Axiom Audio EP500 VS SVS PB12-Plus/2

[ssabripo]

Sherv - Let me try this with some humor mixed in. Taking any number of subwoofers and measuring them in a 4Pi setting with LMS will have ALL of them looking like crap, when compared to a smoothed graph done 2 Pi.

Yes, the SVS looks worse when done 4 Pi. So would my Velodyne DD-18, and your DIY project. The Axiom looks crappier there, too.

However, if you want to see REALLY crappy graphs - run some unsmoothed graphs of a subwoofer in any room.

I will be posting some 10 to 50 Hz in-room graphs this weekend. I top out at 50 Hz because I crossover my system at 50 Hz.

Anyway, the LMS curve done 4Pi is a total anal exam of what the subwoofer is actually producing, with no interference from any other source. Why that fact (and it is fact, regardless what anyone trying to argue with it says) upsets people is beyond me.

Keep in mind, I personally do GP measurements, but stating that 4Pi is more accurate than what I personally do does not seem to offend my masculinity ...

good stuff! just a couple of observations:

1. you are right...LMS is "better" and more detailed. Nobody should deny that (I certainly dont). I think the issue is with the notion that "ONLY LMS is right" that you know who spills. TrueRTA at 1/24 is just as good to get a picture of what is going on, and that is the point of contention I think. We all agree LMS is the flagship, and also VERY expensive, and that RTA serves its purpose just as good. Therein lies the "anality" of things

2. No disagreement there: measurements in room and at GP are fine when taken into context. My only point is that those graphs from Axiom mean beans to me and many others, because of how they were taken...you know that story all too well. I look forward to seeing more of your measurements and graphs....I hope I learn from my measurements too! I will be doing some of both the Ultra and my DIY at GP starting this weekend. The room response will be interesting to see....

 

[jakeman]

In the interest of keeping it civil lets just agree to disagree Shervin. . When you are planning to spend $6,000 on subs like I did last year you can demand and get more comparative info which is why I have so many graphs. Yes I take exception with some of the gospel and hype on things like 4pi vs 2pi testing, high excursion drivers and distortion. Yes I prefer listening to my 500 over my Ultra for the reasons cited above. Yes I believe without a doubt that the 500 is the better sounding sub overall. The bottom line on whether or not its preposterous comes from listening to both subs which I do continually.

Soon I'll upgrade them both again to something that sounds even better. For now the OP can make his own choice based on more complete information and the various opinions.

Congrats on your DIY sub by the way.

 

[craigsub]

Sherv ... Doing the Math, If you use a straight, un-smoothed True RTA graph from 10 to 80 Hz, you will have 72 data points ... With LMS, you will get a bit over 100. Either is more than enough for one of those "raw, crappy" looking graphs.

One thing that smooting does is to take the bass roll off and make any subwoofer look like it has deeper extension than the unsmoothed version will. This happens whether you take Quicksweep and then change it in the "right hand" column, or smooth it within the memory. Someone posted a graph showing both, and they are showing comparable data, though the smoothed version looks prettier than the one I used.

I am looking forward to seeing your measurements this weekend. It should be fun. Do you have a microphone calibrator ?

 

[---k---]

Hey,
Just to get us way off topic, but since we are all looking at a pretty graph:

What happens when you take one of those subs which has a very flat GP/2pi/4pi FR graph to 20hz, and then put it into a room that has lots of room gain down low?

 

[craigsub]

Hey,
Just to get us way off topic, but since we are all looking at a pretty graph:

What happens when you take one of those subs which has a very flat GP/2pi/4pi FR graph to 20hz, and then put it into a room that has lots of room gain down low?

It will look crappy. Haven't you been paying attention ?

That was actually the point of the in room graphs I posted last week. The Behringer will hopefully arrive tonight. That will kick up the listening tests completely.

By the way, from 10 to 50 Hz, my room is really quite good. I cross the speakers there for a couple reasons.

1. It sounds better that way
2. It measures better that way.

 

[ssabripo]

thanks for the compliments John, on the DIY. It was a fun and very learning experience.

