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PaulG View Drop Down
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Direct Link To This Post Topic: Dynamat in yer Doors?
    Posted: 06 Feb 08 at 10:21

Hi Guys,

I searched, but did not (quite) find!

Still on the stereo install subject.  Has anyone fitted Dynamat (or equivalent) in their cab doors, and does this pose a potential problem of absorbing and holding moisture? (Moisture = rust later on!)

Meanwhile, I will go and research this stuff on the web!

PaulG

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Direct Link To This Post Posted: 06 Feb 08 at 12:52
I used that flash banding type stuff from diy stores, heated it up with hot air
gun and stuck it down - it don't shift and makes a big difference to the
resonance in the doors, much cheaper than dynamat and does the same
job.

Its designed to stop water getting beyond it on roofs, so it wont let any
water past it in your doors!
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Direct Link To This Post Posted: 06 Feb 08 at 14:00
I have used the same stuff Monsho has mentioned in several past cars and about to fit it in the bus too. Works a treat!
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Direct Link To This Post Posted: 06 Feb 08 at 22:58

Sorry to be a dullard boys - what's flash banding??

I'm doin a speaker installation on my van soon (sony 110w door speakers with matching amp and head unit) - should I consider this while I'm at it?

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Direct Link To This Post Posted: 06 Feb 08 at 23:01
its the self adhesive bitumen stuff you get for roofs from B&Q and the like -
just pop in and say 'have you any flash banding good sir' and if they're worth
their salt I reckon they'll come good!

makes a big ol difference....
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Direct Link To This Post Posted: 06 Feb 08 at 23:08
nice one - cheers!
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Direct Link To This Post Posted: 07 Feb 08 at 20:56

Motor factors sell sound deadening pads for a couple of quid each.

Caravelle, well anything other than transporters already have it in from the factory, it's only the lower spec commercials that don't have it, thats why the doors don't sound all rattly on passenger carrying vans.

if you put some it it will kill loads of noise and your doors will shut with a nice thud.

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Direct Link To This Post Posted: 07 Feb 08 at 21:03

i used this stuff.

Acoustically better than Dynamat and a damn sight cheaper!

 

http://www.customaudiodesigns.co.uk/soundproofing/t60.htm

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Direct Link To This Post Posted: 10 Feb 08 at 15:08

You used to be able to buy sound deadening in a spray format. Were two colours depending on thickness I think. Red/blue? Came out like a coating of rubber

Me personally would go with the flashing and any part you cant get into or stiock to cover with the spray.

 

Hopefully its still available

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Direct Link To This Post Posted: 11 Feb 08 at 10:39

Update - Well I went for the Dynamat soution, basically because they had it for sale in Halfords, one ICE 'specialist' in Coventry did not have a member of staff who had heard of the concept (only a fellow customer!), and the traffic was too heavy to get to the only other place nearby that I know - so I decided to just go for it!

I have stuck half of the sheet to the inside of each cab door skin, in the front half of the door, as high up as I could reach and the mat would fit.  On reassembly I would say that the sound is better controlled, and it somehow gives the speakers a chance to work better.  It does not however make any noticable difference to the amount of sound that 'leaks' out through the skins to outside.  So people still stare at you at traffic lights etc!

So there you have it.  You pays your money, you takes your choice.

Next step.  Speakers over the R'N'R bed.

See you,

PaulG

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Direct Link To This Post Posted: 11 Feb 08 at 11:32
Guys
Bear in mind that materials like Dynamat do NOT deaden sound.

[techie-mode]
Dynamat, flashing tape and all other bitumen-type materials simply increase the mass of the panel they're attached to, which serves to lower the resonant frequency of the panel. If sufficient material is attached (generally not an awful lot) then the resonant frequency is lowered below normal listening frequencies and the panel stops "ringing" when you play music on the stereo. It also reduces the "thrumming" noise, when you're driving along
[/techie-mode]

In real terms, Dynamat stops your bus booming. It's brilliant on any flat surface more than 6"sq or so, to stop it resonating. What Dynamat et al does NOT do is reduce the amount of noise being passed to the outside world

If you want to do that, you need to increase the sound-absorption of each panel - which generally means either sticking egg-trays over the inside of every panel or covering all Dynamatted areas in self-adhesive foam. NOT advisable, as this will increase the moisture retention in our precious busses.

Granted, if you put more than one layer of Dynamat etc on a panel, it will have an effect on the sound absorption, but at the expense of a lot of extra weight.

