Cabinet project, 3 cubic feet, various speaker options

Thomas Zemp · From: Davos-Dorf, Switzerland

Hello everybody who likes to give me some advice (or his personal opinion) to the following project:

I ran into some nice scrap wood that was just perfect to put a good size cabinet-body together. It has a inside volume of 84.8 l = 3.0 cubic feet, inside dimensions are 625 x 630 x 256 mm or 24.61 x 20.87 x 100.79 inches.
I am going to put a soundboard onto it with one of the following speaker options:
- Altec 418B, 15"
- Altec 418-8H II, 15"
- Altec 417-8H, 12"
- JBL K130, 15"
- JBL K120, 12"
- Weber California ceramic, 12"
- BlackWidow 1201, 12"

The cabinet is closed back, and I don't know to what frequency I should tune the vented box. Actually I am not into the formulas to determine the proper dimensions of a port for these speakers an dimensions.
So if somebody could suggest a "universal" tuning, port dimension or something, that would be of great help.
I am in the mood of trying different speakers, time after time, but I don't see to find the time to do every sort of testing or calculating.
Your advice or personal expertise would just be what I need and what I would like to rely on.

Currently I am playing a WBS SD-10 on an advanced beginner level (whatever that is) through a Randall RG-300 head, which suits me very well.
I am living in Switzerland, and my mother language is Swiss German. But I like English when it comes to steel guitars ...

Thanks, regards
Thomas

Bill A. Moore · From: Silver City, New Mexico, USA

Years ago I built the EV TL606 cab for my wife's bass, but it has been used for guitars more than once. It's volume is 3 cu ft.

Donny Hinson · From: Glen Burnie, Md. U.S.A.

I'd go with one of the 15" Altecs and use a sealed back with an un-tuned front port of 3" or 4", as I was never partial to the other brands you mentioned.

Thomas Zemp · From: Davos-Dorf, Switzerland

Thank you for the idea of a simple port in the baffle board, which I remember seeing on various (instrumental) cabinets.
Is the physical idea the same as with the soundhole of an acoustic guitar? Would the larger diameter (4") support slightly higher frequencies while a smaller one (3") gives more bass? Would a tuned port (tube) give a narrower frequency boost?
Just trying to sort out my physical thoughts. It looks as can't go completely wrong.

Steven Paris · From: Los Angeles

This is a freeware program for designing speaker cabinets, and has many speaker's Thiele-Small parameters already in its database:
http://www.linearteam.dk/?pageid=winisdpro
It's quite an interesting little program. Try it!

Stephen Cowell · From: Round Rock, Texas, USA

3 cubic feet is too small for an infinite baffle cabinet (no port)... and any port you install will have a big effect on a closed-back system. If you really want to experiment with all those drivers I'd just go for an open-back system... steel players seem to prefer these anyway, for the wider dispersion and more open sound.

However, Small-Theile speaker cabinets sound awesome for their size... they really put out the bass frequencies well. The port is designed to take the normal bass 'hump' and split it to widen it out and flatten it... makes an amazing difference. However, you *have* to follow the rules for cab size, port size, port length, etc... you can't just fudge it like you can with open-back cabs.
_________________
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Donny Hinson · From: Glen Burnie, Md. U.S.A.

The following is offered in the spirit of friendship and information:

It's a good thing to keep in mind that much of what one might glean from the internet about speakers and enclosures isn't really pertinent to those used for musical instruments. If musicians, generally, were really interested in maximum flat frequency response and maximum efficiency, they would not be using enclosures with a single transducer, or those designed where small size and portability are main considerations.

Now, I can't speak for others, but my recommendations in this area are not the result of "fudging". They're based on experience with actual Altec-Lansing blueprints for instrument speaker enclosures, several of which I have built myself.

Smile

Thomas Zemp · From: Davos-Dorf, Switzerland

Meanwhile I have completed my little project, choosing the Altec 418-8H-II, 15â€, cutting a round port with 4â€ diameter with no further tuning â€¦. and being rather happy with the results.

Donny Hinson seems to be right â€“ and I thank you â€“ with the thought, that for musical instrument application, a flat frequency response is not what we are basicly after. Second, itâ€™s a lot about the dynamic behaviour of a speaker that makes it nice for steel, guitar or bass.
The 3 cubic feet, ported cabinet works much to my taste for acoustic bass as well as for steel. Strong but not overemphasized bass - exactly how I like it.
I have already experimented with open back and open baffle arrangements, they also sound very nice and interesting, even for acoustic bass.
I am just reinventing (with your help) the basic designs the designs of the 70ies for my own use. As I am a child of the 60ies, that sound is right for me.

Jim Palenscar · From: Oceanside, Calif, USA

When I've used the traditional JBL recs for speaker enclosures they almost always been larger than I wanted so ultimately made smaller ones. You stated that the inside dimensions were "24.61 x 20.87 x 100.79 inches" ~ holy toledo- that's one big spicy meatball!!

Thomas Zemp · From: Davos-Dorf, Switzerland

Never built such a huge cabinet before, true! But the dimensions indicated above are surely wrong.
Correct are 84.8 l = 3.0 cubic feet, inside 625 x 530 x 256 mm or 24.61 x 20.87 x 10.79 inches, without remeasuring it. Sorry and Thanks.
Thomas

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