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scream for me, scream for me!
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hey guys just wondering has anyone changed the subs with replacements meaning just replacing and how do they sound with the stock amp. i have changed all my speakers in the car to 4 ohm speakers but the subs and they are ruining the sound to much vibration not any umph without crapping the rear speakers. my amp is halfway and bass is -1 . it sounds ok but lacking punch from rear its more of a distorted bass if you knowwhat i mean thanks guys
 

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blushirt35 said:
hey guys just wondering has anyone changed the subs with replacements meaning just replacing and how do they sound with the stock amp. i have changed all my speakers in the car to 4 ohm speakers but the subs and they are ruining the sound to much vibration not any umph without crapping the rear speakers. my amp is halfway and bass is -1 . it sounds ok but lacking punch from rear its more of a distorted bass if you knowwhat i mean thanks guys
Keep in mind the system is a 2ohm system stock and you are cutting your power in half by switching to a 4ohm system.
 

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scream for me, scream for me!
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Discussion Starter #3 (Edited)
well now my speakers are 4 ohm and it sounds clearer and the power is ther it seems but best of all no radio shutting down. do you suggest i cahnge the amp to 4 ohm or leave as is. a went to see someone and he said basically im stuck where i am unless i gut out things and add amps and woofers other than that he said no reason to cont such as change woofers just a waste of money etc. or did i just really mess up here ?
 

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MAX-M6/LS1
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I Have To Agree With You Take Out The Stock Speakers And Install Some Decent Speakers And Amps To Drive Them. Get A Line Level Converter To Feed The Amps From The Hu..
 

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May I quote you on that?
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The amp will generate considerably less heat into a 4 ohm speaker and therefore be much less likely to go into thermal protection. The difference is only 3dB if that. Finding a driver with greater sensitivity than stock will more than make up for it.
 

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blushirt35 said:
well now my speakers are 4 ohm and it sounds clearer and the power is ther it seems but best of all no radio shutting down. do you suggest i cahnge the amp to 4 ohm or leave as is. a went to see someone and he said basically im stuck where i am unless i gut out things and add amps and woofers other than that he said no reason to cont such as change woofers just a waste of money etc. or did i just really mess up here ?
Increasing the ohm load decreases the noise in a system, but decreases the volume so I would say if you are happy with the loudness of the system leave it alone.
 

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mistermike said:
The amp will generate considerably less heat into a 4 ohm speaker and therefore be much less likely to go into thermal protection.
Power produces the heat that causes the unit to shut-off. It takes more power to push a 4 ohm speaker with the same sensitivity and volume level as a speaker at 2 ohms, twice as much in fact. So switching to a 4 ohm speaker would cause the head unit at the same perceived volume level to shut down sooner unless the new speakers sensitivity is higher which they probably are.



mistermike said:
The difference is only 3dB if that. Finding a driver with greater sensitivity than stock will more than make up for it.
3db is noticeable and remember on the high end 3db is a lot of power. The reason 2ohm and 1ohm speaker/speaker combinations is because it is a cheap and popular way of increasing volume at the expense of harmonic distortion. 4ohm in car audio is considered the standard by which most amps measure THD. A good amp can drive 2ohm speakers with a 0.1% or lower THD which is generally considered very acceptable on anything save reference material.

As for the second part, you are correct. Another excellent way of increasing loudness is to use a more efficient speaker. Most top of the line speakers have around a 92db sensitivity with 150w+ power handling.
 

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scream for me, scream for me!
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Discussion Starter #8
Speakers I Used

speakers used alpine component in front SPS171A 1" textile dome tweeter swivels up to 15° (surface and flush mounting)
2-way crossover (12 dB/octave high-pass, 6 dB/octave low-pass)
frequency response 35-35,000 Hz
recommended power range 8-50 watts RMS
peak power handling 250 watts
sensitivity 90 dB
top-mount depth 2-1/2"

SPS170A IN THE REARS
swiveling titanium-coated PEI balanced dome tweeter
fits standard 6-1/2" and 6-3/4" (oversized 6-1/2") openings
frequency response 35-30,000 Hz
recommended power range 2-40 watts RMS
peak power 200 watts
sensitivity 92 dB
top-mount depth 2-1/4"
 

