steve McCulloch

I installed some 6*9's about 6 months or so ago. The sound quality with some subs in the boot was excellent.. Now at from mid range volume the rear of the car rattles to bits

I think its the rear metal parcel shelf. I have some 6*9's mounted below with mdf underneath to try and cut any rattles down. I just find it surprising that the rattle shave only just started. Even now when I dont have the system on at all the rear shelf seems to creak and groan. To cap this off t6he Tweeter wire is now doing my head in... this seems to be resonating at btween 2800-3400 rpm.... I will need to get the doors off and see what I can do

The Focal speakers I have seem to resonate bits in the car fairly badly. I will be removing the rear speakers completely and ditching the Focals to Dyns (what I had previously) to see if I can get rid of the bad resonating rattles.... has anyone else found that changing speakers and set up has removed resonance??

chiark

Steve,

Is there any chance that a standing wave is forming behind the speakers? I've heard of this before in some cars...

A friend recommended putting foam packing material on the door metal where the driver fires into. The stuff is foam with little points on it, and he swears by it...
Cheers,
Nick.

steve McCulloch

Thanks

Hmmm I've thought of this...... and it was mentioned by ... shock horror.... Sextons!! a while ago

I think they were a little bit upset when they fitted the high end range of Focals into my car as a make do inbetween getting some Dyns again... I think they were surprised when I said the focals were naff, and they cost me £500..

I'll try the Dyns and then the foam... if this does not work that'll be the last straw and I'll revert the car back to completely standard stereo gear... a Fairly harsh circle to take and a very costly one... but I've had enough..

I'll just have to listen to the engine note instead...

I am in two minds about replacing the front and bridging my amp to get 2 channels per side.. I want to have my eardrums reamin intact!...

chiark

Bridging an amp will increase the power but at the expense of higher THD for a given power output.

If you're up for a challenge, you'll need a test tone (CD or otherwise) and a true RMS voltmeter to set up your amp. Play some music that you know well with your amp in the current config, then play the test tone at a known volume setting on your head unit. Measure the voltage across the speaker terminals...

Bridge the amp, plug in, set gain to be same as before and listen to music. If it sounds worse, you're noticing the change in thd and probably shouldn't go for a bridged setup. I'd imagine that your front speakers are pretty transparent so any increase might be noticable?

I've run bridged before now and reverted back to single channels...

steve McCulloch

I've bridged before on the Dyns with the Genesis amps. Running on single channels.. the sound was not loud enough

I also had the added problem that the amps were clipping when the Bass kicked in which effectively destroyed the Front speakers (twice) before I realised and added a large power cap to the Monoblock

I dont have an rms voltmeter.... but we'll see.

I must say that I was surprised to get quite a lot of sound from the Focals running on a single channel.. They appear louder at a given power input... so maybe the Dyn speakers are just not that efficient if they resist so much to power hikes!!

For the next car I'll keep it all standard!!. I should have listened to Adam M ages ago about not bothering... as with engines I seem to throw thousands also into the stereo configuration on every car.... as with the engine improvements the Scooby has been by far the worst car to get the best out of....

Moan over

chiark

That's the annoying thing with car audio: chuck a new head unit in, and a 100 quid pair of speakers and it'll sound much better than standard. Beyond that, you're fighting a losing battle - but it should be fun

If you're ever around yorkshire way I've got a digital oscilloscope that'd do the job for you...

steve McCulloch

Ever around Yorkshire.. Try to avoid if I can ... too many dodgy IT consultants

But thanks for the offer...

Oh... In forgot to say I'm a Yorkshireman... probably why I complain so much

chiark

Yeah, I guessed as much - you used to be from Bristol and Wakefield... You've obviously moved up in the world

steve McCulloch

No just sideways

Are'nt you the guy that works for Unisys?? - or I may be mixing up with someone else...

chiark

I am indeed that chap

steve McCulloch

Ahhh Mr NL then?

chiark

Aye

steve McCulloch

To put you in the picture you've done some project work for an associate... they found it amusing your interests in this web site... I will say no more as I dont know any more!!

steve McCulloch

Where can I get this foam stuf from?

Re-Bitten Hero

Scavenge cardboard boxes for packing material - it's widely used for anything fragile. If you know anyone who works with microchips and stuff like that, they're bound to be able to find some. I grabbed some from boxes at work that were going to be thrown out...

Richard

Re-Bitten Hero

Just a quick thought - I've got the foam stuff with pointy bits on inside my front doors (which run Xtant 6.5s) and it really improved matters - no more rattles from the plastic rain shield, and significantly less boom and resonance. Sounds sweet as anything now

Oh and I don't run any rears, to allow the sub to vent into the cabin. Might try putting some spare Rockford Fosgates in there though, running off the head unit, just to see what it sounds like...

Just yet another 2p

Richard

ps Hi Nick - glad to see you're still being the voice of wisdom in this forum

[Edited by Re-Bitten Hero - 1/10/2003 3:34:40 PM]