Vintage car radio to amp

[MGBGT1966]

Hi, I have a MGB GT from the 1960s with a vintage mono radio fitted (I think it is a blaupunkt Hldesheim). The radio is connected to a 6X4 inch speaker mounted below the dashboard in the dedicated space in the middle. The sound is surprisingly loud, but the character is rather harsh and lack power/base. Now I know these old time radios are not audiophile, but I am hoping to find a way to improve the sound somewhat. I tested the speaker in another setting and it seems much of the harshness comes from the speaker so I have decided to change it.

I was hoping to receive some tips, experiences and recommendations on speakers and possibly amps too. I am particularly curious on how to best connect an amp to the radio. I would be using the speaker output from the radio so I suspect a low power converter would be needed? My concern is if the radio will be able to handle this? From what I understand, the radio should have about 4 watt max output and recommended to operate a speaker at 4 ohms.

I found this used 6X9 speaker with an integrated amp from a chrysler that seems I might be able to squeeze in to the dashboard: http://www.2040-parts.com/infinity-6...73ab--i604115/ But the question is, would I be able to hook it up to the MG? And if so, could I connect it straight to the speakers, or would I need a converter? Any thoughts on this would be appreciated. Tips on other speakers/settings also welcome.

Thanks,
Gunnar

[Electronpusher0]

First question, is the MG negative or positive earth?

Peter

[MGBGT1966]

Hi, thanks Peter. I forgot to mention that. It has been converted to negative earth.

['LIVEWIRE?']

It's quite possible that the amplified speaker in your link has a line level input, in which case it cannot be connected to the speaker terminals on your Hildesheim Radio. I'd be inclined to ask the seller for more information about that speaker first.

[tri-comp]

It is necessary to know exactly WHAT Hildesheim radio you have.
Hildesheim alone says nothing about what the radio contains or how it's built.
Some are made from the factory with an output to be used with an external amplifier, others not.
Look at the label on the side of your radio and report the number starting with 7, followed by at least 2 groups of numbers each with 3 digits.
That should pinpoint the version and open a way to find the correct schematic.
I've attached a file with 2 schematics for Hildesheim to show how big a difference there can be between two Blaupunkt radioes with the same name.
One radio (upper schematic) is made for connection to external amplifier, the other not.
The lower schematic shows a Hildesheim suitable for both 6 and 12V supply with negative or positive chassis.

[snowman_al]

Hi Gunnar,
If you believe the speaker is the problem, why not start by testing another, better, 4 ohm speaker in the car first?

Old AM radios do not sound anything like the FM and DAB you might be used to today. If the sound quality is poor to start with, adding another amplifier will not improve it.

Alan

[Heatercathodeshort]

I have exactly the same problem with the Radiomobile 1070 fitted in my 1968 MGBGT.
The original speaker baffle, if you could call it that is more decorative than functional. The 7X4 speaker is designed to be sensitive rather than give a good bass response. It is a typical 'television' type of the period.
The radio performs well with plenty of volume and sounds good when connected to a decent speaker /enclosure but no bass with the car kit.
As there is very little on the radio today that interests me I'm not too bothered but it looks nice in the dashboard. Regards, John.

[PaulR]

I think that Alan and John have hit the nail on the head. Firstly AM is not a good sound source, particularly these days when the signal is compressed and generally manipulated to be nothing like the original. Secondly radios in cars were much less common in "classic" days and the car manufacturers didn't put much or any effort into maximising the potential when they decided where to put and how to mount the speaker. Many cars had a single speaker mounted under the rear window pointing upwards to the roof lining - not the best listening experience for the driver.

In my experience the output from the amplifier in all but the cheapest car radios is pretty good if it has a good source such as FM or a CD. I have a Rover P4 which originally had a very similar set up. I managed to fit speakers into the panels on the outer side of both foot wells and this has made them sound better as they are more enclosed. It isn't anything like perfect due to the positioning of the speakers but it is better than it was originally.

Fortunately Radio Lancashire is still broadcast on MW so there is something to listen to but one forgets how the signal fades near to power lines, under bridges etc, etc when using AM.

[MGBGT1966]

Originally Posted by 'LIVEWIRE?'

It's quite possible that the amplified speaker in your link has a line level input, in which case it cannot be connected to the speaker terminals on your Hildesheim Radio. I'd be inclined to ask the seller for more information about that speaker first.

