Which Sub/Surround/OHM?

vandool

Hello Fellow PolkAudio fans! A few questions and hope you can help.

I have the following at this time:

RTi10's (Front)
CSi5 (center)
FXi3's (surround)

Connected to a Onkyo TX-SR803S.


I am looking for a second set of surround speakers for THX or 7.1.

Now I wish I had went with FXi5's. Do you think if I purchased the FXi5's for the surround speakers and use the FXi3's as the surround back speakers, any issues with this? Or should I stick with all FXi3's? Will this also effect the Timbre Matching I have going on?


Also I am looking at two model sub-woofers: PSW404 and PSW505. In the System Builder, the speakers I have recommend the PSW404. What are the reasons not to purchase the PSW505? Will this effect the Timbre Matching I have going on?


One more question. The Onkyo Receiver I have, it can be switch to 6ohm's or 4ohm's as well as the standard 8ohms. Would 6ohm's damage any of the speakers I have above? My understanding of OHM's is the lower the number the more power/watts it can produce?

I guess this OHM's stuff is also called Speaker Impedance in the Onkyo Receiver manual. I guess I have a choice of 4 or 6 ohms. If you can clear this part up in my head, I will be very happy!!

Thank you inadvance.:)

EricBurg

I guess the simple solution to your question about ohms is to set your reciever to the same value that your speakers are rated at.

With that said, there is a physics principle called Ohms Law that deals with the conduction of electricity through a closed current. The formula is
V=IxR
V is Voltage, I is current (amps) and R is resistance (ohms)

The higher the nominal impedence of your speakers (ohm rating) the more resistance they offer to the conduction of electricity through the circuit. In a home system, the voltage is constant, usually 110 volts in a normal home circuit. So, if you alter the resistance by changing to 4 ohm speakers, theoretically you should see an increase in current equal to the factor you decreased the resistance by.

Ok, now a couple of problems with this in reality...1) Ohms are never constant throughout the entire frequency spectrum. Your speakers are nominally rated at 8 ohms, but they may drop to as much as 4 ohms during different frequencies. 2) amplifiers are never 100% efficient. Unfortunately, a lot of energy is lost in the form of heat. This will ultimately limit the wattage available to the speakers, as well as the life and performance of your equipment. Lots of amps have thermal or current limiting circuits to protect themselves. 3) most amps on recievers are only measured/rated with 1 channel driven at a fixed frequency (1khz). This is important because the more speakers you add to the amp, the current has to be distributed and usually they only have 1 power supply. So, when you elvaluate any amplifier, you should look to see that the manufacturer provides their wattage in all channels driven at a low distortion throughout the entire frequency spectrum (20-20khz). External amps use beefy power supplies that can output higher current.

ok, now on to your question about subs...This is the one speaker that you shouldn't worry about any timber matching. There is no real benefit in the sub bass range to keeping the manufacturer. The phase adjustment and crossover is all you need to match your subs with your front speakers and most subs have these on their internal amplifiers. My suggestion is to look at some of the online offerings from SVSound, Hsu or Outlaw. I think for the money, these subs can't be beat. They will completely outperform any of the Polk offerings. Do some searches on this site and you see what I'm talking about. I have never heard anything bad about any of these sub manufacterers or their products...ok, except for the occasional...I wish I had gone bigger...

Hope some of this helps.

Eric

kingkip

As far as the first question, it would be fine to use the 5s and 3s as they are timbre matched.

With that many speaks on your onkyo, I would highly reccommend a separate amp for your 10s. You will notice quite a difference of sound quality up front if you do.

Welcome to the club.

vandool

WOW, Eric. Thank you for taking the time and explaining all of that. And I will look into the SVSound, Hsu and Outlaw.

Kingkip, as for setting up a separate amp for the 10's any suggestions? Also with the added amp, will I lose any of the DTS/THX parts buy leaving the Onkyo Receiver? I guess I am a little fuzzy on adding a second amp. So any suggestions would be great! Thank You.

kingkip

No you won't lose any of the processing. That takes place in the receiver and it passes along the signal to the amp which theoretically only amplifies the signal going to the speaks. That is the theory anyway. Amps will add their own "color" to the sound. So the best way to find an amp is to listen to them, preferably on your setup. Usually that is pretty tough to do, but listen to as many as possible.

That being said, I like parasound, outlaw and marantz monoblocks among others. Depending on how much money you want to spend you can buy new or look at the flea market, audiogon, ebay and the like.

As a rule of thumb the 10s will take as much power as you give them and want more. I would look for 120 watts per channel or more, with more usually being better. However, there are alot of great amps that put out plenty of power for those speaks even though they have a lower rating.

Search around in the electronics area and you will find plenty of reccomendations for 10s and 12s as well as how amps do their thing.

Good luck and keep the ?s coming.

kingkip

By the way I forgot to mention setting up an amp is really easy. Just need to plug it into the wall and run interconnects between the receiver and amp, and then speaker wire from the amp to the spooks.

vandool

kingkip wrote:

That being said, I like parasound, outlaw and marantz monoblocks among others. Depending on how much money you want to spend you can buy new or look at the flea market, audiogon, ebay and the like.

As a rule of thumb the 10s will take as much power as you give them and want more. I would look for 120 watts per channel or more, with more usually being better. However, there are alot of great amps that put out plenty of power for those speaks even though they have a lower rating.

Thank you for all the help Kingkip. Also sorry for the delays, don't get much time and when I do I do research a lot.:) Now, I don't have the luxury to find and test each amp out. But what are you feelings on the Outlaw Model M2200. It's a single channel, 200-watt amp for $325 or $624 for a pair. Which I am assuming I would need two one for the right and one for the left channel. Is this enough power or too much for the Rti10's? The other reason for this model is the slim design only 3.75" high (thats great!!) for my setup.

I use my system for both movies and satellite radio (XM). But I feel that the RTi 10's is missing something. At this time I am not using a Sub and maybe I should use a SUB before the AMP? What are your suggestions?

Thank You.

David