Speaker comparisons?

Hi guys.

I'm trying to get my father to go in with me to build some speakers for ourselves.

What I really need to know is, can I compare the speakers available from Parts Express to professional brands?

Klipsch, KEF, Infinity, B&W?

Say a $30 Audax 6.5" Woofer. Does that compare to a Klipsch 2.5's drivers or Infinity's "Best Buy" models? Or is it more like B&W bookshelf speakers? I have no idea.

Here's a link to the Audax speaker:

I have a pair of Klipsch 2.5s. I'm thinking about taking one driver out and measuring it's Thiel-Small numbers. That would give me a good idea.

In the mean time, can anyone answer this?

Measuring the T-S parameters of the drivers in your Klipsch won't help unless you're planning to take the drivers out and build an entirely new cabinet for them. (In the same way that the gas mileage a car gets doesn't tell you a thing about the quality of the car.)
Audax is used in a number of high-end lines (e.g. Nearfield Pipedreams). I'd take Audax drivers any day of the week. They'll be a step up (perhaps two or three) over the drivers in the Klipsch. Vifa is also good. There are two or three other lines that are of that same caliber.
That said, you may not be entirely happy with the sound of a speaker made with such drivers. Why? Because you're used to the Klipsch, and Klipsch have...well, they've got a bit of an elevated high frequency due to distortion components from the horn tweeters (nothing's free, and the price you pay for the efficiency of a horn is in distortion--it's the usual tradeoff where Mother Nature giveth with one hand whilst taking away with the other). Other speakers may sound dull and uninteresting to you by comparison. Judging from comments you've made elsewhere, I suspect that you've already found this to be the case.
To me it's an open and shut case, but to you it may be a bad deal. Give it some thought before proceeding, as I'd hate to see you put in a lot of time and effort, then be unhappy with the results. You'll get a *completely* different sound from what you're accustomed to. If you're intending to use the new speakers along with your Klipsch (AV 5.1 system), I would go further and sorta advise against it, as the tonal balance won't come close to matching. They say you're supposed to use similar/identical speakers for 5.1; I cheerfully break that rule for my AV here because AV isn't as important to me as music (totally separate systems). It may or may not be important to you.
Back to you.

Actually Grey, your comments helped a lot. I'm not really wrapped up in Klipsch as much as you think. I like a lot of different brands. The new Klipsch are terrible. Anything within the last 10 years has lost the original sound. They used to go for a flat response, now they go for sensational volume.

If you say the Audax is better than the Klipsch then, great. That's what I'm looking for. I'm building a Hi-Fi system for my living room and mains or a center channel for my father.

BTW, Eric, I couldn't get to that link. It must have been down.

The reason I wanted to measure the T-S parameters of my Klipsch woofer was because I noticed an almost linear relationship with Qts vs. Price. The lower the Qts the higher the price. So, measuring the Qts of my Klipsch would give me a general idea of how much they would cost. Don't challenge me on this. I only looked at Audax and the relationship wasn't perfectly linear.

No one answered my question though. Is the $30 Audax better than my Klipsch? Or do I need to spend more than that?

I too was considering this. The LDSG page was VERY helpful. When it comes down to it though, on a first time (or 20th time) diy project I dont think you will be able to replicate the sound quality of the higher end loudspeakers. They can just spend much more time and money working out all of the little resonances and quirks of the individual drivers, cabinets, and crossovers. If you've got a lot of time, a quality RTA, and a reasonable knowledge of acoustics, then definitely go for it. Good loudspeaker design goes FAR beyond the selection of drivers.

I dont mean to discourage you because I fully intend to build a center channel, surrounds, a sub, and a full computer speaker system myself. But for my musical speakers I am going with a professionally engineered setup. (probably Martin Logan aerius i's)