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Hi Guys

After 2 weeks of owning my NC2 with PRHT hardtop I am loving driving it with the top down, but concerned about the road noise inside when the top is up. At first I suspected wheel bearings or brakes, but everything is OK and am now wondering if it really is just road noise from the tyres echoing around in there. It's quiet until about 20kph and then almost like someone has thrown a switch - the rumble starts. If I put the top down the noise is not noticeable at all, which of course is how these cars are supposed to be dríven. I suspect it's just the road noise resonating around inside and wonder if some sound deadening panels might help in the boot, under the carpets etc. ?

Can someone confirm that this is normal, do other owners notice excessive road noise or maybe I have a problem elsewhere which needs investigating. i guess the best way to find out is to have a ride in someone else's NC with the top up and compare.

I appreciate your responses, so thanks in advance.

Place a couple of cushions of a rug into the boot and see if it makes a difference. There is a thread somewhere in here that mentions same.
Greg.

Tyres make a big difference..some are just plain noisy and other get noisy as they wear.
I put some foil backed sound damping mat through the boot area and under all the plastic behind the seats.
I also put some on the wheel arches in taht same area behind the seats.
The difference is quite amazing with noise levels substantially reduced for a weight penalty of about 10kg it's well worth it!

Thanks, Rob The cushion/ blanket thing was just a jump off.
Greg.

I don't have an NC, but my NA6 & NB8A suffered similarly. As mentioned, adding the Butyl/Foil insulation makes a vast difference to comfort. It's a very easy and clean product to use. I used Dynamat in my previous NA and can recommend it, but it's very expensive. In my NB8A I used a product from ebay from Hong Kong and found that it was almost as effective for a much reduced cost. On a recent trip in our SE, although by far the quietest of the lot so far, we still found that different road surfaces created a lot of tyre noise and "rumble", so at some stage I will probably insulate the boot, rear deck, behind the seats and around the wheel arches etc. Insulating inside the doors is a bit fiddly, but makes a big difference and has the bonus of helping the speakers sound better as well

I picked up my mat from Car Builders in Qld on Ebay.

Saved that seller for future reference .... thanks ...

It seems from your replies like the noise is normal then, I will look at getting some sound deadening material and insulate the boot, under carpets, doors and inside the hard top storage area between the boots and the rear bulkhead. Jaycar seem to have a couple of options for reasonable money, I will also look at flea bay to see what's on offer there. i will take an ambient sound level measurement before and after to see ig there is much difference just for the hell of it too.

thanks.

As Rob mentioned, tyre choice as well as tyre wear makes a big difference. I have two sets of wheels - the stock SE 17" Racing Harts have Dunlop Sport Maxx tyres and are much quieter than my 15" Racing Harts with Bridgestone RE002's. The Bridgestones have good tread left, but have become noisier as they wear.

Dont jump to conclusions.
Ncs with prht are not excessively noisy. Thats pretty easy to support as a statement
You should not need extra sound installation.
Sound deadening in my view is not quite so easy to do and get good results.
Tyres are often a cause of noise. Tyres are not all equal on noise.
It would be a good idea to take a ride in other ncs with prht and that should tell you if yr car is extra noisy

It's not just whether it's "extra noisy" over other NC's, but whether it's acceptable to the individual. These are not like most modern cars with heaps of thick and heavy sound absorbing underlay and sprayed on bitumen.

Each to their own, but I personally very much enjoy my comfort these days. Just because I also enjoy driving a sports car that is also a convertible does not mean I have to accept spartan and noisy. It's not my thing any more and with the materials available it's also not necessary.

The foil we are discussing is applied to areas out of view and is very easy to apply - basically peal and stick - and is very effective in making the vehicles much quieter and more comfortable for both everyday use and longer trips. Yes there's a little weight penalty, but if that's a concern, the carpets themselves are already an issue and noise is not.

I find our car (NC1) with the (soft) top up is reasonably quiet. Maybe it's a PRHT acoustics issue. The NC2 also has that stupid intake resonator/amplifier thing which, I imagine, would also contribute to interior noise.

Roof up my PRHT NC2 is a little boomy, but I must say that after moving away from the OEM 050A's everything got a lot quieter. Mr M's interjection is only an opinion, as he does not own an NC. Play with some things in the boot and then look at what Rob has done. (I am sure that there are images of a sound insulation project in here somewhere).
Greg.

Definitely an design issue.

Before people spend money on tyres,matting,etc they need to check the rear drains to make sure that the one way flap is still there and operating correctly.

I didn't bother with the matting after i did this. ( Keeping the drains working correctly can reduce noise and stop water ingress into the cabin)

The flaps can be damaged or direction reversed if they are checked by poking and prodding from the drain holes underneath.

Also dirt and debris can hold the flap open letting all the road noise into the cabin.

Best way to check, Park the car on level ground and open the roof stopping mid-cycle.
Once done you will see what looks like a spoon drain on either side under the back window ( It has a grate covering the opening )
Clean any debris from around the grate and pour in a small bottle of water ( It should drain straight through onto the ground just in front of the back wheels)
If the water pools then the drain will need cleaning

Best two things to use are a trombone snake pipe cleaner or if you are cheap some whipper snipper cord.

"Always start at the top and work down" so you don't damage the oneway anti vermin flap.

The drain hole is not in the middle ( Slightly offset to one corner )

It's a royal pain to do but once you figure the angles of poking it does get easier.

While the roof is open also check the two bits of hose tucked under the back window are secure otherwise you may end up with water in the cabin.

And if the drains are working properly you will get wet shoes.

tez

Do PRHTs have drains, or is it only the soft tops?