both will drastically enlarge the size of the enclosure. Make it longer and make the overall taper larger.

Now I would say that the biggest design work that Bill did went into shrinking it down and still getting decent performance. The Hornresponse program is great for designing a what if scenario. Design one in horn response and start shortening it. Check the response. Downsize the mouth and check the response. I think you get the idea. Then bite the bullet. Either build Bill's design or if you feel that you have noodled around enough build your own.

Mark

[GM]

Greets!

You're welcome!

Study/experiment periodically for ~52 yrs like I have and with the powerful tools available today/future you'll probably know so much more than I'll ever know that in retrospect I'll seem like a rank newbie, especially if you're better at math/computers than me.

Not being familiar with either the design or what performance you expect of it, don't have a clue.

GM

[BassAwdyO]

I just want >100db sensitivity from say 30hz on up. If you'd like... I can buy you a set of the plans and you can look over them, a good opinion is worth $10 for sure!

[GM]

Greets!

Not sure what constitutes a 'slim' baffle, but just looking at the single driver SPL plot for a 30" wide baffle it's ~93 dB/30 Hz/half space, so I doubt it would hit 100 dB unless corner loaded in a small, well sealed room. If the 'slim' model is smaller, then its sens. will be even less for a given BW.

Anyway, the folks who've built them would be your best source of 'hands on' info, so what do they say?

GM

[mwmkravchenko]

THe SPL measurements are taken outside. So on the low end you can expect close to 10 db gain due to corner and wall loading. So you probably will end up with more than you hoped for.

BassAwdyO I doubt that the driver you have is at 100db/watt at 30 hz in any othet box. If you get around 90 db/ watt you will with the gain that you have allready noted ( about 10 db ) get to your goal.

My personal preference is to go with a dual driver configuration. You get another 3db real world output. That's the same volume with half of the power going in!

MArk