Anyone know of a review of the Axiom EP-600 Sub - Page 3  

The lies and made up (plagiarized) graph are amazing...standard SVS-envy.

TV puts the IM silliness to bed in that thread. I have to wonder why it seems that we're being set up to accept that a low-Xmax driver is a good thing in and of itself. And, what about our resident Tumult users? That has more excursion than the dreaded TV-12. Does it "come with" more IMD?

Ilkka, sometimes you just have to bring things out in a different light for them to be seen properly. My example just went to show that a high excursion driver does not automatically equal high distortion vs a low excursion driver - it all comes down to implementation.

Yes probably, if both are using say 70% of Xmax. But at same output level, nope.

John, while I concur about the good Dr and his outstanding work, just on that bolded quote I have to comment and slightly disagree:

Ultra high excursion drivers are NOT as expensive as one may think...take for example the driver I'm using (AV15) with an Xmax of 23mm at under $200. Take some extremely long excursion long throw drivers, a la TC9H, TC3, or Adire Brahma ( or the big boy, the Tumult)...all of these, offer extreme performance with very low distortion for well under $500. So, yes, while not as cheap or cost efficient to manufacture as more mainstream drivers, the difference is nowhere near what it was even 5-7 years ago.

second, there is absolutely no correlation between reliability and excursion with today's manufacturing process and driver designs...I have yet to see or hear a vast number of Adire tumults, or SVS ultras, or Stryke Av15 or HE15's, etc, failing at alarming rates....heck, at ANY rate for that matter. If there is, please show me or post a link.

Third, careful on the whole IM subject.....we have beaten this to death. IM distortion is essentially the same for two subwoofers with the same size driver and tune point generating the same sound pressure at a given frequency.

This is because IMD is largely a function of cone excursion. The longer the stroke, the more a woofer will modulate higher bass frequencies. Say the sub is playing 35 Hz and 70 Hz at the same time - then 70 Hz will get modulated more, the louder the 35 Hz tone is played.

The only time IM distortion will increase for the longer stroke sub is when it plays louder than the shorter stroke sub.

We all know the resonator reduces cone excursion at the lowest frequencies - and this in turn lowers IM distortion. But let's look at a frequency above the effect of the resonator (say 35 Hz), where cone excursion will dictate how loud the woofer can play.

If you have two 10" woofers - one limited to 10mm of stroke, and the other at 20mm of stroke, the longer stroke unit will be able to play louder at 35 Hz before the onset of compression and obvious audible distress (like cone cry, suspension noise, and soft bottoming).

Yes, IMD will naturally increase at the point where the longer stroke driver starts playing louder than the shorter stroke driver.

All I'm saying is that this increase in IMD is not as objectionable as compression and audible artifacts attributable to the woofer running out of clean stroke and starting to lose BL (the main reason for THD increase) and stress its suspension (the main reason for cone cry and suspension noise and soft bottoming).

That's the whole fallicy of the "IMD is the biggest evil" argument. A sub will only have higher IMD when it plays louder and strokes longer than its shorter stroke competitor, and that condition will only occur at the very extremes of the operating envelope and only for very breief periods of time.

So again, I'll take more IMD for a fraction of a second with the assurance I won't bottom the woofer or compress out the signal. Because woofer noise and compression are worse than a transient increase in IMD.

just my 0.02 :D ;)

Are you sure that wasn't a full dollar? :D

BTW, great post.

Right.

LOL - I clicked on that HTF link and sure enough Tom V used the same logic in regards to high excursion drivers and distortion against Peter Marks when he repeated Hsu's comments that I used a few posts back against jakeman when he repeated Hsu's comments. I swear I had not seen that up until now too. Hillarious - like he says, the gig is up :D

And we now know that you are really TV's doppelganger :p

So I don't look like a complete hack regurgitator :), here is me mentioning the same theory in less detail to Peter a few days earlier:

http://www.avsforum.com/avs-vb/showt...&&#post7018220

The poster who doctored the graphs...does he have another name at AVS? We have all had strong heated exchanges about the validity of data but I've never seen anyone deliberately alter a graph. Disingenuous to say the least.

Good post Shervin. I had the opportunity to chat with Dr. Hsu about distortion and his design views in much greater detail than what was written above. Very engaging and soft spoken person with clear ideas about design. He continually emphasized how balance was the key to good design and you can see it in the outstanding products manufactured by HSU.

