Auto Tuba Review

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ACUA
Posts: 552
Joined: Sun Sep 25, 2016 6:21 pm
Location: Tucson Arizona

Auto Tuba Review

#1 Post by ACUA »

I have just finished up an AutoTuba with the 8" MCM driver at 14" wide. This sub cab is in my 2002 gmc pickup truck extended cab. This subwoofer is replacing a light duty 10" direct radiator bass reflex 1.25cuft 34hz tuned enclosure consuming around 400watts. I am powering the AT off of an old school USacoustics 2075 amp, bridged is not much over 100-150watts ish. Basically based on everything I have learned here it is a no brainer, but I will elaborate anyway. Basically this AutoTuba destroys the old setup in everyway, it is more efficient using 1/4 the power, it pretty much plays out flat to 20hz where the other setup fell out after 24hz and became labored below 30hz, the old sub had a peak around 32-36hz for obvious reasons that took away its audiophile potential. with the new cab it is pretty flat across the board and the blend to the mid range drivers was easy to sort out, let it be said that I have some DSP in my head unit making integration pretty easy.

I made the old sub sound good and never drew enough power to stress the electricals, but I could have ran like a 10gauge wire for the amp I am using now!!! the old sub setup seemed to have nothing really lacking but this new sub is truly better. The sounds are correct, smooth, tight, sharp (when supposed to be), theres less shakes in the cabin but more pressure is perceived. perfect perfect perfect, the box is a little bigger than the old one but not by enough to make the switch any less desirable.

look I am posting this up to directly compare a typical car setup to the AutoTuba. The AutoTuba is better by a lot if you can correctly fit it. I will not only recommend it but try to convince everyone I know who is in the market to let me help them build one.

I have built a few Tuba45s 24" and a T18 12"wide loaded with TB6.5" and just started some onmitop12s. I have the above listed AT as well so far not one of these designs has not been worth the effort/investment. I am a DIY guy and I live to build and work with audio equipment. The Bill Fitmaurice loudspeaker designs are valuable to me!!!
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10" driver in 1.25cuft bass reflex 34hz tune on about 400w power
10" driver in 1.25cuft bass reflex 34hz tune on about 400w power
8" in 14" AT on a 100w power amp
8" in 14" AT on a 100w power amp
Advanced Concepts Underground Audio

ACUA
Posts: 552
Joined: Sun Sep 25, 2016 6:21 pm
Location: Tucson Arizona

Re: Auto Tuba Review

#2 Post by ACUA »

flip the pic over
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Advanced Concepts Underground Audio

ACUA
Posts: 552
Joined: Sun Sep 25, 2016 6:21 pm
Location: Tucson Arizona

Re: Auto Tuba Review

#3 Post by ACUA »

bloody hell flip over!!!
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IMG_0519.JPG
Advanced Concepts Underground Audio

ACUA
Posts: 552
Joined: Sun Sep 25, 2016 6:21 pm
Location: Tucson Arizona

Re: Auto Tuba Review

#4 Post by ACUA »

well I cant get the picture to invert, sorry about that, basically I removed my center consul a while back for fun, then got the idea to build an AT and put it as my center consul, so I put my sub in a similar shaped box and placed it in the truck where abouts I would be putting an autotuba, after deciding that the spl was about the same in that spot as having the sub under the back seat I decided that an autotuba I would build. for under $200 and a lot of fun I have my sub in my truck and its better than I could have hoped for. once again sorry that the picture is upside down stupid thing cant get it to flip right ways up. well anyhow...
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J_Dunavin
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Location: Appleton WI
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Re: Auto Tuba Review

#5 Post by J_Dunavin »

NICE! I also have an MCM autotuba in the back of my Buick Park Ave. They Rock! Glad your happy with it, and i love the center console idea!
2 - OTop8
2 - T39
8 - DR200
2 - DR250
9 - T24
6 - T45
1 - Auto Tuba

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Tom Smit
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Re: Auto Tuba Review

#6 Post by Tom Smit »

Aren't they greats?!! Glad you like it!
TomS

ACUA
Posts: 552
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Location: Tucson Arizona

Re: Auto Tuba Review

#7 Post by ACUA »

Been a few days now with the AT in my truck. I metered a 20v 60hz tone at 115db spl on my RadioShack unit. I intentionally pushed 24v 31hz out of the thing to see what would happen and I heard distortion but did not hatch the driver so that is good. This AT is not as loud in this configuration as the direct radiator 10” between 40-60hz but it is better below 40hz and the kick drum snap is tighter than it ever was with the bass reflex. Sound quality is way better with the AT.

