Which sub to augment my TN1220s

[Sorny]

Got a question for the HSU experts...

I have a pair of TN1220HO subs, each with a HSU 500W amp driving them at the moment. I have ample output SPL and low distortion (under 3% everywhere except 17.3Hz, where it's up to 8.5% THD according to REW at -15dB, which is my max listening level).

I started going down the rabbit hole with a MiniDSP 2x4HD, Umik-1, REW, and the like, and want to get the flattest response possible. My current results after EQ are pretty good for the sweet spot, but not so much elsewhere, thus I need another sub to flatten things out some more with less EQ needed.

What is the best match for both output capability and Frequency Response to my TN1220HO subs in the current lineup? I'm not looking for more output, even though I know I'm quite likely to gain output and lower distortion by adding another sub, I'm looking for what's the closest match to the TN's in sound quality, tuning, and whatnot to smooth my response in-room.

Current subs are located equidistant from MLP in back corners of the room. The new sub I'm thinking of getting is probably going to be located close to the MLP to even out some room modes at 23, 46, and ~90Hz.

[Kevin_Hsu]

Hi there,

We don't really have a sub that's very close to that in terms of performance. If you were to get another sub to run along, I would go with one that will either match or outperform it. In this case, the VTF-3 Mk5 HP would probably be the better bet.

[Sorny]

Originally Posted by Kevin_Hsu

Hi there,

We don't really have a sub that's very close to that in terms of performance. If you were to get another sub to run along, I would go with one that will either match or outperform it. In this case, the VTF-3 Mk5 HP would probably be the better bet.

So from a sound quality first standpoint, the VTF-3 is the best match to my TN1220HO's? Ok. So the inevitable follow-up question becomes, what would be the downside of going with a VTF-15 instead from a sound quality perspective, if any?

The price difference isn't enough to scare me, nor is the size & weight, because I've got 2 subs that a mere mortal can move without getting help. So, for the job at hand, which is flatter in-room response, the size & weight aren't big problems.
I know the VTF-15 will have higher SPL, which is low on my list of priorities, I know it'll play deeper, which is a bonus, but not critical, and I'd assume that when I gain match the subs, it'll play at lower distortion (as will the TNs). So, I'm just wondering if the VTF-15 wouldn't be the better buy unless you think there's a downside to the lower port tune and integrating it with the TNs?

You could make my life easier and re-introduce the TN1220HO mk2, just throw the VTF-2 driver in a 4' chunk of sonotube and you'd sell at least 1 pair today.

[Kevin_Hsu]

No downside in going with the VTF-15H MK2. As you stated, barring the TN-1220HO performance, the VTF-15H Mk2 will give you a bit more clean headroom and a little more extension. You do have to keep in mind that the TN may be the limiting factor as it would hit its limits before the larger sub would (bottleneck).

[Sorny]

All good Kevin, I placed my order tonight for a VTF-15H MK2. I suspected as much, in that the TNs should be a bottleneck... Not that I'm hurting in output or extension as you can see from the graphs.

I've attached some Room EQ Wizard plots after EQ, and before EQ showing that subwoofers placed 10' apart can still have great output summation. This is my 2 TN1220HO subs where I put them 16 years ago; one in each back corner of the room. Every room is different and all that, but if you've got dumb-luck like I did, you can see I was getting pretty good real-world in-room response/summation to start with. Yeah, there's some nasty nulls there because the real world sometimes interferes with our plans.

Red line is back left sub, green line is back right sub, blue is both at same time. The subs are gain matched, but I have no delay added as it makes overall response worse by some miracle of placement relative to listening position. I then saw the "natural house curve look" to it, and set a +10dB desired house curve in REW and it generated EQ filters that did what they said they'd do to give the REV 3 EQ graph after I imported the filters into my MiniDSP 2x4HD.

I did gain matching at -25dB, with both subs placed in the same spot in the middle of the room, and adjusted to 85dB. I must have had them placed in a null, or the tones generated by my receiver were at about 48Hz... I may have to use REW to see what the frequency of the subwoofer test tones from my receiver are at frequency wise now that I'm thinking about it.

