My ULS-15 Quad Drive Review

[hjones4841]

For those who at interested, I am posting test results and listening impressions of my new Quad Drive at hometheatershack.com:

http://www.hometheatershack.com/forums/home-audio-subwoofers/20385-hsu-uls-15-quad-drive-review.html

Testing of the subs in different positions in the room will continue over the next few days, but a photo and initial REW freq. response plots are posted already.

[Pete_Hsu]

Thank you so much for the first impressions, Harry!

Do you mind posting some frequency response graphs here as well?

Thanks!

Sincerely,

[hjones4841]

Thank you so much for the first impressions, Harry!

Do you mind posting some frequency response graphs here as well?

Thanks!

Sincerely,

Sure, Pete. First, here is where the subs are located now. The room is 12.5 ft wide x 20.5 ft deep x 8 ft high - just over 2000 cu. ft. Distance between the outside & inside pair is about a foot; about 30" between the inside pair. Three chairs are 11 ft. back from front wall.

[hjones4841]

Here are REW freq. response plots with Audyssey on and the BFD equalizer bypassed. The gold curve is at the main chair, the purple one is at the adjoining recliner to the right, and the green curve is the recliner on the left. Pretty obvious room mode at the left one, but this is the dog's chair and I doubt he will mind:)

[hjones4841]

Now, here is the response with the BFD EQ engaged with 3 filters. I had to boost 20Hz a fair amount to get this, but it does not tax the subs at all.

Here, the blue one is the center chair, the red one is the right chair and the poor dog hears the green one:).

By the way, I used a Behringer ECM-8000 mic and a Behringer mixer feeding an X-Fi Notebook sound card. Oh, and all of them are with an 80Hz crossover and with the mains off (subs only).

[hometheatergeek]

I'm glad you are enjoying the newly found bass nirvana. :D :D :D

I can just imagine what all of those Klipsch with the ULS-15 must sound like. :eek: :D :eek:

One of the best DVD video concerts you must try with the new setup is the Eagles Farewell Tour One from Melbourn. Whenever I demo the Hsu to friends and family that is the music I put on. It has some of the best mid-bass slam. The first DVD is the Eagles playing the Eagles. The second DVD is the Eagles playing some of the solo work that was done by Don Henley and Joe Walsh. "Dirty Laundry" is one of the best songs on the second DVD. Hope to find the time and come out and hear your system in the future.

One other thing can you bypass the BFD and post a graph or see if you really need it now?

[hjones4841]

I'm glad you are enjoying the newly found bass nirvana. :D :D :D

I can just imagine what all of those Klipsch with the ULS-15 must sound like. :eek: :D :eek:

One of the best DVD video concerts you must try with the new setup is the Eagles Farewell Tour One from Melbourn. Whenever I demo the Hsu to friends and family that is the music I put on. It has some of the best mid-bass slam. The first DVD is the Eagles playing the Eagles. The second DVD is the Eagles playing some of the solo work that was done by Don Henley and Joe Walsh. "Dirty Laundry" is one of the best songs on the second DVD. Hope to find the time and come out and hear your system in the future.

Yep, it is TRULY amazing. I got 3 yesterday and the 4th today. The 4th made an amazing difference - far more than expected. The system really bloomed. I suppose it allowed more acoustic coupling between the subs. I read two different sources about spacing for co-location coupling. One said as long as they are 1/2 wavelength apart, you get the full benefit of co-location. The other source said 1/4 wavelength. I am at least 1/4 wavelength between any two up to the crossover freq.

Other notes about the measurements: each sub was set to the same SPL at the main listening chair. The ULF trim on all was set to 50Hz (minimum boost).

About the EQ boost at 20Hz - there is a significant room mode at 26Hz. I bet that is what I was seeing with the mic. I don't think it is a rolloff in the subs; in fact, when listening to pipe organ music, the 32 Hz and 16 Hz notes seem a little "hot." So, the boost may not in fact be needed...

[Pete_Hsu]

Now, here is the response with the BFD EQ engaged with 3 filters. I had to boost 20Hz a fair amount to get this, but it does not tax the subs at all.

