# JL Audio XD vs HD amplifiers



## thebigjimsho (Jan 11, 2009)

While I'm really wanting an excellent SQ system in the Caddy, I'm wondering if I am going to be able to invest in all the components that I dream of or whether I'm going to get plain ole good components.

That being said, will the XD amps be good enough for me or will I really need to step up to HD amps? 

All this assuming I step up to an MS8 running off my factory h/u...


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## thebigjimsho (Jan 11, 2009)

I am out of it today. Guessing I should have put this in the Choosing Equipment forums...


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## kyheng (Jan 31, 2007)

Well, if you just want a "decent" SQ, XD will be good enough... If you want an "execelent" SQ, HDs are not for you, atleast Audison LRX and above.....


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## Thumper26 (Sep 23, 2005)

I think they're fine. Yeah Eldridge is sponsored, but he wouldnt use them if they weren't good enough. I've heard a difference between cheap amps and boutique stuff, but once you reach a certain point, the speakers, tuning, and especially install make a much bigger more noticeable difference.


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## TestTones (Aug 29, 2011)

I don't mean this to be rude but, even your experienced car audio shops that do installations in commerce generally can't answer your question making the online crowd typically as ignorant to such questions.

If you really want to know the quality of an amp, there are two ways to find out. One is to put it on a true RMS meter, thermometer and an oscilloscope, put a load on it then start hitting it with dB controlled test tones and watch how it responds to the variations in signal, specifically the low end. 
These is the low tech approach and obviously, it's costly equipment and not exactly all that low tech in truth of the event. You must be able to competently understand the data and apply it to real life conditions. 

The second way is to pull the amps open and look at all specific components. First, the amplifier chips. What is the name brand and model number on them. The name brand on the casing has nothing to do with what is inside of these units. These companies generally build their amp based on a schematic(for laymen a circuit blueprint) provided by the amplifier chip manufacturer. So it says JL Audio, HD, Jensen WHATEVER, doesn't matter. The brand of chip on the inside will often be a Hitachi or Texas Instruments etc and the core design that brand used to build their amplifier was *given *to them by the chip manufacturer which has been common practice now for close to a century!

So the first thing you do with those chip numbers is look up their data sheet as provided by the manufacturer. It will tell you the chips maximum potential output at a fixed voltage. That voltage is often 16 volts rather than the 12-14.4 99% of the automotive audio crowd is used to. You will also be able to determine what class of amplifier it is. Personally, I still think class D sounds the best *aside* from it's performance as recorded by data meters proving it to be cleaner and more power efficient. You will generally also see quite clearly that your chips are not capable of the claimed wattage and I don't care who's brand name is placed on the amp! 
If those chips put out 340 watts RMS @ 2 ohms, the brands that then build that circuit will tell you 500 watts RMS @ 2 ohms or whatever hopped up ******** RMS wattage they attained using a non standard test tone. Standard is 1 Khz so many will use a higher frequency, overdrive the amp and indeed, get that 500 watts of RMS out of it. 

Unfortunately, your question falls under the category of imperial brainwashing. 999,999 answers out of 1 million people asked will be based on brand loyalty which is of course unreliable. 

So here's what to look for.

First, and even before the chips, your transformer. Fortunately just about every company loathed or loved uses a round toroid power coil. 

Second, how large and how many power caps does it have. Are they name brand? This is an area in life where we *can *pay credit to brand names! 

Third, the amplifier chips. Now that we've had a good look at our power station, lets look at our engines. It's again where we can trust name brand manufacturers. Your amp may say Broblaster 8100XPA on the outside then on the inside, have Toshiba power amp chips. Truth be told, it's unlikely you will get a crap power chip. The issue here is, what is the maximum potential wattage output documented by the manufacturer.

Fourth, how many resistors and non polar caps do you see and what color are they. Burgundy or brownish red polypropylene caps are the highest grade caps. Second would be green, your polyester caps. Third and of course cheapest are your round ceramic disc caps. Ceramic caps produce their own unique distortion and are the cheapest caps that give highs the sharpest, crispest texture. Sometimes this is actually a very good cap to use but bottom line is if the amp has a lot of them, you might want to avoid that brand. You will get 100 ceramic caps for what it costs you to buy 10 polypropylene caps.

Fifth.
Op amps and transistors.
Do you see a lot or just a few. Some amps will have a half dozen op amps and 30 transistors. This is a very good sign because it means your built in preamp/crossover should have a very good dB range and is preamplifying, cleaning and conditioning your signal for further power amplification. 
However, it's also not crucial as one may think. A single op amp and a few transistors can make an excellent preamp and filtering circuit. 
What *is* crucial is the name brand and model number on these suckers. For one, a half dozen to a dozen brands can and do legally produce the same model number. You indeed want name brand op amps. Secondly, the most common op amp you see is the TL072 or JRC4558. Even without those letters, if you see those numbers you have one very crisp turd in your bag of chips! Unfortunately, you will *always* see these op amps in just about everything that uses electricity and makes sound. If you feel competent, replace them immediately with some T.I. NE5532's.

Lastly, your resistors. 
Are your resistors super tiny barrels or are they large barrels. Basically a red ant verse a big ass black carpenter ant. Second, what color are they. Are they blue or a tan color. Large tan resistors are generally the most desired. Resistors are hard to scorn because in some if not majority of cases, the type used makes absolutely no difference to the sound but in the few it does..well that's why I included this portion of the post. 

So let us recap.
Round power transformer.
Name brand chips like Hitachi, Texas Instruments etc.
Name brand power caps, how large and how many.
Lots and lots of resistors and capacitors. 
At least a couple op amps and a half dozen transistors.(generally this is what majority of your caps and resistors are connected to).

