Adding Serious Bass to a Factory System0

April is time for Spring Break, which is a prelude to summer fun. And what’s more fun than adding bass to a factory sound system? New vehicles manufactured in the last few years come with great factory decks — except for the fact that they all lack real bass.

[Ed’s note, I just got a new car and Dave is right, the deck is great, but the bass… :(

Adding serious bass to a factory system requires moving a lot air and this takes woofers, enclosures and amplifiers. Since most vehicle interiors and trunks are sealed, placing woofers on the back deck into an “infinite” baffle works great for the majority of systems. Or a simple sealed or ported enclosure can offer even more bass — albeit over a narrower range. As for the power amplifiers, we have long stated, “Buy all the amplification you can afford. It’s like money in the bank. You can’t have too much amplification in a car.”

This leaves us with the only tricky part of the OEM upgrade — the interface between the factory system (i.e. OEM deck) and the aftermarket bass (woofer, enclosure, and amp). Like the proverbial weak link in the chain, the OEM interface device makes ALL the difference in the quality of the sound. Several years ago, Richard Clark and I designed the N-85V Variable Low-Pass High-Quality Stereo OEM Adapter so that we could achieve the maximum signal with minimal noise. The N-85V features full transformer isolation to keep the factory systems completely away from the aftermarket components. The frequency response of the N-85V (and also the non-variable N-85) is centered at around 40 Hz and the output level is 9.5 Volts rms. When compared to a typical aftermarket car audio deck with the standard 2 Volt pre-amp output, the output of the N-85V is over four times better. As with never having too much mobile amplification, there is no substitute for signal level. Boosting the signal with line drivers, etc. also boosts the noise levels — which can be done at the power amp for free!

Why do you need 9.5 Volts of signal from your OEM Interface Adapter? The answer is that we adjust the gain structure of our mobile audio systems for maximum signal and minimal noise. This requires that we first set all of our pre-amp components (deck, eq, electronic cover, etc.) so that they clip at the same time the deck clips. However, at the amplifier / speaker part of the system, we set the level for 3:1 gain overlap. This means that if the amplifier clips at 2 Volts, we can feed it 6 Volts. If the power amp clips at 3 Volts, then we can feed it 9 Volts. Other settings in the gain structure result in: 1) A system that lacks power and punch, or 2) A system that is noisy, hissy, etc.

So choosing a 9.5 Volt OEM Interface Adapter is important to adding lots of clean, non-hissy, bass to your factory system.