# JL HD600/4 ... My Thoughts



## yuri

I have been reading reviews and posts on the jh hd amps since they came out but i never actually got to listen to one until a few weeks back when i picked up a 600/4 & 750/1 in a deal with another car audio freak  

After reading all the rave reviews i must say i was looking forward to listening to them ......

So far i have focused my time on the the 600/4 ,apart from hooking the 750/1 up just to test it was working OK i haven't spent any real time listen and comparing it to other amps yet ..... ..

I wont bore you all with the usual stuff about how tiny it is and how powerful and efficient it is ,what features it has ,bla bla bla ..... 


This is only based on how it *sounds* in my opinion and nothing else ..

On jl audio website it says quote 
*"We invite you to sonically compare the HD amplifiers to any amplifier, at any price... We think you will quickly discover that all the old amplifier compromises have suddenly vanished."* 

Well that's just what i did ! .. 

I have a number of amps i want to compare it to .
Tru 7.4t copper sweetest amp on midrange and treble i have ever listened to.
Mcintosh mc4000m (the daddy mac).
Genesis class A's , sa30 ,sa50 & da110.
Kenwood kac1023 , my favorite sub bass amp .

I started out with the amps i have hooked up on my bench at the moment .
Sony xm-2000r ,Sony's huge flagship amp 
Denon dca800 , 6x50w amp from the early 90's

JL 










Sony










Denon










I have used the same brand RCA phono leads between amp's ,headunit and switching box except when i had to use extra RCA Y leads i on the Denon to bridge it to 2 channel ..
I also use the same speaker cable between amps and 2 matching pairs of speakers , Mordon Short ms10i (pearl edition). i regularly swapped round speakers to help eliminate any different sound characteristics between them 

MS 10 i's





















A simple switching box was used switch between amp's from the headunit. again regularly swapping outputs to help eliminate any difference on them. 

switch box .









Everything was powered from the same source . and powered up all together to avoid one amp been colder than the other ..

A Vibe 50amp regulated power supply and 2 huge 12v batteries . 











when i first hooked up the 600/4 i spent a full evening comparing the front channels to the rear channels to see if i could differentiate anything between them . i set/matched the front and rear gains with a spl app on my phone ,swapped rca leads,speakers ,inputs.outputs more times than i can recall . and as far as my ears could tell they are identical. 



Each amp's cross overs have be turned off and set flat without any eq ,bass boost etc .. most listening was in simple 2 channel full range stereo .
ie 2 of the jl's 4 channels used, 2 of the denon's 6 channels used and the sony is a 2 channel . i often swapped round channels on the jl & denon. sometimes using the front and some times using the rears ..i also bridged the jl down to 2 channel and the denon to compare them , some time was spent running the jl & denon with a sub as well as the ms 10i's . 

i used a pair of cdt es06+ subs (see pic's ,below the ms10i's) and a Aliante 12 ltd .. this wasn't a fair comparison as i would need another pair of the 06+'s in matching enclosures and another 12ltd to square things up ....


12 LTD 













The head-unit i used is a *Rockford 8140* set flat and with out any other processing . 











I would of liked to compare the 3 amps together. i do have a third pair of MS10 speakers but they have slightly different tweeters fitted to them so that was out ,and having 2 sets of speakers abreast cause enough problems with differences width and path length distance ,imaging and staging ,stacking one set on the other set also changes things up a hole heap . i was forever swapping inner ,outer ,top ,bottom speakers around to the point i hardly knew what amp was driving what speaker set . 
3 set's would of been unworkable and a total nightmare to judge fairly ..

i must of spent at least a minimum of 30 hours sitting down seriously listening to these amp's over the last 4 weeks and around the same amount of time again spent working on a motorcycle i am rebuilding and making bio-diesel in my garage all the while with some of the amps playing ..

A run down on how i compared/listened to them . after i set / leveled all the amps gains as close as i could match them with the spl app it soon became apparent the best speaker placement (sweet spot from my stool)was the outer /wider set on the lower level .
so i would change around speakers so that the amp playing would have its speakers in the that placement most of the time . 

usually i would only listen to 2 amps in one day , ie the jl v the denon , the jl v the sony and some times the sony v the denon just to get a reference between them .. and it was also easier to manage the swapping over of cables ,speakers etc with 2 amps at a time ...

To warn up the amps i would connect the front outputs from the rockford to one amp and the rears outputs to the other and let them both play a few tracks together , after i would connect the switch box back to the front outputs of the rockford and both amps , set the volume depending on my mood and the music i was playing and play at least 3 or 4 tracks from a cd before switching amps on the box and swapping speaker leads over and play the same tracks again at the same volume on the head unit .. sometimes i would repeat this over and over a different volume levels while making notes .... you wouldn't believe how much i hate some of my Cd's now that i loved before :-( ... 

occasionally i would play a whole CD before switching over amps and playing it again at the same volume , this is much harder than you might imagine as you can so easily get carried away in the music and stop taking notes and even crank up the volume half way through a track or CD or even forget what amp you was last listening to ! 
more than once i fell asleep and i also got lots of practice on my air guitar and air drums  ........

Now to be brutally honest i believe i made up mind as to how each amp sounded to me within the first half hour or so of listening to them ... maybe even less time than that ....

i did persevere with the comparison ,swapping round every cable, speaker, sitting position ,rca, resetting gain levels higher and lower on the amps , i used other speakers kef's ,jpw's ,Anthony Gallo .regardless what i factor i changed my overall opinion was the same ?

i have had some friends listen with me ,one who described the sound of the JL HD 600/4 exactly the same as i thought within a few minutes of listening to it ? he actually came to the same conclusions as i had as well ! 

later i will give a list of the cd's and tracks i used and also the conclusions i came to ,my opinion of the amp ,its strengths ,its weaknesses ... 

i have one more "ace in the hole" "trick up my sleeve" so too speak .....


*To Be Continued..................................*




...


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## Coppertone

Wow...................


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## jpswanberg

waiting with baited breath ....


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## tintbox

I'm in for this one as well.


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## Lymen

Can't wait...


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## Lorin

im liking the process.


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## rytekproject

I didnt know car audio blue balls was possible until now


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## spag_bace

excellent setup!


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## evo9

Come on man! Don't leave us hanging like this.........








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## jcollin76

Anxious about this as well!
Do go on...


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## WLDock

Sounds like you have a fun test going on here. Very interested in how you like the amp compared to this group:



> Tru 7.4t copper sweetest amp on midrange and treble i have ever listened to.
> Mcintosh mc4000m (the daddy mac).
> Genesis class A's , sa30 ,sa50 & da110.
> Kenwood kac1023 , my favorite sub bass amp


This is what DIY is all about...gathering gear and listening!


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## IBcivic




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## Coppertone

^^ I just spit out my juice from laughing so hard.


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## Neil_J

Subb'd


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## yuri

guys , 

i am holding off posting my initial findings for a little while as i want to do some further comparisons with other MODERN class D amps .... 

i have very little experience with class d car audio amps ,other that some brief listening to some old infinity 275's (10 years ago) and more recently (2 years ago) jbl gto 755.6 and a 10 minute listen to a ucs pro amp & vibe sick ?? a few weeks ago. NONE them inspired me with "class d" technology ... 

finding people with modern class d's around where i live is proving hard but i did come across a young friend who owns a interesting little " D "amp , not exactly a car amp but it will run from voltage between 10volts and 30 volts and he intends to install it in his car pc setup with a 2x8 mini dsp .. for want of finding any other D's i asked him to bring it over for some fun ...

today he did so .. a very quick wire up and off we go ...






























shocking ,disbelief and unbelievable are words that come to mind ...

as i said it was a quick wire up ,i just used the wire i had to hand , 16awg for power something like 20awg for speaker cable ... 

tomorrow i will upgrade/beef up the power to 3 runs each neg and pos 10awg cable as it has 3 inputs for each .
i will also use the same speaker cable that's connected to the HD , 
maybe i might be able to work in a speaker selector switch box in reverse so i can use just one set of speakers ...have to see if that's possible...

links for the little amp if anyone is interested ..

4*100 watt @ 4ohm, TK2050 D-class Audio Amplifier Board | eBay


...........and there is more :surprised:


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## WLDock

...and the fun continues...


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## Brian Steele

yuri said:


> guys ,
> 
> i am holding off posting my initial findings for a little while as i want to do some further comparisons with other MODERN class D amps ....
> 
> i have very little experience with class d car audio amps ,other that some brief listening to some old infinity 275's (10 years ago) and more recently (2 years ago) jbl gto 755.6 and a 10 minute listen to a ucs pro amp & vibe sick ?? a few weeks ago. NONE them inspired me with "class d" technology ...
> 
> finding people with modern class d's around where i live is proving hard but i did come across a young friend who owns a interesting little " D "amp , not exactly a car amp but it will run from voltage between 10volts and 30 volts and he intends to install it in his car pc setup with a 2x8 mini dsp .. for want of finding any other D's i asked him to bring it over for some fun ...
> 
> today he did so .. a very quick wire up and off we go ...
> 
> 
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> 
> shocking ,disbelief and unbelievable are words that come to mind ...
> 
> as i said it was a quick wire up ,i just used the wire i had to hand , 16awg for power something like 20awg for speaker cable ...
> 
> tomorrow i will upgrade/beef up the power to 3 runs each neg and pos 10awg cable as it has 3 inputs for each .
> i will also use the same speaker cable that's connected to the HD ,
> maybe i might be able to work in a speaker selector switch box in reverse so i can use just one set of speakers ...have to see if that's possible...
> 
> links for the little amp if anyone is interested ..
> 
> 4*100 watt @ 4ohm, TK2050 D-class Audio Amplifier Board | eBay
> 
> 
> ...........and there is more :surprised:


Looks like the Sure Class D amp modules. You can source that particular one and others, along with matching power supplies, from Parts Express, e.g. see 4x100W @ 4 Ohm TK2050 Class-D Audio Amplifier Board 320-302. Note that the "100W" rating is likely at "<10%THD". I don't think they have a power supply suitable for car audio use however. I don't believe you will not get its full potential running it direct from a car's 12V supply. And then there's the remote turn-on requirement to consider...


