I have a pair of Foster tweeters from a pair of Zenith Allegro speakers. Mine are the black plastic housing with the silvery domes and square mounting flange.
Does anyone know the SPL of them?
I used them in one of my early speaker builds and used variable l-pads. I'm wanting to go with fixed l-pads instead so there's less I have to worry about adjusting in my stereo.
Does anyone know the SPL of them?
I used them in one of my early speaker builds and used variable l-pads. I'm wanting to go with fixed l-pads instead so there's less I have to worry about adjusting in my stereo.
Those look very like the Foster horn tweeters used in the Wharfedale E (for high efficiency) range of speakers, and which were 98 dB.
Can you measure the DC resistance for comparison purposes.?
Can you measure the DC resistance for comparison purposes.?
I'd have to remove the back of one of the speakers some time this week.
Also as I recall mine were the version with the crossover cap and coil on a board that slid on the speaker terminals.
Now would the DC resistance of them be the same as the DC resistance of the phenolic dome version of that tweeter? If so I can get to one of those easy I think and can measure its resistance.
Now were different variations of those square black tweeters used only in different models of Allegro speaker or could the same model Allegro have a different variation of tweeter depending on when the speaker was made or was it whatever was in stock that Zenith could get at the time?
Also as I recall mine were the version with the crossover cap and coil on a board that slid on the speaker terminals.
Now would the DC resistance of them be the same as the DC resistance of the phenolic dome version of that tweeter? If so I can get to one of those easy I think and can measure its resistance.
Now were different variations of those square black tweeters used only in different models of Allegro speaker or could the same model Allegro have a different variation of tweeter depending on when the speaker was made or was it whatever was in stock that Zenith could get at the time?
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The Wharfedale E50 Foster horn tweeter had the following specs: 8 ohm nominal (6.9 ohm DCR), 98db/2.83V/m, 2.7kHz resonance.
This type of tweeter is characterised by low power handling, made up for by a high crossover frequency and high sensitivity.
I think it is sensible in your case to accept 98 dB as a working hypothesis.
If you still have a variable L-pad you could use it to set the required degree of attenuation then measure the values of the parallel and series resistances.
Measuring across terminals 1 & 2 will yield the parallel resistor value.
Measuring across terminals 3 & 2 will yield the series resistor value.
This type of tweeter is characterised by low power handling, made up for by a high crossover frequency and high sensitivity.
I think it is sensible in your case to accept 98 dB as a working hypothesis.
If you still have a variable L-pad you could use it to set the required degree of attenuation then measure the values of the parallel and series resistances.
Measuring across terminals 1 & 2 will yield the parallel resistor value.
Measuring across terminals 3 & 2 will yield the series resistor value.
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I still have a bunch of these kicking around, osrtly the dead ones.
The hoens varied depending on when they were made. There was a short version and a long version. Sometimes a shoert on would come with aa styrofoam spacer that made the short one look like a long one.
I have a wack of impedance plots, but no sensitivity measures. I doubt they are as efficient as earlier suggested.
Radio Shack sold a version of this tweeter (i may have a pair) and it popped up elsewhere as well.
dave
The hoens varied depending on when they were made. There was a short version and a long version. Sometimes a shoert on would come with aa styrofoam spacer that made the short one look like a long one.
I have a wack of impedance plots, but no sensitivity measures. I doubt they are as efficient as earlier suggested.
Radio Shack sold a version of this tweeter (i may have a pair) and it popped up elsewhere as well.
dave
As were all the Allegro XOs i saw.Galu, all the ones that passed thru here (many) were nominal 8Ω.
dave
The needed attenuation is 11dB and the calculated resistor values are series 5.74 ohms (4.7 ohm and 1 ohm in series is close enough) and parallel 3.13 ohms. How far can I deviate from the .13 ohms before the effect to the crossover and output is noticeable?
I did think about setting the variable l-pad by ear then measuring the resistance before posting here, however I want the tweeter attenuation to be set right and not by ear.
I did think about setting the variable l-pad by ear then measuring the resistance before posting here, however I want the tweeter attenuation to be set right and not by ear.
I don't think that is possible for it "to be set right" unless you know the exact sensitivity figure for the particular tweeter in question.
It really does come down to setting by ear or, better still, by measurement (if you have the facility to undertake it).
I wouldn't overthink this - you really can't avoid being in tweaking territory.
Radial Horn Tweeter - Stock number 40-1278 in their 1977 catalogue, but no sensitivity figure given.
I agree, sensitivity figures can be optimistic.
I suppose it depends on the frequency range over which measurements are made on the tweeter in order to establish an average figure.
I have the Fosters and the actual Zenith speakers with them and IIRC, they were 96 dB. They also only extend to a little over 16k.
Edit: I am wrong, the speakers are the 3000 which have a round tweeter.
Edit: I am wrong, the speakers are the 3000 which have a round tweeter.
1990 catalog
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Dunno, I've only used the 1228 that with a bit of tweaking impressed a lot of folks way back when in small 2way and a few 3way TV/house party speakers.