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Old 16th August 2006, 12:29   #181
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Quote:
Originally Posted by santosh.s
Usually when you reduce the impedence of the speaker connected to a given amp, it usually does supply more power. But it is at the cost of more distortion. So when you compare power ratings of an amp for various speaker impedences, you must also see THD rating in each case. In other words, the amp may provide higher power for 2-ohm speakers as compared to 4-ohm, but at the same time corresponding THD figure is also expected to be worser (higher)!
Santosh, the GTO 75.4 is rated at <1% THD for both 2 ohm and 4 ohm load.

LBM, Did some more R&D, you are right in that i cannot connect the speakers in parallel but I can connect them in series. This will cause the effective impedance to double i.e. go from 2ohm to 4 ohm and we will still have about 100W of power available to drive the speakers.. So what say whats the disadvantage of this mode.
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Old 16th August 2006, 12:31   #182
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yes u have got this right........good work bro.........connecting 2 ohms speaker toghter will get 1 ohms and this will not be good if u dont have a 1 ohms stable amp.....pionner 944 is 1 ohms stable in 4 channel mode......

the thd will be in limit if the amp is stable in 2 ohms load and if recommended by the manufacturer.....it will not effect so much so dont worry about that factor.


for eg the 944 spec are as following

Continuous power output
75 W x 4 (at 14.4 V, 4 W, 20 20,000 Hz, 0.04% THD)
250 W x 2 (at 14.4 V, 4 W, 20 20,000 Hz, 0.4% THD)
125 W x 4 (at 14.4 V, 2 W, 20 20,000 Hz, 0.4% THD)

Load impedance
4 channel mode (1 8 ohms allowable)
(Bridge connection: 2 8 ohms allowable)


the thd increases but not enough which will decrease the sq

but if the amp who`s thd increase with load then that amp is surely waste of money....and the point above said is 100% correct..
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Old 16th August 2006, 13:04   #183
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LBM what about connecting in series any problems you forsee with that ??
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Old 16th August 2006, 13:30   #184
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Quote:
Originally Posted by jinu_joseph
Santosh, the GTO 75.4 is rated at <1% THD for both 2 ohm and 4 ohm load.
.
I guess they have specified the worst case (2-ohm) THD, may be for 4-ohm it should be better! but then it depends on how much is the difference (practically) between 1% and say 0.1% or something. I have seen that many high end audio systems specify THDs of the order of 0.0x %, so what say gurus, where does 1% stand?
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Old 16th August 2006, 13:38   #185
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Quote:
Originally Posted by jinu_joseph
If so is it possible to power both the fronts comps and the back coax using just 2 channels of the amp ie. one channel to power the 2 fronts and one channel to power the 2 backs ?
If I got you right, you will miss a basic thing with this setup- stereo image itself. It will be more like converting a stereo to mono! You should combine two speakers on either side instead... left and right, if you want to make parallel/serial connections.
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Old 16th August 2006, 13:44   #186
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Quote:
Originally Posted by jinu_joseph
LBM what about connecting in series any problems you forsee with that ??
connecting in series the 2 ohms model will yelid less output but nothning will get damage but this lead to less contorl of sound in car like if u connect the front two speakers in series this is bad no stereo imaging if u connect the front and back each side then no fader controll thats why i said 4 channel for each speaker......

firstly the 1% thd will be at full rated power which will be if achived for a very small peaks in the continous program also. And to identify that 1 % in a very short period will be very difficult to recognize the distortion.....


But we have people in this forum who have special hear which could help u to understand the differnce of the 1% thd and .01 % thd........I Rule:
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Old 16th August 2006, 14:11   #187
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one thing I wanna add here

When an amplifier is driven with a signal, the output of the amplifier is an amplified version of the input signal PLUS any distortion created by the amplifier. All amplifiers and signal processors add distortion to the signal. The levels of harmonic distortion in a high quality amplifiers are sooooo far below audibility that they are basically of no concern. When someone tells you that one amplifier is definitely going to sound better because its THD is rated at .002% vs an amp with .05%, you can be pretty sure that he doesn't know what he's talking about. Many people believe that THD below 1% is not audible and I believe they're probably correct. The fact is, especially in an automobile, the amplifier is the least of your worries. Speakers used for mids and highs commonly produce between 1% an 5% THD and for subwoofers the numbers can easily reach 10%. This doesn't even take into account all of the resonances of all of the plastic and metal panels in the vehicle.

Like I said before the 1% thd is not audible in car envoirment.......
taken from http://www.bcae1.com/thd.htm

Last edited by low_bass_makker : 16th August 2006 at 14:13.
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Old 16th August 2006, 14:34   #188
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Quote:
Originally Posted by navin
Most modern amps can be bridged. Bridging an amp allows both channels of the amp to work in unison thereby making a 2 ch. 100W amp into a 1 ch. 200W amp (the exact increase in power is based on amp design).
Theoretically, this increase in power is 4 times the orginal power given out by one channel...
for eg. if the amp is rated at 100 WRMS / channel.... theoretically, if bridged should give out 400 WRMS...
Like navin has mentioned, the exact power increase in based on amp design....

If i remember right, I have seen only one amp which gives out this increase in power 4 times....
its the MTX amps...
regards,
ant.
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Old 16th August 2006, 15:08   #189
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the pioneer 944 gives about 3.3 times

in 4 channel mode it gives 75 X 4 at 4ohms
in 2 channel mode it gives 250 X 2 at 4 ohms
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Old 16th August 2006, 16:20   #190
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Quote:
Originally Posted by anToNIcHeN
If i remember right, I have seen only one amp which gives out this increase in power 4 times....
its the MTX amps...
regards,
ant.
There are a lot of amps that do it. MTX is just one of them.
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Old 16th August 2006, 16:39   #191
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yah yah... MTX... ..

I shant say anything more... B&T will chew me up!!
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Old 16th August 2006, 16:52   #192
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Quote:
Originally Posted by kb100
yah yah... MTX... ..

I shant say anything more... B&T will chew me up!!
kb?... why that grin?... B&T are you using MTX?...
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Old 16th August 2006, 17:23   #193
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Quote:
Originally Posted by kb100
yah yah... MTX... ..

I shant say anything more... B&T will chew me up!!
Tee hee, no pal. Even my previous outburst had nothing to do with MTX, I remember arguing and consuming 2-3 pages of web footage over that

Quote:
Originally Posted by anToNIcHeN
B&T are you using MTX?...
Sir, God has been kind uptil now.

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Old 16th August 2006, 17:56   #194
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Hi
As per popular advice, i am looking for an HU with min 3 pre-amp outs (Front, back and sub). I noticed that 3 preamp outs are generally present in mid to high end HUs. I was going thru Blaupunkts website when i realised that they seemed to have 5 preamp outs..even on the mid range models. Is this correct or am I missing something.
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Old 16th August 2006, 18:23   #195
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Quote:
Originally Posted by jinu_joseph
Hi
As per popular advice, i am looking for an HU with min 3 pre-amp outs (Front, back and sub). I noticed that 3 preamp outs are generally present in mid to high end HUs. I was going thru Blaupunkts website when i realised that they seemed to have 5 preamp outs..even on the mid range models. Is this correct or am I missing something.
You are mistaking 3 pre-amp outs with 3 pairs of pre-amp outs. If it says 5, it probably has one pair for the front (one each for left and right), similarly one pair for the rear, and a mono sub out. 3 pairs would mean a stereo or dual mono sub out.
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