I'm probably going to get the tape measure out and get the exact dimensions of the room and do some simulations to see where 3 subs gets the flattest response and try positioning subs there. I suspect it'll end up something like front left, back right, and somewhere on a side wall as best options. With only 1 big heavy sub to move (the TN's are featherweights and easy to move), it's not too bad. If I didn't have a fireplace in the front right corner, I'd likely have just done a sub in each corner much to my wallet's dismay.

Anyway, just wanted to say thanks for the advice, and wanted to show proof that even the older HSU subs are still quite potent. Oh yeah, I still want updated TN subs.

[Kevin_Hsu]

Originally Posted by Sorny

All good Kevin, I placed my order tonight for a VTF-15H MK2. I suspected as much, in that the TNs should be a bottleneck... Not that I'm hurting in output or extension as you can see from the graphs.

I've attached some Room EQ Wizard plots after EQ, and before EQ showing that subwoofers placed 10' apart can still have great output summation. This is my 2 TN1220HO subs where I put them 16 years ago; one in each back corner of the room. Every room is different and all that, but if you've got dumb-luck like I did, you can see I was getting pretty good real-world in-room response/summation to start with. Yeah, there's some nasty nulls there because the real world sometimes interferes with our plans.

Red line is back left sub, green line is back right sub, blue is both at same time. The subs are gain matched, but I have no delay added as it makes overall response worse by some miracle of placement relative to listening position. I then saw the "natural house curve look" to it, and set a +10dB desired house curve in REW and it generated EQ filters that did what they said they'd do to give the REV 3 EQ graph after I imported the filters into my MiniDSP 2x4HD.

I did gain matching at -25dB, with both subs placed in the same spot in the middle of the room, and adjusted to 85dB. I must have had them placed in a null, or the tones generated by my receiver were at about 48Hz... I may have to use REW to see what the frequency of the subwoofer test tones from my receiver are at frequency wise now that I'm thinking about it.

I'm probably going to get the tape measure out and get the exact dimensions of the room and do some simulations to see where 3 subs gets the flattest response and try positioning subs there. I suspect it'll end up something like front left, back right, and somewhere on a side wall as best options. With only 1 big heavy sub to move (the TN's are featherweights and easy to move), it's not too bad. If I didn't have a fireplace in the front right corner, I'd likely have just done a sub in each corner much to my wallet's dismay.

Anyway, just wanted to say thanks for the advice, and wanted to show proof that even the older HSU subs are still quite potent. Oh yeah, I still want updated TN subs.

Thank you so much for ordering our VTF-15H Mk2! Can you provide me with the room layout once you get the chance? I'd love to look over it and maybe provide some additional options for placement. So when you changed the speaker distance for both subs it made the response worse? That is interesting.

[Sorny]

Originally Posted by Kevin_Hsu

Thank you so much for ordering our VTF-15H Mk2! Can you provide me with the room layout once you get the chance? I'd love to look over it and maybe provide some additional options for placement. So when you changed the speaker distance for both subs it made the response worse? That is interesting.

I must have been unclear. I meant that changing delays in my miniDSP on either sub made the summed response worse overall. I could impact some nulls positively, but it dropped overall response considerably. I adjusted up to 15ms on either sub, in 1ms increments, but results of any delays to either sub always resulted in worse overall combined response. As one would expect, changing delays to both subs simultaneously had no impact. I didn't do much playing with delaying both subs or playing the distance game in the receiver to impact the crossover integration with the mains. I elected to go for maximum peak summed outpupt, and then EQ the heck out of the peaks to flatten the response.

