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Multi-Way Conventional loudspeakers with crossovers

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Old 18th January 2002, 01:42 AM   #1
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Default tri-amping

How do I calculate the SPL that each section of a tri-amped system must produce by itself to achieve optimal power distribution among the 3 sections?
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Old 18th January 2002, 01:45 AM   #2
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Is this for Hifi or Pro Audio / Sound Reinforcement?
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Old 18th January 2002, 01:58 AM   #3
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It's for my big system that I want to build, you know the one. It's for hard rock and heavy metal music, kind of a monster hi-fi thing.

The low crossover frequency will be 300Hz, that part of the system will produce up to almost 144dB. As for the other two parts, that's what I want to figure out, so I know what to do for amps and speakers for mid/high. I plan the upper crossover frequency to be 3000Hz.
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Old 18th January 2002, 03:22 AM   #4
subwo1 is offline subwo1  United States
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Kilowatt, I prefer about 20dB greater capability for bass than for the range above. So if you require 2000 watts, say, for the lows, that would mean 20 watts for the rest. But it doesn't hurt to have reserve capacity either way to avoid clipping and provide a little flexibility. The speaker system plays a role in the determination also.
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Old 18th January 2002, 06:14 AM   #5
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Ok, I guess my question is more like this:
The total dB level shall be 147dB. According to a chart that I saw, with a xover frequency of 300Hz, the SPL should be divided evenly between mid/trebble and bass. So the subwoofers would produce 144dB, or half of 147dB right? The upper xover frequency is 3000Hz, so the SPL should be divided such that the mids produce 35% and the tweeters produce 15%. The subs, of course, produce 50%. 50+35+15=100%. What is 35% and 15% of 147dB? How do I figure it out? These figures are all subject to change, so I need to be able to calculate this stuff.

thanks
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Old 18th January 2002, 07:01 AM   #6
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Half of 147dB SPL is 141dB .... twice that of 144dB SPL is 150dB SPL.... also these should be peak values.... allow @ least 20dB headroom which would mean if the bass was capable of 144dB peak then it should be run @ about no more than 122dB SPL continuous even less in practice this would give about 120-130dB SPL continuous for the system.... and half the total power of the system should be for below 300Hz .....
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Old 18th January 2002, 09:35 AM   #7
CHRIS8 is offline CHRIS8  United States
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And this should make losing 90% of your hearing darn near effortless.

-Chris
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Old 18th January 2002, 10:38 AM   #8
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only 90% ?!?!?
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Old 18th January 2002, 12:05 PM   #9
Geoff is offline Geoff  United Kingdom
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Default Hearing Damage

Quote:

"Temporary reduction of hearing sensitivity, as indicated by the increase of hearing threshold level, occurs after exposure to loud sounds. This can become permanent if the exposure is prolonged. The louder the sound, the shorter the exposure time to produce permanent impairment. Damage is greater if the sound contains impulsive components caused by percussive elements in the source.

Hearing impairment is of a band centred around 4kHz (bark 18 in the cochlea), irrespective of the nature of the sound causing the damage. As damage increases with further exposure, the band broadens, reaching in some cases down to 1kHz.

Exposure levels and times are regulated in industry. Maximum permissible levels are shown in the following chart:

90dBA 8 hours
93dBA 4 hours
96dBA 2 hours
99dBA 1 hour
102dBA 30 mins
105dBA 15mins
108dBA 7.5 mins
111dBA 3.75 mins

It should be noted that with disco music and headphone listening, levels well in excess of 100dBA are possible. The danger is therefore obvious"
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Old 18th January 2002, 12:47 PM   #10
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I was amused reading these theoretical calculations for 140-150 db on bass!
C'mon guys, are we engineering a kind of acoustic weapon to sold to the Pentagon?!

I guess Geoff is completely right in his post, and that, given a defined budget, is much better to invest in quality rather than quantity.

Let's remember that if we talk about music reproduction (if our goal is to realistically reproduce the sound of an F14 taking off from a carrier at 1 mt, of couse the story is different...) it is insane to aim at an SPL higher than, say, 115 db/1mt, and only if we have available a room as big as a castle salon and a listening point of more than 4-5 mt.
Otherwise, apart from ear damage, all the energy that we put in the room will make everything resonate out of control. We'll have a big noise but a very poor music or event reproduction.

Also, talking about acoustic, classical and normal rock music, the lion share of energy distribution is taken by the midrange section, especially the human voice is the 'instrument' who has the higher need of continuous power. Below 150 Hz we don't have that much, and above 4000 the power percentage is negligible (and that is a good thing, this way we can use extremely light tweeter coils)
Of course heavy metal and others 'non natural' (*) sounds (like home theatre special effects) may have an energy distribution more on the bass side.
bye
sandro

(*) I don't mean by that to say that HeavyMetal, rave etc. are not good, just that this music has a different energy balance.
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