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Sept 22, 2018 6:15:05 GMT
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Morning,
I want to replace the radio in my old rover with a more modern unit. Trouble is that the car only has one centre speaker.
So how do I wire a radio with stereo outputs so that it drives the single speaker I have?
Many thanks!
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squonk
Part of things
Posts: 858
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Sept 23, 2018 9:05:24 GMT
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You cannot use both speaker outputs from the stereo, only one. If you try to connect them together you will damage the stereo.
Does the car have provision for a speaker in the rear (on the parcel shelf maybe)? If so, you could wire up one channel to the front speaker and the other to the rear speaker. Or put a single pod speaker on the rear shelf and use that.
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2004 Chevrolet Avalanche Z71 2005 Mercedes CLK320 Cabriolet 1996 Mercedes C180 Elegance Auto Saloon 1996 Rover 620Ti (Dead fuel pump) 1992 Toyota HiLux Surf 1987 Range Rover Vogue (Rusty) 1992 Range Rover Vogue SE (More Rusty) 2006 Chrysler Grand Voyager 2008 Corsa 1.4 Design
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RetroMat
Posted a lot
Column Shifting!
Posts: 3,442
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Sept 23, 2018 9:17:05 GMT
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Connect up just one speaker then set the fader and balance on the new stereo to that speaker.
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squonk
Part of things
Posts: 858
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Sept 23, 2018 11:27:48 GMT
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Connect up just one speaker then set the fader and balance on the new stereo to that speaker. Great if you are using a mono source but not so good if it is stereo. On older recordings (Beatles for instance) this would sound very odd. The mix on their erlier tracks was brutal, often putting the majority of the vocals on one channel and the music on the other.
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2004 Chevrolet Avalanche Z71 2005 Mercedes CLK320 Cabriolet 1996 Mercedes C180 Elegance Auto Saloon 1996 Rover 620Ti (Dead fuel pump) 1992 Toyota HiLux Surf 1987 Range Rover Vogue (Rusty) 1992 Range Rover Vogue SE (More Rusty) 2006 Chrysler Grand Voyager 2008 Corsa 1.4 Design
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Sept 23, 2018 11:31:26 GMT
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1953 Minor (Long term project) PT Cruiser
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squonk
Part of things
Posts: 858
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Sept 23, 2018 11:34:49 GMT
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My god those are expensive!!! Are they made of unobtanium or something!!!
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2004 Chevrolet Avalanche Z71 2005 Mercedes CLK320 Cabriolet 1996 Mercedes C180 Elegance Auto Saloon 1996 Rover 620Ti (Dead fuel pump) 1992 Toyota HiLux Surf 1987 Range Rover Vogue (Rusty) 1992 Range Rover Vogue SE (More Rusty) 2006 Chrysler Grand Voyager 2008 Corsa 1.4 Design
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Phil H
Posted a lot
Posts: 1,448
Club RR Member Number: 133
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Sept 23, 2018 12:18:06 GMT
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Morning, I want to replace the radio in my old rover with a more modern unit. Trouble is that the car only has one centre speaker. So how do I wire a radio with stereo outputs so that it drives the single speaker I have? Many thanks! In short, you can't. You have 3 choices - run two speakers (so add another - or try and fit 2 where the existing single unit is which might be possible if it's a large oval) or go with one of the combined speakers linked to. Third option is a "Ceiling Speaker Transformer" - used for piping sound around buildings. First one I found with a google is this one: www.ceiling-speakers.co.uk/KEF-Audio-Stereo-to-Mono-Transformer-accessories-127.asp No idea if there's any degradation in sound quality though - and how good is the existing speaker anyway?
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Sept 23, 2018 13:08:06 GMT
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I thought you could do it with a couple of resistors in each positive line, sure I did it years a go on an old car
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RetroMat
Posted a lot
Column Shifting!