I've attached a truly fancy MSPaint-special room drawing that is most assuredly not to scale (there's a lot more room behind couch to back wall compared to what it looks like in my crude drawing, and the front of the room is much more closely packed than the drawing indicates). I've really got to get the room measurements. The big X in the bottom left is where I'm thinking of moving sub 2, and placing the new 15'er where sub 2 is located as a start. I can squeeze a TN in that corner behind the AV rack, but not the new VTF. Sub 1 is close to a door that already can rattle pretty bad when fully closed, so I leave it cracked. I was also thinking of maybe putting the TNs at the front 1/4 and 3/4 along front wall, but not sure if having subs that close will cause the gas fireplace to rattle. With subs in back of room, the fireplace doesn't rattle now... The wall with all the right side speakers is open for sub placement, left side speaker wall is spoken for for the most part at front of room, but back half left side walls are fair game. Sub 1 and Sub 2 have been tried every foot from back of couch along rear right/left of room to back corners of room. I've got my SBR/SBL speakers mounted to the wall, and they're actually at the right spot to try 1/4 & 3/4 rear wall placement for subs, but with short ceilings and tall TN subs, I can't have both at same location. I may be open to trying them at the 1/4 & 3/4 rear position and move SBR & SBL onto stands and moving those closer to listening position.

This is a basement room more or less dedicated for A/V shenanigans. Concrete block walls on 3 sides (framed 2x4/sheetrock over them, but all block), except for the back wall with 2x4/sheetrock into about a 10' unfinished utility room. Back wall (right side of drawing) is the 2x4/sheetrock combo; the entry to the A/Vroom is on bottom of drawing and is a landing at bottom of stairs, with utility room door opening not shown either but directly opposite of entry to the A/V room.
I'm running a 7.2.4 ATMOS setup in there, soon to be 7.3.4 in what I'm thinking is about 2200-2300 cubic feet.

Like I said, I need more exact measurements, but I do know I'm about 15' from the back wall at my main listening position, and about 7' from the TV, which is pulled out maybe 4 feet from front wall so as to better match the front speakers. I get supreme imaging out of the fronts pulled way out into the room, and the room does triple duty of music/movies/games, but priority #1 was finding where the Magnepans sounded best and putting the main listening position in that spot. So, what I'm saying is the MLP isn't going to be moving because the Maggies are truly incredible sounding in that spot.

[Kevin_Hsu]

Sorry for the late response! I saw that there was a response but for some odd reason I wasn't able to find it. When you say you are trying to smooth out the response, what aspect would you like to smooth out more do you need more present mid-bass?

[Sorny]

Originally Posted by Kevin_Hsu

Sorry for the late response! I saw that there was a response but for some odd reason I wasn't able to find it. When you say you are trying to smooth out the response, what aspect would you like to smooth out more do you need more present mid-bass?

Not really, I was just wanting more even bass response overall.

I ended up placing a single TN in the front left corner, one in the back right corner, and the VTF-15H Mk2 in the left rear corner of the room for now. I will probably play around with the position of the subs in the rear of the room a bit, but the overall response after time aligning and EQ is pretty darn good now.

I went from ~8.5% THD peak at 17.3Hz with just TN's in rear corners to 2.3% THD at 10Hz peak with 3 subs in their current locations, and under 1% THD from 15hz up. That's at my usual -15dB listening level. I'm VERY happy with that.

I had to turn gains down on the TN's from ~11:30 on the 500W amps to ~10:00, and have gain knob on the VTF at about 08:00. I did run a sweep at reference level, and see ~15% THD at a few spots, but under 10% most of the time in the audible range (at reference, with just TN's It was 30%+). So, I got more extension, flatter response, and lower distortion.

Overall, I'm quite happy. I may boot up my computer into windows (ick), and try Multi-Sub Optimizer and let it run overnight to see what brute force computation can accomplish as far as flattening the in-room response.

All graphs are with no smoothing applied... and the rising response as frequency drops is intentional with a house curve.

For settings on the VTF-15H Mk2, I have it at EQ1, Q 0.7, 1 port open. I did not try any other settings on it. That's a job for another day.

On a side note, the VTF is big, and heavy. It's also quite well built, the satin finish is immaculate, and the grille makes no noise. Hats off to Dr. Hsu for another subwoofer done quite right.

