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Discussion Starter · #1 ·
We are going to have a GTG at my place on Saturday June 1st starting at 3:00 PM.


My initial reason for having people over was to have some local AVS friends check out my new sub setup with 8 subs with Stereo Integrity 18" drivers and my JTR Noesis 212 speakers (left, right, and center).

However, we are all very interested in experimenting with different amps when powering speakers and finding out if we can tell a difference between amps and also compare to my receiver. We can do a demo of my system too, but I figure we should wait on the amp comparison first.


We are going to do this testing blind, so it should be interesting.




So far we have various class A/B, class D, class T and class H. I am hoping that someone will have a class A amp and/or a tube amp so that we can have at least one of each type. Here is what we have:



Class A/B - Crown XLS202 (Jonathan), Emotiva XPS-3 (Jonathan)

Class H - EP4000 (Kevin)

Class D - Inuke DSP3000 (Jonathan), Pioneer Elite AVR (Sheldon)

Class T - Lepai LP-2020A+ (Jonathan)


Also, Randy Bessinger is planning on bringing some type of switching device to make it quicker to switch from amp to amp.


Anyone in the KC area that is interested in coming please PM me, I've already sent out a number of group PM's and have the following members planning on attending:


Me

Archaea

MrSmithers

Stitch1

Jedimastergrant

Scrappydue

Randy Bessinger

Robotbunny

Chirpie

Dave (non avs member but building DIY SEOS speakers)


Possibles:


ecrabb

Tesseract67

Dragoson

Beastaudio





Be aware that my hosting abilities are limited, I'm going to buy a bunch of beer but can't afford to supply food. Also... we tend to get loud at times with the volume, we won't do that until after the blind testing is over but just wanted to make that known.
 

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Hmm, something I have that's not on the list is a Crown CE4000. It's a different topology than what's listed, but if used on mains and not subs, it has too much noise.
 

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To make this work right with the least amount of bias, you have to have people in attendance that "claim" they have the ability to hear such differences.


Otherwise if nobody has claimed they can, then the "sample set" could be biased by people who actually cannot hear such things.


50% "can's" and 50% "cant's" would be most ideal.


The only other way to overcome this, is to have a fairly large sample set of people.
 

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Quote:
Originally Posted by RobertR  /t/1472180/do-amps-matter-kansas-city-blind-amp-comparison-gtg/0_100#post_23300635


You need to make sure it's a double blind test, not just single blind, else you'll be passing nonverbal clues to each other.

Good point.


Also, fan noise revealing the item under test.


For example: the start up noise of a clone or an idling iTech is unmistakable (because you could hear it from 80ft away.)


Or the delayed relays or power-on button noise; a clear give-away.
 

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Carp has a seperate room we can put the amps in to rule out fan noise --- in addition all of these amps listed have fan mods and are impossible to tell they are on from more than a few feet away. ground loop hum and such is potentially a different problem --- not sure how to counter that one exactly. We can have cheater plugs on hand --- I hope that's sufficient. Some amps seem to have it in his room and some don't.


Yes, we do want to test these amps on mains to test for audible difference because none of use think we can tell any difference on subwoofer usage outside of power.



For my part I know I'm farily confident I can tell a difference between the Inuke stock and the Crown XLS or Onkyo TXNR-1007. It is both measurable with a omnimic and audible to my ears. I don't think I could tell a difference between the Onkyo and Crown, and I'm unsure if I can tell a difference with the emotiva.


Carp is pretty sure he can tell a difference between the Crown and his Pioneer.


I don't know about the rest of the guys. I traditionally am from the camp that amps don't matter that much if they are reproducing the sound accurately --- and measure with the same frequency response. But I'm curious to verify if that's true, and will certaintly be critically listening to the best of my ability. The fast switching function of the box Randy Bessinger is providing will be critical for this meet's success. Listening to the amps even 5 minutes apart and trying to tell a difference will be worthless IMO.

Randy has the CS5 RM2 shown on this website
http://home.provide.net/~djcarlst/abx_hdwr.htm



I found a couple source and speaker switchers on Amazon we could purchase as alternate devices, but I don't know how good they are in comarison to what Randy has.

Obviously you don't want your switch box to color the 'sound' or output quality of the amps.

http://www.amazon.com/4-ZONE-Speaker-Selector-Switcher-Control/dp/B003ED2DZA

or
http://www.amazon.com/Selector-Switcher-Splitter-Impedance-Matching/dp/B004ZGVU7W/ref=cm_cr_pr_product_top


Any input on the offerings from amazon? Does anyone have a very high quality switcher we could borrow in addition to Randy's unit to ensure we are covered? Our group would pay shipping both ways to ensure we have backup for g2g day. We'd like to iron out the details in advance and make this testing as valid as possible.
 

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Discussion Starter · #7 ·

Quote:
Originally Posted by GIEGAR  /t/1472185/do-amps-matter-blind-amplifier-testing-gtg#post_23301519


Now this should be really interesting!