Like you, I will just agree to disagree. To me, spending $600 or $60,000 on subs doesn't make me more of a guru or less; sure I would like to know more info, but I rather get that info independently than going to Ron or Tom at SVS and watch them do "graphs" for me, or viceversa, for Ian at Axiom to do the same. I rather learn and read from the Mullens and Yates and Noussaines of the world, and finally get those subs on my home under my conditions and determine what is best. You did just that (get them in your home), and that's great! you like the EP500 more, and that's perfectly fine...others feel the Ultra is better, and that's fine too. Some like apple pie, others like Peach Cobbler.....Nobody, not even you, or SVS or Axiom, can say unequivocably that one sub is the "better sound quality" one as Fact....NOBODY!

High excursion vs Distortion? lets just say that there are two camps on this, and we know where you stand which is fine. Peter Marcks, Dr. Hsu and other highly respected designers also feel that way, and I'm fine with that as well. I'm on the other camp with the Adire, TC Sounds, Ascendant Audio, and AE Speakers of the worlds, and their phylosophies! I highly doubt that anyone that wants high excursion, clean output, low extension, and yet still very musical subs, will say "hmmm....gee, let me NOT get a Tumult, or an Avalanche, or an RP-L, or an AV15, or any high class Long throw/high excursion driver, because it may have IM distortion.....let me instead get one of those small coil, small throw ones".

I'm happy you like your subs, and seriously, I'm happy that we can cordially disagree on technical subjects. My only beef is when statements are thrown out as facts....that's all.

happy bassing, and I don't mean fishing

 

[jakeman]

No problem with me with discussiing subwoofers with people who hold different views as long as its done constructively. And if you got a better mousetrap that's cool with me too. It's a problem though when people choose to dismiss objective data that conflicts with their bias. Or worse when certain individuals deliberately post biased comparative reports. Anyway one day I hope to get the time to do a DIY, but for now I'll just buy and enjoy.

 

[---k---]

Craig, I forgot the smiley in that post. You probably already knew that.

But actually, it was a somewhat serious question. We all know that room gain will really boost the low end. Depending on placement, I can couple a ton of room gain with my sealed subs, that should be way down at 20hz, and I end up with an overall flat response (ignoring the nulls). With a ported sub that is already flat to 20, I would expect to see, oh lets be nice and call it a huge "house curve", but in the few inrooms plots I've seen, this isn't typically the case. In fact, there are big threads about how to create a house curve using a BFD, and most of those people participating we're using ported subs, like the SVS.

I looked for your inrooms, to prove this point, but after ten minutes of searching, I couldn't find them. Maybe they got moved/deleted in the moderating of that thread. It would be nice if you could put all your graphs on a webserver for browsing without wading through the thread. I guess just the correct link to your photobucket account would work.

 

[craigsub]

Ryan ... I should be able to get those graphs back up. What happens on most rooms is a combination of room gain, peaks, and nulls ... and it can look pretty messy. You are quite correct in stating people use the BFD to create a house curve ... they do so because, typically, room gain will not give a uniform house curve.

The Behringer did not arrive today ... bummer ...

 

[bobgpsr]

new IM measurements

Heads up on some new actual IM distortion measurements SVS Ultra vs Axiom EP600:

http://www.htguide.com/forum/showpost.php4?p=244914&postcount=1

 

[Mark Seaton]

Re Bob's post, the same info is up over at HTF as well if someone is registered there and not at HT Guide.

 

[ssabripo]

Re Bob's post, the same info is up over at HTF as well if someone is registered there and not at HT Guide.

Here is the link Mark:

http://www.hometheaterforum.com/htforum/showthread.php?s=&threadid=254553

Personalities and personal conflicts/history aside, I think this was very good work by both Ilkka and very visionary inputs by Ed Mullen....good stuff.

High Excursion drivers and IM distortion, eh?!!

 

[RMK!]

Here is the link Mark:

http://www.hometheaterforum.com/htforum/showthread.php?s=&threadid=254553

Personalities and personal conflicts/history aside, I think this was very good work by both Ilkka and very visionary inputs by Ed Mullen....good stuff.

High Excursion drivers and IM distortion, eh?!!