[Kevin_Hsu]

Is the purple in the second graph with all of them time aligned but not EQ'd?

[Sorny]

Originally Posted by Kevin_Hsu

Is the purple in the second graph with all of them time aligned but not EQ'd?

I apologize in advance for yet another super long post...

No. 2nd graph purple is with all 3 subs with no time alignment, inversion, or EQ applied; "as-is" if you will. The green line is after inverting sub 3 (got similar results with subs 1 & 2 both inverted and not inverted on sub 3, but then crossover integration with my mains was poor). The Red line on graph 2 was after time aligning as best I can with my very limited experience. I need to re-read the documentation on how to overlay impulse responses to do less guesswork. I think I'm close because REW listed the combined response as having the same delay as sub 2 by itself, which is the physically closest sub to the MLP. I got somewhat less gain than I expected overall by running 3 vs 2 subs, but did get a healthy increase in output (which means lower distortion since each sub has to work much less).

It struck me as odd that I had to invert phase on the VTF relative to the TNs, when I would have thought sub2 and sub 3 would need inversion relative to sub 1 since sub1 is in front of room and both sub 2 and sub 3 were in back corners of room. I took many more measurements than what is posted, but I chose the highlights, showing what having incorrect inversion and delay can do to response. As you can see from the graphs, my room has some challenges without EQ.

Those graphs are just the initial, lazy setup of throw a sub into an available corner and see what happens...

This setup has 1 TN1220 in the front left corner (only open corner in front of room), 1 TN1220 in back right corner, and the VTF-15H Mk2 in the back left corner of the room. Since I know the back right & front left corners sum together well, and I can't get the VTF into a front corner, I'm probably going to reposition the VTF in the right rear and use the 2nd TN to move around to try to boost the mid-bass suckout above 40Hz and even up the response.

I'm relatively happy with the non-EQ'd response below 40Hz, I just have to fix >40Hz stuff and am hoping moving the current rear TN will do that.

Do you think it would be better to fire the VTF into the wall, leaving 3-4" of space from grille to wall, or tuck the amp into the corner or will it likely not matter much? I suspect it won't make much difference as the wavelengths are so much longer than the length of the subwoofer, but I've found you have to test your assertions, and it almost seems like bass output in a real room only vaguely adheres to theory (or my almost complete lack of understanding said theory).

I also still need to play with port plugs, EQ switch, and Q settings on the VTF-15 as well.

I wish I would have placed a TN up front earlier considering what the low bass response is with a sub there. But, these are things one doesn't know they don't know until they measure it.

[Sorny]

I didn't mess around very much more with the setup, aside from having to retire my Maggies due to a crossover catastrophic failure on the Front Right speaker, so I put my Def Tech's back into service, and since I had to calibrate the speakers, I figured I'd tweak on the subs a bit as well...

I merely changed which port was plugged on the VTF-15, and re-visited the gain matching, and performed a bit more exact time alignment of the subs. The VTF is currently firing along the left wall, and I initially had the port away from the wall open; I plugged that port and unplugged the port closest to the wall. The resulting graph, unsmoothed, is not the best looking I've seen, but it sounds so good I've decided that unless I'm forced to change things, I'm calling it good. I watched a couple movies today, and listened to a bunch of music, and think this will definitely do.

A guy can only obsess so long on setup before it's time to listen instead of measure & tweak things.

I'm running the subs about 7dB hot on the very low end (healthy rising response starting at 120Hz, going to 30Hz), and it just plain sounds great. With the subs spread around the room, there is no localization of bass at all (not that I've ever found localization to be a problem with my HSU subs), the distortion is under 1% at any frequency I can actually hear (It creeps up to about 3% at 10Hz), when played back at my normal -15dB volume level.