IM distortion occurs in both the driver and the amp as does substantial dynamic distortion. Contrary to the views of another eminent designer who you guys pander to, Dr. Hsu recognizes that such distortions are a fact of life and need to be compromised. Its downright silly to suggest the absence of IM or dynamic or other distortions in high excursion drivers. Dr. Hsu's views are shared as well by Ian Colqohoun. In my books these two designers are the best in the business and their offerings are a cut above other models. While I recognize other designers employ different techniques, I have found the Hsu, Axiom and recently the Velodyne designs to be superior because of their balanced approach. I'm greatly encouraged by them because rather than trivialize the importance of things like IM distortion they acknowledge the problem through their choice of drivers. If it was that simple don't you think everyone would use high excursion drivers, please. :rolleyes: One can always find an aspect of design that has shortcomings but on balance the Hsu approach to distortion as relates to overall sound quality is superior to the SVS approach. The proof is in the engineering excellence and the listening.

Several months ago I posted a graph showing just how bad distortion was on the Ultra at maximum output. No it wasn't doctored or fixed despite the hysterics from Mr. Voldahol. Yes all subs exhibit distortion at maximum output. The TV-12 is a high excursion driver that produces prodigious amounts of distortion at maximum output in the lower frequencies , higher than the fundamental. I own an Ultra and have listened and investigated it thoroughly. The SVS subs are good performers but low distortion at loud volumes and low frequencies isn't one of them and that high excursion driver contributes to that state. There are better quality designs at the same or lower price points.

I'm not looking to start another long tit for tat leading to thread closure. We've been there and those wars belong in 2005. But I do tire of this herd SVS fanboy mentality from several of the above posters regarding SVS design vis a vis other IMO better designs. Dr. Hsu is a brilliant man and his and Mr. Marck's views on distortion are the more reasoned and objective. I can see why the Hsu approach inspires such negativism in less able designers.

When I listen to speakers with other people, I'm always amazed at the differences in the way we perceive things. Up to about three months ago, I tended to really like one brand of speaker that tended to have a lot of output and a very forward sound. I had never really noticed the lack of detail. I really thought they sounded great, and would have been really proud to have them.

Recently, I've been demoing other speakers and really really trying hard to pick up the subtle and not so subtle differences. With the help of a few other people, I've started to hear them. I'm not to the point where I can be placed in a room blindfolded, and when the original ones that I liked are played and will be able to point out every single flaw, just the opposite - I will tell you they sound great. But once the next speaker is turned on, I will go, ah this speaker is better and this is why.

HSU maybe be better balanced and therefore have better SQ, I don't know. But I wonder if this is something that you really really have to listen hard for, and isn't really obvious unless you A/Bed them. I wonder if most of us if placed in a room blind folded with an Ultra would be like ooh ahhhh wow, until we heard the next sub.

And finally, there are different design methods, and maybe there is a reason for that. Maybe one isn't better than the other, it is just different tradeoffs to suite different people's tastes. different strokes for different folks, you know.

The HTF link does not work.

jakeman, that is all fine and good, but you are still missing the point. A high excursion driver, for a given level of output, all else being equal, will have the same or less IM distortion as a low excursion driver. You are only getting more benefits with more excursion - you are not losing anything.

I hate to do a Prozakk, but please address this issue:

The biggest problem I have with all of this is the very loose definition we have here of what is implied by "IM distortion." IM distortion comes from two signals passing through a non-linear medium or system. A wider, flatter BL and suspension curve will improve IM distortion at any given excursion level for a given size driver. There are other factors at play, but a driver with better linearity at high excursion does not make for a good scapegoat on IMD.

High excursion drivers are not without pitfalls to be navigated, and there are real issues that have to be addressed, and there are certainly examples of these problems. That said, it's a very sweeping and vague statement to say that high excursion in and of itself causes IMD to become problematic... especially when no one pushing this has performed any real test to demonstrate it or it being audible.

Right.

According to Klippel, there are three dominant contributors to modulation distortion. Doppler distortion (resulting from cone motion relative to a fixed point) is only one of them. The other two are BL and Le non-linearities. To focus on only Doppler distortion and ignore the other two contributors is an incomplete analysis.

We all know that Doppler distortion is reduced at Fb in a reflex alignment. But that reduction only occurs over a very narrow bandwidth. At all other frequencies in the pass band (i.e., the majority of them), the woofer is solely responsible for generating sound pressure. And except in the Fb bandwidth, sound pressure is direct function of excursion.

