My first Tuba

[BassAwdyO]

I have been inspired lately to build the autotuba by billfitzmaurice. It all started in "The Maximum bang for your buck" thread where many have suggested that the autotuba not only gives an amazing amount of bang for your buck, but also is of high sound quality.

So I went to Billfitzmaurice.com and ordered the plans. It took a while to get them, but for good things we must be patient.

So I ordered the MCM driver and I will start construction on the enclosure tomarrow.

My questions for those of you who have built this in the past(or Bill himself)

1. how well does 3/4" MDF work?
2. Is the only differnce between the 8" autotuba and 10" the width?
3. Will increasing the width of the 8" autotuba give performance beneifits?
4. How exact must the construction be?(I can get down to <1mm tolerences, but not a whole lot better than that with my skills)
5. How much wood will the entire enclosure take to build(how many 4'x8' sheets)

I would post on the forum at billfitzmaurice... but I like this one MUCH better

[zobsky]

Originally posted by BassAwdyO
I have been inspired lately to build the autotuba by billfitzmaurice. It all started in "The Maximum bang for your buck" thread where many have suggested that the autotuba not only gives an amazing amount of bang for your buck, but also is of high sound quality.

So I went to Billfitzmaurice.com and ordered the plans. It took a while to get them, but for good things we must be patient.

So I ordered the MCM driver and I will start construction on the enclosure tomarrow.

My questions for those of you who have built this in the past(or Bill himself)

1. how well does 3/4" MDF work?
2. Is the only differnce between the 8" autotuba and 10" the width?
3. Will increasing the width of the 8" autotuba give performance beneifits?
4. How exact must the construction be?(I can get down to <1mm tolerences, but not a whole lot better than that with my skills)
5. How much wood will the entire enclosure take to build(how many 4'x8' sheets)

I would post on the forum at billfitzmaurice... but I like this one MUCH better

as the plan suggests, use 1/2" material, else all the other proportions will be inaccurate

a 4 x 8 of 1/2" plywood will suffice (and is only slightly more expensive than 3/4" MDF)

1mm tolerance is sufficient

in my opinion, the one thing that i would suggest would be to make 2 of the sides 4 - 6 " longer so you dont have to deal with making feet for upright placement later on

[simon5]

Hey, nice, I hope you can do some measurements after everything is done!

Especially since you have some subwoofers to compare it to.

[BassAwdyO]

I do plan to use this for Auto purposes.... so I wont be needing the legs as it will surely be placed sideways...

I think I can make adjustments to accomodate 3/4 inch wood. I already have a few sheets of MDF and thats what I normally used to build with.

I will do some home comparisons though.. and hopefully some measurements for simon5

[chipco3434]

If you build with 3/4 material, make absolutely sure that the added dimension is added to the OUTSIDE of the scroll as you go. In other words, there will be real problems with the sound quality if you make the speaker chamber any smaller... the speaker will not fit! It needs all the clearance it can get.

Mount the speaker on the baffle before you start assembly.

[Retsel]

I have one more suggestion. If you do build the cabinet from 3/4 inch material, don't make the assumption that you can leave out the center brace. It is critical. If I were to build this basshorn, and I purchased the plans so maybe one day I will, I also would build it out of 3/4 inch stock for the improved stiffness.

I can't answer the question about MDF or plywood. MDF is more accoustically dead and is less likely to have resonances in the midrange frequencies, but I have heard no complaints about this when reading posts about the quality of this bass horn. MDF is less stiff, but building the box out of 3/4 inch material with the center brace should compensate.

Retsel

[chipco3434]

I built mine out of MDF. They're fine. Dead as a rock. And YES, the bracing is important.

Best suggestion... layout one side and use a 1/32" drill to mark the intersections when both sides are clamped together. This will assure that the sides are mirror images.

[BassAwdyO]

Thanks for all the advice guys...

I plan to increase the dimensions by 1.25"- H .75"-D and .5"-W to make the 3/4" material work. I will brace exactly as the plans have specified except maybe at the mouth I was thinking of making the brace come out a bit farther so it ends up ~6 inches.

I'll be starting on the enclosure in a few minutes, but it will be a while until I get the driver. I havent even recieved an invoice from MCM so it could be a while...

I was thinking of putting an extremis in there and trying it out though

[BassAwdyO]

Well.... after about a half a day's work the enclosure is basically finished. Once my digital cam battery charges I'll post some pictures, and after that I'll hook it up for a listen!

I'm using one of my extremis6 midwoofers in it right now, so I dont know how good of an assesment it will be considering that it was not designed for this speaker, but a horn is a horn and the speaker in question shouldnt have too dramatic of an effect on it's function... right?

[BassAwdyO]

Here's a side view with one side removed....

I know the woodworking isnt perfect, but what can I say. That angled peice that forms the mouth is the most horrid. My table saw only goes to 45degrees though so thats the best I could do with it. Oh well.... I'm filling all the gaps with hot glue(for now) to seal it up and hear how it sounds. Once I get the MCM I'll take it apart and liquid nails everything and finish it off.