Thanks Livewire. Good point. I have tried to ask the seller, but he doesn't know for sure. These are OEM speakers for Chrysler, but I cant find the info on the internet so I might have to test it somehow. Would I risk damaging anything if I connected the speaker wires directly to a line input and started with a low volume? If it is indeed a line input I was thinking I might be able to use a converter like this one: https://www.amazon.co.uk/Speaker-Con.../dp/B004UA753G Any thoughts on this?
Thanks,
Gunnar

['LIVEWIRE?']

If the Hildesheim is similar to the first schematic in 'tri-comp's' link, then an added amplifier with line input could be connected by removing the blanking plug from the DIN socket and connecting the added amp's input to pin 1 of said socket, using a screened lead, with the screen going to pin 3. However, as others have said, you are never going to get high quality sound from an AM Radio. B.T.W., John, your Radiomobile 1070 looks as if it 'belongs' in that MGBGT. I'm not knocking the Hildesheim. Blaupunkt made some very good radios, but BMC would have fitted, or offered as an optional extra, Radiomobile or Motorola Radios. Gunnar, yes you could use one of those speaker to line level converters to match the radio's output to the amplifier's input.

[MGBGT1966]

Originally Posted by tri-comp

It is necessary to know exactly WHAT Hildesheim radio you have.
Hildesheim alone says nothing about what the radio contains or how it's built.
Some are made from the factory with an output to be used with an external amplifier, others not.
Look at the label on the side of your radio and report the number starting with 7, followed by at least 2 groups of numbers each with 3 digits.
That should pinpoint the version and open a way to find the correct schematic.
I've attached a file with 2 schematics for Hildesheim to show how big a difference there can be between two Blaupunkt radioes with the same name.
One radio (upper schematic) is made for connection to external amplifier, the other not.
The lower schematic shows a Hildesheim suitable for both 6 and 12V supply with negative or positive chassis.

Thanks Tri-comp. Im afraid I can't access the radio right now as the car is in the shop. I should be able to get to it in a few days. Given the mono output and old age, I simply assumed that the radio only had speaker outputs. Also, the radio has been adjusted to allow aux input (including a stereo to mono converter) by the previous owner, but I don't know how/where this adapter was connected. The front looks like this: https://www.ebay.co.uk/itm/VINTAGE-B...YAAOSwKJlc93-V

[MGBGT1966]

Originally Posted by snowman_al

Hi Gunnar,
If you believe the speaker is the problem, why not start by testing another, better, 4 ohm speaker in the car first?

Old AM radios do not sound anything like the FM and DAB you might be used to today. If the sound quality is poor to start with, adding another amplifier will not improve it.

Alan

Thanks Alan, yes true. I have considered this option and also tried a modern speaker with high sensitivity (93) I had access to. https://www.hertzaudiovideo.com/car-...ieci-dcx460_3/ Frequency response is more even on this one, but the experienced volume is much lower than the "original" speaker, despite the high sensitivity. I believe I should opt for a bigger speaker. Or possibly add an equalizer to the original speaker somehow.

[MGBGT1966]

Originally Posted by Heatercathodeshort

I have exactly the same problem with the Radiomobile 1070 fitted in my 1968 MGBGT.
The original speaker baffle, if you could call it that is more decorative than functional. The 7X4 speaker is designed to be sensitive rather than give a good bass response. It is a typical 'television' type of the period.
The radio performs well with plenty of volume and sounds good when connected to a decent speaker /enclosure but no bass with the car kit.
As there is very little on the radio today that interests me I'm not too bothered but it looks nice in the dashboard. Regards, John.

Indeed, looks great in the dash Thanks for sharing, sounds like I might have an original speaker too. It is very sensitive, but the timbre is painfully harsh. The baffle is well suited for a mono setting. if only the sound was a bit more powerful and less harsh.

[MGBGT1966]

Originally Posted by PaulR

I think that Alan and John have hit the nail on the head. Firstly AM is not a good sound source, particularly these days when the signal is compressed and generally manipulated to be nothing like the original. Secondly radios in cars were much less common in "classic" days and the car manufacturers didn't put much or any effort into maximising the potential when they decided where to put and how to mount the speaker. Many cars had a single speaker mounted under the rear window pointing upwards to the roof lining - not the best listening experience for the driver.

In my experience the output from the amplifier in all but the cheapest car radios is pretty good if it has a good source such as FM or a CD. I have a Rover P4 which originally had a very similar set up. I managed to fit speakers into the panels on the outer side of both foot wells and this has made them sound better as they are more enclosed. It isn't anything like perfect due to the positioning of the speakers but it is better than it was originally.

Fortunately Radio Lancashire is still broadcast on MW so there is something to listen to but one forgets how the signal fades near to power lines, under bridges etc, etc when using AM.

