Putting the finishing touches to installing a set of Infinity 6500cs components last night and I noticed the head unit display dimmed on bass notes.

As anyone else experienced this?

Never noticed it before as the stock speakers would not take the volume without cracking up!

As I'm replacing the HU (new one in the post) and I'm not going for amps yet, the plan is to beef up the power and ground wiring to the HU. All I can say at the moment is that the Infinitys sound damn good, even though the instal was a bit more fiddly than expected - more on that later after I've downloaded a few pics.

When my sub is giving it some at night, it definitely has a small effect on the headlight beam...

Also with both windows up, pushing both buttons "up" in conjunction also dims the beam a little bit - I guess its just power temporarily being diverted away from the lights. I put it down to a Skoda ideosyncracy.

Could be that you're drawing a lot of current for the bass. Do your headlamps dim as well?

Have a read of this, taken from the talkaudio FAQ section and was written by Geoff Dutch...

Option #1 : The Magic Wires

Replace the factory ground wire between the battery and the car chassis with at least a 4-gauge cable. This will help minimize voltage drops caused by high resistance in the stock cable. Also replace the stock charging wire between the battery and the alternator with at least a 4-gauge cable. If the alternator has a chassis ground cable, upgrade that wire too.This is relatively inexpensive and should be done for every system 500 watts or higher in total amplifier power.

Option #2 : More Powerful Alternator

There is simply no substitute for a large supply of current. Batteries and capacitors don?t produce anything; they are merely storage tanks. When a vehicle is running, the alternator delivers the vast majority of the current demanded by the car and audio system. For this reason, alternator upgrades make a lot of sense for powerful street systems. This is not a cheap upgrade, but should be considered before any of the following if the vehicle is having problems supplying adequate current. It is often possible to purchase a more powerful alternator for about the same price as a couple of capacitors, an additional battery and all the wiring needed to connect them? and the alternator will actually work.

Option #3 : Capacitors

A capacitor helps to maintain voltage during very brief peaks in demand. They are particularly useful in sound quality oriented systems with moderate power. However, they won't do much for you when you're playing Kylie Minoqgue at high volumes (aside from looking a fool!!) ? they simply can't supplement current for very long.

Option #4 : Multiple Batteries

Great for McDonalds car park listening, BUT just something else for the alternator to have to supply current to once the vehicle is running. Not recommended for ?street systems? although some demo car and competition cars might benefit from them if they spend a lot of time at idle playing loudly without an external power supply connected.

As it says CAPs aren't good even though most people recommend them, but what you will find is that making sure you have replaced/added to the standard earth cable will improve the situation loads. Also as you said, uprading the HU wiring will also help, I normally run a new cable direct to the battery for each, but make sure the + is fused