Total Sound Makeover - Sound Deadening, Speakers, Processor, Amp, and Subwoofer

Phase I – Sound Treatment and Speaker Swap-Out

Shortly after I picked up my Plug-In Prius in April, I posted the following on this forum:

I'm upgrading the sound experience incrementally, tackling the challenges in order of those that have the greatest effect to the least, while progressing roughly from measures that have the biggest bang for the buck to the least. At the point I get the sound I want commensurate with the money I've put in, I'm done, so the project will probably not make it to Step 5:​

​

1. The listening room. Far and away the worst thing about the listening experience is noise. No point plowing a lot of money into electronics to battle the noise without first doing everything reasonably possible to get rid of it. The largest part of the upgrade budget will be devoted to professional installation of resonance damping panels, acoustical isolation/insulation foam, and mass loaded vinyl sheeting. It is getting installed now.​

2. Speakers. If sound treatment alone does not improve the sound adequately (and I suspect it will not), I'll next be swapping out the factory speakers for reasonably inexpensive component speakers in the front (Alpine SPR-60C - $170), and coaxial speakers in the rear door (Alpine SPR-60 -$120). My guess is this is all I need, and I'll quit here.​

3. Sound Processor. Whatever aftermarket speakers we choose to put in these cars, they cannot match what the head unit was designed to power, so the next step would be a processor to adjust equalization, phase problems, and time delay. Several products seem well reviewed, but should the speaker swap-out alone not do it for me, I will be installing a JBL MS-8. It does a lot for $565​

4. Amplification. I seriously doubt that I will have any use for power in excess of the 18w per channel put out by the MS-8, but if I do, it will be a 5 channel Class D amp - probably the Alpine PDX-V9. 4 x 100w plus 1 x 500w. Why the 500w 5th channel? Just in case I need...​

5. Bass. I listen to music, and have no desire to annoy cars next to me at stoplights, so the mention of "subwoofer" makes me cringe. Still, there are limitations to what a 6 1/2" woofer can cleanly output at any power level. If I'm not happy at this point, I'm very comfortable working with MDF and fiberglass, and will fabricate a very shallow (~ 4" - the sub only needs .35 cu ft.) enclosure in the cargo area behind one of the wheel wells to house an Alpine SWR-T10.​

​

The project is now complete. Some of you asked for updates, so here we go:

First off, I think I was right assuming that the greatest improvement to the sound was to be gained by getting rid of undesired noise. There are numerous posts on how to use commonly available single product sound treatments such as Dynamat and its many clones, with satisfying results, but I was looking for a more comprehensive solution. The multi-tiered approach employed by http://www.sounddeadenershowdown.com/ made sense, as it’s damping product (CLD Tiles) was better engineered to solve the resonance problem, and the addition of closed cell foam and mass loaded vinyl were far better suited to blocking the low frequency noise (road, tire, wind, and engine noise), than single product solutions were capable of dealing with. The total material cost was around $700, and it was the most cost effective part of the project.

Bare Metal


CLD Tiles Installed

Thinsulate Acoustic Insulation Installed

Rear seat and floor area treated with Closed Cell Foam (CCF) - gray, and Mass Loaded Vinyl (MLV) -black

All layers of CCF and MLV were installed with Velcro in order to facilitate removal for maintenance




A typical buildup of CCF and MLV - these folks do great work















Front seat floor and footwell area

Another complex geometry build up in the right rear trunk area















Door Treatment





















Don Sambrook, of SoundDeadenerShowdown was willing to work with and oversee the installation by Hampstead AutoBody in Manchester, Maryland, so that was my first stop after picking up the car in D.C. They gutted the car down to bare metal, and did a fantastic job of applying the layers of material and putting it back together just like new.


Post job follow-up was excellent as well. I highly recommend both of these companies. I live in Georgia, and will probably make the long drive to use their services for my next car.

The result was incredible. I’ve never experienced this kind of quiet, not even in high-end luxury cars. The only noticeable sound is now environmental noise coming through the only untreated surfaces – the windows.

Since the car was already gutted, I had the shop run 12ga speaker wires and replace the speakers. I had them route all of the speaker wires through the storage bin behind the traction battery, in case I later wished to add sound processing and amplification. I fabricated tweeter brackets from 16ga steel using the attached file (Prius Squawker Mounting Plates.pdf), to help expedite the installation.


Total material cost to this point was about $1,000 (Speakers $300, Sound Treatment $700), and achieved about 95% of the sound improvement I was looking for. It would have made sense to stop here, as the law of diminishing returns hits hard. Next post will outline how I blew roughly $1700 getting that last 5%.

