VTF15H. Why not the ULS15?

Mostly to do with room size. The uls is a good fit for smaller rooms where the closer boundaries will reinforce the lower frequencies and allow it to dig much deeper than the 15h.

In bigger rooms which have little to no room gain, the 15h is a better choice because the ports give it more output up to its tuning frequencies.

There are also personal reasons of course.

The VTF15h has more output. If output were not a factor, I would go for the ULS.

You will find that most MFG's ported subs will have more output with a few exceptions.

Sort of. If you block the ports, they stop adding to the output. They do not seal the box, thouugh, so, as I understand it, the woofer will still unload below the tuning frequency, which means that if you're going to push it you need to keep a high pass filter in place to avoid killing the woofer. Thus an actually sealed box, with it's gentler rolloff and potentially no need for a high pass filter, can reach lower than a ported box in an all ports blocked configuration.

To some only a sealed sub will do and they usually come in smaller boxes and higher outputs can be obtained with multiple units hence the quad drive option.

Without seeing actual measured results, it's hard to say for certainty but....

The more powerful amp in the ULS would likely show an advantage in output at frequencies above 40 or 50Hz.

The VTF has more output in the deeper bass frequencies due to its port tuning, and that's why most people would rather have it.

If you ran the VTF in sealed mode, the ULS would overall outperform the VTF

Personally I'd rather have the ULS, I prefer the "sound quality" of a sealed sub. It doesn't make sense to buy the VTF and run it in sealed mode to me

I am running dual subs, one ULS and one 15H. IMHO the only reason to get the ULS is if you don't have the room, have WAF issues, or need wireless. My 15H blows the doors off the ULS in all aspects....but i'm sure some will disagree.

In the following review there is some discussion of the difference between the sealed ULS and the ported VTF-3HO + Turbo:

http://www.hsuresearch.com/reviews/SecretHomeTheaterReview.pdf

"With the ULS, transients were more pronounced, with a quicker attack and release than normally found in ported sub. To the listener, it can seem as if there is less output (even though I calibrate levels with all tested subs to match the main speakers). I think that what's happening is that, with a ported sub, the port-induced group delay means that the LF from the sub reaches the listener later than the high-passed upper harmonics comingfromthe main speakers, and likewise extends after the sound from the upper harmonics has dropped off. This creates a "fatter" sound, which the ear sometimes interprets as louder."

All I was saying that if you are going to buy a VTF and run it only in sealed mode, the more powerful amp in the ULS WILL pay off in output above 40Hz. If you plan on keeping it ported, then the VTF is a better bet for home theater.

I always prefer sealed subs myself, so I would prefer the ULS.

This shouldn't be true. If the port plugs are actually blocking the ports it is a sealed box. The need for a HPF would come from the woofer not being able to handle that much power low in frequency. The ULS15 has a much stronger driver, which is why it can handle more power lower in frequency. Porting is far more efficient then sealed, which is why the VTF is a stronger sub.

I too prefer the sound of sealed subs due to listening to music as much as watching movies.. I have a very large room. In order to pressurize the room multiple ULS-15s are required. That is why I am up to three of them now. I have very strong content from 10hz up. With this being said it becomes expensive to use the ULS-15s and this forum will always recommend the "best bang for the buck" So the VTF-15 is the one that is usually recommended over the more expensive ULS.

I know you are only posting the article, but that is the rather stupid to me.
If it sounds "fatter", the ear is interpreting it as "louder", and the quicker attack seems like the output is less, why would you get the sealed sub if you want higher output?? So that on a graph with a microphone it is louder?

Why would they use a model that is no longer made for the comparison the VTF3MK4 and VTF-15H exceed the VTF-3HO in both output and extension not to mention tighter sounding bass.

What it takes to disrupt the resonance of a port is not the same as air tight. AFAIK, air still can pass through the foam (just not as fast or as easily). Thus the potential for the driver to unload. Rome what I've read, if I recall it corerectly. I'd be happy to defer to Mr. Hsu or Mr. Fitzmaurice etc, onaccounta it's possible I could be remembering wrong.

If the foam is closed cell, it is blocking the port = sealed. If some air is passing through still, with open cell foam it would be aperiodic dampening, ie a lossy sealed box. Either way it is no longer bass reflex.

In this case I think it is more personal preference than it is more "bang for the buck." Some people prefer sealed and some ported just as some people are looking for more musical as opposed to HT use. Pete that use to work for Hsu has been quoted as saying it would take 2 ULS to equal the output of 1 15H. If someone is looking for musical and extension I would go for a ULS, but if someone is looking for sheer output for HT than the 15H is the way to go. I am a musician and have the 15h and i was surprised by the sound of the 15H with music compared to my older Outlaw sub so I can only imagine how tight the ULS is. Now if I had the money the question to myself would be 2x 15H or 4x ULS lol, now that would be a fun experiment!