Posts: 3,442
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Sept 23, 2018 13:46:07 GMT
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Connect up just one speaker then set the fader and balance on the new stereo to that speaker. Great if you are using a mono source but not so good if it is stereo. On older recordings (Beatles for instance) this would sound very odd. The mix on their erlier tracks was brutal, often putting the majority of the vocals on one channel and the music on the other. It has worked for me in the past, by sending the sound to one speaker like left front and wiring the single speaker to that channel. The stereo puts both channels together, so it sounds normal. Depends on the stereo though I suppose.
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Sept 23, 2018 17:12:52 GMT
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All the radios i have, even the cheap aldi ones have the option to set to mono, hopefully yours will as well.
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Sept 23, 2018 18:30:00 GMT
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This is the best advice yet, specifically these speakers from right at the bottom of the linked page (though they also do oval ones) www.retrocarstuff.com/shop/speakers/d52-dvc-speakerThese have two separate voice coils in the woofer, one for each channel, and a separate tweeter for each channel, all in a package the size of a single speaker. £ 45 seems pretty reasonable to me. Nick
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1967 Triumph Vitesse convertible (old friend) 1996 Audi A6 2.5 TDI Avant (still durability testing) 1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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Sept 23, 2018 20:30:48 GMT
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Thanks for all the replies guys! The head unit is only a super cheap one off eBay, as featured in jim's Cortina thread here: forum.retro-rides.org/thread/121379/1966-mk1-cortina-gt-colour?page=14Fiddling about with it today I found that it does indeed have a mono setting, so that's what I've set it to, with only one output in use to drive the single centre speaker. The fact that is was so cheap, and so is probably never going to give amazing definition, coupled with the fact that I am practically deaf in one ear means that this is probably how I'll run it for now. Cheers all
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Sept 24, 2018 21:19:00 GMT
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The mono button on a car radio normally just operates on the FM section. Stops it trying to decode the stereo when the signal is getting a bit weak and hissy. That said, your radio looks to be a retro style thing so it's possible they made it thinking that there might only be one speaker fitted. What's the instruction book say the mono button does?
You could do to make up a USB stick (or similar) with left only and right only sound to test it with.
Anyhow, if you are lucky you could also try this. Wire the speaker between 'Front Right +' and 'Front Left -' and, with a bit of luck you'll get something close to mono and not annoy the head unit. If you are interested why it works I can try and explain.
James
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Sept 25, 2018 8:58:05 GMT
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James, I would love to have an explanation!
As for the instructions, they are very thin on the ground, and written in best Chinglish, so nothing useful there... However, for £15 delivered I am still pretty happy with it!
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Sept 25, 2018 20:26:41 GMT
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Give me a short while to knock up some pictures and I'll explain all. Well, I'll try, we'll see how good I am. Meanwhile, go look at something like this site... (Picked at random from google - other sites exist) www.audiocheck.net/audiotests_stereo.phpYou can download 3 files to a USB stick. One for left, one right, and one both channels. Play them in your car... If your mono switch is doing what you hope you'll hear all 3. If not you'll not hear one of the files. James
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Sept 25, 2018 22:05:19 GMT
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Forgive me if you are reading this and I’m being over simplistic / far too complex. I’ll pitch it somewhere and see what happens. If you have questions just ask and I’ll try and answer. First we need to know a bit about the power amps in car radios (and loads of other places to be honest). Any decent car hifi made since the 1980s will almost certainly have “bridged” speaker outputs. What I mean by this is that both wires that connect to the speakers are driven with an audio signal. Like this… Slide10 by Sweetpea238, on Flickr For each output of your radio, and your £15 radio has 4 outputs, left and right, front and rear (how do they make it for £15? it’s incredible)… For each output of your radio you have something like the picture. A small audio signal comes in the left side and the amplifier makes it bigger (the top half of the picture). But the signal splits and goes through that box I’ve called “phase”. That turns it upside down and then it too gets amplified. This means that when the + output is swinging upwards