Fostex "boiler plate" speakers

[aeronautical]

Two 15's...you're an animal! Just kidding of course.

Is there a place to get recommended box plans for the AE Llambda's?

My crossover is a Heathkit AD1702 which I built in about 1981

[Pano]

OK, let's not talk about the twin 18s, then.

I guess you'll have to ask the AE guys. They have several 15s, you might have to ask which is best for your application. Box size, type, crossover frequency.
Are you willing to go the digital crossover route?

[aeronautical]

I am open to anything at this point. I actually love my crossover and might clone it. I have the details to scale the crossover frequency all the way up to about 5k which would easily get me in between the mid and high. People kinda look off when I tell them my crossover is a Heathkit but it is a fine little box: Heathkit AD-1702 Crossover That site isn't me by the way.

So I could make two clones, one for the bottom the other for the mid to tweeter crossover.

I am not familiar with digital crossovers, could you enlighten me?

[planet10]

Originally Posted by Pano

Two 15s even better. There are some advantages to a dual 12, but the single

I like dual woofers. I can mount them push-push although it creates another limit to how high they can go.

dave

[Pano]

Originally Posted by aeronautical

I am not familiar with digital crossovers, could you enlighten me?

Sure.

Digital crossovers make use of DSP (Digital Signal Processing) to give the crossover huge flexibility. That means things like:

• A large variety of slopes, 1st, 2nd, 3rd, 4th and higher orders
• Different types, Butterworth, Bessel, Linkwitz-Riley, custom types
• Fine adjustment of crossover point
• Independent points for each channel
• Easy phase and delay adjustment for each channel
• Shelf filters
• Parametric EQ

That means you can fine tune and choose exactly the filter function you need. That can be very important and is a huge advantage over typical active crossovers. You may need a 4th order high pass and a 1st order low pass on some section, a notch and a shelf on another. All done with the click of a mouse or the push of a button. Sort of like writing a book on a typewriter vs a word processor. The typewriter has its charm, but the ease and power of the word processor has won most of us over.

What the digital crossover allows you to do so quickly and easily is measure your drivers, use some free software to find the electrical function that gives you the acoustic slopes and responses you want (very important), then implement those with the crossover. Presto! You've got a good crossover. You can refine it to your heart's content, or just change it to something else.

Different digital crossovers have different configurations. All I've seen have analog outputs, some have digital inputs or analog, or both.
Probably something like the miniDSP (revB) would be great to get you started. It can work as a stereo 2-way crossover. You can cut in the super tweeter with a simple passive filter tapped off the horn. Or you could buy 2 and have a stereo 4-way crossover.

Include in the budget a measurement mic and a soundcard with a phantom powered mic input. Oh, and a mic stand and some cable. That's all you need, apart from some free software. It's all easy to use if you have someone talk you thru it. I've taught many measure and design over the phone or by email. And there is plenty of help right here on the forum.

[aeronautical]

Thanks so much for that. I feel like Rip Van Winkle...a lot has happened since I was in audio other than as a consumer.

I read all about that crossover. Looks like it would take a lot of expensive mistakes out of the equation. Am I wrong or with two of those and three amps and you have a labratory. Back in the day we used calibrated microphones. I assume you mention of a mic setup does the same by giving you measurement feedback on how your doing. I am assuming there are no serious down sides, like switching noises, phase shifts, etc..

I like this approach. To be honest I was intimidated by perfecting my own passive crossover because as you change one tiny thing the rest of the world is affected also.

Now it's down to drivers and boxes.

[Pano]

And the horn! I really do recommend an Iwata or JMLC horn from the source in Poland. Paper Mache horns are very good, too (and cheap!) but are labor intensive, for sure. Real DIY.

There are no serious downsides that I know of to the digital filters. The weak points of some, like the DCX2496 are its analog section and power supply. I have not worked with the miniDSP, but so far no one has reported those same problems.

Yes, a calibrated mic. You can pick one up at Parts Express. I also use a cardioid mic, audio cretin that I am, because it gives me better results in-room. Omnis are great for anechoic and free field, not as great for real listening rooms. I use a simple little AT2020 mic that I checked against a known cardioid (Shure SM81). It was so close to published specs that I just use those.

A couple of my friends use the A.E. 15s and are very happy with them. I've heard them and like them. Not sure which to choose for your project, tho.

[aeronautical]

The reviews online are certainly impressive for the ae drivers. I wonder how they compare to the Fostex which is where I thought I was initially headed. They are a fraction of the costs which is very appealing too.

They (ae) also have a 6.5 inch mid. What would your thoughts be to do the two 15's and a line array of 6.5's for the mid and maybe planars, domes, or horns for the highs?

Anyone?

[Pano]

Gary Pimm in Portland has one of the cleanest, best sounding systems I've heard in years. Can play very loud, too, with no strain. Does soft like a charm. And not a horn in sight!

2 A.E. IB15s per side in a nested H frame (hard to describe)
1 Eminence Beta 8 wideband midrange, open back.
1 Hi-Vi planar tweeter circa 5Khz.
Pretty simple crossover for mid and tweeter, DCX2496 for woofer x-over and EQ.

Gary designed and built much of the electronics, too, which doesn't hurt.

[aeronautical]

Clarify something for me if you would please: With as much bass as would be on tap with two 15's, wouldn't it need more mid's and high's too. Is a line array a good solution or am I just being silly?