Is It Just My Harman Kardon System Thats Hopeless ?

[victorgte]

Originally Posted by SD1too

You are quite right Nick. The problem is very simple and it's down to design.

The HK amplifier input is fed from the loudspeaker outputs of the radio module. As any radio engineer will know this is extremely bad practice since the distortion created by the radio power amplifier will be exacerbated by the HK amplifier. What HK should have done is to take their input from the pre-amp of the radio module.

Simon

Is there a way of performing a modification to achieve this?

[SD1too]

That's a good question Victor. I think the stumbling block would be obtaining a circuit diagram of the HK power amplifier to find out whether or not the high level input signal from the radio module goes via an attenuator which can be by-passed. When I last approached HK for information they unhelpfully took a legal position, saying that it could only be released to MG Rover Group which, of course, no longer exists.

I have the HK door speakers in my car fed directly from the Philips radio module and I'm happy with the sound. It's a great improvement upon the Goodmans loudspeakers and without the distortion of the HK amp or the, in my view, disproportionately bass-heavy rear woofer. But then I have a rather old fashioned taste in hi-fi sound!

Simon

[Geoff130]

Actually Simon it's not as bad a design as you think, the input impedance is quite high reducing the load on the head units amps but having low gain means it is less susceptible to noise over long cable runs as in highline without navigation. The problem lies in the active filters and the distribution of power. I haven't completely mapped all the HK amp nor all it's variants however see my earlier posts for the door speaker filter circuits and how to modify them. Here's the input section and summed output to the sub driver.

[murphyv310]

Hi.
The amp should not be fed from speaker outs on the head unit, distortion from the head unit amp is then further amplified by the sub amp, impedance has nothing to do with it at all unless it's below around 20 ohms which is highly unlikely. The sub amp should be fed from a variable line out feed from the head unit with the sub amp having an extra stage of amplification.
Changing the caps in the sub amp is only masking the deficiencies in the speakers and the woofer in the rear is utter tat, using a port too is nonsense in a car boot as it will only feed bass back out of phase, one reason it sounds better with the boot open, as the out of phase sound from the port is lessened, an infinite baffle would have been better. Speaker systems with a port require very careful mathematical calculations to work properly, one thing you will never get correct in a car boot. Could be an idea to try sealing off the port and test.

[Geoff130]

My point about changing the caps is that people change the door speakers and get no improvement then wonder why. The problem is the standard HK amp doesn't feed low frequencies to the door speakers so no matter what speakers you put in the doors the bass response will always be poor.
I agree about the sub though it's a complete waste of time and is better disconnected.

[mcd840]

Had the full HK set up when I had my contemp se and felt that it was nothing to rave about, I get better sound from my previous and current vauxhall systems

[DEVYL]

Originally Posted by T16

Anyone care to comment on why it sounds so amazing with the boot open?

Has anyone actually tested changing the phase of the sub to see if it improves things with the accoustics of the car?

Im tempted to disconnect the sub completely, it seems to manage to sound even worse than the base Kenwood setup in a diesel ZT.

I cannot believe that another member is having the same problem as I do. With boot open powerfull bass and with the boot lid closed, rubish sound. I have investigated the problem, even changed the speakers but not the result I was looking for. I went to a friend who is breaking his bmw e46 and compared the HK sound system. I have found the problem. In our rovers, the speaker magnet is in the trunk and the speaker itselt in that plastic acoustic box ( rubish design ) and then in the cabin. In the bmw ... the magnet is inside the cabin! The e46 subs have the amp included in the speakers case so it is not impossible to fit it on our rovers. I'm working on it..

The coupe version have the speakers in the same case, the sedan has them separated.

Basically, in my opinion, there are 2 options to dramatically improve the sound system :
1) complete replace the sound system with the e46 oem sound system

2) go aftermaket with sub in the trunk ( cheaper version ) or a nice design with hidden speakers ( expensive version )

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