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Discussion Starter #1
I am in the process of setting up a HSU Quad Drive in my HT and I thought I would share my opinions and a few REW plots with others. Yesterday, 3 of the 4 came in; the 4th one should be here today.

I should note that although I had considered subs from Seaton, ED, SVS and Epik, the few reviews of the Hsus were very encouraging. So was Hsu's volume discount on the Quad drive, which is almost buy 3 and get the 4th free.

For now, here are the initial impressions of 3 located on the front wall. The wall is 12.5 feet wide and the subs are placed approximately equidistant, which puts them within 1/4 wavelength even at the 80Hz crossover. So I should be getting co-location boost at least from each adjacent pair. The room is 2050 cu ft.

First off, the visual impressions: Mine are in walnut and the finish is stunning. I don't know how they got the finish that smooth. It is so smooth that you think it is vinyl, but Hsu says it is real wood veneer. I found the magnetic grills to be a mixed bag - they certainly look nice and hold well enough during playback, but easily come off when moving the sub around. This is my first experience with magnetic grills and this may be typical.

Much has been said about the wireless link on the ULS-15. Although I had hard wiring to the front wall of the HT, I did play around with the wireless link a little. It works OK, but I noticed that the residual noise (sub gains set at about 2 o'clock) was higher than when using the hard wire connections. So, hard wired is how I will use them. To be fair, the wireless residual noise can only be heard very near the sub and certainly would be inaudible at the listening position. Backing the gain to 12 o'clock made it disappear also.

When I powered them up, I immediately ran REW using the ECM-8000 mic and the Behringer mixer. I have run many REW plots in that room with my old sub (Velodyne FSR-18) so I knew what the room response was. First run looked odd - several large peaks and valleys that took 6 BFD filters to fix. I EQ'ed them and played several scenes from Dark Knight. Impressive, but where was the bass slam that I should have with this setup? Investigation found that I had left one of the phase switches reversed when I was checking polarity against the mains. So, two of the co-located subs were essentially cancelling each other.

I fixed the phase error and re-ran REW. This time 3 filters flattened it with only 3-4 db boost or cut. Much better. I did not have time to play the Dark Knight scenes again, but the family watched "Obsessed" last night and the subs were extremely clean and smooth sounding. Although that movie is not that dynamic in LFE, the bass notes on music were much smoother and were noticeably quicker than the Velodyne. 50-60Hz notes seem to have much more impact than the Velodyne, likely to the better transient response.

I still plan to use the Velodyne somewhere in the room. I pushed it into one of the rear corners and ran REW - huge dip at 25Hz with the Hsus on, fairly smooth otherwise. I will move it around this weekend and try to find a better position.

The ULS-15 has a ULF trim control that adjusts the amp's internal EQ to boost LF response. It is intended to compensate for less room gain in larger rooms. I have mine set at its minimum boost (50 Hz setting), as recommened by Hsu for smaller rooms. Even at that setting, REW plots show a rising FR below 20Hz. I suppose Hsu's claim of response down to at least 15Hz is real.

I will post more with REW plots this weekend after I get all 4 set up.
 

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Congrats on the subwoofers. Enjoy setting them up in your room. You are very lucky to have the space/budget to run 5 subs in your system.
 

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Discussion Starter #3 (Edited)
OK. The 4th sub arrived today, so I will start posting REW test results. The photo shows the initial setup (don't you just love taking pics in a dark room with a screen?). Wall is 12.5 feet wide. Distance between the outside pair and the center pair is about a foot. Distance between the inner pair is 32".

The first REW plot is with all subs on, BFD in bypass (no EQ). All subs are normalized to the same volume at the prime listening chair. ULF trim on all subs is minimim boost, 50 Hz. ECM-8000 with Behringer mixer into a X-Fi notebook sound card.

The gold plot is with the mic at the center chair. The green plot is at the left adjoining recliner. The purple plot is at the right adjoining recliner.
 

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Discussion Starter #4
OK, 3 BFD filters produced this result. I am not sure I am going to leave it like this - there is a several db boost at 20Hz. I will see how headroom fares with these settings.

This time, the blue plot is the center seat, the red plot is the right of center seat, and the green seat is the left seat. Pretty big room mode there, but that is the dog's seat and I doubt that he will mind:bigsmile:

Enough plotting for today - time to put some pipe organ music on and let these bad boys sing:yay2:
 

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Discussion Starter #5 (Edited)
After a few pipe organ and SACD tracks, my objective evaluation of the Quad Drive is... leesseee.


The system truly came alive with the 4th sub. Never thought it would make that much difference. Transient response and "punch" is exceptional with more than enough headroom. By far the best bass that I have heard in this room. The "air" around 16 Hz organ notes is outstanding.

When I set out to improve my HT sub, the goal was to gain headroom while maintaining LF response. Goal accomplished! And with better LFE extension than the Velodyne FSR-18.

I may try different positions in the room later, but where they are now is going to be hard to beat...
 

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Discussion Starter #8
So....what do you really think :)

RayJr
:bigsmile:

Thanks for your time on the phone, Ray. The Quad Drive is surely an amazing setup, as you already know.

I tried to find their limits yesterday (never did) by playing pipe organ tracks at elevated sub levels. Although the overall system level did not seem that high (I can easily hit 120 db with the K'horns) and there were no audible signs of distress from the system, at the end of the listening session my ears were hurting. With the ear's lower sensitivity to LF, ear pain and damage can sneak up on you with highly capable subs.

I believe that Hsu is being seriously short changed on the internet forums, especially on the ULS-15. As I said on the phone, I considered all the other popular brands. In the end, the Quad Drive fit my needs the best and I could not be happier with their performance. Congrats to Hsu for a truly outstanding product!
 

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:)
Now you see what I mean when I said "I had not test there max output"...cause there seems to be no limit.

RayJr
 

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Discussion Starter #10
:bigsmile:Yep, I completely understand what you meant.

My HT room is dedicated in the basement. When we had the house built in 1985 I finished the basement myself. That was way before HT, but that is where the K'horns were to be. So, I used 2x6 framing with 5/8" particle board on top of that, then 1/4" oak paneling on top of the particle board. So, at least the walls are well braced. Later on when I put a projector in there I put a black with a muted pattern wallpaper on top of the panelling to darken it and to eliminate reflections from the sheen on the paneling.

In my previous house, I had 1/4" panelling on top of 2x4 studs. Looked fine, but the walls absorbed quite a bit of bass (which really might not have been a bad thing.) So, I decided this room was to be braced much better. That is also our tornado shelter room since most of it is underground. Of course, what better room to have the best protection than the HT:bigsmile:
 

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Sounds like you are having fun getting things set up. I can't imagine wanting/needing to use the Velodyne in addition to the quad drive. Nice to have the choice though.
 

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Discussion Starter #12
I can't imagine wanting/needing to use the Velodyne in addition to the quad drive.
I really don't need it for output. I hope that I can use it to help smooth out FR across the seats. I got part of the way there over the weekend. I put it on the left wall, about 5 feet from the corner. It helped the null at the left recliner a little. I tried it again in the left rear corner and the 25-26 Hz null came back.

I am still amazed at the sound quality of the Hsus - really outstanding sub for music as well as HT.
 

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Discussion Starter #13
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 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.
 

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Discussion Starter #16
New REW plots this morning, this time with the left front K'horn and the quad drive on (Velodyne off). Same measurement tools as before (with calibrated mic). Only the main listening position was measured. BFD engaged with 6 filters. No smoothing on the plots.
 

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Great job. You really got those things dialed in.
 
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