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^^I have 800 watts rms class A/B power in my 81 where everything is 8 gauge, but the wires are under 2 feet long coming straight off of the battery.
The reason for this is that the amps that provide this power have super low distortion. A pair of ADS PH15.2 amps and a JBL 4020 for the sub.
What you hear mostly is the first watt anyway, anything above that operates largely on the law of diminishing returns. Make your system clean, clear, and accurate and never look back. SQ is where it is at
Another common problem with the low freq audio installs is a baffled speaker back-side. The paper/plastic cone of the speaker which reproduces the deeper notes moves a lot of air from the front, but also from the back. The condition of a closed or plugged chamber behind the speaker cone will cause muddy, or distorted audio sound because of compressed reflections of air waves getting cluttered and having no escape. This is a particular issue when a bass speaker is mounted in the tire well, and a plate is installed around the speaker outer hub. There should be a duct, or hole leading to the back of the speaker so that the air has somewhere to go. Bose made a very detailed study of this back in the day, and tried to design speaker enclosures that used the reflections to enhance the primary sound from the front cone. It had - moderate success.
Most people think that the distortion is caused by the amplifier stages. In modern electronics, this is very rare. Class A/B amps with well matched power sections, or using power ASICs where the power stage is made up of common rail transistors are remarkably clean within audio ranges. The most critical parts of the install should be the impedance matching with the output stage(8 ohm preferred, 4 ohm ok, 2 ohm - NEVER). Followed by the proper venting of the speaker. Those Bazooka deals are remarkably good at this, because they flow air in both directions. Some of the best setups are now using a class D, saturated drain PWM amps with a switching speed over 2MHz. Since they run in saturation mode, the efficiency can be real good, but some of them use lousy decoupling setups. Best to test before buying.
Sacrifice wattage for quality design. Avoid crimp-only wire/connector links. Keep it clean.
Best to test before buying, my car stereo installer let me try different subs before I bought because all acoustics are different.......settled on small jl model sub with its own enclosure sounds just right to my ears.....
[QUOTE=docmirror;15655373]A The most critical parts of the install should be the impedance matching with the output stage(8 ohm preferred, 4 ohm ok, 2 ohm - NEVER). /QUOTE]
Maybe I am misreading you here, but many car audio professional design systems with lower Ohm ratings for many reasons. For instance, matching a 2 OHM single or dual voice coil speaker with a 1/2 ohm capable amplifier. You maximize the wattage of the amplifier to save space and minimize how many speakers you may need to run depending on your configuration design.
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Maybe I am misreading you here, but many car audio professional design systems with lower Ohm ratings for many reasons. For instance, matching a 2 OHM single or dual voice coil speaker with a 1/2 ohm capable amplifier. You maximize the wattage of the amplifier to save space and minimize how many speakers you may need to run depending on your configuration design.
I won't go into the engineering aspects of things, but there are formulas for impedance vs frequency which are pretty well known and followed by pros. The audio range from 20Hz to 20Khz is best suited to a ~420 ohm output resistance. In fact, in olden days with large single speakers, and multi-stage tube amps the output stages and the speaker were matched at the factory for approx 400 ohms. Simply because the bandpass and audio range of the freq would be best qualified. Of course, later on with the advent of transistor amps, the impedance could be lowered a great deal, and the output power would not suffer with a significantly lower resistance setting(if you search, one can still find speakers with a matching transformer mounted to the frame to drop the impedance). Still, 8 ohms is well below the optimal ~420 ohm range, but the output stage of the amp can be setup to minimize ringing, feedback, and harmonics.
But - just because we can do that, doesn't mean it's best. So, I don't really care if a sales person wants to use 2 ohms, and tell customers it's 'best' for amp gain, it really doesn't matter to me. I am not an amp gain/wattage type of consumer. My opinion was, and will be that the flattest response, lowest distortion, most suitable impedance match is found at 420 ohms(no longer commercially avail). Next best is 8, and then in some cases 4, but I will NOT give 5 Kopeks for a 2 ohm 'solution'.
edit: This is the only thing I could find with a very quick search. Note the chart references: THD @ 20W/8R = total harmonic distortion with 20 watts dissipated into a 8 ohm resistance(impedance really, but why quibble). A class A/B amp, with matched gain power stages would be even flatter. No one would even bother with this for a 2 ohm load.
