Car Audio

[Derek Meyer]

I did a complete Alpine system in my 93 Explorer back in the 90's. I replaced the head unit with a CD unit that had optical outputs, and installed a signal processor that had optical inputs, along with a 6 disc CD changer. I had three amps, one 4-channel amp for the front mids/tweets (in custom kickpanels), one 2-channel for the midbass (located in the doors) and one 2-channel for the subwoofer (bridged into one channel). Once I got it installed and adjusted, it sounded phenomenal - imaging was spot-on and the sound quality was really high. I had an installer from a high-end place in Spokane listen to it, and he told me that, at the time, it was one of the two best sounding vehicles he had ever listened to.

I leared a lot about what constitutes good car audio from this project. One - you need tons of power in a car system if you want to listen at medium to high volumes while driving. Road noise is a killer and you need power to overcome it, especially at the low end. I built a custome subwoofer box that had two Alpine 12" DDDrive subwoofers, bridged together to a 2 ohm load. I ran these from a 2 channel Alpine amp that was bridged, so the load was effectively 1 ohm. I called Alpine and discussed this with an engineer, and he assured me that the components would handle this configuration, and even gave me dimentions to build the box to for the best sound quality. It was a sealed box with 1.4 cubic feet per woofer, filled with polyfill. I built it from 1" MDF and lined it with V-Blok, a sound deading membrane made by Cascade Audio. That box was really heavy, but really inert. The amp could produce 900W RMS into its 1 ohm load. It had an 80 amp fuse on the power line, which was a 4 gauge copper line that came from the battery. I also had a 1 farad stiffing capacitor to deal with the large transients that loud bass notes produce. The mid-bass speakers were driven by an amp that was 100w per channel RMS, and the front stage was 50w per channel RMS. I used the digital crossover in the signal processor, which also provided equalization and time alignment. It was a great system.

I recently upgraded the system in my 2020 Edge by replacing all the speakers and amps with aftermarket gear. This time, I had a local shop do the work and bought all the equipment from them. All I can say is, wow, talk about expensive! It was about twice as much for the install as I expected. They did a great job and the system sounds fantastic, though it does not play as loud as I thought it might. That doesn't matter now, though, as 53 year old me doesn't listen at the same volume as 27 year old me did. They used Hertz amplifiers, which have all the processing built in now (eq, time correction, level adjustment) and Audison speakers. I went with one 12" sub in a custom enclosure that fits in the spare tire well. They used a signal converter that connects to the head unit's outputs and converts them to digital to feed to the amps. It also has analog input-output if needed.

If I had it to do over this time, I'm not sure I would have had it done. The factory system wasn't bad, so this upgrade was not the night/day change that my old Explorer was. Plus, I didn't do any of the work myself this time, so I didn't have the same satisfaction at the end of the project. I'm still on the fence about whether the money I spent was worth it. Maybe my expectations were too high, but I did expect better performance than I got.

[Greg Parrish]

Yeah, my 2020 Explorer has the upgraded sound system in it with subwoofer. Can’t remember if it’s a JBL, Harmon, or what system. It’s not bad for a factory system. If i had one gripe it would be that the Sync system sucks for use with Apple Car Play. It’s been such a pain over the last 2 years. If you plug the phone in or touch any buttons in car before all the ford systems finish booting up it just will not ever connect to apple car play. Plus, it doesn’t do wireless car play like our BMW X5. Otherwise, its been fine for me.

[Derek Cohen]

Very interesting and helpful posts. Thanks all.

The realisation is crystallising that more power is needed than the head unit can supply. The Alpine ilx-507a gets absolute rave reviews, for screen, speed, connectivity, sound quality, etc. However it is just 18 watts RMS (50 wats music power, which is a nonsense measurement), and has 4 speaker outlets. Power to 6 speakers will lower this further. Now I know that we only need a couple of watts RMS to get sound, and probably 5-8 watts rms would be sufficient … if the car was stationary and the motor off. But this car is a convertible, and there is competing noise from the engine/muffler, wind, road, and environment. The video (I referred to earlier) uses a hardtop Porsche 911 (996 generation, which is the same as the Boxster 986 from the nose of the car as far as the seats). The music was presented in a workshop, not on the road.

More power needed. Alpine makes a D-class amplifier specifically for this head unit. Two will be needed to ramp up the outputs to the 6 speakers. This is the amp in the video. The blurb for the amp states: The KTP-445U Universal Power Pack amplifies the head unit power output, resulting in up to a 150 percent power increase over the original power from the head unit's built-in amplifier.

I suspect that others here will agree, but it would be reassuring to know if this sounds right as I need to contact the installer and confirm my order.

Regards from Perth

Derek

[Greg Parrish]

Sounds right to me, just remember than 18w from a head unit or even some of the head unit extension amps is not equal to 18w from a true separate amplifier. Kinda like the way a hand held router or shop vac says its 3 hp but its not equal to a 3hp motor on a shaper. You will get much more solid power, sound and headway from a true separate amp. I don’t know that head unit or the specific amp, but my guess is that it is a smaller amp similar to what’s in the head unit.


Just take a look. The KTP-445U only has a 15 amp fuse. https://www.crutchfield.com/p_500KTP...ower-Pack.html

One of the Alpine Separate amps has 90 amps of fuse. https://www.crutchfield.com/p_500RA9....html?tp=78740

I’m sure the KTP-445U will expand the output number of channels from the head unit, but if you want real, clean power with plenty of overhead capacity, you should look at the truly separate amps to cover all 6 speakers.

It’s just like home audio. A receiver with 14 channels built in will sound fine until you push it. Then as power output goes up, THD levels, noise and distortion also go up. But if you replace those channels with true outboard amps, you gain a new level of clean, powerful sound with plenty of reserve power when called upon. I know I’m pushing you to spend your money, but for someone with a nice system at home, the similar system in the car will be appreciated.

Regardless, I still say start with the head unit and work your way out from there. It will become diminishing returns like anything. Your biggest bang for your buck will be a head unit with low noise floor/level, a high voltage line output to an outboard amp with low noise floor/level feeling solid, clean power to a set of reasonably efficient speakers. More to it than that, but those are the basics for solid, clean sound.

[Derek Cohen]

Thanks Greg.

I looked at the larger amp (R-A90S). Three strikes against, although it looks to be the better amp: it is not available, and if it was it is quite a large unit and unlikely to fit in the available space. The smaller KTP-445U is less than half the size, will fit where the existing amp is installed, and also about a third of the cost. I would be using two, each of which is 45 watts per channel (a total of 8 channels). And is available.

Regards from Perth

Derek