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Do I need an amp for these speakers?

 

New member
Username: Jonathanc

Post Number: 1
Registered: Jul-15
Hi - first post, thanks for the help.

I just installed some Bowers and Wilkins CMW7.3 wall speakers. I'm going to play movie and music through them (no surround). I'm worried that my receiver - Yamaha RX-V379 is not going to give me good sound. The receiver is rated for 8 ohms and the speakers are 4 ohms. There is also subwoofer. So two wall speakers and a subwoofer in total.

The receiver lists these specs:

Channel 5.1
Rated Output Power (1kHz, 1ch driven) -
100 W (8 ohms, 0.9% THD)

Rated Output Power -
(20Hz-20kHz, 2ch driven 70 W (8 ohms, 0.09% THD)

Maximum Effective Output Power (1kHz, 1ch driven) (JEITA) -
130 W (8 ohms, 10% THD)

Dynamic Power per Channel-
(8/6/4/2 ohms) 110 / 130 / 160 / 180 W

What do you guys think. I will by a new receiver and amp if I need to.
 

New member
Username: Jonathanc

Post Number: 2
Registered: Jul-15
I'm worried about sound quality mainly - if i crank it up will it still sound good. My other worry is blowing the speakers; say one of my kids messes with the volume knob.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 18061
Registered: May-04
.

In wall speakers tend to limit sound quality. Not always but, "good sound" is subjective. I can't say any more than anyone else can guess what "good sound" quality is for you.

Certainly, if your listening is primarily a matter of movies and videos, then there are few real world situations represented in those sources. That said, most $300 AV receivers are not widely recognized for their fidelity to the source.

Originally, back before home theater, fidelity guided amplifier design and judgement. Today, with few listener's highly familiar with non-amplified music and most preferring movies soundtracks of car wrecks, fidelity is a long forgotten word for the vast majority of listeners. I can't say where you fall in that continuum by reading your post.

I'd somewhat like to know why you bought speakers you feel are not well suited to your receiver. That's a bit like buying a Honda Civic to tow your boat. Maybe, you're simply looking for permission to buy a new receiver?

If you "crank it up" means, what?

If you crank the volume level beyond the limits of the amplifier, then it will distort. Distortion will damage both the speakers and the receiver.

The published specs for your receiver are the typical mish mosh of manufacturer nonsense that says nothing about the ability of the amplifier to drive a real world speaker load.

The speakers are not "4 Ohm" loads throughout their frequency range. The impedance load of a speaker varies with frequency.

The speakers may be higher or lower than the stated four Ohm average at any frequency.

It is the "may be lower" which is typically troubling for a $300 AV receiver. As impedance drops higher current is required according to the rules of Ohms Law.

It's very unlikely your current receiver will be sufficient if you intend to crank up the volume. On paper wattage is not what matters here.

There is no accounting for kids and controls. You have to teach them to respect the equipment.

Where'd you buy the speakers?

I would go back to that retailer and ask for a recommendation regarding a suitable AV receiver. Be prepared to spend an adequate amount since you've chosen more than average difficulty in your speakers.


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Gold Member
Username: Superjazzyjames

Post Number: 2272
Registered: Oct-10
In short JDC, you will probably need a pretty robust amp for speakers with a 4 ohm nominal impedance. Check to see how many ohms your receiver is stable down to. If it's higher than 2, you will definitely need another amp. The impedance of most speakers varies widely across the spectrum and most speakers will get down to about half of their nominal impedance.
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