ThraxXx

Hello,

a few years back I bought 2 KAC 929 kenwood amps. They are 1000watt peak, 2 channel amps. Now I downloaded the PDF manual for it and they say the following about the amp

High Quality 2 Channel Power Amplifier
1000 Watts Max
150 W RMS x 2 at 4 Ohms
230 W RMS x 2 at 2 Ohms
460 W RMS x 1 Bridged 4 Ohms
Variable Low Pass Filter 50-200 Hz (18dB/oct)
Bass Boost +6db/+12db at 90 Hz
Additional Speaker Level Input for Easy Upgrade
261 X 57 X 350 mm

Now what I noticed here is it says 460 W RMS x 1 Bridged at 4 Ohms. I then pulled the plate off of my stereo and realized that the guys at the shop wired up my subs wrong. They bridged the amp to 460 watts RMS however only wired the amp up to 1 of the 2 voice coils. The second coil has nothing on it. Now what I am wondering is this. If I were to bring that bridge down from 4ohm to 2ohm by running the coils in paralell with the amp...what could be the side effect?

If doing this is impossible...what would you recomend I do? Please don't request replacing the amps with better ones...I like these amps and my baffle board was designed for these bad boys.

ThraxXx

Guess no one has the answer... I posted this question on a few other boards and they are also unsure. Guess I will run the amp in stereo to avoid a smoke show.

syc0path

So u have 2 amps and 2 DVC subs? And they only hooked up 1 coil on each sub? I think u've already answered your own question, but I need more info to tell u for sure.

ThraxXx

yeah I have 2 Kenwood KAC 929 subs. Each amp powers its own independant sub.

The subs are Premier dual voice coil subs and each coil is running at 4ohm. Now the guy who hooked it up didn't understand the Dual Voice Coil logic so he bridged the amp and ran it into 1 voice coil.

I did some research on the DAC 929 amp and it shows that when bridged the sub can only do 460watts RMS @ 4ohm. There is no stats on running the amp at 2ohm.

So what I am wondering is..if I ran the KAC 929 in paralell and wired up the second voice coil the amp would drop down to 2ohm...would the amp blow up?

aaron7

iTrader: (7)

I have one KAC-929S amp, and I love it!

I have 2 DVC subs, both are wired in parallel to the bridged amp. Not sure if this is the best way, but that's how I have it.


Horrible drawing, but you get the idea.

syc0path

The reason why it isn't rated bridged into 2ohms is becuz very few amps can handle that load. I doubt those Kenwoods can. Unfortunately, those subs are not a good match for those amps. They should have given u SVC subs. U could try to go back to the shop and bitch and see if they'll exchange them, but I doubt they will if it's been a while since the install.

The correct way to hook up DVC subs to a 2ch amp is to run the coils in series and hook it up to the bridged channel. That works fine if the subs have 2ohm coils, or if u'r hooking a DVC sub w/ 4ohm coils to a home system. But in your case, it would give the amp an 8ohm load and cut your power in half. The shop screwed up, and there's really no good solution.

aaron7

iTrader: (7)

The 929 does support 2ohms.

ScrapMaker

can you link the amplifiers together to get gigantic bridged output at 2ohms?

if those amps are perfectly stable at 2ohms, while bridged, then you should be good to go... otherwise you're screwed, and they shouldn't have sold you that setup.

if it can do 2ohms bridged, then you're all set.

aaron7

iTrader: (7)

Just like how I suggested above. That's how I have mine.

ScrapMaker

oops, I meant, can you connect one amp to the other, and create a "single amplifier," to achieve an overal 2 ohm-stable system?

if the system is 2ohm-stable for a single amp, then you're all good, as aaron7 pointed out... but that is a rare quality of an amp. I guess you have a nice amplifier.

syc0path

In stereo, but not bridged. Here's a write-up I wrote that should explain things...

Modern amps are wired so that the L+ terminal is connected to a voltage rail that produces power, and the L- terminal is just a ground. No surprises there. But the right channel is different -- the R+ is a ground, and the R- is the voltage, 180* out of phase w/ the L+. This works just fine in stereo, becuz even though the 2 voltage rails have opposite polarity, they connect to opposite ends of the speaker coil – the 2 “opposites” cancel each other out and the end result is that the R channel remains in phase w/ the L channel. The advantage of this design shows up when u want to bridge the amp.

Voltage is like pressure -- it's a measure of how hard the electricity pushes thru the circuit. Amperage is the amount of electricity moving thru the circuit. Wattage is the power moving thru the circuit -- it equals V*A. And resistance is measure of how hard it is to move electricity thru the circuit.

