Lopgok's stereo upgrade - in many small parts

*** I finally added my subwoofer, please scroll down to read about it. ***

I am in the process of upgrading my stock prius sound system.
I will be documenting some steps along the way.
I have installed a few car stereos, but I am not an expert.
I do have a very good understanding of electronics, stereos, wiring and the like.
If you find my thoughts useful, great.
I have found a lot of silly ideas in car stereo, and I will try to avoid them.
I am doing the upgrade myself, not to save time or money, but to ensure the job is done correctly.

Today, I wired up the power and ground.
The factory ground wire looks to be approximately 10 gauge. No doubt ok for some purposes, but I want to minimize voltage drop. Leaving it in place, I decided to add a lower resistance ground wire of my owk. So I used a piece of 6 gauge wiring. The battery end got a 1/4" ring lug terminal, and the chassis end got a 3/15" ring terminal. I used a ratcheting crimper to attach the ends. I have seen poor crimps, and a ratcheting crimp tool greatly reduces these. If you can pull the wire out of the terminal, it is too loose and not making good contact. I have soldered these terminals before, but it is hard work, and the interface between the soldered wire and the unsoldered wire is a weak point which can fail under vibration. A good ratcheting crimp tool is about $20, and should last a lifetime of casual use. I recommend PP75/SB50 Powerpole Crimping Tool for 75 & 50 amp [CT-75] - $16.99 this tool.

You will need to run a power wire for each amp (unless you use a silly power distribution block). The standard AGU glass cylinder car stereo fuses are marginal. If they use spring loaded contacts, they are useless for any serious current. The typical screw down set screws used by the 5mm diameter car stereo fuse blocks are also useless, as it is very difficult to get a good, low resistance connection. Despite having some lying around, I bought some maxi-fuse holders. Maxi-fuses are bladed fuses with a low resistance connection. They look like standard bladed fuses used for cars, but on a larger scale. They are available in up to 100 amps, which is much more than I will need. I bought some inexpensive inline fuse holders with 8 gauge wire. I attached the 8 gauge wire to the battery terminal with a ring terminal using my crimp tool. I attached a long run of 8 gauge wire to the other end with a coupler, which is a tube of metal with a 8 gauge hole, designed to be crimped. I removed the insulation of the coupler before crimping, and put it back after crimping. I also covered the insulation with some heat shrink tubing. I used a heat gun (about $10) to shrink the heat shrink tubing. I will be using a JBL MS-8 amp as well as a subwoofer amp, so I installed 2 fuses and 2 runs of 8 gauge wire for the 2 amps.

There is another type of fuse, that has screw down terminals called the ANL or ANE type of fuse. It is a good design, but for higher currents than I care about. I recommend reading about fuses at FUSES They have pictures and lots of useful info.

 

Next, I needed s source of switched power. I decided to use the cigarette lighter. I loosened up the front of both side panels of the lower central console. Next, I pushed out the panel with the cigarette lighter from behind. I disconnected the cigarette lighter wiring. The black wire is the positive. There isn't much room to work, but I managed to strip away some insulation from the wire. Next I wrapped my signal wire around it. I soldered it up, and wrapped it with electrical tape. I secured the electrical wire with a cable tie, as I had electrical tape loosen up. If I had some shrink wrap tape, I would have used it instead.

I have some insulation displacing crimp on wire taps, but I have had them come loose, and since it is a bit involved in accessing, I decided to solder it.

I routed the wire along a thin black loom wiring harness that went to the front left area of the passenger seat.; I had to pull up the carpeting a bit around the central console to route the wire. I have 2 pictures, one before I soldered the wire, and the second showing the taped and cable tied result.

 

Well, I wired up the rear door speakers. It would have been nice to remove the door connector, but I have been unable to do so. I have heard that it is very difficult, and likely to break when taken apart. The reason is to be absolutely sure which wires go to the speakers.