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## yuri

I used the following CD’s in my listening sessions 
Focal demo disc’s 1,3,4,5&6
Alpine Reference Disc
Dynaudio feeling music CD 
These are my favorite “SQ Reference” CD’s , there is some fantastic tracks for evaluating purposes not only can they give your setup a good workout they have a huge range of musical styles and great music .

I played various tracks from these CD’s
Fleetwood Mac - The Dance
Sultans of Swing - Best of Dire Straits 
John Mellencamp 1978-2005 A Biography 
Steve Earle - The collection 
Michael Jackson - Thriller 
Shania Twain - Come On Over 
Wynonna Judd - Revelations 
Katherine Jenkins - Believe 
AC/DC -Back in Black & Let There Be Rock 
Def Leppard - Adrenalize & Hysteria
Michael Buble - Crazy Love
Guns n Roses - Appetite for destruction
John Holt - 1000 Volts 
Gregory Isaacs -Night Nurse
Dr Dre - The Chronic 2001
Bob Marley - Legend
Relax - 1980’s 2cd 
Beegees - greatest hits 

Maybe a few others i can’t recall right now ....
I know i said i would do some further testing but it’s got to the point today that i am just going round in circles , and more testing is just confirming what i already know !..............
*
I WANT TO MAKE A FEW POINTS FIRST...*

*1.* As i said earlier I bought these *JL HD AMPS* , well actually I done a deal with 2 of my amps and cash to the other guy .. When it’s all said and done I paid out a big lump of my hard earned money of these amps one way or the other...

*2.* i am a JL Audio fan , in so much as i rate there subs..and have a number of them over the years , I know for a fact I owned the very first 15w6 in theUK many years ago ...so have no hidden agenda or axe to grind with JL audio ..

*3.* my testing is far from ideal , not in any way scientific at all , and not in the intended environment that the amp was designed for “inside a automobile “ just me and my ears and my heart.

*4.* The amp played and functioned 100%, exhibited no signs of stress or showed any indication that it was in need of any repair at any time over the weeks of use ....

*5.* it’s just my opinions and thoughts, i am not out to upset anyone or start arguments so no flaming please guys...


Let’s get onto it , you have seen i have listened to the amp seated in a central position without any form of digital or analogue processing ,no eq ,no ta ,no cross over’s . Just a head-unit the amp and a pair of speaker ...I also have direct comparisons (amps) that with the flick of a switch I can compare to > 

If on the other hand if I was testing the amp in isolation in car without the luxury of other amps to make direct comparisons to ,off centre seating and maybe using processing ,ta ,eq , x-o ect ect . Would the outcome be different? You will have to decide that for yourselves! 


*THOUGHTS *

If music is food for the soul , feasting on the hd600/4 left me hungry ,tired and cold ....
Its ability it take a great recording and suck the life and emotion from it is disturbing.

Presents music like a young unemployed actor reading Macbeth for the first time at a screen test for the RSC, word for word correct but lacks the skill and experience .

Each and every detail and instrument can be followed note for note throughout the track but it stumblingly refuses to combine the instruments and vocals together to form “ music” ,rather like listening to individual parts that never gelled and felt out of time and disjointed .Harmony vocals are pulled apart and that’s just wrong ! 

Stereo sound stage is also _“different”_ ! it has a very strong and focused left, right & centre but poor integration across the stage and actually draws you attention to the directly to the speakers , 

Width was only as wide as the speakers while depth suffered from a awful trait this amp has of projecting the centre information several feet further way than the left or right .( in the Michael Jackson track where the footsteps walk across from right to left ,on the hd they walk in a arc away From you from right to left ).

Like your boss at the company Christmas party , it never lets go and gets down and dirty ..Always in total control at the expense of sounding compressed & restrictive , heck its anal !
The longer i listened to it the more fatigued i felt ,left me feeling flat and tired no matter what music was played ,it just never got into the groove and hit that spot ....

I could go on and on but i think you get the picture .. in all i am very disappointed in the amp 


............


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## ErinH

I respect what you feel/found but I disagree. I think the amps work just as they should. In fact, I'd almost question what the other amps you're listening to might be doing to the signal throughput but that's another day. 

I'm not going to burn you at the stake. I'll just disagree and leave this with saying that the top 2 scorers at MECA finals this year run only JL HD amps. And if competition isn't your thing, I encourage others who are following your post as gospel (trust me, it will be taken as such by many) to listen to a properly integrated system using Class D amps. The only issues I've found with common day Class D is that the SNR is a bit higher in earlier models (notably, alpine's 1st gen PDX line). Otherwise, given the benefits, and no side effects that I've been able to measure or hear for that matter, I'll still stand by Class D.
I've been running 2 hd600/4's and a single 750/1 for nearly 3 years now. Ask anyone who knows me and they'll tell you that it's either a testament to my belief in their ability to do what they need to... or I'm just lying about not having swaped them out. 


Thanks for taking the time to do the writeup in the manner you did. I wish more folks were as methodical as you are. You've put the OG's here to shame. 
I appreciate you've taken time to note that it's simply an objective opinion. The fact is, to truly A/B something, the steps required are much greater than many of us can achieve. Vance Dickason wrote on this specifically and Floyd Toole discusses it when discussing the importance of subjective testing; our hearing memory isn't what we think it is and psychoacoustics have been proven to take effect. At the end of the day, however, you have to purchase what you like and you've done a great job of exploring your options and coming to a conclusion on what you should run.
Great work.

- Erin



Yuri, I mentioned above about Floyd Toole's efforts regarding testing. Here's a GREAT article to read which really stresses how much psychoacoustics plays in to what you hear and how to really have a good test, it needs to be as "blind" as possible and the way to achieve this isn't as simple as putting on a blindfold. I should have posted this before, but I didn't see your thread until now. 
http://www.pocket-lint.com/news/34090/harman-kardon-want-standardised-sound

I encourage anyone else who wants to themselves and their own testing true justice to read the same. This isn't me harping. This is me trying to help the community learn that proper testing is the only way to test.


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## tintbox

bikinpunk said:


> I respect what you feel/found but I disagree. I think the amps work just as they should. In fact, I'd almost question what the other amps you're listening to might be doing to the signal throughput but that's another day.
> 
> I'm not going to burn you at the stake. I'll just disagree and leave this with saying that the top 2 scorers at MECA finals this year run only JL HD amps. And if competition isn't your thing, I encourage others who are following your post as gospel (trust me, it will be taken as such by many) to listen to a properly integrated system using Class D amps. The only issues I've found with common day Class D is that the SNR is a bit higher in earlier models (notably, alpine's 1st gen PDX line). Otherwise, given the benefits, and no side effects that I've been able to measure or hear for that matter, I'll still stand by Class D.
> I've been running 2 hd600/4's and a single 750/1 for nearly 3 years now. Ask anyone who knows me and they'll tell you that it's either a testament to my belief in their ability to do what they need to... or I'm just lying about not having swaped them out.
> 
> 
> Thanks for taking the time to do the writeup in the manner you did. I wish more folks were as methodical as you are. You've put the OG's here to shame.
> I appreciate you've taken time to note that it's simply an objective opinion. The fact is, to truly A/B something, the steps required are much greater than many of us can achieve. Vance Dickason wrote on this specifically and Floyd Toole discusses it when discussing the importance of subjective testing; our hearing memory isn't what we think it is and psychoacoustics have been proven to take effect. At the end of the day, however, you have to purchase what you like and you've done a great job of exploring your options and coming to a conclusion on what you should run.
> Great work.
> 
> - Erin


Thank you.


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## evo9

> Originally Posted by *Yuri*
> 
> Always in total control at the expense of sounding compressed & restrictive


I somewhat agree with Yuri on this. My time with the JL HD's reminded me of listening to my pc. And for the record, my pc audio side is HT Omega Calro halo XT, Simplifi Digital 7075 & Definitive Technology BP10







.


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## Coppertone

^^^ Please translate this into English since I have no clue if this is good or sucky lol.


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## evo9

Coppertone said:


> ^^^ Please translate this into English since I have no clue if this is good or sucky lol.


Well........................ the pc bits are there to inform that we are not talking about the mobo onboard sound. As for the HD amp, I am not saying it sounded bad. To me it sounded compressed! Look at it this way, I had the Arc Audio XXK series prior. It was a step backwards SQ wise replacing them with the HD's. The HD's are now replaced by the Tru's in my sig. This move is a step forward back up the SQ ladder. However, the 500 watts from the HD900 makes the 600 watts from the SB6 channel 5&6 bridge sounds/feels like 200watts.





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## ErinH

Again, read my link regarding psychoacoustics and non blind testing...


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## Coppertone

I see said the blind man, I found that with my 600/4 I had more of a completed sound system. Overall with that and my HD750/1, I was very happy with the output. Now I am far from an expert, but for my needs it was the perfect fit. Sorry for my rambling, carry on.


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## t3sn4f2

OP, props on your review and I'm sure many will benefit from it (rightfully so IMO, ie go for what make YOU happy), *BUT* the review is in no way unbiased or scientifically accurate. To be truly fair.


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## evo9

Coppertone said:


> I see said the blind man, I found that with my 600/4 I had more of a completed sound system. Overall with that and my HD750/1, I was very happy with the output. Now I am far from an expert, but for my needs it was the perfect fit. Sorry for my rambling, carry on.


It's an open forum! Your opinion counts. I would not bash the HD amps in any shape or form. I still have my HD600, but sold the HD900 after it came back from repair. Would I run them again? Short answer, yes!





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## Coppertone

I have my HD 750/1 still hooked up although my HD 600/4 went to its new owner. The only reason for the sale was the fact that I have a Zuki Eleet that I wanted to run. The HD will be pulled and stored in anticipation of going to a new owner.