 

Phase II – Sound Processing, Amplification, and Subwoofer Installation

The sound from the upgraded speakers, along with the incredible sound treatment drastically improved the listening experience, but I wanted better equalization and more accurate bass than the stock electronics and replacement speakers could provide. The biggest challenge was adding bass, particularly fitting a subwoofer into what I wanted to be as unobtrusive an installation as I could manage. My goal was to minimize intrusion into useful space, while mitigating the eyesore of a sub enclosure as much as feasible. I chose the Alpine SWR-T10 for several reasons (sonically matched to the other Alpine R Series speakers, appropriate power handling and frequency range) but mostly because it was the 10” shallow mount sub driver that required the smallest enclosure space (.25 to .5 cu. ft.).

Before getting into the subwoofer enclosure construction process, first let me strongly recommend that any Gen III, non Plug-In owner order either a completed sub enclosure, or a plug from mgb4tim. See http://www.morspeedperformance.com/priusRight.cfm. They appear to be of the highest quality, will save you a great deal of time and effort, and are very reasonably priced. His products will not fit the Plug-In because the charging port intrudes on the right wheel well space.

I chose the left rear cargo space because it is smaller than the right, I did not need much volume, and it would free up the larger right rear space for useful storage. Also, it allows much easier access to the battery.

I fabricated all unsupported parts of the enclosure out of MDF or plywood in order to minimize resonance, so all visible surfaces were constructed that way. All hidden surfaces would be in contact with the trunk carpet, with much of them tightly radiused, or consisting of compound curves, helping to dampen any resonance, so they were a reasonable application for fiberglass.

I used aviation fiberglass materials, simply because I am used to working with them. Epoxy resin and Bidirectional cloth. They have the advantage of being incredibly strong, odor free and non-flammable, but are expensive. Total material cost was about $100 for all cloth, resin, ratio pumps, application tools and materials – probably double the cost of standard materials.

First step was fabricating the MDF rings, mounting the driver, and prototyping the placement based on enclosure volume. I measured volume with packing peanuts, and it worked out that at the point that I had about ¼” clearance between the sides of the driver and the enclosing carpeting, the volume was .29 cubic feet – lower than the preferred .35, but within the acceptable range of .25 - .50. Adding polyfill will increase the apparent volume to approximately .36, so all is well.

Next, I masked off the area, placed a nut can cut on a diagonal to create a recess for the terminal mount, placed aluminum foil (as a release), and applied four layers of bidirectional fiberglass cloth to create the rear of the enclosure.

Initially using cardboard templates, I then cut and shaped ½” plywood sides, and shaped the final exposed part of the box to resemble a leaf on its top and front profiles. More trimming fit the MDF/Plywood exterior box to the fiberglass rear shell.


One layer of bidirectional cloth to secure the inside of the fiberglass shell to the exterior of the MDF/Plywood box completed the initial assembly.

Cutting the terminal mount hole at this point helped greatly to see inside for the sanding, filling, and fiberglass work to follow.


Filling irregular voids with “micro” (a mixture of epoxy and microscopic glass bubbles) inside of the enclosure created a smooth surface to apply two layers of bidirectional cloth joining the inside of the MDF/Plywood box to the inside of the fiberglass shell.

Not a fan of heavy subwoofer assemblies accelerating toward my head during a collision, I placed a couple of plywood disks using flox (a strong mix of cotton fiber and epoxy) and two layers of bidirectional cloth. Sheet metal screws will bear on these to hold the enclosure tightly to the car’s frame.


I covered all areas exposed to the trunk with at least a single layer of bidirectional cloth to protect from chipping. I also coated all MDF not exposed to abuse with at least a single layer of epoxy to seal against moisture – a few drops of water can disintegrate any unsealed MDF fabrication. Next came a lot of sanding, filling (large voids with micro, small ones with auto body filler), sanding, filling, priming, sanding, filling, priming, then painting



Smarter folks than I have found it impossible to match the carpet color, so I did not try. It was very easy to match the paint color. After some experimenting, I found a reasonable texture match to the car’s plastic parts by stippling a thick mixture of flat paint, and lightly sanding with 220grit.

A tap test revealed some unwanted resonance on the flatter parts of the fiberglass shell, so they were treated with Dynamat. CLD tiles work better, but Dynamat was all I had on hand at the time.


Mount the terminal, run the speaker wire (8ga), screw the enclosure to the car’s frame.

Get polyfill from Wal-Mart rather than a speaker part supplier. Same stuff, 1/5 the price. I attached it to the top and bottom with 3m 77 spray. Nothing on the sides, as I now have less than ¼” clearance from the driver to the wall. Press the final back polyfill in with no adhesive, so it can easily be removed to access the installation screws.

Mount the sub, grill, and trim piece, and voila.


I don’t know which I like better to finish the job. I like the way the black WeatherTech mat makes the sub less visually obnoxious,


But the carpet just looks nicer. It cost the minimum job fee ($20 in my case) for a local carpet shop to put a nice edge treatment on the cut carpet edge.


With the speaker wires already running through the rear storage area, installation of the sound processor (JBL MS-8) and amp (Alpine PDX-V9) was simple and straightforward, taking only a few hours. Distribution block (lower left), fuses (upper left), processor, and amp were all mounted using Velcro, for easy access.