Thanks Paul. My concern is that I can only fit one speaker in the baffle and a relatively small one at that. Also, I believe the stereo could really use some power to keep up with the engine The stereo has been amended with an aux input (including a stereo to mono converter), so the source should be ok.

/Gunnar

[cheerfulcharlie]

Something like this would give you access to the modern world.

https://tinyurl.com/y4mom2mp

You could then connect what you like..even a Bluetooth transmitter and one of those cheap but usually good Bluetooth speakers available at some supermarkets etc.

Obviously, any old age deficiencies in the old radio maybe magnified but the modern attachments will probably reduce noise.

If you can nail down what model it actually is and somebody can provide a circuit diagram, it could well be possible to place a modern amp module inside the radio itself which will do it's best with the output of the receiver section.

[PaulR]

I fitted two speakers only because I briefly used a stereo FM radio in it. It was negative earth whereas the car is positive earth. I took a lot of precautions to isolate it but in the end my confidence in it ran out and I reverted the Radiomobile that came with it. I think that the point is that my speakers are now in an enclosed area which helps with the bass response. They are also better speakers than the original.

Part of my +ve/-ve earth precautions were to build a wooden box to enclose the radio. Could you make an enclosure for your speaker which would fit into the space? This might help with the bass response. Even something like an ice cream container might help, if only to try. I don't think that any sort of separate amp would help much if the speaker is mounted on a small, open baffle.

[Edward Huggins]

There seems to be room in that original fibreboard speaker enclosure for a larger speaker.

Car Scrappers/Breakers will usually have many 9" x 6", 4 ohm units which is a popular auto size. These are liable to have a roll surround to the cone for an improved Bass. If there is a concentric tweeter, this could be disconnected/removed to achieve a more "mellow" sound.

[MGBGT1966]

Originally Posted by 'LIVEWIRE?'

If the Hildesheim is similar to the first schematic in 'tri-comp's' link, then an added amplifier with line input could be connected by removing the blanking plug from the DIN socket and connecting the added amp's input to pin 1 of said socket, using a screened lead, with the screen going to pin 3. However, as others have said, you are never going to get high quality sound from an AM Radio. B.T.W., John, your Radiomobile 1070 looks as if it 'belongs' in that MGBGT. I'm not knocking the Hildesheim. Blaupunkt made some very good radios, but BMC would have fitted, or offered as an optional extra, Radiomobile or Motorola Radios. Gunnar, yes you could use one of those speaker to line level converters to match the radio's output to the amplifier's input.

Thanks Livewire, indeed I suppose there should be a DIN socket, as the radio has an aux input installed. I will look into it once I have the car back. Thanks also for confirming the line converter, I was a bit worried that the change of impedance it is causing could be damaging for the radio. All best

[MGBGT1966]

Originally Posted by cheerfulcharlie

Something like this would give you access to the modern world.

https://tinyurl.com/y4mom2mp

You could then connect what you like..even a Bluetooth transmitter and one of those cheap but usually good Bluetooth speakers available at some supermarkets etc.

Obviously, any old age deficiencies in the old radio maybe magnified but the modern attachments will probably reduce noise.

If you can nail down what model it actually is and somebody can provide a circuit diagram, it could well be possible to place a modern amp module inside the radio itself which will do it's best with the output of the receiver section.

Thanks Charlie, those speaker to line adapters seem worth looking into. It would definitiely open up the possibilities. I am not so concerned about hifi sound, as the engine noise is a serious bottle neck for any kind of audiophile experiences. Which is also the main reason I am opting for power/base rich sound here. Normally, I would be more picky about timbre and character.

[MGBGT1966]

Originally Posted by PaulR

I fitted two speakers only because I briefly used a stereo FM radio in it. It was negative earth whereas the car is positive earth. I took a lot of precautions to isolate it but in the end my confidence in it ran out and I reverted the Radiomobile that came with it. I think that the point is that my speakers are now in an enclosed area which helps with the bass response. They are also better speakers than the original.

Part of my +ve/-ve earth precautions were to build a wooden box to enclose the radio. Could you make an enclosure for your speaker which would fit into the space? This might help with the bass response. Even something like an ice cream container might help, if only to try. I don't think that any sort of separate amp would help much if the speaker is mounted on a small, open baffle.

This is a very interesting point about the speaker enclosure Paul, thanks. I will look into it. I might try and build something for the baffle. Regardless of speaker, iit would be interesting to see how it changes the sound. I am not sure how much space there would be to put it behind the baffle though, I seem to recall it is a rather tight area. Any experiences on this? Thanks