Here, the blue one is the center chair, the red one is the right chair and the poor dog hears the green one:).

By the way, I used a Behringer ECM-8000 mic and a Behringer mixer feeding an X-Fi Notebook sound card. Oh, and all of them are with an 80Hz crossover and with the mains off (subs only).

That is brilliant Harry, the center and right seats have a wonderful response in general, and the dog's left seat is where the big dip occurs :D I don't know how you managed to pull that off, but truly brilliant, ha ha :)

Seriously though, looks great! I still remember the last time I heard a QuadDrive system, and it was literally breathtaking...

Sincerely,

[hjones4841]

I still remember the last time I heard a QuadDrive system, and it was literally breathtaking...

Sincerely,

Pete: You folks are seriously being short changed in the other internet forums. I read (and considered) most of the other popular brands, especially Epik, Seaton, SVS and ED. All have their fanboys that say theirs are the best, why would anyone consider anything else, etc. Well, from what I am hearing in my room I doubt that any of the other brands would perform better and some likely would not perform as well. Everyone has their favorite, but in the end the ULS-15 fit my needs the best and I could not be happier with them.

I do have a renewed appreciation for what high LF SPL can do to a person's ears. As we know, the ear is less sensitive to LF; ear pain (and damage) can sneak up on you with highly capable subs. That is what happened to me yesterday. I was trying to find the Quad Drive's limits (never did) by running the subs well above normal levels. There were no audible signs of distress from the subs or the mains. The overall system level did not seem that high (although I can easily hit 120db with the K'horns), but the subs were and after listening to some pipe organ tracks my ears were hurting.

Again, thanks for the great customer service, Pete, and congrats to Hsu for an outstanding product.

[hjones4841]

For comparison, here is the REW frequency response plot for the single Velodyne FSR-18 in the same room, same testing conditions, same crossover point. Only the center seat was measured. I don't remember how many BFD filters were used to get this response. As you can see, LF extension was not a problem with this sub; the overall output capability was.

This is an 11 year old sub that uses Velodyne's servo drive technology, which prevents amp clipping and cone bottoming by limiting output. As a result, distortion remains relatively low, but there is an easily achieved point where increasing system volume no longer increases sub volume - the sub stays the same level while everything else increases. That is the way it was designed. The goal of the sub upgrade was to increase LFE headroom, which the Quad Drive easily did.

A note about the room node at the left chair. The room is symmetrical with the exception of a door on the left side of the room (front of center) and a tall (60") equipment rack immediately to the left of that chair. The turned-off Velodyne was also on the left side of the room near the back. Those may have combined to cause the node there.

[hjones4841]

One other thing can you bypass the BFD and post a graph or see if you really need it now?

The first set of plots in this thread are with the BFD bypassed.

[hometheatergeek]

Thanks

I see it now. I must get better glasses so I don't read that post wrong again. :o

[Pete_Hsu]

Pete: You folks are seriously being short changed in the other internet forums. I read (and considered) most of the other popular brands, especially Epik, Seaton, SVS and ED. All have their fanboys that say theirs are the best, why would anyone consider anything else, etc. Well, from what I am hearing in my room I doubt that any of the other brands would perform better and some likely would not perform as well. Everyone has their favorite, but in the end the ULS-15 fit my needs the best and I could not be happier with them.

I do have a renewed appreciation for what high LF SPL can do to a person's ears. As we know, the ear is less sensitive to LF; ear pain (and damage) can sneak up on you with highly capable subs. That is what happened to me yesterday. I was trying to find the Quad Drive's limits (never did) by running the subs well above normal levels. There were no audible signs of distress from the subs or the mains. The overall system level did not seem that high (although I can easily hit 120db with the K'horns), but the subs were and after listening to some pipe organ tracks my ears were hurting.

Again, thanks for the great customer service, Pete, and congrats to Hsu for an outstanding product.

I really appreciate that, Harry! Multiples of the ULS-15 can make for an amazing experience :) Using four ULS-15 will mean that each subwoofer will only need 1/16th the amount of amplifier power to reach a given SPL level compared to a single ULS-15. That is an absolutely huge decrease in distortion. And not only that, but driver excursion demands are cut by 1/4th, which also reduces distortion. And of course, overall headroom is much much higher too.

