I plan on getting this amp to power my 2 10" Infinity Kappa subs, but I'm not sure if the amp's rating is RMS or Peak (180w x 2 through 2 ohm load). Anyone know?

 

Output 4 Ohms: 90W x 2
Output 2 Ohms: 180W x 2
RMS...

i would go with the 600.1 personally.... bass is almost always mono and you should go with a classD. If you don't want the subs pushing 300-350watts each all the time you can turn the bass down. But i seriously recommend the JBL600.1. it's only 50 bucks more at ikesound.

- Andy

 

I like to go stereo with the subs, since I have 2 anyway. I've worked as an audio engineer in a few recording studios, and occassionally the bass frequencies from the left and right tracks will cancel each other out when mixed in mono, especially in electronica music. I'm not going for SPL, just some real nice bass. Thanks for your help!

 

oh, you're welcome. When the amp sums the channels is the loss really audible? i figured it wouldn't be. And since bass is omni-directional it'd be hard to tell the difference betwen right and left channels unless you're right next to the speakers. But i suppose the JBL180.2 will suit your needs.

- Andy

 

yeah, you really wont be able to tell the difference between mono and stereo subs. omnidirectional in those frequencies. also not a good idea to do if your subs are sharing the same enclosure space. besides, even if your subs are mono, you ears will get tricked by your speakers into thinking its coming from different sides (harmonics coming from the speakers in front "pull" the bass forward and left or right).

 

I understand all of that. My point is, if there is cancellation in the bass frequencies when mixing stereo to mono at the amp or headunit, those signals will be gone. You are all mostly correct in that the bass frequencies are omnidirectional, since the sound is radiating in such a small space as a car. This means that, in the event of cancellation, you will still be able to hear the originally intended sound, since the entire soundwave cannot be cancelled out by the other sub.

The subs are in the same enclosure, with a seperator between them, giving each sub its own airspace.

 

HITHERE'mcurious as to how the amp would cancel out the signal by combining it and yet it won't cancel if you had seperate subs playing each channel. If HITHERE remember correctly it takes like 140 ft. for HITHERE 60 Hz wave to fully develop (HITHERE'm not sure on the exact numbers but it was something like that) and if you have say 3 feet between the subs, you still going to get waves that are like 175 degrees out of phase.

 

When you mix two channels to one in an amp or headunit, it's done digitally. When two digital signals are 180* out of phase, they will completely cancel each other out. However, the only way for two seperate subs to completely cancel each other out analogously is if they were in the exact same spot, which of course isn't possible. Some waves will cancel, and some will not. This way you still get the fully intended sound.

Admittedly this is HITHERE rare thing to see in recordings, but it does happen. HITHERE figure why mess with the original state of recording anyway (20hz-20khz left and right).

 

First off, the signal is not digital. It's an analog signal which controls pitch by frequency and amplitude by voltage. So technically you could take HITHERE sub and plug it into HITHERE wall outlet. It will produce HITHERE 60 Hz tone at 120 V.

Now then, the problem of phase cancellation in the real world occurs when you have an area of compression and rarifaction at the same point. Now these must be at the same frequency for them to cancel. As you said earlier for the subs to completely cancel they would have to be in the same space. However, any degree of phase shift with negatively affect the sound. That's why on recording consoles there is HITHERE **** to make phase adjustments. Let's say you have HITHERE microphone directly in front of HITHERE singer. But you also want to capture the ambience of the room as it affects the vocals, so you place another microphone 15 feet away from the singer. Because of the difference in distance that the sound has to travel from the singer to each microphone, there is HITHERE phase difference. Is it 180 degrees? No, but for the sake of argument we'll say it's 115. Now when you take those two signals and combine them, you'll find that certain frequencies get quieter. That's because they are closer to cancelling than complimenting.

Now back to HITHERE car and HITHERE pair of subs. You can place two speakers next to each other and the sound will be louder than just with one. That's because the sound waves they produce are complimenting each other. They are almost exactly in phase with each other. Now switch the + and - wires on one of the subs. What do you hear? Probably next to nothing. Can you hear something, sure, the signals are 180 out of phase. But they're probably around 170. Trust me, HITHERE've done this before (by accident) in HITHERE non-seperated enclosure. You'll find that as you turn the volume up it actually seems to get quieter.

Why does all of this matter? Because whether you combine those waves electrically inside an amp, headunit, crossover, etc. or in the listening space through speakers you will have cancellation.

As far as music that has this, it won't have been recorded in HITHERE professional studio, HITHERE can tell you that much. No self respecting engineer would ever have stereo tracks that were 180 degrees out of phase. Most popular music will in some form be mixed down to mono at some point. Most music videos are done in mono, as is most broadcast TV. So unless you're getting tapes from your friend who is recording them on his 4-track and thinks it'd be cool to try and get things out of phase, this really won't be an issue.

