audio help for a '91 318is

[idickers]

Thanks. Any suggestions for a 4-channel amp? It's been a long time since I bought a car amp, and the descriptions for Class A, B, A/B seem a bit like smoke and mirrors. How can I tell what the real RMS is for 4 ohms? For example, I found a Planet Audio amp (AC1600.4) that claims 4x200watt rms @ 4 ohm for $80. I seem to remember amps being a lot more expensive. Have they gotten significantly cheaper, or just figured out how to make their specs harder to interpret?

[StereoInstaller1]

Yes, the price of performance has dropped incredibly, to the point that my recommended woofer is $60 or so, and one of my favorite 5 channel amps is 130...plenty of power, plenty of controls... Just don't expect 20 years out of it!

[StereoInstaller1]

Check out the MB quart amps too, I am just nuts about the "Mykro" series, just did a 5 channel on an 8" (Massive Audio Hippo84) and was stunned what 200 watts does on an 8" from such a small amp.

[modernist]

So, say I want to install an 8" 'box. I have the ski pass hole behind the rear seat, but the seat itself has no opening. In your experience, does that sound good? The stock premiums do sound nice, but they really lack bass.

Also, driving that sub. My HU has an RCA sub out. Using just a sub amp, HU speaker out for the rest: good idea?

(noob question)

[idickers]

Yes, the price of performance has dropped incredibly, to the point that my recommended woofer is $60 or so, and one of my favorite 5 channel amps is 130...plenty of power, plenty of controls... Just don't expect 20 years out of it!

How would one of the new amps like the Planet Audio AC1600.4 (rated at 4 x 85w rms @ 4 ohm) compare to an older amp? I have a 1997 Precision Power PC450 (rated at 4 x 50w rms @ 4 ohm) that I pulled out of a project car that is just sitting on a shelf. Is the inexpensive AC1600.4 really 75% more powerful than the older pricey PPI amp?

[StereoInstaller1]

First, yes it very likely is...and second, it doesn't matter. An i7 runs rings around a Pentuim Pro, and a 2014 Camaro is a much better car than a 1981...yes, new amps are better, but that just isn't that important in your situation.

Wattage is logarithmic, so double the power really doesn't mean shit, much less that supposed wattage rating. Besides, it isn't power that makes a system sound good, it's crossovers and adjustability, that's the difference between mud and music.

Thats the real reason for a subwoofer BTW. It's not about making you look like a 17 year old, its about allowing the amp that runs the mids and highs to play cleaner and clearer, thus making clearer sound overall by reducing strain on the gear.

The bonus is it plays MUCH louder and MUCH clearer, and you can use less expensive peices.

I personally am a huge fan of not wasting your money. I officially reverse my position on what to do in your car. Since you have that amp, which IIRC lacks proper crossovers, you need to replace your deck. There are tons of great choices for under $150, and several under $100 right now.

If you got a new deck, one that had all the features you need (3pr pre-outs, HPF, LPF) then we can use half that PPI on the sub and the other half on the fronts. The deck can run the rear, obviously use the HPF on mids and highs, and the LPF on the bass.

You need to do that PC450, a SVC 8" woofer (Infinity 860W) and one of our cute little 8" boxes...and a new deck.

Oh, the "seat thing"...

We have sold over 800 E30 boxes, so there are LOTS of opinions and solutions out there.

Here is a point of logic I think will make sense: bass waves contain much more energy than higher frequency waves, we all know this. Bass travels through walls, metal, windows, everything. By forcing the bass into the cabin, we get as much of that energy as possible through the seat, making the effect much less obvious.

Yes, having a seat in front of the woofer is a minor reduction in output, but if you take some of the foam out of the back of the seat, it works great.

So, hopefully that clarifies things a bit.


Luke

[idickers]

Thanks for the detailed response, that is really helpful. Unfortunately, I might have shot myself in the foot, as a year ago I replaced the stock deck with a JVC KDHDR52, which only has two sets of preamp outputs, front and a rear that can be switched between rear speakers or a sub. Bummer.