TLAH Pro for a church sanctuary

[mattsk8]

Very excited to get this build underway, but before I can do that I have a couple questions that hopefully someone here can answer...

First, I read through everything including the plans for the home version. From what I've read, if these aren't going to be corner mounted, then making the cabinets rectangular as opposed to the triangular version is an option; and also the option I will choose as I plan on flying these above the front of the stage. My question is, the triangular baffle dimensions in the plans show the cabinet sides being 6" deep on the bottom and 8" deep on the top; while the rectangular version shows the cabinet sides being 5" deep on top and 3" deep on the bottom. First of all, the mounting depth for the recommended woofer is 3 1/4"; so having the cabinet depth only 3" at the bottom seems shallow in my (very) limited understanding of how and why these work. I just want to clarify that this isn't a typo in the plans and that I should forge ahead w/ building the cabinets this way. Also, if the plans are correct and just for my curiosity's sake, why does changing the shape of the baffle alter the depth of the cabinet so much?

That said, before anyone has visions of someone getting crushed by one of these when it falls apart and lands on them, I have a LOT of experience building cabinets as I used to build high end custom kitchens and cabinets, and I've also built a few pairs of speakers as well (for home use). The instructions say these don't "need to be built like a tank", but do to them being flown these will be.

[Tom Smit]

If you start your woofer line at the top, then the bottom woofer will be not quite at the bottom. Because of the taper, there will be just enough clearance. If you are front mounting the woofers, there will be enough room. Measure it with Sketchup; I did.

[gzc_stageTech]

+1 to what Tom said.
I front mounted mine and while they get close, they don't bottom.

Suggestion for when you hang them. . . aim them down so they point to the first rows of your chairs, otherwise the tight vertical beaming of the tweeters will shoot farther back and the front rows will get mostly mids and low mids. That'll reduce vocal clarity in the front. Everywhere farther back will be sweet though.

Chris

[mattsk8]

If you start your woofer line at the top, then the bottom woofer will be not quite at the bottom. Because of the taper, there will be just enough clearance. If you are front mounting the woofers, there will be enough room. Measure it with Sketchup; I did.

As far as sketchup goes, when I built kitchens, cabinets or speakers, I found it better to use old fashion graph paper and a ruler and pencil them out to scale. It takes more time, but I downloaded Goole Sketchup 8 a couple years ago and didn't see the gain over the pencil and graph paper short of the time; and even saying google sketchup saves time is arguable IMO. Am I missing something?

Also, in the disc of plans under the "read me" section it says, "To view models go to (a link) to download a free program that allows you to view the model, turn the x-ray mode on and off, rotate the model in space, and print different views of it". Is he just telling me to download google sketchup, or is there somewhere I can go to view one of these that's already sketched up? Because if I use that link, all it gives me are different sketchup program options that I can download.

One more question... As far as the xover for these, the plans for the pro version don't make mention of one for the woofers at all. The plans do mention the piezo high-pass filter, but nothing about the woofer's xover. Just from the different speakers I've built, I would assume that changing the cabinet depth and the front baffle so drastically and also changing the speakers would completely change the xovers from the home version's xover. Is this not the case?

[Tom Smit]

Download this, install it, and then go to your plans and click on the icon for the sketchup version of your cab.

[Bill Fitzmaurice]

is there somewhere I can go to view one of these that's already sketched up?

That would be in the folder labeled 'Sketchups'.

[mattsk8]

I downloaded sketchup and now I have the dimensions. Although, I'm still curious why the minor change in the baffle shape justifies the drastic change in cabinet depth.

Can anyone answer the question about the xover? Is there a woofer xover or just a tweeter xover and I would use my Driverack for the woofers?

[mattsk8]

I plan on wiring the woofers series/parallel; I got the 8 ohm Eminence drivers and want to end up w/ a 4 ohm speaker once they're all assembled. I also will wire the piezo tweeters the same way and use the recommended tweeter crossover.

My question is, how do I wire the woofers and tweeters into the input leads on the cabinet? I don't want to bi amp these. Will I still see a 4 ohm load if I wired the tweeter plus to woofer plus, and tweeter minus to woofer minus?

[Tom Smit]

You'll have a filter to install as well, for the tweets. The amp will see the ~4 ohm load of the woofers, and higher up in frequency will see the 4 ohm load of the resistor that you're going to install.

[DJPhatman]

I plan on wiring the woofers series/parallel; I got the 8 ohm Eminence drivers and want to end up w/ a 4 ohm speaker once they're all assembled. I also will wire the piezo tweeters the same way and use the recommended tweeter crossover.

How many 8 Ohm woofers are you using? And why do you want 4 Ohm speakers? If you wire them as 8 Ohm, you can run both from 1 channel of an amp, saving money on amps and power requirements.

My question is, how do I wire the woofers and tweeters into the input leads on the cabinet? I don't want to bi amp these. Will I still see a 4 ohm load if I wired the tweeter plus to woofer plus, and tweeter minus to woofer minus?