I watched "BEQ" versions of 2 of my recent favorite movies for the quality of the sound design; John Wick 3, and Blade Runner 2047. At -15dB main volume for both, they showcased 2 very different flavors of bass. John Wick had chest thump galore on the gunshots, and BR2047 had crushing low and loud bass throughout. At no point in either movie did I ever detect a hint of distress from the subs. I honestly can't say that I could point out the location of the subwoofers if I didn't know where they were if I was blindfolded; lets be honest, it's hard to miss any of them visually as 2 are 4' tall cylinders, and the 3rd is a dorm fridge size box. But close my eyes and I hear bass coming from whatever speaker is supposed to produce it (in the case of John Wick), or just omnipresent as LFE in BR2047.

Listening to music, it's obvious I have subs, or very large speakers, but the bass comes entirely from the front (listening in stereo), despite 2 out of the 3 subs being behind me. Even with the house curve, drums sound tight.

I'm probably going to repair my Maggies' crossovers and set them up in a room upstairs. That's a project for later, as it means new amps, preamp, and sub to get for it... It never ends.

[Sorny]

Been a month with 3 subs and now I'm waiting for sub #4 to show up...

I'll have to recuse myself from giving anyone subwoofer advice, because I think I have a bass problem...

Room is 12'x28'x7' according to my trusty tape measure, so about 2350 cubic feet.

I'm going to be quite honest...

Staying with just my original pair of TN subs would have been the smart thing to do and the best thing for my wallet. They already provided me with better bass than most people will or have ever heard; I'd gotten multiple comments from friends/family about never hearing anything like that before. The Organ Symphony excerpt from the test CD is a crowd pleaser, even for a crowd that likes death metal... Nobody expects what a pipe organ can do on a playback setup that can reproduce it... As to movies? Well, newsflash, subs that do great on pipe organs do great on mvoies.

But, I am part of the lunatic fringe, and when I saw how much worse it measured at seating locations I don't sit in, it bothered me. So, I added a 3rd sub, and got improved seat to seat consistency; I also got enough headroom to run a crazy hot house curve (+12dB, not +7dB as I indicated in a prior post) at my normal listening level maintaining very low distortion levels. Most of the comments from the few who've heard the current setup involve language not fit for a family forum, but the gist is that it's absurd, in a very good way.

I guess I'm adding the 4th because if a little overkill is good, a lot of overkill is more gooder. I expect I'll be running no more of a house curve than I currently do, because right now drums still sound correct. Recordings with "punchy" kick drums that kick you in the chest, do kick you in the chest; recordings that don't have it, don't.

Now for the long wait... Then the room re-arranging, then measurements, adding EQ, more measurements, and then the payoff. Listening.

[Kevin_Hsu]

Thank you so much Sorny! The thing that's great about all of this is that you built up quite a bit of experience in integrating various subs within the room. Are you going to put TN's in the back and the 15H's in the front in that room? I love the Saint-Saens track! I use it all the time to showcase what the various port configurations do. Shame I wasn't able to hear that in person.

[Sorny]

Originally Posted by Kevin_Hsu

Thank you so much Sorny! The thing that's great about all of this is that you built up quite a bit of experience in integrating various subs within the room. Are you going to put TN's in the back and the 15H's in the front in that room? I love the Saint-Saens track! I use it all the time to showcase what the various port configurations do. Shame I wasn't able to hear that in person.

Going to try TN's at 1/4 & 3/4 positions up front, and VTF's along rear wall at 1/4 & 3/4 positions to start with. TN's are easier to tuck behind the TV stand.

[Sorny]

Got room all re-arranged. TN's up front at 1/4 & 3/4 positions, and VTF's on rear wall at 1/4 & 3/4 positions.

I mislabeled the 4 sub graph... but one look and you'll be able to see the results of each sub and the result of all 4 subs after time alignment.

THD is under 2% at my normal listening level at 10Hz, under 1% above 11Hz, and under 0.5% above 20Hz when running sweeps at -15dB on the master volume.

I have no idea what THD is at reference level because my Umik-1 clips to the point it's not reliable by 14Hz on a sweep at 0dB master volume.

Of course there's room for further improvement, and I'm sure I could re-position subs even more, but I don't really think the juice is worth the squeeze considering where it's at now.