can someone shed soem light on speaker impedances for me (replacing videologic digitheatre speakers)

[downhiller80]

I've got a set of dolby 5.1 Videologic Digitheatre speakers with the decoder. This is (obviously) 2 front speakers, 2 smaller surround speakers, 1 centre speaker and a sub.

The setup on a whole is pretty loud, but I want real-in-your-face loudness with no distortion.

The decoder is allegedly a pretty good one so I am happy keeping that for a while.

The sub reverberates horribly above a certain volume, as do the other speakers. The volume knob still has a way to go when this distortion occurs. Does this imply that the speakers are the weak points or the amplifier?


One of my favourite speaker "modes" is to map the stereo signal (for mp3's etc) to the surround speakers so as 2 have stereo sound coming from 4 speakers. hence I want identical speakers for front & surround.

The current ones have an impedance of 4ohms, do I have to match this?

Any other advice on improving this setup?

Seb

 

[lenjack]

All speakers have limitations...at a certain level they will distort. The setting on you volume control is not important. There should always be some room left on the control in a properly designed system. As for impedance, this is not normally of real importance. Check your manuals.

 

[Noriaki]

Don't let the impedence get to high or it will stop the current.

Don't go using like a 200 megaohm impedence wires or anything silly..

But anything on any speaker you see will be fine. The DigiTheatre comes with a pretty good amp so it should be able to handle anything standard.
I'd say 4-32 ohm is probably about "normal" and that amp should handle anything in that range...


If you want really massive loudness above all else, check out the Klipsch ProMedia's...I don't like them much personally, but they have the most powerful Sub of any computer targetted set of Speakers out there.
The sats are pretty powerful to, I just hate the horn tweeters, but that is 100% personal preference. Without going into a real home stereo setup these are about as loud as they come.

 

[Goi]

Its advisable to match the impedance. As impedance goes down, your maximum power rating will go up too. 4 ohms is already quite low, its the standard for car audio speakers. Home hifi speakers usually have 6 or 8 ohm impedance.

 

[bigjon]

Remember too that the lower the speaker's impedance, the louder it will be (since it's drawing more current from the receiver). This is not good, since it will overpower the other speakers, and does nothing for maximum loudness, which is still limited by the amplifier (with higher impedance speakers you just have to turn the volume up higher).

Maybe I'm getting way too deep here, but this analogy really helped me out when I was learning about this stuff:

The easiest way to understand this is to think of electricity as water:

1. Voltage is much like water pressure (higher voltage = higher pressure).
2. Impedence is like a dam (the higher the impedance the higher the dam)
3. Electrical current is much like water current (or water speed).
4. Current is determined by the Impedence (more current occurs when there is less impedence - just like there is more water flow when the dam is lowered).
5. Power (wattage) is like the total amount of water. To get more water/power, you can either increase the water pressure/voltage or the current.

Of course the water pressure/voltage affects all of this - if the water pressure/voltage is high, more current will flow over the dam and the power/total water will be higher.

So, if you use 8 ohm speakers instead of 4 ohm speakers, you are "raising the dam," and less current will flow (and therefore less power will be used) for any given voltage/water pressure. Of course, you can still raise the volume/voltage/water pressure and end up with the same amount of power/water going over the dam (thru the speaker).

As far as the sub goes, it does sound like a distortion problem since all the speakers have this reverberation effect. Does the distortion sound high-pitched, like static (if so the problem is the amp being underpowered), or does it sound more like the speakers are "popping" (probably under-powered speakers)? The fact that the sub has the same problem makes me think the speakers are under-powered. Either way, you run the risk of killing speakers (over-powered amps kill woofers and midranges, under-powered amps kill tweeters because when the amp is driven into distortion it emits a ton of high frequencies).

BTW, the placement of a sub in a room makes a surprising difference in the amount of "boominess" at different frequencies. If it's located in a corner of the room it will reverberate much more than if it's located near the center of the room or at least away from the corner. Doesn't sound like the same reverberation you're talking about, but just in case, you might want to try changing the sub's placement in the room (put it in the corner for louder bass, away from the corner for cleaner bass)

Good luck!