svs 20-39-isd, pb12-isd, or velo-dls5000r??? (1 Viewer)

[Tom Vodhanel]

>>>Tom, as much as I would like to spend more time responding to some of your comments above, I will avoid doing that in order to respect the decisions of the moderators.> Like it or not, one of the main goals of a vented design is to reduce driver excursion in the low bass, and in turn reduce dynamic distortion in the low bass.> we are not in favor of the other compromises too that are involved with ultra high excursion, including greater manufacturing cost, arguably lower reliability, and higher IM distortion.

 

[Jordan Placheck]

Oh yeah! I'm still reading this. My questions have been answered and I have learned a tons of information through all of these debates. Now I just have to decide which is the best option for me.

 

[SteveCallas]

Wow, he owned two people in one thread lol - well done

 

[rob-h]

I love to see knowledge debunk what may be considered mass fact. There is no shame in being wrong. There is in knowing it and lying to further the argument. This has ben a great thread.

 

[Mark Seaton]

Peter,

To echo Tom V's point here, if you want to keep preaching further about IMD here or elsewhere, please at least perform a simple test or two which actually demonstrates the problem described. Any properly conducted and documented test should be easy for others to replicate. Once you've demonstrated this, then feel free to explain what non-linearity causes this observed artifact.

High excursion woofers most certainly have inherent hurdles which much be addressed, and there have been some DIY offerings that exemplify these problems. Please be more specific in what problems you are referring to. It would appear that some have managed to lump together a few factors that are in fact separate and come from different issues.

Regards,

 

[Peter Marcks]

Tom, you are misunderstanding and misinterpreting our viewpoints on high excursions.

When I say IM distortion, I am referring to what is commonly known as Doppler distortion (apologies to anyone if that was not clear). I am not referring to BL nonlinearities or anything else. Of course we also give serious consideration towards distortion due to BL nonlinearities, why do you think we are using XBL^2 TM linear BL motor technology in our newest drivers?

IM (ie. Doppler in this context) distortion gets exacerbated with higher cone excursions. This is obvious to anyone who has even a basic understanding of IM (Doppler) distortion. There is no evidence needed to prove this, as this fact has already been established. Like it or not, higher cone excursions will increase IM (Doppler) distortion.

Now, in response to the comparison on page 2 of one driver with > 20mm xmax versus another driver of the same size with 8mm xmax...

This comparison really misses the point we are trying to make.

Our viewpoint is that we would rather increase cone area instead of increase driver excursion in order to achieve higher output levels at the frequencies where subwoofer output is limited by driver excursion.

The reasons for this are the same as I have already mentioned: we use a vented system with the goal of reducing driver excursion in the low bass and in turn lowering dynamic distortion in the low bass; ultra high excursion woofers tend not to be very cost-effective; ultra high excursion woofers tend to be less reliable (this should be obvious...the more a woofer is able to move back and forth, the greater chance there is for a problem to occur. In fact, we have made it known on many occasions that adding a second subwoofer increases reliability because driver excursion demands are reduced in half); ultra high excursion means ultra high IM (Doppler) distortion (whether we like it or not, IM (Doppler) distortion becomes exacerbated with higher excursions. If the goal is higher output at frequencies where the subwoofer is limited in output by driver excursion, we would prefer to increase cone area instead of increasing excursion). The audibility is something for future study, just as is the audibility of total harmonic distortion, the audibility of dynamic distortion, or the audibility of any type of distortion in the low bass.). Other problems with ultra high excursion drivers that I have not yet mentioned: they tend to be less efficient and require more power to perform optimally (this further increases cost beyond the increased cost to manufacturer the very high excursion driver); ultra high excursion will increase reactive forces, so the enclosure will have to be strengthened even more (which further adds to cost to manufacture, and adds weight which increases the shipping cost even more to the consumer).

There are some applications where I think it makes some sense to use very high excursion drivers. Mark Seaton's project is a good example of this. He is using a balanced force design and sealed enclosure with the goal of cleanly reproducing very low frequencies without the assistance of a port or passive radiator. However, for a vented design, I feel it is much more cost-effective and makes much more sense not to use ultra high excursion drivers, since one of the main design goals is to reduce excursion in the low bass. Of course, one could argue that a ultra high excursion would come in handy when the subwoofer is variably tuned to a lower frequency. The problem with this is that, with existing methods of variable tuning, port cross-sectional area is required to decrease by 33-50% with each lower tune. So at the same time that driver excursion demands are increased, port flow capability is decreased, which leads to a less balanced design in my opinion.

