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Discussion Starter · #1 ·
I have about 6 hours of good listening and tweaking on my new sub, and I have a few observations. I start at the beginning when my sub was first installed.

My sub is a 12" aluminum cone, 14-inch xmax 4-ohm single-coil woofer optimized for really low distortion, sold by Parts Express. It is leftover from a home audio system, so I figured I may as well use it as it is a very good driver. The x-max is about 2/3rds to half what a high-end car audio driver of this size would have, though it is considerably better than the cheap ones.

I built the (sealed) enclosure out of MDF myself. It has 4 internal bracing ribs as well, all screwed and glued together. The sub is powered by a 300+ RMS Profile Baja amp, with high level inputs. The amp was installed by CarToys, with the EXPRESS instruction to DISCONNECT the rear speakers and route them to the amp.

When I first connected the sub, I deliberately kept all of the gain low for safety's sake. It didn't seem to matter at first, because the modest output I was getting at first seemed like a revelation to me compared to the system without the sub so I only turned it up a little bit. I also (mistakenly) thought the SUB sounded rather strange in the midbass as I turned it further up, so I kept on turning the gain back down when this distorted sound intefered with my music enjoyment.

This morning I discovered that the strange sound in the midbass was NOT the sub. It was the friggin' rear door speakers. Car Toys left them connected!!! Until I have time tomorrow to tear apart the dash and clip the wires to the rear doors, I turned the gain up considerably at the amp, so I can almost fade out the rear doors, but still get a several times greater bass volume than what I was getting before without being able to hear the rear speakers.

Now if the first install of system was a revelation, the bass boost from the subwoofer with out the horrid "fill" behind me from the rear doors was even more so. Nothing less than a mind-blowing epiphany. I had no problem turning the sub up even more, since I was no longer getting the horrible cancelations and confusing sounds from the rear doors.

Geesh Nina Hagen sounded great. So did Green Day's American Idiot album, Steve Earle, Lucinda Williams, Goldfrapp, and so much more. (I have been stuck in traffic for a total of six to eight hours in the last week, btw. All of this for a trip that in good traffic that should take 15 minutes each for a total of 45 minutes).

So I have independently verified something that I have been harping about for some time. You don't need no freakin' rear speakers. The system sounds better without the rears. Period. It is just plain a waste of good money. Even if the rears had been something better than the OEM speakers, they can only produce a sound that cancels out what you should be properly hearing only from the fronts.

Using rear speakers for fill makes no sense from a theoretical point of view, and my ears have independently confirmed this in a completely accidental blind test. I bet none of those insisting on rear fill have actually done a blind test. I now have.
 

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amen to that, rear speaekrs are for rear passengers only - and since they ain't footing the bill...

what sub did you go with? a Dayton? I know PE carries a lot of those.

Also, I'd highly recommend getting a good quality line out converter instead of using the high level inputs on the amp (which are notorious for being low quality). Or better yet, an aftermarkt headunit with subwoofer rca output.
 

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Discussion Starter · #3 ·
Judging from the quality sound I am getting and the rather fine quality of the rest of the amp, I suspect that the high level inputs are just fine on this one. If you could suggest what I should listen for in a bad high-level input, then I might be able to detect it if its happening. I know how easy it is to fool yourself.

When someone here first posted the cheap sub amps here on this site, I couldn't believe the price. When I was a kid, amps at this price were always total ripoffs, that sold at ripoff stereo meets, with three transistors and a small cap and a big sticker saying 1000 watts. They were more like 3 watts!

Nevertheless, my Profile amp is exceedingly well made, both physically and electronically and cost less than $95 with shipping. There is absolutely no reason to pay more per watt. In the 40-degree weather we have here in Seattle right now, I cannot tell that it is much warmer than the trunk itself even after playing heavy bass for more than two hours. It is class-d operation, which means that something like 80% or more of the power is actually going to the speaker rather than warm up the transistors.

The speaker I am using is one of the dayton european-style speakers. I have posted pictures of it on other threads. It is made in either Taiwan or China, but was designed over here in the US. The price of these woofers are low considering the quality of the design; the 15" is less than $160 including shipping. I'm pretty sure the 10" verson of the driver would be adequate especially if you were trying to save space (it only needs a 1.2 cu ft box!). The aluminum cone and butyl surround should be exceedingly durable too. The main reason I built my own box is I wanted to control very precisely the box size to the woofer.

The dayton woofers have extremely low F3 which is the frequency where the sound is 3 db (half volume) down. Most car audio speakers have F3 about 5-10 hz higher than this unless you get really large and very expensive drivers. This means with room gain and the complementary rolloff from the sealed cabinets I should be getting really flat frequency response down to about 22 hz with at least 95 db of max output. Anything below that is pretty much subsonic anyway.

I really don't understand why anyone needs two 15" long throw drivers in their car, but I suspect that they don't sit in their cars when they are playing at full volume. The 12" was slightly inadequate in my somewhat small living room, but my car interior is so much smaller yet, and so far I have not heard any indication that it is being overdriven, and my sub volume is absolutely superb even on stuff with hip-hop level bass.
 

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yeah Dayton is good stuff.

most cheap onboard LOC are just resistors inline with the signal path, instead of an actual transformer. The two things I notice the most are sloppy bass (like too much group delay) and a tendancy to have engine whine on amps running midrange and up.

check out the NE-7V on this page

http://www.autosound2000.com/adaptor_products.htm

probably one of the best LOC's on the market and only 19.99
 
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