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#769 03/11/01 06:21 PM
Joined: Oct 2000
Posts: 2,723
Likes: 1
Broom Pusher and
Member
66'
Your in a band, huh? That's cool.
I play drums. Been playing on and off for about 12 years. Been in a few bands [nothing serious, just jam sessions].
I also was a drum Tech for an old friend. Worked quite a few gigs in Hollywood, but a lot of local shows. Learned a lot of stuff from other bands, too.

Did maintenance stuff on the rest of the band's equipment [fix cords, change out pickups, etc.].

Anyhow, the 8 amps load sounds about right for a high level of sound from all equipment.
You most likely measured this in your studio, where everything is somewhat close together.
The Bass guitar's amp will draw the most power at one instance, but not continuous. If your Bass player was doing a hammer-on, or maybe arpeggio in an octave that's resonant with the amp, that will draw a steady power. Same with guitars, but not as high of power as the Bass amp [it needs high power to move the air at low frequencies, such as the first 3 audiable octaves [20-63, 63-125, 125-250 Hz] and a few subsonic octaves [below 20 Hz].

The thing about Audio power [as to the power amplifier] is that when you effectively double the perceved sound [sounds twice as loud after turning the volume pot], the power required to do this increases 10x. So if you had the level [volume] set so the speakers put out an overall sound level that is like normal conversation [around 50 dB] and the amp puts 1 watt RMS of power [for example] into the speakers [would also draw 1 watt from power supply - not including preamp load efficency], when you increased the level to make the sound from the speakers "seem" twice as loud, the output power pushed into the speakers from the amp [and also drawn from the power supply] increases 10 times - from 1 watt to 10 watts. Each increase from there will continue the same [doubling the sound from the 10 watt point will require 100 watts].
It's a logarithm figure. This is why sound loudness is measured in dB [deciBells].

You might have replaced a volume pot on some piece of audio equipment [volume pot is the volume dial - pot is short for Potentiometer]. You als might have noticed that any old pot won't work and that you need to use a pot with an Audio Taper, as opposed to a Linear Taper. A Linear Taper pot will increase, or decrease the resistance level in an equal and uniform fashion while the shaft is turned. If you measured the R from one end to the center tap while turning the shaft, the R will change evenly with the turning of the shaft.
An Audio Taper pot is designed to corespond with the way people perceive an increase - or decrease - in the loudness of sound. There is a non uniform increase - or decrease - in R when the shaft is turned, quite different from the Linear Taper pot. Even though this non-uniform change seems like it would definitely be wrong and sound weird, it sounds just like it should! Turning the pot to a position that increases the loudness twice as loud as before will result in a drop of R in the pot 10 times lower than the previous setting.

As to the power amp being fried, I can only say that Peavy amps seem to fry power amp ICs [chips] at the most oddest times.
Maybe if the speaker boxes / cabinets have crossovers in them, they were allowing high power to be drawn constantly through the filter and around the speaker.
16 Guage wire, even at 100 feet, will be OK with a power level no more than 25 watts continuous, 50 watts instant.
Were the cables getting warm??
I could go on for ever on this stuff, so post a little more info and I'll continue from there.

Steve [sparky],

I have seen some of the PC speakers with the built in power amps, being rated at some bizzare power level - like 200 watts! They did include in very small print the disclamer to this, which stated it was Peak-to-Peak power at 250 hz into a 2 ohm load.
This is no lie, but it's misleading! It can put this much instantanious power into a 2 ohm speaker at 250 Hz for about 0.00534 seconds. Similar to the 4HP motor!!
Just can't see how they can legally advertise this [Linked Image]

A visual way to judge a speaker's power handling capability is to see how wide the voice coil is. Voice coil is visable at the front of a speaker - it's the round part at the center of the cone. With horn tweeters, it would be the center part of the driver.
On woofers, a 1-1/4" voice coil could handle no more than 75 watts. A 3" voice coil could handle no more than 350 watts.

The speaker's Impedance is something that is not a steady level over the frequecy spectrum, so it might be very high at one frequency, nominal at resonant frequency, then lower at another frequency.

