I'll try and put together something later on on my budget arrays, .. but here are some random thoughts on building line arrays on the cheap for those of use who cannot, or chose not to, invest in a full blown array.
1. A critical issue when building arrays is the choice of tweeter - woofer crossover point . Jim Griffin's white paper goes into the details but basically, the larger the woofer (more / deeper bass), the earlier the roll-off when arrayed. Consequently, the tweeter must be crossed over lower. The problem is, tweeters that can be crossed over lower tend to be more expensive, .. and this really adds up in an array. Another issue of a lower crossover point is that the cost of passive crossover increases (if you use a passive crossover, that is).
Solutions (and their potential disadvantages):
2. Use a single fairly efficient tweeter (like Fred's budget arrays) . Disadvantages: a) different dispersion pattern b)the single tweeter will probably not project as far as the woofer array, and level adjustment may be needed for different rooms.
3. When arrayed, cheaper tweeters can be used somewhat lower than a single unit,.. as the power delivered to each driver is substantially less. Just don't take it too low. Another possibility would be to add a simple wave guide to the tweeter line to boost power handling and response.
4. Use a woofer with a rising response to counteract the array rolloff. That's the way I went in my project, and I still have a bit of a dip around 4KHz -5KHz before the tweeter line takes over but I consider it more like a" BBC dip of sorts", not really obnoxious. Disadvantage: Potentially, you could have a non uniform dispersion patterns , .. but I don't seem to find this an issue, or maybe I don't have golden ears.
5. Use a smaller driver. IMO, 4" woofers are the "sweet spot" for building budget arrays if you want to cross over to a line of tweeters, because they allow you to cross over fairly high (say 5KHz) without compromising on the array design. Also, budget drivers in this size tend to sound a bit better than their bigger brethen, and cabinets can be made somewhat smaller. Disadvantage: BASS !! - the array might sound plenty dynamic, but don't expect to shake the walls. Of course, a discretely placed sub or two should be able to fix this. Also, while they cost less, they are also smaller and you may need more of them to make up a specific array height.
6. For budget arrays, I feel that you can get a good percent of the benefits (dynamics, wide sweet spot) by not going for a full blown 6 - 7 ft anti-WAF weapons, and instead keep the size down to a more domestically acceptable 3.5 - 5 ft. Make sure that the tweeter or tweeter line is inline with your ears in the sitting position. Disadvantage - if you stand up, you will probably notice the sound collapse.
On the treble side, if you chose to use an array of tweeters, be aware that the tweeter line maytend to roll off a bit on the top end depending on response characteristic of the individual driver and also the driver - driver spacing. There are a few different ways to address this IF you find this an issue. You may not run into this issuein certain if for instance, your tweeters have an extended high freq. response and / or can be spaced extremely close (maybe trim the flanges), if you use a single tweeter to match the woofer line or if you use a line ribbon or planar, tweeters.
1. Passive tweeter compensation - haven't tried this, .. no comments
2. Electronic EQ - should work well, provide you don't overdo it and of course, own such a device
3. Use the treble control judiciously, if you have one - that's what I do - afterall all, my array's are budget :devices)
4. Add a supertweeter crossed over high, .. somewhere about 12 - 14KHz 1st order - I've done this with my pair of radioshack supertweeters. Unfortunately, their levels weren't matched so I grudgingy removed them and hooked up a pair of fountek JP2 ribbons that I picked up locally for a good price.
Hope that helps.
