BillFitzmaurice.info

I am building a custom iPod dock and I want it to be somewhat small but have some efficient loud bass that draws lower wattage. I was thinking since the Bill Fitzmaurice tuba subwoofers are so efficient maybe this could be done with a small driver in a cabinet about 12"x12"x12" approx. I have a 5.25" driver that was in a small vented cabinet that was making decent bass 35-150hz so I want to use it in the tuba. I have included the measurements of this driver below but I have no idea how to efficiently tune or design a tuba. Bill, if you read this maybe you could come up with a Tuba design for a 6" or 5.25" driver and I will be the first one to gladly buy the plans for $14.95. Then you will have a complete woofer selection of Tubas on your website from 5.25" all the way to 15"!

If not any advice for me?

Here is a zoom of the specs, a little easier to read...

The T18 has the smallest dimensions possible for a horn loaded sub. Anything smaller will work better direct radiating.

The Tuba 18 can be built as small as 13'' W, 18''D and 19'' H. Maybe that could still work for you. The only way to be sure is to build a mockup with cardborad and duct tape to get a ''hands on'' feel of the size of the box. Worst case, that will be severe overkill for an Ipod dock !

By the way, what will you use this for ? Portable or mostly installed in your living room ?

@Bill, thanks for the response. I know now not to try a smaller cube. I am thinking if the 18x19x13 T18 could work with a 6" driver I have, might be worth a try...

@mr.lussier, it is going to be large but still portable. I have been challenged by a group at my work to make the loudest iPod dock in the smallest footprint. There are 3 people in this challenge and the docks will be rated and judged by others at my work! So this is just a fun project with a bit of competition tied to it and the idea is a very loud dock that is severe overkill! As for the use, in the end I will hope to use it in my living room and still be able to bring it to the cottage if I want and play it on battery power outside.

The rules for this challenge was no bigger than a 6" driver for sub, must be portable, battery and AC operated. So far I have a 100w mono amp for the sub and a 40wx40w plate amp for the left and right that are old parts from projects that I worked on long ago. I have a power inverter with 30 x 2200 MAH NIMH AA rechargable batteries all running at 12v. I tested the 30 batteries running my ipod dock plugged into it which is a good one with deep bass that is 20w (so it claims) and it ran at full volume for 14 hours so I will assume that my 180w of peak power will run for at least 2 hrs and at normal volume probably 7 hours. I want to use what I have to make something cool and that will walk all over the competition. I have a dock connector already also, got it from ebay for $3. I have to think if the T18 as large as it is will do the job that much better leaving me with better battery life and more output or leave my 5.25 in the small vented cabinet that already does 35 hz and is very room filling. I am nearly willing to make a test box just to see... I am currently trying to redesign the dock so it can be such a large box!

The t/s specs don't lend to horn subs.

Gregory East wrote:The t/s specs don't lend to horn subs.

Nor a subwoofer for that matter.

Better in the box he already has than a t18?

Check out the Anarchy tapped horn - http://www.diysoundgroup.com/flat-packs ... hy-th.html

fitzwaddle wrote:Check out the Anarchy tapped horn - http://www.diysoundgroup.com/flat-packs ... hy-th.html

When you do pay attention to the SPL chart. Yes, it goes low. But it doesn't have any better sensitivity than a direct radiator loaded in the same size cab, if not smaller. It won't compete with a 1x12 direct radiator for output. IMO the return on the cab size and complexity doesn't make it worthwhile. And that's why I don't use smaller than an eight for a sub.

Yes, I am trying to achieve SPL at least at 100db from about 40hz though to 150hz to make it worth my while to build another cabinet for this project. Something like the Anarchy tapped horn that is around 88db from 20hz through to 100hz is very similar to what I have built in the vented cabinet already accept I don't hear 20hz, I have a decent sounding response from 35hz and up. I am still thinking. Might try some testing with 9 feet of horn in a spiral configuration like this. The picture is just to show the idea of the layout. The spiral will be much tighter and go around a few more times. This is easy to build a test mock up so it might be worth the testing to understand whats happening. I could easily start at 9 feet of horn and work my way down until I have an idea of whats happening to the sound.

A 6" can certainly hit 20Hz, but don't expect significant output. Because of the lack of surface area, it will have to have monster excursion to move enough air. The Tang Band 6" has quite a bit, and can do 40Hz, but is still quite volume limited.

Also, how do you plan to build a spiral like that? I would imagine you'd have to go with fiberglass.

use 1/8 ply probably all you would need, double them up, your only using such a small driver so you probably wouldn't need more than 1/4''. bracing would still be needed. with the rounded edges all the driver distortion will be transmitted to the mouth, so it wouldn't sound clean like a horn.

I always thought of designing my own computer sub, but I wouldnt need sensitivity, just clarity and extension. so maybe a 20 hz horn design at 80db would suit me!

TheGreatGazzoooo wrote: Might try some testing with 9 feet of horn in a spiral configuration like this.

A spiral horn offers no benefits with a sub, while making the build very complex.

After laying out the spiral configuration, the smallest I could make it was about 14x14x14. Still this is way to big for my dock especially considering this is a 5.25 inch woofer in there. I will not bother with even testing horn configurations at this small size. Bill is 110% correct with the T18 being the smallest possible tuba. Vented cabinet it will be! I will post picks at least so you can all see the finished product! The design is planned to be about 16x9x6 and have a detachable sub cabinet that can be corner loaded just like a computer 2.1 speaker system or remain attached as one complete iPod dock. I have a 100w sub amp and 40wx40w plate amp for the left and right so should be pretty loud if I can get some efficient speaker designs. The sub already does very well in a vented cabinet that is 0.21 cubic feet tuned to 38Hz. The result is the lowest sound noticeable is around 35Hz anything below that really drops off the scale which is fine for a small dock. I wont be pushing all 100w of the sub amp into that tiny 5.25, I will adjust the gain to where I think it is happiest and that is where the sub volume will stay.