Axiom Audio EP500 VS SVS PB12-Plus/2

[craigsub]

Mark ... A few responses here.

1. If this was intended as a scientific study, subwoofer "A" and subwoofer "B" would have sufficed. If anyone is gullible enough to not see the agenda in the way this "test" was presented, I have a great buy on a bridge in NYC. PM me for details.

2. The graphs mean nothing. I have already had a few chats with people taking me to task for my earlier position about the effects of IMD. When I pointed out to these people what my position always has been, those chastising me were quite surprised.

My position all along is that IMD, like THD, is largely a non issue with subwoofers. Bottoming, Port Noise, Clanking noises, etc ... are all audible.

The difference between, say, 10 and 17% THD/IMD @ 20 Hz is not audible. If you think it is, great, prove it in a blind test.

In order for these "tests" to mean anything, blind tests HAVE to be a part of the study. This new protocol of posting graphs for the sake of posting graphs, with no blind listening tests to help form a correlation between the graphs and what people can hear is just ... meaningless.

Finally ... the quips about "jokeman" instead of jakeman show the level of insecurity among several of you guys in the two threads.

Grow up, "gentlemen".

 

[Manic Miner]

My position all along is that IMD, like THD, is largely a non issue with subwoofers. Bottoming, Port Noise, Clanking noises, etc ... are all audible.

The difference between, say, 10 and 17% THD/IMD @ 20 Hz is not audible. If you think it is, great, prove it in a blind test.

Craig as far as I can tell noone has yet said anything about IMD being audible at a certain level, or that the EP600 is a worse sub then before because it in this test was shown to exhibit more IMD then the other sub.

The interesting part here is that it seems that there is no direct correlation between long stroke, and high IMD, something that jakeman has been claiming for the last few months, without showing any proof.

And THD is audible, at least to me it is. And I would suspect that this holds true for most people. Take a look at an equal loudness curve, you are more sensitive to higher frequencies, so THD should be audible already at not to high levels.

 

[craigsub]

Craig as far as I can tell noone has yet said anything about IMD being audible at a certain level, or that the EP600 is a worse sub then before because it in this test was shown to exhibit more IMD then the other sub.

The interesting part here is that it seems that there is no direct correlation between long stroke, and high IMD, something that jakeman has been claiming for the last few months, without showing any proof.

And THD is audible, at least to me it is. And I would suspect that this holds true for most people. Take a look at an equal loudness curve, you are more sensitive to higher frequencies, so THD should be audible already at not to high levels.

How many blind tests have you either participated in, or moderated, when it comes to the audibility of THD ?

 

[Manic Miner]

And for the rest of you who all of a sudden got your balls in a twist:

I do not think that Ilkkas and Eds experiments was meant as an attack against Axiom. Lighten up.

 

[Manic Miner]

How many blind tests have you either participated in, or moderated, when it comes to the audibility of THD ?

None, nada, ingen! I can tell that you are in one of your moods again, and need someone to lash out at, so there is no point for me to explain to you why I know what THD is

If you want to know, ask me again when you are calm

 

[ssabripo]

Some follow-ups Craig:

1. I actually agree with you, that IMD vs THD is actually inaubible in the ranges and levels the are "real world", ergo, it is a mute point. However, unless my english is waaaaaaaaay off, wasn't this the same exact point that some people were making: in a nutshell, that high excursion drivers "inherently" have more IMD, therefore are not as "good" for music, clean bass, etc? did we or did we not have several threads deleted on this very issue?! wasn't there huge banners posted about the reason Company X and Company Y did not use "high excursion" drivers because their "design choice" was to have "less IMD"?

2. As you mentioned to me, the the klippel test is a perfect example on when IMD is audible....I took the test weeks ago when Ed posted it, and I honestly could not tell. I have to agree with Mark, that there are some really good key findings on that IMD thread. Take the X vs Y out, filter it out, dont worry about "who won" and there is actually really good technical info in there.

 

[craigsub]

And for the rest of you who all of a sudden got your balls in a twist:

I do not think that Ilkkas and Eds experiments was meant as an attack against Axiom. Lighten up.

"Zippy", as he is also known as, has done nothing but attack Axiom for 8 months. As I stated in my response to Mark Seaton, the way that little "test" was done was done so deliberately. If all he was looking at was the relative differences in IMD between short throw and long throw woofers, he could have used a true short throw and long throw driver, and done so discreetly.

He could have purchased a couple of 12 inch drivers from Parts Express, and done his tests there. THAT is what someone looking to test a hypothesis would have done.

