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Author Topic: Why is all active speakers underpowered???  (Read 20263 times)

Sean Chen

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Re: Why is all active speakers underpowered???
« Reply #30 on: December 26, 2013, 09:25:24 PM »

hello
Manufacturers of the PA speakers in most cases spec amp to have 2x RMS speaker rating. So, if speaker have 500W amp need to have 1000W. I can confirm that this formula work fantastic and no speaker and amp ever overheating or work with clipping. In this way amp and spekaer work with 50% load. Even for bass you can use 4x RMS rating because peaks. But, 99% active speakers have amps 0.5-1x RMS rating. Why is that??? How large 1kw 18" driver can be driven with 500w-1000w amp? Cant be.

I used to go with this formula, until I started custom building bass guitar cabs. Not many woofers can handle more than its 1x RMS power at bass frequencies without exceeding Xmax, and sound like flutters. Running transducers beyond Xmax can damage woofer physically, while clipping @ the amp or mixer simply sends square wave to transducers and make it heat up quicker - more of a problem for compression driver than woofer. When powered speakers bi-amp the HF and LF separately, clipping @ LF amp won't transfer the clipping to the HF amp section.

Having said that, I don't know which powered speakers uses amplifier w/ power half of woofer's RMS rating. Most of what I came across are 1x to 1.5x (QSC, JBL...).

Now putting my business hat on. A powered speaker with amplifier RMS power 2x that of transducer's RMS rating can end up in transducer premature physical failure (low frequency especially) without user-induced clipping: most likely oem responsibility. On the other hand, a powered speaker with amplifier RMS power 1x to 1.5x that of transducer's RMS rating, if damaged by user's excessive clipping signal inputs: most likely user responsibility.

This I believe is the reason why we don't see powered speaker with amplifier having 2x woofer's RMS rating. Not saying what's right or wrong, just trying to rationalize the situation.

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g'bye, Dick Rees

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Re: Why is all active speakers underpowered???
« Reply #31 on: December 26, 2013, 09:26:53 PM »

Danijel Foler, please excuse these guys. They probably don't realize you are in Croatia.

I wasn't making fun of his command of the English language.  I was making fun of his topic.
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Danijel Foler

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Re: Why is all active speakers underpowered???
« Reply #32 on: December 27, 2013, 09:32:58 AM »

here is one rare example in which amps have 2x rms speaker ratings:
http://www.rcf.it/products/touring-and-theatre/tts56-a

Why I ask question about under powered active speakers? Before some time I have PA for rent, mostly dj playback EDM (techno/trance). Here is picture:



This RCF ESW1018 subs have 600W RMS but crest factor 2.5x, which is 1500W program and 6000W peak (L18S800 driver). My Peavey CS4000 is bridged for two subs and this is clear 1600W per sub 20hz-20khz. I can put this amps to clip and woofer I think can even use 4x RMS power. Never to much woofer excursion, never amp overheating, never into clip of course, all day all night, clean power...

If I have for this subs only 600W RMS, this system cant work to maximum potential and amp will non-stop overworking. Someone have comparison with car. Is it strange that 7.0L V8 in Corvette Z06 can have better mpg than some 1L city car???? No, because V8 will work with 20% instead 100%.

I think that for money I can build better passive system with 2x or more RMS than with active speakers. In this way all components have needed headroom for playback without problems.
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Steve M Smith

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Re: Why is all active speakers underpowered???
« Reply #33 on: December 27, 2013, 11:19:00 AM »

Danijel Foler, please excuse these guys. They probably don't realize you are in Croatia.

Good point.

My friends who have English as a second or third language like to have their mistakes corrected for them so they can learn.

Unfortunately, we didn't do that.

I apologise.


Steve.
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Tim Perry

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Re: Why is all active speakers underpowered???
« Reply #34 on: December 27, 2013, 01:13:30 PM »


I think that for money I can build better passive system with 2x or more RMS than with active speakers. In this way all components have needed headroom for playback without problems.

