A Bit of Bass for Betty the Bentley

Things have changed over the years, I seem to recall that the Cortina Mark 2 that my parents bought in the early 1970's didn't have a radio. You could buy one, it was an option, from what I remember it was AM only and had an output of about 3 Watts. When Japanese cars started coming in they had a radio as standard, usually AM/FM but still only a few Watts per channel.

You could buy after market stuff - 8 tracks were popular back then and the cassette tape was invented back in about 1963 but it took a very long time before the likes of Ford and Vauxhall bothered with such new fangled devices. Except for the Japanese stuff very few cars were designed with sound in mind, most came out the factory without speakers or anywhere specific to put them, those ugly add on rear shelf pod things were the norm back then. God they were shit.

It's only really in fairly recent years that manufacturers have started fitting decent sound systems and designed the cars with acoustics in mind. Most of the premium brands now work with high end audio suppliers to produce systems of outstanding quality - Bentley now use Naim, Audi fit Bang and Olufsen, Porsche used to use Bose, don't know what options they offer now. Doors are usually much deeper and often pods are moulded in to allow for deeper more powerful bass. Tweeters are fitted high up so the passengers and driver get more direct high frequencies directed to where they are needed. The number of speakers has gone up massively, 2 used to be the norm, then 4 but these days 14 is not unheard of. Everything has a sub too, nobody wants a car without a fairly decent system and they definitely want bluetooth and CarPlay and all those sorts of things.

By the mid 1980's chips had come out that gave high power amps in a tiny package, 20 or 25 Watts per channel  was common, my Capri had a very cool little after market Clarion cassette only player with that sort of power driving 2 6.5 inch speakers, I thought it was the mutt's nuts. i sunk the speakers in to the rear parcel shelf so the boot acted as the speaker cabinet - I was Jack the biscuit, the thing had power and bass. My Last Jag had a factory system by Bowers and Wilkins, it was 1200 Watts from memory, had a sub and 8 or 10 other speakers, it sounded fantastic.

Betty - being from 1998 originally had an Alpine system which had been removed long ago and a later head unit fitted. When I get her the front left speaker was damaged and was making a horrible noise so I changed the front pair - I kept with Alpine and used the closest modern equivalent of what was in there. It sounds ok but there is no real bass - nothing much below about 60 or 70 Hz and it has no thump to it. Being mad on music it just doesn't do it to me, it's all flat and very 1980s rather than 2020's. I don't spend much time in there and I'm not looking to turn it in to a mobile disco but I would like something better. As the car is not really designed with sound in mind the doors are pretty shallow. I don't want to modify them so my only real option is to add a sub woofer into the boot area. you can get ones that go under the seat but they are rubbish, not worth the trouble.

I am at the limits of my Wife's patience and tolerance at the moment, so a big spend isn't going to get authorised so a bit of creativity is required.

Designing a sub woofer is pretty easy, there is a ton of info out there, calculators on line and even software that gives you a cutting list for the bits of wood or MDF to make your own. My initial idea was a Temu 10 inch driver built in to an MDF cabinet with a large slot type reflex port driven from an amp of about 500 Watts. The Alpine head unit has a subwoofer output and the level can be controlled from the menu, I can run an RCA cable down the car to the boot area, the remote switch wire is already there for the electric aerial, the hotel battery is right there too. The Arnage has two batteries - the starter battery and the hotel battery that powers everything apart from the starter. there is a load sharing controller so it's a bit more complex than that bu I will wore to the hotel battery. Between them they can provide over 1400 amps, which should be adequate. These days you can buy high power amps for very little money but you need to be aware that a lot of them advertised with massive power are a massive con. In my search I saw one claiming to deliver a massive 7600 Watts but looking at an on line test it was more like 100 Watts per channel RMS. It's been going on for years and it's really annoying but stick to the principle that power costs money and you won't go far wrong.

As luck would have it I was on facebook one day and an ad came up from somebody literally 100 yards down the road from me that had a sub woofer box with two 500 Watt 12 inch drivers in it, the ad said he would throw in a couple of amps of unknown functional status and all for just 40 quid. The speakers were ok, the couple of amps turned out to be one amp and of course it was knackered.. I bought one off ebay but the one I got is a hefty beast rated at about 300 Watts x 4 and verified by an on line test I saw some time back. It's bridegeable so that would give me 600 Watts, more than enough. Obviously it's knackered but it was free and it should be fun to take it apart and have a fiddle with it.

These things all work in a similar way and when you open them up they look remarkably similar inside. The tech that allows such high power is quite interesting - it started to come in about 1980ish, and that's the DC to DC converter. It converts the 12volts of a car supply in to anything up to about 120v which can then be stuffed in to the 4 ohms of your speakers to give massive power. Many amps are capable of running down to 2 ohms, that's serious power that would almost certainly require a significant power distribution system and an additional or uprated alternator. You can go mad with this stuff, spend a fortune and have way more sound pressure than is sensible or safe. I don't want that, I just want a decent system that will go down to 20hz, up to 20 Khz and will sound at least as good as the system I have in my house. It has to be cost effective and it has to keep the interior original, I don't care about boot space, if we need boot space we take the Insignia.

So I have the massive twin 12 inch ported box, 2 12 inch drivers, a broken amp and a new lower power amp on it's way, I also have a 10 inch 500 Watt driver coming and a pile of MDF in the garage. Much experimenting will happen, I am attempting to fix the amp I have first, some parts are on order, I think I know what's wrong with it but until I fix the first fault I can't test the rest.

I'm sure many folk will be horrified with what I am up to, purists will be accusing me of heresy and will be reporting me to various authorities. I couldn't care less, my car, my rules. Hopefully it will sound fantastic, which will be the cream on the cake because it is the most incredible and rewarding car to drive. I love it to bits, this is the last thing to sort, in my opinion it will make it even more enjoyable than it is now.