Help: Building speakers using 8" woofer, 5" mid & 2" tweeter

[tripslipfall]

Hey, this is my first post here, and I'm looking for some ideas on building custom boxes for my speakers.

I would like each speaker to have 1 8" subwoofer, 1 5" midrange and 1 2" tweeter.

I already have the drivers I would like to use, I have some older (maybe 6-8 years old) Rockford Fosgate 8s, and some 5" midranges & 2" tweeters from some speakers with blown woofers.

I'd like the speakers to be able to hit lows nicely and still be able to have good mid-level bass.

These are only going to be used for music, mostly rock & rap music.

Any help would be greatly appreciated, and if anyone has built speakers like this, please tell me your box dimensions and let me know how they turned out.

Thank you very much.

[ThomasW]

Speakers are designed by taking frequency response measurements of the individual drivers mounted in the baffle where they'll be used. That data is then imported into a software program and used to create a first pass crossover design. Once that first crossover is built it's performance is measured and a decision is made regarding any changes.

Doing this with your drivers requires an investment in test equipment that would exceed the value of the drivers you want to use.

For the first time builder it's a good idea to build a proven and tested design. You'll find a list of those in our missions accomplished section of the forum.

[pres589]

Here's my advice; lurk around here for a while before posting. Lurk around the Part's Express chatty board for a while as well, it's a little more in tune to the needs and ideas of newbies, I think. You can find it here;

http://techtalk.parts-express.com/

Next up, and it's already been mentioned once and I'll be shocked if it isn't mentioned again, for your first build-up you should probably copy an existing design. Read the comments, maybe search around for a while and check out info about DIY audio events so you can get a nice collection of speaker opinions quickly, that kind of thing.

There's a crossover network to figure out and that's going to be "fun", there's the problem of not knowing anything about your current drivers (we've got a brand and diameter on one, that's it, and it's probably the most forgiving to screw ups. Dealing with 2 inch tweeters, whatever the type and I bet they aren't some soft dome that's generally more forgiving than other types, etc etc)... the list goes on and on. You may be able to turn those drivers into a decent full range speaker. But you've no idea what lies in store for that kind of effort.

I'm still in lurk mode here, I probably won't come out of lurk mode for a while, and it's going to be something simple and small. I really don't mean to rain on your parade, it can be discouraging to hear, but it's going to be a lot more fun if you build something that is proven to work and just fight through the issues of getting a crossover assembled correctly, getting an enclosure built that you're happy with, and other issues that come along with this sort of thing.

[Undefinition]

I wrote this only to help:

The Most Frequently Asked Question in DIY Audio

http://undefinition.googlepages.com/diy-mfaq

[---k---]

Paul,
I was just about to post that. You beat me to it.

[bluewizard]

The underlying problem is, you can't just take random bass, mids, and tweeters and throw them together.

For example, let's say you have a woofer that functionally goes from 30hz to 1000hz, and you have a Midrange that functionally goes from 2000hz to 6000hz. Can you use those drivers together? The answer is NO, because there is a glaring gap of 1000hz between the end of the woofer and the beginning of the midrange.

Now, what you propose could be done, but you would need more information than you seem to have. You would, bare minimum, need to know the crossover frequencies of the existing speakers, and hopefully, the slopes of those crossovers. That would give you a basic Go or no-Go on the speakers.

If those crossover frequencies are compatible, with no gaps, then you might have a chance of pulling this off.

If you have any specifications on the two speakers, or if you can get those specifications, there might be a slim chance of this working. Many manufacturers still have information on older models. Also, there are vintage speaker sites on the net that might have that information. But that is your starting point. If you can't at least get some sense of the existing crossovers for both speakers, then you can't determine whether these speakers will work together.

Steve/bluewizard

[tripslipfall]

Well I have no idea what manufacturer made the mids or tweeters, no numbers or brands on them or the original boxes they came in, and when they are all ran together without a box or crossover it sounds good, but of course there is no bass, this is my first project and I'd just like to see how it turns out.

I mostly just need to know what to tune the box to for good low bass, someone told me 20Hz, but I feel that's too low, but it might not be.

[tripslipfall]

Oh, and I guess I could run some tests on WinISD and see where the woofer & midrange cut off at. The mid and tweeter came together with some old blown speakers so I already know at least they will work together.

[ThomasW]

WinISD doesn't test anything it just simulates the performance of the woofer in a box.

Hard to tell you what box tuning to use because that's based on knowing among other things how much the woofer's cone will move =Xmax.

FWIW drivers never have the information printed on them that's needed to design a crossover or the box.

Do you have a multi-meter so you can at least measure the resistance of each driver? If not there's little point in continuing this discussion.

[tripslipfall]

I already know the midrange and tweeters are 8 ohms, and the Rockford 8s are 4 ohms.

Do you have any ideas on how I should check to see what the frequency range is?

[tripslipfall]

Hey, I got lucky and found some info on the Rockfords.

Nominal Impedance: 4
Fs (Hz): 30
RE (Ohm): 3.6
LE (mH): 2.5
QMS: 4.89
QES: 0.32
QTS: 0.30
VAS (cu. ft.): 0.883
VAS (Liter): 25
Power Handling (RMS): 200
Power Handling (Peak): 400
SPL (dB @ 1 W/1M): 85
X-MAX (inches): 0.32
X-MAX (mm): 8
Speaker Displ. (ft3): 0.05

[ThomasW]

Tune a ported box to about 32Hz. Use a 3" diameter port.

BTW regardless of what Rockford calls it, it's a woofer not a subwoofer.

[tripslipfall]

Do you know of any box designers / calculators I can use that will help me?

[kevinp.]

check the faq thread at the top. WinISD is a pretty simple box design program.

[tripslipfall]

Tune a ported box to about 32Hz. Use a 3" diameter port.

BTW regardless of what Rockford calls it, it's a woofer not a subwoofer.

Would it be ok if I used an L-Ported box tuned to 32Hz?

[ThomasW]

Sorry but I've never heard of an ' L-ported' box. What is it?

[tripslipfall]

It's a box with the port made in the shape of an L. Here's a simple example. http://i37.tinypic.com/20zzev5.jpg

[Hdale85]

That would be a vent.

[tripslipfall]

Yeah I know, but in the 12 volt world, it's called an L-Ported box.

[ThomasW]

It's known as a slot port.

If you know how to model one fine. I think a length of pvc pipe is a lot easier to model and to install