 

[craigsub]

None, nada, ingen! I can tell that you are in one of your moods again, and need someone to lash out at, so there is no point for me to explain to you why I know what THD is

If you want to know, ask me again when you are calm

You know, coming from a guy lashing out about "balls in a twist", having comments come from you that I am "in a mood" is pretty funny. Thanks for the amusement.

And no surprise you never took a blind test. Most people are quite intimidated at the thought of actually having to prove with their ears what their eyes told them they heard ...

 

[jakeman]

The interesting part here is that it seems that there is no direct correlation between long stroke, and high IMD, something that jakeman has been claiming for the last few months, without showing any proof..

There is much literature on this true and tried basic point. Its straighforward physics. Here is one to further your understanding from Linkwitz. Note well the comment under " Non-linear Distortion." http://www.linkwitzlab.com/thor-measmt.htm.

The non-linear behavior of a subwoofer increases rapidly as cone excursions become large, because force factor Bl, compliance Cms, and voice coil inductance Le, change with displacement from the resting position. Distortion also changes with frequency, even when the peak-to-peak displacement is held constant.

While its all well and good to come up with new measurement techniques it would be better not coming from someone whose degree of ethics has been shown to be lacking and who has a record of bending pseudo-science to fit his bias. Why reputable people would associate with it is strange to say the least. It really makes me wonder.

 

[jakeman]

"Zippy", as he is also known as, has done nothing but attack Axiom for 8 months. As I stated in my response to Mark Seaton, the way that little "test" was done was done so deliberately. If all he was looking at was the relative differences in IMD between short throw and long throw woofers, he could have used a true short throw and long throw driver, and done so discreetly.

Once again we have a study disguised as testing a hypothesis done with such faulty technique as to render the results invalid. Yet its written and presented in such a manner as to present a scientific finding. If it were true it would run contrary to fundamental principles of acoustical physics. Perhaps a Nobel Prize is in order.

Zippy? I checked AVtalk and he is registered as belonging to the marketing department of another subwoofer manufacturer. Not worth any more discussion.

 

[silversurfer]

1. If this was intended as a scientific study, subwoofer "A" and subwoofer "B" would have sufficed.

I agree with this statement 100%.

120db at 4" does not translate into very high excursion, so I wonder how relevent the test really is.

 

[Manic Miner]

Jakeman: Thanks for the link. I'm not sure if i understand what he is saying the same way as you do. To me it seems like he is writing about what happens when the stroke of the woofer exceeds its linear work area, I could be wrong though

But I found another interesting about THD quote there

The importance of low distortion at very low frequencies can be deduced from the equal loudness contours. The threshold of hearing is around 70 dB SPL at 20 Hz. This is at the level of normal conversation. With increasing frequency the threshold drops rapidly. The loudness contours have an initial slope of 80 dB/dec, or 24 dB/oct, at low perceived volume levels

This means that if the 40 Hz 2nd harmonic of a 20 Hz tone is at a 24 dB lower level, then it will sound equally as loud as the fundamental. This corresponds to 6% 2nd harmonic distortion. The 3rd harmonic distortion would have to be below 1%, or over 38 dB down, in order that it is less loud than the 20 Hz fundamental. It all leads to very low distortion requirements. The fundamental frequency sound pressure level needs to be above 70 dB to even become audible and it should not be masked by higher frequency distortion products.

Basically the same as I said in a previous post, I do not know how anyone can feel that THD is inaudible.

 

[craigsub]

Jakeman: Thanks for the link. I'm not sure if i understand what he is saying the same way as you do. To me it seems like he is writing about what happens when the stroke of the woofer exceeds its linear work area, I could be wrong though

But I found another interesting about THD quote there



Basically the same as I said in a previous post, I do not know how anyone can feel that THD is inaudible.

Maybe we need a Steve Callas "sigh" here. Manic, why don't you write to Keith Yates, and ask him how he could say this :

The Platinum did a more credible job with the U-571 depth charges, which showed a compelling if less than teeth-rattling concussiveness up to a peak level of 107dB (Fig.B4). It got through Pearl Harbor's Gooding-at-the-guns passage at the same level (Fig.D4) without blunting individual gun discharges or adding a flapping/thwocking quality, a reasonably impressive achievement for a unit of this size and price.....In none of these four core movie clips did the Triad's highish measured distortion draw attention to itself; in fact, the unit steadfastly refused to honk, rattle, rasp, or otherwise let on that my torture tracks were discomfiting it. Rather than issue distress cries, it simply stopped getting louder as I slowly turned up the level

about this graph, note the THD @ 107 dB ... ???