[QUOTE=Shawn Stanford;15649896]I used the spare tire sub from a Nissan Murano. I think I paid $40 on eBay.
How's the spare tire sub working out for you ? I rarely listen to the radio but my daughter can't live without one. Just want a little more than stock.
Last edited by RSMartin; 03-05-2019 at 10:54 PM.
Reason: Address
[How's the spare tire sub working out for you ? I rarely listen to the radio but my daughter can't live without one. Just want a little more than stock.
It's good. It's not going to blow the windows out of the frames, but it adds some bottom end, and that's all I was looking for. And you can't go wrong for the price and fit.
I chose this one for several reasons:
- amp and subwoofer all-in-one
- enclosure is a direct fit into the tire well with room for the spare tire lid, if desired, to keep the trunk area usable and the sub hidden
- uses an 8” woofer which is plenty for my needs
- at $120 (comparing it to some more expensive solutions) seemed like an acceptable amount of risk, since I just want a more well-rounded sound in my car than what I have
i have not done the install yet due to some other interior work I am doing, but hope to do so in the next month or so and will come back with thoughts. The one comment I have so far is that it states it has 4 gauge power and ground, but the power/ground wires that come out of the subwoofer connector are 14 gauge.
This is a pretty nice package to fit inside the existing tire.. Do you know if this is 4ohm or 2ohm resistance? I'd be curious to know how well you think it works and what the driver looks like on the inside.
Originally Posted by Shawn Stanford
I used the spare tire sub from a Nissan Murano. I think I paid $40 on eBay.
This is a pretty nice package to fit inside the existing tire.. Do you know if this is 4ohm or 2ohm resistance? I'd be curious to know how well you think it works and what the driver looks like on the inside.
On a related note, I've been considering either building my own box like the sharkwoofer or just using a standard OEM sub box designed for the trunk or spare tire well. I have an Audi Q5 with a sub and pulled it out to compare the fit in the 928. The Audi sub is one of those spare tire systems that is designed to fit into an 18" wheel so its a bit bigger than the above mentioned Nissan/Bose unit which fits in the 16" rim.
Here is the test fit in the trunk. I was able to line up the securing bolt and cap as well. The depth of the trunk well is about 6". The sub box is about 5" deep. Here you can see it sits about .5" below the trunk floor with the .5" OEM rubber spacers below. This is what the driver looks like Just your standard 6.5" driver, no fancy electronics in there. 2-ohms
This box is a nice unit and offers some room for a trunk mounted amp as well. But It would be nice to find a slightly larger box. The working diameter of the space is 19.25" where as this box is about 17" diameter. I'm not convinced I am going this use this Audi solution, but thought the information would be interesting.
It would be nice if someone know of a larger pre-made box. Any thoughts?
Here are some interesting finds in my searches on eBay.
So I test fitted the Precision Power Subwoofer in the spare well today. It fits well length and width wise, and can be oriented either way. Depth would be perfect if it were not for the welded spare tire base that stops it from sitting flat, as it sits up in the well. If it was removed, I could put my well cover back on and the opening for the speaker just about matches.
So I test fitted the Precision Power Subwoofer in the spare well today. It fits well length and width wise, and can be oriented either way. Depth would be perfect if it were not for the welded spare tire base that stops it from sitting flat, as it sits up in the well. If it was removed, I could put my well cover back on and the opening for the speaker just about matches.
Recommend removing that spare tire base?
Can you share a picture of the model you are using with some photos of the fitment in your car? I am curious to see.
02-21-2019, 06:20 AM
where everything is 8 gauge, but the wires are under 2 feet long coming straight off of the battery.
