How to Select Drivers

[SonicBooMan]

Thanks for all the great advice!

OK, I'm a neophyte in the DIY speakers. I've done some reading, but the books I've checked out from library are quite technical...formulas? yikes! I've read other materials but still have some nagging, unanswered questions.

Anyway, I thought that this new thread might help those of use who are beginners.

1. How does one go about selecting drivers without spending an arm and a leg? There are a plethora of drivers and price variances; and I certainly don't have the cash or time to test most of them.

2. What are the criteria for selecting drivers?

3. How can I tell (or guestimate) the sound quality of a driver without first hearing it? Does price play a significant role in the driver's sound quality? For example, I looked at the frequency response curve of the Dayton RS 8 & 10" drivers, and compared that to the SEAS Excel series 8 & 10" drivers. The curves show similar responses, yet the prices are sky high for the Excels.

4. How are drivers' physical dimensions specified? For example, is an 8" driver from manufacturer A the same size as an 8" from manufacturer B? Are the mounting flanges have the same dimensions?

5. How do various driver's components affect the sound quality? (e.g., aluminum, textile, paper, magnesium, others).

6. Do size of magnets matter?

Please post other helpful information.

Thanks, again.

SonicBooMan

[cjd]

1. How does one go about selecting drivers without spending an arm and a leg?

Close your eyes and become one with the force. Let all the good drivers come forward. If that fails, you browse forums and read what others say. Or just up and ask. If you want cheap drivers, you can just pick cheap drivers. Don't forget, a quality crossover isn't cheap either.

2. What are the criteria for selecting drivers?

THE criteria? That they're perfect! Sooo many variables. And everyone has their preferred flavor. There is no single answer.

3. How can I tell (or guestimate) the sound quality of a driver without first hearing it?

You can't. Not really. Response curve, distortion, impedance, all tell tales. You can probably get a pretty good sounding driver looking at these things, if you know what you are looking for.

Does price play a significant role in the driver's sound quality? For example, I looked at the frequency response curve of the Dayton RS 8 & 10" drivers, and compared that to the SEAS Excel series 8 & 10" drivers. The curves show similar responses, yet the prices are sky high for the Excels.

Well, you now have the "yes" and the "no" answers figured out.

4. How are drivers' physical dimensions specified? For example, is an 8" driver from manufacturer A the same size as an 8" from manufacturer B? Are the mounting flanges have the same dimensions?

Most will give you actual dimensions along with whatever size they decide to call a driver. They're not guaranteed to be standard at all.

5. How do various driver's components affect the sound quality? (e.g., aluminum, textile, paper, magnesium, others).

6. Do size of magnets matter?

Please post other helpful information.

Read those books. If you're reading math stuff and it doesn't make sense, skim through it and don't understand it, but keep reading. Proper answers to your questions take a book to answer thoroughly. Read some other stuff. Then go back to the sections you skimmed to see if they make sense yet. You can grasp a healthy portion without understanding the math thoroughly. Every time I think I understand something, I come across some new bit of knowledge that proves I only knew a little. I can only assume this will continue.

C

[Dennis H]

You're asking the right questions.

The thing to realize about cone drivers is that, at low frequencies, they act like a rigid piston and at higher frequencies they start to "break up" i.e. not all parts of the cone are moving the same direction at the same time. Distortion rises when that happens. There are two general schools about picking cones. One camp prefers soft (paper, polypropylene, etc) cones because the breakup is gradual and they tend to have a smooth frequency response. The other camp prefers rigid cones (metal, carbon, etc.) because they will act as pure pistons to a much higher frequency than the soft cones. However, once the rigid cones do break up, it's really nasty and it takes extra crossover components (and design skill) to suppress that breakup. By contrast, crossover design for a soft cone is relatively easy. So it's one of those engineering tradeoffs. Hard cones potentially sound better but only if you have the skill (and money) to deal with their nasty characteristics up high.

You'll find that our resident guru, Jon, is in the hard cone camp.

The other part of the equation besides cones is motors (magnet and voice coil.) Some motors have more distortion than others. The details are too complex to go into here. Forum member Capslock is really into motors so read his postings to get an idea of the issues involved. Just be aware that price isn't necessarily an indication of which is better.

Just some food for thought to help you realize that easy questions don't always have easy answers.

[JonMarsh]

And when you're ready to wrap your mind around test data, check out MFK's site for his projects and testing, as well as MarkK's. Google is your friend.

Then, there's the LDSG guide, (Loudspeaker Designer Selection Guide) with all kins of data and links, and educational commentary:


LDSG



There's quite a few driver discussion threads on Mission Possible DIY, so reset the thread dates to go back a year a so, and do some browsing.

[taz13]

And for a whole list of links that might help.

http://web.telia.com/~u87124019/diy.html