Let's consider a hypothetical 100WRMSx2 amp. In this case, the voltage rails would put out 20V. So the voltage difference from the L+ to the L- is 20V, and it will be able to push 5A thru a 4ohm load (20V*5A=100W and 20V/4ohm=5A). If u connect the L channel to a 2ohm load, u will have 1/2 the resistance, so the amp will be able to push twice as much amperage thru the speaker. So the amp will put out 200W (20V*10A=200W). If u run both channels at 2ohms, u'll get 200W+200W=400W total power.

But when u bridge the amp, u use the 2 channels so that one "pushes" electricity thru the circuit while the other "pulls". When u go from +20V on the L channel to -20Von the R channel, u have a 40V differential -- u've doubled the voltage. But now that the voltage is doubled, there's twice as much pressure, so the amount (amperage) flowing thru the circuit is also doubled. Twice the voltage * twice the amperage = 4 times the wattage (40V*10A=400W). Note that this is exactly the same amperage going thru each channel and exactly the same total wattage as running both channels in stereo at 2ohms. That's why bridging into a 4ohm load is the equivalent of running the amp in stereo at 2ohms. And as u might expect, bridging the amp into a 2ohm load is the equivalent of running the amp at 1ohm stereo -- and most amps aren't stable like that.

This also explains why u can only bridge 2 channels together -- u can't do more than that.

aaron7

iTrader: (7)

Well, mine has been working @ 2ohm for 3 years now, bridged with 2 DVC subs... no issues yet!

syc0path

What ohm are the voice coils? If they're standard 4ohm coils, then there's no way to combine them to create a 2ohm load (unless u'r only using 1 coil per sub like they did to ThraxXx)

Like I said, most amps aren't stable if bridged into a 2ohm load... but some are. I have an old RF amp that I ran bridged into a 1ohm load (2 DVC subs w/ all coils in parallel) for over a yr! It still works fine... in fact, it's bridged into a 2ohm load (2 SVC subs) in my TA right now. So it certainly can be done, but Kenwood amps aren't exactly known for being underrated.

aaron7

iTrader: (7)

Hmm, seems like my 2 subs have dual 4ohm voice coils. They are wired like the crappy paint picture I posted above. So what ohmmage am I running?

BTW, sorry about the hijack!

ScrapMaker

honestly, I cannot tell what's going on in your picture, but if I THINK I know what it means, you would be running a 1-ohm load... and I believe it's possible to do this on a 2-ohm-stable amplifier, as long as you keep the gain WAY down, right?

We talked about this in a thread a few months ago... someone chimed in about the Signal-to-Noise ratio, as well as a few other factors involved with using lower-than-intended ohm loads.

really, aaron7, you need two separate amplifiers for your setup... or one good one that is 1-ohm stable...

either you're running each sub at 2-ohms, or they are running at 8-ohms.

so with both subs running at 8-ohms together, you get an overall 4-ohm load, which is all you can get from a 2-ch amp bridged.

case closed.

ThraxXx

Well I brought this question to the leader of our car audio club and he knew someone with one of these amps so he decided to see if it would go 2ohm. The amp held up for him so he then got crazy and wired it down to 1ohm. The amp held 1ohm for 45 minutes doing an 80hz burp. He decided it was getting too anoying so stopped the test however the amp didn't get all that hot. This past weekend I decided to wire both amps down to 2ohm stable. I replaced the ghetto 16guage speaker wire they gave me with 10guage speaker wire that I had laying around from when I wired up my other car. After getting everythign wired up I fired up the stereo and MAN!! now I have bass...The amps should hold their own and if they don't then I will replace them with something that will.

ScrapMaker

if it was any work at all, then you probably wasted your time with the larger diameter speaker wire... it's not nearly as important as you might think.

so you have roughly 400 watts RMS per sub now? that's pretty good, and I'm glad you got the situation fixed.

ThraxXx

Well here is the thing. the amps say that they will do 460watts rms at 4ohm. I just dropped the amps down to 2ohm. Doesn't that double the wattage or at least increase it?. Is there anyway I can hook up some meter to the sub to see how much wattage is going too the subs?

ScrapMaker

In theory it's twice as much power, since the resistance is half. In reality it's more like 80%

you probably have around 730RMSwatts

NEEDAZ

Not easily...

syc0path

They're running at 2ohm stereo (ie, both channels have a 2ohm load). U could rewire them for a 4ohm load and then bridge your amp into that... but u probably wouldn't be able to hear the difference.

U don't necessarily need a different amp, as long as the amp u have is putting out close to the RMS rating of the subs.

ScrapMaker

you can use a device to measure the amperage being drawn by the amp... then if it' a d-class amplifier, it's about 80% efficient.

Lets say it draws 70 amps. 70 amps x 0.8eff = 56 amps x 13.5v = 756 watts.