67watts is nothing, and doing 115db spl. That keeps up pretty good with the rest of my truck system so I can’t complain.
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djamps
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Re: Auto Tuba Review

#8 Post by djamps »

So how do you guys affectively limit these things in autos? I've not seen any auto amps that have any sort of voltage limiting, and only a small handfull with HPF/subsonic filtering. My MCM T18's complain over 20v. I imagine it would be alot more difficult to notice the sub complaining in a noisy car, especially tucked away in a trunk.

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Seth
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Re: Auto Tuba Review

#9 Post by Seth »

I just turn it down if I hear voice coil slap. :)
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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J_Dunavin
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Re: Auto Tuba Review

#10 Post by J_Dunavin »

Its not 100% fool proof, but you run a test tone at 0 db, say 50hz at max non clipping. ( A test tone somewhere in your crossover range, like 10 hz is too low, 100hz probably too high)
You should use a o scope for that part. Then measure the amp until you get to whatever voltage you aiming for.
Now you should be able to turn up your system to that max clean number and not go over your measured voltage.
Again it's not a limiter, but at least it gives you a reference point.

Oh and a high pass is necessary of course.
Most in line, active crossovers would have that.
See audio control 2xs for example.
Inexpensive and easy to add next to the amp.
Last edited by J_Dunavin on Sat Jul 14, 2018 1:12 pm, edited 1 time in total.
2 - OTop8
2 - T39
8 - DR200
2 - DR250
9 - T24
6 - T45
1 - Auto Tuba

jimbo7
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Joined: Fri Dec 28, 2012 10:45 am
Location: St. Louis

Re: Auto Tuba Review

#11 Post by jimbo7 »

djamps wrote: Fri Jul 13, 2018 6:03 pm So how do you guys affectively limit these things in autos?
My headunit can turn on/off the internal amp for the door speakers, so I turn them off then play a 20hz tone with the volume cranked all the way (just the sub playing). Then I measure the voltage output from the sub amp and set it and forget it. Quick and dirty, but I know it'll never push the speaker too hard at max. Still ungodly loud at above normal listening levels. Edit: Remove sub wires from amp before doing this!
BFM builds:
XF212
T24 BP102 24"
2x SLA's 6-5" mids, 9- gt-302's
2x AT 14" MCM 55-2421
TrT 5" MCM 55-2421
AT 18" JBL GTO804
2x OT12 flat array
2x SLA Pro 2-Alpha 6's 2-Goldwoods
2x T39 24" 3012lf
Simplex 10 BP102

ACUA
Posts: 552
Joined: Sun Sep 25, 2016 6:21 pm
Location: Tucson Arizona

Re: Auto Tuba Review

#12 Post by ACUA »

I guess in my automobiles!!! Basically over time I can sort out how loud the system is at what voltage level audibly. Problem is that finding where the amp does 20v on sine wave does not clearly indicate where music is hitting 20v. So I just guess and meter here and there to see what is happening!!! Never have had problems yet but this is my first AT
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djamps
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Re: Auto Tuba Review

#13 Post by djamps »

To answer my own question I suppose minidsp but - 1. limiting is not a brick wall (but better than no limit) and 2. cost as much or more than the small amp required for an AT :/

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Seth
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Re: Auto Tuba Review

#14 Post by Seth »

And to follow up on my statement...
SethRocksYou wrote: Fri Jul 13, 2018 6:28 pm I just turn it down if I hear voice coil slap. :)
I originally intended to build 2, double loaded, 20" wide TAT's and ordered 6 MCM drivers. 2 as spares/backups. I built the first cab and never built the other. Partially because it was a lot of work and partially because I was very satisfied with the one. And... it's big.

Anyway, it's been about ten years since the build and the TAT is now the garage stereo sub. In those ten years and multiple duties I've slapped the voice coils many many times. Yet, I still have 4 spare drivers.

Not to say that this is any sort of recommendation. Just food for thought. Another experiential report to ponder.
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

jimbo7
Posts: 849
Joined: Fri Dec 28, 2012 10:45 am
Location: St. Louis

Re: Auto Tuba Review

#15 Post by jimbo7 »

SethRocksYou wrote: Sun Jul 15, 2018 3:40 pm Anyway, it's been about ten years since the build and the TAT is now the garage stereo sub. In those ten years and multiple duties I've slapped the voice coils many many times. Yet, I still have 4 spare drivers.
How has your MCM lasted that long!? The 2 I bought that liked to separate their voice coil from the spider. One was brick-wall limited and the other with car amp gain adjusted. Got tired of gluing them back on and got the JBL GTO.
BFM builds:
XF212
T24 BP102 24"
2x SLA's 6-5" mids, 9- gt-302's
2x AT 14" MCM 55-2421
TrT 5" MCM 55-2421
AT 18" JBL GTO804
2x OT12 flat array
2x SLA Pro 2-Alpha 6's 2-Goldwoods
2x T39 24" 3012lf
Simplex 10 BP102

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