I've seen a lot of amps come and go for myself and others. Admittedly I've had more Brand-X gear than name brand but I've also experienced $50 amps with about 20 pieces to the entire circuit take 20 years of abuse in just 2 and survive! Then one minor incident from wire tinkering kills them dead as a doornail where your amps with 200 part counts aren't going to take any level of damage. It's unfortunately a question that isn't open for academic debate because there is no reliable let alone factual answer.


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## thebigjimsho (Jan 11, 2009)

Well, I'm thinking JL Audio mainly because my old installer works for them...


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## thebigjimsho (Jan 11, 2009)

And because of their reputation...


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## trojan fan (Nov 4, 2007)

kyheng said:


> Well, if you just want a "decent" SQ, XD will be good enough... If you want an "execelent" SQ, HDs are not for you, atleast Audison LRX and above.....


That's a very very subjective opinion.. you would need a very special pair of ear to hear a double the price difference



Thumper26 said:


> I think they're fine. Yeah Eldridge is sponsored, but he wouldnt use them if they weren't good enough. I've heard a difference between cheap amps and boutique stuff, but once you reach a certain point, the speakers, tuning, and especially install make a much bigger more noticeable difference.


x2...exactly right......Imo speaker make a lot more difference then amps


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## Thumper26 (Sep 23, 2005)

Def speakers, but I feel install is much more of a difference. Either one of those lines will work great. I think the hd's are better, but the xd's are more than enough, esp with using the signal from a factory deck. It seems you're still just getting into active setups, so I'd esp save the money from the hd's and be sure to buy an rta solution or spend it on the speaker install.


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## trojan fan (Nov 4, 2007)

TestTones said:


> I don't mean this to be rude but, even your experienced car audio shops that do installations in commerce generally can't answer your question making the online crowd typically as ignorant to such questions.
> 
> If you really want to know the quality of an amp, there are two ways to find out. One is to put it on a true RMS meter, thermometer and an oscilloscope, put a load on it then start hitting it with dB controlled test tones and watch how it responds to the variations in signal, specifically the low end.
> These is the low tech approach and obviously, it's costly equipment and not exactly all that low tech in truth of the event. You must be able to competently understand the data and apply it to real life conditions.
> ...




easy....You are going to get the OP confused


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## kyheng (Jan 31, 2007)

trojan fan said:


> That's a very very subjective opinion.. you would need a very special pair of ear to hear a double the price difference


That's why I highlighted decent and execelent....


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## BuickGN (May 29, 2009)

I would pick the one with the most power regardless of what front stage you're using.


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## thebigjimsho (Jan 11, 2009)

trojan fan said:


> easy....You are going to get the OP confused


Once upon a time I took electronics at a tech school. So most of that I got. Even as familiar as I was with old school audio and passive systems, it's a whole new animal with these active setups and using my factory h/u and class D amps...


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## WLDock (Sep 27, 2005)

There is no question that the HD is the better amp. But only you can decide if the XD is good enough for you. That is about as real of a response that you could hope to get. 

Sent from my HTC Sensation 4G using Tapatalk


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## metanium (Feb 2, 2007)

I'm currently running a XD700/5 from a factory HU. I had run HD previously. I also just recently removed a MS-8 from the signal chain which was used with both setups (XD & HD). As far as perceived SQ goes, I don't believe I detected any difference between XD & HD. The only real difference is the output power. Once I decided to remove the MS-8, the XD made sense because of the X10 switch that allows me to run fully active with tweeters. Now I'm experimenting with wide-banders in place of the tweeters. So my HP crossover has moved from the 2.5kHz range to the 250Hz range. If I settle with this setup, I may replace the XD700/5 with a HD900/5 to gain additional subwoofer output.


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## waldojeffershead (Jun 6, 2010)

The JL XD amps sound wet and almost tube like.


The A/B 4 channel in the HD900/1 sounds awesome, but the D-class sub channel sounds like over-rated garbage @ 2ohms.


The XD has 60% of the detail of the HD series on the highs, but makes up for the detail in clean and clear SPL.

My sister has an XD500/3 on a 10w3 and a pair of components and its loud and clear.


I would not recommend the JL HD series amplifiers, especially not for subwoofer duty. They don't even have adjustable subsonic filters.


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## lucky (Sep 25, 2009)

waldojeffershead said:


> The JL XD amps sound wet and almost tube like.
> 
> 
> The A/B 4 channel in the HD900/1 sounds awesome, but the D-class sub channel sounds like over-rated garbage @ 2ohms.
> ...


Are you saying the HD900/5 is A/B + D? I think you are very mistaken on that.

IMO, the two biggest factors that would swing my opinion in favor of the HD's over the XD's is the power output plus the regulated power supplies. 

I have this issue with my car where the volume and tonality changes with what seems to be rising and dropping of my car's operating voltage. Yes, that likely means I have car related issues I need to deal with, but I don't need my car stereo telling me that.

Amplifier power should be strong, consistent, and rock solid. If the regulated power supplies give that, then I'd be in. 

That XD700/5 looks mighty tasty for going active though.


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## adrenalinejunkie (Oct 17, 2010)

I have thought of this aswell since i just need an amp to do a 2 way active setup on my 6.5 clarus. i'm stuck between the hd600/4 and xd400/4.


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## Thumper26 (Sep 23, 2005)

Buy as much power as you can afford. Plus having 6 channels gives you more flexibility if you ever go 3way active.


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## kkant (Feb 3, 2008)

waldojeffershead said:


> The A/B 4 channel in the HD900/1 sounds awesome, but the D-class sub channel sounds like over-rated garbage @ 2ohms.