Carp, you're a brave man... you realise that if you don't get the procedure spot on (or clearly state any limitations of same), when the results don't fall the way people are "comfortable" with, nit-picking the methodology after the event will likely be the focus, rather than reflecting on what the results of the day generally indicate. Nah! That wouldn't happen, would it?



Think I can see where James is going with the XT -v- XT32 idea (ie. that's where the real audible difference is, right?) but it looks like another layer of complexity to me. Perhaps for another day (Part 2?).


I've got a few questions/comments on the set-up. Would you rather them here or in the other thread? Not sure of the etiquette.




I'm not too worried about being torn to shreds. At the end of the day my main motivation for doing this is because I want to know for myself. I like discussing it here too of course, but I won't take offense if some people get upset at how we do things in fact I'm looking for input on how we should do this most effectively so - fire away with questions/comments GIEGAR.
 

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This has been brought up recently but y'all are going to need some really dynamic BDs where the author throws in some really hot signals in places. In my opinion that is where having an amp over an avr really shines and a high powered one even more since will have no trouble outputting that signal. The noes will also help show where the extra power is being used "cleanly".
 

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Quote:
Originally Posted by Randy Bessinger  /t/1472180/do-amps-matter-kansas-city-blind-amp-comparison-gtg#post_23302015


this has to be done right. Curtis Chang can we borrow Shawn's QSC switch? I will vouch for returning it. To the extent you are not friends with Shawn can you ask Sanjay? Arny, I have one of the originals... Can u help?

I concur with this 100%.


If people cannot reliably discern through an ABX I have no interest in the results of an "a sounds better than b" trial. No offense to anyone here, it simply does not interest me.


If we're really after the truth a properly executed abx will unearth it.


Good luck!


James
 

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Quote:
Originally Posted by carp  /t/1472180/do-amps-matter-kansas-city-blind-amp-comparison-gtg#post_23301820


I'm not too worried about being torn to shreds. At the end of the day my main motivation for doing this is because I want to know for myself. I like discussing it here too of course, but I won't take offense if some people get upset at how we do things in fact I'm looking for input on how we should do this most effectively so - fire away with questions/comments GIEGAR.

Yeah, you really shouldn't get torn to shreds because I know you fellas will have a red hot go at planning and doing it with the aim of learning and having fun and beer!



The big thing you have in your favour is those ripper JTR Noesis'... by all accounts accurate, clear, very loud and dynamic (zero compression). I reckon their qualities effectively take speaker behaviour out of the mix to allow the group to concentrate on the amps.


I'm by no means an expert at this, but have a few questions that I've seen thrown up previously:
  • The comparison is meant to be conducted below clipping. How will the group ensure/demonstrate that all amps will never clip on any of the material? Is the only way to do this with an oscilloscope?**
  • On the current lineup, I guess the little T-amp will be the limiting factor? The level would have to be selected so it never clips and then the rest of the amps level matched to it right? Which leads me on to...
  • How will the group ensure all amps are level matched? Not sure what the accepted tolerance is for level matching, but I think it's in the order of fractions of a decibel (+/- 0.2dB?).
  • What will be compared to what? Do you intend to set up a matrix whereby every amp will be compared to the AVR only and then all amps compared to each other?


That's about all I can think of at the moment. Good luck and have fun with the planning!



**PS: Actually, what would be really intriguing would be if there was a little bit of occasional light clipping going on and the group still couldn't pick the difference.
 

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Discussion Starter · #12 ·

Quote:
Originally Posted by GIEGAR  /t/1472180/do-amps-matter-kansas-city-blind-amp-comparison-gtg#post_23303075


Yeah, you really shouldn't get torn to shreds because I know you fellas will have a red hot go at planning and doing it with the aim of learning and having fun and beer!



The big thing you have in your favour is those ripper JTR Noesis'... by all accounts accurate, clear, very loud and dynamic (zero compression). I reckon their qualities effectively take speaker behaviour out of the mix to allow the group to concentrate on the amps.


I'm by no means an expert at this, but have a few questions that I've seen thrown up previously:
  • The comparison is meant to be conducted below clipping. How will the group ensure/demonstrate that all amps will never clip on any of the material? Is the only way to do this with an oscilloscope?**
  • On the current lineup, I guess the little T-amp will be the limiting factor? The level would have to be selected so it never clips and then the rest of the amps level matched to it right? Which leads me on to...
  • How will the group ensure all amps are level matched? Not sure what the accepted tolerance is for level matching, but I think it's in the order of fractions of a decibel (+/- 0.2dB?).
  • What will be compared to what? Do you intend to set up a matrix whereby every amp will be compared to the AVR only and then all amps compared to each other?


That's about all I can think of at the moment. Good luck and have fun with the planning!



