Receiver Capable of Handling 4 Ohms

THX labelled AVRs can do it. For < $600 you have to look at the refurbished/used market. Onkyo 805 is a THX AVR and I believe you can find it for under $600 online.

If an AVR handles 4 ohms then it definitely handles 8 ohms. You should be aware that the impedance value isnt just a specific value, its actually a curve and speakers can have 4 ohm impedance at one frequency and 10 ohms at another frequency.

very few receivers I have seen are specifically rated for 4 ohms. Some people have used 4 ohm speakers with receivers successfully.

If it's only the front 3 speakers, that helps.

At moderate volumes, my guess is the 765 will run ok with 4 ohm speakers. At high volumes it could overheat and it's internal protection would then hopefully kick in and shut it down.

When you use 4 ohm speakers, more current will flow. You need to ensure plenty of air space for ventilation.

8 ohms is easier to drive than 4 ohms, so no worries there.

If a receiver can handle 4 ohms it will handle 8 ohm speakers easily. The 4 ohm speakers are much harder to drive than 8 ohms. What speakers are these? Also how large an area are you putting this setup in? I would think that the 765 could handle 4 ohms, but I would look at something else as Yamah did drop their specs on this years offerings. If you look at their website and pull up the specs for this AVR it will give you the ratings for this receivers capabilities. Also there may be a full test report on it at Audioholics.com. Check out that site and see if there is. I would look for something that has a THX certification. The Onkyo 707/807 have these and should drive 4 ohms okay. The Denon don't have the certification but do usually come close to their specs. H/K is also known for either meeting their specs and in some cases surpassing them. Good luck and hope this helps in some way. Also give the Pioneer Elites a look. The 21/23 will have THX certification also.

would you consider a separate amp to power those ML Encores properly?

Get the speakers you want. You'll be unhappy for settling for something less in the long run. Step down on your receiver to one that has preouts (665) and then save for an Emotiva upa5/7 or even an XPA3/5. Let the AVR do the surround work. The fronts are by far the most important part of the setup. Nice choice on the speakers. Keep and build from there. Go to Emotiva website and check out the above mentioned amps and see if any are on sale now. Any of them should drive those speakers IMO.

For $80 over your budget you could look at an Onkyo TX-SR707. Onkyo certifies it for 4 ohm performance.


I know that is or used to be part of the spec. But.....the Onkyo 608, which is THX Select 2 certified doesn't appear to be rated for 4 ohm operation. On this page you'll see that "4 ohm performance" is not checked and here the speaker impedance is listed as 6 to 16 ohms.

The amp would connect to the pre-outs on your receiver and then you would connect your speakers to the amp. Really simple to do. That's why I suggested the Yamaha 665 and an Emotiva amp. The 665/765 doesn't have enough power to drive the speakers of your choice like they need. The AVR + amp combo would do it easliy. Check out the link below to get an idea on the price of highly recommended amps from Emotiva.

http://emotiva.com/xpa3.shtm


Also look at the prices for the UPA series there.

The 765 actually cost less than the 665 when discounted on Saturday's at Newegg.com.

Then do as suggested by someone else and look at the Onkyo 707 for now. Later if you feel you need more power still, then consider adding amps. The 707 should power those speakers okay. But I still say if those are the speakers you want, get them, they are the most important part of your system. The 707 is a very good AVR for the money. Check them out at Newegg. There are also refurbs at accessories4less you should consider. The 876 is there and I know it will power those speakers easily.

Here's the 707 from Newegg.

http://www.newegg.com/Product/Produc...82E16882120135

Yamaha AVRs run very cool to start with - so long as you don't block the ventilation, they will work fine.

Denons, on the other hand, run very hot to start with and I wouldn't push them.

Not to go off topic here, but what Yamaha are you using that runs cool. I've used many Yamaha with plenty of ventilation and they all ran pretty damn warm to even hot. The Yamaha 2600 I replaced with the Onkyo 876 ran a lot hotter than the the 876 is running and Onkyo's have a history of running hot. Just a question and not a dispute by any means.

thx,
I guess that is the Select 2 certification...I honestly don't follow THX that well, I did think it was 4 ohm certified at one time. Oh well.

707 would be beefy enough for him. I still think something like the 805 offers maybe more at a lower cost (if he can find one).

Yes.

This depends on what you want.

Pro amps are higher powered, low cost choices but they are a little uglier so you are not going to have an audiophile look if you like to look at gear.

You can then not worry about your mains and get a lower cost AVR like the Yahama series that has pre-outs to connect to separate amps.

The entire RX-Vx6x series which has been referenced in this thread runs almost cold to the touch and runs 4-ohm speakers without issue.

Note: leave the AVR switch at 8-ohms or else you reduce the available output power.

There's a lot that goes into the amount of heat a receiver generates. I will list the ones I think are important, but I should mention I am not an engineer -

* High power ICs; CPUs, DSPs, Video processors, etc. all generate heat - I suspect this is why receivers have gotten so hot, because of all the ICs being added for new features
* Bias; The output transistors can be biased in class A to varying degrees. This increases radiated heat as far as I know
* Transformer; A lot of current can flow through a transformer, this will generate heat
* Power transistors; Regardless of bias, these will convert a certain amount of electrical energy into heat; 7.1 receivers have at least 7 of these.

MaxJean, you just posted in the speaker forum and I just clued into the fact that you have not purchased the MLs.

If $$$ are an issue maybe you should consider front speakers that are easier to drive?

The Onkyo 703 and the 707 will not drive vintage nominal 4 ohm Infinities to moderately high levels (100 db peaks on orchestral music) without shutting down. Using the 4 ohm setting on the 703 reduces output by ~ 6 db and it will still go into protect mode if driven hard. It depends on how far below 4 ohms the speaker drops and how flat the impedance curve is.

I have not tried the 4 ohm setting on the 707.

Thank you good to know. Also look at this years offerings from Yamaha as compared to previous models. There seems to have been a pretty big drop in amps,power supply, and to me quality build that Yamaha was known for. What are they making now that compares to the 1900/3900 or even the 863? Maybe the 1065/2065 will but again to me the build quality is not there. I'm a huge Yamaha AVR fan and usually recommended them first, but not this year. Glad to hear the x65 series do run cooler though.

Onecall.com has the TX-SR707 under your budget, you can probably even offer a tiny bit less with their "my price" option.

While the impedance is a factor, the sensitivity (efficiency) of the speaker is the largest factor in getting adequate SPLs.

What is the sensitivity of your Infinitys?