If I told you the 4 channel part of that amp is also class D, would it still sound awesome to you? If not, what does that say about our ability to hear awesomeness?



waldojeffershead said:


> The XD has 60% of the detail of the HD series on the highs, but makes up for the detail in clean and clear SPL.


Closer to 72.332%, but that's just an approximation.


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## kkant (Feb 3, 2008)

lucky said:


> I have this issue with my car where the volume and tonality changes with what seems to be rising and dropping of my car's operating voltage.


This is probably not an amp problem. Even in an unregulated amp, the thing that varies is the rail voltage, not the gain. So lack of regulation is not what is causing volume changes. More likely you are hearing a noise problem like alt whine.


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## ErinH (Feb 14, 2007)

waldojeffershead said:


> The JL XD amps sound wet and almost tube like.
> 
> 
> The A/B 4 channel in the HD900/1 sounds awesome, but the D-class sub channel sounds like over-rated garbage @ 2ohms.
> ...



wtf does "wet" sound like? 

The JL amps are all class D. your answer, therefore, is useless.

I run all HD amps. No one has ever told me my low end sucks. In contrast, I've been told by numerous people that my car has the best low end response they've heard. I'm not bragging... just saying. It has MUCH, MUUUUUCH more to do with install of the equipment you use and the final tune. 




Guys, the bottom line is that, in a car, FR is the beast. Quit worrying about silly amplifier differences and learn how to listen and tune.


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## WLDock (Sep 27, 2005)

waldojeffershead said:


> The A/B 4 channel in the HD900/1 sounds awesome, but the D-class sub channel sounds like over-rated garbage @ 2ohms.





kkant said:


> If I told you the 4 channel part of that amp is also class D, would it still sound awesome to you? If not, what does that say about our ability to hear awesomeness?


Interesting observation and comment. As stated, the HD amps use the same switching amplifier technology called Single Cycle Control™ on *ALL* of the output stages...FRONT, REAR, SUB. That is why they are SO small. Here's a blurb that explains their patented Single Cycle Control™ technology http://mobile.jlaudio.com/products_amps_pages.php?page_id=251 Also, the owners manual is a good read and advised: http://mobile.jlaudio.com/pdfs/16816.pdf The HD amps also have good specs in terms of THD and Damping Factor:

*THD at Rated Power: 
<0.03% @ 4Ω (front and rear ch.)
<0.05% @ 4Ω (subwoofer ch.) 

S/N Ratio (Front & Rear Channels):
>108.5 dB below rated power (A-weighted, 20 Hz - 20 kHz noise bandwidth) 
S/N Ratio (Subwoofer Channel):
>95 dB below rated power (A-weighted, 20 Hz - 20 kHz noise bandwidth) 

Damping Factor (Front and Rear Channels):
>400 @ 4Ω per ch. / 50 Hz
>200 @ 2Ω per ch. / 50 Hz 
Damping Factor (Subwoofer Channel):
>800 @ 4Ω / 50 Hz
>400 @ 2Ω / 50 Hz * 

Those are good numbers....better than some class A/B/ amps. Not sure what would cause the Mono sub channel to sound so bad at 2 Ohms? Unless maybe the sub is dropping below 1.5 Ohms at certain freqs and creating excessive distortion?


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## Frank Drebin (May 30, 2011)

If a guy needed 7 channels of amplification for a MS8 installation, what do you think the better option would be:

2 HD600/4's with one unused channel (or bridged for center)

OR

2 XD600/6's 

With 10 channels bridged, and the remaining 2 channels for rear fill.


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## lucky (Sep 25, 2009)

kkant said:


> This is probably not an amp problem. Even in an unregulated amp, the thing that varies is the rail voltage, not the gain. So lack of regulation is not what is causing volume changes. More likely you are hearing a noise problem like alt whine.


Ok answer man. I suppose you're right if volume and tonality equals inaudible phantom alternator whine.

Who said anything about gain? No, I don't believe fluctuating voltage is causing my gain knob to turn up and down.

Do you think it's a myth that an amp will put out less watts at a lower voltage than it will at a higher voltage? Say for example 12v vs 14v?


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## kkant (Feb 3, 2008)

lucky said:


> Ok answer man. I suppose you're right if volume and tonality equals inaudible phantom alternator whine.
> 
> Who said anything about gain? No, I don't believe fluctuating voltage is causing my gain knob to turn up and down.
> 
> Do you think it's a myth that an amp will put out less watts at a lower voltage than it will at a higher voltage? Say for example 12v vs 14v?


No, I don't think that's a myth. And as I said before, the reason they put out more power is because of higher rail voltage at higher car voltage. What that means is, if you are listening to your music at medium volume, there will be no difference in volume (or tonality) when flipping between 12V and 14V from the car. At very high volumes with loud music you will clip a little earlier when you are at 12V, but that doesn't change the volume. So, getting an amp with a more regulated PS probably isn't going to fix whatever problem you are hearing.

And getting back to the OP, it's not really a good reason to choose between XD or HD, any more than choosing between amps of different power levels. If you are listening loud enough that you are hitting clipping at 12v, then you need a bigger amp whether it is "unregulated" or regulated.


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## lucky (Sep 25, 2009)

kkant said:


> No, I don't think that's a myth. And as I said before, the reason they put out more power is because of higher rail voltage at higher car voltage. What that means is, if you are listening to your music at medium volume, there will be no difference in volume (or tonality) when flipping between 12V and 14V from the car. At very high volumes with loud music you will clip a little earlier when you are at 12V, but that doesn't change the volume. So, getting an amp with a more regulated PS probably isn't going to fix whatever problem you are hearing.
> 
> And getting back to the OP, it's not really a good reason to choose between XD or HD, any more than choosing between amps of different power levels. If you are listening loud enough that you are hitting clipping at 12v, then you need a bigger amp whether it is "unregulated" or regulated.


