Original Speakers, 914-6 Options

[DennisV]

What were the brand and model of original speakers? I would have guessed Blaupunkt.

There are Zenith in the pods of our car ad they appear to be pretty old. They have odd connectors. Assuming these are original speakers, I need to figure out wiring from Blaupunkt Frankfurt head unit. If not, then I'll get something more modern and work backwards from there.

Thanks.

P.S. This probably should have gone in the originality forum. My mistake.

[DennisV]

Something we didn't not touch on, but I think is important, is impedance.

If I understand correctly from chatting with Ingo Prangenberg and reading his site vintageblau.com, the early 70s radios are meant to have 8 ohm speakers. Using 4 ohm speakers will potentially distort and / or damage the radio amp and speakers. Unless you wire the 4 ohm speakers in series, which I think is unusual for car radios.

The Blaupunkt Frankfurt radio we have with sticker date code B = 1970/71 is mono. It appears stock speaker cable is for wiring in parallel.

The Zenith speakers I found in the car measure ~6 Ohms. My understanding is voltmeter will measure slightly less than the rating, so these are probably 8 Ohm spec speakers.

Please correct any parts I've gotten wrong. I'm learning as I go... (IMG:style_emoticons/default/aktion035.gif)

[Superhawk996]

Please correct any parts I've gotten wrong. I'm learning as I go... (IMG:style_emoticons/default/aktion035.gif)

Like most bull (IMG:style_emoticons/default/stromberg.gif) you find on the internet you have to question it all and try to look for verification of source info. (Including mine (IMG:style_emoticons/default/laugh.gif) )

As a general principle - solid state amplifiers are not particularly sensitive to speaker impedance but they also don’t like to be overloaded by extremely low impedance (let’s call that 2 ohms or less)

You are correct that higher impedance is safer for the amplifier. You’ll just get less volume and some other changes (like circuit damping) that come along for the ride that are outside the discussion here.

The site you pointed to is a little disappointing. No source material backing up his claims. There is plenty of source material contradicting his claim of 8 ohms but perhaps he’s focused on some specific models. His claim that “Speaker wattage should be kept relatively low. . .” is odd. Speaker power rating has zero effect on impedance and this is just a weird recommendation. I agree there is no point putting a 50 watt rated speaker on a 5 watt radio but it isn’t going to harm the radio or its speaker amplifier circuit.

Here is what I could quickly find for a Frankfurt owners manual and schematic. WARNING: all electronics are model specific. I have no idea what exact model you have.

[DennisV]

Here is what I could quickly find for a Frankfurt owners manual and schematic. WARNING: all electronics are model specific. I have no idea what exact model you have.

The manual you posted is for a stereo unit, which would seem to suggest it is a later model than what I have.

Thanks to Radiomuseum.org I finally found a manual for our specific model 1970 Frankfurt US 7639670. It seems to indicate 5,8 ohm.



FWIW - There are a lot of radio manuals on The Samba. I have seen a couple that spec 5 or 6 Ohm. I haven't seen an 8 myself.

[Superhawk996]

Here is what I could quickly find for a Frankfurt owners manual and schematic. WARNING: all electronics are model specific. I have no idea what exact model you have.

The manual you posted is for a stereo unit, which would seem to suggest it is a later model than what I have.

Thanks to Radiomuseum.org I finally found a manual for our specific model 1970 Frankfurt US 7639670. It seems to indicate 5,8 ohm.



FWIW - There are a lot of radio manuals on The Samba. I have seen a couple that spec 5 or 6 Ohm. I haven't seen an 8 myself.

(IMG:style_emoticons/default/smilie_pokal.gif) there you go!! I like radiomuseum.org a lot - great resource! I’ve used them in the past for vintage tube radio info!