I agree that these attributes are underappreciated and underrated by many.

I'm really glad to hear that these subs are keeping up with those very powerful K'horns!

Sincerely,

[hjones4841]

I found out Thursday that it is very easy to hurt your ears with these things. High volume low frequency content kinda sneeks up on you. Since the ears are less sensitive to LF you really don't appreciate the SPL that can come out of these things. Of course, you don't have to play them that loud, but it sure is fun:).

After a few pipe organ tracks at pretty high level followed by a few SACD tracks - all played at elevated LFE settings - my ears were hurting. There were no audible signs of distress from the mains or subs. Like I said, it kinda slipped up on me as I was having some fun trying to find out the Quad Drive's limits (never did).

So, Quad Drive owners, perhaps it would be wise to have a SPL meter on if you decide to test the limits of this awesome system.

[hjones4841]

One of the best DVD video concerts you must try with the new setup is the Eagles Farewell Tour One from Melbourn. Whenever I demo the Hsu to friends and family that is the music I put on. It has some of the best mid-bass slam. The first DVD is the Eagles playing the Eagles. The second DVD is the Eagles playing some of the solo work that was done by Don Henley and Joe Walsh. "Dirty Laundry" is one of the best songs on the second DVD. Hope to find the time and come out and hear your system in the future.

I just ordered the Eagles DVD from Amazon. I was hoping it was on blu ray, but is only on HD DVD. So, I got the standard DVD. At least it is in DTS, right?

[hometheatergeek]

That's what is amazing about this DVD. I play it in my Panasonic DMP-BD35 bluray player and I swear it looks HiDef. And yes the DTS sounds excellent. :D You are really going to enjoy this. My wife and I watch all three hours the first time we put it on and she said 3/4 of the way through, "I feel the urge to stand up and applaud" and I saw her dancing in the kitchen by herself on one of the songs. Enjoy Harry and boy that was funny that I decided to check the forum right now.

[hjones4841]

On a family vacation last year, we stayed at the La Posada Inn in Winslow, Arizona (wonderful place, by the way). I have a photo of my son by the statue and plaque at "Standing on the Corner." Meant nothing to him, but did to me:)

[Ddavidson]

Pete: You folks are seriously being short changed in the other internet forums. I read (and considered) most of the other popular brands, especially Epik, Seaton, SVS and ED. All have their fanboys that say theirs are the best, why would anyone consider anything else, etc. Well, from what I am hearing in my room I doubt that any of the other brands would perform better and some likely would not perform as well. Everyone has their favorite, but in the end the ULS-15 fit my needs the best and I could not be happier with them.

I do have a renewed appreciation for what high LF SPL can do to a person's ears. As we know, the ear is less sensitive to LF; ear pain (and damage) can sneak up on you with highly capable subs. That is what happened to me yesterday. I was trying to find the Quad Drive's limits (never did) by running the subs well above normal levels. There were no audible signs of distress from the subs or the mains. The overall system level did not seem that high (although I can easily hit 120db with the K'horns), but the subs were and after listening to some pipe organ tracks my ears were hurting.

Again, thanks for the great customer service, Pete, and congrats to Hsu for an outstanding product.

A/V Forums (and the like) have long been known as easy prey for marketing manipulation. Renouned and highly reputable audio designers (such as Dr Hsu) have no such need for participating in such activities. The key IMO has always been to get to do "actual real listening comparisions" rather than rely on buying "based soley on the typical spec sheet sales dribble" that is posted on most internet audio forums.

Certainly not surprising to me that your Quad ULS subs are helping you rediscover your enjoyment of music .

Ddavidson

[hjones4841]

I received a calibrated ECM-8000 mic from Cross Spectrum yesterday, so I am running new FR plots with it down to 5 Hz. Here is the Quad Drive with BFD EQ bypassed & Audyssey off. Mains are off. As you can see, there is significant output well below 20 Hz with a large room gain peak at 8 Hz. Subs are at the same location as for the earlier plots.

