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Amp RMS and speaker choice

post #1 of 8
8/13/12 at 4:06pm
Thread Starter 
Hey all!

I will be ordering some new speakers pretty soon for my surround sound I got last year.

I am starting small and just getting a pair of bookshelf speakers for front left and right

All the speakers I am finding in my price range (Sub 130 USD) are only good for 125watts peak.... I have an 80 watt rms amp...

I am really liking the looks of these but I will most likely get them via Bestbuy instead (lower price)

My overall question is this: Will my 80 Watt RMS amp (yes 80 per channel not total) power these speakers safely? or is it too much for them.

You should also know I like my music LOUD... Very loud...

I had a set of 100Watt peak speakers wired in with the fronts (total of 14 ohms) and they would distort at a low volume (well low for me, ~15 - 20 out of 30)

I welcome other speaker suggestions especially if they are cheaper.

Thanks for reading!

-H0tHead132-
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post #2 of 8
8/13/12 at 4:22pm
Amp and speaker ratings are over rated. The standard for both is vague at best. Generally, what destroys speakers is underpowering them with. With a high current amp and desktop/bedroom/dorm setup, generally you'll want to run out of the room or will damage your hearing before the speaker's thermal capacity has been reached. That is, unless you're expecting concert like sound out of Bose or similar satellite speakers.

What amp do you have?

FYI, wiring speakers in series so the total impedance is 14ohms is cutting your amp's power rating @ 8ohm in half. Plus, the crossovers from each speaker will react with each other, creating poor sound. If you want to run multiple pairs of speakers, buy a multi channel amp or receiver.
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post #3 of 8
8/13/12 at 4:44pm
Thread Starter 
Quote:
Originally Posted by Face76 View Post

Amp and speaker ratings are over rated. The standard for both is vague at best. Generally, what destroys speakers is underpowering them with. With a high current amp and desktop/bedroom/dorm setup, generally you'll want to run out of the room or will damage your hearing before the speaker's thermal capacity has been reached. That is, unless you're expecting concert like sound out of Bose or similar satellite speakers.

What amp do you have?

FYI, wiring speakers in series so the total impedance is 14ohms is cutting your amp's power rating @ 8ohm in half. Plus, the crossovers from each speaker will react with each other, creating poor sound. If you want to run multiple pairs of speakers, buy a multi channel amp or receiver.

That is a good thing to know, I knew about the wattage halve but i didn't know the rest...

My amp is a Sony STR-K402 it is advertised as 90watts rms but is rated at 80watts rms
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post #4 of 8
8/14/12 at 7:03am
As Face76 mentioned, under powering is a major cause of damage/low quality sound is under-powering of the speakers. A good rule of thumb I have gone by is to try and make sure I power the speaker with at least 70% of the RMS rating.
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post #5 of 8
8/14/12 at 7:07am
I have some B & W bookshelves that I am sending 100 rms to for each which is "over-powering" but I have them set as "small" and low frequencies sent to sub. your biggest risk for blowing a smaller speaker is from overpowering in frequency ranges that they can't produce well.
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post #6 of 8
8/14/12 at 9:18am
Most class a/b amplifiers (99% of whats available on the market) are about 50% to 60% efficient. Meaning that an amp with 80w per channel will effectively put out 40w to 50w per channel at most. In other words, unless you turn the volume dial 100% you will not damage the speakers.

HOWEVER, the vast majority of damage done to surround speakers is not using crossovers inside the amp to filter out the <120Hz frequencies (like buddy suggested). The other common damage done to all speakers is by turning the volume too high and causing clipping (i.e., sending square clipped waves) to the speakers causing violent movements of the voice coils / motor structures of the speakers.

I like the dealer of those speakers (Parts-express is awesome) although I have never heard them. For that price, here is a diy option that is the best value on the web http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-706 if you feel like using a little glue and elbow grease. I have a pair of these in my computer room and are wonderful speakers and critically acclaimed.
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post #7 of 8
8/14/12 at 1:28pm
Thread Starter 
So pretty much what everyone is telling me is that I worry too much?
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post #8 of 8
8/14/12 at 3:04pm
Quote:
Originally Posted by trulsrohk View Post

I have some B & W bookshelves that I am sending 100 rms to for each which is "over-powering" but I have them set as "small" and low frequencies sent to sub. your biggest risk for blowing a smaller speaker is from overpowering in frequency ranges that they can't produce well.
I had a pair of vintage Tannoys that were only rated for 80 watts but had a 330wpc amp hooked up to them, never had an issue.

Quote:
Originally Posted by Mark the Red View Post

Most class a/b amplifiers (99% of whats available on the market) are about 50% to 60% efficient. Meaning that an amp with 80w per channel will effectively put out 40w to 50w per channel at most. In other words, unless you turn the volume dial 100% you will not damage the speakers.
Yes, A/B amps are not that efficient, but the rest of your info is incorrect. Class D and T are becoming fairly common and are also much more efficient than class A and A/B.

A well designed 80w class A/B amp should put out 80w, but is more wasteful doing so than a Class D or T(@ 90% efficient). For example, a 100w Class A amp will put out 100w, but will draw 400w from the wall to do so, hence the need for large heat sinks.
Quote:
Originally Posted by h0thead132 View Post

So pretty much what everyone is telling me is that I worry too much?
As much as you follow the correct advice in this thread, yes. thumb.gif
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