The sum total of all of this and it's applicability to anything that has been written prior to is *0*.


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## NucFusion (Nov 28, 2010)

I am currently running the xd 500/3 and it sounds fine. I have heard many hd set ups and they have all sounded great. As for deciding between the amps, I would say it just comes down to the power you are needing and budget. I doubt you could hear much difference in sq with the same speaker set up driving down the road. Maybe only a difference in volume.


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## rcurley55 (Jul 6, 2005)

Frank Drebin said:


> If a guy needed 7 channels of amplification for a MS8 installation, what do you think the better option would be:
> 
> 2 HD600/4's with one unused channel (or bridged for center)
> 
> ...


I'd do a 900/5 and 600/4:
150 x 4 for semi-active on the fronts from your 600/4
150 x 1 for the center from the 900/5
100 x 2 for the rears from the 900/5
500 x 1 for the subs from the 900/5

I think that's the most logical MS-8 system from JL assuming you are ok with 500 x 1 for subs.


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## sjg5359 (Mar 29, 2011)

Mioght have to consider XD's as well, currrently running slashes but thinking of HD but i'll give XD's a look.


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## waldojeffershead (Jun 6, 2010)

bikinpunk said:


> wtf does "wet" sound like?
> 
> The JL amps are all class D..


I described "wet" as tube like, lacking intricate and detailed SQ architecture. I didn't want to use the word muddy as I think the sound pretty nice.

Smooth, as if dripping liquid sound. Unlike my Zuki Eleets amplifier which has every musical detail presented accurately and clearly and all volumes. 

The 4 channel slash series amps are A/B, like the 300/4. 

I had an HD 900/5 on a w6 and c5 comps. Thought it was ear piercingly bright compared to my PPI A404 art series. The highs were definitely clearer than the Ample Audio AP series I used for a brief period after selling the HD series



lucky said:


> Are you saying the HD900/5 is A/B + D? I think you are very mistaken on that.


I'm pretty sure the sub amp is d on the HD and the 4-channel part is a/b, judging by the S/N ratio.



bikinpunk said:


> I run all HD amps. No one has ever told me my low end sucks. In contrast, I've been told by numerous people that my car has the best low end response they've heard. I'm not bragging... just saying. It has MUCH, MUUUUUCH more to do with install of the equipment you use and the final tune..


I switched from JL to Zed Audio and the difference was night and day for me.

I must admit I was shocked when I heard the XD series, the lows are completely different sounding from the HD series, more bloated sounding.

Didn't the HD series have all kind of recalls issues? And there is no excuse for the lack of an adjustable SSF.


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## WLDock (Sep 27, 2005)

waldojeffershead said:


> I'm pretty sure the sub amp is d on the HD and the 4-channel part is a/b, judging by the S/N ratio.


Where are you getting this from? The amps are all High-Fidelity Class D!

S/N Ratio:
HD1200/1 >111 dBA below rated power 
HD750/1 >110dBA below rated power 
HD600/4 >110 dB below rated power 
HD900/5 >108.5 dB below rated power (F & R), >95 dB below rated power (SUB)

Its obvious they had to make a slight compromise on the five channel. I understand that this amp is a bit complex in design. But all channels are CLASS D! Please read their technologies before making assumptions: http://mobile.jlaudio.com/products_amps_pages.php?page_id=251


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## kkant (Feb 3, 2008)

waldojeffershead said:


> I'm pretty sure the sub amp is d on the HD and the 4-channel part is a/b, judging by the S/N ratio.


You are definitely wrong about this. The whole amp is class D. Now...let me ask you again...does the fact that you now know this change your opinion of how the amp sounds?



waldojeffershead said:


> I switched from JL to Zed Audio and the difference was night and day for me.


Two words: amp challenge.

This does seem like Godwin's law of car audio.


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## lucky (Sep 25, 2009)

kkant said:


> This does seem like Godwin's law of car audio.


How do you figure? You Nazi. Haha...jk.


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## waldojeffershead (Jun 6, 2010)

kkant said:


> You are definitely wrong about this. The whole amp is class D. Now...let me ask you again...does the fact that you now know this change your opinion of how the amp sounds?


I have a window antenna that is effected by class-d amps.

For some reason I can't get any radio stations with a class d amp in the car.


I've been considering an ARC audio SE series for a while, but money is way too tight, I still might. I'd like to run all class A/B. And i'd need an external crossover or processor to use my 4 channel for bass duty.

But back to the XD amplifiers. I'm having some trouble find a component set that is "good enough" to serve along with the XD.

I'm torn between the Hertz Energy ESK 165 and the JL C3-650. I've heard the Hertz have a fragile crossover.


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## WLDock (Sep 27, 2005)

Well it's know that Class D amps tend to have higher EMI. Results may vary...


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## nerofive4 (Oct 4, 2011)

metanium said:


> I'm currently running a XD700/5 from a factory HU. I had run HD previously. I also just recently removed a MS-8 from the signal chain which was used with both setups (XD & HD). As far as perceived SQ goes, I don't believe I detected any difference between XD & HD. The only real difference is the output power. Once I decided to remove the MS-8, the XD made sense because of the X10 switch that allows me to run fully active with tweeters. Now I'm experimenting with wide-banders in place of the tweeters. So my HP crossover has moved from the 2.5kHz range to the 250Hz range. If I settle with this setup, I may replace the XD700/5 with a HD900/5 to gain additional subwoofer output.


Out of curiosity, why did you pull your MS-8?


