[moralfibre]

Originally Posted by praveen_v

6K for 5.1?? I thought the 6.1 came for that price.

6.1 costs Rs. 6,490/-.

[praveen_v]

I was thinking of going for the JBL1004 amp running the Electra 6.1's up front and a JBL 12" sub with the rear channels bridged. The 6.1's had a rms rating of 70watts@4ohms and the 1004 pumps 100w rms@4ohms and it was kind of matched.

But the electra 5.1 can handle only 50w rms @4ohms and the amp might be an overkill for those speakers, but perfect for the subs. So what do i do?? look for another amp or go for the 1004?

[moralfibre]

Originally Posted by praveen_v

I was thinking of going for the JBL1004 amp running the Electra 6.1's up front and a JBL 12" sub with the rear channels bridged. The 6.1's had a rms rating of 70watts@4ohms and the 1004 pumps 100w rms@4ohms and it was kind of matched.

But the electra 5.1 can handle only 50w rms @4ohms and the amp might be an overkill for those speakers, but perfect for the subs. So what do i do?? look for another amp or go for the 1004?

Don't go by what RMS what puts out. An amp with lesser power can do more damage to the speakers than an amp with more power. In your example, the amp puts out more than twice and is quite good since you have a lot of headroom. Don't worry about mating the 1004 to the 5.1's. They'll work well.

[Bass&Trouble]

Originally Posted by praveen_v

6K for 5.1?? I thought the 6.1 came for that price

6.1 is 6.5k. The 5.25" driver has almost the same magnet and voice coil size as that of the 6.5". The 5.1 is rated at 60 Wrms.

Originally Posted by praveen_v

But the electra 5.1 can handle only 50w rms @4ohms and the amp might be an overkill for those speakers,

You will blow the 5.1s if you play them at full rated output of the amp playing pink noise for 12 straight hours.

If you are willing to not perform the abovementioned experiment, then dont worry about the power matching.

P.S. Even the 4.1 can also take the full output of the 75.4/ 1004 with program material and high pass of 80-100 Hz.

[praveen_v]

Originally Posted by Bass&Trouble

6.1 is 6.5k. The 5.25" driver has almost the same magnet and voice coil size as that of the 6.5". The 5.1 is rated at 60 Wrms.

You will blow the 5.1s if you play them at full rated output of the amp playing pink noise for 12 straight hours.

P.S. Even the 4.1 can also take the full output of the 75.4/ 1004 with program material and high pass of 80-100 Hz.

Thanks B&T for clarifying that. So i can stick with the 1004. But what's this "program material"??


One more question, what's the relation between the rms output and the gain of an amp?? is it like at max gain the amp will push out the specified rms??

[RAC]

Originally Posted by Bass&Trouble

P.S. Even the 4.1 can also take the full output of the 75.4/ 1004 with program material and high pass of 80-100 Hz.

This is good. I had the same doubt in my mind as I had planned an upgrade to EL4.1 from the current speakers and had thought of running them on my 1004.

[Bass&Trouble]

Originally Posted by praveen_v

But what's this "program material"??

What normal people listen to on their stereos, i.e. music, audio from movies, speech etc. Hence.. not tones, sine waves or noise.

Originally Posted by praveen_v

One more question, what's the relation between the rms output and the gain of an amp?? is it like at max gain the amp will push out the specified rms??

Lets assume that the markings on the gain control on amp extend from say 6V to 250mV (decreasing voltage units as you turn clockwise).

So, if you connect a 6V pre-out head unit to the amp, leave the gain in the minimum position (i.e 6V on the dial), and when you turn the head unit's volume control to max (head unit is now "outputting" full pre-out voltage), the amp will (ideally) deliver maximum unclipped power.

But if the pre-out voltage from the head unit is lower than 6V - say 4V, you turn the gain knob clockwise to 4V so that the amp increases its gain to compensate for the lower input it receives. Not to put out more power. But to put out same maximum power at this head unit's full volume.

[praveen_v]

Originally Posted by Bass&Trouble

So, if you connect a 6V pre-out head unit to the amp, leave the gain in the minimum position (i.e 6V on the dial), and when you turn the head unit's volume control to max (head unit is now "outputting" full pre-out voltage), the amp will (ideally) deliver maximum unclipped power.

But if the pre-out voltage from the head unit is lower than 6V - say 4V, you turn the gain knob clockwise to 4V so that the amp increases its gain to compensate for the lower input it receives. Not to put out more power. But to put out same maximum power at this head unit's full volume.

Oh now I get the whole point. That was a great explanation . So it means that the higher the voltage of the pre-outs from the HU, the better, since the amp will work less and hence less heat generation and cleaner music right??

supposing that the HU gives out 4v pre-outs, and we set the gain to a much lower voltage in the amp, say 1v(or even less), then will the amp try to push more power, thereby heating itself and killing the speakers?? and also clipping the sound??