To put things in perspective: most commercial subwoofers today are limited most in the low bass, and they are limited by porting! In our VTF-3 HO (non turbo) subwoofer, even without ultra high excursion driver and even without ultra high powered amplifier, the porting restricts at 16Hz well before the amplifier runs out of steam and well before the driver runs out of excursion. To achieve as balanced a design as possible, we felt it necessary to substantially boost port flow capability in the low bass (with turbocharger) in an attempt to try to remove or relieve that bottleneck.

 

[mackie]

Good stuff. Can anyone provide a link or two for common folks to learn more about the types of distortion? I get lost in the fb, xmas, IM...

 

[Jack Gilvey]

So, given that the Turbo ostensibly alleviates this low-Fb port compression, a Turbo'd VTF3HO does need an "ultra-high-excursion" woofer to be a "balanced design" (as I alluded to earlier)?

 

[Peter Marcks]

Not exactly, we felt that about 2" peak to peak linear excursion was more than enough to satisfy our design requirements, the requirements being to maintain a relatively even power response without woofer bottoming. Even at maximum output levels where driver excursion demands somewhere above port tuning are highest, the VTF-3 HO woofer should not bottom out. At 16Hz, at maximum output levels, the VTF-3 HO will exhibit no audible port noise as well (with turbo of course).

 

[Evan M.]

Great info as always Peter....and handled professionaly as always without calling peoples opinion "BS". I am really looking foward to doing business with you in the near future. As for the OP's question.....Peter hit the nail on the head.....decide what style you want to go with and try to do your own shootout. This obviously will cost $$$$ to do but who knows.....you may wind up saving in the longrun as you will get the Sub you WANT and not always wonder "what if...."

 

[Jack Gilvey]

You either were not referring to a turbo'd VTF3HO, or you do indeed consider 2" to be "ultra-high excursion"? I already mentioned the porting, so port compression is not the issue.

 

[Tom Vodhanel]

>>>Tom, you are misunderstanding and misinterpreting our viewpoints on high excursions.

 

[Peter Marcks]

Not exactly, we felt that about 2" peak to peak linear excursion was more than enough to satisfy our design requirements, the requirements being to maintain a relatively even power response without woofer bottoming. Even at maximum output levels where driver excursion demands somewhere above port tuning are highest, the woofer should not bottom out.

 

[Jack Gilvey]

You either were not referring to a turbo'd VTF3HO, or you do indeed consider 2" to be "ultra-high excursion"? I already mentioned the porting, so port compression is not the issue.

 

[Ilkka R]

Jack/Peter, you guys are posting the same posts on both forums?

 

[Jack Gilvey]

Peter's posts are identical, so my answers are.

 

[Peter Marcks]

Hello Tom


That is something that you need to figure out.

And about reliability, the point is not that an ultra high excursion driver cannot be fairly reliable. The point is that limiting or reducing driver excursion will lead to higher reliability. That is why we tell people that they will increase reliability when purchasing two subwoofers, because driver excursion demands will be cut in half.

 

[Peter Marcks]

It is a design choice for us to carefully weigh all types of distortions. Remember, higher xmax will not always mean higher headroom because of the various efficiencies involved with driver design. Light cones tend to have high upper bass headroom. Also, the headroom in the lowest bass is typically limited by porting.

 

[Tom Vodhanel]

>>>The new drivers don't have less cone area than the TN series woofers.>ultra high excursion means ultra high IM (Doppler) distortion (whether we like it or not, IM (Doppler) distortion becomes exacerbated with higher excursions.

 

[Peter Marcks]

I already answered this above.

Your argument about reliability just doesn't make sense. It should be obvious that the more a cone is able to move in and out, the greater chance there will be for something to go wrong. In fact, we just had someone post at our forum that I keep hearing about another ID sub company's drivers getting damaged during bass heavy senes in movies...I never hear of this problem with Hsu subs.