# XD600/6 JL Audio quality?



## S141995 (May 18, 2006)

I'm now using a Zapco 1000.4 and I need more space for my hunting trip so I'm thinking selling my zapco and switch for a XD600/6. Anyone ever use it ? What about the quality ? I know it won't be the zapco but I really need my cargo space and the small size of the XD amp make them interesting. Thanks for your advice


----------



## chefhow (Apr 29, 2007)

Actually JL makes EXCELLENT quality products. They last, they work and they stand behind their product as long as its bought via an AUTHORIZED dealer.


----------



## FAUEE (Jul 22, 2010)

chefhow said:


> Actually JL makes EXCELLENT quality products. They last, they work and they stand behind their product as long as its bought via an AUTHORIZED dealer.


This man speaks the truth. JL has some of the best quality products out there. Easily the best mass market, and better than most of the low volume "boutique" types too.


----------



## OldSchoolRF (Aug 29, 2011)

I agree. JL puts out a quality product. I've owned a few of their amps and a couple different W7s. If you can find the equipment used so it's a little cheaper it's even better.


----------



## 91dime (Dec 17, 2008)

I just got a 600/6 for $330 from crutchfield. Its a refurb, but to be honest I have never bought an amp from a store that wasnt.


----------



## blackknight87 (Jul 11, 2011)

I have an XD700/5 amp and i really like it. I say go for it.

Its very small but packs a punch.


----------



## OldSchoolRF (Aug 29, 2011)

Nice. Pretty good deal. Let us know what you think about it compared to the Zapco.


----------



## 91dime (Dec 17, 2008)

I'd like to hear what some other people think about this amp?


----------



## tintbox (Oct 25, 2008)

I have a buddy mine running two of the xd amplifiers and they are amazing to say the least.


----------



## Jsracing (Apr 1, 2011)

I find the XD amps to be very clean. Some people claim to hear the switching. Instead of outright me dating tours false, I'll just say that switching frequency is 400khz, do if they can hear that, then they have the best ears ever.
I also have an old Zapco comp amp and unless I do an immediate A/B swapping between the two in the same car, its extremely difficult to hear a difference. If I do the swapping too slow, its virtually impossible (keep in mind auditory memory is only good for a couple od seconds at best). So yes, its a clean sounding amp that's well made. Go for out and enjoy having trunk space again.


----------



## FartinInTheTub (May 25, 2010)

If I were you I would pick yourself up a used JL HD 600/4. This will give you the power you had with your Zap and make you smile in the meantime.


----------



## trojan fan (Nov 4, 2007)

Bought my first JL sub back in 1993 and been onboard ever since


----------



## cleansoundz (May 14, 2008)

JL makes good stuff. I used the JL 300/4 and 500/1 in my truck for 5+ years easy.


----------



## 91dime (Dec 17, 2008)

The w6 sold me, but I have zero experience with their Amps.


----------



## S141995 (May 18, 2006)

Thanks to all of you ! 

I bought a JL audio amp back in 96 so I know they do quality product. 

The size of those amp are crazy I'm too used with big size amp


----------



## Lorin (May 5, 2011)

Im going to try some of the jello cool-aid. I purchased a refurb xd600.6 for myself.


----------



## trojan fan (Nov 4, 2007)

S141995 said:


> Thanks to all of you !
> 
> I bought a JL audio amp back in 96 so I know they do quality product.
> 
> The size of those amp are crazy I'm too used with big size amp



....And what amp might that have been  :laugh:


----------



## S141995 (May 18, 2006)

It was'nt in 96 , In 96 I was running 2X Orion 2100 HCCA ! That's back in the time ! I was running Jl's around 2000 2001 finally ,,,


----------



## Lorin (May 5, 2011)

I just received my refurb xd 600\6 from crutchfield. Tiny is putting it mildly. Very small footprint to say the least. I wont have it hooked up for a bit, but am looking forward to it.


----------



## fish (Jun 30, 2007)

Lorin said:


> I just received my refurb xd 600\6 from crutchfield. Tiny is putting it mildly. Very small footprint to say the least. I wont have it hooked up for a bit, but am looking forward to it.


Does it feel pretty solid, heavy?


----------



## Lorin (May 5, 2011)

Seems like a solid amp, you are welcome to take a look next time we get together. Still amassing parts before starting on the install. If it works as advertised, I will be one happy camper.


----------



## Neil_J (Mar 2, 2011)

Jsracing said:


> I find the XD amps to be very clean. Some people claim to hear the switching. Instead of outright me dating tours false, I'll just say that switching frequency is 400khz, do if they can hear that, then they have the best ears ever.


