Well I have been wanting to get into audio for a very long time and I think now is the time. I'm getting close to graduation (B.S. in Electronic Engineering) and I think that combined with everything I've learned in school, a great hobby would be speaker design. I really need something useful to occupy my time on the weekends when I have a job.
I want to start off with a simple two-way bookshelf type speaker design and then later on add a separate sub woofer. I am not really quite sure on the crossover yet. I think I may design it so that the woofer is ~45Hz-2,500Hz and the tweeter from ~2,500Hz and up.
This may be a dumb question, but would it make sense to have the woofer at let's say, 45Hz-2,500Hz and the tweeter at 2450Hz and up? Would there be a smoother frequency response curve at the crossover point with a lesser drop-off?
Let me show you the speakers I want to incorporate (through browsing the parts-express website).
Tang Band 25-302SH 1" Shielded Neodymium Dome Tweeter
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-804
Tang Band W6-789S 6-1/2" Woofer
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-852
This is my idea, quickly drawn up in Paint:
I don't know if this is a good idea or not, but to me it sounds reasonable. I want to build a separate box for each speaker (tweeter and woofer), as you can see in the picture on the left. These two boxes would be mounted inside a larger "container" box and secured to prevent any shaking/vibrating/etc. The crossover would most likely be mounted inside the larger "container" box with wires running up to their respective speakers.
I think this would be a good idea because I would be able to model a box for each separate speaker, providing me with a better design and a box tuned to each speakers' specifications. Would something like this work or do I just have the completely wrong idea?
Let me know of any suggestions. Thanks a lot.
Unfortunately you have a lot of wrong ideas.
First of all a tweeter does not need an enclosure.
The next thing is be careful of Tang Band drivers. These are Chinese designed and built drivers. Their specs are rosy, that is their reputation. Unless they are a lot better at making drivers than anybody else you absolutely can not trust the frequency response curves. Just take the tweeter, which has a Fs of 1400 Hz. You can see it in the impedance curve but it does not show up in the frequency response curve. Any way a tweeter has to be 24 db down by cone resonance or it will sound very harsh.
The next point is that the woofer will need to be reflex or TL loaded, it is not suitable for a sealed alignment. Fs is 45 Hz, so in fact you practical F3 will be somewhat higher. I don't trust the frequency response curve posted for that driver at all.
If you want to build a speaker round these drivers you will have to measure them before doing any design. That includes T/S parameters and frequency response.
Now the function of the crossover is two fold.
One is to keep the drivers in their usable pass bands, including deal with problems such as break up modes within at least 24 db for each driver either side of the crossover point. I'm talking here about notching out break up mode resonances etc.
The next function is to sum the drivers to a flat response either side of the crossover region. Now this is tricky, as the crossover has to work with the
acoustic roll off of the drivers to sum to flat. Say for instance a woofer has a second order roll off and our tweeter first, then the low pass needs to be first order say and the high pass second order. It often gets more complicated
than that, as the acoustic roll off of drivers frequently change orders, and then so must your filters.
You frequently have to compensate for the impedance rise of woofers with frequency, so your low pass filter can even work.
Now you have to do all this doing a little violence as possible to time and phase. You usually do quite a lot!
The crossover is the heart of the speaker, and by far is the toughest challenge to design, and takes experience.
The easier part is modeling the box, however that has to be done right as well.
I would suggest you look at Scandinavian woofers like those of a manufacturer like SEAS. SEAS specs are renowned for being brutally honest.
I would purchase drivers from an outfit like Madisound. They have no complete rubbish in their catalog.
http://www.madisound.com/?gclid=CKaH2eSh3ZMCFQKaFQodHRg4ZA
Before proceeding further I would do a little reading. Since you are an engineer it will all make sense to you.
Here is a good place to start.
http://www.audioxpress.com/bksprods/BKSLOUDES.htm
I particularly recommend Vance Dickerson's loudspeaker Cookbook, and Bullock on Boxes.
Loudspeaker building is great fun. Every enthusiast should design at least one set of speaker. If you are like me however, you will always roll your own.
You have to be prepared for some failures, especially at first, as you gain experience. However you are just out some time and wood, the other parts can usually be recycled into other designs later.
One other tip, is leaning how to choose drivers that have a decent chance of working well together with a relatively simple crossover. Careful driver selection, and taking time over it, really pays dividends, and gets you off to a good start.
