Rear speaker power....how much???
06-07-2005 | 01:11 PM
#1
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Joined: Mar 2004
Posts: 1,144
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From: West Springfield, MA
Rear speaker power....how much???
I've heard a lot of people say that the rears are only for "fill". I have a roadster, however, and I've noticed that with the current stock bose system, the rears do add quite a bit of depth with the top down. I don't want to underpower my rears and regret it.
Here are the two amp set-ups I'm considering
1. JL 300/4 amp with 75w going to each front and each rear +
250/1 for the sub
2. JL 500/5 amp which sends 100w to each front but only 25w to each rear
Will 25w to each rear be enough in the roadster with 100w going to the fronts or am I better off in the roadster with equal power to all speakers?
I'm planning on either Boston Acoustics Pro 60 6.5" in front with 5.25" coax in rear or Focal 165KP 6.5" in front with 5.25" coax in rear
Here are the two amp set-ups I'm considering
1. JL 300/4 amp with 75w going to each front and each rear +
250/1 for the sub
2. JL 500/5 amp which sends 100w to each front but only 25w to each rear
Will 25w to each rear be enough in the roadster with 100w going to the fronts or am I better off in the roadster with equal power to all speakers?
I'm planning on either Boston Acoustics Pro 60 6.5" in front with 5.25" coax in rear or Focal 165KP 6.5" in front with 5.25" coax in rear
Last edited by Speedracer; 06-07-2005 at 01:15 PM.
06-07-2005 | 11:54 PM
#2
I have the Focal K2Ps. If you do decide on them, there will be no needs for rear speakers. I also ran the JL 500/5 on my initial system and recomend it. The focal should be able to handle the power the 500/5 sends to the fronts. The difference in sound will be incredible. To hear anything from the back once you have a good set of components, you will have to underive the comps or overdrive the rears and in either case, you will just diminish the sound quality. I learned that the hard way and now have a set of Infiities just sitting in the back unconnceted.
06-08-2005 | 08:42 PM
#4
How loud do you want it? It's simple math.
Take the efficiency of your speakers expressed as dB at 1 watt driven at 1 meter. Let's say that they're fairly average efficient at 90 dB.
First off you're head isn't no where close to being one meter away from the speakers - I'd guess inside of half of that so add 4 dB. That makes you're speakers 94 dB with a one watt amplifer.
Every time you double the power of the amplifier you gain 3 dB more worth of sound.
1W=94dB
2W=97dB
4W=100dB
8W=103dB
16W=106dB
32W=109dB
64W=112dB
128W=115dB
256W=118dB
512W=121dB
1024=124dB
So notice that the first very few watts are very efficient and get you lots more sound pressure levels. Second the best way to get loud is to have an efficient set of speakers. It's a heck of a lot cheaper to get speakers 4-5dB louder rather than to up grade from a 120w/ch. amplifer to a 480w/ch. amplifier. Third notice that the difference between a 100, 120, and 150 W amplifiers doesn't make for that much more music. Finally each speaker driven with this wattage adds to the sound level - two speakers driven +3dB.
The smallest amount of difference the typical guy can hear is about 2 dB. An average dance club will reach 110-115dB levels (see chart below).
Here are the OSHA guidelines for sound exposure:
90 dbA 8 hrs
92 dbA 6 hrs
95 dbA 4 hrs
97 dbA 3 hrs
100 dbA 2 hrs
102 dbA 1.5 hrs
105 dbA 1 hr
110 dbA 0.5 hr
115 dbA 0.25 hr or less
So looking between chart one and two - a fifty watt amp cranked up should be listened to for about a half an hour to bit more. Note that many say that the OSHA numbers are too high - the EU has lower volume requirements.
Now, just because you only plan on listening to music at low (sane) levels of 90-100 dB doesn't mean that a large and powerful amplifier will not benefit the quality of the sound. A larger amplifier will have the power reserves to reach for transcients. They'll also typically have a higher dampening factor. Both of these mean more accurate music.
I have suffered from tinnitus for about 20 years from exposure to fighter jets on a Navy aircraft carrier and it sucks. 