It's not the switching frequency that's being heard. It's the artifacts that are left after they're filtered out via a low-pass filtering network (some of the artifacts will be in the 20-20khz range). Some amps like the Zed and JL HD's will apply global negative feedback after the filtering section which works very well to remove distortion, but adds cost and complexity. The XD series instead chose to skip the global feedback and just did a very good job of making the filter do it's job. It works quite well, but no filter is perfect, there will be non-linear artifacts left that will be superimposed on the audio output. These artifacts total to a fraction of a percent distortion, so we're splitting hairs here. Most people will never hear it. I own one and I'm still not certain if I can hear it, or is it the reverse-placebo effect.

I'm in the process of characterizing these artifacts now with test equipment and my ears. I can say so far that the distortion is so low that it will be difficult to measure.


----------



## Jsracing (Apr 1, 2011)

I'd be very interested in your test results. If they are hard to measure, they won't be heard. I understand the artifacts, they're intermods. The reason I specifically stated the switching frequency of the XDs, which is the same as the HDs, is so far above the the audible range that their relative levels are too low to be heard. Whatever people believe they hear is placebo or other sonic signature. Regardless of how little distortion the amp or drivers generate, their operating environment creates more distortion than than the amp switching.


----------



## Neil_J (Mar 2, 2011)

Jsracing said:


> I'd be very interested in your test results. If they are hard to measure, they won't be heard. I understand the artifacts, they're intermods. The reason I specifically stated the switching frequency of the XDs, which is the same as the HDs, is so far above the the audible range that their relative levels are too low to be heard. Whatever people believe they hear is placebo or other sonic signature. Regardless of how little distortion the amp or drivers generate, their operating environment creates more distortion than than the amp switching.


Very true, there's no use pairing a low-distortion amp with a crappy set of speakers. My first install with the XD700.5 was with two pairs of JL C2-570x coaxials and a 12W1v2-4 sub in a mismatched box, with no DSP or equalizing. I was running them beyond the amp's rated power, so I can't really say what I was hearing. This time around, I'll be testing them with a T/A'd, equalized, 3-way active setup with Hybrid Audio L3SE's, L1 Pro R2's tweets, and L6SE midbass drivers. That should eliminate most of the variables right there.

I just bought an HD900/5 a few minutes ago, so I will be able to compare it to my XD700.5. I also have a few oldschool class A/B amps I'll be trying as well. I hope to put this myth to end very soon


----------



## Jsracing (Apr 1, 2011)

Sweet. If i could take my amps to work, I'd put them on the Spec A and really do a detailed frequency sweep, but alas I can't bring in non work stuff. It would be easy then ti see how many dBc the intermods are within the audibile range.


----------



## Neil_J (Mar 2, 2011)

Jsracing said:


> Sweet. If i could take my amps to work, I'd put them on the Spec A and really do a detailed frequency sweep, but alas I can't bring in non work stuff. It would be easy then ti see how many dBc the intermods are within the audibile range.


I work in the test and measurement field and have access to all that stuff, although I'll probably be buying/making/improvising most of my equipment at home. These class D amps really intrigue me: there's so much wiggle room for quality between brands and models... I could hear two dozen conflicting stories on this forum about how "musical" or "clinical" they do or don't sound.. but why not just measure the damn thing?? I wouldn't trust a vendor or trade publication to do it due to conflict of interest... but I certainly trust myself to do it. Everything else is Kool-Aid and forum boners. And yea, if I ever compete in SQ events, I'd like to get as close to zero distortion as possible throughout the whole system, and when you get competitive, you gotta take matters into your own hands, rather than blindly following everyone else.

If you ever get your hands on that Spec An... Make sure to impedance match it to 50 ohm and attenuate it to 20 watt or whatever its max is, or you will end up with a $120,000 paperweight :surprised:


----------



## Jsracing (Apr 1, 2011)

Thats awesome. I wish I could access the equipment in my labs. I'm an amplifier engineer (not audio), so I have equipment around, but can't use them for non work. No worries with the spec a, I'd use a coupler so the input won't see much power. Really looking forward to your test results. IMO, even for SQ comps, most distortion would be inaudible...the problem is no ones bothered to measure the levels.


----------



## Neil_J (Mar 2, 2011)

If I can't hear a difference between the HD900.5 and the XD 700.5, I'm selling the HD


----------



## UNFORGIVEN (Sep 25, 2010)

I've heard the JL XD's in person and I have to say they sound fantastic. Somewhat pricey but you get what you pay for and these are quality in a compact package. 

I say go for it.


----------



## subwoofery (Nov 9, 2008)

A german mag did test the XD and HD line... 

From what I've gathered, the XD line has a lower noise floor (S/N ratio) than the HD (87dB vs 99dB) - 4 channels. With the XD700/5 being the best @ 102dB. 
The XD line is more efficient (76.1% vs 88.6%) - 4 channels 
Distorsion is low enough over the whole bandwith except for the XD600/6 which is much higher than the other HD and XD amps - the XD600/6 will obviously sound the warmest... 
Construction is similar for both lines (HD gets 8/10 and XD get also 8/10) 

IMO, the HD is only good if you need more power... If not, get the XD. 

