DIY Door Speaker Upgrade & Sound Deadening Treatment for 2001 Pathfinder

[mda185]

I am in the process of upgrading every part of the factory Bose sound system. In a previous post, I explained how to upgrade the head unit and retain the factory Bose amplifiers and speakers. This is a worthwhile upgrade and results in much improved bass and treble response while still using factory speakers.

My next step is to apply sound deadening to the door skins and fabricate MDF speaker baffles to enable me to install high quality door speakers. My plan is to test a variety of DIY and commercial door speakers before I decide which design to use. The factory door panels have to be modified if you want to fit the largest possible woofers in your doors. There are three reasons this is necessary. First, the OEM door skins are made of thin sheet metal and they will flex and vibrate a lot if you install a woofer with a heavy, strong magnet. A speaker baffle made out of medium density fiberboard (MDF) will help to stiffen the sheet metal and damp out door panel vibrations. Second, the mounting depth is restricted because the window glass is only about 1.5” behind the door skin with the window down. A proper MDF baffle will increase mounting depth enough to mount any good 6.5”-8” woofer. Third reason is that the OEM door skin speaker hole is not large enough to mount a decent woofer. Cutting this sheet metal is not a good idea because it already has problems with excessive flex and vibration with heavier speakers. A well designed MDF baffle will solve all of these problems.

Fortunately, the R50 Pathfinders have flat door panels and this makes it relatively easy to make MDF baffles to replace the original speaker mounts. There are two possible upgrade paths. It is possible to make a speaker baffle that fits underneath the OEM door trim panel. This requires cutting an MDF baffle based on the shape of the factory speaker bracket. It has to be 1.5” thick and has an irregular shape to fit under the plastic speaker grill.

Here is a picture of an OEM front door speaker and amplifier module. The amp is the black box next to the speaker. The actual woofer is only 5 1/4" diameter. Lots of room for improvement here.

Here is a picture of the backside of the OEM door trim panel with its irregular cutout.

Here is an an example of a speaker baffle I made to fit under the door trim panel while experimenting with my Pathfinder. I ultimately abandoned this approach because I wanted to try larger woofers.

This approach still has limitations that caused me to reject it. Speaker mounting depth is limited to about 2.75” and speaker diameter is restricted to 6-6.5” max. This approach also does not add as much mass to stiffen the door and lower its resonant frequency. I know of at least one Pathfinder owner that has successfully upgraded to Dynaudio 6.5” speakers using the approach above. I prefer to make a larger baffle and completely replace the factory Plastic speaker grill and door pocket assembly. I started by tracing and cutting ½” and ¾” thick MDF pieces that match the outline of the OEM speaker grills. I then glued 4 of these together to make a baffle 2 ¾” thick.

Here is a picture of the OEM speaker grill/door pocket with one of the new baffles underneath it for size comparison.

Here is a picture of one of the new baffles that should give you an idea of how deep they are. They are about the same depth as the OEM speaker grill.

This baffle is deep enough to handle any reasonable 6.5-8” driver and it has a lot of mass. My first attempt is based on making a baffle that replaces the factory grill but still retains the factory door pocket. This will require cutting the door pocket assembly and butting it up against my new baffle. I am still experimenting with applying a finish to this baffle. I have gotten decent results with generic primer/sealer, SEM texture paint, and SEM satin black paint. It passed the wife acceptance test with this combination and that is probably the toughest test I am going to face. I will post a picture of the painted baffle in a day or two. I can't find the camera right now.

Before mounting the baffle and testing speakers, I added sound deadening to the outer door skin. I started by applying a butyl based vibration dampener called Brown Bread. This works on the principle of absorbing vibration in the sheet metal and converting it to heat in the butyl rubber layer. The effectiveness of the sound dampener is based on the thickness of the butyl layer, the quality of the adhesive, and the thickness of the aluminum layer. Low cost sound dampener like Brown Bread has a very thin aluminum foil outer layer. Higher quality products like Damplifier Pro from Second Skin have much thicker aluminum layers. It is very hard to measure the difference between products like this in terms of SPL noise reduction but I will attempt to at a later date. The one advantage of using the less expensive products is that they are easier to apply to the entire door skin if you are also trying to get it to act like a sound barrier. Pros will tell you this is not necessary and not cost effective.

Here is a picture of the driver's door with a layer of Brown Bread sound dampener applied to the outer door skin.

