Just searching on the web and looked into the channel vision A-bus, nice setup. I believe that is what I will use did not anticipate to pay that much but I figured the cost of all the other parts i was planning on using may justify about half of what this kit will cost me. Will I then be able to use my 2nd source on my reciver for the input signal. again thanks for all the input

The problems are more subtle than those listed.

Yes, every switch box I have seen has a resistor in it. I think I once saw one with 2 ohms, just enough to keep the load above 2 ohms if eight or so speakers in parallel were in series with this resistor.

Let's look at the frequency response.

First, one speaker. Speakers have different impedance values at different frequencies, so putting a resistor, which has the same resistance at all frequencies, in series with a speaker will affect the amount of power getting to the speaker at each frequency, and thus the frequency response.

In a typical speaker system, there is a bass resonance (or two) that usually peak well above twenty ohms. I a, being conservative; I have seen 60 ohm peaks. If you feed your amp output through a resistor, the response at those peaks will be changed very little.

But an octave above those peaks the impedance is usually around 8 ohms. That means that 1/3 of the power going to the speaker at that frequency will be absorbed by the resistor. Result? Lower output in the midrange.

The crossover should keep energy out of midrange and tweeter drivers at their resonance, so the effect will be similar to that on the woofer in its eight ohm-ish range.

But I have also seen well-designed speaker systems vary in midrange and tweeter impedance from six to ten ohms. Thus the resistor will affect frequency response.

Add to this that old bugaboo, damping factor. A speaker is a motor, and it should move, then stop, to put out the sound that is fed to it. To do this, the amp and all associated wiring has to have zero ohms impedance. This is impossible, but the lower the impedance of the source feeding the speaker, the better controlled the woofer motion will be. (Midrange and tweeter motion are better controlled for various reasons.) When you put a resistor in series with a speaker, you lessen the woofer's ability to stop moving when the voltage drops to zero, so the bass can become less clear.

On all of the above, there is one last issue: can anybody hear any of this? It is real, and it is measurable, but most of the distributed audio systems I have heard sounded pretty good!

Now, take two speakers, put them in parallel, and use the same resistor; this will be like putting an eight ohm resistor in series with a single speaker. Make it four speakers in parallel, and this will be like putting a 16 ohm resistor in series with each speaker. Thus the effect of that single series resistor increases as the number of connected speakers increases.

Turn the volume up and down, and the volume control will offer slightly different impedances to the switch box. Now the frequency response varies as the volume varies, in addition to not being accurate.

Again, can we hear it? Don't forget that the frequency response of our ears varies with volume. At lower volume, we generally hear low bass and high highs less well. How can you tell if a speaker's frequency response is varying with volume when your ears vary with volume?


To sum up, I personally would go with the cleanest method, especially if there is any chance that different rooms will EVER want to play different audio: use the multiple channel amp with volume controls in each room, or line level volume controls in a preamp before each pair of amps, as in a multi-room situation. Sometimes such an amp is not in the budget, or is not in the budget for this year: I have put in many single-amp, big transformer, impedance-matching volume control systems, which are not the best. But they sure sounded good!

I went into a McDonald's one morning and saw an old gal, wrinkled face, sour expression (only thing missing was a cigarette with two inches of ash dangling from it), wearing a T-shirt that said

"Don't get me started. You know how I can be."

I see after writing that last post that maybe I should have just written THAT.

Channel Vision A-Bus, is that a good setup? And will my second source from my current theatre receiver suffice to run the audio for this A-Bus system?

Thanks alot for the help

garciahomes - I do not want to mess with guys in here ( for me they are professionals) and they help me every time , when I need - couple times they saved my ass. Our company install A-bus system for a lots of houses , where is no buyer yet. For builders good price , easier to sell house and for us easy money :-) We always pull 16/4 and Cat.5 from audio cabinet to each volume control and 16/2 from volume control to speaker locations. In this setup is possible upgrade to CAV 6.6 or other (more expensive , better keypads - for bigger houses) . You can hook up on A-bus all, what has line out RCA jacks - so cd player or boom box is able to feed your home sound + check out local sound module (for kids bedrooms...).Your second zone of your surr. receiver is great.Again-this is realy cheap and no high-end solution .. If you love excelent high-end sound and you want to spent more money do not listen to me!! Where is your location? Maybe I can show you how it looks and works in model home.I am from Chicago south west sub.

robsaudio

thanks again to all for the great responses, thank you for sharing inexpensive versus high end. you gave me exactly what i felt i wanted to hear and have convinced me that this is the best system for me at the price range of this home. i called channel vision today and tried to determine the best method of terminating at the audio wall but they had no solution, should i just hand the cat5 out of the wall?

OK-on volume control side (kitchen,office.....) leave 1feet long wire , make loop,leave in wall and put low voltage ring on stud(1 CAT.5 + 2 16/2 for speakers). If you plan unit for A-bus in audio cabinet , pull all Cat.5 through single low voltage ring (tv/ph jack). A-bus unit is coming either in wall or surface mount.Check out Russound web site www.russound.com .Cut holes for units later , but make sure there is enough room behind drywall. I like more that surface mount ,do not need hole in wall, but you will need more tools (RJ45 jacks).I leave wire for speakers behind drywall (bigger loop in ceiling or wall) , because if you use rough-in plates ,it is hard to cover hole if you decide do not install speakers yet or you want to smaller speakers then before.Take pictures and measure better two times. You should be one of the last people on construction before insulation and drywall.Good luck and enjoy...