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## evo9

Coppertone said:


> I have my HD 750/1 still hooked up although my HD 600/4 went to its new owner. The only reason for the sale was the fact that I have a Zuki Eleet that I wanted to run. The HD will be pulled and stored in anticipation of going to a new owner.


So what are your thoughts going from the JL's to the zuki?





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## Coppertone

The Zuki is still in its box as I just sold the 600/4 the other day. Next week the 750/1 will be pulled and the Zuki will be wired up. Review to follow folks.


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## adrenalinejunkie

Intresting read...


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## jimmyjames16

_*THOUGHTS *

*If music is food for the soul , feasting on the hd600/4 left me hungry ,tired and cold ....
Its ability it take a great recording and suck the life and emotion from it is disturbing.*

Presents music like a young unemployed actor reading Macbeth for the first time at a screen test for the RSC, word for word correct but lacks the skill and experience .

Each and every detail and instrument can be followed note for note throughout the track but it stumblingly refuses to combine the instruments and vocals together to form “ music” ,rather like listening to individual parts that never gelled and felt out of time and disjointed .Harmony vocals are pulled apart and that’s just wrong ! 

Stereo sound stage is also “different” ! it has a very strong and focused left, right & centre but poor integration across the stage and actually draws you attention to the directly to the speakers , 

Width was only as wide as the speakers while depth suffered from a awful trait this amp has of projecting the centre information several feet further way than the left or right .( in the Michael Jackson track where the footsteps walk across from right to left ,on the hd they walk in a arc away From you from right to left ).

.. * in all i am very disappointed in the amp 
*
_

I couldn't agree with you more about the HD's.. go right to ZUKI my friend..


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## yuri

i would like to add that i still have the hd on my bench and i am still comparing it to other amps ,, more to come on that later , 

something that i have recently found out is that a friend of mine tried to contribute to the tread .. he has been a member on here from 11-27-2009 but had never posted before so it would of been his first post ! 
i believe that his post would of had to been approved by a mod? .

i am not suggesting anything unto-ward as to why his post never appeared ,probably just got lost in the system but i would like to add his thoughts to the thread for clarity if i may ... 
his user name is " agithegreat " and below is the post he tried to post .. 


quote"

_You see the little head in about the 10th picture down?
That's me... []

Now, i'm not here to 'back Yuri up, believe me, I don't like everything he likes (his hearing is going downhill at his age you see...).

I don't care, or have 'a bias' to anything as it cost me nothing to sit there and listen to the amps. Yuri was very fair and wouldn't even hint at his opinion before I started listening...
I immediately could tell which amp was the DCA800 - An amp i'm familiar with.

Song after song after song, I could say yup, thats the denon.
Now to say that the JL is as good as an amp as the denon surely must mean they sound equal?
We balanced the volumes as best as we could using the RTA app on my phone, sat back listening with just a switch and the JL sounded like Yuri described above.
Imagine how I felt telling him I didn't like the sound of his new amp... :blush:

I'm not slating class D amp design here at all. I'm an active poster on DIYA and on there you will see how I stand behind IC amp design, having heard a few chip amps and repaired a few class D's too.
However, the JL left me disappointed. I was hoping when Yuri told me he had his hands on a class D that it would 'shift the tables' to show him how the class D amps have come along, which I actively support.

Unfortunately yuri, nor myself have access to 'perfect environments' or top class test equipment. However we both have ears and all the plots in the world cannot accurately represent how I hear, yet alone, how I interpret sound.

These are my findings and as has already been said others have found different results. I would be very interested to hear another member of the HD range to compare again. Or even if someone else local could setup a different 'rig' to compare the JL again.
If anyone has any other suggestions into how this could be made fairer on a practical level, without requiring excessive money inputs, or a degree in acoustical engineering, i'm sure yuri would be up for 'trying' it.

I have many a time gone over to see yuri and sat in his garage listening to various amps, headunits, speakers, subs. What I have always noticed is Yuri wont take anyone else's opinion before conducting his own.
I'm not striving for the ultimate competition car, nor even the best sounding one on music. I look at practical application on a realistic budget, which unfortunately I feel the JL amp in question does not fit." end quote_


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## Mless5

Thanks dudes, very interesting read!


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## KyleMDunn

Coppertone said:


> The Zuki is still in its box as I just sold the 600/4 the other day. Next week the 750/1 will be pulled and the Zuki will be wired up. Review to follow folks.


Any additional feedback or opinion?


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## yuri

i still have the hd600 on the bench , and this last few weeks i also have had a alpine pdx 2.150 on the bench . 

in some ways i prefer the alpine amp , its more musical to my ear and less fatiguing during longer listening periods , on the other side its less detailed and not as dynamic,focused and controlled as the HD .
but PDX has a wider stereo sound stage with a even depth and a more natural spread across the stage compared to the HD ... 


but before you guys jump on me as a "hd hater" i may have to eat a large slice of humble pie ! 

Enter one Clarion HD-X1 .... and a jaw dropping moment .............


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## subwoofery

Interesting post... You now got me curious about the PDx v.2 (F4 & F6)... 

Kelvin


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## ariko81

SO relevant to my world!...please continue your thoughts kind sir. I'm hanging..


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## fj60landcruiser

Nice write up!


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## Fishlips Soup

Although I'm new here, I felt the need to respond, given the testing methodology and the "reference" system used. I have very little experience A/B-ing car equipment, but rather 35 years+ of doing it with high-end home equipment and audiophile headphones/amps. Despite the differences bwtween mobile and in-home, there are some basic principles of the science of sound that hold true for any reproduction of music; beginning with the power source, through the digital media and processor, preamp and then amp, through the speakers, which are finally affected by the listening environment. In short, it's a long long chain with both digital and analogue links.

1) Your ears don't lie, and if you noticed that much of a difference, then using the same test criteria, you'd probably get similar results in a car ...but...and it's a very large, humongous butt (couldn't resist the extra t): your power supply is probably unregulated and contaminated with noise. You actually need battery power with sufficient amps to run everything 12V …and that which is not 12V needs a clean/regulated power supply (think PS Audio PS300 or similar). Your power converter (I didn't notice what you are using) is the first weak link that injects noise (and thus bias) into your results.

2) Your "front end" (the head unit) is far from reference-quality: it certainly has its own sound signature and may be a bad match/synergy with one, or even all, of the amps or speakers. CD's played through that digital front end are going to have a lot of jitter and the DAC section is anything but ideal. (A _good_ amp will magnify a bad D/A conversion and your ears will notice it as harsh or fatiguing, a reason often work well in a home system to get rid of the digital "edge"). So you _may have proved that the JL is a revealing amp,_ good to know when selecting other components for your in-car build, in that, you may not be able to mask a weak link in the chain and the JL does not respond well to mid-fi.

3) Unless you have speakers with a very flat response curve (think Focal Utopias, Rogers/Harbeth or similar quality in an a well-designed enclosure at the proper listening distance and fully-time aligned with no unwanted harmonics caused by reflections) ...your speakers _will _inject unwanted bias, not to mention their own sonic signature. At the very least, a decent set of headphones is needed to evaluate properly if you don’t have the $ for truly reference-class “flat speakers”.

4) No one properly A/B-ing equipment uses a swticher box ...those things inject more noise than summer road construction in the middle of a Rush concert. Not to mention that setting the gain on each amp is so very difficult becuase our ears often fools us with our mind thinking that a slight change in efficiency, resulting in an increase in volume, has something to do with an increase in quality. (unless the criteria is efficiency and we know that Class D amps have no issues there).

So...what am I getting at: in order to do a proper review you need a test system "chain" close to the anology of a "piece of wire + gain". What you are hearing with your particular setup is a selected combination of mid-fi, in a non-acoustically treated (not neutrally "flat") room...those cement walls and basement sealing are brutal to harmonics/reflections, etc. It's like evaluating an un-dampened car with lots of glass area. The best amps or speakers cannot overcome this obstacle, which is why room treatment/acoutsitcs are just as important as component matching.

Unffortuantely, no part of setting up a reference testing parameter is cheap, (think of it as a gold chain, as soon as you add a rusty iron link, the whole chain looks bad) …that's just the way it is scientifically...in addition to needing the ultimate test instrument (your ears). That said, there is a way to do this sort of testing logically, so the results are meaningful: 1) Clean, regulated power; 2) a good source (your test CD are probably excellent in that sense...but the DAC in that unit is far from "reference" and your DAC is perhaps the single most important piece of gear for anything digital); 3) neutral components in the chain ...uhhh that's where it gets somewhat expensive, although I have seen some well-thought-out inexpensive amps and lower cost passive pre amps that can do the job; 4) the speakers ...what are these adding to the equation that is far from flat and what's missing because of the drop-off at each end?

This is where it gets expensive, because flat speakers that can play at both ends with a wide sound stage don't come cheap and are far beyond most budgets. (I use Stax electrostatic headphones to evaluate most everything but bass). If there's something bad with respect the source, the power regulation and/or anything else in the chain, a quality headphone will bring it out.

What you did accomplish is perhaps show that with that particular chain of components the JL might not be the best amp choice ...in short, there may be a lack of synergy between the JL and the other components. But as others rightly pointed out, those same JL amps, both "bench well" and sound very good in many SQ mobile environments. So ... your test "chain" is highly suspect and probably very far from the neutrality it needs to make your test meaningful. 

_More likely, you’ve shown that the JL 600/4 is very revealing …and that is a good thing!_

Finally, amps designed to work with "clean" 12V power, often perform poorly when run with AC through a power supply, unless that power supply is very, very clean itself ($$). That's why we don't see more home enthusiasts using car equipment in-home.