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## nerofive4 (Oct 4, 2011)

sjg5359 said:


> Mioght have to consider XD's as well, currrently running slashes but thinking of HD but i'll give XD's a look.


I have a new xd700/5 if you are looking, I went with the HD for the output to the sub, since my arrangement did not have room for an additional amp (I have them hidden behind a quarterpanel.)


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## TestTones (Aug 29, 2011)

WLDock said:


> Well it's know that Class D amps tend to have higher EMI. Results may vary...


The IC industry trend dealt with this many years ago through suppression techniques and better power transformers. It's why any decent amp uses a toroid. I'm admittedly partial to class D though. They have a clean, bold blunt sound to me. 

I still can't contribute much to this thread. I would just go by the reputation of output performance of same or like wattage and lifespan. You could go through all I said earlier by pulling the amps open, getting the chip manufacturer ID's, review what type of polar and passive caps, location of components on your PC etc but both companies are surely using top of the line and extensive designs.


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## Neil_J (Mar 2, 2011)

TestTones said:


> The IC industry trend dealt with this many years ago through suppression techniques and better power transformers. It's why any decent amp uses a toroid. I'm admittedly partial to class D though. They have a clean, bold blunt sound to me.
> 
> I still can't contribute much to this thread. I would just go by the reputation of output performance of same or like wattage and lifespan. You could go through all I said earlier by pulling the amps open, getting the chip manufacturer ID's, review what type of polar and passive caps, location of components on your PC etc but both companies are surely using top of the line and extensive designs.


The funny thing is, very little EMI mitigation techniques are taught to EE's at college. It's somewhat of a black art. Not just in component selection either.. A huge portion of it has to do with pcb layout. Try to build the product to a price and rush it through the testing phase never helps, but always happens. 

I got my HD900/5 hooked up this weekend and I'm already having EMI problems. My XD700/5 never had them. The 900/5 might go up for sale very soon.


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## TestTones (Aug 29, 2011)

I think this is unfortunately typical of most technological fields. It's the rubber stamp dipped in ink taken to print format of education you find in everything from electronics to law school. Most of your amplifier designs are handed straight to the commerce brands from the imperialists in the global manufacturing industry. This is why I tell people open the equipment up and see for yourself if you have some knowledge in what you are looking at. Their engineer may tweak it, add to it etc but to be cost effective, they want to retain as much of the core design distributed by the chip manufacturer as possible when it comes time to order fully assembled PC's. 
The more standardized the design, the cheaper the gross product will be. 

Some tinkerer then mods or adds to it, licenses the addition and it becomes an industry standard. That tinkerer can be anyone from the engineer at Toshiba to the 65 year old grand father in his home work shop fixing his grandson's stereo. 

So yank the thing open and have a look. Is your toroid and other power stage components far away from your preamp components. Is there any shielding. What kind of passive caps and resistors do you see. What's the ID number on the chips. It's a completely different type of data set, and to most DIY'ers foriegn, to take into consideration.


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## Neil_J (Mar 2, 2011)

TestTones said:


> I think this is unfortunately typical of most technological fields. It's the rubber stamp dipped in ink taken to print format of education you find in everything from electronics to law school. Most of your amplifier designs are handed straight to the commerce brands from the imperialists in the global manufacturing industry. This is why I tell people open the equipment up and see for yourself if you have some knowledge in what you are looking at. Their engineer may tweak it, add to it etc but to be cost effective, they want to retain as much of the core design distributed by the chip manufacturer as possible when it comes time to order fully assembled PC's.
> The more standardized the design, the cheaper the gross product will be.
> 
> Some tinkerer then mods or adds to it, licenses the addition and it becomes an industry standard. That tinkerer can be anyone from the engineer at Toshiba to the 65 year old grand father in his home work shop fixing his grandson's stereo.
> ...


Lol.. Everything you say is true, BUT... There is such a thing as an amplifier with all of the qualities you mentioned that still sounds like ****. I know, because I have designed and built several. PCB layout really matters, a lot. I firmly believe that it is an art since no two engineers would end up with the same layout in the end.. Yet you could easily measure which one had the lowest RF and conducted emissions. The guys that do this stuff are artists in the truest sense, and it's impossible for you or me to quantify how good or bad it sounds just by opening it up and looking at it.

How do I know this? Because I would be out of a job if it were true! I test electronic devices in EMI chambers (and other fun stuff like zap them with lightning), and if you could just look at the device and know what it's emissions were, why, test tones, would they spend millions to measure it with test equipment? 

The real question is here, how much RF and conducted emissions testing did JL do? I'd like to see the test data, but that's unlikely to happen. My bet is, their test units did "good enough" but there may be some manufacturing tolerances or variations that make it worse. Some units may be better than others. I could sit and measure the unit until i was blue in the face, but instead I'm going to sell it and buy something else


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## metanium (Feb 2, 2007)

nerofive4 said:


> Out of curiosity, why did you pull your MS-8?


It seemed to over-complicate the whole setup. I know that may sound like a weak reason. My systems sounds more dynamic w/o the MS-8. The XD can accept speaker level directly from the HU and has all the crossover capabilities to do a full active 3-way. I did lose the center channel and T/A. But to somewhat make-up for that. I ditched tweeters and went with full-range 3" Founteks in their place. This allows me to move my crossover between dash and door from +/- 2.5kHz to 250Hz. There now no beaming from my midbass and the dash and door blen a whole heck-of-a-lot better. End result is me much happier. I eneded up selling the MS-8 which also helped add to my perceived happiness. Win-win!