Kelvin


----------



## Jsracing (Apr 1, 2011)

Neil_J said:


> If I can't hear a difference between the HD900.5 and the XD 700.5, I'm selling the HD


Get some help so you make it a blind test. Any knowledge of what youre listening to will taint the results.
I agree with kelvin, the HD offers more power but the other enhancements aren't worth the price.


----------



## Neil_J (Mar 2, 2011)

Jsracing said:


> Get some help so you make it a blind test. Any knowledge of what youre listening to will taint the results.
> I agree with kelvin, the HD offers more power but the other enhancements aren't worth the price.


Dunno, I just payed $630 for a HD900.5 refurb, not bad (70 cents a watt). That's only $150 more than what I payed for the XD700 new.

Yes the listening tests will be 100% blind, that's the only way to do them IMO


----------



## Jsracing (Apr 1, 2011)

I got my XD700/5 for MUCH less, so it was worth it, but if I could get an HD for near the same price, I'd do it too. Though I like the more flexible preamp stage of the 700/5.


----------



## t3sn4f2 (Jan 3, 2007)

subwoofery said:


> A german mag did test the XD and HD line...
> 
> From what I've gathered, *the XD line has a lower noise floor (S/N ratio) than the HD (87dB vs 99dB) *- 4 channels. With the XD700/5 being the best @ 102dB.
> The XD line is more efficient (76.1% vs 88.6%) - 4 channels
> ...


-87dB is _way_ too low a figure for a high quality amp like the HD. It's S/N ratio was probably measured at 1 watt and the XD at rated power.


----------



## t3sn4f2 (Jan 3, 2007)

Jsracing said:


> Get some help so you make it a blind test. Any knowledge of what youre listening to will taint the results.
> *I agree with kelvin, the HD offers more power but the other enhancements aren't worth the price*.


I think the regulated PS in the HD's is a great thing when listening to the car with the engine off and using a stock undersized battery. That's where critical listening really happens.


----------



## subwoofery (Nov 9, 2008)

t3sn4f2 said:


> -87dB is _way_ too low a figure for a high quality amp like the HD. It's S/N ratio was probably measured at 1 watt and the XD at rated power.


Nope... Both measured the same way - @ 1% distortion: 









Kelvin


----------



## t3sn4f2 (Jan 3, 2007)

subwoofery said:


> Nope... Both measured the same way - @ 1% distortion:
> 
> 
> 
> ...


Thanks for the review. I'll comment more tomorrow on it. Particularly S/N ratios at max power comparisons, for amps that don't have equivalent max ratings. And for amps with different minimum gain settings, which is where amps are measured at (ie XD 4V, HD 8V = difference of 6dB of noise floor). 

If specs or measurements aren't specified like this Audio Specifications, don't put too much stock in them.


----------



## kmarei (Nov 13, 2009)

subwoofery said:


> Nope... Both measured the same way - @ 1% distortion:
> 
> 
> 
> ...


Do you have the figures for the XD700/5?


----------



## subwoofery (Nov 9, 2008)

kmarei said:


> Do you have the figures for the XD700/5?


Yes but it's pretty useless. They only give the power output and the drawing: 
XD600/1 
S/N 54dB
1 x 412Watt an 4Ω (34A) 
1 x 702Watt an 2Ω (61A) 
XD700/5 
S/N 102dB
4 x 79 Watt an 4Ω (35A) 
4 x 120 Watt an 2Ω (60A) 
2 x 71 + 1 x 266Watt an 4Ω 

That's all I have... 

Kelvin


----------



## Jsracing (Apr 1, 2011)

t3sn4f2 said:


> I think the regulated PS in the HD's is a great thing when listening to the car with the engine off and using a stock undersized battery. That's where critical listening really happens.


While I think the technology is great and an improvement, I've never heard a difference in output or clarity from any of my amps between the car being on and turning it off. The regulated PS should make a difference in measurements, but I've found no audible difference and thus the cost difference is not justifiable for me.

Subwoofery - any numbers for the HD? Curious to see those. The XD numbers look great, and seems underrated. The sub channel puts out quite a bit. My friend's eclipse amp puts out a solid 150w for the sub, s and the same sub on my XD700/5 was considerably louder and hit harder, even though the rated power isn't much different between his amp and mine.


----------



## kmarei (Nov 13, 2009)

subwoofery said:


> Yes but it's pretty useless. They only give the power output and the drawing:
> XD700/5
> S/N 102dB
> 4 x 79 Watt an 4Ω (35A)
> ...


perfect thank you 
it puts our 20% more into 4 ohm than the advertised specs
and 266w is 30% more than stated specd into 4 ohm bridged
so my suspicions that the 700/5 was simply a 600/6 with 2 channels bridged are unfounded 

that's it
i'm getting me a 700/5!


