2xAutoTuba results from USAC / DB Drag Race

[Radian]

Although I don't make a habit of attending sound-offs, I found out there was an event going on nearby and decided to see what 2 of my fleet of 4 AT's could do.
I entered in the Street Stock Class A (less than three 8's) DB Drag Race. I was more interested in what the AT's in my GF's car were capable of WOT. We all know the AT's sound absolutely phenomenal day in and day out. I used the Bink's CD at 60 Hz, cranked the amp up to 10.6V. I wanted 14V, but couldn't get anything higher out of amp, and that was fine with me. I was almost deaf just from dialing in the amp, and the trunk wasn't even closed yet. I drove over to the test lane, the judge came out to place the mic, and got the thumbs up to let 'er rip.
127.0 db
It didn't draw too much attention from the rather small crowd (Some cars were pushing 150db with the accompanying mega distortion) until the judge announced that the tone was emanating from just two 8's. Then the crowd gathered 'round and the questions came. No one could figure out how the boxes were built, and only one kid even knew what a horn loaded sub was. That guy, the SQ judge, and the DB Drag Race official were the only ones truly impressed with the output. I received a few words of praise for the construction quality and install (VERY clean and tidy compared to every one elses). Honestly, I built this system very stock and the car is very anti-climactic. Not a hint of bling here for security reasons. The side effect of low-key is almost complete indifference from folks walking by.

There ya go....did I mention 10.6V? Gotta love this design.

[thijs666]

10.6V @ 4 Ohms ~ 28W

So... you're saying you got 127 dB from 28W ...

(note: I'm not sure, but I assumed one AT is 8 Ohms; what driver did you use?)

This makes me interested in the findings of a friend of mine who said he was going to join a dB drag for once at a meeting last weekend (he normally doesn't care) . Think I'm gonna give him a call .

[Radian]

That's what I'm saying. I didn't have the heart to tell anyone there that I was consuming less than 50W. The judge knew because that's what I wrote down on the registration paperwork underneath "amplifier power".

I used the MCM 55-2421 per the plans, the boxes were built exactly as Bill prescribed.

[Rickisan]

If word gets around in these "DB Drag" circles Bill will be sellin' quite a few plans.

[thijs666]

If word gets around in these "DB Drag" circles Bill will be sellin' quite a few plans.

Naaa... I don't think so. It's all about "I've got 20.000 watts and 5 extra alternators attached to 3 batteries and 6 capacitors" ...

We know better .


.... well ok, I'll have to admit that I don't see enough AT's fitting in a car to get to 153 decibels, but I'm not interested in that kind of loudness anyway, as I already have a small leak in my wind screen and it sounds like my license plate is going to come off with only one AT. That's loud enough for me .

[Bill Fitzmaurice]

If word gets around in these "DB Drag" circles Bill will be sellin' quite a few plans.

Naaa... I don't think so. It's all about "I've got 20.000 watts and 5 extra alternators attached to 3 batteries and 6 capacitors" ...

+1. dB competitions are about as useful as rubber crutches. But it does keep the participants busy doing something harmless, as opposed equally useful pursuits that include, but aren't limited to, blowing up frogs with cherry bombs, toppling gravestones and mugging little old ladies.

[John H]

> Naaa... I don't think so. It's all about "I've got 20.000 watts and 5 extra alternators attached to 3 batteries and 6 capacitors" ...

maybe I should compete then. I've got 134,000 watts (a.k.a the motor) and one Autotuba. Then again I don't get the whole point of that stuff either.....

JH

[chrapladm]

I cant remember but is 2x8's louder than 1x10?

Or do the eights run out of room before the 10 does?

This is all regarding max spl.

[dbaldock]

If word gets around in these "DB Drag" circles Bill will be sellin' quite a few plans.

Naaa... I don't think so. It's all about "I've got 20.000 watts and 5 extra alternators attached to 3 batteries and 6 capacitors" ...

+1. dB competitions are about as useful as rubber crutches. But it does keep the participants busy doing something harmless, as opposed equally useful pursuits that include, but aren't limited to, blowing up frogs with cherry bombs, toppling gravestones and mugging little old ladies.

Or, street racing.

[myn]

That's a very respectable number given the power (28 watts).

When I was in the car audio circuit the competitions were segregated into different classes based on amp power @4ohms/12 volts.

Of course when the car audio amp companies saw this they took advantage of it producing amplifiers that could handle extremely low impedance loads that were utilizing class D power. So a 40watt x 2 at 4ohms/12volts would become 1200 watts @ .5 ohm @ 13.4 volts. This started the cheater class of amplification..

Than came the high tuned ported enclosures that were designed to deliver high SPL at a very high frequency and usually only capable of a very narrow band above 55hz. These subs are far from musical to say the least but can knock the wind out of you at close range.