That said, I do appreciate your candor, the work you put in… and your enthusiasm for trying to accomplish something that is not very easy unless you have a properly treated room and very deep pockets for reference-grade components that "disappear" and allow you to hear only the piece of equipment you’re trying to evaluate. My goal here was not criticize or preach, but rather to show you how difficult it is to do what you were trying to do...not to mention be fair to the many users of JL equipment. OK, I admit I just bought a 600/4 and 750/1 ...so ya...I am injecting some unwanted bias too - Lorne


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## yuri

hi fishlips soup, 

thanks for taking the time and effort with your reply ,you made some excellent points , some i totally agree with..

first let me say my "review" is just my thoughts and opinions of the jl hd600 ..
i am just your average audio fan !
i am not a professional "audio anything" i work construction ... but music is my passion and a big part of my life .. 

one or two points i will try to address ...

firstly the power was supplied by a pair of large batteries ( powersafe 105ah &101lbs each) and some times also by a vibe 13.8 volt 50amp regulated power supply ( made for running caraudio) how clean it is i don't know ? but most listening was using battery's ...

sorry about the poor quality photo ..pic below is the power supply and underneath it is the pair of battery's 











another pic of the power supply and showing one of the battery's i used











this photo shows where i can swap from battery power to the mains power ... notice the anderson connector fixed to the wall (lower right of the pic) that is my hard wiring to the amps ,headunit ect and below that slightly to the left you will see two other anderson connectors ,, one is wired direct to the pair of battery's and the other is wired to the vibe supply ... just takes a few seconds to swap between them ...











another point ! .. as regards my reference cd headunit ...
i would kinda of like to disagree somewhat ....
this is car audio equipment i am playing with here in my garage .. would it not be defeating the point to use anything else as a source other than car audio cd player ????

regards the rockford headunit !
i have owned many high end head-units over the years and found everyone without exception has its own sound signature ie coloration .
i found the rockford to be one of the most neutral sounding units i ever used that is why i use it as MY reference cd source ..

below are some of the head-units that have owned /used in my garage, the rockford is not my favorite sounding by a long way but in my opinion it is the most neutral sounding of them ! ..

































































sorry i am really rushed for time right now .. but i cant wait to get back and discuss some more ..... 

i quick thing before i go ... you hit the nail right on the head !!!!!

SYNERGY 
between the HD and the rockford :bigcry: there is NONE ..... itis the biggest mismatch in caraudio i ever came across ..... i promise i will get back as soon as i can ... 

and thanks again for posting dude ...


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## A-Ron

subwoofery said:


> Interesting post... You now got me curious about the PDx v.2 (F4 & F6)...
> 
> Kelvin



I second that one! Been running the PDX-F4's and I absolutely love them! Of course I've never played with the JL amps...


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## andy74

I just thought I would add my opinion to the jl hd amp 600/4.
I owned one for a very short time and in the time I owned it I was not impressed at all. It was very flat sounding and made all music sound like mp3 format with no sparkle and nothing to attract me to the sound. It has plenty of power that I will say. I ran it on some rainbow vanadiums on the front channels and didn't like it so bridged the four channels down to 2 to give it more power and see if that got it any better. Bridging it to run in 2 channel mode gave it a better sound but still was very flat sounding, I soon realised I didn't like the sound of the jl hd amp and I sold it.
My opinion counts for nothing really only to say I wasn't impressed with the hype I had heard regarding the hd Amps. There very solidly built and compact and powerful but by far are they an sq amp..


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## Coppertone

So saying all of that about what your 600/4 sounded to you, what did you replace it with sir ?


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## ErinH

andy74 said:


> There very solidly built and compact and powerful but by far are they an sq amp..


The two highest scoring cars at MECA finals last year run HD amps only. Not just one high scoring car. The two highest scoring cars. 

So yea... You're right. They're hardly an SQ amp.


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## Got-Four-Eights

Yuri, Thx for your input. It's good to see ppl who actually listen to thier equipment. You have a hell of a nice collection.


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## BuickGN

Now that I've had my 900/5 and 600/4 for a year I feel a little more qualified to comment. I never could hear a difference betwen the HDs, the Leviathan, the McIntosh, the JL 6450, or the cheap Interfire other than the HDs had the lowest noise floor of the bunch and when pushed hard they never audibly gave up. They just amplify the signal and do exactly what they should do. There's every bit as much sparkle from the tweeters as the McIntosh had and every bit as much pop from the midbass as any of the others had. Having this much power and being able to fit it all under the seats, along with the efficiency is what sealed the deal for me.


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## andy74

Coppertone said:


> So saying all of that about what your 600/4 sounded to you, what did you replace it with sir ?


I replaced it with a temporary alpine pdx 2.150 which has been replaced with a genesis s3 4 channel. The genesis is leagues ahead above the hd amp regardless of what's winning what competition.
It's my ears listening to my setup and it's other people's ears listening to others set ups. We all have different views and opinions and this is mine, just the same as its others judging the hd setups.
This is a forum where opinions count and go along way.


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## andy74

bikinpunk said:


> The two highest scoring cars at MECA finals last year run HD amps only. Not just one high scoring car. The two highest scoring cars.
> 
> So yea... You're right. They're hardly an SQ amp.


I knew you would agree with me:laugh:


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## Coppertone

Lol, this is why we have to take what is being said as opinions. We all like what we like and there is no harm in that. I can't say for sure what is the best amp for you as I can't even say what is best for me yet...


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## BuickGN

I find it so hard to believe people are hearing differences in these amps. Back and forth between the Mac and HD the only differences were headroom and noise floor that I could tell and the Dyn Esotars are pretty revealing. I think most would agree that a McIntosh and HD are on opposite ends of the spectrum. I have to question the amps they're being compared to, are they coloring the sound? I've got enough money wrapped up in this thing that if I even thought I heard a difference I would have bought a different/better amp.


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## Coppertone

I personally can't tell a sound difference, I just utilize what fits my application at the time and fill in from there. Once again I have had no formal training when it comes down to it, I go with what I know.


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## quality_sound

I find it funny that people think OS PPIs are amazing and the HDs aren't yes the same guys designed both...


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## matdotcom2000

bikinpunk said:


> The two highest scoring cars at MECA finals last year run HD amps only. Not just one high scoring car. The two highest scoring cars.
> 
> So yea... You're right. They're hardly an SQ amp.


But they can tune their ass off so they could run a pyramid amp and it wouldnt matter


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## msmith

matdotcom2000 said:


> But they can tune their ass off so they could run a pyramid amp and it wouldnt matter


Wait a minute... how could you possibly tune bad amplifier sound quality away?

All the things you guys are talking about: "openness", "graininess", "congestion", etc. are very hard to define, and I know of no processor that can fix them.


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## monkeyboy

True.. If the amp is introducing a bump in response at 80 hz, you could EQ that out. Make things flat again. But if the amp is clipping, has a high noise floor, introducing noise, or isn't following the signal, how would you fix that with an EQ?


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## Niebur3

bikinpunk said:


> The two highest scoring cars at MECA finals last year run HD amps only. Not just one high scoring car. The two highest scoring cars.
> 
> So yea... You're right. They're hardly an SQ amp.


3 things Erin...

1) Do you know for sure that the HD amps run in those cars are unmolested?

2) Did the 2 winning cars actually sound good? I have been to many finals where the winning cars did everything technically correct, but sounded poor when actually trying to listen to "music". 

3) Did most of those scores come from the sq portion or the install portion?

I'm not saying the HD's aren't good amps (I do prefer many others) as they do offer good power, small compact chassis, and good sq. All I am saying is that making its case by use of its competition record does nothing for my opinion. I'm sure Mark could put in virtually any high quality amp brand and achieve the same scores.


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## andy74

Niebur3 said:


> 3 things Erin...
> 
> 1) Do you know for sure that the HD amps run in those cars are unmolested?
> 
> 2) Did the 2 winning cars actually sound good? I have been to many finals where the winning cars did everything technically correct, but sounded poor when actually trying to listen to "music".
> 
> 3) Did most of those scores come from the sq portion or the install portion?
> 
> I'm not saying the HD's aren't good amps (I do prefer many others) as they do offer good power, small compact chassis, and good sq. All I am saying is that making its case by use of its competition record does nothing for my opinion. I'm sure Mark could put in virtually any high quality amp brand and achieve the same scores.


^^^^this..
Winning the competition on points wouldn't equate to winning it on pure sq.


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## t3sn4f2

Niebur3 said:


> 3 things Erin...
> 
> 1) Do you know for sure that the HD amps run in those cars are unmolested?
> 
> 2) Did the 2 winning cars actually sound good? I have been to many finals where the winning cars did everything technically correct, but sounded poor when actually trying to listen to "music".
> 
> 3) Did most of those scores come from the sq portion or the install portion?
> 
> I'm not saying the HD's aren't good amps (I do prefer many others) as they do offer good power, small compact chassis, and good sq. *All I am saying is that making its case by use of its competition record does nothing for my opinion.* I'm sure Mark could put in virtually any high quality amp brand and achieve the same scores.


Not Erin but I think in this case it does. His rebuttal was in response to this claim. 



andy74 said:


> I just thought I would add my opinion to the jl hd amp 600/4.
> I owned one for a very short time and in the time I owned it I was not impressed at all. *It was very flat sounding and made all music sound like mp3 format with no sparkle and nothing to attract me to the sound*. It has plenty of power that I will say. I ran it on some rainbow vanadiums on the front channels and didn't like it so bridged the four channels down to 2 to give it more power and see if that got it any better. *Bridging it to run in 2 channel mode gave it a better sound but still was very flat sounding,* I soon realised I didn't like the sound of the jl hd amp and I sold it.
> My opinion counts for nothing really only to say I wasn't impressed with the hype I had heard regarding the hd Amps. *There very solidly built and compact and powerful but by far are they an sq amp*..


Erin's just saying that how can something that sounds so obviously bad evaluate so well by a group that we at the very least have to consider to be competent.


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## msmith

Niebur3 said:


> 3 things Erin...
> 
> 1) Do you know for sure that the HD amps run in those cars are unmolested?


