clipping and impediance...

[Etac 10+ year member]

ok i just wanna make sure im correct when assuming this...

i've noticed my dedicated midbass speaker tends to clip before my other speaks do... but its defently not being overpowered.. so the only logical conclusion i can come up with is..

im sure as most of you know impediance changes depending on the frequency and the driver... even tho my speaker is rated at nominally 4ohms... at 60hz.. its resistance is more like 12 ohms... and at 36 its like off the charts..

so i figure its clipping at the midbass (60hzish) first because the ohms is 12ish compared to the 4 in the 100hz ish range...

and i know this part isnt exact but its a good example...say an amp produces 100 watts at 4 ohms... 200 at 2 ohms... so at 8 it would be 50... ect....

so basically thats whats causing my amp/signal to clip right? trying to produce more power than it can at the given impediance.. correct?

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[FoxPro5 5,000+ posts]

I think you're over thinking it and confusing yourself. If speakers offered no impedance/resistance the amp wouldn't have to do anything to power them.

If the driver indeed sounds distorted then it's the amp fault, not the speaker. The speaker just offers a reactive load. A speaker can't distort on it's own.

You are over driving the signal and causing distorted output. Ignore the speaker rating and the amp rating, they are fabricated lies.

 

[Etac 10+ year member]

yeah i understand what you're saying but the thing is i know its the amp thats clipping, but i think its clipping because of the speaker...and the resistance the speaker presents at given freqencies...

ok, am i wrong when saying... let me think how to word this...

say you set the gains to run 10 volts .. (ignore resistance for now)

now given an equal signal reguardless of freqency.. the amp will always try to produce that 10 volts, correct?

ok, now assuming that is true, now lets add resistance into this equation..

lets take 4... 10 volts @ 4 ohms =

25 watts

now lets take 12 ohms... 10 volts @ 12 ohms = 8 watts..

now like is aid before, the impediance changes throughout the speaker.. depending on the signal (freqency) thats running through the coil

at 100 hz say its 4 ohms... at 60 hz say its 12 ohms...

now you give it a 10 volt signal playing the ranges 60-100

at 60hz it would be producintg 8 watts.. at 100hz it would be producing 25..

lets assume 10 volts is the limit for clean power

so does it

a) still produce a clean signal... just plays it lower since its only 8 watts or..........

b)since its trying to make an equal signal.. at both these points, it cannot.. the signal its outputting is clipped at 60hz because it cant reach its peak and hits a wall from resistance..so the top of the sine wave becomes flat and clipped...

 

[skateboardkid 10+ year member]

No it would only make more power if the impedance was falling down to 2 or 1 ohm, 60 Hz is the lowest those mids should Be playing anyways - you mention 32Hz that is strictly sub material my friend.

Find the point of lowest impedance and set your gains using that tone if it makes you feel better, your electrical theory is wrong and you are over thinking several key points.

"at 100 hz say its 4 ohms... at 60 hz say its 12 ohms..."

now you give it a 10 volt signal playing the ranges 60-100

at 60hz it would be producing 8 watts.. at 100hz it would be producing 25????

really impedance rose from where you set your gains wattage would go down.

Set your gains with a 100Hz tone then, Music is dynamic and changing constantly - Why don't you measure the amps output power when you expect it to make more, playing tones and report back to us with the findings.

 

[mokedaddy 5,000+ posts]

You cant hear clipping.

Distortion can come from many factors.

 

[Etac 10+ year member]

thanks for the responses guys, i found out my problem (sorta) check this thread if you want:

http://www.caraudio.com/forum/showthread.php?t=358318

and mokedaddy, you can hear clipping... its just hard to detect... take a test tones at 0 dbs.. in a audio editor, listen to it... then up it by 1 db, so its clipped, trust me you can hear it

 

[mokedaddy 5,000+ posts]

thanks for the responses guys, i found out my problem (sorta) check this thread if you want:
http://www.caraudio.com/forum/showthread.php?t=358318

and mokedaddy, you can hear clipping... its just hard to detect... take a test tones at 0 dbs.. in a audio editor, listen to it... then up it by 1 db, so its clipped, trust me you can hear it

#1 who listens to test tones?

#2 you are hearing distortion generated by clipping.

 

[Etac 10+ year member]

well im just saying... clipping obviously makes a difference, that *can* be detected

and you're right, clipping generates distortion... call it what you want

 

[mokedaddy 5,000+ posts]

You can have soft clipping without audible distortion. That is the difference. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Etac 10+ year member]

well if you got so much free time read my other post and help me out =]

 

[mokedaddy 5,000+ posts]

Is it just on test tones or on music as well? Is the source cd or mp3?

First I would take a random set of rcas and try those. You dont even have to take out your interior. Second how solidly are the speakers mounted? Are they enclosed (sealed pods/door panels) or are they just in the door?

 

[Etac 10+ year member]

i tried different RCA's, same problem...

speakers are mounted in the doors, but these 6.5s play pretty deep... i have them just in custom brackets, sealed with modelling clay... like i said, with one amp connected they pound, rattle my doors too much...

but when i connect both amps.. or hell even if i daisy chain the 4 channel amp to itself... the bass is like half as loud.. and 60hz down really really suffers.. (i know doors shouldnt play that but still doesnt make sense) and even the 80hzish range after a certain volume (about 30-50 watts) just sounds like its completely hollow... but still sounds "clean" but with only the one amp connected, not only does it play deeeper, it plays much louder...

and yes its on music as well, thats where i first noticed it, playing korn - dead bodies everywhere... if you know the song or wanna check it out, just listen to the intro.. teh deep bass it begins with... and i hate to be redudant, but like i said one amp or just the mids connected, they rattle my doors insanely... with another amp daisy chained (same amp or a different one, and orders reversed) it just lsoes so much output and almost all depth, its like i have a 48db crossover at 100hz

i gotta drive to class but i got a computer in there so ill be back on to check replies in like 45 mins

 

[mokedaddy 5,000+ posts]

Have you tried an additional set of rcas as opposed to just daisy chaining them? If so I take it the results were the same?

Also which amps on which speakers?

 

[Etac 10+ year member]

ok well i forgot i did wire another set of rcas from the HU, so on my way to class (which im in now) i just picked up the couplers i needed cause it was original too short, so i wired em up real quick.. and same problem...

no longer daisy chaining them... and maybe my 48db crossover at 100hz might of been a little sarcastic.. but its still a very very drastic change...

now the amps im using are the one in my sig (jbl gto) and the one i took out of my closet was a sony (shhh dont tell anyone) this was just temp for my mids, i never planned on using it ever again, but i thought maybe the jbl was lacking in power to power all 6 speakers (upper mid and tweet are passive atm) so even tho its a sony it does a decent amount of power and should be more than enough for my midbasses...

so anyway i guess its a power problem? i do have a shitty alt (85 i think it is) and the battery is still the one that came with the used car... but i mean it would have to be a pretty shitty battery not to handle like 500 watts,,, actually its not even even reaching full volume, so its not even hitting that high... =\

 

[mokedaddy 5,000+ posts]

Do you have a digital multi meter to check voltage at the battery and at the amp?