Auto/truck tuba designs

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Benflitv30
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Auto/truck tuba designs

#1 Post by Benflitv30 »

Was doing all the reading and searching I could on the different BFM auto sound focused designs here in the forum.

My intension is to build the most authoritative option I can, in one single cabinet. That seems to be a dual loaded version of either the auto or truck tuba built as wide/deep as the plans allow.

Do I ‘lose’ any performance by using the dual driver trucktuba design I’ve seen here with the cones exposed? Like the THT I’ve built, I thought the folded horn became more ‘efficient’ by having the driver enclosed within the cabinet with the back of the driver being sealed so to speak.

Is the only real trade off to folded horns vs direct radiators being the additional size of the cab needed?
The push back I get from conventional audio guys is that amp power is very cheap these days, so why sacrifice the space. If the only drawback is space needed for a folded horn, yet outperforms direct radiators in all other aspects, especially the harmonics and transient response, seems like a no brainer to build the horn.

I just want to build one cab and be done with it. These questions are all for the sake of measuring twice and cutting once and having a better understanding for the naysayers I encounter.

Thank you.

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Bill Fitzmaurice
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Re: Auto/truck tuba designs

#2 Post by Bill Fitzmaurice »

Benflitv30 wrote: Mon Jan 04, 2021 3:27 pm The push back I get from conventional audio guys is that amp power is very cheap these days, so why sacrifice the space.
Distortion and cost. You can use a very long excursion driver in a small sealed cab throwing 1,000 watts at it and it will go loud, but it will also have high level Doppler and harmonic distortion. Drivers capable of handling 1,000 watts without going past xmax are expensive, as are 1,000 watt amps that really deliver 1,000 watts with low distortion. There's a slight advantage to the sealed rear chamber of the AutoTuba versus the Truck Tuba, but you can't have a sealed rear chamber using an 8 inch driver in a cabinet only five inches deep.

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Seth
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Re: Auto/truck tuba designs

#3 Post by Seth »

Benflitv30 wrote: Mon Jan 04, 2021 3:27 pm ...My intension is to build the most authoritative option I can, in one single cabinet.
Depending on your vehicle and space available... or space you're willing to make available... you could easily create a 4 driver TruckTuba, AtuoTuba, or TallAutoTuba

Do I ‘lose’ any performance by using the dual driver trucktuba design I’ve seen here with the cones exposed?

I've built a double loaded TAT and a Double loaded TruckTuba. Still have them both. I have never done a side by side comparison, and the timeframe between having each installed is about a 10 year span and two different vehicles, so I can't really speak to that one way or the other with any confidence. However, I can say they're both impressive and neither sticks out above the other... again, given my recollection of my system 10 years ago.

Is the only real trade off to folded horns vs direct radiators being the additional size of the cab needed?
The push back I get from conventional audio guys is that amp power is very cheap these days, so why sacrifice the space. If the only drawback is space needed for a folded horn, yet outperforms direct radiators in all other aspects, especially the harmonics and transient response, seems like a no brainer to build the horn.

There's almost always more than one way to create a desired result. I've had higher powered systems with smaller ported boxes that were louder. However, I've never had a ported box sound as good all the way down to 20Hz, and below, as the Truck or AutoTuba has... at any power level. It is possible to achieve. But, to get the lower tuning, the ported boxes get large too.

Ultimately, I like horns just because. They're unique, interesting, very efficient, and sound fantastic... all qualities I appreciate. Something about flexing the roof and windows with an amplifier about the size of my hand puts a smile on my face.

Not to say there's anything bad or wrong with any other design. Maybe there is, maybe there isn't. Build/buy what suits your interests and goals. There's always time to try something different in the future too.
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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Bill Fitzmaurice
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Re: Auto/truck tuba designs

#4 Post by Bill Fitzmaurice »

And as for those conventional audio guys, one thing you can be assured of is that they don't have or have never heard good horn subs. If they had they wouldn't be conventional audio guys any longer.

Benflitv30
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Re: Auto/truck tuba designs

#5 Post by Benflitv30 »

That’s great to know about the slight advantage between the AT and TrT. Thank you for the quick reply as well Bill and Seth.

I know it isn’t popular in this group to have ‘loud’ builds in cars, but it isn’t for competition use, annoying fellow drivers at stop lights, etc.
It’s just like my THT at home, it’s to have that ‘headroom’ for that here and there max blast movie scene, definitely not everyday use.

