Sierra-2 Bass, Subwoofers, Acoustical Treatment

[cubusmybro]

Hey guys. Even though I've been a forum member for seven years, this is my first post!

In about four years, I'll be building a dedicated music listening room. My endgame will be Sierra RAAL Towers with dual Rhythmik subwoofers, proper room treatment, etc., etc., but for now, I am a proud Sierra-2 owner in a simple small room.

Over the next four years, I will be moving various times and will mostly be listening in smaller rooms. Currently, my system is struggling with the low end. Without a subwoofer, the Sierra-2s do not have sufficient bass output in my room for music. With my HSU Research STF-1 subwoofer (8-inch), the bass often becomes boomy.

Since I'll move a few times over the next four years, if I spent around $500 to even out the low end, where would my $500 be best spent? Acoustical treatment? Another STF-1? A different sub, like the Rhythmik L12?

Appreciate any answers. The Sierras sound excellent running by themselves, but when I try to fill out any bass, I always run into this boomy issue.

[Bruce Watson]

Have you tried the Sierra-2's without any sub? Mine sound great without a sub as long as I'm listening to music that doesn't go too deep. For example, a sub wouldn't get used much listening to a string quartet. But if it's techno dance music, you're going to want a sub for sure.

That said, servo subs typically do a much better job of reducing "boominess" and integrating well with your mains, compared to non-servo subs. If you're only going to listen to music and not do any HT, a sealed sub like a Rythmik L12 would be a good choice. If you can swing a pair, you can get better control of room modes, which is a problem in any small room. But you can always add a second one later.

Thing is, you can try it and see how you like it. If you don't like it, send it back. I think Rythmik gives you like 45 days of in-home trial.

Personally, I do more HT than music, so the subs I use with my Sierra-2 mains are a pair of Rythmik LVX12s. They do surprisingly well with music. And the integration with the Sierra-2s was just scary for me -- the subs completely disappear and all I get is the Sierra-2 sound ruler flat down to around 16 Hz (does a mean pipe organ). Those bottom two octaves just sound like the Sierra-2s are effortlessly playing them.

I'm just sayin' if it works that well with the LVX12s, I would imagine that it would work even better with an L12.

[N Boros]

If it were me and I knew that I would be moving around quite a bit, I might wait on a subwoofer. It would be too bad to get subs that are too small, when you end up in a more permanent place. You could avoid this issue by just getting huge ported models with lots of output, but then you are trying to move them from one place to the next and as you say they will go in small rooms.

I too have the Sierra 2s as my main, but an Outlaw LFM1, which was also designed by Hsu. The subwoofer is about 15 years old and I am really itching to get a pair of Rythmiks that better keep up with the Sierra 2s in terms of transient response and have more extension and output capabilities. I too have noticed that if I set an 80 Hz crossover that the bass is a bit sloppy in comparison to setting it between 40 to 60 Hz. You might try different placement, if you haven't played around with different locations and then a lower crossover. Maybe you will be okay with it for the next few years, until you settle on something more permanent.

For me I primarily do HT more than music, like Bruce. So I need the extra output from a subwoofer from 40 to 60 Hz and so end up switching back to an 80 Hz crossover when I watch movies that I know will have lots of LFE. I get tired of switching back and forth on the crossover, so I usually just have it at 80 Hz and live with the sloppy bass. Hopefully just another year or two for me before I can get a pair of Rythmiks.

[cubusmybro]

I am considering upgrading the subwoofer, but still, I do not want to buy something like an L12 and one day have to upgrade again to an even bigger, more musical subwoofer. My HSU-STF1 has a lot of output if placed in a corner, but the corner gives more volume but less quality.

I've done something fairly controversial by raising my subwoofer to ear height and placing it closer to the center of my room. The volume output from the subwoofer has decreased, but the quality of the output has dramatically increased and all the bass-boominess I had been suffering from has essentially disappeared.

