# Auto Tuba?



## Tom K (Oct 7, 2006)

Any one heard of this? I just heard about it on another forum. Folded horn for the car. 

http://www.billfitzmaurice.com/


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## dewi1219 (Nov 16, 2006)

I am about to build an Auto Tuba for my car. I have already built the Table Tuba for my HT, and it lives up to the hype you read on Bill's forum. The Auto Tuba is fairly big (14x15x32" IIRC), but it's pretty light and gives you big sound with just a few watts and one cheap 8" driver. The Table Tuba gives some of the cleanest most natural sounding bass I've ever heard in my HT room. I can't wait to get the Auto Tuba done to see how it compares. 
Scott S.


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## toolfan91 (Dec 7, 2005)

Whats so different about one of the tuba enclosures opposed to a horn? 

<Noob on advanced subwoofer alignments, but would love to learn more


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## demon2091tb (May 30, 2005)

How is the Home HT with the tempest? I've got a pair i want to do something with eventually and the guy on the site says that it can do110db sensitivity down to 1hz in roomput into a folded horn cornerloaded, Is that even possible? 2 Tempests put into those would be rediculious, like 116db sens with doubling of cone area and power. Rediculious.

Possible? Seems like a bit of EQ would need to be used too.


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## dewi1219 (Nov 16, 2006)

Toolfan,
The Tubas are horns. However, there is a difference between rear loaded horns (sometimes called "scoops") and front loaded horns like the Tubas. 

Demon,
I haven't heard the Tuba HT, but I can't imagine how ridiculous it would be. My "little" Table Tuba (30x30x18) with only a 150-watt amp literally shakes the walls and concrete floor in my basement HT room. I have an IDQ15 just sitting in the garage that I'm very tempted to try in the Tuba HT. But I was about 80% done with my Table Tuba when he released the Tuba HT design, and these are not simple boxes to build. So, I'm waiting to finish a few other projects before I decide on that. 

Supposedly, the Table Tuba is better for music while the Tuba HT is more suited for pure HT use. However, my Table Tuba does perfectly fine down to 20Hz in room for HT. It blends seamlessly with my mains for music also. 

You can see a pic of my Table Tuba on my photobucket page. It is disguised, oddly enough, as an end table 
http://i22.photobucket.com/albums/b319/dewi1219/Subwoofer1.jpg
Total cost was only about $130 - $70 for two 8-inch drivers, $20 for MDF, $30 for a buyout 150-watt plate amp, and a few dollars for paint, brads, glue, etc. Talk about bang for the buck...
Scott S.


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## Whiterabbit (May 26, 2006)

I believe it. Why? Ive got tangband 6's in an excessive sized box well designed and it can compete with a sealed 13w7. No joke. Its not a horn, but the learning is clear: with lots of space to use and design an enclosure, extreeme performance can absolutely be attained from what may seem like entry level performers.

Now we start with a subwoofer thats already well known for its low frequency extension: the tempest. the trick here is to notice his horn design constraints. The horn is 36x36 by a particular width. He claims extension to 1Hz in a 36" wide box. thats a cubic _*yard*_ of box! 27 cubic feet! fold a horn into 27 cubic feet and im sure combied with corner loading we can do some impressive things!

By the way, I think it is interesting to note that dan wiggins released a tempest paper that contained plans (free) to build a horn loaded tempest in a box 36x36 (15-18 inches wide, I believe) for home theater use. Its expected low frequency extension was around 40 Hz, far higher than the same driver in 4 cubes sealed for HT use.

the document is still available by searching out old versions of adire's site, or by finding someone who downloaded the paper.


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## Whiterabbit (May 26, 2006)

aaaaaaaaand though my understanding of horns is rather limited, as I recall the ultimate bottom note is defined by throat area of the horn. so your extension would be directly related to how wide you can make your horn!

which then begs the question: with the extreeme slow rolloff of sealed boxes combined with the russian principle of a horrible inefficient design but throwing so much cone area and power at the situation as to render efficiency moot (ala two tempest), wouldnt the ideal HT construction be precisely to seal your tempest rather than horn load them for maximum low frequency extension?


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## chad (Jun 30, 2005)

I don't trust that cat's designs. He claims stellar performance but embraces Piezo horns in almost every design. As discussed last week a horn CAN work in a car wiht proper placement in the RIGHT car. But it's a lot to wager on considering the complex design and the fact that physics says it simply will not work with the mouth dimensions. Cutoff point IS a product of mouth dimensions that can be changed my adding more horns. Multiple horns lower cutoff to increase mouth area.

Chad


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## dewi1219 (Nov 16, 2006)

Cutoff point is as much or more a function of the horn path length than the mouth area. Mouth area has more affect on the overall efficiency of the horn. More mouth area will push the efficiency lower in the frequency range though. 

Just like any other design, horns have compromises. Size is the biggest compromise over normal designs. I've always heard before - loud, low, small - You can chose two of these three. Which compromise you're willing to make will determine the design that's right for you. But for a project that costs under $100, you don't have much to lose. Many people will want to try it out.

I'm not real keen on his use of piezos either, but keep in mind those designs are for pro audio which is a completely different animal. And still, I've never seen a bad review on his designs. Everyone that has tried them raves about them. I'm definitely a believer in the Tuba subs.


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## chad (Jun 30, 2005)

I work in pro audio and I refuse to use a Piezo as an ashtray let alone a proper HF device 

Path length plays a part ALSO but no, LF extension is a direct relationship with mouth dimensions. Direct radiated boxes gain more in the efficiency area, horns dig deeper but don't gain as much efficinecy. I have some real numbers on my Electrotec LabQ bins I'll try to bring in on array placement. Tonight I'm working on the rack again but I'll try to remember to pack up the array info.

Chad


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## 89grand (Nov 23, 2006)

I want to hear an Auto Tuba for myself.


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## Whiterabbit (May 26, 2006)

if anyone wants to skimp on plans, the table tuba plans were published in a certain recent issue of audio express. a local enormous branch library just might happen to carry a subscription


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