[praveen_v]

Originally Posted by praveen_v

Oh now I get the whole point. That was a great explanation . So it means that the higher the voltage of the pre-outs from the HU, the better, since the amp will work less and hence less heat generation and cleaner music right??

supposing that the HU gives out 4v pre-outs, and we set the gain to a much lower voltage in the amp, say 1v(or even less), then will the amp try to push more power, thereby heating itself and killing the speakers?? and also clipping the sound??

***Bump***
No answer to my earlier post??

[Bass&Trouble]

Originally Posted by praveen_v

So it means that the higher the voltage of the pre-outs from the HU, the better, since the amp will work less and hence less heat generation and cleaner music right??

While higher pre-out voltages are beneficial from the point of view that the signal to noise ratio remains high during transmission, it doesnt exactly make the job any easier for the amp.

Originally Posted by praveen_v

supposing that the HU gives out 4v pre-outs, and we set the gain to a much lower voltage in the amp, say 1v(or even less), then will the amp try to push more power, thereby heating itself and killing the speakers?? and also clipping the sound??

Your system will max out in terms of the loudness level at a lower head unit volume level than max and if you turn the dial further, the amp will produce clipped output. It could overheat/ go into thermal protection/ kill the speakers too.

[DerAlte]

Originally Posted by praveen_v

... higher the voltage of the pre-outs from the HU, the better, since the amp will work less

Correct.

Originally Posted by praveen_v

and hence less heat generation ...

Approximately correct - depends on the amp rating and the impedance of load connected

Originally Posted by praveen_v

... and cleaner music right??

Yes and no. Depends on the make of amplifier. For example, if an amp makes bad music, giving it a higher HU output might make matters worse.

Originally Posted by praveen_v

supposing that the HU gives out 4v pre-outs, and we set the gain to a much lower voltage in the amp, say 1v(or even less), then will the amp try to push more power, thereby heating itself and killing the speakers?? and also clipping the sound??

Depends on a lot of things that you are leaving out in the equation:
* The absolute power rating of the amp
* The sensitivity and power rating of the speakers
* The 'loudness' demanded - HU volume, and loudness of the music being played

[praveen_v]

Originally Posted by Bass&Trouble

While higher pre-out voltages are beneficial from the point of view that the signal to noise ratio remains high during transmission, it doesnt exactly make the job any easier for the amp.

now that has got me a little confused. Which is better? A low level preout or a higher level preout from HU, considering a good amp like the GTO75.4?? Is the extra cost paid for the HU justified?

Originally Posted by DerAlte

Correct.
Approximately correct - depends on the amp rating and the impedance of load connected
Yes and no. Depends on the make of amplifier. For example, if an amp makes bad music, giving it a higher HU output might make matters worse.
Depends on a lot of things that you are leaving out in the equation:
* The absolute power rating of the amp
* The sensitivity and power rating of the speakers
* The 'loudness' demanded - HU volume, and loudness of the music being played

And one more question. What are the advantages of more amp pre-outs from the HU?? consider a setup with
1.front components and sub running from a 4-ch amp, rear co-axes off the HU
2.front components and the rear co-axes running from a 4-ch amp. no sub.

how many pre-outs are required for both these setups?

[nitrous]

The higher the pre-amp voltage, the stronger is the signal to the amp.

[DerAlte]

Originally Posted by praveen_v

And one more question. What are the advantages of more amp pre-outs from the HU??

Convenience, if a conventional setup. If an active setup from HU - band separation (low, mid, hi)

Originally Posted by praveen_v

consider a setup with
1.front components and sub running from a 4-ch amp, rear co-axes off the HU
2.front components and the rear co-axes running from a 4-ch amp. no sub.
how many pre-outs are required for both these setups?

2 L+R pairs!

[Bass&Trouble]

Originally Posted by praveen_v

now that has got me a little confused. Which is better? A low level preout or a higher level preout from HU, considering a good amp like the GTO75.4?? Is the extra cost paid for the HU justified?

I don't know which two head units you are considering, but anything 2.5V + should serve well.

Originally Posted by praveen_v

And one more question. What are the advantages of more amp pre-outs from the HU?? consider a setup with
1.front components and sub running from a 4-ch amp, rear co-axes off the HU
2.front components and the rear co-axes running from a 4-ch amp. no sub.

how many pre-outs are required for both these setups?

Take the example of Pioneer. Most of their 2 pre-out head units have a configurable pre-out pair, i.e. Front + Rear OR Front + SubWoofer. So in both your above examples, one with 2 pairs of pre-outs will do the job. UNLESS you expect to upgrade in the future and amp the rears also. In which case a 3 pre-out head uni is future safe.