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Old 22nd December 2002, 01:32 AM   #1
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Talking silk purse from 2 sows' ears

I'm looking for advice on a project I'm planning.

Having just completed my new HT setup recently, I have a ton of leftover components. So my thought was to take the drivers from 2 sets of speakers, build new crossovers and cabinets, and have 1 new set of speakers for my "B" system. And this is where I need advice.

1 set of speakers has: 10" woofer, 4" mid, and 2.5" horn tweeter, xover points of 2000 Hz & 3600 Hz. A no-name brand from 1988.

Other set of speakers has: 6.5" woofer, 2.5" cone tweeter, single 1.2 uF cap for a xover. Pioneer from 2000.

So, can I take this mix and make it better? A new 3- or 4-way design? Scrap the old set and just use the Pioneers? Remember, its for the "B" system. Please, no jokes about kindling
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Old 22nd December 2002, 02:01 AM   #2
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Offhand, my initial inclination is to take the 4 inch out of the no-name 3 way and substitue an enclosed 6.5 inch Pioneer crossing over at 200 Hz and 2500 Hz or so.

However, I fear the crossover components, especially at the 200 Hz point, might be too expensive for a "throw it together and see what happens" type project.

Perhaps, a sealed design can be used on the 6.5" where the low frequency rolloff can be used for the crossover. Then, you might escape with just an inductor for the 10".

Then I would take the best tweeter of the two and cross it over to the 6.5". Or see if I could get a decent tweeter cheap. Or use a piezo-maybe something like a KSN 1165A.

Check to see is the tweeter horn is piezo. If so, which model?

The KSN 1016A also has good response for a piezo from 3000 Hz up.

Check out the responses for the KSN 1016 and KSN 1165A at the following thread:
need driver finding help

Be on the lookout for good prices on dynamic tweeters as well. They happen.

Well, just a bunch of quick suggestions.
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Old 22nd December 2002, 04:40 AM   #3
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Default Re: silk purse from 2 sows' ears

Quote:
Originally posted by leadbelly
1 set of speakers has: 10" woofer, 4" mid, and 2.5" horn tweeter, xover points of 2000 Hz & 3600 Hz. A no-name brand from 1988.
The 10" will be extended range to go up as high as it does, the mid is primarily there for decoration, but some of the horns in this ilk can be quite good -- Foster made a 2.5" horn that is quite excellent. Can you tell us more about the drivers?


Quote:
Other set of speakers has: 6.5" woofer, 2.5" cone tweeter, single 1.2 uF cap for a xover. Pioneer from 2000.
1.2 uF cap? Even with a 16 ohm tweeter this is essentially a full-range system with a helper tweeter.

I would tend towards what kelticwizad suggested, Take the 6.5 and put it in a sealed or aperiodic enclosure. Use the better of the 2 Ts with a single cap -- slowly increas ethe cap size till the T starts to intrude, then back it off.

Getting the 10" to fit in without some trickery (like bi-amping) could be tricky. Your best bet might be to side or rear mount it, and just do a 1st order XO at the bafflestep frequency -- because it is extended range it may well integrate.

The non-front mounting will help keep the higher frequencies from interferring with the FR, and XO at the baffle-step will make this a variation on a 2.5 way.

Now this will only work if the 6" & the 10 are approx the same efficiency, otherwise time to scare up a 2nd amp and use a PLLXO.

And then if you are getting to that point, the 2 10s in a single push-push sub will be more versatile (and you could just use the Pioneers in there existing state -- with teaks of course).

dave
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Old 22nd December 2002, 04:57 AM   #4
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Default Re: silk purse from 2 sows' ears

Quote:
Originally posted by leadbelly
Please, no jokes about kindling
Heck, the cabs make great fuel for a big bonefire. Just lit up the fire to consume all the excess cabinets from my hifi recycling biz collected since May 1 -- it will probably still be burning Monday nite

dave
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Old 22nd December 2002, 02:52 PM   #5
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Thanks for the suggestions.

I wish I could say more about the drivers, but they don't have brand markings.

The horn tweeter is a piezo I guess. All it says is 5DR51526, TAIWAN, PT-8651. Magnet has a good heft to it.

The cone tweeter says 275749-A, 4 ohm, INDONESIA, IT-1020629.

The 4" midrange looks like a piece of fluff.

The 6.5" woofer looks the highest quality of the lot, good heft to the magnet. It says 268251-A, 6 ohm, INDONESIA, IT-1020703.

The 10" woofer says PL7D2, 4DR51688.
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Old 22nd December 2002, 04:49 PM   #6
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Quote:
Originally posted by leadbelly
Thanks for the suggestions.