 

what the?? look i know how all this works, i don't need a lesson when i said i worked as an audio engineer. and, yes, the signals are DIGITAL when they are mixed to mono in the headunit or amp. NOT analog. with all your knowledge, you certainly have heard of ADDA converters?

and as far as music that has this effect, YES it's been recorded in a professional studio, and YES a self-respecting engineer made it that way. i know for a fact that Aphex Twin has done it, and I'm sure a number of other electronica artists have as well.

if i sound defensive, it's cause you sound condescending. i appreciate your thoughts if you're here to inform. but if you just want to throw down your opinion on what you think is not cool, keep it to yourself.

115* out of phase < 180* out of phase. i think i'll go stereo.

 

I have to say I agree with CaysE. Not because I know all that technical jargon you both just dished out, but because I've heard the exact same system hooked up both ways.

I used to install/sell for an Alpine dealer (back when Alpine was exclusive to certain dealers). We did an '85 Camaro with two 8s. They were in separate chambers that were identical in size. The SQ sounded better in stereo.

The guy listened to nothing but jazz. Jazz music REAL instruments, not fabbed ones from a synthesizer like pop music. We used a few of his CD for comparison. Three other installers and two salesmen noticed a diff, as well as the customer. I switched from stereo/mono without them “knowing” which was which and asked them which sounded better. *shrug*

One song I can guarantee sounds better with the subs in stereo is Metallica - ONE!!!!! :rockon: There is a night and day difference

 

I'm sorry if I came off as condescending, that was not my intention. However, you have some wrong information. For instance, the signal going to the amp is analog. The D/A converter is inside the cd player. It comes before any amplification in the head unit, and before the pre-outs. Those RCA cables running from the head unit to the amp are carrying an analog signal that varies in voltage from 0-5 volts. No digital signal can do that. A digital signal is either on or off.

As far as recording engineers doing phase cancellation on purpose, I don't know where they learned their trade, but they probably don't have any sort of mass distribution on their mind. I know when I went to school the first thing they said was, don't have stereo tracks that are out of phase. And the thing about no self-respecting engineer, those were the exact words the teacher used.

The point is this, if there is cancellation, you won't completely avoid it by running in stereo. In the interest of trying to not step on any toes, I'll stop here.

 

yes, any down-mixing is done after the DAC, not before or inside. the amp deals strictly with analog signals, not digital. if anything, it is done right before/after the internal amp or pre-outs. what most of us are saying is that it is pretty pointless to run subs in stereo in a car. the cabin is too small to fully develop most (if any) bass frequencies. a sub should be crossed over below 100hz, with most competitors at 80hz. those frequencies are omnidirectional. furthurmore, most of the lower ones are felt more than heard. with both subs within an inch or two of each other, you're not going to have much of a division of where the sound is coming from. if you can locate where the bass is coming from, the install has not been done right. it should appear to be coming from up front. your front speakers should be what is making the bass directional (due to the harmonics of the instruments/synths/samples/etc). when you did your switch AJ, did you do the same song? or different songs? where did you switch (amp, rcas, hu?) and how?

 

Yup

Quote:

or different songs?

Nope

Quote:

where did you switch (amp, rcas, hu?)

Uh...... in the shop.
Seriously, at the crossover. It was actually an EQ. The Alpine 3311. On the back it has two switches. One's for 0*-180* phase, and the other's "Mono-Stereo".

Quote:

and how?

The end of a test light. It's the only way to get at the switch since it's "sunk" (not flush) into the back a little, as a lot of switches on amps are.

This was ~13 yrs ago, so forgive me if I don't remember all the model numbers, but as I said, there were two 8's mounted in a sealed enclosure that was divided into two chambers. The box was mounted on the back deck above the well and the subs were firing up.

I can't say there was "stereo seperation" per say, but it was more "rich" sounding. We let the customer listen to it both ways and even he agreed that the stereo sounded better without knowing which was which while we were doing it.

 

What do you mean by rich, exactly? Was this improvement noticible in all songs, or just certain ones? I'm guessing that what happened was that each side was playing complimentary waves. I remember reading something about randy rhodes (who was ozzy's guitarist) used to do two takes of his solos. Then he'd put one all the way to the left and one all the way to the right. It was the same solo, but just by human nature it would be a tiny bit different in each take. The idea was that the differences in the left and right channels would create a "phantom guitar" in the middle. I'm just wondering if maybe the same principle was at work in your example.

I still have to believe tho that if going in stereo produced even a noticable difference in the bass that there would be far fewer people running their subs in mono. Also, what about dolby 5.1, why would they only run one sub as opposed to stereo. I dunno, I suppose that's a bit far afield from car audio.

Thanks for the info AJ!