Except at Fb, two woofers of the same diameter generating the same sound pressure at the same frequency must - by definition - have the same cone excursion. And if they have the same cone excursion, they generate the same amount of Doppler distortion.

That leaves us with BL and Le non-linearities. These types of non-linearities are minimized when the woofer is operating within Xmax. And when the woofer exceeds Xmax its behavior is - by definition - non-linear and subsequently all forms of distortion (including modulation distortion per Klippel) increase drastically.

Compare two 10" woofers, one with a 10mm Xmax, and the other with a 20mm Xmax. Up to 10mm of stroke both woofers will generate the SAME Doppler distortion. For the sake of discussion BL non-linearities are assumed to be equally low in both woofers at this excursion point (although in reality the 20mm unit will already be showing an edge).

At 15mm of stroke, both woofers will STILL be generating the same amount of Doppler distortion. But the 10mm Xmax woofer will also be generating significant BL non-linearities - and by definition more modulation distortion - since it has already exceeded Xmax by a significant margin. In comparison the 20mm Xmax woofer is still operating within its linear limits and its BL non-linearities are still low and hence so is this form of modulation distortion.

So at 15 mm of stroke, the 20mm Xmax woofer will be generating lower overall modulation distortion that the 10mm Xmax woofer, despite the fact they are both generating identical levels of Doppler distortion.

Because they are more expensive? Have you checked for example how much Tumult costs? That's why HSU HO etc. doesn't have it.

I was wondering today... Do we have any THD/IMD measurements from any HSU? I know Ed has done a couple, but besides them?

I don't know how your (Axiom's) numbers were achieved, but at least the unit I tested, didn't exhibit from any excessive amount of THD at any frequency or level I tested it. As the graph shows, 16 Hz was lowest I tested and it kept the THD at around 14%. That's nowhere near "above fundamental".

http://personal.inet.fi/private/ilkk...eeps_final.gif

Could you point me to the right direction? Which designs are you exactly talking about. I challenge you (or anyone else) to find a sub which can do 100 dB @ 16 Hz @ 14% THD (2 m GP), on any price category if you wish.

Ilkka; has anyone conducted such measurements on a DTS-20?

Just curious, as this unit might fit the bill.

Larry

In 1998, The Hsu 1220 managed 104 dB @ 16 Hz @ 22 % THD, and did so for the then price of $800.

It sure will be interesting to see what the new VTF-3 HO does for $1000 today.

Not that I know. But I'm quite sure it would do it. :)

I tried to search these figures. Are they anywhere around net?

Do you mean these figures?

So the 104 dB (that was probably 1 m) was in-room, not GP.

I'd be very surprised if the new VTF-3 HO can hit 100 dB @ 16 Hz @ 2 m GP. But we'll see soon.

I may have erred ... here is a link to the review done by Don Keele in 1998 for Audio Magazine ... 1220 review with 250 watt amp

Excerpts ...

It appears Mr. Keele did a 2 meter GP session 8 years ago. Talk about ahead of his time !

Anyway, my post earlier is edited.

Yes but as you read it, you'll notice that the THD measurements were taken indoors. 104 dB in-room would equal maybe around 95 dB 2m GP. That would put the new HO at around 100 dB.

Man...I just caught the the OT turn in this thread and THANK YOU MARK for this post. I was gagging on my tongue with all of the generalizations.:p

I would add that IM distortion results from 2 or more inharmonic tones (or, not ssab's example of 35 and 70 Hz).

I agree that too many assumptions about drivers and alignments are made to conclude anything at all about IMD from either of them.

Bosso

It also says : The wording is ambiguous, for sure. However, we will be sure to run a full battery of tests on the Hsu, and match it up against the Ultra.

Should be fun.

Peak can mean so many things. As you have seen, a single Ultra can do around 120 dB @ >16 Hz in-room with a quick sweep. That's why I would use either sine waves or sweeps. And GP environment. ;)

Full battery... :rolleyes:

It is easy to miss. I read it a couple of times, conviced that the THD numbers were still ground plane, because it was hitting 110 db max at 16hz. But this conviced me that Ilka maybe correct:

Yes, little one, and we will actually do some LISTENING tests in a room larger than a walk in closet first. Those tests will be done blind, as usual, and the subwoofers properly calibrated. You should try it sometime.

And again you have outdone yourself. :D

Maybe? :)

It can not be missed. FR tests were GP, THD tests were in-room. So no reliable THD data for that HSU either.