Those concerned about temperature buildup in this area damaging the equipment need not be. I used a recording thermometer to measure the temp during a recent drive in 95 degree outside air temps, and the highest it got was 99. There is plenty of airflow back there – it is right next to the traction battery fans. The area also gets hot during charging, but again, never over 100 degrees, and the sound equipment is not operating while charging anyway.

After setup and calibration of the MS-8, I could not be more pleased. The sound is incredible. Was it worth the expense? I look at it this way. The difference in price between the base and advanced Plug-In models is $7525. Of the upgrades, only two appealed to me – garage door controls on the mirror, and an upgraded sound system. The mirror only cost me $168, leaving $7357 left to improve the listening experience. I spent $1000 on stuff that was necessary, and $1700 on stuff that was not, so (using logic you may find twisted) I am not only $4800 ahead, but have a much, much better overall sound experience than the advanced model could have hoped to provide. Yeah, it was worth it. I cannot begin to describe the joy I get from driving a car that is everything I hoped it could be. It is all at once the world’s most efficient electric car, most practical gas car, quietest luxury car, and surely ranks amongst the best sounding music entertainment cars on the planet. Thanks to all of you at PriusChat for the info to make it possible.

 

Approximately 120 lbs for the sound deadening materials, 27 lbs for the sub and enclosure, not sure about the amps, but the wiring probably weighs more. All told, basically the weight of a passenger. I did not have a baseline, but am satisfied with over 100mpg so far. The way I see it, it still weighs less, burns less fuel, and sounds better than a Mercedes S Class.

I thought this issue through while researching the project, and ended up reasoning that it is not about how much power the system can handle, it is about how much is does handle. I listen to music at roughly the same volume that I did before the install, so roughly the same acoustic energy is generated by the drivers. Perhaps there is somewhat greater loss due to the additional electronics, but it is likely offset by the use of Class D amps. Bottom line is that in everyday use, I'm not drawing significantly more electrical power than I did using the stock head unit alone, and saw no need to add batteries or capacitors. Again, my preference is music. Not looking to annoy folks at stoplights.

If I'm wrong and do trash the battery, I'll replace it with an Optima Yellow top and add a capacitor rather than an additional battery.

 

Quite thin, actually. I would estimate it to be approximately 6-8 guage.

Thanks for that. It is precisely the sort of advice I was looking for when researching the install. I come from an aviation background, where simpler is better, and it is all about a simple alternator and battery situation.

Good idea. Can you recommend a product?

Regarding operating the system for an hour in ACC - not gonna happen. I only listen to tunes when driving. I will heed your advice, however, when considering loaning the car to a teenager, and remove the fuse powering the whole thing.

 

Joedirte, thanks a million for all of this advice. I don't know what I'd do without all of you helpful folks at Priuschat.

I've downloaded Torque to my phone and have a PLX Kiwi ODB2 bluetooth adapter on order, so will be able to monitor voltage and (if I can find it) inverter temp in a few days.

Swapping the main fuse from the battery to the distribution block for a 20A fuse is pure genius. I'll do that right away when I get home Sunday. I'll also plan to install a 1 farad capacitor close to the amp.

I just subscribed to TIS and am downloading the manuals now. Should make for a good read. I believe the power sensing lead used to trigger the processor (which in turn triggers the amp to power up) is already tapped from a non ACC source, but I'll recheck. The wiring diagrams should help me locate a better source if I'm wrong.

Thanks again.

 

I have a graduate degree in brute force engineering, so I'll put it to use with a little experiment. I just bought a hand full each of 20, 30, 40, and 50 amp fuses, and will do a little experimenting when I get some time at home (probably a couple weeks from now - I travel a lot). After installing the capacitor, I'll put in a 20A fuse and crank the volume until either the fuse blows or my ears bleed, whichever occurs first. If my ears remain intact, I'll progress through the 30, 40, and 50, stopping when the volume level reaches the point that I would never consider listening. My guess is that it will be a lower amperage than most of us think - Important point to note is that the fuse assembly is located upstream of the cap, so if the capacitor is doing its job correctly, the amp itself could very well see transient loads of nearly 80 amps, while the battery upstream feeds the capacitor a consistent current of well under 20 amps. That is the brilliance of your recommendation - most folks think about fuses to protect downstream circuits, but your out-of-the-box suggestion can, in effect, help to protect the far more valuable circuits upstream.

I'll probably go with one of the more expensive audio capacitors equipped with a power sensing lead, and direct wire connections that can save a few bucks on large gauge ring terminals.

Thanks again.

 

FM? What's FM?

Kidding, and sorry to be a jerk, but my dislike of DJ's, commercials, and the same 10 songs repeated again and again drove me to iPod (uncompressed CD recordings only), XM, and Pandora long ago. Sorry to say, I've never tuned an FM station since I bought the car in April. I'll do so when I get home Sunday and let you know how it sounds.