3-Way Cabinet Question

Thank you for the quick reply.

The goal of this project is to build a pair of 3-way that are a similar size of some really old, really poor quality speakers my father-in-law currently has.

They measure 13" wide x 11.25" deep x 21.25" tall, which, when using 3/4" MDF, results in approx. an internal volume of 1.44 ft3 or 40 L

I started looking at the Dayton 8" Woofer (Vas = 2.04 ft3, Fs: 29 Hz, 88 SPL, 29-3,000 Hz, Xmax= 4.5 mm, Qts: 0.38, Qms=3.23 & Qes: 0.44

The Dayton 8" looks interesting because they are inexpensive, have a low freq. range and are inexpensive.

Playing with WinISD, a volume of 30L gets a F3 of 33 Hz :cool:

Keeping the same width and depth, after the 30L, I have only have about 7 inches of height to use for midrange and tweeter, assuming that I made two different volumes inside the cabinet.

What inexperience options to I have for sealed 5" midranges? I do not have my catalog around, but they usually describe the speaker as sealed? I plan on buying a 3-way cross-over with 375 & 3,000 cut-offs.

What happens if a 8" and a 5" midrange share the same volume?
 
AndrewT said:
Are sealed mids common?

Morel do a reasonable dome mid that's sealed, and I think Vifa do one as well. Of course there is the ATC, but just one would cost more than the entire rest of the system!

The box size for the mid can be quite small for your planned crossover point, just model a few drivers and box sizes to give a smooth roll of at about 300Hz. It might well be as small as 1/2 a litre or so.
 
Why not just build a separate chamber within the box for the midrange unit? The box you are planning to build will realise 40L and you need only 30L, so there's plenty of scope. A vertical partition between a shelf-brace and the top of the cabinet will work just fine. The extra volume behind the mid will provide more space for fill than any enclosed mid driver could muster for effective absorption of the back wave.

James
 
These are wonderful responses, thanks.

I had thought today sitting at my desk. I can make a separate enclosure and adhere it the back of the front baffle, not sure why I did not think of that earlier. I am thinking about using the Dayton DA135-8 5.25" Woofer (8 ohms, Fs= 53 Hz, Qts: 0.46, Qes: 0.57, Qms: 2.40, 50-15,000 Hz). With a sealed enclosure, it requires 5.2 L, which is not to bad.

I will do some calculations to see if I can come up with a cabinet size I like.

Thanks for your help!
 

RJ

Member
2004-10-19 4:29 pm
I've used a few of those Dayton 5 1/4" Aluminum Woofers.
They sound very good. The upper limit is 2500 hz.
That's where I crossed mine at. 4th order Bessel.
 

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Thanks RJ - I think I want to hear from someone that has a little more expereince with those woofers - you have only used 20 of them! ;)

Why do you say they are only good to 4k? The freq. range is 50-15,000 Hz. I was thinking about using the Dayton 3-way croos-over with a low point of 375 and a high of 3,000 Hz.

Do you know any other companies that seel pre-assemblied cross-overs that may have a few more options?
 

RJ

Member
2004-10-19 4:29 pm
4th order Bessel is a crossover slope of 24 db per octave.
All metal cone speakers have a breakup mode at higher frequencys.
If you look at the frequency response for the Dayton 5 1/4" Aluminum speaker you will see it start falling at 2000 hz. It finally hits a low point at 3800 hz. Then you'll see some erratic & jagged peaks starting at 4000 hz and up. The jagged part is what you want to supress with a crossover. I don't think 3000 hz 2nd order (12db) will do it. You'll need a steeper slope like a 3rd (18db) or 4th (24db) order crossover to supress that breakup mode.
You'll have to make your own crossover. I don't think they make prebuilt crossovers with steeper slopes.
Also a three way speaker design is very complicated to assemble from scratch. It's far easier to build a two way with a subwoofer.
The three ways you see as projects by other diy'ers are by people with very good modeling software and speaker testing equiptment. There are free modeling software and testing software (Speaker Workshop), but it still takes a fair bit of knowledge and a lot of experimenting to get a feel or handle how speakers can be built from scratch.
You can either dive in and start to learn the craft or you can start with a predesigned speaker by one of the online guru's. I just dove in and learned as I went. Theres alot of good and knowledgable people out here to help you along the way.
Those line arrays were my first project. I went through 5 subwoofer enclosures to see and hear how they sounded. I finally settled on a Mass Loaded Transmission Line and I've also built 3 different MTM's to see how they sounded. As far as crossover work I use the free spreadsheet program by Jeff Bagby and I use the Radio Shack Decibel Meter to calibrate my crossovers.
I don't know how far or how deeply you want to get involved, but we're here to gladly help you along the way.
Rudy