Hummm,

An emotional diatribe from an immature twice banned pseudo scientist showing data generated in a closet. Yes, this represents a significant advancement in the science of subwoofers.

 

[ssabripo]

Hummm,

An emotional diatribe from an immature twice banned pseudo scientist showing data generated in a closet. Yes, this represents a significant advancement in the science of subwoofers.

some good technical info if you weed thru it...Even Mark thinks so. I took it with a grain of salt, and thought there were some excellent points, particularly some of the guidance from Ed Mullen.

speaking of good stuff Rob, where are some more pics of your setup man? the only one i've seen is at frappr. would be cool to see more man! those MA's look

 

[jakeman]

Hummm,

An emotional diatribe from an immature twice banned pseudo scientist showing data generated in a closet. Yes, this represents a significant advancement in the science of subwoofers.

Yes he has now been banned permanently from AVS as well. What's unfortunate is that less knowledgable people who are unaware of his background will be misled by his pseudo-science. Its also unfortunate to see Ed Mullen named though he wasn't the author.

The general term "intermodular distortion" actually is a catch word for several different difficult to measure distortions including amplitude MD, frequency MD, doppler MD, time induced MD and so forth. Needless to say this is a highly complex area of acoustical physics and to reduce these various phenomena to a single measurement is well...misleading.

From what I can tell from a quick read the basis for the procedure is something called a CCIF test devised 30 or 40 years ago and rarely used today, where 2 frequencies closely spaced are applied to a device and the distortion products are measured often as the difference in frequencies. The test is long out of favour for being too simple to catch all the distortion artifacts created though even when used decades ago the tests were done in close relative spacing at higher frequencies like 15kh and 16kh.

Any plausible measurement of IMD would have to measure amplitude a well as frequency modulation distortion. That would also encompass a measurment of doppler shift distortion and its related distortion artifacts which anyone with the most basic understanding of physics will understand that a cone which moves further will produce more of this kind of distortion.

Any one of these modulation distortion pheneomena is highly complex to measure using the most advanced spectrum analysers, techniques and lab equipment so I wouldn't put any weight on those results.

 

[spyboy]

I gather from the recent lack of posts, that the young man from Finland has been banned from this forum?

 

[jakeman]

Yes he has. With AVS he has been banned from four sites.

 

[silversurfer]

IMHO, those that follow teachings/research of others without question, and the teachers/researchers that do not encourange questioning, have more potential in harm than in good.

When you conduct any kind of of a study or research, you don't use the guidance of just one person.

 

[RMK!]

some good technical info if you weed thru it...Even Mark thinks so. I took it with a grain of salt, and thought there were some excellent points, particularly some of the guidance from Ed Mullen.

speaking of good stuff Rob, where are some more pics of your setup man? the only one i've seen is at frappr. would be cool to see more man! those MA's look

There are a few pics in the Members System Gallery (about three pages in I think).

Speaking of pictures, it would be nice to see how you have deployed that DIY with the Ultra? Have you had a chance to put a finish the enclosure?

 

[Mark Seaton]

IMHO, those that follow teachings/research of others without question, and the teachers/researchers that do not encourange questioning, have more potential in harm than in good.

When you conduct any kind of of a study or research, you don't use the guidance of just one person.

Ilkka can be a real PITA, lacking some tact, but these measurements are hardly only his own doing. What he posted purposely said *preliminary* as it was a snapshot of what was being shown in such testing. I know he plans to do outdoor ground plane testing, and Ed Mullen should be posting a more extensive version of these tests in the near future, measured outdoors. Ed and I have e-mailed back and forth a good bit about the possible means of testing this, and I know he's gathered input from some others who also know what their talking about. My own suggestions would make for a very difficult quantification, and was really a multi-tone test that would still require two different frequency sets to properly measure the range of subwoofers on the market fairly. The good part about the arbitrary 30/70Hz choice is that the 30Hz signal can still push some excursion in most subwoofers. What I did find interesting is that there is a significant higher order component generated at 10Hz. It does perk my curiosity in that some of the spectrograms displayed by Keith Yates had some odd VLF blips that were not in the input signal. IM distortion looks like the likely culprit.