Given that your comparison is to a box that cost $10,000 to $11,000 USD, I should hope so.
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Lyle Williams

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Re: Why is all active speakers underpowered???
« Reply #35 on: December 27, 2013, 05:48:26 PM »

My experience is at the bottom end of the market.  Down here I think passive+amp sounds better than powered.  The amps in economical powered speakers are spec'd by the guys in marketting not engineering.
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Sean Chen

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Re: Why is all active speakers underpowered???
« Reply #36 on: December 27, 2013, 10:06:19 PM »

Another practice aspect of powered speaker is cooling. Until until recently, powered speakers cannot get too much wattage in the integrated amplifier because there are no huge fans to cool: most of them rely on passive cooling or tiny fans. Passive speakers use racked amplifiers that have much more airflow since noise is not as much a factor - can be stowed away elsewhere.

With Class D amplifiers more prevalent now, powered speakers can pack more wattage without overheating.
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John Roberts {JR}

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Re: Why is all active speakers underpowered???
« Reply #37 on: December 28, 2013, 08:59:01 AM »

Another practice aspect of powered speaker is cooling. Until until recently, powered speakers cannot get too much wattage in the integrated amplifier because there are no huge fans to cool: most of them rely on passive cooling or tiny fans. Passive speakers use racked amplifiers that have much more airflow since noise is not as much a factor - can be stowed away elsewhere.

With Class D amplifiers more prevalent now, powered speakers can pack more wattage without overheating.
While temperature may be a minor consideration the larger benefit from class D and switching supplies is the lower size and weight and more importantly lower cost, at least lower cost for modern class D. Consumers have some difficultly grasping a fair price comparison between powered speakers and passive speakers + amp(s), + crossovers.  Even though the complete package could be a better value it appears to be higher priced than buying passive speakers

JR
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Brad Weber

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Re: Why is all active speakers underpowered???
« Reply #38 on: December 28, 2013, 09:19:17 AM »

Another practice aspect of powered speaker is cooling. Until until recently, powered speakers cannot get too much wattage in the integrated amplifier because there are no huge fans to cool: most of them rely on passive cooling or tiny fans. Passive speakers use racked amplifiers that have much more airflow since noise is not as much a factor - can be stowed away elsewhere.
Which also leads to how cooling, loading, response, etc. of the driver in a particular box can affect the resulting power handling capability and just looking at the woofer driver rating of a powered speaker does not tell the whole story.
 
A powered speaker is typically a system of DSP, amplifier, driver(s), cabinet and sometimes preamp. Manufacturers make decisions in the design of that system to optimize various performance and reliability characteristics.  They may decide to compromise some aspects in order to focus on others.
 
This RCF ESW1018 subs have 600W RMS but crest factor 2.5x, which is 1500W program and 6000W peak (L18S800 driver). My Peavey CS4000 is bridged for two subs and this is clear 1600W per sub 20hz-20khz. I can put this amps to clip and woofer I think can even use 4x RMS power. Never to much woofer excursion, never amp overheating, never into clip of course, all day all night, clean power...
Where did you get those numbers and the 2.5X crest factor for your driver?  Look at the General Specifications in http://www.lautsprechershop.de/pdf/rcf/l18s800.pdf, as far as I can tell the power rating for the driver noted is 700W Continuous and 1400W Program.  They don't identify a Peak rating but I'd assume 2800W.  If the drivers were rated 600W with a 2.5X crest factor then the peak rating would be just 1500W, not 6000W, with probably a 1050W Program rating.  If you want to run 3200W into each sub then go for it, I'm sure your parts supplier will love you.
 
Also look at the response associated with the bare driver and those poiwer ratings.  To get a relatively flat response down to 40 or 50Hz you're apparently looking at the cabinet and processing having to add something like 8 to 10dB of low frequency boost to the driver response.  What might that do to the power the driver can handle?
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Lyle Williams

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Re: Why is all active speakers underpowered???
« Reply #39 on: December 28, 2013, 04:34:22 PM »

Consumers have some difficultly grasping a fair price comparison between powered speakers and passive speakers + amp(s), + crossovers.  Even though the complete package could be a better value it appears to be higher priced than buying passive speakers.

When I buy speakers I go to a store with about $x.  When I listen to $x powered and passive speakers the $x passives sound so much better.

Of course I should be comparing $x passives to $2x powered, but I already have the amp channels.  And I didn't walk into the store planning to spend $2x.  :-)

... but I do hate carrying too much gear at setup/teardown.
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Re: Why is all active speakers underpowered???
« Reply #39 on: December 28, 2013, 04:34:22 PM »


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