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Deuce and a Half
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actually, the amplifier doesnt get hotter with a 4 ohm speaker. Due to the higher coil impedance the current will be lower. Current being lower means things run cooler :)
 

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LiqTenExp said:
actually, the amplifier doesnt get hotter with a 4 ohm speaker. Due to the higher coil impedance the current will be lower. Current being lower means things run cooler :)
Quickly crunching the numbers in my head at 2 ohms compared to 4 ohms at 25 clean watts using an A/B design (guessing on the head unit stats) you are correct. However, even though a lower resistant circuit is losing more power to heat, it doesn't take as much power to move the speaker. At low power loads speakers at specific volume levels overcome the power effeciency loss (heat). Not to mention digital amps that run in a non-linear mode hardly lose any power to heat so running a lower resistance circuit is actually more effecient heatwise.

As a general rule you are absolutely correct (higher ohms means better power effeciency), but there is a reason that a 20watt system at .5 ohms can get a lot louder with less heat than a comparetive 160watt 4ohm system.

As a side note, I did the electrical unforgivable... I had my right hand grounded and closed the car circuit with my left by accident (it slipped). All I can say is ouch.
 

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msfyter said:
Rockford Fosgate makes a 6 3/4 sub I have them, havent installed yet
Practically any 6.5 inch speaker with 3.5" mounting depth will fit in those slots (that is what is in there stock). I would recommend getting a midbass driver that runs below 40hz if possible. The upper end is irrelevant so long as it goes to about 100 or so.
 

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Oh my f*ck!
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msfyter said:
Rockford Fosgate makes a 6 3/4 sub I have them, havent installed yet
Do you have the model number? I'm on Fosgate's website right now and in their subwoofers section the smallest listed is an 8" with a 4.1" mounting depth. Is it marketed under a different brand?
 

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Good ol' Ohm's law :)

For example, lets assume the stock 2 ohm driver as a 93dB sensitivity, and we want to replace it with a 4 ohm driver with 90dB sensitivity. Our amp will need to produce the same output current, but TWICE the voltage to reach the same listening volume (and thus TWICE the wattage, since watts = volts x amps). Say you were able to find a 4 ohm driver with the same sensitivity. Then, you'd have a happy amplifier -- same output volume, same voltage, half the current ;)
 

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If these are dual 4 ohm drivers they may be a good replacement. It could end up being a good deal, because people will stay off of them due to the mounting rings seperating. To me that is minor though.

These are classics from when I was in HS. Unfortunately I don't need 8, otherwise I'd bid on them for nostalgia. I had 2 12" blue thunders in a 5 cu ft box tuned to 25hz that was just nuts.

Here is the rockfords. I don't believe they make these anymore. This is last years speaker style for them.

Kicker
 

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Brains said:
Good ol' Ohm's law :)

For example, lets assume the stock 2 ohm driver as a 93dB sensitivity, and we want to replace it with a 4 ohm driver with 90dB sensitivity. Our amp will need to produce the same output current, but TWICE the voltage to reach the same listening volume (and thus TWICE the wattage, since watts = volts x amps). Say you were able to find a 4 ohm driver with the same sensitivity. Then, you'd have a happy amplifier -- same output volume, same voltage, half the current ;)
Almost unless I misundertsood you. You would need a 4ohm 96db speaker for the same power output as a 2ohm 93db sensitive. The main advantage to using a lower ohm speaker is it simply plays louder with the same amp. Our friend was kind enough to prove me wrong in the nicest possible way that you lose circuit effeciency lowering the load and thus generate more heat when comparing 2ohm to 4ohm and you get a better damping factor with a 4ohm setup which simply means you get a "cleaner" sound. However, between 2 and 4ohms you would be hard pressed to hear the difference.
 

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Well, this is where a big "it depends" comes into play -- because a loudspeaker doesn't have a straight line sensitivity vs. frequency curve, nor does it have a straight line impedence vs. frequency curve. You also bring in another important criteria when choosing components with damping factor (which is a function of output impedence of the amplifier -- imp. of the amp vs imp. of the loudspeaker). Again, its often quoted as a static number, but its far from ONE number. Again "it depends" on the speaker and the frequency being played ;)
 
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