Diff bewteen A/B and class D amps.

[gunz4me2 10+ year member]

It's actually the opposite IIRC. Higher ohm load = higher DF, and DF get cuts in half with the halving of the ohm load. Basically high DF = good and low DF = bad, but when it actually makes a difference is anyone's guess and generally left to personal opinions and preferences.
Just wondering, since you said that DF doesn't matter yet you won't run a sub amp at 1ohm, what is the reason why you won't run it at the lower ohm loads? I ask because most people blame the low DF for bad transient response.

I still think damping factor is one of the most useless specs ever contrived by a marketing department to make one amplifier seem better than the other. Can one hear damping factor? Furthermore, can one detect a difference on subwoofers when the damping factor between amplifiers is 50, 100, or 200 keeping all other variables equal?

There are several flaws to damping factor. Most amplifier manufacturers just provide a number and are missing important things such as frequency and output impedance. This would be like quoting a high horsepower figure and not providing torque in the world of cars. In its truest sense, damping factor is load impedance divided by output impedance. Unfortunately, a subwoofer's impedance varies by frequency reproduced and so does the output impedance from the amplifier. Oh, and we can't forget the resistance caused by the speaker cables themselves.

The next flaw is many amplifiers picked different spots to measure damping factor. Spots such as the circuit board or the terminals on the amplifier instead of the leads connected at the driver itself. IIRC Orion and Rockford Fosgate were infamous for measuring at the circuit board where damping factor will be much higher. This was in the age where they used molex plugs thus causing resistance in multiple spots way before the subwoofer was connected.

Don't get me wrong, a high damping factor is usually necessary in the pro audio world due to the extensive runs of speaker cables, that can be located as far as 100 feet away from the amplifier. If the damping factor was low, the amplifier would probably go into protect or blow due to the back emf dumped into the speaker wires by the driver.

Lastly, damping factor generally makes the largest difference between 10 Hz and 400 Hz, hence the reason most generalize the damping factor argument on subwoofers.

Disclaimer: I am extremely tired and getting ready to go to bed. If I made an incorrect assertion, please feel free to correct me!

 

[Jaredturp 10+ year member]

I think a lot of companies will give the freq and ohmage, but with the varying imp it's probably not accurate right?

 

[cleansoundzz 10+ year member]

It's actually the opposite IIRC. Higher ohm load = higher DF, and DF get cuts in half with the halving of the ohm load. Basically high DF = good and low DF = bad, but when it actually makes a difference is anyone's guess and generally left to personal opinions and preferences.
Just wondering, since you said that DF doesn't matter yet you won't run a sub amp at 1ohm, what is the reason why you won't run it at the lower ohm loads? I ask because most people blame the low DF for bad transient response.

I can hear a difference in quality of music between 4 ohms and 1 ohm. Plus 1 ohm is much harder on the charger system, components inside the amp, etc, etc.

 

[rc10mike 10+ year member]

I agree.

I once had an RF Power 1000. Rated at 1000w at 1 ohm and iirc 250w @ 4 ohms.

I was powering two RF Punch HX2s at 1ohm and just to satisfy my curiosity, I switched the wiring to run at 4 ohms.

I instantly noticed that the bass was much more "detailed". The notes were more clear and defined. Granted I couldnt push it nearly as loud, the difference was there and noticeable. I know its hard to explain what you hear with words on a forum, but there was a difference.

 

[rc10mike 10+ year member]

Ive ran MOST of the best sub amps out there. Ive always ran the same subs in the same box. (two IDMAX 12's sealed).

Ive ran, a US Amps AX-2000, Zapco 9.0xd, JBL BPX2200.1, ARC 4000SE, even tried two JL 1000/1v2's.

They are all very impressive amps, but if I had the space, I would run the AX-2000 with a couple extra batteries. Its an A/B amp, so draws a LOT of current, but the sound from it is like none of the above amps I ran before.

 

[ConwayBang 10+ year member]

So a class d 1ohm load is prolly the most bad sound you can push to your sub but it is efficiant. See my friend wants something plenty loud but he really likes sq. I had a class d 1 ohm load and i thought the bass sounded clean and tight and low with a l7. Hes gonna get a 12 type r 2.15@32hz wana about 1000 watts to it

 

[rc10mike 10+ year member]

Tell him to buy my JL 1000/1v2 for $550 shipped.

 

[cleansoundzz 10+ year member]

I agree.
I once had an RF Power 1000. Rated at 1000w at 1 ohm and iirc 250w @ 4 ohms.

I was powering two RF Punch HX2s at 1ohm and just to satisfy my curiosity, I switched the wiring to run at 4 ohms.

I instantly noticed that the bass was much more "detailed". The notes were more clear and defined. Granted I couldnt push it nearly as loud, the difference was there and noticeable. I know its hard to explain what you hear with words on a forum, but there was a difference.

That is why I run everything at 2 ohms or 4 ohms if possible. The problems is that to find a class D that does 1000 watts at 4 ohms is either super big or super expensive. With the RF T1500-1BD CP that will be possible because it puts out 1000 watts at 4 ohms. Now is class AB amps had that high efficiency and didn't kill a person's charging system then that would be a different story. At class D @ 1 ohm vs. class AB @ 4 ohms-big difference. At class D @ 4 ohms vs. class AB @ 4 ohms no difference. At class D @ 2 ohms vs. class AB @ 4 ohms-very little difference. Again the class D must be a quality made class D amp.

Running any system at 1 ohm for subs is SPL and no SQ is involved.

 

[cleansoundzz 10+ year member]

This thread usually turn into fights because people get offended but all intelligent knowledgeable people are contributing their opinions without being offensive and sarcastic to other people.

I appreciate that.

Thank you.

 

[DBfan187 5,000+ posts]

I got some LOL's out of this thread.

 

[Jaredturp 10+ year member]

I got some LOL's out of this thread.

They are very present. Haha. Everyone knows it all.

 

[rc10mike 10+ year member]

I laughed at stuff too

 

[supermaxx123 10+ year member]

i liked the part about sq

 

[hispls 5,000+ posts]

The technology of class D has come a LONG way.

I can say first hand that the new Zed full range class D's sound every bit as good as class A/B, but you'll pay for them or any other full range class D that sounds good.

IMO for subs, it doesn't make too much difference since we generally can't even hear 5% distortion in the

Also I highly doubt any class D amp will run 80% efficient real world listening to music. Seems like possibly 80%+ with a sine wave at the most favorable frequency into a resistive load, otherwise, real world 60% average probably and closer to 40% or less for A/B.

 

[gunz4me2 10+ year member]

i liked the part about sq

If the amplifier employs any type of VI limiter, it is possible that some SQ is lost at lower impedance loads. Whether it is noticeable or not on a subwoofer, remains debatable, but it is a known fact that VI limiting can introduce artifacts into the amplifier's output.