Still, I'm wondering if quality acoustical paneling placed in corners may allow me to have a more normal subwoofer position. I was thinking about something such as this:

https://www.acoustimac.com/dmd-bt4000-bass-traps-48x24x4-g (https://www.acoustimac.com/dmd-bt4000-bass-traps-48x24x4-]g)

How much of a difference would upgrading from an STF-1 to an L12 make? And can anybody comment if there is any real musical difference between an L12 and an F12, especially if I am running dual L12s or dual F12s?

Thank you all again.

[white_darren]

The boominess is primarily going to be a room integration issue and is pretty common with corner loaded subs. Knowing that you're going to be moving around a lot, I'd focus on solving the room integration and worry about upgrading subs when you settle into a more permanent listening space.

FYI, I also raised my E15HP up off the floor to resolve my boominess issues. My listening area is far from from ideal as it has lots of hard, reflective surfaces (tile floors, lots of glass, etc) and the reflections off the floor were the cause of my boominess. It doesn't get discussed much but I'd argue that vertical placement is just as important as horizontal placement, it's just a little more difficult to raise a big, heavy sub up off the floor and make it blend into the room decor....

[jjackkrash]

My personal opinion is sell the sub you have for whatever you can get and get the biggest ported Rhythmik sub you can afford. If you can up the budget, do that. When it comes time to move, just stick it in the moving van with everything else and move it. Skimping on subs compromises the whole system, especially when it comes to the HT experience.

[bkdc]

My philosophy on subs is different since I'm 70% music, and my 45 year old body hates moving 100 pound subs. Room integration is far easier with multiple subs. I'd rather own three 60-pound subs than one 100-pound sub to avoid injury and the hassle of asking for a second hand. This costs more money but that's how much I value my back. :) Since I know I will be using more than one sealed sub (eventually), I'd start with one sealed sub and then add additional identical subs as the space demands. I have two F12's, and I'm contemplating on adding a third F12.

[N Boros]

My philosophy on subs is different since I'm 70% music, and my 45 year old body hates moving 100 pound subs. Room integration is far easier with multiple subs. I'd rather own three 60-pound subs than one 100-pound sub to avoid injury and the hassle of asking for a second hand. This costs more money but that's how much I value my back. :) Since I know I will be using more than one sealed sub (eventually), I'd start with one sealed sub and then add additional identical subs as the space demands. I have two F12's, and I'm contemplating on adding a third F12.

In a sealed rectangular room, going with 3 subs over 2 is actually worse in terms of reduction of standing waves. In room that is not sealed and rectangular, 3 subs can give a better reduction of standing waves, but figuring out the placement and delays to do so can be quite tricky. The nice thing about two subs is that if you are in a sealed rectangular room, then you know that the midpoints of opposing walls is the optimal location. So you just get the levels to match your speakers, do some EQing and you are done. If you room is not sealed and rectangular, then you could get a receiver with the highest level of Audyssey, and just place them across the room from one another and run Audyssey to allow it to dial in the delay to reduce the standing waves as much as possible. Again, with 3 subs you are kind of on your own doing lots and lots of measurements.

[Beave]

In a sealed rectangular room, going with 3 subs over 2 is actually worse in terms of reduction of standing waves. In room that is not sealed and rectangular, 3 subs can give a better reduction of standing waves, but figuring out the placement and delays to do so can be quite tricky. The nice thing about two subs is that if you are in a sealed rectangular room, then you know that the midpoints of opposing walls is the optimal location. So you just get the levels to match your speakers, do some EQing and you are done. If you room is not sealed and rectangular, then you could get a receiver with the highest level of Audyssey, and just place them across the room from one another and run Audyssey to allow it to dial in the delay to reduce the standing waves as much as possible. Again, with 3 subs you are kind of on your own doing lots and lots of measurements.

Optimal in what sense? In terms of response smoothness?

Do you have a link that explains this in greater detail?

I've seen analysis that recommends corner placement instead of midwall placement. According to the analysis (was it Welti?), corner placement has better efficiency with only minimal reduction in response smoothness.

[jjackkrash]

I've seen analysis that recommends corner placement instead of midwall placement. According to the analysis (was it Welti?), corner placement has better efficiency with only minimal reduction in response smoothness.