The green curve is REW's default 80Hz crossover response.

[hjones4841]

Blue plot is Audyssey on, but BFD still bypassed. Some level shift, some improvement in smoothness, but general shape of the curve is the same.

[hjones4841]

This plot is with BFD engaged with 4 filters optimized. I think I can live with this:) but I still need to work on the valley above 100 Hz. I need to run the plot with the mains on to see the results above 80Hz. The main goal of these curves was to see how flat I could get the ULS-15s in my room below 80Hz.

[skool]

Wow, that's an nice FR after BFD is applied. I wouldn't worry about response above 100 Hz if your crossover is at 80 Hz. Your Audyssey should take care of that with your main speakers.

[hjones4841]

Wow, that's an nice FR after BFD is applied. I wouldn't worry about response above 100 Hz if your crossover is at 80 Hz. Your Audyssey should take care of that with your main speakers.

Thanks and yeah, that was my thoughts also. I ran out of time before I could check FR with the mains.

[skool]

Yeah, I would run a sweep of your subs plus mains to see what's your FR looks like above 100 Hz.

[hjones4841]

Yeah, I would run a sweep of your subs plus mains to see what's your FR looks like above 100 Hz.
I re-ran REW yesterday with the mains on. Most of the valley above 80Hz was gone. I added a slight boost around 100Hz to the subs with a BFD filter and now it is essentially flat. Sounds wonderful:D

[Pete_Hsu]

Harry, do you have any pictures of the latest FR with mains on that you could post over here?

Thanks :)

[hjones4841]

Harry, do you have any pictures of the latest FR with mains on that you could post over here?

Thanks :)

Pete, I don't think I saved them. I remember shutting the laptop down, then thinking that "hey, I did not save them":).

I likely will run more later on and will be sure to post them here. Basically, take the previous curve with the optimized BFD filters and remove the valleys above 80Hz, add a pretty flat resonse up to the 200Hz plot limit and that is it.

I was only driving the center (the Belle Klipsch) and the 5 subs (Velodyne on) when I ran them. I suppose I should run another one with LCR and the subs on as another check.

[skool]

I re-ran REW yesterday with the mains on. Most of the valley above 80Hz was gone. I added a slight boost around 100Hz to the subs with a BFD filter and now it is essentially flat. Sounds wonderful:D


That's awesome. I guess Audyssey does have its benefits ;).

[hjones4841]

I guess Audyssey does have its benefits ;).

Mixed feelings on that. For movies, I prefer for Audyssey to be on. Sometimes on music I turn it off. The sound with Audyssey on is much more "forward" with my system, which certainly helps to anchor dialog to the center.

When I first got the BFD and REW, I could not get anything close to a flat response with Audyssey on. Then I discovered that running Audyssey first, then smoothing with the BFD would give me a flat response.

[skool]

Do you have MultEQ XT on your receiver by any chance? It seems like a nice feature to have, but I am finding inconsistencies among people who used it, at least on subwoofer equalization. I wonder if this due to users' error or what.

How many filters are you using on your BFD? I would use as many filters as possible, not only for peaks removal, but to reduce ringing based on your spectral decay as well. If used effectively, BFD should be as good, if not better, than Audyssey. It just require more trials and time and effort. I am thinking of purchasing one myself to EQ my VTF2.3. I had an eQ.2 before by Elemental Design, but didn't like it. It has many limitations.

Also, sorry if I have missed this, are you using BFD before Audyssey or after Audyssey is applied?

Have you heard of Anti-Mode 8033? I stumbled upon a review of it by JohnM on HomeTheaterShack. It's a very interesting device and quite easy to use.

Given that you have four, have you thought of only use 2 up front and two for nearfield in the back? The effects for nearfield can be quite an experience for movies. It may help with your dip below 23 Hz. I am sure you probably won't need any headroom with that room dimension.

[hjones4841]

The AVR is a Denon 5805 with the first generation of Audyssey - don't remember what version it was called.