I know this for sure... feel free to ask Buwalda and Eldridge directly.



> 2) Did the 2 winning cars actually sound good? I have been to many finals where the winning cars did everything technically correct, but sounded poor when actually trying to listen to "music".


Yes, both of the competitors I mentioned have very good sounding cars.



> 3) Did most of those scores come from the sq portion or the install portion?


These cars score very high on both SQ and installation. You can't win without doing well in both areas.



> I'm not saying the HD's aren't good amps (I do prefer many others) as they do offer good power, small compact chassis, and good sq. All I am saying is that making its case by use of its competition record does nothing for my opinion. I'm sure Mark could put in virtually any high quality amp brand and achieve the same scores.


I am sure Mark and Scott could achieve excellent results with other amplifiers as well, but they CERTAINLY wouldn't run amps that put them at a disadvantage.


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## Niebur3

msmith said:


> I know this for sure... feel free to ask Buwalda and Eldridge directly.


Ok.




msmith said:


> Yes, both of the competitors I mentioned have very good sounding cars.


Yes they do, but how much of that is attributed to the amplifiers? I mean, Scott does run the Macs in his "black betty", which is the highest scoring car ever!




msmith said:


> cars score very high on both SQ and installation. You can't win without doing well in both areas.


Correct. I do understand this, but Erin said the 2 highest point total cars ran JL HD amps. I can almost guarantee that more than 75% of that score is due to the install and has nothing to do with the sound of the actual system.


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## Victor_inox

quality_sound said:


> I find it funny that people think OS PPIs are amazing and the HDs aren't yes the same guys designed both...


I heard both and let me tell you this, whoever is saying that they can tell the difference is ****ing liar.


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## schmiddr2

Just so we all know what scoring is what.

_The Sound Quality “SQ Best of Show” award will be presented to the Competitor who receives the highest SQ score in the Sound Quality contest.. The “Install Best of Show” award will be presented to the Competitor with the highest Install score. The Sound Quality League “SQL Best of Show” award will be presented to the Competitor who received the highest total score among all SQL formats (SQ, Install, and RTA Freq Out)._


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## Niebur3

t3sn4f2 said:


> Erin's just saying that how can something that sounds so obviously bad evaluate so well by a group that we at the very least have to consider to be competent.


I have agreed they are solid amps with a compact chassis, but compared with a Sinfoni, Brax, Tru, or ARC SE's, you may be able to hear subtle differences over the HD's. Are these differences noticeable in a car? Debatable. Are they worth the size difference and install issues? Debatable. Will tuning and speakers (including install) make much more of a difference then the amps will? Most Definitely! Will the system sound good at the end of the day with either one.....sure! Do any of my points bring up car audio competitions, when winning depends on many more things then sound? Nope! 

**EDIT**

I just looked at the results from 2011 and Erin was referring to Mark and Todd, I believe. They both do have very good sounding cars. I am not saying they don't. I am saying there are way more arguments to using HD amps then bringing up competitions. 

I mean hell, if we go by competitions (Eldridge) then we should all be running JL components in our cars as well (no offense Manville)!


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## schmiddr2

Everything is debatable except consistent results.

As you can see above the top 2 SQ cars had HD amps. Not install, SQ.

And btw, you could have looked that up as easy as I did.

Also, the amps help them win awards for install too. Part of competing is to win, why not win at both parts. Todds install was amazing, and could have won, just that Marks car is unbelievably put together.


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## Niebur3

schmiddr2 said:


> Everything is debatable except consistent results.
> 
> As you can see above the top 2 SQ cars had HD amps. Not install, SQ.


So, again, Mark uses JL Components for his front stage.....he always wins.....should we all switch to those?

Mark has a NASCAR completely built to be a sq car, should we all do that as well?

Is every one of the best sounding cars currently in existence even doing competitions?


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## msmith

Niebur3 said:


> Correct. I do understand this, but Erin said the 2 highest point total cars ran JL HD amps. I can almost guarantee that more than 75% of that score is due to the install and has nothing to do with the sound of the actual system.


Go to the MECA and IASCA sites and look up the SQ scores. They're all there.


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## msmith

Niebur3 said:


> I mean hell, if we go by competitions (Eldridge) then we should all be running JL components in our cars as well (no offense Manville)!


I wouldn't have a problem with that... 

The C5's that Eldridge runs are completely stock, and not even hand selected. I've designed quite a few demo cars with our components... most people are really impressed when they listen to them. Go figure.

If they don't impress you, I don't take it personally. I know they're really good.


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## schmiddr2

Niebur3 said:


> So, again, Mark uses JL Components for his front stage.....he always wins.....should we all switch to those?
> 
> Mark has a NASCAR completely built to be a sq car, should we all do that as well?
> 
> Is every one of the best sounding cars currently in existence even doing competitions?


Todds car has had the whole dash rebuilt. So what. Did his using JL amps mean all of the other competitors should all use Hybrid Audio speakers like him? That was a stupid argument.

Stop acting like a baby. JL wins a lot and are very install friendly. Get over it.

No one is saying HD amps are the best ever, just that if they are good enough for some of the most experienced car audio guys so they must be pretty damn good.


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## Niebur3

schmiddr2 said:


> Todds car has had the whole dash rebuilt. So what. Did his using JL amps mean all of the other competitors should all use Hybrid Audio speakers like him? That was a stupid argument.
> 
> Stop acting like a baby. JL wins a lot and are very install friendly. Get over it.
> 
> No one is saying HD amps are the best ever, just that if they are good enough for some of the most experienced car audio guys so they must be pretty damn good.


And where have I acted like a "baby" (nice for a mod to say, btw)? I have said they are solid amps and stated reasons why many would want to use them....just have a pet peeve with the whole competition argument as the be all end all.


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## [email protected]

Why is everybody getting butt hurt over a few people not liking the JL HD amps? Who cares what the competition guys use? They will change it up shortly when the next fad of amps roll out. Just like they did before. 

I do love how competition is brought up to gauge a piece of equipments quality. Its 80% install.


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## msmith

BeatsDownLow said:


> Why is everybody getting butt hurt over a few people not liking the JL HD amps? Who cares what the competition guys use? They will change it up shortly when the next fad of amps roll out. Just like they did before.
> 
> I do love how competition is brought up to gauge a piece of equipments quality. Its 80% install.


I get butt-hurt because it's my livelihood. Is that fair enough? :laugh:


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## schmiddr2

lol. I like you Jerry. Was just trying to make a point. It's not that other amps might not be better for SQ, but are they necessary to make a great SQ vehicle? Obviously not. No more arguments from me if we can agree on this.


Yes a lot of people use competitions to document how well equipment works for SQ. We are all competing with our systems, comparing it to our last systems and other peoples systems, so just because someone has a national stage doesn't mean that their car is not a gauge of how our cars sound. And I heard these cars, they were amazing, I'm not just going by what place they came in. So don't accuse everyone of just going by the scores.


Otherwise, I really don't care who uses them. It's just that I can be fair, and the amps obviously work well for a lot of great sounding cars.


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## Niebur3

schmiddr2 said:


> lol. I like you Jerry. Was just trying to make a point. It's not that other amps might not be better for SQ, but are they necessary to make a great SQ vehicle? Obviously not. No more arguments from me if we can agree on this.


Agreed !

I like you too....but I'm not a baby...I'm not....I'm not!!!! :baby:


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## schmiddr2

lol. Good day to you sir.


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## quality_sound

Eldridge's car sounds amazing with real music and that's a car with no carpet on the floor. I can't say the amps are unmolested, but most of the other amps people are claiming are better are just as molested at that level of competition so it's a moot point. Hell, Arc offers mods for their team from the factory.


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## ErinH

OMG... I'll reply later. I think people are COMPLETELY missing the point of my rebuttal. And some are actually unknowingly proving my point.


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## bassfromspace

That Nascar is something to behold.


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## thehatedguy

I have owned Brax amps. The JL HD amps remind me a lot of Brax...a lot. I have told Manville this. Anyone who has ever asked me my opinion on the HD amps normally gets a reply like..."they remind me a lot of my old Brax amps."

I don't want to sound like an amp snob, but I have owned a lot of high end and esoteric amps...and these JLs are right up there with the other a/b designs I have owned.


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## thehatedguy

And most competition formats have seperate SQ and install judging...you don't have to do either if you don't want to.


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## pionkej

Holy crap. I saw this thread yesterday and it's just taken off. I'm glad some people decided to reign things back in.

I'll step out on a limb here and say that from being on this forum for a while, I often hear people refer to Steve Head (aka Audionutz-"big meat"), Mark Eldridge ("Nascar"), and Jon Whiteledge ("The Magic Bus") as having the best sounding CURRENT cars around. I've not heard Whiteledge's bus, but, seriously, Mark E. has to have one of the best sounding cars I've ever heard. The only reason I say "one of" is because I've also heard Todd's (aka Highly) car and it is the "other best" car I've ever heard. They both present a different experience, and I haven't heard either since last year, but they are simply mind blowing.

To me, this proves two things. One, for everybody who says "a lot of competition cars sound like crap"...they are either full of it OR they haven't heard the right cars. Two, JL HD amps don't hinder a person from achieving a great sounding system. In fact, I love how earlier in this thread people argued that the HD's have "inferior" sound to some other amps, people show that HD amps do very good in competition, and two points suddenly show up: competition doesn't always determine the one, true "best" car because everybody doesn't compete (I can agree with this point) AND that it's because those people that do great know how to install and tune. 

HA. So, the lesson is......that if you learn how to install and tune, that fact will dictate "essque" to a much larger degree than what amps you use (which I also agree with). Really doesn't help people very much with that whole, "HD amps just don't stack up to other amps" club does it??? 