My advice would be:
Dynamat is heavy, expensive and over the top for a bus that is essentially an underpowered, noisy box on wheels (that I love and wouldn't be without
Foam-based panels are cheaper and lighter, but the risk of water-retention is too great for me to recommend
Flashing tape is cheap, flexible and light. It can be applied to pretty much any flat area and has a significant effect on the resonant frequencies of the panels. You can put two layers on (in a criss-cross arrangement for greatest effect) if you're really keen on resonant-noise reduction, but do keep in mind that this won't directly affect ambient noise levels
Ambient noise can be most significantly reduced by concentrating on:
1) the storage areas under the front seats (these resonate like a wotsit - I have pillows in mine at the moment and the difference is HUGE)
2) Flashing tape on the angled section behind the rear seat. This will reduce resonance from the engine. Ideally, build a cupboard under your rear seats as well - this will give you storage and increased baffling from the noise
3) Sound-deadening the doors. This will reduce wind-rush a lot
4) If your engine-lid is exposed, you can benefit by covering this in carpet, but make sure you haven't got any water-leaks in the back first ;)

Final recommendation is a product recommendation. Second skin make a water-based sound-deadening "paint" called Spectrum, and a thicker version called Sludge. I have used Sludge on my bay window to reduce resonance on the roof and door panels. It can be daubed on with a paintbrush, dries in about 10 minutes in warm weather and is solid in a few hours. It's got lots of rust-inhibitors in too, so it's old-bus friendly. It's cheaper than Dynamat and even flashing tape, can be splodged anywhere you can get a brush and is very good at reducing resonance

You can get it from http://www.caraudiodirect.co.uk and no, I don't work there ;)

Richard
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Direct Link To This Post Posted: 11 Feb 08 at 11:51

Hi Globbits/Richard,

Good post mate!  What you've written there brings together a lot of the salient points and puts them into one place.  Good for future reference!

I must say that I am a little confused by Dynamat's products and their claims about them (if I understood the correctly).  They seem to suggest that the foil covering on the mat blocks sound transmission.  But then when I broke open the pack there was no foil on the mat.  Must be a different Dynamat product?  They aslo suggest you stick it to the back of the door cards.  It's too thick, the door cards wouldn't fit back properly!

You are right about the risk of moisture retention in anything more foam-like that the Dynamat, or egg boxes or whatever.  That's why in the end I just went for the Dynamat and be done with it!

My T3 is a camper, so R'n'R bed in the back, but the pillows under the cab seats looks like a simple thing to try?  Where I work I have a lot of packing materials to dispose of... might be something crop up there that I could use...?

Could you expand a bit on " 3) Sound-deadening the doors. This will reduce wind-rush a lot ".  Are we talking draft exclusion?

Thanks again for all the info in your post though.  I think it should help others in the future.

PaulG

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Direct Link To This Post Posted: 11 Feb 08 at 12:10
Hey Paul

My bus is away having a recon engine fitted (bless those DG's and their head gaskets ) but as soon as it's back, I shall be soundproofing the whole thing and putting a reasonable stereo system in. I'll put a log of my progress on the tech section, so you can keep an eye on what gets done and how

For reference, Dynamat do two main versions - "normal" Dynamat and Dynamat extreme. From memory, the major difference is that the Extreme version is:
  • Slightly lighter
  • Foil-backed, for greater sound-reflection (reduces noise passed to the outside world)
  • Twice the price
Regarding sound-deadening doors, there are a number of things to focus on here:

1) Resonance - Reducing the ringing from the door panel. This is "simply" a matter of putting Dynamat/flashing tape onto the flat metal areas of the door

2) Ambient noise - Reducing the noise from the outside world. This is essentially wind-rush, from the air going past the door as you're whooshing along, not draft-exclusion. Again, load-lining the panel (putting on Dynamat etc) will do as much as you can about this

3) Reducing speaker resonance - If your speaker's not solidly mounted, when it moves the cone to produce noise, some of the movement will be lost, in shaking the speaker itself. You lose bass more than you lose midrange/treble, making the sound in the front weak

This last one's a tricky one, as the speaker is mounted to the door card, which is essentially a flimsy bit of hardboard. Dynamat's advice, about sticking the material to the door card itself, is to resolve this situation. If you make the door card heavier (or rather increase its mass) then it won't wiggle as much when the speaker attached to it wiggles. End result, greater output from the speaker.