Dr. Toole was discussing this very thing in a thread on AVS and also indicated that corner placement has much better efficiency with only minimal reduction in response smoothness, even though midwall placement generally does get you the smoothest response.

[Beave]

Here's a link to Welti's paper:

https://www.harman.com/sites/default/files/multsubs_0.pdf

[N Boros]

Optimal in what sense? In terms of response smoothness?

Do you have a link that explains this in greater detail?

I've seen analysis that recommends corner placement instead of midwall placement. According to the analysis (was it Welti?), corner placement has better efficiency with only minimal reduction in response smoothness.

Yes, it was Todd Welti's research:

https://www.harman.com/sites/default/files/multsubs_0.pdf

Basically he ran computer simulations (using Matlab) to see what would happen as you increase the number of subwoofers in a sealed rectangular room. He was assuming that you place the subs all at floor level and they are all placed in reasonable locations. What he was trying to measure along the way is how the standing waves in the room will be reduced with either placement or an increase in the number of subwoofers. The way that he measured the standing waves was by looking at the Max Minus Min, Max Minus Average and Standard Deviation all in dB's over multiple seats. As these figures get smaller the standing waves in those seats get reduced and your bass is more even from one seat to the next.

Basically what he did with one subwoofer was run the simulation for the sub in one location and then slowly move it around and then pick out the location that was optimal (in reducing the standing waves over multiple seats using the three different ways of measuring it). Then he did it for two subwoofers, three subwoofers and four subwoofers. In the attached plot you will see the effects of the standing waves in the seats as you go from 1 sub to 2 to 3 to 4 (here https://drive.google.com/drive/folders/1cvnALVdL_5INHdGMQcCRAGj-HnQ_5MJb?usp=sharing ). Surprisingly, either 2 or 4 subwoofers is best and 2 subs is actually really close to what you get with 4 subs, at half the cost (because in most cases one should be using identical subs).

Afterwards, he also did actual in room measurements of some of the positions to compare with that of the simulations that he ran to determine how close the two were. It turned out that they were actually quite close, so you can look at either the in room measurements or the simulations with confidence that they are both accurate. To sum up he found that either placing 2 subs at the midpoint of opposing walls or 4 subs at the midpoints of opposing walls was best. Going from 2 to 4 was only slightly better. He also suggested as an alternative to 4 subs at the midpoint of each wall, to place them all in a separate corner. This gives up a slight bit of the reduction in the standing waves (close to that of 2 subs at the midpoint of opposing walls), but gives you a lot more output. See the other attached figure for figures of these configurations ( https://drive.google.com/drive/folders/1cvnALVdL_5INHdGMQcCRAGj-HnQ_5MJb?usp=sharing ). Again, you can keep adding more and more subwoofers and you might reduce the standing waves a slight bit more, but it really doesn't make sense with the extra additional cost.

[N Boros]

Dr. Toole was discussing this very thing in a thread on AVS and also indicated that corner placement has much better efficiency with only minimal reduction in response smoothness, even though midwall placement generally does get you the smoothest response.

Pulling figures from the Welti paper (here https://drive.google.com/drive/folders/1b76DYW0brOOtWCaN7I2yCPGhFgGPKfRR?usp=sharing ), I guess I disagree. The midpoint of opposing wall placement has a Standard Deviation of about 1.3 dB, Max Minus Min of 4.6 dB and a Max Minus Average of 2.3 dB. Going with the opposing corner placement has a Standard Deviation of about 2.6 dB, Max Minus Min of 13.1 dB and a Max Minus Average of 5.6 dB. That seems pretty big to me. But, maybe his idea of minimal is different than mine. Or more likely, maybe I don't have the context of what he was saying.

If Dr. Toole was referring to configuration number 4 from pages 19 and 20 of the paper, where the subs in the front to corners of the room, then things get even worse. This configuration would have a Standard Deviation of about 4 dB, Max Minus Min of 21 dB and a Max Minus Average of 7 dB. If it were me, I would stick with the midpoint of opposing walls, if at all possible. It's not the end of the world if that isn't possible, but it does seem drastically better than either of the corner placement configurations mentioned.