I completely understand that some people have a vested interest in showing that "higher end" amps really do make a difference (because they either sell them or because they want to justify the $$ they spent), but the simple fact is that they really don't play a big role in how good a system sounds. TUNING AND INSTALL dictate this more than any other factor. Because of this, I also use HD amps. It isn't because the "cool kids" were using them. It's because they are small, reliable, put out rated power, and fit in my install easily. The fact that I was able to purchase all three HD amps I have, PLUS my 80prs head unit, PLUS my 6to8 processor, PLUS all of my speakers in my system for the same price somebody is currently asking for two Tru Billet 4100's in the classifieds is just icing on the cake (NOTE: some of the items I bought were used--but so are the Billet's in the classifieds).

Finally, a few points I'd like to concede:

I didn't choose Steve Head as an example just to say his system sounds bad. It doesn't. It sounds great in my opinion. Just like Kirk Proffit's and Steve Cook's vehicles. They all sound incredible. It's just that they aren't the "best I've ever heard" but sometimes are regarded as such and so I used him/them to qualify that I've heard more than just those two cars.

I don't fault anybody who wants to run a rare or more expensive piece of equipment for sentimental, asthetic, or functional reasons, I just don't expect to hear they do it because it's got better "SQ". I'm honestly considering using a DRZ or C90 for my source instead of my 80prs solely for the fact that both use 0db as the reference for max volume and I like that (I also considered the Pioneer P9, but the other two asthetically fit my install better).

DAT (Dave) was at The Vinny at the same time as me. He is in Extreme class by choice but his install qualifies him for Modex (my class). He runs a modified Panny Bottlehead and Sinfoni amps. I use an 80prs and HD amps. We both use a 6to8 for processing. I'm using Dayton/JBL/Aura/LPG for my speakers and he has JBL/AP. My car outscored his. I have cut up and fully modified my dash to mount my midbass, midrange, and tweeters up there. He hasn't. This isn't a slight to Dave, he also has a great sounding vehicle and I think he'd say the same about mine. The point is simply that even when you're not dealing with "the best tuners in the world", install/tune will usually dicatate the overall quality of the system than the actual equipment used almost every time (as long as you're dealing with, at least, "good" equipment to begin with).

Again, I hope my post didn't offend anyone who has a car I've heard. My opinion is totally subjective and is my own opinion. None of the car's I used for example sound bad and to someone else they may even be the "best". My point solely rests on the fact that if myself, and others, can consider any car using HD amps to be the "best", they can't possibly be that much worse than any other "top-tier" amp listed in this thread.


----------



## ErinH

John pretty much nailed my point. People say that the HD amps sound bad. The HD amps have shown they are contenders. The argument really lies on understanding how to tune and install. The sonics of the amp is essentially a non issue other than achieving a desired output and an amps capability achieve that task. 

Buy based on form factor, price, and power. Don't get sucked in to the idea that an amp is your downfall when there are NUMEROUS other issues at hand.



Now, as an aside...
I've had my HD amps for around 3-4 years. No issues with them. 
I placed 3rd in MODEX at finals a couple years ago out of 14. 
I placed 1st overall at Freezefest earlier this year out of 17. 

I've also gotten beat on pretty badly. It was never a fault of the amp. It was, however, an issue with my install or tune. The amp simply amplified the signal. It's my fault for feeding them the wrong signal to amplify. 

And no one has ever heard my car and got out saying "sounds like Class D amps". 

True story: a judge at a show gave me a high score. 30 minutes later he was talking to a group of guys about how Class D amps sound bad. Dude never knew I ran class D and my score certainly didn't reflect his sentiments. Since then, he's probably given me te highest scores of any judge on tonality and mid/tweeter response. still doesn't t know I've got three HD amps under my seats. 

I'm not bragging... The point is simply these issues people are speaking about seem to really fly in the face of everyday use. Personally, I'd like the chance to critique some of these cars who's owners vehemently swear class D can't perform well. I'm willing to bet they have other issues going on.

The install and tune is much more important than worrying about amp sonics. As long as the amp is well made it'll perform it's just as it should an that means just amplifying what it's fed.


----------



## highly

Niebur3 said:


> 3 things Erin...
> 
> 1) Do you know for sure that the HD amps run in those cars are unmolested?
> 
> 2) Did the 2 winning cars actually sound good? I have been to many finals where the winning cars did everything technically correct, but sounded poor when actually trying to listen to "music".
> 
> 3) Did most of those scores come from the sq portion or the install portion?
> 
> I'm not saying the HD's aren't good amps (I do prefer many others) as they do offer good power, small compact chassis, and good sq. All I am saying is that making its case by use of its competition record does nothing for my opinion. I'm sure Mark could put in virtually any high quality amp brand and achieve the same scores.


As one of those guys, Let me say:
1) Yep. Stock as the day JL sent them to me. One of them was actually purchased used right here on this forum. Stock 701 that was purchased used here. Third year in car audio, and I built and tuned the car myself. I don't consider myself as one of the best tuners in the world by a LONG shot, but I am persistent. 

2)I am sure there are a few here that can attest to the way the car sounds. The judges seemed to think it sounded OK...

3) 100% sound quality, Extreme class. Built to MECA ModEx standard but competing in Extreme for fun. The only car in any one-seat class to outscore it in Olympic style judging was Mark's car. The show prior (State finals) it outscored his as well (by half a point...LOL)

No tricks, no funny business. I've torn the car down at a local G2G, so there are a few here that have seen it naked to attest to that!


----------



## highly

Unrelated to the thread, but I am so seriously freaking honored to have been brandied about as part of this argument - you have no idea. Thanks for totally making my week. :blush:

-T


----------



## Niebur3

Todd, you have deserved to be part of argument and controversy....lol! I have never heard your car, however, I can only imagine how good it sounds. 

And again, to make myself very clear, I NEVER said the JL amps aren't solid, good sounding amps. I have heard myself that there are better sounding amps out there. However, the JL's are very solid and with their power output, reliability and small footprint, they are hard to beat.


----------



## FartinInTheTub

I was running Soundstream Reference amps which in my opinion are good amps. I needed room so I purchased a 900/5... I was stunned! Sound was crisp, dynamic and very powerful. I like the HD amps so much that I have a 600/4 and 750/1 waiting to go in my car. I love the HD amps and for once I feel completely satisfied with my purchase and have zero buyer's remorse. <----- To me that means a lot


----------



## jimmyjames16

andy74 said:


> I just thought I would add my opinion to the jl hd amp 600/4.
> I owned one for a very short time and in the time I owned it I was not impressed at all. It was very flat sounding and made all music sound like mp3 format with no sparkle and nothing to attract me to the sound. It has plenty of power that I will say. I ran it on some rainbow vanadiums on the front channels and didn't like it so bridged the four channels down to 2 to give it more power and see if that got it any better. Bridging it to run in 2 channel mode gave it a better sound but still was very flat sounding, I soon realised I didn't like the sound of the jl hd amp and I sold it.
> My opinion counts for nothing really only to say I wasn't impressed with the hype I had heard regarding the hd Amps. There very solidly built and compact and powerful but by far are they an sq amp..


Couldn't have said it better myself... I felt the same way...


----------



## ErinH

so, again... people are complaining that an amplifier _isn't_ coloring the sound ("They're flat")? 

I'll take that any day of the week...


----------



## Victor_inox

bikinpunk said:


> so, again... people are complaining that an amplifier _isn't_ coloring the sound ("They're flat")?
> 
> I'll take that any day of the week...


+1 . HD and XD as well is as flat as it can get, perfect amplifier characteristic if you ask me. it's like more distortion makes it sounds "warmer" "tube alike".
and another audiophilistic bull ****. new hi end stuff sounds better then old hi end stuff- end of story. you yours doesn't look elsewhere.


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## jimmyjames16

bikinpunk said:


> so, again... people are complaining that an amplifier _isn't_ coloring the sound ("They're flat")?
> 
> I'll take that any day of the week...


.... "flat" as in ... "not a good way flat"... I felt.. as well as the XD's -that it took away more from the music than it did stay neutral.. something synthetic about the HD & XD's and I can't put my finger on it..


----------



## TOOSTUBBORN2FAIL

^makes no sense. You mean its doing exactly what its supposed to to. Amplify the signal without changing it. If you want an amp to change the signal, you can accomplish that with eq.


----------



## Victor_inox

I hooked up hd600 to some bad ass martinlogans. and put some SACDs to test, I wish I could keep it that way, just not practical having power supply in the middle of the room. usually it's $12000 Krell pushing those puppies. 
like I said before coloration somewhere else in the path, not @ an amp.


----------



## Thumper26

Maybe I missed it, but how did the little sure amp board do? I've found some pretty nice regulated dc-dc converters to run with these, but was curious about the quality. There's a lot of threads on ht forums with people adding caps and other mods. It's made me curious to try them, but never heard any reviews from car people.


----------



## yuri

Thumper26 said:


> Maybe I missed it, but how did the little sure amp board do? I've found some pretty nice regulated dc-dc converters to run with these, but was curious about the quality. There's a lot of threads on ht forums with people adding caps and other mods. It's made me curious to try them, but never heard any reviews from car people.


hi thumper , 
the little sure amp done good imo .
depending how high your bar is set at ? but for the price i would pick one up and try for yourself ... 
personally if i was building low cost 3way active setup i wouldn't hesitate to use one for midrange and tweeters ,while not quite having enough authority to drive midbass to my taste ! but i only ran the amp at 13.8 volts ,but if you could up the voltage to 20volts this may help ?
or maybe more efficient mid bass drivers than i was using ! ....


----------



## yuri

Victor_inox said:


> I hooked up hd600 to some bad as ? s martinlogans. and put some SACDs to test, I wish I could keep it that way, just not practical having power supply in the middle of the room. usually it's $12000 Krell pushing those puppies.
> like I said before coloration somewhere else in the path, not @ an amp.


hi victor .

looks like you had the amp on a pretty good setup and in house ,
i would be interested to know did you find the hd amp fatiguing when you had it hooked up in house ? 

i found when i changed over to the clarion hx-d1 head unit from the rockford the transformation was unbelievable..ie much more musical ..

i can see why some of you guys like them so much but the fatigue was still there , while not as "fast acting " or noticeable it still crept up until the point i was not enjoying the music again ! ...


