I've done a lot of reading about car audio on this site and others, but have little hands on experience at installing amps, and none in working with a mono amp, so I find myself out of depth trying to figure this out. Any help you can provide would be much appreciated.

My friend recently decided to upgrade the low end audio of his 300zx TT. He ordered the appropriate JL Stealthbox (ebay) and since it didn't come with a sub also purchased a JL 10" w6. The w6 is a DVC sub and each coil has a 6 ohm impedance. My understanding is the best way to wire a single DVC sub is to wire the coils in parallel and attach a single Mono amp. The sub in parallel will have offer a 3 ohm load and everyone wins. As I understand it a 2 channel amp is not a good option because simply wiring each channel to a voice coil would offer a 6 ohm load and hence a relatively low amount of power, while bridging the amp would create a 1.5 ohm load which is too low for the amount of $$$ available to spend.

All that background (besides to reassure me my understanding of the set up is correct) is to set up me being completely baffled when I walked into Best Buy yesterday (friend purchasing equipment wants to charge it to his Best Buy card, I know that isn't the optimal purchasing location) and looked at their selection of TWO total mono amps. While looking at one I noticed it had 2 pairs of speaker connectors, labeled A and B. This blew me away. I have been under the impression that a mono amp was basically a 2 channel amp divided in half, and hence would have one pair of outputs. If there are two sets, how does that affect the wiring stats of the amp (for instance 200x1 at 4 ohms and 400x1 at 2 ohms). Do you just use 1 set of outputs, or do you bridge the 2 sets? Do all mono amps have outputs like this and if so whats the optimal way to handle the wirings? Thanks again for all your help.

P.S. The two amps available are a Kenwood amp (which is the one I checked out the wiring outputs on, the other was obscured by a cover) that promises 200x1 @ 4 and 400x1 @ 2 and also claims to be 1 ohm stable. The other choice, a Rockford Fosgate is $50 more expensive ($250 versus $199) and is weaker (150x1@4 and 300x1@2) but is CEA 2006 compliance. Does the third party standard make the Rockford amp worth the extra money? Thanks for this answer as well.

Links to the 2 amps are below

http://www.bestbuy.com/site/olspage.jsp?id...87&type=product

http://www.bestbuy.com/site/olspage.jsp?id...87&type=product

 

You can't bridge a mono amp.

The extra set of terminals is there to help you connect two subs (in parallel), i.e. connect one 4 ohm sub to terminal A and another 4 ohm sub to terminals B, the amp would see a load of 2 ohms. I guess this could be useful if you have the subs in seperate boxes (e.g. a left and right WLAURANT box in trunk).

So, it's basically just one channel

For you JL sub, connect the coils in parallel and then hook up the box to any set of terminals on the amp (it will see a 3 ohm load).

 

Thanks for your help Mas.

Do you or anyone else happen to have advice on my "P.S." amp decision?

 

First - good job on your question - some posts we see have so little information it's hard to help the person posting without asking a dozen questions.

Due to the variability in subs and amps there is not a single best answer. In general, as long as the amp can handle the impedance you will get more power by keeping the speaker impedance as low as possible. If you used a mono amp that can put 200W into both coils in parallel or a stereo amp that can deliver 100W into each coil separately, you end up with the same thing. Now that you have the sub, which amp is cheaper? (assuming other factors are similar). Since you're dealing with 6 ohm coils the mono approach is likely to be better in this case. But if they were 2 ohm coils it would be different.

One thing I need to correct (a technicality, I can't help it) is that bridging an amp does not change the impedance of the speaker, though it does change the effect of impedance on the amplifier. A sure way to "overload" an amp - connecting an impedance lower than it's rated for , either in regular or bridged mode. And since bridged mode typically is rated for twice the impedance of regular mode, you are correct in your assessment that bridging into 3 ohms has the same effect as regular into 1.5 ohms. But technically it's bridging into 3 ohms, not 1.5.

I don't have any info on the standard you mentioned, I wonder what's wrong with the existing standards, other than nobody follows them?

I can offer you this - I have a 4-channel Kenwood amp that is rated "400W maximum power", which of course means nothing because there is no engineering definition for maximum power. But if you read the specs they do say it's rated at 50WPC RMS into 4 ohms and 150W RMS bridged into 4 ohms. When I bench tested it I got over 60W stereo and 165W bridged, so at least Kenwood wasn't lying on the "real" RMS numbers. It's also been in my car for 4 years without a hiccup, and it's mounted in the trunk above the gas tank, pressed against the rear tray (limiting air circulation) so I'm quite happy with it.

