REVIEW: Surprised by SQ of Class-D Full Range amps!! Alpine PDX, JL Audio, Etc

[VWBobby 10+ year member]

Hi Guys,

I had a chance to make it to a few local car audio shops and test some new equipment. Just thought I would give my 2 cents.

I generally ONLY like Class A/B amps for Midrange through Tweeter applications (Anything over ~80hz)

I decided to try the following amps:

Alpine PDX5

JL Audio HD9005, and HD7005

JL Audio 300/4v2 (Class A/B)

Rockford Fosgate Power T600-4

Speakers: Focal 165-KRX2 2-way components ($1200)

Head Unit: Kenwood DNX7180

I also tried misc JBL, Alpine, and any other speakers they had on display at the time (mostly models below $300). All 3 Focal models above $600 sounded similar other than "clarity". No noticeable cutoff or losses in frequency bands, just the $1200 set sounded more "clear"/accurate.

First impressions: All of the Class D amps have no audible noise/hiss when not playing material. Both the Rockford and the JL class A/B amps had audible hiss or noise when not playing material.

The Rockford T600-4 had perceptually more "punch" and loudness, BUT was not more clear and did not have the same full range sound as the other amps. First impression would say its "louder", though it was not gain matched to the other amps so appreciable volume is due to RMS/gain differences.

After 2 hours of listening to various types of music on HD Radio and CD, I determined the Alpine PDX5 and JBL HD9005 "sound" almost exactly the same. Level matched, I would say they would have the same equivalent perceived volume/loudness. Honestly, the only way I could tell which amp was playing was by looking at it. Sound difference was almost not determinable.

Bad camera pics of the demo wall at Car Toys:

Just thought I would post my findings! Let me know if anyone has any similar experiences or reviews!

Edit: Forgot to say, all of the Class D amps had 4 Gauge power connections. The salesman was telling me their installers only use 4 gauge with these amps and have no power demand issues (according to him).

-=Bobby //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Click to read more...

 

[gunz4me2 10+ year member]

I was torn between a pair of Kenwood Excelons (XR-4S and XR-1S) or Alpine PDX amplifiers (PDX-F4 and PDX-M6) and the JL Audio HD900/5 when I was planning on scaling back my system. I ended up going with the HD900/5 because of the tiny footprint from one amplifier versus a pair of amplifiers.

IMHO, the next gen full-range class d amplifiers from other manufacturers will be the future of car audio and I have a feeling that class ab will eventually go by the wayside. After all, there is no point in running huge, inefficient class ab amplifiers when something way more efficient is available in a much smaller footprint while offering the same, if not better sound quality.

 

[whitedragon551 5,000+ posts]

And people always had an issue when I said my full range class D Eclipse XA5000 sounds awesome.

 

[VWBobby 10+ year member]

Gunz4Me, you hit the nail on the head. These amps are TINY (for their output) and super efficient. Even after playing for a couple hours at moderate volume, they were barely warm, if at all. I was very impressed. I used to be a die hard 90's SoundStream/PPI/Rockford guy, but these things have got me thinking twice.

 

[Papermaker85 5,000+ posts]

Sorry but my ears can tell class d full range from a good AB or g/h design..

 

[Rich B 5,000+ posts]

Never trust comparisons made by listening to a dealer's sound display.

They arent known to set gains properly, and even a small output difference is known to influence people towards the slightly louder amp.

Its also not unheard of for some dealers to increase the gain on models they need to move.

 

[Why So Cereal? 5,000+ posts]

I run a PDX amp on my golf cart to some boston sr65 coaxials and a 8 inch woofer, and the SQ is great! granted, it is all out in open air so sq isnt quite as noticeable.

as far as power, its great!

 

[gunz4me2 10+ year member]

Never trust comparisons made by listening to a dealer's sound display.
They arent known to set gains properly, and even a small output difference is known to influence people towards the slightly louder amp.

Its also not unheard of for some dealers to increase the gain on models they need to move.

This is so true since most individuals can discern differences in amplitude versus differences in actual sound when amplifiers measure within 1 decibel of each other from 20 Hz to 20 kHz.