MAYBE its just my hd600 ?????????? but i cant find anyone local to me that has one that is willing to loan it to me to compare ...

i did install both the 750 and the 600 in my car ,
firstly the 750 replacing my regular sub amp (kenwood kac1023) driving 8 x focal 5ws (5 inch subs) i also ran it with a idmax 10 and at the moment it still in the car powering a pair of cdt es 06+ subs . i have no complaints it's doing a sterling job whatever subs i throw at it . 

the 600 , i run a 3way active front end with 2x 4 channel amps so i first ran the hd600 bridged on my midbass ( cdt es06) replacing my mcintosh mc431m ... 
again i have no complaints it ran the midbass just fine , on average i am driving 500 miles a week but that week was over 750 miles so i spent a good few hours listening . 

sunday before last i swapped over to to run it on my mids (focal 3w2 be) and tweets (genesis D1's) replacing my mcintosh mc420m and reinstalled the mc431m on midbass ...

Monday was a 150mile round trip to work and back ,tweaked the gains once or twice ...

Tuesday was the 150 mile to work and back and another 260 miles that evening due to a family emergence .. i was up from 5.am that morning and didn't get back home until 1.45 am Wednesday morning , driving the 130 mile back from my sisters house blasting the stereo to help keep me awake .... 

Wednesday up again at 5am with less than 3 hours sleep i drove to work and back home that evening in total silence . 150 miles ...

Wednesday evening i pulled the hd600 out of the car .....


Tuesday was a nightmare , i was so tired and stressed that day but i had already made up my mind on Monday about the amp ....
i will repeat what i said 7 months ago 

_"If music is food for the soul , feasting on the hd600/4 left me hungry ,tired and cold ....
Its ability it take a great recording and suck the life and emotion from it is disturbing "_ 

_"Each and every detail and instrument can be followed note for note throughout the track but it stumblingly refuses to combine the instruments and vocals together to form “ music”_

ALL AMPS SOUND THE SAME !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! i never before wanted to smash a amp with a hammer like i did to the hd600 Tuesday night .... the 750/1 is still in the car and i am still liking it 

i must have a rouge amp as i just cant see why i get so fatigued listening to my hd600 and know one else has ?


----------



## thehatedguy

Before you start with all amps sound the same stuff...please please include the rest of the statement- all amps that MEASURE the same, sound the same. All amps certainly do not sound the same.


----------



## yuri

thehatedguy said:


> Before you start with all amps sound the same stuff...please please include the rest of the statement- all amps that MEASURE the same, sound the same. All amps certainly do not sound the same.


it was a sarcastic remark ... hence the bold and caps !!!!!!!!! 

it was for peeps who say a amp is a amp .........


----------



## highly

yuri said:


> it was a sarcastic remark ... hence the bold and caps !!!!!!!!!
> 
> it was for peeps who say a amp is a amp .........


ALL amps that MEASURE the same SOUND the same. That isn't preceded by 'sometimes' or 'on occasion'. 

If you believe that you can hear a difference between two amplifiers that measure the same, that difference is not due to the amplifiers.

If they measure the same, an amp IS an amp. A watt IS a watt.


----------



## Thumper26

I read the statement about the amps being flat as sounding compressed, like it doesn't have a flat response, or not being dynamic enough to maintain realism. I ran a 900/5 for a while and didn't notice this, however. To me, speakers and tuning we're more of my focus. I agree with the statement that install and tuning make a much more noticeable difference. To me, if your jl hd is the glaring weak link in your chain, it's probably also the cheapest link in an otherwise expensive signal path with an excellent install.


----------



## andy74

Thumper26 said:


> I read the statement about the amps being flat as sounding compressed, like it doesn't have a flat response, or not being dynamic enough to maintain realism. I ran a 900/5 for a while and didn't notice this, however. To me, speakers and tuning we're more of my focus. I agree with the statement that install and tuning make a much more noticeable difference. To me, if your jl hd is the glaring weak link in your chain, it's probably also the cheapest link in an otherwise expensive signal path with an excellent install.


This is a very valid point and makes total sense.
I never meant the sound was flat in a good way because to me it was flat in a not good way, to my ears at least.
Install and tuning play a massive part in any competition.


----------



## msmith

Frequency response is easy to measure. So is dynamic range. The HD's have no issue with either one. We're chasing ghosts here.


----------



## highly

msmith said:


> Frequency response is easy to measure. So is dynamic range. The HD's have no issue with either one.


Or signal to noise ratio
Or crosstalk
Or damping factor
Or power output...



msmith said:


> We're chasing ghosts here.


^ What Manville said.

I appreciate that some of you feel that you can hear a difference. Even that some of you feel you perceive a lack of something intangible. A certain blue-grey hue to the music. An ever-so-slight tartness to the upper midrange. A definite odor of daffodils to the cymbals. There is a reason that an entire genre of audiophilia exists that BANKS on these perceptions.

That doesn't make it real. Any more than Santa Claus or Zeus or the Easter Bunny. 

There ARE tangible ways to determine the differences between two things, however.

-T


----------



## quality_sound

^^^That. I've owned my HDs longer than any amp I've ever had (including a number on the list of "better" amps bandied about so far) and the ONLY amps I'd even consider swapping them for would be XDs.


----------



## Niebur3

msmith said:


> Frequency response is easy to measure. So is dynamic range. The HD's have no issue with either one. We're chasing ghosts here.





highly said:


> Or signal to noise ratio
> Or crosstalk
> Or damping factor
> Or power output...
> 
> 
> 
> ^ What Manville said.
> 
> I appreciate that some of you feel that you can hear a difference. Even that some of you feel you perceive a lack of something intangible. A certain blue-grey hue to the music. An ever-so-slight tartness to the upper midrange. A definite odor of daffodils to the cymbals. There is a reason that an entire genre of audiophilia exists that BANKS on these perceptions.
> 
> That doesn't make it real. Any more than Santa Claus or Zeus or the Easter Bunny.
> 
> There ARE tangible ways to determine the differences between two things, however.
> 
> -T


So, every manufacturer shows flat frequency response, good dynamic range, boasts about s/n ratio and damping, and tell us the RMS of the amps.

You claim their are no audible differences, that it is all it our heads about amps sounding different, yet in the real world they do sound different. Hell, even 2 HD amp might sound a tad bit different. So, I might run Sinfoni or ARC SE's or Tru Billets, but if I loose to someone in competition with HD's, that is the basis for them sounding the same or even perhaps better? 

I have the brands I carry on my board all level matched to the 1/10th of a volt, and I can hear subtle differences between them. Are they colored? Well, all show a flat frequency response...so how can they sound different?

I like HD amps, but I do I wonder if all you guys think all amps sound the same why are you even paying HD money for amps? There are much less expensive class d amps available that deliver the same power that also show a flat FR. 

I can tell you I am sick of being called a "audiofool" for hearing a difference. Can those differences be overcome with processing? I honestly don't know...but probably. Do other things make a MUCH bigger difference? Absolutely. Does it ever matter in competition or otherwise that the cymbal decay last a millisecond longer on 1 amp vs another? Probably not!

Run HD's if you want to. Run Audison Thesis if you want to. But can we agree to respect each other and agree there are many reasons for running the equipment that we do in our cars. I mean, do any of you have the balls to make fun of Scott Buwalda for running McIntosh Amps (MCC602TM) in "Black Betty"?


----------



## yuri

msmith said:


> Frequency response is easy to measure. So is dynamic range. The HD's have no issue with either one. We're chasing ghosts here.





highly said:


> Or signal to noise ratio
> Or crosstalk
> Or damping factor
> Or power output...
> 
> 
> ^
> 
> I appreciate that some of you feel that you can hear a difference.
> 
> There ARE tangible ways to determine the differences between two things, however.
> 
> -T



i have decided to send my hd600 to Gordon Taylor the designer and builder of *Genesis* amps ... for full testing .. (he is the tech guru behind http://www.amp-doctor.co.uk )

i am sure with Mr Taylor's pedigree nobody will argue with his results ?.. 

in particular i will ask him to investigate any possible reasons/causes or defeats or a fault with the amp as it induces such listening fatigue with me .... 
i will also ask to take full measurements , ie
signal to noise ratio
dynamic range 
Frequency response
crosstalk
power output ... etc etc .. and any other measurements you guys think that mat be relevant .. msmith or any jl tech guys maybe you can help out here ....

so please shout out what i should ask to be measured /tested /checked 

i will post the full results and any faults that are found when i have them .....


----------



## [email protected]

yuri said:


> i have decided to send my hd600 to Gordon Taylor the designer and builder of *Genesis* amps ... for full testing .. (he is the tech guru behind http://www.amp-doctor.co.uk )
> 
> i am sure with Mr Taylor's pedigree nobody will argue with his results ?..
> 
> in particular i will ask him to investigate any possible reasons/causes or defeats or a fault with the amp as it induces such listening fatigue with me ....
> i will also ask to take full measurements , ie
> signal to noise ratio
> dynamic range
> Frequency response
> crosstalk
> power output ... etc etc .. and any other measurements you guys think that mat be relevant .. msmith or any jl tech guys maybe you can help out here ....
> 
> so please shout out what i should ask to be measured /tested /checked
> 
> i will post the full results and any faults that are found when i have them .....



I am sure he will check it, as he has a whole page about it, but its the bias tracking. From what he says on that page, that seems like it could be something some of you are experiencing. Interesting info on his site.


----------



## highly

I am by no means saying that the amps on your board, all level matched to 1/10 of a volt, all sound the same. To some degree each and every one of them colors the sound, and each in a different way. There is no perfect amplifier... if there was then this conversation wouldn't be happening, and I am not going to sit here and try to say that the JL HD amplifier is that perfect amplifier. Flat frequency response is just one of the numerous parameters that define the degree to which an amplifier colors the sound. I'd also be willing to accept the possibility that there are parameters that we can measure - but do not - that have a perceptible effect on the sound. Out of bandwidth switching noise for instance. 

