Blaupunkt Low Volume

[RMBaiada]

I have a mono 1974 Blaupunkt Frankfurt radio that I purchased new and installed in my new 1974 BMW 2002. It has been sitting on the shelf for the last 20 years as I rebuilt the car. After taking the radio off the shelf and hooking up two new 4-ohm speakers in series (Infinity Reference REF-4032cfx) to get the 8-ohm requirement for the radio. The radio works, but the volume is low. It is loud enough sitting in the garage with the engine off, but barely, and the volume will be too low when driving.

 

My question is how to increase the volume? I was told that the 50-year-old capacitors may have dried out and not putting out the full 4 watts of power. I am looking for an inexpensive fix, maybe changing the capacitors, or some other easy fix. I have thought about an inline amplifier, but I can't find an inexpensive 1 channel amp that would work.

 

 

Edited April 27, 2023 by RMBaiada

[David Layton]

The best source on Blaupunkts is Vintageblaue.  Ingo can give you advise.  I sent in a c-series with a non-functioning dial and some other issues and he brought it back to life.  I will be installing it this weekend.

[RMBaiada]

I spoke with Vintageblau, but the rebuild cost was too expensive. I am looking for a possible less expensive alternative.

 

[Einspritz]

Contact "The radioman" in southern California.

 

I've had him refurbish two of mine, though have yet to install them.

[RMBaiada]

Thank you, since I live just north of San Diego, I will call the Radio Man tomorrow.

Edited April 28, 2023 by RMBaiada

[John76]

4 hours ago, RMBaiada said:

I have a mono 1974 Blaupunkt Frankfurt radio

 

Isn't the Blaupunkt Frankfurt a stereo AM/FM/FM stereo?

Do you have a good antenna and adjusted the antenna trimmer (on the radio) correctly?

Do you have a fader control? If so, are the speakers connected correctly?

Did you try other speakers?

Is the power wire (w/fuse) providing a good 12V and the radio has a good ground?

Check the above first...then consider replacing the capacitors if you're handy with a soldering iron.

 

 

[jimk]

How are two 4 ohm speakers connected when the radio requires 8 ohm speakers?

[RMBaiada]

For John, where is the antenna trimmer, how do I adjust it and what capacitors do I need if it comes to that?

 

Also, for JimK, the 4-ohm speakers are connected in series which makes them 8 ohms.

 

Edited April 28, 2023 by RMBaiada

[mgben]

I was looking for @jgerock post about his hidden amp setup. 

In essence leave your radio as a period correct item, then use a bluetooth amp for your music.

He used a nice Kenwood  https://www.crutchfield.com/S-Q7YNb6E16TQ/p_113M1824BT/Kenwood-KAC-M1824BT.html

In my vintage MGB I used a Pyle watersports / 4 wheeler amp setup with a hardwired input (before bluetooth took the market).

For not much money you could try feeding your signal into this or just use the bluetooth

https://www.amazon.com/Pyle-Auto-4-Channel-Marine-Amplifier/dp/B072LDM7N6/ref=sr_1_5?crid=25T9X65P0XG0J&keywords=pyle+amplifier+car+audio&qid=1682697285&sprefix=pyle+amp%2Caps%2C126&sr=8-5

 

[John76]

12 hours ago, RMBaiada said:

where is the antenna trimmer, how do I adjust it and what capacitors do I need

Here's what I have on the back of my Blaupunkt AM radio. 

Tweek the trimmer until best reception.

Not sure what capacitors are in yours. I have a schematic for a Frankfurt AM/FM. Not sure if it will be legible if I scan it but will be glad to mail it to you.

John

 

 

[JohnS]

2 hours ago, mgben said:

I was looking for @jgerock post about his hidden amp setup. 

In essence leave your radio as a period correct item, then use a bluetooth amp for your music.

He used a nice Kenwood  https://www.crutchfield.com/S-Q7YNb6E16TQ/p_113M1824BT/Kenwood-KAC-M1824BT.html

In my vintage MGB I used a Pyle watersports / 4 wheeler amp setup with a hardwired input (before bluetooth took the market).

For not much money you could try feeding your signal into this or just use the bluetooth

https://www.amazon.com/Pyle-Auto-4-Channel-Marine-Amplifier/dp/B072LDM7N6/ref=sr_1_5?crid=25T9X65P0XG0J&keywords=pyle+amplifier+car+audio&qid=1682697285&sprefix=pyle+amp%2Caps%2C126&sr=8-5

 

These little buggers have been discussed here many times.  I think the smaller 50Wx2 one costs about $10, the 100Wx2 about $20.  They work well.  I added the barrel connectors for the speaker outputs.  I have the 100W one connected to some bookshelf speakers in my shop.  It works really good for what it is.  I think they make 4 channel ones also.

 

Edited April 28, 2023 by JohnS

[66Vette]

RM:

 

The problem might be as simple as the Infinity speakers you are using are less efficient than the speakers that were originally used for the Blaupunkt radios.  By todays standards, 4 Watts is not much juice, and todays speakers are designed for much more powerful amplifiers.  Also the Blaupunkt at 4 Watts is maxed out and has pretty high distortion.  It probably puts out more like 2 Watts with acceptable listening quality.

 

You can do a sanity check on the amplifier power output by taking a multimeter and measuring the voltage you are getting across the speaker terminals (with the speakers connected).  If you have a decent multimeter it will be a "true RMS" meter and can measure a random (music) AC waveform for voltage.  Take that voltage and square it, then divide it by your nominal speaker impedance, that will give you the output power (V**2/R = Power).

 

From the data sheet for your speakers, the nominal impedance is 3 Ohms, if you have two in series that is 6 Ohms.  Take the voltage, square it, and divide by 6.  At full volume, you should be approaching the 4 Watt specification.

 

[MikeD]

22 hours ago, David Layton said:

The best source on Blaupunkts is Vintageblaue.  Ingo can give you advise.  I sent in a c-series with a non-functioning dial and some other issues and he brought it back to life.  I will be installing it this weekend.

I used Ingo for my Blaupunkt for my 72 911.  He wasn't cheap but the radio is perfect.

[Mike Self]

Before adjusting the antenna trimmer, adjust your antenna to about 30" in length.  I remember reading when I first acquired a Blaupunkt radio the installation/owners manual indicated that a 30 inch long antenna was optimum for FM reception.  That probably won't solve your lack of volume, but it'll give you a basis for adjusting the trimmer.

 

I tend to agree with those posting about speaker efficiency.  I have a vintage 1959 Stromberg-Carlson console stereo; the amp that puts out a whopping 6 watts per channel, and the 12" speakers in the set will drive you out of the house way before you hit max volume.  If you still have the original speaker that came with your Blaupunkt, try it and see what volume you achieve.

 

mike

[David Layton]

Installed mine that worked fine on Ingos bench. Very low sound at max.  Have 8 ohm speakers attached.