.

 

This is for you, modifry, and other EE folks here:

http://www.jbl.com/car/support/AUTOMEDIA_CEA2006.pdf

If it makes sense to you please translate this into simple term for the rest of us.

Thanks!

 

Modifry: Thanks for your post and answer, as well as correction on my misuse of impedance when bridging. I think the Kenwood amp is the way to go after reading your experiences, though maybe a few others will chime in as well.

The CEA 2006 standard is something I have seen a lot on Crutchfield and on Rockford-Fosgate amps. Its supposedly a standard where the Consumer Electronics Assoc. will certify the RMS wattage of a product that pays some sort of fee, and then the product can display the logo. In Crutchfield only Alpine and Rockford use the standard, and its probably no coincidence that the very inexpensive amps don't, but I assume (and your experience with Kenwood seems to confirm) that not every company that doesn't use the standard is overrating their power.

I think I'll be able to give better advice to my friend now, thanks again for all your help.

 

the CEA 2006 standard actually brings some truth to amp ratings... the current standards are a joke b/c they are too flexible. the CEA2006 standards actually narrow the criteria to the point where you can actually feel confident that the power you're paying for is the power you'll get.
that stated? unless you know that a manufacturer over rates their amps (ie cheater* types), i'll take the CEA 2006 amp over another similarly rated amp anytime.

Bob (modifry) corrected quite a few of your misconceptions... i definitely agree -- great to see so much info out of the box!

like Bob said -- whether you bridge the amp or not, the impedence of the speaker doesn't change. so, if you see a 2 ohm stable mono amp, then a 3 ohm load (6 ohm DVC in parallel) will be absolutely fine.
the misconception you mention (ie a 1.5 ohm load) is a VERY common one that is often propogated by people who know just enough to get them confused and in trouble.

let me clear up some others...
when wiring up a sub, aside from working to best harness the amplifier's power, it doesn't matter whether you wire in parallel or series. when dealing with multiple subs, it's generally better to do voice coils in series and speakers in parallel. there's a fairly technical reason behind this involving electrical currents induced by moving coils in magnetic fields -- but don't worry about that. just keep the rule of thumb in mind.

99.9% of mono sub amps out there are NOT 2 channel amps made into 1 channel. they are class D amplifiers. they use a different type of amplifying technology that works better with low tones vs high tones. one benefit? they are generally more efficient, and generate way less heat. one drawback? they can be a bit less clean. chances are - you'll never notice the loss of clarity, but you will notice the reduction in heat...
as a note - most 2 channel and 4 channel amps are class AB amps. they are actually a hybrid between class A and class B amps.

long ago, i had a lot of success out of a Kenwood mono amp. mine was a decent and reliable little amp, that i got on the cheap. chances are, the Kenwood IS really 1 ohm mono stable, but produces no additional power with the change from 2 to 1. in fact, there may even be a switch on the amp for '1 ohm mono use.' that'd be typical.

regarding which to buy? it's your money.
looking at the RF specs:
i wouldn't be surprised if this amp was making more power than they are claiming on the spec sheet. RF does have a long history of producing 'cheater'* amps. still, the Punch series isn't their high end amps, so it probably isn't making much more than what is written on the box.

looking at the Kenwood it has pretty similar specs. they aren't known for making a ton of excess power, though Bob had good success with his.

honestly - do not think you can go wrong with either. check for features, adjustments, easy connectors, etc. that might make one more valuable to you. honestly, i think the Kenwood is ugly as sin...

what really bothers me the most, is that BB's stat sheets conflict themselves constantly... listing different powers in different places at the same resistance, etc. i'd check w/ the manuf. before i trusted their site or the in store info.


interesting aside? the RF amp is listed as a class A/B amp (both on BB's site and RF's site), and not D. that's unusual and relatively rare for a mono sub amp.


finally? go to this website. read much and read often. all your answers lay here. http://www.bcae1.com/


*cheater amps -- known by this because in competition you're classified based on your power ratings. these amps were deliberately rated low, to allow the owners to get into lower power categories while competing. they generally make more power than advertised.