**PS: Actually, what would be really intriguing would be if there was a little bit of occasional light clipping going on and the group still couldn't pick the difference.


I don't know the answer to your questions, but I'm sure someone that knows will. I honestly don't know yet how everything will be setup.


I do think we should test 2 different ways. I think we should do a test attempting to not have any clipping and then later compare again with the volume cranked up a bit to see how much of a difference that makes. A big motivation for me to try this blind test is to see if I need to buy an amp, and I like it loud at times for music and movies so not testing it that way makes no sense for me.


Also (Archaea brought this up and I agree) I think we need to get a hold of some low sensitivity fuller range towers to use as well. My speakers are 101 db sensitivity rated to 60 hz so that may not tell us much of we can't distinguish between an amp(s) and receiver especially on the non-clipping test.


I didn't know the level matching had to be that close, but we can give it our best shot using my omnimic db meter and calibration disk test tones (I have Avia and Disney's WOW disks).
 

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I've a/b many mid and highend amps over the years, and yes there is or can-be a different sound between amps, more so with driving different loads (speakers). One load may not easly prove to show the differenences between amps while another load would make it easy for everyone to hear it. Also when listening to your favorite tracks, the better amp may only shine above the others for just a few notes, so you really need to listen.. Of couse if someone can't hear it, than to them the amps do sound the same..
 

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Quote:
Originally Posted by joehonest  /t/1472180/do-amps-matter-kansas-city-blind-amp-comparison-gtg#post_23303285


I've a/b many mid and highend amps over the years, and yes there is or can-be a different sound between amps, more so with driving different loads (speakers). One load may not easly prove to show the differenences between amps while another load would make it easy for everyone to hear it. Also when listening to your favorite tracks, the better amp may only shine above the others for just a few notes, so you really need to listen.. Of couse if someone can't hear it, than to them the amps do sound the same..
Please provide a list of speakers that would allow people to hear a difference so the team can try and accomdate.

 

This to me sounds like someone who can't pass a double blind test but still insists they hear differences.  
 

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Quote:
Originally Posted by primetimeguy  /t/1472180/do-amps-matter-kansas-city-blind-amp-comparison-gtg#post_23303315


Please provide a list of speakers that would allow people to hear a difference so the team can try and accomdate.


This to me sounds like someone who can't pass a double blind test but still insists they hear differences.  
I have a pair of magnepan tympani 1d speakers that I only use for stereo music playback. Over the years I have used amps from mac (tube), many A/B class amps, to many to list and now a crown xls1000 class D.

The class D to my ears has a sweet highend, this is without any EQ.. Speakers over the years were AR 3a and JBL L100. I've owned and listened to many other speakers, but these were my favorites over the years


I can say forsure the crown xls 1000 is the best amp for the money that I've owned. I would to buy a crown xls 2500, if Ididn't have the 1000..
 

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Quote:
Originally Posted by GIEGAR  /t/1472180/do-amps-matter-kansas-city-blind-amp-comparison-gtg#post_23303075



**PS: Actually, what would be really intriguing would be if there was a little bit of occasional light clipping going on and the group still couldn't pick the difference.
100db/w speakers being fed 6-700w with one of those Beri amps. After that, I would be intrigued if anyone could accurately discern anything over the ringing in their ears. 130db is loud
 

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Quote:
Originally Posted by AV Science Sales 5  /t/1472180/do-amps-matter-kansas-city-blind-amp-comparison-gtg#post_23304208


Here is a post by Tom Danley on amps that you all might find interesting: http://www.avsforum.com/t/1189404/danley-dts-10-super-spud-diy-kit/210#post_17409024

Thanks for the link Mike, that's a great reference post. One to bookmark.


From that post (bold mine):
Quote:
The amplifiers did not all sound the same, after searching recordings I found a couple parts where one could reliably hear differences, not in anything obvious BUT oddly in the decay parts of the sounds.


Anyway at a modest level (peaks about -15 -20dB on the Thresholds fast meter, it began to be different in a different way, it sounded slightly less dynamic.

I was very puzzled (it was my listening amp at home) and grabbed an oscilloscope and examined the outputs. Sure enough around the point it began to sound less dynamic, it had reached instantaneous clipping.

TO BE CLEAR this is nothing like clipping which everyone knows, this was ONLY detectable if one had a without version to compare to (in this case from a much larger amplifer).

By it self, it sounded fine, no problems and that not hearing the problem is exactly why most sound level meters and other volume level indicators do not show the peak requirements.


Anyway, my point (looking at the clock) it that to preserve or realistically reproduce sounds, you often need a far larger peak level than you would ever guess based on the ubiquitous Sound level meter. Of course all of this is irrelevant if your producing near steady tones, I am talking about dynamics.

You simply can't produce short large peaks unless the system can produce them at all in the first place. Headroom is your friend.

The bold bit describes what I was trying to say above. I think you got it.
 
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