Ok I just purchased some 8ohm speakers for my cec. The originals are rated at 4ohm but from what I have been reading they will be fine. I was planning on trying to get some small 8ohm tweeters to run in parallel to bring ohms down to 4 but i really want to keep the originality of no tweeters. Anyone have any insight to offer me.

They will be about half as loud because the resistance is twice as much.

On the other end if you tried driving 2 ohm speakers the load on the amp cicuit would be too great...

It's best to stick with same OHM and a high
efficiency rating....

Johnny

You can run an 8 ohm resistor in parallel instead of the tweeter. Get one with the right ratings though.

Radio Shack has an 8-Ohm Non-Inductive Resistor for $2.49 Catalog #: 271-120O
"Use this device for protection and current control in your electronics. The 8-Ohm Resistor is rated 20 watts. 5% tolerance. Helpful in high-power audio connections and projects."

This wont affect the sound quality and will it then be like a 4 ohm speaker

quote:

Originally posted by 71spud:
You can run an 8 ohm resistor in parallel instead of the tweeter. Get one with the right ratings though.

I dont think it is a good idea. It wont help in efficency but wasted heat is produce from the added resistor. The 8 ohm speaker is just fine you get maybe half power from the amp compare to an 4 ohm speaker. You might save on battery with lesser loudness. Your power amp ic might live longer....But best to get the same ohm rating but with better fidelity speakers.

By adding a tweeter to the woofer you need a crossover or a simple capacitor to form a simple crossover. Theoritically the amp still see it as 8 ohms coz at lower frequncy your main/woofer speaker will respond but not your tweeter. Therfore the amp sees it as 8 ohm loading coz by your main/woofer speaker. At higher frequencies the tweeter will respond but maybe your main speaker will not respond well. Your amp will see it as 8 ohm loading coz by your tweeter. Actually if you were to see to look at any speaker impedance versus frequecy response graph it varies. Therefore impedance rating are normarlly rated nominal ratings. Nominal 8 ohms or nominal 4 ohms.

For the amp point of vie will be the same.
But you will feel only a half of power, since the other half is spent over the resistor.
The other solution (I don't like the difficult way) is an output tranformer to do the impedance matching betwen 4 and 8 ohms.

I also read the output transformer will cause more distortion

quote:

Originally posted by SUCCESS:
For the amp point of vie will be the same.
But you will feel only a half of power, since the other half is spent over the resistor.
The other solution (I don't like the difficult way) is an output tranformer to do the impedance matching betwen 4 and 8 ohms.

quote:

Originally posted by baddbill:
I have also read that the speaker impedence of 8 ohms can vary between 6 and 10 ohms

I would agree with that, I've used my meter to test speakers, and have seen that an 8 ohm rating might be like 6.7 or 9.1.... weird but true.

Johnny

Yes, the add distortion.

But not all kinds of distortion are bad. Figure the tube amps with output transformer.
you have tons of distortion (compared with a solid state amp) only in the tube operation, and then the output transformer ... but they sound nice (that's a little subjetive)

And you will be suprissed to know how many boomboxes have and output transformer ...
With them, they had doubled the output power.
I have about four National Panasonics with output transformer. If you ask me ... I'm not sure, but I would prefer the transformer.
Some people think that they delivers warm sound because it's distortion. Again, that colud be subjetive

Have a look there

http://www.lennartlabs.se/philosophy/greathobby4.htm

Only an opinion for me, but some ideas makes sense.

Pedro

quote:

Originally posted by baddbill:
I also read the output transformer will cause more distortion

quote:

Originally posted by SUCCESS:
For the amp point of vie will be the same.
But you will feel only a half of power, since the other half is spent over the resistor.
The other solution (I don't like the difficult way) is an output tranformer to do the impedance matching betwen 4 and 8 ohms.

I never understood this: if boomboxes are trying to get the most out of what is already a low power rating, why don't they all have speakers with the lowest ohm possible to maximize the sound? The Bose in my Maxima runs on less than 1 ohm and the bass out of those 6.5 inch rear woofers is INCREDIBLE. They have a nice, airy subsonic growl that they reproduce with ease. And the system is only rated at 200 watts. I'm sure the low ohmage helps in getting the most out of the amps. So generally speaking, why don't bbx's do the same thing?

The manufacturer have to consider Battery consumption. Lower ohm traslate higher wattage, more current drawn. It make no sense if one have a boombox that eats batteries like mad. The manufacturer have to compromise between loudness and battery consumption. The best is to find a better efficent speaker with better fidelity.

Early were 8 ohms, but as they used output tranformer, perhaps the impedance seen by the amp was nearly the half or less (4 ohms).
And the voltage swing at the output transfomer were twice the output voltage in the amp.
That's the way the doubled the power for an 8 ohms speaker runinng at a cetain DC voltage.
But then moved to 4 or 3 ohms avoiding the output tranformer (which is expensive).
3 ohms looks like the best trade-off betwen power consuption and battery life.

Hey guys thanks for all input

Very interesting discussion indeed - thanks for all the knowledge