Attenuation

[Nappylady]

I'm currently building a pair of very big 3-way speakers with the goal of good sound and high SPL. (If the sound is superb that's a plus, but I'm only going for good.) Oh, and cost. The cost is a huge factor; all the drivers, horns, and crossovers (I've already bought them) cost me less than $200.

The problem I'm having is that while the woofer and horn tweeter are efficient to about 93 dB, the mid-horn (hehe) is efficient to 110 db. (!!!!!)

The mid-horn itself is 6.1 ohms DC resistance, and by my calculations, I need something like 5.97 ohms in series with that, in order to reduce the output to the level of the other drivers. Question 1: did I do that calculation right?

Next question: how's the best way to attenuate this? Ideally I'd build my own active crossover and then triamp the thing (*droool*) but alas, I have not got the money to do such a thing... I'm thinking that if I go to my local art store and buy some BIG pieces of graphite, I can use them as series resistors next to the driver to cool off the sound some.... I mean really, it sounds terrible with the midrange so loud and the treble so wimpy....

Last question: anyone interested if I dig up a digital camera and take some pictures?

[FrankDIY]

Normally you use an L-PAD. One resistor in serie and one in parallel. 10W resistor a normally enough. From my experience, it is hard to calculate the good value because of many factors. Simply buy a variable L-PAD and adjust to taste. When the sound is fine, read the resistor value on the LPAD and then build a fixed LPAD with standard resistor.

[Nappylady]

Thanks...

I actually discovered that if I take a piece of foam left over from the project, and shape it to fit the throat of the horn, and then jam it in there, it gives about the attenuation I want. :-)

I'm afraid I have neither the money nor the time to spend getting L-pads, and I suspect they wouldn't give the range I wanted anyway; it doesn't matter though, my problem is basically solved.

I spent less than $130 on all the drivers for these boxes, and when you wrap it up to high SPLs, it really shows, especially to people who are spoiled like me. :-) The higs and mids sound like someone is going "WSHHHSHSHSHSH" out of the horns. It's very yucky. These are $5 ABS horns and I can tell by looking for 5 seconds, they are NOT shaped right.

Oh well. It's for dance parties and I don't think they'll care a whole lot.

Pictures? Pictures coming.

Thanks again!

[FrankDIY]

LPad are not so expensive. The 15W one are around 3-5$ and you need only one to "debug" you crossover