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## TestTones (Aug 29, 2011)

Neil_J said:


> Lol.. Everything you say is true, BUT... There is such a thing as an amplifier with all of the qualities you mentioned that still sounds like ****. I know, because I have designed and built several. PCB layout really matters, a lot. I firmly believe that it is an art since no two engineers would end up with the same layout in the end.. Yet you could easily measure which one had the lowest RF and conducted emissions. The guys that do this stuff are artists in the truest sense, and it's impossible for you or me to quantify how good or bad it sounds just by opening it up and looking at it.
> 
> How do I know this? Because I would be out of a job if it were true! I test electronic devices in EMI chambers (and other fun stuff like zap them with lightning), and if you could just look at the device and know what it's emissions were, why, test tones, would they spend millions to measure it with test equipment?
> 
> The real question is here, how much RF and conducted emissions testing did JL do? I'd like to see the test data, but that's unlikely to happen. My bet is, their test units did "good enough" but there may be some manufacturing tolerances or variations that make it worse. Some units may be better than others. I could sit and measure the unit until i was blue in the face, but instead I'm going to sell it and buy something else


Not impossible at all!
You have to take into account I have the ears of a musician that designs equipment for the most difficult of playing styles. The better you can hear your signal, the better your skill gets. You're amplifying the signal in it's rawest form as it comes straight from the pickups and you're dealing with a single instrument. Your ears get far better trained than anyone dealing with general music reproduction amplifiers. While I'm not famous, I rate myself in the top 5 players I have ever heard and do so without arrogance. One crucial difference behind my methodology is using less parts, solid state instead of tubes and it has worked very well. I do not need a noise gate or ground isolator to have a completely noise free tone. I hear/see even $5,000 rigs that are plagued with ground buzzing without a gate. The same claim is made all the time about telling the difference between tube, chip and digital then everyone fails. The reason they fail in the blind sounds tests is because 90% of the units are designed to have the same sound. Hard clipped, edgy with a lot of bass, the midrange EQ actually set to a midbass band and the treble set low in the band of highs which is used sparingly. 90% of tube amps are designed so the distortion sounds like a chip. The truest sound of tube distortion is very fizzy and frothy. When you hear it, which is rare, it has a sound that is undeniably distinct from chips and digital processing. There's also thousands of chip and digital designs claiming to emulate, simulate etc real tube distortion but it's all nonsense. I know of ONE specific way to get that exact sound as tubes, none of them use it and from what I have seen know about it and I will never tell!

Point being, we're pretty well adapted to identifying the distinct sound of ceramic, polypropylene and polyester. There are very distinct differences between the sounds and the way they perform. If I open up any amp and see it loaded with ceramic caps, I know how it is going to sound and I know they were used to save money. I can get 100-200 ceramic disc caps for the cost of 10 polypropylene. Same cost any commerce brands purchase them at. Polyester is one step up and has a fuller texture without the shreddy, flexing wave form that produces natural distortion heard in the highs of ceramics. Polypropylene gives the fullest sound. Electrolytic used for filtering is just a crap shoot in terms of end sound but generally have the oozy texture and again, they are cheap. 

You can not stop a ceramic disc cap from distorting and bending the waveform. A couple in the circuit can sound good but used in every position it creates a very distinct sound. I had 2 amps loaded with ceramics that I replaced. The distinct difference between set ups would just be equated to quality by 99% of people rather than be associated with the use of the ceramic caps. I however knew exactly what I was hearing and knew it's what was greatly responsible to the way the speakers sounded. 

Ultimate point is, I know majority of people into car audio won't like the sound of an amp loaded with ceramic caps. 

To say millions to test equipment is absurd. The actual break down based on the cost of this equipment, life span and that cost applied to each model they produce which breaks down because it factors into each unit sold means a few cents of cost per unit. It's also not in the millions to build a sound isolation chamber and a tesla coil along with diagnostic equipment for other tests and pretty ridiculous to claim this is a standard practice in the audio industry. Maybe at Sony or some of the tube amp companies of Europe that sell hi-fi monoblocks that go for up to a million dollars per unit but car audio amps that get banged around for a couple years then replaced?
Absolute nonsense. 90% of them are thrown through some basic tests and sent to market. We're not dealing with the demands of the military here where gadgets need to withstand exposure to radiation EMF or EMP from explosions, radar, smoke and other airborne debris etc. 

In terms of layout. 
It's a standard in the industry to teach specific layouts. Your power stage is kept far away from your preamp stage and amplifier chips. Any amp you find that is not designed this way is surely coming from some oddball brand designed by someone who is unlikely to hold a degree or obtained it in a Chinese or Indian factory's basement hosted trade school.


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## Neil_J (Mar 2, 2011)

TestTones said:


> Not impossible at all!
> You have to take into account I have the ears of a musician that designs equipment for the most difficult of playing styles. The better you can hear your signal, the better your skill gets. You're amplifying the signal in it's rawest form as it comes straight from the pickups and you're dealing with a single instrument. Your ears get far better trained than anyone dealing with general music reproduction amplifiers. While I'm not famous, I rate myself in the top 5 players I have ever heard and do so without arrogance. One crucial difference behind my methodology is using less parts, solid state instead of tubes and it has worked very well. I do not need a noise gate or ground isolator to have a completely noise free tone. I hear/see even $5,000 rigs that are plagued with ground buzzing without a gate. The same claim is made all the time about telling the difference between tube, chip and digital then everyone fails. The reason they fail in the blind sounds tests is because 90% of the units are designed to have the same sound. Hard clipped, edgy with a lot of bass, the midrange EQ actually set to a midbass band and the treble set low in the band of highs which is used sparingly. 90% of tube amps are designed so the distortion sounds like a chip. The truest sound of tube distortion is very fizzy and frothy. When you hear it, which is rare, it has a sound that is undeniably distinct from chips and digital processing. There's also thousands of chip and digital designs claiming to emulate, simulate etc real tube distortion but it's all nonsense. I know of ONE specific way to get that exact sound as tubes, none of them use it and from what I have seen know about it and I will never tell!
> 
> Point being, we're pretty well adapted to identifying the distinct sound of ceramic, polypropylene and polyester. There are very distinct differences between the sounds and the way they perform. If I open up any amp and see it loaded with ceramic caps, I know how it is going to sound and I know they were used to save money. I can get 100-200 ceramic disc caps for the cost of 10 polypropylene. Same cost any commerce brands purchase them at. Polyester is one step up and has a fuller texture without the shreddy, flexing wave form that produces natural distortion heard in the highs of ceramics. Polypropylene gives the fullest sound. Electrolytic used for filtering is just a crap shoot in terms of end sound but generally have the oozy texture and again, they are cheap.
> ...


