Budget PA Speaker Upgrade Questions - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 8 Old 02-13-2012, 08:25 AM - Thread Starter
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I just purchased some used Kustom KPC10M speakers for casual use at our family BBQ's, get togethers, etc. They will be used in lieu of larger PA speakers I have for ease of setup (and back strain).

I am upgrading the original 60 watt drivers with these from PE, now on order. Questions:

1. I noticed that all three PA speaker models I have had the pleasure of disassembling (these Kustom, Sonic 15" 3 way, Yamaha BR-15) all run the woofers full range. Is this typical in PA speakers? It seems the HF drivers are typically protected by a crossover but the LF drivers run unrestricted.

2. Do the same "rules of the road" apply for PA speakers as subs (e.g., box tuning, use an hpf at box tuning if ported, etc.)? Do I need to worry about the new drivers unloading and bottoming out? The cabinets are "ported".....two small ports (by memory) about 1.5"x3" deep. The old Kustom drivers looked to be very light duty compared to the PE drivers on order, and have a much higher Fs. Should I try to calculate the box tuning and adjust it to the new (lower) drivers' capabilities? If need be, I can convert them to sealed boxes, but would probably lose a lot of output. I know PA drivers are built for punishment to some degree........

3. The old HF horns seem to work fine, and they have a single order crossover (cap). If I find better hf horns to replace the existing ones as bolt-in, do I need to be critical about crossover frequency, or just protecting the driver? Can you mix/match drivers at will with good results?

These never will be for critical listening, and I know there is much more "forgiven" for PA systems, I just want to get the most I can out of the enclosures in hand, budget in mind.....I will be installing lining and stuffing as well.

Thanks......
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post #2 of 8 Old 02-13-2012, 09:53 AM
 
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One should almost never run the woofer full range or use a first order HP filter. That's only done with cheap poorly designed cabs. That probably means that these weren't worth putting new drivers in anyway, good money after bad. Since you have drivers ordered fix the cab and crossover as best as you can, though starting off from scratch building cabs appropriate for the woofers is probably the better option.
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post #3 of 8 Old 02-13-2012, 03:37 PM - Thread Starter
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Quote:
Originally Posted by Bill Fitzmaurice View Post

One should almost never run the woofer full range or use a first order HP filter. That's only done with cheap poorly designed cabs. That probably means that these weren't worth putting new drivers in anyway, good money after bad. Since you have drivers ordered fix the cab and crossover as best as you can, though starting off from scratch building cabs appropriate for the woofers is probably the better option.

Thanks Bill. I knew these were not "quality" cabs when I bought them, but they fit my needs. I don't want to go too "deep" into the speaker design thing, but would welcome a "down and dirty" design using these woofers and some budget HF horns. Building a simple cabinet is do-able.

I would certainly never even ask this for home speakers.....but would an "off the shelf" two-way second order crossover be better than nothing?
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post #4 of 8 Old 02-13-2012, 03:52 PM
 
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Originally Posted by zhillsguy View Post

but would an "off the shelf" two-way second order crossover be better than nothing?

You'll find any pro-sound crossover worth using is a 2nd/3rd order, and not cheap. You're better off rolling your own.
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post #5 of 8 Old 02-13-2012, 06:54 PM
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The reason there is no low pass and only a simple high pass is that these cabinets are built for a budget. At their intended price point-every dollar adds up.

I would start with sticking in the woofers you ordered and listen. See if they sound OK for your intended purpose. And possibly stop there.

If they don't-then think about working on the crossover (among other things).

The cabinet is probably pretty cheap-as well as the horn-but who knows.

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post #6 of 8 Old 02-13-2012, 08:48 PM
 
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The cabinet is probably pretty cheap-as well as the horn-but who knows.

If it's the cab that the link leads to it's really cheap, as in particle board and a five dollar woofer. And it appears to have a piezo tweeter, which begs the question why it has a filter cap.
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post #7 of 8 Old 02-13-2012, 09:04 PM - Thread Starter
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Quote:
Originally Posted by Bill Fitzmaurice View Post

If it's the cab that the link leads to it's really cheap, as in particle board and a five dollar woofer. And it appears to have a piezo tweeter, which begs the question why it has a filter cap.

Yes, it is a cheap cabinet, I knew that going in....I pulled out the (ahem) horn tonight, it looks like a no-name piezo. I am mulling over options now, and may end up building a couple of budget cabinets (with home-spun two-way second order crossovers, no less) soon, whether any of my original questions get answered or not. The more I think about it, could be a fun project, with my limited woodworking skills.....I have only built subs until now. I paid someone else to build my AutoTuba .
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post #8 of 8 Old 02-14-2012, 06:11 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

If it's the cab that the link leads to it's really cheap, as in particle board and a five dollar woofer. And it appears to have a piezo tweeter, which begs the question why it has a filter cap.

There is a kinda well know loudspeaker manufacturer (in my area anyway) that used to use piezo's in quite a few cabinets. They put a 4uf cap in series with the piezo.

I guess "because that is what you put on a "horn". But they did not under stand how a piezo worked/what the impedance was as so forth.

As far as the piezo was concerned-the cap was a piece of wire. So all they did was lose money by putting it in. And they just "let 'er fly" by just hanging the cap off of one of the terminals. I fixed many of them by simply hooking the wire back up to the piezo-and getting rid of the cap-whose weight caused the problem in the first place.

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