I am using 5 BFD filters now - the original 4 plus the one for the valley above crossover. There has been quite a bit of discussion about use of more or less filters. Most agree to use only what is needed to get a reasonable flat response (and of course to limit boost). I have not checked spectral display recently or the waterfall - good idea, guess I need to take a look. I had the ringing well under control with all the bass traps before, so hopefully not that much has changed.

Using BFD after Audyssey seems to work best for me; never could get a very flat response the other way around. I also have read about the AntiMode as well as the SVS and Velodyne products. Most folks seem to think that equal results can be had with the BFD, it just takes more time. Plus, on the BFD, care has to be taken when setting the AVR sub output level - high enough for good S/N ratio, but not high enough to clip the BFD's A/D converters. Not that big of a deal, but the sub amp's level control has to make up the difference, + or -.

I probably should move them around the room a bit, but I am soooo hooked on how they sound now:D.

[skool]

I am using 5 BFD filters now - the original 4 plus the one for the valley above crossover. There has been quite a bit of discussion about use of more or less filters. Most agree to use only what is needed to get a reasonable flat response (and of course to limit boost). I have not checked spectral display recently or the waterfall - good idea, guess I need to take a look. I had the ringing well under control with all the bass traps before, so hopefully not that much has changed.


I was also under the same impression as you about the less filters utilized, the better. However, reading the Anti-Mode 8033 review thread by JohnM on HomeTheaterShack, I learned some new interesting things.

On the thread, one person commented,

I think you could use far fewer than 12 BFD filters to get the same or better graph.

Here were JohnM's replies:

I don't agree.

To simply correct the overall level of the frequency response fewer filters could be used, but that would not correct the decay. To correct the decay the filters have to match the modal resonances, it is the resonances in the room that determine how many filters are required.

You should use one filter for each modal peak. The spectral decay plot is the best tool to identify the centre frequencies of the peaks, the modal resonances show up more clearly in the later slices as the rest of the soundfield decays away. The decay plot also makes it easy to see the effect you are having on the decay time as you alter the bandwidth of the peak to get the best match to the mode, and to check you have the correct centre frequency by trying slightly higher and slightly lower frequencies and measuring the result. To accurately counter a mode the filter centre frequency needs to be within 1% of the mode's frequency. 1% corresponds to 1/60th of an octave, which conveniently is the step between frequencies of the BFD. Your "50Hz" peak might be 49.5Hz, or 49.0Hz etc. You will see the difference in the decay plot provided you have the filter bandwidth narrow enough, try starting at 2/60th of an octave on the DSP1124P (or 0.067 octaves on FBQ2496, which specifies the width differently) while identifying the correct centre frequency then vary the bandwidth once the centre frequency is right.

If you looked at his REW graphs using the BFD versus Anti-Mode 8033, although Anti-Mode 8033 was quite effective, the results with BFD was better when looked at Spectral Decay plots. If you're happy about your sound, that's great. I wouldn't change anything. However, if you're looking to maximize your ULS's potential and a "better" frequency response from your subs, I would try some more filters. Either way, you got a really great setup.

[hjones4841]

Here are new REW FR, spectral decay and waterfall plots of the quad drive with Front Left K'horn also on. (Velodyne was off). Same measurement tools as last week's; only the main listening position was measured. 6 BFD filters were used. No smoothing is applied to the plots.
This time I remembered to save them BEFORE hitting the power switch on the laptop:)

[skool]

That's an excellent result! Spectral decays looks great as well!

How does it sounds now?

[hjones4841]

Thanks. Nothing has changed in the room or the sub setup since last weekend's plots - I just remembered to save them this time:)

There was a HUGE improvement in the room's sound when I put in the bass trapping back in January, even before the new subs. I had been on the fence about traps until one of the folks at GIK made recommendations. I started out with 2 of their Monster traps, ended up with 7 of them along with R30 above the suspended tile ceiling. There is a several page thread over at hometheatershack.com room acoustics forum entitled Klipschorn Room Treatment that has waterfall plots of the progress along the way. To put it simply, I was completely amazed at the improvement in sound. Modes were attenuated and as a friend said "the bottom dropped out of the room's sound."