Of course, the problem is that the door card is attached to the bloody door and, if you put a ton of Dynamat behind it, you can't fit it back onto the door! Solutions here include:
  • Glueing further sections of MDF in front of (or behind, if you can) the door card, as close to the speaker as you can. This will stiffen up the panel, without dramatically affecting the weight
  • Sticking Dynamat etc to the back face of the metalwork around where the speaker is fitted in the door card and/or screwing the speaker through the door card into the metalwork. These give the speaker something more solid to resonate against
  • Making new door cards out of thicker timber and/or making full speakers boxes to hide into the doors, out of fibreglass. (This will be my weapon of choice, but only because I'm a stereo nut and am going to try and fit two pairs of 6.5" speakers into the doors )
Bus should be back during the week. I'll start a sound-deadening and stereo-installation thread as soon as I get on the case!

Richard
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Direct Link To This Post Posted: 11 Feb 08 at 14:47

Thanks again Richard, you are obviously way ahead of me on this subject.  Re: Door card flimsiness... I wonder if a thin sheet of metal in the sandwich between the speaker cone and the door card would help?  It could be glued to the back of the door card and that would stiffen up the imediate area of the speaker?  I think Dynamat would be too thick, although I noticed they sell a so-called 'Door Kit'

At the end of the day, there is only so much you can do isn't there?  My intention to add a pair of speakers to the rear of the camper should enable me to take some of the emphasis away from the fronts (presently the only ones fitted).

How about seperate tweeters, high in the doors.  Can these be retro-fitted to existing speakers (with a crossover circuit of course) do you know?  Or, do they tend to be part of a speaker 'package'.

Ta for now,

PaulG

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Direct Link To This Post Posted: 11 Feb 08 at 16:00
I'm only ahead because I've been playing with car audio for far too long  My T3 experience is still very new! (Only had mine 6 months now) I'll answer your questions as best I can though

Regarding the door cards bear in mind that what you're trying to do is present a more solid base to the speaker. Whether you achive this with bits of wood or metal glued to the back of the card, by screwing the speaker to the metal frame of the door or by putting Dynamat/flashing tape on the back faces of the metalwork the door card clips to, all you're actually doing is making it more solid. What you won't be doing is making a silk purse out of a sow's ear. Bear in mind that the factory-fit speakers are old, small and low power and quality. They will never shake your fillings out, no matter how much solidity you give the door

My advice would be to treat this as two separate exercises. First, get the van sound-deadened to a point where you're happy with the background noise and boominess (or lack of) and only then consider what you're going to do stereo-wise.

Which leads nicely into your second question. Yes, you can get aftermarket tweeter kits, which will allow you to connect a tweeter to your existing speakers. But since they cost around 15-25 and you can buy a component set (midrange and tweeter) for similar money, consider going the whole hog and treating yourself to a nice but inexpensive set of components. You won't regret it

To give you an idea, this is my plans for the bus so far:
  • Flashing tape into storage areas under front seats (reduce resonance, as described earlier)
  • Build fibreglass "boxes" to fit into the storage areas (giving more soundproofing and more storage in one go)
  • Flashing tape across the boot floor and angled section (already done this - made a big difference to engine "roar")
  • Second skin Sludge into door panels - probably two layers (reduce resonance and exterior noise inside the doors)
  • Make new door cards out of 3mm or 5mm ply (for a more solid speaker-mounting)
  • Build fibreglass box into hole at the base of the door, for 6.5" midrange speaker (f/g box is to improve speaker response and keep it protected from the worst of the water ingress through the door)
  • Build MDF/fibreglass boxes to fit underneath rear seat (mine's a Caravelle) for subwoofers (gives extra sound-deadening too)
  • Sit back and investigate the noisiest places left. I expect these to be the floor section in the middle, followed by the tailgate, then the sliding doors, then the front panel behind the dash
That should keep me going for a month or two!
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Direct Link To This Post Posted: 11 Feb 08 at 16:49

Sounds like you are going to be busy!  .  What you probably didn't know (from other threads), is that I have just installed a Blaupunkt 'London' Headunit, and Blaupunkt THx542 speakers (130mm Two-Way co-axials, in the cab doors) plus the Dynamat as well now of course.  The headunit is wired to the leisure battery, and the speakers have 2.5mm 'Bluespot' speaker cable (instead of the Blaupunkt supplied thin stuff.  Blaupunkt don't seem to make seperate tweeters, although there are already tweeters in the THx542's of course.  With hindsight I should have bought the THc542's (with seperate tweeters) instead, and may still upgrade to those later on, if I'm still not happy.

I plan to put Blaupunkt THx693 6 x 9's or THx572 5 x 7's above the bed, in the bottom of a wooden overhead locker that I usually have filled with towels etc.  Firing downwards.

