[DerAlte]

Originally Posted by nura

What is closed cell foam & how does one use it to sound-deaden the doors?

Closed cell foam is the one where the air bubbles are closed, giving it a glossy look as compared to open cell foam, where the holes are open and interlinked like sponge.

Not a good idea to use closed cell foam to damp doors, since closed cell foam sheets are not adhesive backed and it will be dificult to get uniform contact across the metal expanse. CCF works best when one can sandwitch it beween carpet and metal (floor), metal and metal (like number plate) or metal and plastic (stuffing).

For damping doors it is better to use adhesive backed butyl rubber (or butyl+asphalt) sheets like the Fonomat you have. Costlier than CCF, but does the job properly.

[nura]

Vielen Dank, DerAlte. Would also appreciate your comments about the application of clay to the doors to add mass & stiffness as well as smoothen out the surface before pasting on the Fonomat.

[DerAlte]

Originally Posted by nura

Vielen Dank, DerAlte. Would also appreciate your comments about the application of clay to the doors to add mass & stiffness as well as smoothen out the surface before pasting on the Fonomat.

Gar kein Problem, @nura! IMHO adding mass would be an overkill to the car panel vibration problem, and clay is too brittle for automotive application.

Adding stiffness would be a matter of sticking steel / alu L- or T-sections with Araldite or cyano-acrylate glue, but the even that would be an overkill for small car panels (except bonnet, roof and floor, all panels are < 0.6 sq.m. flat area - too less to bother about stiffening).

Damping sheets such as Fonomat are able follow contours pretty decently, IF the adhesive surface is heated with a hot air blower AND the sheet is pressed on uniformly, preferably with a small roller. The only surface preparation required would be de-greasing (thinner)/ de-rusting & de-flaking (sandpaper).

@Autophile mentioned somewhere yesterday that the best time to do it in an older car is when it is stripped for painting. However, if you are not repainting the car, a little elbow-grease would suffice.

[nura]

Danke sehr! Would you recommend sealing the service holes in the inner door panel with aluminium sheets before pasting on the Fonomat?

[DerAlte]

Originally Posted by nura

Danke sehr! Would you recommend sealing the service holes in the inner door panel with aluminium sheets before pasting on the Fonomat?

Bitte sehr!
No, those holes don't interfere with or affect anything. Put the Fonomat around them.

The culprits are a. harness connectors & cables not fastened down (rattling; stick them down with masking or surgical adhesive tape) and b. large expanses of undamped metal sheet or plastic (vibrations; that's what the Fonomat is damping).

[rocksterraghu]

Originally Posted by nura

Was vaguely thinking of the Alpine CDA-9856 & would welcome your comments about it.

I have been using the HU for over 4 months now. I can confirm that it is a very good option for the setup that you've planned.

The HU looks great and sounds brilliant. Absolutely hassle-free in reading CD's and has all the features you would desire. I would definitely recommend it for your setup.

The cost of the HU was about 19,500/- with B&W and about 14,500/- without B&W. (Not too sure, please verify this data)

[nura]

@DerAlte - So there's not much to be gained in trying to convert the door into a leakily sealed box for the speakers?
@rocksterraghu - Thanks for your feedback. Which other HUs did you hear before you chose the 9856?

[vijay_k]

@nura: How much did you pay for Image Dynamics IDQ12D2V.2 sub & Audison SRx5 amplifier???


Vijay

[navin]

Originally Posted by DerAlte

Adding stiffness would be a matter of sticking steel / alu L- or T-sections with Araldite or cyano-acrylate glue,.

prior to the days of Dynamat etc... I used 1.5mm lead sheet. I had to take the doors of their hinges (Premier, Contessa) and lay them flat then use Araldite 242 (I think it was 242) to stick the lead sheets.

[rocksterraghu]

Originally Posted by nura

Thanks for your feedback. Which other HUs did you hear before you chose the 9856?

I have a Pioneer 5850 in my 800 which I've used for quite sometime now. I tried the 7950 for a day until my 9856 arrived, and in my opinion, the Pio by default has lower mids, I had to pump them up using the EQ (which I don't like doing often ).

I tried the Blaupunkt Bahamas MP46, it was good. Sony and Kenwood were not on my list since my friends keep complaining about read problems in some models (not to generalize, but did not want to take a chance ).

Hydrashok suggested that I choose the Alpine from his personal experience. And I am also a little inclined towards Alpine, due to its finish and SQ - so Blau was my second choice and Alpine the first.

[nura]

@Vijay K - The sub was 14K & the amp 31K approx.
@Navin - Did you cover the service holes in the inner door panel with these lead sheets? How difficult was it to get the sheets off when door contents needed to be accessed? Some people use silicon adhesive, which can be easily removed. Any idea what brand name it is sold under?
@Rocksterraghu - Thanks a lot for all the useful information.

[DerAlte]

Originally Posted by nura

@DerAlte - So there's not much to be gained in trying to convert the door into a leakily sealed box for the speakers?

If one goes by the mid-bass driver's T-S parameters (most common ones come without the params; Navin has all the formulae hard-wired in his brain) one will find that the door cavity volume would anyhow be too large for the driver that you are putting there - for the relevant frequency band (80-4K) - almost reaching IB proportions.

While there is something to be gained by matching the Vas with Vb (cavity volume) for a high quality driver with declared T-S parameters, for most others it would be a futile exercise - low benefit/cost ratio!

Originally Posted by navin

prior to the days of Dynamat etc... I used 1.5mm lead sheet. I had to take the doors of their hinges (Premier, Contessa) and lay them flat then use Araldite 242 (I think it was 242) to stick the lead sheets.

Must have been hell of a lot of work! Try doing that to J/K econo-boxes, and the doors will start hanging down in no time.

Safari has damping already in some parts: some kind of (looks like) asphalt-based lining in the door outer panel. Not enough, since only 25% has been strategically covered. I finally bought some American Dynamics sheets last Friday - should make out some time to get it in now.

[navin]

Originally Posted by DerAlte

If one goes by the mid-bass driver's T-S parameters - most common ones come without the params....

Must have been hell of a lot of work! Try doing that to J/K econo-boxes, and the doors will start hanging down in no time

1. if you look at T/S specs of speakers made for car audio you will see that the Qts is rather high. this allows them to be used in leaky boxes (QL>15) and still provide a sembalnce of bass. Stuff in the same woofer in a less leaky box and the bass will tighten.

2. Der Alte, this was when I was single and involved in audio. Today I just live vicarously.

[navin]

Originally Posted by nura

@Navin - Did you cover the service holes in the inner door panel with these lead sheets? How difficult was it to get the sheets off when door contents needed to be accessed?

Actually no. I cut the lead sheets and did not damp the entire door panel 100%. I just covered the parts I felt would be the most resonant. The contessa was more difficult as the winder would interfere.

[nura]

I was making some inquiries re Alpine HUs & was told that the 9856 & 9857 are obsolete. The dealer recommended the 9881, 9883 & 9885. How do these newer models compare with the older ones?
Thanks in advance.