High quality and custom built crossover networks incorporate Impedance equalizers with the Xover filters to help with this Z swing and try to keep the input Z level that the power amp sees, somewhat constant.

Higher Z speakers have lower loading, but require the amp to push the current at higher voltages. High Z coils are good for midrange and tweeter speakers, but not too helpful with low power levels.
Low Z coils are nice for woofers, but the same applies.
When using multi driver setups on speaker boxes, like 2 way and 3 way speakers, it's best to have all the voice coils' Z to match each other. The crossover, if designed properly, will appear as one Z level, close to the rating of one coil's Z, as far as the amp is seeing.

When the amplifier has low power output and is "cranked" [volume at highest], outside of the crappy sound made, the tweeters are in danger of being fried. At this level, the amp produces little low and mid range power, but plenty of high Hz power and voltage.

On the other hand, High power amps rattle the heck out of woofers until they get extended beyond their capability - this makes them sound like crap! If the voice coil cannot handle the power and is run for an extended period of time, this fries the voice coil.

This is a fun subject!! glad it came up.

Scott SET


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
#770 03/11/01 08:40 PM
Joined: Nov 2000
Posts: 2,236
Likes: 1
Member
Yep...it was a Peavey...can't remember which model and I may have the numbers wrong, but we refer to it as the "boat anchor"...And indeed there are X-overs in the monitors.

I'm the bass player and I haven't figured out the slap-n-pop thing yet. I rarely have the volume (gain?) pot over 50%, and then it shakes your insides...(Cool!)

Go to: http://www.kellyelectric.electrical-contractor.net/Fat%20Heads/Fat%20Heads.html

for more on my band "Fat Headed Monster"


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI
#771 03/11/01 09:12 PM
Joined: Oct 2000
Posts: 5,392
S
Member
a six stringer! and fretless! wow!...I was a bass player, still got that ol' Sun tube head around, peavy 4 banger bass...

check out Stu Hamm's slap tap & pop video, he's the man.

I always liked doin' that tune by the wicked Mr. Picket... [Linked Image]

[Linked Image]

#772 03/12/01 02:22 AM
Joined: Oct 2000
Posts: 2,723
Likes: 1
Broom Pusher and
Member
That's cool there is a few musicians in this forum!

Now there is a real variety of stuff going on here!!

Hey Steve, do ya still play?

Scott SET


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
#773 03/12/01 07:40 AM
Joined: Oct 2000
Posts: 5,392
S
Member
only to the radio...bands are a time committment, and my kids take most my time , i have a 6 string ovation...i do sesame street tunes for my 3 yr old. I do some Bert & Ernie cover tunes.. [Linked Image] [Linked Image] [Linked Image]

#774 03/12/01 09:30 AM
Joined: Oct 2000
Posts: 4,116
Likes: 4
Member
I thought Bert left the group, .. or was it Ernie?

Hey, maybe you know, why is Barney so Purple sometimes, does He Tan? [Linked Image] [Linked Image]

Bill


Bill
#775 03/12/01 03:59 PM
Joined: Oct 2000
Posts: 2,723
Likes: 1
Broom Pusher and
Member
That's so cool Steve!! I wish there was something to play drums to for kids shows that wouldn't blow the kids' ears out [Linked Image]

Speaking of an Ovation, my Wife wants me to learn how to play an Acoustic Guitar [she loves the sound and the way the person looks while playing deep and emotional grooves]. Maybe after 5 years, I can play something other than bar chords [Linked Image]

I'm not in a band either, nor plan to get serious in one [have too much involved with EE stuff], so as you do, I just play to the Radio, tapes, CDs and the occasional Vinyl record.
It sure helps to relieve some stress at times, plus is a nice "get away" from the world of seriousness [Linked Image]

Virgil,
Tried to look at the pictures on your site last night, but images could not be loaded [404 error]. I'll check again today, so if the problem is corrected, don't worry.
If you or Bill are not aware of this yet, maybe it will be corrected.

Scott SET

[This message has been edited by Scott35 (edited 03-12-2001).]


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
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