View Full Version : Ohm ratings for speakers vs. receivers......
12-17-2002, 02:36 AM
Help me understand........
OK......so generally I understand the Ohm rating thing, but here's my question. I know with receivers they're capable of running at different ohm loads, but does the same go for speakers? Right now, I have an Onkyo TX-SV727 which isn't even a DD unit (that'll change in a few months) but what I'm wanting to do is to run 2 pairs of front speakers at the same time. As far as I know at this moment (haven't really ever looked) the new receivers don't have outputs for mains 1 and mains 2 to accomplish what I'm wanting to do.
The only way that I know I could run the mains as I'm wanting to with this receiver, I would have to basically take 2 runs of wire to each side, spliced together at the receiver end and clamp them to the R and L binding posts for the mains. That would be putting my RT16's running at 4 ohm (I believe), so would that kill them since they're rated at 8 ohm?
I guess the only other way that I could do what I'm wanting is to get a 2 channel amp and use that to hook up the second pair, but as of this posting, I'm just tryin to see if I can make it work with what I currently have.......
Thanks for the help.......
oh ya.......I tend not to apply practicality to some things(this probably being one of those times), so to those that are gonna ask why I would want 2 pairs of the same speaker up front, I can only say...........because I want to. (shouldn't that be good enough?) :lol: I'm kinda thinking that, given a larger room to work with, that having 4 mains kinda spread across the front of the room that would fill in any potential audio holes that you might have and would widen the sweet spot. Maybe I'm just tryin to justify why it could make sense to have a total of 5 or 6 speakers up front.......(that would be like me) Anyway....thanks again.....
12-17-2002, 03:31 AM
Welcome to the world of dual fronts. I don't think that hooking them up as you described would hurt anything. If there's a switch, put it to 4ohm. If not, I still wouldn't worry too much. It is an Onkyo. I wouldn't crank them full blast and if listening for extended periods feel the amp to see how hot it is.
My receiver has pre-outs for the 2nd room. I connected a 2ch to this and let it rip. Without the amp connected it uses the rear amps and is therefore only good for 2 ch. You might want to consider such option before getting your new receiver. Speaker A+B usually just connects both speakers together giving the 4ohm load you described above.
12-17-2002, 04:03 AM
Thank you for the reply........In all my ramblings I kinda overran my biggest question.......
If I do hook both pairs up as described above, am I going to damage the speakers? I don't know if a speaker that's rated as 8 ohm is going to perform normally at 4ohm with running duplicate fronts.
Will the speakers be ok is my biggest concern..........
12-17-2002, 07:59 AM
I know with receivers they're capable of running at different ohm loads, but does the same go for speakers?
No it does not. The nominal ohm rating is what it is, they method you describe will not change the nominal ohm rating. If you connect 4 speakers as you describe, your receiver will not last long.
12-17-2002, 03:30 PM
Regarding your information Frank....so if I hook up 2 pairs of 8 ohm speakers, i'm not changing the ohm of the speakers, but instead the ohm load of the receiver (i got that part). This is something that I need to learn more about with the purchase of a DD unit in the next few months, but is the Ohm level on the receiver based on what's hooked up to it or to what the receiver is manually set to run at?
I called Onkyo to see what the options were for what I was wanting to do and according to them, essentially there are none. They indicated that I could kill the receiver by going by my intended route. This imparticular receiver does not have an amp pre-out, but does have a set of binding posts for a pair of 2nd zone speakers. My manual mentions nothing about this unit being 4 ohm capable. The lowest I see mention of is 6 ohm
Ultimately though, if running zones 1 and 2 at the same time, zone 1 will only run in 2 channel stereo mode with no surround possible (at least with the receiver that I have). Is it common, or even standard or optional, that a receiver actually has the built in capability of running 2 sets of front speakers at the same time in HT mode? Or would the only way to accomplish that be to purchase an external amp for those 2 channels and run those through the receivers amp pre-out with the other mains running directly from the receiver? (Because I'm not dealing with a digital receiver at this point, I guess I'm not completely clear right now on how plugging in an external amp based on the above scenario would specify my external amp as running 2 additional front speakers, as compared to say surrounds. Maybe it's an amp pre-out front, or amp pre-out center, etc? I dunno......)