I do like the idea of just raising the floor some like can be done with the TrT. My max available dimensions are:
40” front to back
40” width
18” tall

If I can do more than two drivers in that available space, I’m all for more output.

I’ll be looking forward to giving the conventional audio guys an audition of this build for sure. I am not a proponent of having to tax my current vehicles electrical system (or upgrade it) like they have to either. I am all about efficiency, superb audio quality, and still have the ability to get loud when the occasional mood strikes.

Bruce Weldy
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Re: Auto/truck tuba designs

#6 Post by Bruce Weldy »

Benflitv30 wrote: Mon Jan 04, 2021 6:09 pm
I’ll be looking forward to giving the conventional audio guys an audition of this build for sure. I am not a proponent of having to tax my current vehicles electrical system (or upgrade it) like they have to either. I am all about efficiency, superb audio quality, and still have the ability to get loud when the occasional mood strikes.
While the other Pro sound guys are bragging about how many watts their system has - I tell 'em how few mine needs and that I can run 16 cabinets between FOH and monitors on a single 15A outlet......and be just as loud as they are. :mrgreen:

6 - T39 3012LF
4 - OT12 2512
1 - T24
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2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Seth
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Re: Auto/truck tuba designs

#7 Post by Seth »

Bruce Weldy wrote: Mon Jan 04, 2021 6:23 pm While the other Pro sound guys are bragging about how many watts their system has - I tell 'em how few mine needs and that I can run 16 cabinets between FOH and monitors on a single 15A outlet......and be just as loud as they are. :mrgreen:
I'm completely onboard with your line of thinking. I'd much rather have the bragging rights of a lower powered system (car or pro audio) and have people wow over that, than hang my ego hat on some astronomical "wattage" number like it means something "cool".

A pair of powered 12" QSC tops and 18" subs has a combined advertised power rating of 11,200 watts. Ridiculousness. But, guys get all wide eyed and giggly about the numbers like it means something. THIS is a SERIOUS system. Uh huh... :roll:
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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Seth
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Re: Auto/truck tuba designs

#8 Post by Seth »

Benflitv30 wrote: Mon Jan 04, 2021 6:09 pm That’s great to know about the slight advantage between the AT and TrT. Thank you for the quick reply as well Bill and Seth.

I know it isn’t popular in this group to have ‘loud’ builds in cars, but it isn’t for competition use, annoying fellow drivers at stop lights, etc.
It’s just like my THT at home, it’s to have that ‘headroom’ for that here and there max blast movie scene, definitely not everyday use.

I do like the idea of just raising the floor some like can be done with the TrT. My max available dimensions are:
40” front to back
40” width
18” tall

If I can do more than two drivers in that available space, I’m all for more output.

I’ll be looking forward to giving the conventional audio guys an audition of this build for sure. I am not a proponent of having to tax my current vehicles electrical system (or upgrade it) like they have to either. I am all about efficiency, superb audio quality, and still have the ability to get loud when the occasional mood strikes.
A TAT would be too tall, but either a TrT or AT could be built with 4 drivers to fit in that space.

Laying flat in a cargo area instead of upright behind a bench seat, a TrT has a 24" x 36" footprint and 18" tall would easily fit 4 drivers if you put them in panel 1 instead of the stock location in the side (top/bottom in this flat configuration).
The AT could be made 40" wide, which would have a footprint of 30" x 32" and a height of 14". Could be a little tight/tricky screwing the center drivers down through the access hole though.

I had planned to build 2 double loaded cabs, for a total of four drivers in my first TAT system years ago. I built one double loaded cab and never built the second. Was satisfied enough with what I got out of the one I built. I wouldn't recommend avoiding a 4x. But, most have built a single loaded and been quite satisfied... And I was/am satisfied with the double's I've built. Still, from time to time, I consider making a 4x just for fun.

I look forward to hearing what you choose to make, your impression of it once it's completed, and seeing a few pics. :thumbsup:
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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Tom Smit
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Re: Auto/truck tuba designs

#9 Post by Tom Smit »

Seth wrote: Mon Jan 04, 2021 9:32 pm
I had planned to build 2 double loaded cabs, for a total of four drivers in my first TAT system years ago. I built one double loaded cab and never built the second. Was satisfied enough with what I got out of the one I built.
This is what I would suggest ....what Seth suggested. Make an AT that is 18" wide, and double load it.The reason I would chose 18" is because it will give a bit of wiggle room when trying to fit the two cabs in together. If it is not loud enough, make a companion for it.
TomS

Benflitv30
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Re: Auto/truck tuba designs

#10 Post by Benflitv30 »

I appreciate everyone’s replies. It’s a tough call.

