DIY 3-way speaker with 12' in a cabin, midrange & tweeter in another cabin???

[hariskar]

Can I find instructions to make a DIY 3-way speaker set that has: a 12' (sub)woofer in it's own cabin and a midrange and tweeter in another smaller cabin?
Is it a good idea? What are possible disadvantages?
Thanks!

[kexodusc]

Can I find instructions to make a DIY 3-way speaker set that has: a 12' (sub)woofer in it's own cabin and a midrange and tweeter in another smaller cabin?
Is it a good idea? What are possible disadvantages?
Thanks!

Disadvantages - 15" deep cabinet in a 40" tall speaker for starters. Do you want these things to weigh 100 lbs each? :D

If you're serious about doing this, I'd suggest using dual 10 " woofers over 12" woofers. Port the lower half of the cabinet. This should give you the added response. Unless you don't mind 15" deep cabinets, then by all means use a 12" woofer. You might have problems finding a woofer that works well in such a small volume though unless it's a sealed cabinet, and then you lose some bottom end.

You probably won't find a proven and tested design with built in subwoofer(s), but you can get away with using a good proven 2-way bookshelf speaker, and basically building that on top of another cabinet for the subwoofer. The tonality would change probably very slightly as the baffle step is now different, but I would think only to the tune of a 1 dB or so across between 500 Hz and 200 Hz...might not even be noticeable depending on the model.

I have a few ideas on the go right now to do this same thing with the popular EFE Audioreview.com DIY speakers for my parents. The addition of a large screen tv on their narrow wall has made their subwoofer almost impossible to place in the room...so I'm thinking of building the subs into the cabinets.

[Swerd]

Here are plans for a DIY 3-way with a 10" woofer, where the woofer is in a separate cabinet from the mid and tweeter. http://murphyblaster.com/content.php?f=MBOW1_3-WAY.html.
I've heard this one and it is excellent. The designer, Dennis Murphy, has a good reputation for designs that work as promised.

The woofer cabinet is sealed and is 2 cubic feet. Good smaller cabinets for the mid and tweeter can be bought from Parts Express, 0.375 cubic feet model http://www.partsexpress.com/webpage.cfm?&DID=7&WebPage_ID=180&raid=44&rak=finished_cabinets. Or you can make your own cabinets from Dennis Murphy's plans.

Also read the plans for the MBOW1 (the 2-way cousin of the 3-way), and the MB20 and MB27 which are lower priced alternatives that use $30 tweeters instead of the Hiquophon OW1 tweeter at $90 each.

[kexodusc]

Good call on the MBOW1's... I forgot all about those.

I wonder if it would be adviseable to build the side and rear panels of the speakers at least the full height of the speaker rather than sticking a PE cabinet on a longer bottom cabinet? If he can do the bottom parts for the sub he can do the top as well and save a bunch of money too? But I'm just thinking from a structurally sond point of view -then again it might not matter in the end.
.

[Swerd]

Now that I thought about it some, I would not recommend the pre-made Part Express cabinets for a 3-way MBOW1. The problem is the size of the crossovers for the midrange and tweeter will be too large to easily fit inside the cabinet.

I recently built the MB20 and used the cabinets from PE. They are very well built, and the gloss black finish looks great. There is an internal brace that runs from top-to-bottom and side-to-side, that divides the floor of the cabinet. The brace has 2 large holes in it allowing air flow and access to the rear of the cabinet.

http://www.partsexpress.com/imageslarge/302-710i.jpg

The part of the floor behind the brace is larger than the space in front, so it made sense to put the woofer filter on a separate board in the rear and the tweeter filter in the front. I measured the floor spaces behind and in front of the brace, and cut some hardboard pieces to fit. Of course the inductors stood taller than I had thought, and I didn't install the boards until after I had sealed the port vent in place. That blocked the upper hole in the brace. As a result, getting the woofer board in the rear space was a very tight fit. I had to trim off all the corners and then some just to get it in.

In the 3-way design, the midrange speaker has even more components on the crossover board than the midwoofer does for the 2-way. So I don't think it will fit in the PE cabinet at all. The cabinet as Dennis Murphy shows it has no internal brace. It would be better to follow that design.