When you're building a tube amp or class A/B with a linear power supply, don't have to worry about radiated and conduction EMISSIONS, because you aren't generating anything that high in the frequency range. You do have to worrry about radiated and conducted SUSCEPTIBILITY which means proper shielding, etc. Yes component selection matters, I am not arguing this.

Now what about audio designs with high-frequency switching power supplies, and class D designs? They are by nature generating high frequencies that, if not mitigated properly, will be emitted via radio waves and/or conducted out of the cables. Through careful pcb layout and other mechanical tricks, it can be reduced to a negligable level. YES, you need test equipment to verify that this isn't happening. How much test equipment? That depends on what kind of specs you are trying to meet.

In terms of layout. I'm not talking about simply placing components on certain parts of the board. I'm talking about routing the critical switching components (the switching FET(s), capacitor(s), coil(s), and/or diode(s) in very specific manners, as these are high current loops that run at very high frequencies, that can create huge voltage spikes, that if the rise time is fast enough, can create nasty EMI. I'm also talking about copper thickness, layer count, has the ground plane been split by a signal layer? Is there even a ground plane? This stuff is not as much down to a science as you think. When you design this stuff down to a cost, (e.g. No 8-plus layer boards), it becomes a trade-off, and takes a bit if creativity to pull off. 

I work in the aviation electronics industry and we spend millions to do this sort of testing. You have us to thank if you've never been in a mid-air collision. If a board doesn't pass, we re-design it and re-test until it does. Everything I said before is still valid. A class-D amp is simply too sophisticated to just, as you say, open it up and judge it simply by the component selection. That was and still is somewhat acceptable for tube amps and class A/B amps, though.


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## TestTones (Aug 29, 2011)

Neil_J said:


> When you're building a tube amp or class A/B with a linear power supply, don't have to worry about radiated and conduction EMISSIONS, because you aren't generating anything that high in the frequency range. You do have to worrry about radiated and conducted SUSCEPTIBILITY which means proper shielding, etc. Yes component selection matters, I am not arguing this.
> 
> Now what about audio designs with high-frequency switching power supplies, and class D designs? They are by nature generating high frequencies that, if not mitigated properly, will be emitted via radio waves and/or conducted out of the cables. Through careful pcb layout and other mechanical tricks, it can be reduced to a negligable level. YES, you need test equipment to verify that this isn't happening. How much test equipment? That depends on what kind of specs you are trying to meet.
> 
> ...


You're really trying to make some factors sound far more sophisticated than they are such as shunting unwanted frequencies to ground from an ideal segment of the circuit. Granted the more gain, the more effective your bleed filter will need to be but it's nothing new nor so challenging as you know most reading your post in ignorance will be tricked into believing. You're talking about test equipment you can build from stock on hand up to the range of buying for millions of dollars. 

Obviously in your industry, I want to know you are using the most effective test and diagnostic equipment available to mankind. 

So I stand by what I said because it's a simpler way of saying what you have said only I am factoring the sound to specific components. If I see a circuit loaded with 40 ceramic disc capacitors, I know what kind of sound texture I am going to get within the broader image of the sound. If I see Wackasucki amplifier chips rather than something like Toshiba, I know I will need to be cautious with how well it's going to work even if the boys at Wackasucki ran their design through the most brutal tests and sophisticated diagnostic systems in the audio industry. If it rated a 4 out of 10 on their scale, they are still going to sell it.

If I see the preamp stage cluttered around the power amp stage and amplifier chips, that does serve as an indicator *if* there is a noise issue. For example if I pickup noise from cranking up crossover gain, it gives me a good starting point. Either the crossover design is poor or has used poor components or, it is simply picking up noise from the power stage. 

So what you are saying is of course accurate and convincing but it is not definitive and it by no means discredits the factors I am pointing out. If it is indeed EMF, it can be generating from anywhere in the circuit regardless of where it is most likely sourced from yet you specified a source yourself that is recognized by *looking.* Obviously if you have noise that you suspect is due to the power stage or amplifier switching stage, hooking it up to a diagnostic system and getting frequency and EMF readings with a system's probe is far better than trouble shooting based on looking at the design and using common sense as an engineer or general technician with less sophisticated test equipment.

But it's certainly not useless or irrelevant.


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## nerofive4 (Oct 4, 2011)

Test tones, could you give a synopisis on what you beleive to be the major differences between the hd and the xd amplifiers (if asked to be specific then the hd900/5 vs the xd700/5) Simplify when possible.


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## BuickGN (May 29, 2009)

I'm curious as well. It might be over my head but I'm thoroughly enjoying this conversation.

I'm almost starting to think that different amps can sound different even if they measure the same which is something I've never believed.


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## Babs (Jul 6, 2007)

100 watt Krell Monoblock vs 100 watt Sony ... I had too much exposure to home audio to ever think all amps are the same, just speaker wire with gain. 

