: Trying a different approach to speaker upgrade  ( 265 )

Hydrolastic

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Trying a different approach to speaker upgrade
« : February 15, 2021, 10:59:01 PM »
Hello all,  After trying to get a speaker/horn combo to work in the 2st208 with horrible results. I though that i could forget the horn and just replace the woofer. The 2st208 used the 2 oz magnet speakers @ 4 ohms i wonder if i could swap the 35 oz @4 ohms speaker would it work correctly? Do the stronger magnet speakers need different crossover capacitor values> thank you Aaron
 https://flic.kr/p/2kC6NWK
 https://flic.kr/p/2kC6NXw
 

TJ

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Trying a different approach to speaker upgrade
« #1 : February 16, 2021, 11:01:58 AM »
You can use any size magnet speaker. The magnets have no effect on the rated input impedance.

The bigger the magnet, the "better" the efficiency of the speaker.  There is some debate that once you reach a certain magnet size on speakers, that going any bigger on the magnet has little effect and is more for advertising, especially on AlNiCo magnet speakers.  Ceramic magnet speakers need to have bigger magnets than AlNiCo speakers as they tend to be less efficient.

I replaced the 7oz speakers in my Continental with 35oz speakers from an Imperial. Zero issues.
My Consoles:
1962 Motorola SK112CW-FM, All original tubes
1958 Magnavox Continental - DIY Concert Grand!
1957 Magnavox Brittany - Amp 148 Magic!

Hydrolastic

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Trying a different approach to speaker upgrade
« #2 : February 16, 2021, 04:59:33 PM »
Right on! i will put the 35 oz CG speakers right in and see how it works. Aaron
 

Hydrolastic

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« #3 : February 17, 2021, 05:14:23 PM »
Hello  again, So put the CG speakers in, They are not a matched set as the CG uses a combination of speakers.  I would really like a good explanation as to why but thats a different subject.
 The bass does seem improved like more thump. But i have come to see that there is a thing that happens at about half volume the quality of sound goes away as it gets louder. Its not just the speakers either even though it is noticeably improved  I am now convinced that you need the bigger amp to be able to drive the bass speakers harder. Which makes sense as the systems with bigger amps get bigger heavier magnets. I plan on keeping the CG speakers in the 2st208 with the AMP 185 but this console needs some new mid range speakers as the 60 year old 5 x 7's are shot and the smaller 4" tweeters the cones are rock hard   . I still have some items to figure out like which amp to work on next.  Aaron   

TC Chris

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« #4 : February 17, 2021, 08:05:24 PM »
Hello  again, So put the CG speakers in, They are not a matched set as the CG uses a combination of speakers.  I would really like a good explanation as to why but thats a different subject.
 The bass does seem improved like more thump. But i have come to see that there is a thing that happens at about half volume the quality of sound goes away as it gets louder. Its not just the speakers either even though it is noticeably improved  I am now convinced that you need the bigger amp to be able to drive the bass speakers harder. Which makes sense as the systems with bigger amps get bigger heavier magnets. I plan on keeping the CG speakers in the 2st208 with the AMP 185 but this console needs some new mid range speakers as the 60 year old 5 x 7's are shot and the smaller 4" tweeters the cones are rock hard   . I still have some items to figure out like which amp to work on next.  Aaron

What I've read about the mis-matched speakers is that the intent was to have different resonant frequencies to smooth out the overall response.  The cone tweeters are supposed to have those hard cones. They all do.  I think it was a mechanical way of limiting their response to higher frequencies only. Don't pitch 'em.  They work for the highs.  Or if you really want to replace them, put the old ones in a box and send them to me!

There's a lot of art in getting things to sound right.  Magnavox's advertising always talked about how they matched up all the components so the ultimate sound output was accurate.  There's probably some truth in that.  They could compensate for nonlinearity in one component  by fiddling with the response of another one.  You may have to play around with crossover components are maybe even the amplifier to get everything to sound right to you.

Chris Campbell

Hydrolastic

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Trying a different approach to speaker upgrade
« #5 : February 17, 2021, 09:40:26 PM »
Hello Chris, First question. If magnavox was making the sides of the stereo slightly mismatched why did they not put a balance knob on the console? In other words make the sound perfectly balanced from the factory then put a bit of imbalance in. Not saying it didn't work it just seems like a funny way to do something.  Thanks for the info on the tweeters  i will keep trying to work with them. To clarify i turned down the bass knob and the volume mid range is down on one side. Aaron 

TC Chris

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Trying a different approach to speaker upgrade
« #6 : February 17, 2021, 10:33:45 PM »
Hello Chris, First question. If magnavox was making the sides of the stereo slightly mismatched why did they not put a balance knob on the console? In other words make the sound perfectly balanced from the factory then put a bit of imbalance in. Not saying it didn't work it just seems like a funny way to do something.  Thanks for the info on the tweeters  i will keep trying to work with them. To clarify i turned down the bass knob and the volume mid range is down on one side. Aaron

The mis-matched speakers they installed had the same efficiency--the same audio output for a given electrical input.  They just differed in resonant frequency. And besides, bass sounds are largely non-directional, which is why Motorola used their 3-channel system with one combined bass channel.  And Maggie does have a balance control.  One of the knobs has a hollow shaft that you use a screwdriver in after pulling the knob off--at least if you have the tuner/preamp with that feature.  Somebody else can fill us in on what models have that.

Chris Campbell

Bill

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« #7 : February 18, 2021, 08:01:44 AM »
As far as balance controls, the Concert Grand and the big Imperial have the hollow shaft.  My Symphony has the balance control in the amp.  I'm not sure about the Little Imperial but I'm guessing because it has the better tuner it too has the hollow shaft.  As for the rest of the Magnavox line I'm not sure.  Check the top side of your amp to see if there is a balance control.  If not, you probably have a hollow shaft which is usually under the bass or treble control.  My Imperial it's the treble.

Speakers!  If you were to take the covers off your speaker compartments on your Imperial you will find the use of two different magnets as well.  At least that's the way mine is, so I assume yours will be the same.  Also, like Chris said, you may have bad crossover caps. If I were you, I would just replace them.  You might be surprised at the difference in sound. 

Good luck Aaron,
Bill



electra225

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Trying a different approach to speaker upgrade
« #8 : February 19, 2021, 08:04:44 PM »
My Concert Grand does not have a hollow shaft.  It has a phono balance control, which is all you get.  However, there is a tutorial in "downloads" that tells how to set the balance on any Magnavox instrument.  The 88 series amp has the balance control in the bass control shaft.  The 93 series has a balance control on the amp chassis.  The 64 series tuner in my Imperial has the balance control in the hollow shaft of the bass control, but it is just a phono balance control, ala the Concert Grand.  We must remember that these big Magnavox instruments were designed and built to be the ultimate record player.  They did not give two hoots about radio performance.  As long as it worked, good enough.  All the instructions on balance says to use a mono record on the changer, then put an analog meter on each speaker, then adjust the control until the signal to the speakers is the same.  You need a Snap-On screwdriver, made to adjust Bosch K-Jetronic fuel injection to be able to reach the balance control in the Imperial tuner.   ;)


Magnavox matched speakers to components to cabinet.  Trying to alter any of the combination typically yields less-than-satisfactory results.  Your best bet is to troubleshoot and repair the original components.  Good luck.
I don't need Google.  My wife says she knows everything.

Bill

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Trying a different approach to speaker upgrade
« #9 : February 21, 2021, 09:23:43 AM »
Thanks Greg, I figured if a Imperial had the hollow shaft so would the CG.  I apologize for guessing. I need to stop doing that, it usually gets me in trouble.

Bill