I don't know that I would be accomplishing all that much by running dual fronts, but the idea alone is something that makes me wanna try. Like I've said in some of my previous posts, I REALLY like the sound from the RT16's and if there's a possibility that I can expand the soundstage by doubling them up, then I really see no downside. Am I crazy?
12-17-2002, 03:53 PM
So I type up this big post and think that it sounds all intelligent, and then start to research a bit more about my receiver only to find out that it does in fact have a set of amplifier pre outs that I could hook an external amp up to in order to accomplish what I'm wanting.....Few questions about that would be what would be considered a good dependable amp that would work well with my Onkyo receiver. The only thing that somewhat concerns me is that if I do end up going with a different brand down the line, will having an amplifier not matching my Receiver put out a different sound or is all of that controlled by the receivers functions? I imagine that I want to keep the power rating between both the receiver and the external amp as close as possible, so as to not have one set of fronts overpowering the other, true?
I'm still not clear though on the way that a receiver attains it's ohm load rating, be it a manual setting, or on what's hooked up and running off of it. I'm also curious about what others experience or thoughts are on running dual fronts. I suppose that I also need to find out if I'm crazy..... :lol:
12-17-2002, 05:01 PM
If you're happy with the sound of your Onkyo receiver you should look at some Onkyo amps. The sound should be similar but the external amp should sound much better. I don't think it's a good idea to connect both pair of speakers to the L&R outputs because the impedance is likely to drop well below 4 Ohms for certain frequencies. The 8 Ohms rating is nominal. If the speakers have a minimum rating of 6 Ohms, the speakers will need a 3 Ohm load for some frequencies.
Originally posted by Frank Z
If you connect 4 speakers as you describe, your receiver will not last long.
not only that, but I am sure that they will sound like crap
12-17-2002, 07:47 PM
Take a look at this thread it might help a little bit.
Receivers and Amps in general are rated for output INTO a given nominal load (Speaker). The receiver/amp is not rated as a XXohm receiver, instead it is rated for the amount of watts that can be delivered (actually demanded) by a given load. An amp/receiver that is rated at 100 watts into 8 ohms may infact provide 200watts into a 4 ohm speaker, but if the amp/receiver is not designed and/or built for this amount of power it's lifespan will indeed be shortened.
12-17-2002, 07:55 PM
You would essentially be running your speakers in parallel. In parallel, total resistance (or impedance) is going to be less than the individual values. You would be turning your speakers into real current suckers. They'd work your amp really hard as well as sound like crap.
12-17-2002, 08:03 PM
What does nominal mean with regard to ohm ratings?
12-17-2002, 09:39 PM
12-19-2002, 03:51 AM
For DD I wouldn't worry TOO much about matching another amp with your current receiver. It'll only add a tinge of sound difference. Optimally an Onkyo of like model would be great. For stereo, I say go to the extreme. Listen to your receiver for what you like and dislike. Try to pick another amp that offsets this. It's not the replication, so much as the accentuation that make it so appealing to me. Any brand of quality build with the characteristics you're looking for should suffice. I wouldn't worry too much about matching power as I'll assume you have independant volume controls for each. If not then I wouldn't stray more than 30%.
Ohms=resistance. Nominal is average. All speakers have what they call an impedence curve. Lower frequencies usually have less resistance and thus a lower Ohm rating which results in more amperage (amps) for the same amount of voltage. Imagine cutting the end off an extension cord. With the lead separated there is infinate resistance (ohms), connect them with a rusty coat hanger and there might be 30 Ohms resistance (tweeter) and you amp is happy, connect a shorter piece of rusty coat hanger and it might be 4 Ohms. This is getting tougher on your amp and it starts to heat up trying to push out the extra energy (voltage) to compensate. Touch the wire together and there is 0 resistance (Ohms) and your amp fries due to a short.
I hope this helps.
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