We have done more blind tests here in which people, such as yourself, claimed all sprts of things would be audible. However, when the lights went down, suddenly all these audible problems or differences disappeared.

Mr. Yates is pretty exprienced at this listening vs. measurement stuff. Or is Yates no longer a credible source ?

 

[Manic Miner]

What that tells me is that Keith Yates did not hear the sub in question

honk, rattle, rasp, or otherwise let on that my torture tracks were discomfiting it

THD sounds like none of the sympthoms he is describing. In my experience it sounds like that the sound gets 'thicker' and less distinct. Some people will not think of this as something negative, but I'm sure that they can hear it.

It is almost the same effect that is used in movies when there are flames on the screen, for example in Fantastic Four whenever when The Torch was onscreen.

I think I've read the there is a product that adds THD that can be hooked up to your system, if so it is clear that THD is preceived as positive by some.

 

[craigsub]

What that tells me is that Keith Yates did not hear the sub in question

THD sounds like none of the sympthoms he is describing. In my experience it sounds like that the sound gets 'thicker' and less distinct. Some people will not think of this as something negative, but I'm sure that they can hear it.

It is almost the same effect that is used in movies when there are flames on the screen, for example in Fantastic Four whenever when The Torch was onscreen.

I think I've read the there is a product that adds THD that can be hooked up to your system, if so it is clear that THD is preceived as positive by some.

Manic, the quotes I posted were from Keith Yate's listening tests. That means he heard the sub in question - in this case the Triad In-Room-Platinum.

His entire quote in regards to distortion was as follows :

In none of these four core movie clips did the Triad's highish measured distortion draw attention to itself; in fact, the unit steadfastly refused to honk, rattle, rasp, or otherwise let on that my torture tracks were discomfiting it. Rather than issue distress cries, it simply stopped getting louder as I slowly turned up the level

NOTE ... He clearly states the "high measured distortion" did not draw attention to itself. In some cases this distortion was over 60%.

As for what you are hearing, how do you know it is distortion ? How do you know it is not compression ? In my experience, what you described as "thicker" sound usually manifests itself when compression is reached, and not due to distortion.

Compression is much more audible than THD. I know this through actual, real world listening tests.

 

[jakeman]

I do not know how anyone can feel that THD is inaudible.

That is actually a very interesting point that has led many researchers to conduct listening tests to attempt to measure the limits of audibility. Its actually an ongoing area of research with several speaker manufacturers and research facilities. Here is another good site to get you up the learning curve. Take the test. It's fun. I'm near the median around -15-18db. http://www.klippel.de/aura/ You will need headphones.

 

[Manic Miner]

I can't be 101% sure Craig. I have heard Velodyne DD subs at compression without hearing any thickening of the sound (or honking for that sake ) And I have heard B&W ASW 675 and 700, and Velo SPL1200 all exhibit the same behaviour when pushed hard.

I have a huge problem seeing how THD NOT can be audible, does the brain somehow know that the original signal should be 20hz and therefore discard anything produced at other frequencies? I'm sorry, but experience and common sense tells me that THD IS, and HAS to be audible.

I would love to hear Keith Yates take on it though...or anyone else who can explain me why THD is not audible

 

[craigsub]

You have not heard a DD sub at compression. You have heard the servo stopping the driver from moving further. A driver going into compression is pretty audible.

By the way, try the Klippel test. My best was -30dB on the Axiom M-80's ... my worst was -18 dB on my computer speakers.

Even with the Axioms, I pretty much got lucky ... it was a guess after -24 dB. And this was with my head about two feet from the speakers.

Not one person who has tried it at my place has consistently gotten past -18 dB, which is over 10% THD.

 

[Steve42]

I guess one could take the Klippel test and see for themselves just how audible THD when using their own ears. I'm going to try it tonight, sounds cool.

Edit: You beat me to the suggestion Craig. I guess I should have used the "quote" function

P.S. I'm guessing that the test signals do not go extremely low either if they suggest using headphones which usually do not produce lower frequencies very well. And correct me if I'm wrong, but isn't THD usually harder to "hear" the lower the frequency is? At least I would think it would be harder to hear around 20Hz in the case of "subwoofer frequencies".

 

[craigsub]

Here are a couple of graphs for everyone to take a peek at. The first is the Axiom M-80. I do believe it has the lowest THD of any speaker tested by Soundstage ... typically -40 to -50 dB:

Here is the ascend 170 - likely the lowest THD bookshelf... note it is typically about -35 dB through the important midrange:

I have seen guys "claim" to hear -45 dB thd on inexpensive computer speakers. Simply put, that is impossible. The speakers generate much higher levels of distortion than -45 dB...