Foster Horn Tweeters

[Wigwam Jones]

I took everybody's advice and simply refoamed my Realistic Nova 5 8-inch woofers instead of replacing them. That's all done now and they sound pretty good. However, the tiny, tinny, 2 1/2 inch cone tweeters have got to go. They sound like poop.

I have a set of Foster horn tweeters I picked up cheap; part number 49-1166, marked 74.24 (I believe this means they were made in 1974) Japan Zenith Radio Corp, Chicago, IL. Supposedly came out of a set of Zenith Allegro speakers.

I did a trial fit, and darned if the things don't *almost* fit into the existing tweeter holes! A little work with a rasp ought to get them in there nicely. Plenty of room inside the cabinet for the back of the horns, no problem there.

They actually sound pretty darned good from what I can tell hooking them up outside the box. Bright and clear. The cabinet still has the standard 4.7 uf capacitor crossover in it with some kind of resister - can't quite read the value - in series with the capacitor.

Any thoughts on whether or not this would be a good match? If not, what would you recommend? Anything cheap - and anything that is NOT the stock tweeters, they suck.

Thanks!

 

[MunkeyQ]

You'd need to pad down those Fosters a bit as they're more sensitive than the stock ones - an L-pad and a bit of listening is the best way to do it.

Depending how big the horn size, they should go low enough to meet the 8", but it might be a bit beamy.

Otherwise, practically any semi-decent soft dome will be an upgrade!

 

[Wigwam Jones]

You'd need to pad down those Fosters a bit as they're more sensitive than the stock ones - an L-pad and a bit of listening is the best way to do it.

Depending how big the horn size, they should go low enough to meet the 8", but it might be a bit beamy.

Otherwise, practically any semi-decent soft dome will be an upgrade!

I did notice that the horns are somewhat directional; I tried listening to a couple soft dome tweets also; very nice, creamy and not directional at all, but lacking an 'edge' if you know what I mean. The horns seem to have some sizzle to them; perhaps it's just that they're so directional?

I'm guessing the woofer was designed to be nearly full range; the crossover is simply a resister and a cap to the tweeter, nothing at all on the woofer. Radio Shack catalog of the time describes them as 'long throw 8" woofers' and the cabinet is ported.

I've also got a pair of 1" domes out of a pair of Boston Acoustics that more-or-less fit - same deal, will need a little surgery with a rasp to get 'em in there. They do sound, as I said, creamy and very smooth. I suppose they might be a better choice all-round...eh...dunno.

 

[audiozaz]

I have a pair of Foster horn tweeters taken from Zenith Allegro 1000 cabs. All black plastic, with a hard orange dome (phenolic?). Does that look what you have?

I have not tried to do much with them yet. Let us know if you can make them work for you.

Have fun!

az

 

[absolve2525]

I think I have those Realistics too, or a simiar 2 way with an 8 inch woofer...and a set of Foster tweets from some old Allegros. Mine have a grey plastic-looking diaphragm instead of the orange phenolic. Does anyone know how the 2 versions compare? Id like to find a use for mine too!

 

[audiozaz]

I think I have those Realistics too, or a simiar 2 way with an 8 inch woofer...and a set of Foster tweets from some old Allegros. Mine have a grey plastic-looking diaphragm instead of the orange phenolic. Does anyone know how the 2 versions compare? Id like to find a use for mine too!

I've also seen the grey dome version in pictures on the web. I have no idea what the differences are.

az

 

[Wigwam Jones]

Yes, mine are sort of gray on the 'bullet' portion of the inside of the horn. The look like these:

Hope this link works!

http://bit.ly/e4u1kL

These are the ones I bought recently. The gray inside looks more like oxidation?

 

[Wigwam Jones]

And I have to say that I'm really really tempted to just make the holes the tiny bit larger they need to be in order to sink these tweeters into the speaker and mount them up. Just mounting them outside the cabinet they sound really good to *my* ear, but my ears aren't that great - I do have some hearing loss. I like the sparkle and snap of high end probably a bit more than some. And they are, as reported, 'beamy'. They are not as good with dispersion as the silk dome tweeters I've also been playing with here.

FYI, these Fosters apparently are manufacturer-rated at 8 ohms and cross at 2500. Pretty much a match for the current tweeters, which I believe probably cross at something like 3000 (resister and 4.7 uf cap combination)?

 

[Wigwam Jones]

Here they are refoamed but with the stock tweeters remounted for now:

http://www.flickr.com/photos/wigwam/sets/72157626258222783/

 

[audiozaz]

Yes, mine are sort of gray on the 'bullet' portion of the inside of the horn. The look like these:

Hope this link works!

http://bit.ly/e4u1kL

These are the ones I bought recently. The gray inside looks more like oxidation?

Mine don't have a bullet phase plug thing, but are otherwise very similar. This one seems to have the orange dome under the bullet if I see correctly.

az

 

[gearhound]

I figure with that 4.7uf cap and a single resistor.
You have a 1st order Xover, at a little under 4Khz?
That's assuming that the Foster horns are 8 ohms?

Steve

 

[Wigwam Jones]

I figure with that 4.7uf cap and a single resistor.
You have a 1st order Xover, at a little under 4Khz?
That's assuming that the Foster horns are 8 ohms?

Steve

That's the single-order crossover that came stock in the cabinet. I can't quite read the value on the resister, but it's wired in series with the 4.7 uf cap. So it went with the stock 2 1/2" paper cone tweeter that is in there now. Radio Shack specs say that both drivers are rated at 8 ohms in stock form, so I figured that if you ignore the resister, the crossover is something like 4000 Khz, but with the resister added, I believe that drops it a bit (or am I wrong on that?). In any case, the published spec for the Foster horns says it is rated at 8 ohms and is meant to be crossed over at 2500 Khz. So I am guessing you can cross it higher using the stock (but recapped) crossover and get more or less the same response curve. Anyone comment on that?

Might have to pad it a bit to bring down volume as mentioned by someone previously, due to the higher efficiency of the horn tweeter. Or not - I may just try it and see what it sounds like; my hearing loss might make the difference so I don't want to pad it down. Or I suppose I could reverse the polarity on the horn tweeter; simple trick to make the overlapping portions of the two speakers cancel each other out - if I am reading correctly.

All comments still welcome; I haven't cut anything yet!

 

[gearhound]

Could be that the resistor was in the original circuit, to pad down the original 2 1/2" cone tweeter?

I've seen BIG horn loaded tweeters mated to 15" woofers, in 2-way Magnavox speakers.
Done properly, horns can be crossed over quite low AND sound punchy-n'-dynamic!

Steve

Steve

 

[Wigwam Jones]

Could be that the resistor was in the original circuit, to pad down the original 2 1/2" cone tweeter?

I've seen BIG horn loaded tweeters mated to 15" woofers, in 2-way Magnavox speakers.
Done properly, horns can be crossed over quite low AND sound punchy-n'-dynamic!

Yes, that's what I've been trying to say. The crossover that's in there now is the original crossover for the Realistic Nova 5. A 4.7 uf cap in series with an unknown-value resister. I suppose it probably was there to pad down the original cone tweeter. But in any case, I really don't care for the original tweeter, so it's got to go.

My thought for the horn was to either simply replace the stock cap with a nice same-value poly cap -or- remove the cap and resister and figure out the correct value to cross over the horns - perhaps at 2500, which for a first-order crossover I believe would be something like 8 uf. No resister, see what it sounds like. Add an l-pad if required to bring it down until it's good soundage.

Sorry if I wasn't clear in my initial description.