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 Post subject: Vintage Top Line Magnavox Extension Speaker Xover Help
PostPosted: Feb Sun 17, 2019 1:26 am 
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Location: Central PA 16801
hello folks,

today I acquired a top line Magnavox extension speaker from the early 50s. it has the 15 inch bass driver with the big black bell. the horn is the larger and deeper horn than the normal ones found in the regular Magnavox speakers. it is beautiful and made with solid plywood all around except for the back pegboard. it definitely is a class act for what I believe would be a high-end magnavox system.

this top line unit bi-amped the woofer and tweeter. both drivers went straight to the amplifier, the woof and tweet had their "own amplified" section, hence there was NO crossover in the cabinet.

the woofer will run wide-open as magnavox did it, but I want to cross the tweeter with a 2nd high-pass filter around 2.5k.

since most crossovers and the ones I have here are designed for 8 ohm speakers, here is my question.

if I have an 8 ohm high pass crossover that crosses over at 5k and if I hook it up to the 16 ohm tweeter, (measures 11 ohm dcr as all of those Magnavox horns did), the "8 ohm crossover point" that is loaded with a 16 ohm driver will now cross over (half) at 2.5k, correct ?

in other words: If you use a 16 ohm high frequency driver with an 8 ohm crossover, the crossover point will halve. (I am correct on this, correct ?)

-or can i:

place an 8 ohm non inductive resistor across the 16 ohm tweeter to make it an "8 ohm driver" for the crossover to see and use an 8 ohm 2.5k crossover ? (3db of attenuation will be nothing on this screaming horn, I plan on padding it down after all frequencies are said and done.)

bottom line questions:

1. should I use a crossover (that I have here) that crosses over at 5k for an 8 ohm load--which will cross my 16 ohm horn at 2.5k ? 16 ohm horn will be crossed at 2.5k.

or

2. should I make the 16 ohm horn an 8 ohm speaker by paralleling an 8 ohm resistor across the voice coil to fake out an 8 ohm crossover that crosses at 2.5k ? "8 ohm" horn will be crossed at 2.5k

or

3. it does not matter.

i ask, which one and why ? (I say use the 5k 8-ohm crossover with the 16 ohm horn to cross the horn to my wanted 2.5k, all due to the damping factor)

we are not designing a 4 way 4th order professional system here. all I want to do is cross the horn somewhere around 2.5k, L-pad it down after the xover is used, and use this beautiful speaker with some of my fantastic hifi amps.

i plan to use a linkwitz-riley crossover design so there is no bump at the crossover point and enhance an already screaming horn.

thanks,

steve

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 Post subject: Re: Vintage Top Line Magnavox Extension Speaker Xover Help
PostPosted: Feb Mon 18, 2019 2:22 am 
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Joined: May Sun 13, 2012 8:12 pm
Posts: 12588
Location: Central PA 16801
ok then...

I guess I will just design a crossover with fresh parts for a 16 ohm driver...

steve

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