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Old 9th March 2012, 10:12 PM   #1
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Default Speaker power rating vs amplifier rating

How do you determine how much power you can drive into a speaker based off manufacture power rating?

For example, I plan to get 4 of these + a horn tweeter for a center channel I will build:

HiVi F5 5" Bass/Midrange 297-435

Which has a power rating of only 35 watts rms, but I will be driving it with a QSC 850 bridged which has a power rating of 400W into 8 ohm.

Obviously I can protect the speaker by only having the amp up slightly but I do want to run my system very loud, theater right.

If I plan to wire 2 in series and and then those 2 in parallel, then the 8 ohm horn in parallel, how do I determine how much power I can pump into the set of speakers without blowing them? What is the proper procedure here?
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Old 9th March 2012, 10:29 PM   #2
sreten is offline sreten  United Kingdom
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Hi,

Basically you can't. You can say with 140W total continuous thermal
power rating with music programme at clipping levels the speaker
will be fine in the midrange with a 400W amplifier.

What you can't say though is that your speakers won't excursion
limit in the bass end with far less than 140W drive, they will, and
the power handling will actually be based on the high pass filtering.

rgds, sreten.
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Old 9th March 2012, 10:53 PM   #3
a.wayne is offline a.wayne  United States
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Both amp and speaker will have some thermal distortion, i like big coils for woofers, 3-4 inch at least for high power applications ..
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Old 9th March 2012, 10:53 PM   #4
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As far as power rating, what exactly blows a speaker? When the amplifier tries to drive it beyond xmax?
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Old 9th March 2012, 10:54 PM   #5
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Quote:
Originally Posted by a.wayne View Post
Both amp and speaker will have some thermal distortion, i like big coils for woofers, 3-4 inch at least for high power applications ..
Sorry do you mind explaining what that means? I'm new to diy.
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Old 9th March 2012, 11:00 PM   #6
CBS240 is offline CBS240  United States
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Depending on brand, I generally recomend not to exceed 60% of rated RMS power of the speaker.
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Old 10th March 2012, 12:23 AM   #7
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by Fusion916 View Post
As far as power rating, what exactly blows a speaker?
When the amplifier tries to drive it beyond xmax?
Hi,

Most drivers sound horrible driven full range well before you
get anywhere near their themal ratings. Drunken parties
are a well known tweeter (and amplifier) friers.

Modern drivers are very resilient if you use your ears.

HiFi is not car audio and you can't match driver and amplifier
power ratings. Many quality hifi speakers can handle 1KW
transients but would also die with 100W continuous RMS.

Fact is with a 100W amplifier mildy clipping the average
power is much less than 10W, it doesn't fry drivers.

Small amplifiers fry tweeters when excessively overdriven
and big amplifiers can and do fry bass units at silly levels.

At any reasonable high levels your drivers will be fine.

rgds, sreten.

FWIW the actual plan for a centre doesn't seem a good idea.
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Old 10th March 2012, 01:33 AM   #8
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Quote:
Originally Posted by sreten View Post
Hi,

Most drivers sound horrible driven full range well before you
get anywhere near their themal ratings. Drunken parties
are a well known tweeter (and amplifier) friers.

Modern drivers are very resilient if you use your ears.

HiFi is not car audio and you can't match driver and amplifier
power ratings. Many quality hifi speakers can handle 1KW
transients but would also die with 100W continuous RMS.

Fact is with a 100W amplifier mildy clipping the average
power is much less than 10W, it doesn't fry drivers.

Small amplifiers fry tweeters when excessively overdriven
and big amplifiers can and do fry bass units at silly levels.

At any reasonable high levels your drivers will be fine.

rgds, sreten.

FWIW the actual plan for a centre doesn't seem a good idea.
Hmm, I was hoping there was some calculations or something I can use but that doesn't seem to be the case.

And what is wrong with my driver selection?
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Old 10th March 2012, 09:33 AM   #9
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by Fusion916 View Post
And what is wrong with my driver selection?
Hi,

With 4 drivers flanking a horn you'll get horizontal lobing issues.

rgds, sreten.
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