Like the article said, there is 'seems' louder and then there IS louder. You can have a sub measure louder and seem quieter. The 'kind' of higher output you are after is a matter of personal preference. One more thing, with an effects processor, you can make a quicker sub sound slower, but there is nothing you can do to make a slower sub sound quicker.

You'll notice that article is from 2008, when the VTF3HO was still available. By the way, I don't believe the VTF3mk4 would outperform the VTF3HO. The HO was basically the same as the mk3, but with a more powerful amplifier. When paired up with the turbo, it would really beef up its tuning point ouput. Given the size of the ports with the addition of the turbo, I think it might have better deep frequency performance than even the VTF15h. I am just speculating though, we might ask the Dr. to be sure, but the VTF3HO with turbo was certainly nothing to be scoffed at.

"Output" is not the only goal when designing a subwoofer system. Some folks favor extension... on one or both ends of the bandwidth. Others want excellent sound quality. Still others prefer short transient, (temporal), response, (so-called "fast" bass.), while others prefer the "fatter" / "fuller" sound of slow transient response. In addition, the size and shape of the room, as well as the distance to the listening position must be taken into consideration. Finally, the budget comes into play and is the final arbiter of how close the system designer can come to achieving the goals.

Once the goals and priorities are determined, then the system designer can evaluate the strengths and weaknesses of different alignments, (sealed/vented), to determine the best approach to reach the goals within the budget. For example, if the goal is deep infrasonic extension at reference level, in a modest, sealed room, multiple sealed subs will be the most efficient method to achieve that goal. The shallow natural roll-off of sealed subs combined with the "pressure vessel gain", (PVG), experienced in smaller, sealed rooms results in huge output at deep infrasonic frequencies. The ULS-15 works exceptionally well in this scenario, (multiples, of course.)

A sub like the VTF-15H, used in "vented" mode, would be the wrong tool for this job. It rolls off too rapidly to benefit from PVG:



It could be used in sealed sub with it's ports blocked, but you would likely want multiples to achieve useful output:



OTOH, if the goal is Reference Level at 20 Hz and above, and the infrasonics are not important, the vented VTF-15H sub system could be the more efficient choice.

So, before you label something as "stupid", you should try to understand the design choices better. You might make a better decision yourself.

Craig
Edited by craig john - 6/16/12 at 6:51am

Boom (low loud sound) is typically preferred over sound quality (detailed music) here in this forum. I hope one day that paradigm will change.

Are the two mutually exclusive?

I listened to both subs at HSU headquarters (Dr. Hsu did the demo for me). The VTF15H is an amazing sub and wins the SPL per $$ award. But, the ULS15 is tighter with better detail. The ULS15's driver has a MUCH larger magnet structure and is more linear over it's larger excursion. As many have already said or implied in this thread, it comes down to personal preference and values. I bought 2 ULS15s and LOVE them.

Both the VTF-3 and the VTF-15H use a 350 watt amplifier. The older VTF-3HO and the ULF-15 use a 600 watt (continuous) amp. In addition both the HSU VTF-3HO and the ULF-15 use the XBL2 technology (licensed from Adire), in their drivers.

Here is information about the XBL2 tech from Adire:

http://www.adireaudio.com/Files/XBL2DetailsPaper.pdf

Neither the current VTF-3 MK4 or the VTF-15H use the XBL2 technology in their drivers.

In 2008, the time of the review, the VTF-3HO + Turbo was the reviewers reference subwoofer.

Not knocking the older subs but it has not been HSU's nature to go backwards each time they release a new sub it has been an improvement as to the VTF-3HO comparison maybe the good DR. can chime in.

Yes they are until you get something like a S. Submersive. Now I haven't heard them, but from reports they are powerful sealed subwoofers that get really low.

You guys who say you definately prefer ported or sealed sound. I wonder if you could even tell the difference?

These nine enthusiasts largely couldn't when put to that task. Look at the end of post 2 for the summary results.
http://www.avsforum.com/t/1387178/archaeas-kansas-city-blind-subwoofer-shootout-2012/0_50

For instance 66% of the blind voters thought the HSU VTF-15H was a sealed subwoofer.


Here's a snippet summary from post 2:
As to the accuracy of the blind voters on whether they were listening to a ported or sealed or horn sub - it's pretty clear the majority of enthusiasts cannot reliably tell the difference between the different sub designs in blind auditioning as the majority only got it right twice out of seven subs.



Here's a link to the voting tally.
http://www.avsforum.com/t/1387178/archaeas-kansas-city-blind-subwoofer-shootout-2012/350_50#post_21520007


Here's a graphic showing the summary


Edited by Archaea - 6/16/12 at 2:41pm