For maybe that 99% of it "just amplifying signal and driving speakers", sure.. But that 1% that separates the 70lb Class A monoblocks with roughly the same output rating from a 2lb JVC receiver at Sears.. It's a big 1%. I always get tickled when I read the statements that an amp is just an amp is just an amp.

But also, amps of equal component quality will still exhibit different voicing and characteristics, sure. The goal of the perfect amp of course is "straight wire with gain", only increasing the amplitude of the input signal to absolute perfect 100% accuracy. Not yet achieved.. By ANY but the closer you get, the higher it costs exponentially.

.. All my unedumacated opinion just from a music lover rather than a EE, for what it's worth (about one soda).


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## Neil_J (Mar 2, 2011)

To clarify my previous posts, all of my negative EMI concerns with JL HD amps aren't directly audible by the amplifier itself. It is audible, however, through my FM tuner, which has reduced reception, and through the crappy RCA cables used in the first phase of my installation. I'm not talking about sonic differences heard from the outputs... _I'm talking about nasty signals emitted from the amp that are interfering with other systems in my car_. This is obvious to folks who have read the other JL HD vs xxxx threads that have came up lately, but maybe not so much for everyone else.


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## Neil_J (Mar 2, 2011)

nerofive4 said:


> Test tones, could you give a synopisis on what you beleive to be the major differences between the hd and the xd amplifiers (if asked to be specific then the hd900/5 vs the xd700/5) Simplify when possible.


I have both installed in my car right now, and I'm leaning towards the XD. However, I still have many weeks of testing ahead of me, and this may change down the road. 

So far, I like the XD's because:

I like the set-screws in the XD. The HD series use little connectors that face down, which must be unplugged to work on. The XD's set-screws can be accessed without much effort, and accepts a wider range of cable types due to a flat piece of metal attached to the set-screw, giving a flat clamping area rather than a single point.
The XD is smaller than the HD -- Have you seen the MINI Cooper hatch area? Enough said 
The HD scratches easier than the XD. I could lose points for this kind of stuff at sanctioned SQ events.. sad but true. The XD black powder-coat is pretty damn durable.
I've not noticed any sonic differences... yet. I may find some as the weeks progress. So far, the XD has been "good enough" but this may change as I get my system tuned in.


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## Babs (Jul 6, 2007)

Considering the price differences, if the XD's are that close to the XD's in clean detailed accurate power delivery, given of course the output rating differences, I'd say the XD line is actually more value per dollar.

Sent from my DROIDX using Tapatalk


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## Neil_J (Mar 2, 2011)

I just purchased a second XD700.5 from Al and Ed's for $430 price-matched. So now I own:


JL XD700/5 #1
JL XD500/3
JL HD900/5
JL XD700/5 #2
I'm currently thinking about going with this configuration:

XD700/5 #1: ch1-4 bridged to L6SE midbasses, channel 5 to SWR-843D sub #1
XD700/5 #2: ch1-2 to L1 Pro R2's, ch3-4 to L3SE (use the internal 12dB/oct xover at ~3.5-5khz), channel 5 to SWR-843D sub #2
XD500/3: Center channel, probably just a L3SE. Channel 3 to SWR-843D sub #3
XD300/1: SWR-843D sub #4
JBL MS-8 mounted under passenger seat, powering TB 3" speakers for rear-fill
Put the 900/5 up on the classifieds to pay for the damage above :laugh:
..Then probably rip it out after six months because of some nitpick I find down the road.. deep sigh.


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## BuickGN (May 29, 2009)

It seems like you could reduce the number of amps if you went HD and did not have to bridge everything. That was part of the reason I went HD, I wanted only two amps, one under each seat for my active 3-way+center+subs. The XD amps just didn't have enough power unbridged at least for my midbass.


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## Neil_J (Mar 2, 2011)

BuickGN said:


> It seems like you could reduce the number of amps if you went HD and did not have to bridge everything. That was part of the reason I went HD, I wanted only two amps, one under each seat for my active 3-way+center+subs. The XD amps just didn't have enough power unbridged at least for my midbass.


I dont know if that's exactly true. I would have to bridge my midbasses either way to get the desired power levels (I wanted >=150W): 150W x 2 bridged with the 900/5, and 200W x 2 with the 700/5 (admittedly with higher distortion). The midbasses are the only thing I'm bridging. The amp with the center channel may just have the other channel unconnected (or maybe another HAT tweeter down the road). 

I can live with being called crazy for running 4 amps and 4 subs :rolleyes2: I think the custom box and amp rack will look pretty rad when it's all said and done. Lots of carbon fiber, chrome, and exposed techflexed wiring. Which reminds me, I need to get started on my build log!


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## BuickGN (May 29, 2009)

Neil_J said:


> I dont know if that's exactly true. I would have to bridge my midbasses either way to get the desired power levels (I wanted >=150W): 150W x 2 bridged with the 900/5, and 200W x 2 with the 700/5 (admittedly with higher distortion). The midbasses are the only thing I'm bridging. The amp with the center channel may just have the other channel unconnected (or maybe another HAT tweeter down the road).
> 
> I can live with being called crazy for running 4 amps and 4 subs :rolleyes2: I think the custom box and amp rack will look pretty rad when it's all said and done. Lots of carbon fiber, chrome, and exposed techflexed wiring. Which reminds me, I need to get started on my build log!


Looking forward to the build log. I was thinking a 900/5 and 600/4 but I'm the guy that took 1.5 years to decide on which amps to use lol.


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## thebigjimsho (Jan 11, 2009)

Go away for a couple weeks and see what happens. lulz.


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