 

[Canaan 10+ year member]

This is so true since most individuals can discern differences in amplitude versus differences in actual sound when amplifiers measure within 1 decibel of each other from 20 Hz to 20 kHz.

Nailed it.

I have Arc Audio KS-mini and XDi amps in stock here at the shop.

I dare you to listen to them and hear a notable difference compared to similarly priced a/b amps.

Edit:

And the XDi-803 is a SICK amp for the average joe looking for nice sound on some comps and a small sub.

80x2 @ 4ohm for mid/hi

400x1 @ 2ohm for sub

I'm chomping at the bit to get a customer in an ARC 6.5" comp set and Sundown SA-12 or 2 ARC KS12 up and running //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[VWBobby 10+ year member]

Exactly...

I consider the speakers I was using as some of the best/most accurate I've ever heard. That makes it easier to decipher subtle differences.

I agree, most dealers don't set the amps to an equal playing field. Hell, most of them probably set gains by ear... //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

All variables aside, anyone would be hard pressed to pick out the actual SQ of the PDX or JL HD amps over a comparable class a/b. Again, the noise floor (hiss) I experienced with all the A/B amps was very evident compared to the class D's.

 

[Papermaker85 5,000+ posts]

noise floor?

You mean signal to noise ratio?

Anything above 80db a rated is high enough..

If your hearing noise at 0 volume level you have a pretty noisy cd player the a/b amps will tell you this while the class d will mask it..

If you understand how amps work the class d amps use a narrow bandwidth with a chip that just Modulates the original signal..While they can perform great above it's normal bandwidth it becomes increasing hard to control feedback and dampening among those frequencies.. The benefit is increased efficiency because it's ethier on or off which helps greatly over a/b amps

Where as class AB is much more linear through it's bandwidth ( and wider)so feedback is easily controlled ultimately you have better cone control and as Power increases it becomes increasingly harder to control..

Class g/h is similar in the theory of d except the g/h amps have output regulation threw several output rails

Instead of sampling and modulating a narrow bandwidth it's uses several rails or outputs by varing voltages only using the rail needed turning Others off(eliminating output threw switching between them)

Lower power/voltage loads use a specific rail while high output/voltage signal use the higher voltage rails

 

[VWBobby 10+ year member]

No I meant "noise floor". http://en.wikipedia.org/wiki/Noise_floor

I originally got started in guitar and pro audio equipment about 15-20 years ago.

Most amplifiers with minimal filtering are garbage in = garbage out. The more noise you start with, the more noise gets amplified (gain factor).

Yes, there was a a definite audible hiss/white noise with both A/B amps, especially the Rockford. I'm a big Rockford fan, so I'm not bashing them, but I did notice the most noise. Probably because an A/B amp has a constant A bias, and operates class B when used/pushed (from what I understand). This was tested with the deck off, just the amp(s) on and nothing playing. This was an A/B test, usually with 1 amp off, but I did leave one on standby but bypassed through the board for one test so I didn't have to wait for it to kick on for 1 or 2 listens.

Keep in mind, my hearing isn't what it was when I was 15-16, so if I can hear this now, I could imagine how disappointed I would've been back then... //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

I understand class D and G/H. That is why I was surprised to see a Full Range Class D that didn't sound like a servo motor controller. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif (has a digital harsh sound, instead of a tube amp warmth or transistor clarity). I wouldn't be able to tell by my ears with those 2 amps I demo'd.

 

[denim 5,000+ posts]

To me, the initial PDX models, seemed to be a little dirty on the higher ranges. But that was a few years back, and newer designs have improved. I am honestly very impressed by the latest ZED models.

 

[Papermaker85 5,000+ posts]

Did you find out where the nOise was coming from?

Chances are it's not the pre amp section..

 

[Papermaker85 5,000+ posts]

To me, the initial PDX models, seemed to be a little dirty on the higher ranges. But that was a few years back, and newer designs have improved. I am honestly very impressed by the latest ZED models.

They look nice..