You don't. The woofers all get wired together, and the tweeters all get wired together. You build the HP/LP filter shown in the plans, connect your wire from the amp to the ins of the filter, then wire the outs of the filter to their respective woofer or tweeter bank.

Be sure that you wire the woofers as per the plans. If you change your wiring, the filters shown will not be correct.

[mattsk8]

How many 8 Ohm woofers are you using? And why do you want 4 Ohm speakers? If you wire them as 8 Ohm, you can run both from 1 channel of an amp, saving money on amps and power requirements..

We already have the amps, so I chose a 4ohm load to get the most power out of it. I'm using 8 8ohm drivers wired series/parallel.

You don't. The woofers all get wired together, and the tweeters all get wired together. You build the HP/LP filter shown in the plans, connect your wire from the amp to the ins of the filter, then wire the outs of the filter to their respective woofer or tweeter bank.

Be sure that you wire the woofers as per the plans. If you change your wiring, the filters shown will not be correct.

Definitely wiring both the woofers and tweeters per the plans. I know I have to wire the woofers together, plus wire all the tweeters together. What I don't know is how to wire the tweeters to the woofers at the input leads on the cabinets.

The TLAH Pros don't have a woofer filter, only the tweeters do. The HT version does have a woofer filter, but not the Pro version according to the plans.

[Bill Fitzmaurice]

We already have the amps, so I chose a 4ohm load to get the most power out of it.

All you accomplish by going with a 4 ohm load is to reduce the number of cabs you can use should you ever need to expand the system. 'Getting all the power out of my amp' is one of those newbie concerns that we strive to eliminate by education. But you've got to ask.
The only legitimate reason for using a lower impedance load is when the amp you have cannot deliver adequate voltage swing to drive a higher impedance load to full output.

[mattsk8]

You'll have a filter to install as well, for the tweets. The amp will see the ~4 ohm load of the woofers, and higher up in frequency will see the 4 ohm load of the resistor that you're going to install.

When you say "as well", the woofers don't get filtered in the cabinet according to the plans. All they get is wired in series/parallel and the plans show the piezo tweeters wired exactly the same way (except the tweeters do have a filter). My question is, once the woofers are wired in series/parallel, then the tweeters are also wired in series/parallel after the tweeter filter, do I then wire the 2 positives of both the woofer circuit and tweeter circuit to the positive input lead on the cabinet, and additonally do the same to the negative input lead on the cabinet?

All you accomplish by going with a 4 ohm load is to reduce the number of cabs you can use should you ever need to expand the system. 'Getting all the power out of my amp' is one of those newbie concerns that we strive to eliminate by education. But you've got to ask.
The only legitimate reason for using a lower impedance load is when the amp you have cannot deliver adequate voltage swing to drive a higher impedance load to full output.

I never made claims to know or understand how or why pro audio is (seemingly) so much different than home or car audio, which is where my roots are. I assumed the Crown XLS802D power amp the church already has worked similar to every other amp I've dealt w/, where when it's run at 4 ohms it produces more power than when run at 8 ohms; I also assumed this because Crown's website says it's 500 watts at 8 ohms and 800 watts at 4 ohms (I guess I'm reading that wrong?). I thought I would try to maximize the power output. But you're sayingh this is wrong, and there will be no audible gain by doing this; correct? Because these haven't been shipped yet, and it's not too late to change my order.

[Tom Smit]

I meant that the tweeter filter had to be installed in addition to just wiring up the drivers...but you know that.

Yes, the woofer and tweeter wiring should be done as you described.

If you were to set a limiter on the amp so that you limit by db rather than volts (but keep an eye on the volts), you'll find that you won't come near the wattage that your amp provides.

[Jon Barnhardt]

I never made claims to know or understand how or why pro audio is (seemingly) so much different than home or car audio, which is where my roots are. I assumed the Crown XLS802D power amp the church already has worked similar to every other amp I've dealt w/, where when it's run at 4 ohms it produces more power than when run at 8 ohms; I also assumed this because Crown's website says it's 500 watts at 8 ohms and 800 watts at 4 ohms (I guess I'm reading that wrong?). I thought I would try to maximize the power output. But you're sayingh this is wrong, and there will be no audible gain by doing this; correct? Because these haven't been shipped yet, and it's not too late to change my order.

It doesn't make any more power. It's actually less efficient at 4 ohms.

500 watts at 8 ohms is 63.25 volts. That same voltage at 4 ohms is 1000 watts. So if the amp is putting out 800 watts at 4 ohms, it's only delivering 56.57 volts. It's more watts because watts is dependent on voltage and resistance (ohms).

Your speaker don't care about watts. It only knows voltage. The more voltage, the louder it goes (until too much and then black smoke.)

Ohms is nothing more than the amount of resistance the speaker creates for the amp.