The fact that 2 AutoTuba's are capable of sounding so musical and are only getting 28 watts of power delivering near 130dbs is something to be pretty proud of.

With that said, there was a guy by the name of "John Notle" who was a frequent visitor to many car audio forums that had this amazing enclosure featuring 2 6.5"'s powered by a 200 watt amp. He made countless videos of him having people guess what was in his car. No one could believe he had 2 6.5s and 200 watts. From the looks of the enclosure, it appears to be that of either a folded or tapped horn. The drivers are 6.5" Audiobahn AMD60Q's

He later started powered4sound selling subwoofer enclosures, none of which were folded horns.

In any case, here are a couple of his videos. I've always been intrigued by small efficient subs that develiver high SPL such as BFM's designs. I'd love to hear Bill's take on this particular design:

http://profile.myspace.com/index.cfm?fu ... id=2013164
http://www.realmofexcursion.com/videos/ ... 6.5.1b.wmv


Congrats on the nice score

[Bill Fitzmaurice]

I'd love to hear Bill's take on this particular design:

http://profile.myspace.com/index.cfm?fu ... id=2013164
http://www.realmofexcursion.com/videos/ ... 6.5.1b.wmv


Congrats on the nice score

You can't see them well enough to tell what they are, though they appear to be tapped horns.

[Scott Brochu]

My AT moves my VW convertible's top something wicked. Didn't know that was such a big deal in the car audio world.
My wife hates it when the car is closed and the top expands.

[chrapladm]

I think that is pretty cool hat they made an incredible sound with 6.5's.

As far as how loud they are you usually can tell how loud something is by standing 35 feet away from the car and then using the camera mic. Now it will only distort the camera if it is EXTREMELY Loud. I have heard 20,000watts going to 4x18's and 100ft away it was still ridiculously loud. I felt like I was at a concert. But I also remember being at a concert and hearing a bassist play through a horn loaded bass cab that had 16 five inch drivers and that was even louder and amazing sounding musically at about 150 ft. The PJB bass cab that he was playing through is also $2500 and 286lbs.

In the video he said it sounded better with the windows up. That would make sense since the woofers are only 6.5" . If they were 10 or 12's I think they would sound better if the windows were rolled down. Just my thoughts, I dont know the physics of it but I am sure Sydney could tell us or Bill of corse.

As far as I can tell that is a huge box for 2x6.5's. Maybe the horn length is 18ft. I also have had in the past 1x8" JL audio W7 in the same size box as the 6.5's and that was amazing sounding(musically) and pretty dam loud. A few of my friends have had the 10" version and that 10 is insanely loud with 500 watts to it.

I think I will stick with TAT and just get the 10" for it. Then I will never want anymore bass for my car and wont have to worry about abusing it either from the occasional driving alone and needing to FEEL the bass. Just like building the THT for my home theater.

Anyways 2 AT and 28 watts is amazing and the best thing in my opinion is a amp that puts out 50 watts will be VERY cheap.

[Bill Fitzmaurice]

In the video he said it sounded better with the windows up. That would make sense since the woofers are only 6.5" . If they were 10 or 12's I think they would sound better if the windows were rolled down. Just my thoughts, I dont know the physics of it but I am sure Sydney could tell us or Bill of corse.

Cabin gain. Without it those stupidly high measured SPL levels don't exist, and as soon as you roll the windows down it's gone.
The only thing about that video that should come as a surprise is how little the so-called 'professional' in the passenger seat knows about the physics of sound. True, he's probably working from a script, but what's unfortunate is that the vast majority of auto-sound pros have a knowledge base that only extends to the advertising copy of the products they sell, so the script is founded in reality. But to be fair the same applies to the guys who man the sales floor at G-C and the like, let alone Best Buy.

[myn]

In the video he said it sounded better with the windows up. That would make sense since the woofers are only 6.5" . If they were 10 or 12's I think they would sound better if the windows were rolled down. Just my thoughts, I dont know the physics of it but I am sure Sydney could tell us or Bill of corse.

Cabin gain. Without it those stupidly high measured SPL levels don't exist, and as soon as you roll the windows down it's gone.
The only thing about that video that should come as a surprise is how little the so-called 'professional' in the passenger seat knows about the physics of sound. True, he's probably working from a script, but what's unfortunate is that the vast majority of auto-sound pros have a knowledge base that only extends to the advertising copy of the products they sell, so the script is founded in reality. But to be fair the same applies to the guys who man the sales floor at G-C and the like, let alone Best Buy.

Yup. Infact shortly after, Gately started manufacturing and selling Nolte's "SnailShell" designs in clear plexiglass. They were deamed as being more efficient than a vented alignment. To me they just appear to resemble a Transmission Line: