Blown Speaker

I recently added Energy CF-50 towers to my system. My other equipment includes Definitive Technology C/L/R 2002 center and SM 350 bookshelf speakers for the surrounds, all powered by a Denon AVR-1912. I'm concerned that I may be underpowering my speakers, because within the first two weeks, the left speaker blew out. Luckily, I was able to exchange the blown speaker, but my question is, should I upgrade to a more-powerful receiver?

Dan Marchio

It's interesting—and insightful—that you would think underpowering your speakers might cause a blowout. Most people would think that overpowering a speaker might cause damage—and it can—but so can underpowering if you like to play it loud. If you limit the volume so it always sounds clean, you shouldn't have a problem, but if you drive the amp near its limit, it could go into clipping, and the resulting distortion can cause the speaker—especially the tweeter—to overheat and fail.

Another potential issue arises from mating low-impedance speakers to an amp that is not designed for them, but I don't think this is the problem in your case. Let's take a look at the specs—the Energy CF-50 is specified with a nominal impedance of 8 ohms and a minimum impedance of 4 ohms, while both Definitive models are spec'd to be "8-ohm compatible," which I assume means they have a nominal impedance of 8 ohms; I don't know their minimum impedance. The CF-50 and C/L/R 2002 can handle power from 20 to 250W, while the SM 350 can handle 20 to 200W.

The Denon AVR-1912 is spec'd to output 90 watts per channel into 8 ohms with "low-impedance drive capability." However, the manual says the speakers must have an impedance from 6 to 16 ohms, which I assume refers to the nominal impedance, and 6 ohms isn't all that low. Still, taking all these numbers into account, I think the Denon should have no trouble with the impedance of your speakers.

On the other hand, 90 watts is kinda wimpy for these speakers, which would probably be happier with 200 watts than with 90, especially if you like to crank the volume. So yes, I think a more powerful AVR is warranted in your case. You don't say if you have a powered subwoofer, but that can also reduce the workload of the AVR if you redirect the low frequencies in the main channels to the sub.

I'm also concerned that you are mixing Energy and Definitive speakers in the same system. I always strongly recommend that all speakers in a surround system come from the same manufacturer to maintain a consistent tonal balance. Unless you really like the sound of your current system, I'd return or sell the Energys and get two more C/L/R 2002s for the front left and right, which would give you three identical speakers across the front. Alternatively, a pair of Definitive towers would also work very well with the rest of your speakers.

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jnemesh's picture

Dan (and Home Theater Magazine!) should also realize that wattage ratings are EXTREMELY distorted! Also, saying the AVR has a rating of 90 Watts tells you absolutely nothing. To get a TRUE measure of available power, you also need to know what frequency range it is tested at and also the number of channels driven. You also need to know how much total harmonic distortion is present (THD) at the measured output. (roughly 0.1% THD is where the distortion becomes audible)

For example, lets look at the AVR1612 (I picked this one because HT Mag has a review on this model). Denon's website puts the 1612's output at 75 Watts/channel, with all 5 channels driven, with 0.08% THD. Home Theater Mag reviewed this unit and found that with all 5 channels driven, you get 71.5 watts at .1% THD and 79.8 watts at 1% Denon's specs are pretty close to what you get in the real world. Other companies aren't so truthful. Lets take a look at another example, the Onkyo TX-NR609...

The BOX says 125 watts...but if you look at the website, you see each PAIR of channels rated separately. The front left and right channels are listed as follows: 100 W + 100 W (8 ohms, 20 Hz-20 kHz,0.08%, 2 channels driven, FTC)125 W + 125 W (6 ohms,1kHz,0.1%,2 channels driven, FTC).

So here, you can see that if you are only powering TWO speakers, AND the speakers are 6 ohm nominal impedance, you will get 125 watts per channel before you start to hear distortion. However, if you look at Home Theater Mag's review, when you drive 7 speakers at the same time, this unit only puts out 77.7 watts per channel before you hit 0.1% distortion! So, while it may seem like you are buying a more powerful amp than your AVR 1912, in reality, the power is about the same as what you have!

Finally, NOTHING in the specs will EVER tell you how the thing actually sounds! You really need to listen to the AVR before making a purchase! I have seen plenty of cases where a lower powered (or lower priced) AVR sounds SIGNIFICANTLY better than the higher powered one. (try listening to a Marantz vs. the Denon!)
I hope this information helps you on your quest...good luck, and have fun!

Scott Wilkinson's picture
AVR and amplifier power ratings are often meaningless, but not always, as in the case of Denon. And of course, specs say nothing about how a product sounds. In my response here, however, I was only addressing the question of whether or not the AVR is powerful enough for the speakers, and the spec'd power provides a general idea, which is good enough in this case. Of course, the best way to know what's really going on is to read HT's reviews and, especially, our measurements.
albert26's picture

please ,,your'e last statement is correctly overdue,,,,
Not sure where the other Amatauer comments are coming from.
I have owned multiple pre-pro's & AVR's,,,,again ,not in every person's
budget , But ,certainly we can all hear the difference between a Pre-Amp section of the AVR ,,we hope.,,listen for pure A/V sounddddd.
Put a Yamaha or Denon ,against something awesome,but more $$$$$$$$.
Watts per channel ,have never been accurate since the 50's. Get off it.
Good luck kids

shiitaki's picture

I have Def Tech and am happy with them. They do have limits, and while I agree that the baby Denon may not be as robust as it's bigger brothers, the speakers won't take big power anyway. If you have reasonable expectations, and a reasonably sized room, I would suspect the issue is that the crossover was set wrong, damaging the speaker with too much power at too low a frequency, causing physical damage by the cone bashing it self against the physical limits of the speaker frame and suspension. The picture illustrates this, a amp that is clipping would destroy the tweeter because the corners of square waves go right through the crossover. A speakers ability to covert electricity to sound pressure goes down as the frequency goes lower. The crossover should be set at 80 hz, even for a 'tower speaker', unless it has a sub amp built in. The Denon doesn't have a amp section to push a real sub, and those towers don't have a real sub anyway. My Denon loves to set my crossovers to low, I have to go back and manually set them up to where they belong. A speaker may be able to go down low at 75 db, but will rip itself apart at 90db. If you are going to play at theater levels, then using something as high as 120hz may be needed in a big room.

albert26's picture

I think this person is tonally def , or needs help.
Create your own personall Crossover, to your'e Human ear!
Good Luck

Tucker1011's picture

He was talking about the crossover in the receiver. He's recommending against feeding moderate speakers the full frequency range to help reduce the possibility of damage. This comment clearly assumes the presence of a subwoofer.

It may not have been the most cohesive comment, but the core content was just fine. Besides, it's not like you're in a position anyway - Mr. Business Man.

P.S. I apologize to the gods of HomeTheater; this tone-deaf comment just irked me something fierce.

albert26's picture

Positivley , you need more power,if its in your'e budget,look at a Denon
AVR3312,,with pre-outs ,,& create your Own Sound,,in reality of adding
seperate Power amps,choose what you like ,,,,down the road Sir.