Take the efficiency of your speakers expressed as dB at 1 watt driven at 1 meter. Let's say that they're fairly average efficient at 90 dB.
First off you're head isn't no where close to being one meter away from the speakers - I'd guess inside of half of that so add 4 dB. That makes you're speakers 94 dB with a one watt amplifer.
Every time you double the power of the amplifier you gain 3 dB more worth of sound.
1W=94dB
2W=97dB
4W=100dB
8W=103dB
16W=106dB
32W=109dB
64W=112dB
128W=115dB
256W=118dB
512W=121dB
1024=124dB
So notice that the first very few watts are very efficient and get you lots more sound pressure levels. Second the best way to get loud is to have an efficient set of speakers. It's a heck of a lot cheaper to get speakers 4-5dB louder rather than to up grade from a 120w/ch. amplifer to a 480w/ch. amplifier. Third notice that the difference between a 100, 120, and 150 W amplifiers doesn't make for that much more music. Finally each speaker driven with this wattage adds to the sound level - two speakers driven +3dB.
The smallest amount of difference the typical guy can hear is about 2 dB. An average dance club will reach 110-115dB levels (see chart below).
Here are the OSHA guidelines for sound exposure:
90 dbA 8 hrs
92 dbA 6 hrs
95 dbA 4 hrs
97 dbA 3 hrs
100 dbA 2 hrs
102 dbA 1.5 hrs
105 dbA 1 hr
110 dbA 0.5 hr
115 dbA 0.25 hr or less
So looking between chart one and two - a fifty watt amp cranked up should be listened to for about a half an hour to bit more. Note that many say that the OSHA numbers are too high - the EU has lower volume requirements.
Now, just because you only plan on listening to music at low (sane) levels of 90-100 dB doesn't mean that a large and powerful amplifier will not benefit the quality of the sound. A larger amplifier will have the power reserves to reach for transcients. They'll also typically have a higher dampening factor. Both of these mean more accurate music.
Two types of hearing damage can result from exposure to loud noise: sensineural hearing loss and tinnitus. Sensorineural hearing loss happens in the inner ear when high energy sound waves, rippling through ear fluid, overstimulate and kill hair cells. When hair cells for a band of frequencies are destroyed, those frequencies are no longer heard. In addition to being at the frontline of the cochleal sensor array, the high frequency hair cells are also the most sensitive. It is not surprising, then, that noise-induced hearing loss typically begins with the high frequencies in the 3kHz-6kHz range. Cochlear implants may improve hearing function in those cases, where the auditory nerve cells (that connect to the hair cells) are still intact.
If loud noise only damages the hair cells beyond their capacity to heal completely, then either hearing at certain frequencies will be diminished and/or the listener will suffer tinnitus, when the damaged cells fire continuously even though there is no real sound. Tinnitus is typically described as a persistent, loud buzz in the head at the frequency of the hearing damage. For some tinnitus sufferers, the buzz is very loud - 90dB or more - and can compromise the quality of life, not to mention completely ruin all ability to enjoy music. Diminished hearing can be corrected to a degree with hearing aids. Tinnitus is currently not curable, but there are treatments and devices to minimize its impact on the sufferer.
If loud noise only damages the hair cells beyond their capacity to heal completely, then either hearing at certain frequencies will be diminished and/or the listener will suffer tinnitus, when the damaged cells fire continuously even though there is no real sound. Tinnitus is typically described as a persistent, loud buzz in the head at the frequency of the hearing damage. For some tinnitus sufferers, the buzz is very loud - 90dB or more - and can compromise the quality of life, not to mention completely ruin all ability to enjoy music. Diminished hearing can be corrected to a degree with hearing aids. Tinnitus is currently not curable, but there are treatments and devices to minimize its impact on the sufferer.
06-09-2005 | 09:30 AM
#5
Thread Starter
Registered User
Joined: Mar 2004
Posts: 1,144
Likes: 1
From: West Springfield, MA
Originally Posted by Paul350Z
How loud do you want it? It's simple math.
Take the efficiency of your speakers expressed as dB at 1 watt driven at 1 meter. Let's say that they're fairly average efficient at 90 dB.