As much as I like a flat lifted floor I was thinking originally with the TrT, I think the AT wins out for the sake of the slight performance advantage and the drivers being enclosed for protection from any loose cargo etc. I also like the ‘hidden’ look, provides some mystery for the conventional car audio guys.

So for all practicality purposes during the build/mounting of drivers... a dual 8” driver loaded AT is the most ambitious or can dual 10”s be utilized?

Benflitv30
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Re: Auto/truck tuba designs

#11 Post by Benflitv30 »

Bill Fitzmaurice wrote: Mon Jan 04, 2021 3:40 pm
Benflitv30 wrote: Mon Jan 04, 2021 3:27 pm The push back I get from conventional audio guys is that amp power is very cheap these days, so why sacrifice the space.
Distortion and cost. You can use a very long excursion driver in a small sealed cab throwing 1,000 watts at it and it will go loud, but it will also have high level Doppler and harmonic distortion. Drivers capable of handling 1,000 watts without going past xmax are expensive, as are 1,000 watt amps that really deliver 1,000 watts with low distortion. There's a slight advantage to the sealed rear chamber of the AutoTuba versus the Truck Tuba, but you can't have a sealed rear chamber using an 8 inch driver in a cabinet only five inches deep.
Please pardon my ignorance here, but based in another post I saw here when it comes to driver selection, with all other T/S specs being equal, it seems (could be completely wrong of me) that it comes down to the Vd of the driver..the piston area and Xmax. ‘No replacement for displacement’ I’ve heard as well.

For optimized performance, if you could have a custom driver made for an AT, it would need to be within the plan’s specs of course, but from that point you would choose the driver with the highest Vd, correct or ?

I know a place I can get low quantity custom 8” drivers built. This may be a way to get the best cabinet, along with the best driver possible as well. 🙏

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Tom Smit
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Re: Auto/truck tuba designs

#12 Post by Tom Smit »

Benflitv30 wrote: Tue Jan 05, 2021 9:37 pm
So for all practicality purposes during the build/mounting of drivers... a dual 8” driver loaded AT is the most ambitious or can dual 10”s be utilized?
Dual 10's can be used as per the plans.
TomS

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Bill Fitzmaurice
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Re: Auto/truck tuba designs

#13 Post by Bill Fitzmaurice »

Benflitv30 wrote: Tue Jan 05, 2021 9:46 pm Please pardon my ignorance here, but based in another post I saw here when it comes to driver selection, with all other T/S specs being equal, it seems (could be completely wrong of me) that it comes down to the Vd of the driver..the piston area and Xmax. ‘No replacement for displacement’ I’ve heard as well.
That's true of direct radiators, but not horns, which don't necessarily benefit from more cone area. Too much cone area for a given horn throat area gives a reduction in performance. As for xmax, you need enough so that you don't exceed it at the maximum levels you listen at, but there's nothing to be gained by having more than that, especially if in realizing additional xmax the other specs suffer. Anything gained in one spec is always at the expense of other specs.

Benflitv30
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Re: Auto/truck tuba designs

#14 Post by Benflitv30 »

Thank you again everyone.

Yes, Bill, that seems to be true of every sort of engineering endeavor... a ‘science of compromises’, a give and take.

I understand the intention of the cab designs being overall efficiency, as in the required power and driver cost. It seems that if you were to want to optimize the cab as a whole for a ‘premium/high power’ driver, you would basically have to start all over again with the design. Is that correct? I believe it was said that you design a cab for what drivers are on the market, or something to that effect.

Unfortunately, my source I mentioned earlier here for custom 8” drivers does not have an available motor design for that low of Q required of the AutoTuba.

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Re: Auto/truck tuba designs

#15 Post by Bill Fitzmaurice »

If you examine the specs for premium drivers you'll find that usually the main thing that's premium is the price. I don't design for super high power drivers because with horns there's no need for them. 100 watts with a horn can beat 1000 watts with a direct radiator. If you can't find drivers within the acceptable Q range that tells me they're probably auto sound drivers intended for use in small sealed cabs. That makes them unsuited for either horn loaded or ported cabs. All else being equal high Q isn't an indicator of a better driver, low Q is.

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