The beauty of the Blaupunkt headunit (IMHO) is that, 1) it fits the DIN slot's 150mm depth limit (the limit is an issue on a watercooled vans where VW robbed some space for the water filled heater parts when they went from aircooled to watercooled) and 2) it's vaguely relevant to a (German) VW vehicle, and 3) they are at least half-decent quality, 4) it has the features I wanted.

So, in summary, I'm way ahead (I hope!) of factory fit gear, with some idea for where to go next, and some acceptance that I may have to rethink the door speakers.  The Dynamat 'experiments' are just that really, and the whole install is a project within the overall project of restoring and improving the van.  Plus, there is some notional limit to my budget!

It's great trading these posts with you, you obviously know your stuff!  Hope to meet you somewhere some day when the shows get going.  I might have finished the install by then!

Have a look here:- http://www.bluespot.co.uk/default.asp and you can see what I'm talking about, Blaupunkt-wise.

Cheers,

Paul.

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Direct Link To This Post Posted: 11 Feb 08 at 17:11
Ah, the joys of axial speakers! Brilliant if you've got limited space and surprisingly good sound, if you aim them properly. As you've found though, their limitation is their benefit - that the tweeter's part of the main speaker!

Don't worry though - all's not lost. Blaupunkt's not a bad place to start (I used the Blaupunkt Casablanca CD and USB head unit for ages) but I wouldn't carry on with Blaupunkt speakers - there are much better options for your money. We'll come back to speakers in a bit though

Sounds like your next step is to reduce road noise - the storage below the front seats and the engine lid area being the major contributors. Once you've done them, get someone else to take the van for a drive in a car park, with you able to move around and find the noisy bits. If you find the noisy bits aren't too intrusive then yay. Otherwise, deal with them accordingly.

Once you're happy with the background noise levels, then it's time to consider your speaker setup. My first point about that would be to ask what you want from rear speakers. If you're after music in the back of the van, for passengers or for while you're "relaxing" in bed then I have nothing against 6*9's. BUT (and this is a huuuuuuuge but) if you're after rear speakers to aKind sir, you have an e-mail.ent the fronts while you're driving you do NOT want 6*9's. Really.  Really really.  Really really REALLY

6"*9" speakers are a compromise speaker. They have a reasonable surface area main driver so they can produce fair quantities of bass and midrange. They then have one, two or three tweeter units of varying sizes, to provide high frequency stuff. When listened to at close-range (like in the front doors) the bass and midrange frequencies are pretty strong, so the speakers sound pretty potent. The problem is that, if you put them at the back of the van (or even the middle) the lower frequencies drop off quicker than the higher frequencies. So you end up with masses of tinny rubbish coming from the back which just gives you a headache

If you want to make your system sound better in the front of the van, for your own pleasure when driving, get a sub. Really. What it will do (when set up properly) is complement the lower frequencies from the front speakers, making them sound stronger. It won't drown out the music, nor make you deaf.

Honestly, don't bother with rear speakers, don't bother either with a massive or expensive sub. Just get a small one you can build into a cupboard. You won't regret it

On the other hand, if you want music in the back for chilling out to, go ahead with the 6*9's - just make sure they are NOT aimed towards the front of the bus

Richard
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Direct Link To This Post Posted: 11 Feb 08 at 20:52

Good to see a nice indepth thread with some tried and tested advice, Thanks Guys.

 

What about 6x9's in my parcel shelf, innit

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Direct Link To This Post Posted: 12 Feb 08 at 09:09
Another point which has not been considered here is how to get the most bang for buck from your sound deadening material.

As Richard said the bus is a large resonating box and what you are trying to do is kill the resonance.

In order to do this you should consider where the majority of your resonance is coming from.

THE WHEELS ARE THE MAJOR SOURCE OF RESONANCE IN ANY VEHICLE

So if you concentrate your efforts around those areas you are likely to see the biggest improvements . Working your way out from the wheels is the best method.
So do the wheel arches first and underseat boxes then the upright panels nearby ie the doors and then work your way on to the larger panels between the B and C posts.

Pretty obvious when you think about it really.
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Direct Link To This Post Posted: 12 Feb 08 at 09:45
Good point Mr B

This is the argument behind putting pillows in the under-seat storage areas. It should be said though, when I changed from the nasty tyres that were on there to some softer compound "normal" tyres, the road noise dropped off dramatically!

As Mr Bricolage says, the largest source of noise ingress is from the tyres (assuming your engine/exhaust is in good nick). Focus on those areas to reduce exterior noise, but you're looking to absorb noise here, so will need to use foam/carpet/pillows etc. Bear in mind that whatever you use will possibly retain water near your precious metal bits. Use and/or rust-treat accordingly!

Richard
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