----------



## Neil_J (Mar 2, 2011)

kmarei said:


> perfect thank you
> it puts our 20% more into 4 ohm than the advertised specs
> and 266w is 30% more than stated specd into 4 ohm bridged
> so my suspicions that the 700/5 was simply a 600/6 with 2 channels bridged are unfounded
> ...


I'd say it's more of an XD400/4 and XD300/1 love-child.


----------



## subwoofery (Nov 9, 2008)

Jsracing said:


> While I think the technology is great and an improvement, I've never heard a difference in output or clarity from any of my amps between the car being on and turning it off. The regulated PS should make a difference in measurements, but I've found no audible difference and thus the cost difference is not justifiable for me.
> 
> Subwoofery - *any numbers for the HD?* Curious to see those. The XD numbers look great, and seems underrated. The sub channel puts out quite a bit. My friend's eclipse amp puts out a solid 150w for the sub, s and the same sub on my XD700/5 was considerably louder and hit harder, even though the rated power isn't much different between his amp and mine.


What do you mean any numbers? Everything is in my post... 

Kelvin


----------



## JITTO (Dec 31, 2012)

subwoofery said:


> A german mag did test the XD and HD line...
> 
> From what I've gathered, the XD line has a lower noise floor (S/N ratio) than the HD (87dB vs 99dB) - 4 channels. With the XD700/5 being the best @ 102dB.
> The XD line is more efficient (76.1% vs 88.6%) - 4 channels
> ...


Hi Kelvin, i have a little question, what does you mean by warmest sound? 
Coming from the world of guitar amplifiers, warmer means better, is it the same for car amplifiers?

Thanks!

FYI: i'm planning to replace my MRX-F65 with this unit for going active and amplify a pair of focal krx2 (tweeter on one channel and mid on the other) and a set set on Focal PS165 on the other channel, all in one amplifier... all of these comming from an alpine pxe-h660.


----------



## Victor_inox (Apr 27, 2012)

I have XD 600.6 and 600.1 amazing little ****ers, whoever says that he can hear switching outright lier, period.  they sounds great, powerful and quick. If space were a concern I`d switch from zapco in a heartbeat, I have dc1000.4, 650.6, 750.2 and 200.2 I have something to compare it with, tunability of zapco is great but if you don`t need it then switch without second thought.


----------



## Jsracing (Apr 1, 2011)

JITTO said:


> Hi Kelvin, i have a little question, what does you mean by warmest sound?
> Coming from the world of guitar amplifiers, warmer means better, is it the same for car amplifiers?


Not Kelvin, but if you don't mind...
typically 2nd order distortion is described as sounding "warm". This is contrary to 3rd order (and other odd harmonics) which sound harsh (sometimes inaccurately described as detailed due to additional energy added in at those frequencies from their higher order odd harmonics). The high even order distortion of tube amplifiers is what gives them their "warm" character.
Whether it's "better" depends on the character of the sound you like.


----------



## Neil_J (Mar 2, 2011)

Jsracing said:


> Not Kelvin, but if you don't mind...
> typically 2nd order distortion is described as sounding "warm". This is contrary to 3rd order (and other odd harmonics) which sound harsh (sometimes inaccurately described as detailed due to additional energy added in at those frequencies from their higher order odd harmonics). The high even order distortion of tube amplifiers is what gives them their "warm" character.
> Whether it's "better" depends on the character of the sound you like.


^^^ What he said. Even harmonics sound heavenly. Not all distortion is created equal.


----------



## t3sn4f2 (Jan 3, 2007)

And just to add, this warm thing only applies to tube amps where there is an actual difference in dBW between inaudible distortion levels and high even ordered ones. The XD amp would simply sound clean at ~75 watts and the at ~80 watts it would be clipping grossly. There is no wiggle room in there to even begin to hear the onset of distortion, much less the type. And to add this would be on the tip of music peaks, not the constant average wattage level.

Below are output wattage versus distortion graphs for a tube amp and a solid state amp.

Tube:

Lamm ML2.2 monoblock power amplifier Measurements | Stereophile.com










Solid State:

Dan D'Agostino Momentum monoblock power amplifier Measurements | Stereophile.com









See how the tube amp has 15dB output (dBw difference between 1 and ~30 watts) from 1% to clipping, and the solid state has the typical ~.5dB!.


----------



## sirbOOm (Jan 24, 2013)

I've replaced XD-series in a car with a fairy good SQ (Hertz Hi-Energy active) setup with HDs. The before and after was hard to tell in a loud shop but the only difference I personally noticed was that the HD was louder and there was more midbass slap. That, though, could be attributable to higher power - which is what the customer was looking for.


----------