So, when the new subs came in, I knew that I had done as much as possible to get the room out of their way. As you can tell from my enthusiastic posts, the sound is phenominal:). The Hsus' quick transient response is well matched to the K'horn's quickness. That was one thing that seemed to be missing with the Velodyne. Sure, the extension was there, but kick drums sounded more like thuds. Certainly the room treatments helped the Velo sound its best, but the "attack front" of bass transients is so much better with the Hsus.

I am thankful to have a dedicated room to stuff all this into. As I have told others, I have a very understanding wife. She understands that room is mine and that the rest of the house is hers:)

[hometheatergeek]

Well I want to give you a huge Thank You for your southern hospitality.

In case you other readers didn't know, Harry picked me up from the Sheraton hotel in downtown Birmingham and took me to his wonderful home. I first had to play with his new puppy. Yes dogs take precedent. Then it was off to his HT room.

Well all I can say is WOW. Seeing four Klipschorns in that room was a sight to behold. Then of course sitting in front of the front speakers like pawns in a chess game were the four ULS-15s. A Quad Drive in Walnut sitting there just waiting to be abused. Well Of course Harry obliged.

We started out listening to some of the Chris Botti Bluray and some of the Stevie Wonder Bluray. Along with the DVD of the Eagles "Farewell Tour 1".
Well all I got to say is JUST DAMN. Imagine if you will sitting inside a very large set of headphones where the iindividual instruments are scattered around a 360 degree circle. And then throw in the bass from the Hsus and you would never need to go to a live concert again. His system can easily hit 130 dbs without any hint of running out of steam.

We then moved on to some movie demos. We started with the first scene from the Quantum of Solace. When that was over I had to take the time to remove the glass and the bullets from my body. That was how intense it was. We watch a couple of other movies then I showed him the scene from Transformers where the helicopter flys into the air base. Then of course I had to show him the Ironhide flip near the end of the movie at least three time. We both had the same response, and you all have heard me say it before, we were both grinning and giggling like little boys who just got away with something.

I forgot that you hadn't seen it before Harry, so when are you going to add this to your collection?

Unfortunately we ran out of time and I was unable to hear my copy of Terminator Salvation. But in May I might get the chance when I have to return to Birmingham.

In closing like you predicted Harry, once my Velodynes die I will have to get a couple more of these extraordinary subwoofers. I hope that Hsu does not discontinue this model unless they get a hankering to build an 18 incher. Hint Hint. :)

[hjones4841]

Thanks for the kind words. Always fun to show off the system. And, I don't think I will be looking for speaker upgrades anytime soon, unless I can figure out a way to replace the Heresy side surrounds with another pair of K'horns:D

[OU812]

Thanks for the kind words. Always fun to show off the system. And, I don't think I will be looking for speaker upgrades anytime soon, unless I can figure out a way to replace the Heresy side surrounds with another pair of K'horns:D


hjones4841,

After looking at the various graphs you posted, I can't even begin to imagine what your system must sound like.

I have "the former" flagship subwoofer system from Hsu (which doesn't even come close to what you have now...:eek: ) and it still "wows" me with the way it sounds.

[hjones4841]

One of the best things I did for my room was to add bass traps. While certainly not equal to the sub upgrade, it made a huge difference in smoothness of frequency response (by supressing room modes) and bass transient response. So, anyone who wants to make the best of what they have, room and sub wise, is advised to look into trapping.

One word of caution, however, they ain't pretty and it will take a LOT of trapping to get the room acoustics under control below 100 Hz. Below 40Hz - forget it. The wavelenths are so long that traps have to be unreasonably large to be effective, or panel absorbers have to be used (thin plywood or Masonite over a wood frame.) Lots of info available on line about pre-made or DIY traps.

[hjones4841]

Next week is my first anniversary with my Quad Drive and I am still smiling. Absolutely no buyer remorse from this guy:D

[hometheatergeek]

They just get better with age eh Harry? Are you looking forward to Iron Man 2? We plan on having a double feature that weekend. :)

[Pete_Hsu]

Congrats! I have to admit that the QuadDrive system is pretty amazing!