the - output is swinging downwards. And visa versa. Now you know why your speaker wires are marked with a + and -. The speaker sits across the two wires. Bridging gives us a significant increase in audio power output. And in a car we need all the grunt we can get. The alternative to this bridged output is that we just drive one side of the speaker and connect the other side to ground. That saves us a load of components but we get less power. Ok so far? So how does this help with your problem of getting a mono output by devious means? What I told you to do is this (or something like it)… Slide11 by Sweetpea238, on Flickr Now I’ve drawn the left and right power amplifiers. Both bridged. I’ve wired the speaker between the + wire on the left channel and the - wire of the right. You can do it the other way round, it makes no difference so long as you take the + of one and the - of the other. So far as the speaker is concerned it’s still getting both its wires driven and they are ‘out of phase’ as audio engineers describe it. So the speaker is happy. But because the + wire is coming from the left channel and the - output from the right any signal that’s just in one channel is still seen by the speaker. You’ve (sort of) created a mono output for free. Does that make sense? Yer never get something for nothing. What’s the disadvantages? Well most audio amplifier chips (yours is a sweet little thing known as a TDA7388) have some form of protection to stop them getting destroyed if something goes wrong on the output. Normally if one of the speaker wires gets connected to ground, or to 12 volts, or even if they are shorted together the amplifier will shut down until you fix the problem. There is a chance that it’ll notice the unbalanced output (the fact that you are drawing current from only half of each speaker output) and protect its self. It’s pretty unlikely though because it’s not a condition that would cause damage. Another problem is that it’s likely to sound a little dull. Most of the bass signals are the same in both left and right channels. So our speaker is driven with a signal from both sides. But a signal that’s paned hard left is only driven to the speaker from the left channel (rather than both) so it’ll sound quieter. Now, it so happens that the “stereo signal”, things that are different between channels, things that are pushed towards the left or right side, tend to be in the higher frequencies. (I know that doesn’t seem make sense at first sight but it’s true.) This means that the higher frequencies tend to be a little quieter than they should be because only one amp is driving those signals into the speaker. So it sounds a little dull. The solution is simple. Turn the treble up a bit. Stereo has come a long way over the years. These days it’s quite subtle and the statement that it’s mostly in the higher frequencies is reasonably true. The exception to this would be recordings like the early Motown stuff where they tended to pan things hard left and right. Those recordings will likely have a stereo component at lower frequencies. Anyway, wouldn’t it be interesting if you could actually listen to the difference between channels? Well I’m a wizard and I can make that happen for you. Just wire your speaker between the + of the left and the + of the right and all you’ll hear is the stereo component. Hope that makes sense. James
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Last Edit: Sept 25, 2018 22:07:49 GMT by Sweetpea
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Sept 26, 2018 11:44:29 GMT
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That's what I love about this forum, the depth of knowledge and the fact that people will take their time to post up interesting stuff!
Thanks for the explanation, much appreciated - i even think it makes sense!
I am pulling the chassis out from under my old Landrover 90 this weekend, but might get a chance next week to try switching the wires about as suggested, i will report back!
Thanks again
Jamie
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Sept 26, 2018 12:55:41 GMT
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You are very welcome. Hope it goes well with the Landy!
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Sept 26, 2018 14:57:57 GMT
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What a great explanation from Mr Sweetpea! its not even my thread but loving the reply set out in a way that even I can understand and make sense of!!
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Sept 27, 2018 22:33:55 GMT
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I'm going to look a massive prat if it doesn't work! It's been a long time since I've tried this sort of thing. Maybe I should quietly sneak off to the garage and quietly try it... My rust bucket of choice is the MK1 MR2. Some of the early models had a sub woofer fitted under the drivers seat, or at least the wiring for it. According to the wiring diagrams there were a couple of ways of getting the mono feed for it but one appears to have used the trick above. Something like this below... Slide9 by Sweetpea238, on Flickr I'm not sure exactly which models were wired this way. I know mine isn't 'cos I took the sub apart and traced the amp's circuit board to find out how it works. Sad git. James
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