The passenger side was quite easy to wire up. I verified the wires, but cutting one when the stereo was playing, and getting silence. After cutting the other one, I verified it was the right one by attaching a 1.5v aa battery to the two speaker wires. If they are indeed speaker wires, the speaker will make a thump. The drivers side was not so easy. The wires are supposed to be black for the positive side, and yellow for the negative side. The colors are accurate, however, there are *two* black wires and *two* yellow wires on the drivers side. Of course, I cut the wrong ones first, and I had to splice them back together again. There is not a whole lot of room to work... I did eventually get the correct ones, and put everything back together again. Without removing the connector, I have no idea how to verify which wires are the correct ones. Perhaps the other black and yellow wires go to the optional rear door tweeters. I have no idea, so I spliced them back together again. Not very clever of toyota to have multiple wires with the same color on a single connector...

 

Well, I wired up the JBL MS-8 amp. It is secured to the carpet with 4 bolts with the heads going from under the carpeting up. I used large washers on either side of the carpeting to distribute the load. The first picture shows the slit I cut in the carpet to allow all of the wires to come through. I will be using convo-tubing to dress all of the wires. The clear wires are the speaker wires, which connect to the amp in the back. Channels 7 and 8 will be for my subwoofer once I build it. Eventually, I will use an outboard amp for more power for the subwoofer. The gold wires that don't seem to go anywhere are the sub speaker wires. When I pulled the two unswitched power wires for the amps, I also ran the subwoofer wires. The blue wire is the 12v to the amp. It is 8 gauge. I had to trim it down a bunch to fit the 10 gauge ring terminal to the amp. The gray wire is a 10 gauge ground wire. I used my ratcheting crimper to make all the power connectors. You can see the crimp on the ground wire where it attaches to the seat bolt. The thick white wire is the 8 gauge wire for the subwoofer amp, which goes nowhere for right now.The black wire is the switched 12v wire that I ran from the cigarette lighter. It is the only wire that doesn't come from the rear carpeting area.

The smaller white wires are the front channel outputs from the head unit. They go to the speaker level input connector in the front of the amp. I routed the input wires, the 12v wire and the switched 12v wire under the heater vent at the front of the seat. The rest of the inputs to the amp are not used, and just go to the side. I added black heat shrink tubing to the unused inputs and outputs so nothing would short out. I also added heat shrink tubing to the ring terminals, as I had to cut the insulation in order to use my crimping tool.

Calibrating the ms-8 was easy. The one thing it doesn't do is adjust levels to each speaker, so I sent the fader a few notches back as most of the sound was coming from the dash speakers.

Next, I will be removing the 2 ohm resistors I had in series with the front door speakers (from when I was using the stock head amp). After that, I will fabricate my subwoofer using two 12 inch 91db/watt woofers I have. Finally I will hook them up to either the JBL amp, or a blaupunkdt class D amp I have lying around.

 

Subwoofer fabrication and Install

I upgraded my door speakers to 6x9 JBL's but I wanted more bass.

I read about the 'cubby' subwoofers, but I decided they weren't for me. Subwoofer efficiency is based on several factors. The efficiency of the driver, the size of the enclosure, and the port. The cubby subwoofers have a tiny volume which doesn't help efficiency. They also have no port, which also reduces efficiency.

I acquired two Jenson JW-12 woofers, which have an efficiency of 92db/watt. I have seen a few more efficient woofers, and a lot of less efficient woofers. Why someone would select a woofer with an efficiency of 85db is a mystery to me, unless they want to brag about having a huge amplifier. Since my woofers are 7db more efficient, if I used a 100 watt amplifier, I would need a 635 watt amplifier to get the same volume with 85gb speakers. I also decided I wanted to be able to use some of my trunk space. I fabricated an open shelf enclosure for my two woofers. It was relatively simple to build but it has some potential disadvantages. It will present an underdamped load for almost any woofer. This means the frequency response needs to be equalized. Fortunately I have a JBL-MS8 which has a great DSP based equalizer.

