Radio- speaker question

[EScanlon]

Beerman, read the WHOLE post and you'll see why your answer... while technically correct, if the question were just, how can you equate an 8ohm speaker with two 4 ohm speakers, is TOTALLY WRONG for this application. (And some audiophiles will still discuss the HOW you connect in series as being important not only in circuit but also in acoustic response.)

In this case, your "fix" is actually the WORST thing you can do for that radio. You're essentially DOUBLING the speaker rating.

We're dealing with a 40+ year old radio that used technology and components probably 50 or so years old by now, with ratings of 4 Watt, 10% THD, and designed to use ONE 4 ohm speaker.

E

[manny1973]

Checked today, Radio shack. Car Toys, Wallmart. and another local stereo shop. The only 8 ohm speakers avail are woofers all of the others are 4 ohm. So What do I have to do to use 4 ohm speakers?

[EScanlon]

http://www.amazon.com/dp/B0002ZPSBY/ref=asc_df_B0002ZPSBY1734134?smid=A385A0XNQBW8HY&tag=nextagusmp0351057-20&linkCode=asn&creative=395105&creativeASIN=B0002ZPSBY

http://www.allelectronics.com/make-a-store/item/GM-858/5.25-60W-MIDRANGE-DRIVER-8-OHM/1.html

No qualification as to suitability for your intended use.

E

Edited October 22, 2011 by EScanlon

[beermanpete]

I agree that a series connection is not ideal but since 8-ohm speakers don't seem to common any longer it is a workable option. It will not hurt the radio. The worst problem will be the decoupling of each speaker from the output of the power amp and therefor soft bass. Does that really matter here?

Another option is using a 4-ohm resistor in series with each 4-ohm speaker and then paralleing the pair, resulting in a 4-ohm load on the radio. The bass will still suffer a bit however.

A better solution might be using a "booster" amp that is designed to be driven by the speaker output of the radio. This will present a suitable load to the radio and isolate the radio from the speakers allowing the possability of more power and tolerance to a 2-ohm load. The booster amp could easily be hidden under a seat or in the dash to preserve the factory look.

Edited October 23, 2011 by beermanpete

[5thhorsemann]

Once again, the radio is designed to supply an INDUCTIVE LOAD. The crossover is an inductive load that modifies the output to support multiple inductive loads, they cost like $20.00 and are the size of a pack of cigarettes. Doing things rite the first time saves time and money, and in this case the original radio.

[beermanpete]

Once again, the radio is designed to supply an INDUCTIVE LOAD. The crossover is an inductive load that modifies the output to support multiple inductive loads, they cost like $20.00 and are the size of a pack of cigarettes. Doing things rite the first time saves time and money, and in this case the original radio.

Not exactly. The radio is designed to tolerate a reactive load. How does connecting the speakers in series change the load to a non-inductive or non-reactive load?

The "crossover" is not a crossover anyhow, it is a transformer which matches the impedance of the load to the source. When transformers are used in their linear range (as it would be for this application) they will not add or subtract any reactance, the reactance of the load is simply presented to the source in its normal form but with the magnitude altered according to the transformer's turns ratio.

[5thhorsemann]

Not exactly. The radio is designed to tolerate a reactive load. How does connecting the speakers in series change the load to a non-inductive or non-reactive load?

The "crossover" is not a crossover anyhow, it is a transformer which matches the impedance of the load to the source. When transformers are used in their linear range (as it would be for this application) they will not add or subtract any reactance, the reactance of the load is simply presented to the source in its normal form but with the magnitude altered according to the transformer's turns ratio.

Wa-WHAT? It's caled a "CROSOVER" because it "crosses over" the load. The transformer keeps the inductive load "stable" when highs and lows of music signal pass through the coils of the speakers. That little resistor you see on the back of the speaker is there to compensate for heat buildup in the coil of said speaker, in parallel, to provide for the reactive inbalance.

If you take two 8 ohm inductive loads in parallel, they effectively form one inductive load of of under 4 ohms, depending on signal intensity and strength, not like a set of resistive loads which will devide themselves in half over the circut. If you place succesive inductive loads in series the resistance will degrade with each load as the magnitute of the power source deminishes through the previous load or device. This is the reason you can not wire unregulated alternators (AC generators) in parallel or series. The back feed voltages become circuit fatal to the individual devices over time. Of course all this depends on the intensity of the power generated, again we are talking 4 watts. We are however talking a 40 some odd year old radio that will be a PITA to replace.

Buy the C/O and be happy.

Edited October 24, 2011 by 5thhorsemann

[FastWoman]

I think beerman's onto something. Feed the output of the radio into both the L and R channels of a booster/equalizer doobob. Here's the thing: SOME of them have pseudo surround -- basically a button you can hit to introduce some very minor reverb that will give the sound some pseudo-stereo "presence." You can output to 4 speakers (2 up under the dash). Because you're not actually loading the radio (much), the sound will be somewhat less crappy/distorted than if you were driving a speaker. Yeah, that's what I'd do (if preserving the original radio is important, that is).

[manny1973]

I like the sound of that. If I hook the radio up to an equalizer, speakers into the input, I can then hook up two 4 ohm speakers to the output of the equalizer. And just to be sure this would not hurt the radio?

[EScanlon]

As long as the equalizer accepts an amplified input signal, it would work.

E

[manny1973]

In Case anyone's interested I did find 8ohm speakers check out these sites

http://www.turnswitch.com/speakers.htm

http://www.skycraftsurplus.com/5-14roundcoaxialautomotivespeaker.aspx I bought the cheap one. Thanks to everyone for the help. Escalon, I appreciate your input.

[FastWoman]

Like Escanlon said, yes, it will work fine. In fact it will work better than just a speaker.

Look for an equalizer/amplifier with "surround sound" effects, like this preamplifier has:

http://notebooknerds.com/sony-xdp-u50d-digital-car-stereo-pre-amplifier-customize-sound-from-your-cars-audio-system/

That will give the monaural sound a certain "liveliness" that will simulate stereo/quad. And THAT is probably as much as you can make out of a low-power monaural output.

(Just to be clear, you need an amp, not a pre-amp, so you have to keep looking. This unit won't do what you need. I just has the effects you need.)

Edited October 26, 2011 by FastWoman