I _will_ say with a high degree of confidence that if Scott Buwalda hid a set of JL HD amplifiers behind the body panels and just had those big Class A amplifiers light up and wiggle those sexy VU meters like they should nobody would be the wiser and he'd not have scored lower as a result. Only Scott would know the difference. 

I am certain that user perception (seeing the McIntoshes there) will override any existing audible differences between the MCs and the HDs beyond statistical probability. 

Is it possible that the listener's measurement system may in fact be a factor in 'listener fatigue'? After all, we know the calibration of our measurement microphones. What is the calibration of a listener's measurement devices? Would you agree that this also makes a difference?

** I apologize if anything I've typed has caused you to feel like I was attacking >you< or any other individual here. That was not in any way my intent.**

-Todd


----------



## Niebur3

I know you weren't attacking me Todd. It's all good.


----------



## subwoofery

yuri said:


> i have decided to send my hd600 to Gordon Taylor the designer and builder of *Genesis* amps ... for full testing .. (he is the tech guru behind http://www.amp-doctor.co.uk )
> 
> i am sure with Mr Taylor's pedigree nobody will argue with his results ?..
> 
> in particular i will ask him to investigate any possible reasons/causes or defeats or a fault with the amp as it induces such listening fatigue with me ....
> i will also ask to take full measurements , ie
> signal to noise ratio
> dynamic range
> Frequency response
> crosstalk
> power output ... etc etc .. and any other measurements you guys think that mat be relevant .. msmith or any jl tech guys maybe you can help out here ....
> 
> so please shout out what i should ask to be measured /tested /checked
> 
> i will post the full results and any faults that are found when i have them .....


Would be interesting to see phase shifts over the whole bandwith (if any). 
THD over the whole bandwith too - something like a distortion spectrum showing harmonics like I posted many times: 
http://www.diymobileaudio.com/forum/general-car-audio-discussion/114820-speaker-selection-cts-v-3.html#post1465630

Last but not least, see spec and plots change when bridging channels...  

Kelvin


----------



## Thumper26

msmith said:


> Frequency response is easy to measure. So is dynamic range. The HD's have no issue with either one. We're chasing ghosts here.


Like I said, I loved my HD, only sold it because I had to, and then ran two XD's after that. I was moreso trying to help clarify what he was trying to say.

One thing I will say though, is that mics and meters are not human ears, with different designs, sensitivities, and frequency responses. At the end of the day, everyone has their own genetic signature that you can't calibrate.


----------



## ErinH

Niebur3 said:


> So, every manufacturer shows flat frequency response, good dynamic range, boasts about s/n ratio and damping, and tell us the RMS of the amps.
> 
> You claim their are no audible differences, that it is all it our heads about amps sounding different, yet in the real world they do sound different.


Jerry, you know as well as I do that not all amps actually spec the exact same. The point of mine and Todd's posts isn't that there's no potential for them to sound different. It's simply that that particular kind of difference is VERY miniscule in the grand scheme of things; and that's conceding there may be a difference. Again, if they actually do sound different then it absolutely can be measured. There is no set of ears in this world more capable of outmeasuring a good measurement system (ie: AP units or a simple o-scope and time). As long as the product is worthwhile (ie: it's not garbage), then odds are it will do just fine as long as the use meets the application. Obviously trying to drive an amp to deliver 100w when it is only designed to achieve 50w isn't a fair shake but sometimes folks seem to think that kind of comparison and use is enough to justify an argument. 



Niebur3 said:


> You claim their are no audible differences, that it is all it our heads about amps sounding different, yet in the real world they do sound different. Hell, even 2 HD amp might sound a tad bit different. So, I might run Sinfoni or ARC SE's or Tru Billets, *but if I loose to someone in competition with HD's, that is the basis for them sounding the same or even perhaps better? *



whoa...

No one ever said that nor was it implied by me. If you think that's what was meant, you completely missed the point. Which was to counter the statement that the JL isn't an "sq" amp. Well, that's been proven incorrect simply by the number of people who have placed in the top tiers of their respective class... and not against just a couple people. I won out over 17 folks one day and anyone who has seen my install knows it wasn't because it looked pretty. I compete in a sound class only. And I made the point that I absolutely did not say "oh, that's because of my amps". No. It's because of the time I spent trying to aim my drivers. Testing for crazy stuff (that Roxul in my pillars actually worked). And tuning. It has much, much more to do with knowledge of what you're doing than gain. Case in point, same amps... 4 months later... 5th place in my class and probably 10th overall that day. I did horrible. New tweeter install and a crappy tune were to blame. My amps didn't hurt me. I did.

And that particular mantra has been beaten to death, yet people still feel the need to argue over something no one is saying.



Niebur3 said:


> I mean, do any of you have the balls to make fun of Scott Buwalda for running McIntosh Amps (MCC602TM) in "Black Betty"?


Who is making fun of anyone for running anything? Oddly enough, SB is running all HD in his other car. But, I think we already know that. Just pointing it out for those who don't. Which kind of lends credence to the argument... seeing as he owns both brands, do you guys not think if JL was so inferior that he would run it? On that note, would most of the people who have great cars run these particular amps if they were really as bad as some make them out to be? Really think about that.

If I could afford to run Mcintosh gear I absolutely would. But the reason why has absolutely _nothing_ to do with the notion it _sounds_ better. To me, it's simply a label... a label that has a very highly respected brand image. They make cool looking gear that holds up extremely well and holds it value like nothing else I know of in the audio world. Hell, 30 year old amps are going for near MSRP still on ebay and audiogon (RIP, OG Audiogon). I've been staring at an MC7205 for my HT build and have wanted to pull the trigger so many freaking times, it's not funny. 

If I hadn't already owned HD amps from 3 years ago, I might have even highly considered the new v2 PDX amps that came out a couple years back. There are more and more amps that might get my attention as well. 

To me the amp purchase comes down to a few real criterion:

Power Needed
Space Available
Budget
Any known issues (ie: the v1 PDX's had very bad SNR... or, at least, the 4 that I had did...)
Is the company known for making good gear or crap?
Is it a company I would want to support?

If the product fits those criterion, it's on my radar. If it doesn't, it's not. But I don't "make fun" of anyone who goes outside of that set or chooses a product that doesn't satisfy my personal needs. The HD just happens to achieve all of those and that's why I bought them*. 

The only problem I have is with people making very blanketed statements such as the one which initially got Round 2 of this thread going. I don't take people's word for it anymore and I've done enough testing to know not to even trust myself fully. So, someone can tell me that the HD amps sound better than a Mc and I'm still not going to think much of anything about that because it's hearsay until I can either blind test it or objectively test it with measurement gear. Hell, I'd probably still objectively test it just to see if I could pinpoint why I heard a difference (assuming I did). Same thing if someone said X amp did better than Y amp. Unless one of the mfg's is known for crappy product or known for altering the signal in a way that colors the sound on purpose, it's all taken with a half-grain of salt. 

If you like what you run, then rock it. No one is saying you shouldn't. What is being said, however, is that there is a very tangible way to identify the reasons why you hear what you hear. It's either complete psychoacoustics or it's a real occurrence and either of those can be proven with some measurements. FR is number one. I've seen data on amps that actually seem to droop the midrange response. I've seen others that fall off at the top end. I've seen some that just flat out are wonky. 

Hell, I've tested DSP's that do CRAZY stuff and have wound up helping one mfg identify an unknown problem (happened as recently as February) that they NEVER knew about, while _hundreds _of people were already using the product and singing its praises. A FW update resolved that issue and oddly enough, from what I was told by their chief engineer, no one ever said anything of it... as if you could conclude there was a measurable difference (and it absolutely _was not_ marginal), yet people never noticed or complained. Logic drove me to conclude it was likely because they had a preconceived notion it was doing A, when it was really doing C (skip B) so while they could have easily heard something, they convinced themselves otherwise. Perfect case of psychoacoustics and blind testing at its best. 


*FWIW, I bought my 3 HD amps used a few summers back from Doitor who got them used. I've not at all had an urge to try different amplifiers simply because they perform the function I need them to. If the XD series amps offered more output, I'd probably go that route just to save a bit more space. I actually do have an xd600/6 in my wife's car under the passenger seat as well.


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## Niebur3

All very well said Erin. Some of my defensiveness comes from arguing some blanket notions for a very long time. I have no problems at all with what you just wrote!


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## BFYTW

Win on Sunday, sell on Monday. Hey, Manville?  
Its amazing to me how much turmoil can come from the one link in a car stereo that probably matters the least to the overall outcome. We all have our opinions and our beliefs which we cling to. 
I never liked the way JL amps looked. Ugly things if u ask me. I finally broke down and bought a 300/4 slash to try out because i liked the features. Its a good solid amp. Just like every JL sub i have installed for a customer or for myself since 1991. Solid product, does what it says and says what it does. Bravo Mr Smith to everyone in the JL house.. still doesnt change the facf, my JL amp is sitting in the top of my tool box... my ARC is under the seat running my components. 
To each their own gents.


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## btbluesky

So Yuri, has there been any news from the Doc? 

Personally I'm looking for a class d amp, and JL fits the bill, but still abit worry about it. Either the HD or some old zapco, TRU....


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## BuickGN

I don't know if I was being referenced in Erin's post from a month ago but I wanted to clear that up real quick. I've never said the HD sounded better or worse than the Mac. I said I couldn't hear a difference so I naturally went with the smaller, more efficient amp which also has a lower noise floor.


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## quality_sound

btbluesky said:


> So Yuri, has there been any news from the Doc?
> 
> Personally I'm looking for a class d amp, and JL fits the bill, but still abit worry about it. Either the HD or some old zapco, TRU....


I much prefer my HDs to the Zapco DC Refs I used to run.


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