I made a cardboard mock-up of the entire rear shelf area. It turns out that it is possible to build, but next to impossible to put in or remove from the car once constructed. I decided to cut away the sides a bit (as they stick out the most) in order to make it possible to install and remove. I built the shelf out of 15/32 plywood. It is roughly 44 inches wide and 30 inches long. I removed the privacy screen and fabricated a piece of wood to replace it. This was a bit of work. The bottom of the wood needs to taper a bit because the mounts get narrower near the bottom. The very bottom of the mount has a square bulge which needs to be cut away in the bottom of the wood. Next, I removed the bolts by the rear end of the privacy screen and replaced them with longer bolts with an L bracket attached to support the plywood.

Using the cardboard mock-up, I cut the plywood to shape. I had to do a bit of trimming in order to make it fit well. I then cut the holes for the woofers, along with the 8 mounting holes for each woofer. I recommend using a router, as my hole cut with a skill saw was a bit uneven. I had planned on permanently attaching the wooden cross piece to the plywood, but it would make it much more difficult to remove the subwoofer, so I decided to bolt it together. I then reinforced the bottom of the plywood with a bunch of 1x2s. I was planning on nailing, clamping and gluing, but the plywood was a bit warped and difficult to clamp. I decided to use drywall screws to clamp and hold the 1x2s while gluing. I then painted the plywood because it was cheap and very ugly CDX plywood covered with lots of lines used for construction. I covered the top of the plywood with nylon screening so that nothing would fall into the woofer cones. I also bought some gray grill cloth to cover all of the plywood, but I haven't installed it yet. I may use some kind of sound deadening over the plywood, and under the grill cloth.

The woofers had 5 way binding posts. I didn't want to use banana plugs as they might fall out, so I used 1/4 inch spade logs. I would have rather used ring lugs, the the plugs don't completely unscrew. I secured the woofers to the plywood using eight 10-24 bolts, with a washer under the head and under the locknut to help spread the clamping force. I installed the woofer in the car, and while clamping the plywood to the wood cross piece, I drilled 4 holes to be used to bolt the plywood to the cross piece. The rear is held on with a bolt on either L bracket. I used wing nuts to make it easy to remove. Using the JBL-MS8, I added the woofers, and set their range to 20-100 hz. The JBL equalized them to have flat frequency response.

It has been a bit of work, but I can now play any type of music, including pipe organ music. I should be able to generate 108db at one meter using both of the woofers and 2 channels of the JBL amplifier. I suspect that will be enough, but if not, i have the wiring to add a bigger amplifier. There are no buzzes or rattles, as the subwoofer is securely clamped in place

 

I have not measured efficiency or frequency response with my set-up. I do have the JBL-MS8 which should equalize it out for flat frequency response. Based on Thiel-Small equations, my setup will be significantly more efficient that a sealed box.

Since I have a plug-in-prius, I don't have a false floor. I have a really big battery. It would be interesting to use a mostly open baffle design in the false floor of the standard prius.

 

I took the dashboard tweeter cabless and connected the JBL to them, bypassing the 'bass blocking' capacitor which feeds the signal to the dashboard tweeters.
If you can, you want to run higher voltage to the amplifier, in order to minimize noise. Hopefully your amp will accept high level inputs, as the JBL MS-8 does.

 

No hiss.

Since you paid someone to install your system, it is their responsibility to deal with it. Hopefully they are good enough to fix it.

 

So what are you going to use, if you don't trust the manufactures' specs?
Most woofers include the thiel-small parameters.
Do you think the manufactures' make them up?

It is true there are FTC specs for amplifiers, but not for speakers. Still efficiency is typically measured at 1watt and 1 meter, on axis, except sometimes for Infinity which uses 2.82 volts for some of their 2 ohm speakers.

I certainly think efficiency is reasonably accurate, at least comparing products by a single manufacturer.

 

Unless you have your own test equipment, like your RTA, I fear you have to trust the manufacturers. Clearly some are less trustworthy than others.
With experience, and careful reading, it is possible to get some idea who solid manufacturers are and who the untrustworthy ones are.

I have no idea how a ground plane applies to speaker measurements. It sounds like snake oil to me.

It is difficult to measure low frequency response accurately under good conditions.

As for JL audio, I seem to remember a 900w rms amp with a fuse so small that you would need more than 100% efficiency in order to not blow the fuse.