At AutoSpeed we don’t do a helluva lot on DIY car sound.

At AutoSpeed, we do a lot on car sound.

Contradictory? Not really: since we’ve done near 3000 stories, even those topics that we cover rarely still have a good few stories available. And this week it’s the topic of DIY car sound that’s been swirling around in my mind.

I’ve bought a new (secondhand) car – a Honda Insight – and fitted a JVC DVD/CD/AM/FM head unit. As a temporary expedient, I’ve simply connected the JVC to the four standard Honda speakers. These are single cone, nominally 6 inch units positioned in the two doors and in the rear bulkhead behind which the battery and control electronics for this hybrid car are situated.

Like most OE units, the Honda speakers’ efficiency is high and so the power output of the head unit is sufficient for my SPL needs. But the lack of bass and treble are obvious. (Interestingly, with the ability of the JVC to allow you to set individual speaker levels down to 1dB and also set distances from the listener to each of the speakers, the imaging and sound stage are fine. It’s just the lack of highs and lows.)

I love collecting speakers and so I have plenty lying around, some of which I have been trying in the Honda. But there’s a big problem: the Honda speakers are shallow in depth. This lack of depth is required in the doors and also in one side of the rear bulkhead – although not the other side. A shallow speaker is limited in the degree of ‘coning’ that can be use and also in the size of the magnet. So, basically, no generic high performance 6 inch speakers fit straight in the required spaces.

I don’t really want to cut the aluminium car up to fit larger speakers and so I’ve been looking at pre-made speaker pods (trimmed with vacuum-formed vinyl or carpet) that are now available very cheaply. Initially I thought of getting some 6×9 pods for the rear bulkhead – I recently sourced some OE 6×9 two-ways that look really good. But after doing some measurements, that approach had to be wiped from the list: whenever they’re right back, the seats come to within millimetres of the bulkhead. Without limiting seat travel, there’s simply not the room for the pods to project into the cabin.

Then I thought of doing the same with the doors, this time with 6-inch pods. But while there’s room, if you sit in the car and splay your legs slightly, your outer leg would often be hitting the door pod. One of the characteristics of the car that gives the small cabin a feel of real roominess is that no part of your body contacts anything prematurely. And I didn’t want to lose that aspect.

Another alternative is to leave the factory speakers in place but to limit the frequency range over which they’re working – the factory speakers, if confined just to mid-range frequencies, will probably sound fine. Adding door tweeters with full LC crossovers will allow this to occur, with further capacitors then used to limit the bass going to the OE drivers. Of course, you then need to make-up the bass deficit somewhere else…

Which brings me to subwoofers, of more correctly in this application, just woofers. The Honda weighs only 850kg or so; the weight of a passenger and/or full fuel tank are clearly able to be felt from behind the wheel. So the last thing I want to do is to add a heavy subwoofer box. There’s also very, very little load space and filling any of it wouldn’t be a positive.

I don’t have an answer: I’m thinking of installing a subwoofer tube across the load area directly behind the seats and making this enclosure from plastic pipe or even a lightweight expanded polyurethane. The rear speakers – which don’t really do much anyway – could then be removed, so offsetting a little of the mass gained from the sub and its associated amp.

But it’s really is all very difficult: when there’s little space to start with, how do you get good sound without spending a motza, cutting up the car, adding lots of mass or filling the load space of a hatchback?

Footnote: A major part of the answer came in the form of a new, flat package combined sub/amp, which we reviewed in AutoSpeed a few weeks ago.