The horn tweeter is a piezo I guess. All it says is 5DR51526, TAIWAN, PT-8651. Magnet has a good heft to it.
If it has a magnet, it is not a piezo. Piezos use a thin wafer or piece of film to create back-and-forth movement-no magnet or voice coil is involved.

Indonesia? I shouldn't be surprised. Most here in the US don't know it, but Indonesia is just behind the USA in population. Not surprising to see speakers coming out of there.
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Old 23rd December 2002, 12:55 AM   #7
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Quote:
Originally posted by leadbelly
I wish I could say more about the drivers, but they don't have brand markings.
pictures?

Quote:
The horn tweeter is a piezo I guess. All it says is 5DR51526, TAIWAN, PT-8651. Magnet has a good heft to it.
That will likely mean it is not one of the cool alnico ones.

Quote:
The cone tweeter says 275749-A, 4 ohm, INDONESIA, IT-1020629.
4 ohms with a 1.2 uF cap is going to be a nominal 30 kHz XO. It [robably doesn't even go up that high].

Quote:
The 4" midrange looks like a piece of fluff.
as expected. sealed back no doubt.

Quote:
The 6.5" woofer looks the highest quality of the lot, good heft to the magnet. It says 268251-A, 6 ohm, INDONESIA, IT-1020703.
Given the cap size on the tweeter this is probably better considered a Full Range -- the ideal candidate for midrange duty.

Quote:
The 10" woofer says PL7D2, 4DR51688.
My 1st guess to the part numbers is that they are Panasonic OEM units.

dave
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Old 23rd December 2002, 02:39 AM   #8
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Some thoughts on that 1.2 uF capacitor.

A 6 dB/octave crossover generally has a capacitor that has 8 ohms, (or 4 ohms in a 4 ohm system) at the desired crossover frequency.

At 3400 Hz, that 1.2 uF capacitor has 39 ohms. At 2000 Hz, it has an ohmage of 66 ohms.

It would seem to be ridiculous-but consider. Magnetic speakers, even tweeters, all have a resonance point where the ohm rating goes way, way up. 39 or 66 ohms ohms is not an uncommon rating for a 4 ohm or 8 ohm tweeter at resonance.

At that resonance, the output of the tweeter might be at the midpoint, above it or below it. Frequently, the tweeter's output is just below the midpoint at resonance.

If the resonance of the tweeter is 2000 Hz, 3400 Hz or so, then any crossover capacitor will be required to have a very high ohmage at the crossover frequency to have an effect on the tweeter. Much below the frequency of resonance, the speaker returns to 8 ohms or 4 ohms, and the capacitor then acts as a very high slope crossover element indeed-much higher than 6 dB/octave.

So maybe they crossed over at the tweeter's resonance point, that is why the capacitor is so small. The capacitor needs to be small to get that high ohms rating.

I have never done a crossover like this, by the way. I have never run a tweeter all the way down to it's resonance point. But if you are going to run the tweeter down to it's resonance, I would think that is what you would have to do. Very high ohmage, therefore very small capacitor.

Strictly speaking, running a tweeter all the way down to it's resonance is not the best idea, though I have never heard that it cannot be done. However, we all know that this was not the most expensive speaker system in the world, so maybe that is what they did.

Just a guess.
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Old 23rd December 2002, 06:54 AM   #9
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I just had a session listening to the 2-way speakers, comparing them to my "A" set, and listening to each of the 5 drivers by itself.

I doubt my original idea would work, as there is a pronounced difference in sensitivity between the 2 sets of drivers.

I think the 1.2 uF cap is a joke, as the speaker as a whole sounds quite bassy. Yet listening to just the tweeter surprised me, as it seems very decent. The capacitor is obviously choking it off almost entirely. A better crossover would improve the speaker immensely.

So my thinking is now to just use the 2-ways as satellites and use the 10" woofers as subwoofers, using 3-way passive crossovers.

Make sense? What should I be looking at for crossover design?
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Old 23rd December 2002, 08:05 AM   #10
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Quote:
Originally posted by leadbelly
I think the 1.2 uF cap is a joke, as the speaker as a whole sounds quite bassy. Yet listening to just the tweeter surprised me, as it seems very decent. The capacitor is obviously choking it off almost entirely. A better crossover would improve the speaker immensely.
Keep adding capacitance bit by bit until the tweeter starts getting to be too much, then back it off. I suspect it is quite robust and you can probably go as high as 12 uF or more -- 12 would give a nominal XO at 3 kHz (and is probably a little low)

[QUOTE]So my thinking is now to just use the 2-ways as satellites and use the 10" woofers as subwoofers, using 3-way passive crossovers.

Quote:
Make sense? What should I be looking at for crossover design?
Getting a passive XO to work decently for a sub is hard (and the inductors & caps are huge -- and expensive). Active would be better & might actually be done for less $$$ if you can scrounge up an inexpensive amp.

dave
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