Choosing the Right Amp


New member
Username: Ryanmaxferreira

Post Number: 1
Registered: Feb-13
Hi all,

I'm new to home audio and I have a very basic understanding of how the whole thing works. I need some help with something and I'm hoping someone can give me some assistance. I have 3 Klipsch 650 outdoor speakers which I want to put on my deck. I also want to add 2 Klipsch outdoor Subs to the set up as well. I believe all these speakers run at 85W and 8ohms. From what I understand I would need an amp capable of pushing 1.5 times the power that the speaker requires and 8 ohms from each channel. So basically 127W at 8 ohms from each channel would be sufficient not to over work the amp.This system is strictly for listening to music so I'm looking for something pretty basic, but where I'm getting a bit confused is the fact that I have 3 speakers I don't want to put 2 on one channel and 1 on the other which would create an unbalanced sound. Thanks.

Gold Member
Username: Hawkbilly

Nova Scotia Canada

Post Number: 1561
Registered: Jul-07
If you were to get a A/V receiver, you could run the 3 speakers as left/centre/right, and the two subs off of the Right and Left line outs (assuming the receiver you purchased had line outs). Any of the reasonable quality receivers would do the trick (Denon & H/K come to mind).

Those speakers are super efficient, so you don't need a lot of power to run them. Anything with decent power supplies will do just fine. You certainly don't need a 100+W amplifier. Something that will produce a decent amount of current (amperage) is more important than the wattage rating, which on many brands of amps & receivers is suspect.

You can spend anywhere from $180 to many thousands of dollars on a receiver or amplifier, depending on how critical you are with the quality of sound. What's your budget ?

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17738
Registered: May-04

Sorry to say, the Klipsch webpages aren't very helpful here. This made me curious enough about this system that I called Klipsch's tech assistance and, even more sorry to say, got even more confused.

According to Klipsch they no longer produce an outdoor subwoofer. The first question then is, do you currently own these two subs? Or, do you know for certain you have access to a pair? If not, most of the questions about the subwoofer can be ignored.

Concerning an amp for the three 650's alone, you can find a few manufacturers selling three channel amps though four, five and six channel amps are more common. These are typically sold for use in a whole house audio distribution system and each channel of the amp would be dedicated to a specific "zone" or room. Certainly, any such amplifier would work for outdoor applications.

Your post, however, raises more questions than it provides answers to satisfy. If you already have a 5.1 HT receiver, you could probably run the outdoor speakers off the outputs of that receiver or another modest HT receiver dedicated to the outdoor system. Most HT receivers have multiple formats for surround sound output which would cover you for any program source you would likely run through the outdoor system. The "five channel surround" format outputs equal volumes to all speakers and could be used to run these outdoor speakers without any real problems beyond the complications of switching the formats back and forth. With a separate HT receiver used for the Klipsch, even that would be a minimal consideration. However, already we have at least two different scenarios for how to make your system work; one receiver running all speakers inside and out or two separate receivers with each dedicated to one "zone". The former requires speaker selector switches and volume controls while the latter does not. For someone not well versed in how to put together a system, this can already be more complicated than you should take on yourself. If you have other speakers in the whole house system that you've not mentioned, then the complications have multiplied.

Who will be doing the wiring and installation of the system? This is unlikely to be a set up you should attempt yourself. There's nothing incredibly complicated about the basic set up you've described but you'll need to make a few decisions about the arrangement of the gear and how to manage the system's flow of signals. I would suggest this is the point where you get a qualified installer involved in the project.

If you already have the subwoofers, this further complicates the system arrangements since the Klipsch webpages are contradictory in how to set up the system. The subwoofer mentioned in the 650's onwer's manual hasn't, according to Klipsch, been produced in six years. The only outdoor sub they offer is not mentioned in the 650's manual and you'll not find it an easy task to make the system work according to either Klipsch's manual or their technical information. To further complicate the set up, the subwoofer is not of the same "electrical sensitivity" as are the 650's. This would suggest you need an amplifier with individual gain (volume) controls to make the sub mate well with the 650's.

Additionally, the on line information regarding a subwoofer states a minimal impedance of 4 Ohms. This will require a fairly stout amplifier if you're going to be driving this outdoors where you lack the indoor's reinforcement of walls, floor and ceiling to contain and add to the overall volume of the system. When I say "stout" I'm not talking about wattage alone. You need an amplifier capable of delivering high amperage (current) into a four Ohm load. THAT would completely alter any suggestion for a HT receiver driving the outdoor system since HT receivers seldom can deal with low impedance loads and many have warnings against use in such systems.

How many reasons is that now why I can't make any recommendation other than you get a qualified installer into the mix to guide you and, more than anything, to take responsibility for making the system operate as you envision?

There's really no need for me to go on here. There are too many plausible system set ups, too many "what if's" and too many unknowns for me to do much more than inform you that your information about wattage is completely wrong. Ignore the "85 watt" figure on the speakers - it means nothing. Literally, it means absolutely nothing. The number you need to look at is the "sensitivity" spec which on the 650's is relatively high. What this number tells you is how much wattage will produce how much sound measured in SPL (sound pressure level) when measured at one meter away from the speaker face. The 650's by themself don't require much in the way of wattage to play rather loud. If these were indoor speakers, you could use a twenty watt amplifier and get very loud levels. As is, these are outdoor speakers and you once again run into the situation where you have no walls, floor or ceiling to add reinforcement to the output of the speakers. Without this reinforcement power requirements go up.

Where ever you found that 1.5 times idea, don't go there again. The person or website that suggested that doesn't have a clue. There's really no reason for me to go through the entire explanation of why that information is bad, just take my word for it, it is. The "sensitivity" spec is what you need to know and it says you don't need much power at all to drive these speakers into making sound. But, since you're outside and there is no reinforcement from surfaces to speak of, you'll need a few more watts than that number would indicate. Since you're going to be seated farther away from the speakers than you would be inside, you'll find that sound looses 6dB every time the distance between the speaker and your ears is doubled. This all gets fairly complex as anyone tries to explain the math of the situation but an installer should be able to sit down with you and come to a conclusion regarding which amp and how much power is appropriate for this system.

Then the elephant in the room is the subwoofer. Subwoofers don't work well outside since there are no reinforcing surfaces to bounce the bass wave. The Klispch tech suggested they had stopped producing any subwoofer meant for outdoor use. That would make sense since most buyers probably weren't very happy with the amount of bass such a "subwoofer" added to their system in such a placement.

Once again this is more complicated than a forum post can cover but I would first suggest you contact Klipsch. If you have the speakers and sub you say you want to hook up, you need some technical assistance - more than can be covered easily in a forum post. Outdoor speakers are never used for much more than background music so the purchase of a high quality amplifier is overkill on these speakers. (The Klipsch tech assistant mentioned Outlaw and Emotiva as possible sources for three channels amps. Apparently, Outlaw no longer produces a three channel amp and both Outlaw and even the Emotiva would be seriously wasted dollars for use with outdoor speakers IMO.) The use of the subwoofers though demands a "stout" amplifier. These objectives are somewhat at odds with each another. You need to sit down with someone and discuss what you think you want against what is actually possible.

My advice, therefore, is to, first, contact Klipsch technical assistance. Second, contact a qualified installer. Third, decide on an acceptable budget for the equipment and the labor of getting everything up and running and then have a long discussion with the installer as to how you can make all of this fit into that dollar amount.

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