The next stage of sound deadening is extremely important and often overlooked by DIY installers. I applied a ¼” layer of closed cell foam to the aluminum side of the sound dampener. It is extremely important to use closed cell foam because this will not absorb and retain water. I used spray contact cement to attach the foam to the aluminum. The foam acts as both a sound barrier and a sound absorber. It makes a dramatic, noticeable difference in the ambient noise coming from the door. I did the driver door first and left the passenger side alone. My wife drove the car and immediately noticed a difference between the two doors without knowing what I did. I have not been able to measure a difference in SPL from the two doors but the difference is audible. I tried measuring the ambient noise level coming from both doors by placing a microphone down near the speaker opening. There was no difference at any speed. My theory is that the noise that would normally couple into the door glass is being absorbed by the foam. This also explains why my wife is so sensitive to the improvement. Women retain their high frequency hearing much longer than most men and glass is a better transmitter of high frequencies.

Here is a picture of the door with the closed cell foam applied over the Brown Bread.

The next step is to replace the OEM vapor barrier with mass loaded vinyl sheeting. This is available from McMaster-Carr by internet order. It is part number 54665T22 and it comes in 54” wide sheets that are sold by the foot. Part # 54665T22 is 50 mils thick and has ½ pound of mass per square foot. There is also Part # 54665T32 which is 100 mils thick and has 1 pound mass per square foot. The thicker MLV is more difficult to work with but is more effective at blocking noise. I was not confident that I could fit it under my door trim panel and went with the thinner version. If you think you have the room, by all means use the thicker version. It does not cost much more.

I made a trace of the OEM plastic vapor barrier using craft paper and taped the template to the MLV. This makes it much easier to cut out without losing your line.

Here is the MLV applied to the door with the OEM Bose speaker back in place. I had to make the sound system function for my wife to drive while I continued experimenting with paint finishes on the new baffles. Next up, pictures of painted baffles and sound measurements of an assortment of woofers.



Modified by mda185 at 3:38 PM 11/7/2009

Modified by mda185 at 6:19 PM 11/15/2009
Modified by mda185 at 6:22 PM 11/15/2009

[lino]

Excellent writeup! Thanks for sharing . When I get some of my more pressing mechanical issues sorted out, I'd love to work on my audio. Just out of curiosity, how much of a difference do you think a product like Dynamat or similar would make compared to what you've done?

[slickroger]

Looks good.

nice write up

[mda185]

I actually don't like Dynamat. I think it is overpriced and not as effective as the better butyl based sound deadeners like Second Skin Damplifier and Damplifier Pro. If you want a lower cost alternative look at Raamat or Brown Bread.

The original Dynamat is based on an asphalt dampening layer that smells and does not outperform the butyl rubber products. I think they make a butyl rubber product now but I have not tried it.

I will post some pictures comparing Raamat with Damplifier Pro in a few days.

[slickroger]

Awesome I really want to do this but find Dynomat way out of my budget considering how much I will need to do a good complete job

[mda185]

I have some pictures of the test baffle I made with paint. I used a coats of white primer/sealer with sanding with 120 grit on a random orbital sander between each coat. This was followed by two coats of Krylon satin black but I was not happy with that look. I painted it with two coats of SEM 985 Texture Coating and two coats of SEM 15243 satin black Color Coat. This combination looks very good. The pictures don't do it justice. I think I can do better but I am satisfied with this first experience with the SEM products. They really are a step up from Krylon and Rustoleum paints you can get at HD and Lowes. The SEM color coat is a flexible paint also suitable for painting plastic and vinyl. I have used it to refinish some 20 year old BMW door panels with excellent results.





Here are some pictures of 3 of the drivers I am going to evaluate for door mounting in my Pathfinder. The PPI 356CS is a cost effective coax solution if you don't want to do separates. It is based on a very good ADS 6.5" speaker and has a fairly sophisticated crossover design. (ADS and PPI are owned by the same mother company now.) The tweeter can be mounted separately if you don't want to do coax. The quality of the crossover filter is far above anything from I have seen from mainstream car audio brands like Pioneer, Kenwood, Sony, Alpine, etc. I picked this pair up for $129 on Ebay.



The Dayton RS180 7" mid bass is in the middle. It has a respectable magnet structure, aluminum cone, and well designed cast frame. This is a very popular mid bass driver for the DIY crowd in both home and car audio. It won't play as low as the SLS 6 but it has better response above 1000 Hz and is easier to mate with tweeters. This also is a higher quality driver than the usual car audio suspects. It usually sells for around $40 each at Parts Express. The Peerless SLS 6 usually sells for around $50 each and is probably the most powerful 6.5" driver available for car audio period.



Magnet structures on the Peerless and Dayton midbass drivers are robust. Notice the large bump plate on the Peerless SLS 6. This is more like a subwoofer in construction and is designed to move serious air for a small driver. That is why the baffle needed to be strong and deep.





Next up, I will show how I mounted the baffle to the door and start taking some speaker measurements. I am going to experiment with several different midbass drivers. Progress would have been faster but we have been having monsoon conditions in NJ. Every time I have had a day off from work in Oct and November, it has rained.

Modified by mda185 at 7:00 PM 11/15/2009
Modified by mda185 at 7:07 PM 11/15/2009