Reply posted by D. Parker on August 19, 2000
As far as crossover points goes, you need to look at the manufacturers specs for the drivers you have. Some speakers don't just fall off, some have peaks that you would want to crossover below.

Your high frequency drivers crossover point would also depend on how much power you are going to throw at them. The lower the crossover point the more power it takes. Since the horn drivers are the weakest link in your chain, you have to cross them over low enough to get the sound you want, but high enough to keep from melting them down.

The manufacturer has the specs to help you dial this in. Larger drivers such as 15's will distort as the frequency goes higher. You want them crossed over below this, but not too low as to overload your mid drivers. Manufacturers specs aren't hard to find and will help.

David

Reply posted by Miles Langham on August 19, 2000
Now here is what I was looking for!!

Thanks. The local guy I bought these from is busy as can be right now. It's hard to catch him with enough time to ask questions.

Many thanks David,

Miles

Reply posted by ivan beaver on August 19, 2000
You cannot trust what the Autograph is telling you as far as your frequency. This is not saying that it is not accurate but ANY 1/3-octave analyzer will not give you accurate results because of the amount of the overlap of the filters. These filters are not nice square chunks of sound as we would like to believe.

You need a much higher resolution filter to get real results. Smaart or the Audio Toolbox are some inexpensive tools that can get you much better resolution. You need at least 1/12 octave to get minimum overlap. Simply prove it to yourself.

Put a 1KHz tone (or any tone that is on as ISO center) and look at the display. Do you only see the 1KHz row of LED's light up? No, you will see bands on either side of it lighting up to lesser and lesser levels as you move above and below it. So why am I reading 800 Hz on a 1KHz tone? It is because the 800 Hz filter is overlapping the 1KHz one.

Without a better test setup you are better off doing as the previous post said and use the particular manufacturers recommendations as to the high and low limits of the particular drivers-and then maybe listen to them closely and fine tune to your taste.

Reply posted by D. Parker on August 19, 2000
-"Put a 1KHz tone (or any tone that is on as ISO center) and look at the display. Do you only see the 1KHz row of led's light up? No, you will see bands on either side of it lighting up to lesser and lesser levels as you move above and below it. So why am I reading 800 Hz on a 1KHz tone? It is because the 800 Hz filter is overlapping the 1KHz one."

That's why I say it is important to use an RTA to find feedback frequencies. If you do it by ear, maybe the offending frequency is 1k, but you grab 800, notch it, the feedback goes away, but if you would have grabbed the 1k, you wouldn't have had to notch it as far to get the same feedback reduction.

David

Reply posted by Alan Wheeler on August 19, 2000
I agree with Ivan - if you can afford it, buy Smaart Pro. You won't regret it. If its out of budget, then see if someone with it can help or if you can borrow or hire it. You will learn so much about what the speakers are actually doing and this will help in understanding what is going on in an environment you are trying to mix in.

I'm sorry, I'm not sure if you said if your X-over is DSP based or not, but if it is then you can set so much up with the program and really make the system sing. Also as David has said, the X-over points need to be set within manufacturers specs and then within those specs you can play around with the "anomalies" of the drivers. Go outside those specs and you could cause damage.

Wheels

Reply posted by Harry on August 20, 2000
Miles,

In addition to several other posts, I offer the following.

Pay special attention to horizontal dispersion when setting your crossover frequencies. The high frequency horizontal dispersion should match the mid frequency horizontal dispersion AT the crossover frequency. This is essential for consistent coverage, especially in the vocal region. 15-in drivers tend to beam at lower frequencies compared to 12-in drivers, and the same goes for 12-in compared to 10-in.

If the cone drivers are horn loaded there are other factors to consider. Also try to get the SPL from the individual bands to match AT crossover frequency. This will give you the best starting point. After that you can do a better job with your EQ.

Even if you have DSP based crossover/ delay/ EQ for your system, you would still be better served by starting with these basic techniques. If you have better measurment tools such as TEF, SMAART, Iasys, etc., you may be able to get into overlapping crossovers, crossovers with different response curves (ie. butterworth, L-R, Bessel), as well as more accurate delay between passbands. This is the type of processing the larger speaker manufacturers are doing at this point.

I think even Tom Danley is doing this with his TD-1 product, although he is doing it with math, physical alignment, and passive electronics in the cabinet,...an even more complicated and time consuming endeavor.

A DSP based speaker processor, and several hours of FFT based measurement will go a long way toward getting your system sounding great.

BTW, it is possible to do all of this with a pair of ears and a brain.

Harry
PS - Do this "initial" setup outside, in a large unobstructed area, if possible.

Reply posted by Another Dave on August 20, 2000
Miles,

Once upon a time, before the subwoofer/fullrange topbox idea took hold, the type of system like you have with one type of box per passband was very common. Lots of 'em were home brew, and many sounded quite good.

Many bands in the 70's moved from Altec A7 woofers & 511 horns to JBL Perkins with 2441's on top. Those that really "made it" were able to get Martin two 15-in "shotguns" & philishave mids. A lot of the plans for these boxes were available from the driver manufacturers for free, in the hope you'd buy their drivers to load them.

Once you get the polarity thing straight, (see the link below) crossover points can be set by ear if you have an analog crossover with sweepable points. The 15-in and 10-in cones will most likely be working well within their respective response parameters. Most 15's will go up to about 1KHz, and if your crossing over to a 10-in, you'll most likely only be going up to about 200 or 300 Hz.

Some 10's can go up as high as 6KHz, but get pretty "beamy" past about 3KHz. Your horns could very possibly go down to 500 or 800 Hz, but crossing them over higher will increase the power handling of the horn. Do the best you can to get the response information on your particular drivers, and LISTEN!

In my experience, I always seemed to end up with crossover points of 200-250Hz, lo-to-mid, and 2-2.5Khz, mid-to-hi.

Having your crossover at FOH is essential for this type of rig, IMO.

Here is a small piece of info I learned early on in my career. ALWAYS CHECK THE HIGHS FIRST. This way, if anything is mis-wired, the highs won't damage the cones, but your horns sure wont like having the lows going through them.

A properly set up crossover can get the system as flat as possible before any EQ is applied. I particularly liked the Ashly crossovers for this, because they had the peak/dip knob that was always centered at the crossover point.

I hope this was helpful, it's late here. (or is it early??)

Dave "applying old knowledge" Dermont

Reply posted by Miles Langham on August 20, 2000
I guess it's old knowledge I'm looking for. I'll check out the Soundtech product. I was hoping for something like a detailed schematic for the device blocked out in the study hall article. This is the most affordable so far.

Thanks Dave,

Miles