First off you're head isn't no where close to being one meter away from the speakers - I'd guess inside of half of that so add 4 dB. That makes you're speakers 94 dB with a one watt amplifer.
Every time you double the power of the amplifier you gain 3 dB more worth of sound.
1W=94dB
2W=97dB
4W=100dB
8W=103dB
16W=106dB
32W=109dB
64W=112dB
128W=115dB
256W=118dB
512W=121dB
1024=124dB
So notice that the first very few watts are very efficient and get you lots more sound pressure levels. Second the best way to get loud is to have an efficient set of speakers. It's a heck of a lot cheaper to get speakers 4-5dB louder rather than to up grade from a 120w/ch. amplifer to a 480w/ch. amplifier. Third notice that the difference between a 100, 120, and 150 W amplifiers doesn't make for that much more music. Finally each speaker driven with this wattage adds to the sound level - two speakers driven +3dB.
The smallest amount of difference the typical guy can hear is about 2 dB. An average dance club will reach 110-115dB levels (see chart below).
Here are the OSHA guidelines for sound exposure:
90 dbA 8 hrs
92 dbA 6 hrs
95 dbA 4 hrs
97 dbA 3 hrs
100 dbA 2 hrs
102 dbA 1.5 hrs
105 dbA 1 hr
110 dbA 0.5 hr
115 dbA 0.25 hr or less
So looking between chart one and two - a fifty watt amp cranked up should be listened to for about a half an hour to bit more. Note that many say that the OSHA numbers are too high - the EU has lower volume requirements.
Now, just because you only plan on listening to music at low (sane) levels of 90-100 dB doesn't mean that a large and powerful amplifier will not benefit the quality of the sound. A larger amplifier will have the power reserves to reach for transcients. They'll also typically have a higher dampening factor. Both of these mean more accurate music.
I have suffered from tinnitus for about 20 years from exposure to fighter jets on a Navy aircraft carrier and it sucks.
Take the efficiency of your speakers expressed as dB at 1 watt driven at 1 meter. Let's say that they're fairly average efficient at 90 dB.
First off you're head isn't no where close to being one meter away from the speakers - I'd guess inside of half of that so add 4 dB. That makes you're speakers 94 dB with a one watt amplifer.
Every time you double the power of the amplifier you gain 3 dB more worth of sound.
1W=94dB
2W=97dB
4W=100dB
8W=103dB
16W=106dB
32W=109dB
64W=112dB
128W=115dB
256W=118dB
512W=121dB
1024=124dB
So notice that the first very few watts are very efficient and get you lots more sound pressure levels. Second the best way to get loud is to have an efficient set of speakers. It's a heck of a lot cheaper to get speakers 4-5dB louder rather than to up grade from a 120w/ch. amplifer to a 480w/ch. amplifier. Third notice that the difference between a 100, 120, and 150 W amplifiers doesn't make for that much more music. Finally each speaker driven with this wattage adds to the sound level - two speakers driven +3dB.
The smallest amount of difference the typical guy can hear is about 2 dB. An average dance club will reach 110-115dB levels (see chart below).
Here are the OSHA guidelines for sound exposure:
90 dbA 8 hrs
92 dbA 6 hrs
95 dbA 4 hrs
97 dbA 3 hrs
100 dbA 2 hrs
102 dbA 1.5 hrs
105 dbA 1 hr
110 dbA 0.5 hr
115 dbA 0.25 hr or less
So looking between chart one and two - a fifty watt amp cranked up should be listened to for about a half an hour to bit more. Note that many say that the OSHA numbers are too high - the EU has lower volume requirements.
Now, just because you only plan on listening to music at low (sane) levels of 90-100 dB doesn't mean that a large and powerful amplifier will not benefit the quality of the sound. A larger amplifier will have the power reserves to reach for transcients. They'll also typically have a higher dampening factor. Both of these mean more accurate music.
I have suffered from tinnitus for about 20 years from exposure to fighter jets on a Navy aircraft carrier and it sucks.
I think I am going to end up going wit the 75watt x 4amp. The headroom and steady state power levels for listening won't be that much different between 75w in the 300/4 amp vs. 100w in the 500/5 amp, but the 75w going to the rears in the 300/4 will give me more room to play with here.
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