View Full Version : Do i need an amp
Tony2Quick4u
19-12-2002, 14:20
Hi all
the gf is buying me some speakers for xmas, they are the kenwood ones, door speakers and the tweeters, part No. KFC-PSR71P. Do i need an amp to fully power the door speakers or not? i mean they will they run ok off the unit and be underpowered or just working fine? the head unit is 4x50w. Cheers
:D
they will sound a bit better than the stock ones without an amp, but to get the best from them its best to amp them up....then you will see the true quality of them.
Tony2Quick4u
19-12-2002, 14:43
thanks alot for that but they will still sound good without an amp wont they?
:cheers:
They will sound good without the amp. What I think Mike is saying, is that you won't be able to get everything out of the speakers without using an amp.
By the way the 4x50w is not really true. Most built-in amp will only produce something like 4x12w at more than 2% thd (that's 12w from 20-20kHz with alot of distortion). Besides you can't find a true 4ohm speaker, the range is usually 4-32ohms depending on the frequency it's trying to produce.
Tony2Quick4u
19-12-2002, 15:37
oh right cool, thanks for that.
:D :cheers:
ALSO RUN OXYGEN FREE WIRES, YOU CAN HEAR THE DIFFERENCE!
Icecavern
30-12-2002, 00:47
Do you need an amp?... NO...
Do you want an amp?... Hell YES...
Just by replacing the standard crappy tracing paper speakers you'll notice a MASSIVE difference in clarity and midrange responce. But amp them and you get even more benefit... ;)
Pete
hopkinsgm
30-12-2002, 10:55
It's all more weight. See you on track :D
Originally posted by prc
By the way the 4x50w is not really true. Most built-in amp will only produce something like 4x12w at more than 2% thd (that's 12w from 20-20kHz with alot of distortion).
Yep, would have to agree with that, and probably pushing it a bit to say the amp would go down to 20Hz for the built-in jobby! The frequency response would taper off by then.
You see, the power supply in a head unit has to do a lot of work. It has to power the CD/tape/MD player, the tuner, the display, remote receiver, the pre-amp, and then it has to cope with the power-amps and try and keep noise away from each separate component whilst it does this. That's a lot to ask, and you simply can't squeeze mega power out of DIN size box. It ain't possible.
Using an external amp gives you a 2 fold benefit. You gain in terms of sound quality from the power-amp to the speakers because there's a bigger power supply in there to feed it. How many of you like bass but as soon as the kick-drum spike comes in, it's out of breath? Or as soon as some big bass guitar or synth bass frequencies come in, it muddies everything else? Having a dedicated power supply for the amp in a separate chassis will make sure there's plenty of power and control to produce the cleanest, purest sound it can. The second benefit is that if the internal amp isn't loading the power supply in the head unit (because the speakers aren't connected to it), then that gives more available power to the rest of the head unit, including the all-important pre-amp which is always working regardless of whether you're using external amps or not. The pre-amp brings the signals from the source components (like CD or radio) up to a level that the power-amp can deal with, the part that delivers power to the speakers.
So using an external amp is a good thing. Well, that's not always the complete answer. It's a lot of work doing this properly. External amps use more current in order to provide good drive to the speakers, or it's like running something set-up for high-octain fuel on unleaded; there's just not enough food! So larger power cables need to get connected to a good power source (like straight to the battery where there's lots of amps). Good line cables with a very low resistance need to be used between the head unit and the amp, or you will lose drive and make the sound strained by using too much gain at the amp. A half hearted installation will bring more problems. If you're going to put amps in, make sure the total cost of installation is considered, which will be much more than just amps themselves.
One more thing. Lots of amps say they're 800watts or 4 X 200. That's great, but they're talking about peak or calculated total music power, which doesn't tell you a thing. A cheap amp will give masses of distortion because it can't keep up with the discharge at high volumes. Look at the RMS (Root Mean Square) ratings on speakers and amps. 50 watts per channel RMS is good. I'm using 150w RMS and have it turned down. First rule of amps: the more powerful the amplifier, the better it sounds at low volumes. It also gives you a richer sound.
Also look at the line level voltage output on your head-unit, and the line-level sensitivity on the amp to make sure it's well in range. Once everything has been successfully matched, and good quality cables have been used to connect the jigsaw together, it will sound fantastic! But don't be fooled into thinking it will cost a fortune to get this power. It will cost you even more to cure problems if you try to take shortcuts.
Hope all this helps :D
Originally posted by josh
ALSO RUN OXYGEN FREE WIRES, YOU CAN HEAR THE DIFFERENCE!
On my home HiFi, I'm running QED silver aniversary bi-wire cable. It's expensive (£8.50 a metre) but it's made a massive difference to ambience, depth, whispers and detail. Has anyone got any silver plated speaker cable in their car and demo'd the difference?
Originally posted by Chester
50 watts per channel RMS is good. I'm using 150w RMS and have it turned down. First rule of amps: the more powerful the amplifier, the better it sounds at low volumes. It also gives you a richer sound.
I agree with Chester but have got a couple of things to add.
The RMS power is important, but it also depends at what voltage it's measured at. Some amps (MTX for example) have a 12V rms rating (like 25x2). Since a healthy car electrical system will be producing something like 13.8-14.4 volts the rms rating will be more like 45x2 (depending on amp construction).
I don't fully agree with the more power = better sound rule. I think it depends on amp design. I've used some Soundstream class A amps in the past and they sound awesome! Even though they have a low wattage rating, they were 0.5ohm stable and could really make the speakers play.
I do agree that 50W/rms is good for full range or component speakers and at least 150w for a sub.