2 Subs (Rhythmik L12) Response Worse Than 1 (Hsu VTF-2 Mk5)

[CoolHandDuke]

Well I have both. The L12 is my bedroom sub.

I have dual VTF2mk5 in my living room. There is no comparison vs L12 sealed. It’s sealed so it can’t compete with ported.

The VTF2mk5 also is noticeably more mid bass than my LVX12 in my small theater room. If WAF ever strikes in the living room, I would happily have the dual VTF2 mk5 in my theater room.

I do appreciate the feedback, but I'm aware of the limitations in both volume and extension. I'm just concerned over smooth response. 95%of my listening is music, and I went with the L12 based on what seemed like great reviews for that function. I will miss the chest slam of 17hz during the occasional movie, but am fine with duals if it makes wife happy. That said, I need to sort out positioning and response or the Rhythmiks go back and I eat shipping. Damn.

 

[ryanosaur]

95%of my listening is music, and I went with the L12 based on what seemed like great reviews for that function.

Nooooooooooooooooooooooooo!



This whole music vs HT thing is a myth that needs to die.

Sure, maybe 20 years ago, it may have held some merit to suggest such a thing. Today’s ported Subs work well enough that it is safe to call this myth, now.

I do hope you can get these working, please don’t get me wrong.

 

[CoolHandDuke]

Nooooooooooooooooooooooooo!



This whole music vs HT thing is a myth that needs to die.

Sure, maybe 20 years ago, it may have held some merit to suggest such a thing. Today’s ported Subs work well enough that it is safe to call this myth, now.

I do hope you can get these working, please don’t get me wrong.

Sorry. I wasn't inferring sealed is better for music. Just that if I was going with sealed (to appease the wife), then Rhythmik was well regarded in that respect. With my Hsu, I dampen to 0.3 for music and really like the results.

 

[CoolHandDuke]

I have two L12's as well (I eventually added an F18 to get real low end power) but the link in my sig has more info on the results I was able to achieve with them. Let me know if there's other help we can provide.

To answer your question on XT32 I'm not sure how good a job it does with phase but it does delay for sure. I ended up adding a miniDSP when I got the third sub and I made a huge different with phase and delay on that. When I just had the two L12s I did try playing with phase on one sub at a time but never got much of a change - the dial only gives so fine of an adjustment and I wasn't great at experimenting with it.

All that said REW and a good calibrated mic were a huge help in getting real before and after measurements -the 'after' in the audyssey app is calculated so it's essentially made up. you might be getting a better end result and not even know it.

So I took some REW measurements when I got home. I started by finding the ideal placement for the sub between my mains. It gave an excellent response on its own (I've attached measurements). I then independently found a spot (left side of room) with decent response. These locations were the same ideal spots I had my Hsu in before.

As soon as I take a measurement with the 2 subs together, I see the hole 60-80hz. I tried moving the "2nd" sub all over the room. Really no matter where I took it, I still got the same hole. I played with phase on the closer sub, but saw no changes. Really discouraging. That initial measurement of the 1 sub is really damn good IMO. I just don't understand why a second one is ruining the response so much.

Any suggestions are appreciated. Apolgoies for the rant. I'm burnt out from Covid testing and hospital work and my patience isn't what it usually is.

Edit: The blue line in the "both subs" graph is the measurement from the single front sub just to compare the response of 2 to 1.

 

[nathan_h]

Two subs CAN make seat to seat variation less of a problem. Two subs can create a consistent bass response across multiple seats.

Note that I didn't say they would make a flat, linear or smooth response. They often won't.

BUT, once you get consistent bass across your mains seats, THEN system EQ can tamp down the peaks in response. (Fixing nulls is hard and less likely to be achievable with EQ.)

So, the goal with two subs is NOT to figure out where one measures best alone and the other measures best alone. It is to figure out when WHEN PLAYED TOGETHER they create the fewest dips in the listening area, and the least variation across the listening seats.

THEN, EQ can flatten the peaks.

---

Sounds like a lot of work? Yeah, it feels that way, especially in a non rectanguler, non sealed room.

In fact, I went down the rabbit hole of getting dual subs 15 years ago......and sent one back after a couple weeks. The science and knowledge of how to get them working well in an unusual room just wasn't well known at the time. All the research by Welti, and other folks, about bass in small rooms was just begining to get published. Tools like REW, MSO, and miniDSP were mostly just ideas that hadn't been implemented yet. Gedde's research and ideas weren't common knowledge.

---

Anyway, I am going to say it again: Two sub SELDOM deliver linear response on their own. There are a few edge cases in rectangular rooms with specific placement of the subs and listener where they can. But that's rare and NOT the goal.

The goal is CONSISTENT response (may be very non linear) across your main listening area. That's the big thing that dual subs can achieve.

Moving them around and the phase adjustment, can let you choose from among different NON LINEAR response curves the curve that has the fewest dips. That is ideal.

THEN, EQ can effectively smash the peaks.

---

As far as I know, no automated room correction system can really set up dual subs correctly yet. That is why people still resort to using a miniDSP. Or, at the very least, adjusting the PHASE on ONE of the subs.

Here is the easiest approach. Not precise, but good: http://www.avrant.com/a-12-step-guide-to-setting-up-dual-subwoofers/

If you want to go down the rabbit hole on why this is, you can watch this video and follow the links (http://www.avrant.com/av-rant-737-interview-with-todd-welti-on-subwoofers/#more-4107) but that is not necessary for actually solving things. Rather, that is an explanation of why.

In your room and in your case, if you are willing to add a miniDSP, you might find this guy the easiest to follow.

 

[CoolHandDuke]

Two subs CAN make seat to seat variation less of a problem. Two subs can create a consistent bass response across multiple seats.

Note that I didn't say they would make a flat, linear or smooth response. They often won't.

BUT, once you get consistent bass across your mains seats, THEN system EQ can tamp down the peaks in response. (Fixing nulls is hard and less likely to be achievable with EQ.)

So, the goal with two subs is NOT to figure out where one measures best alone and the other measures best alone. It is to figure out when WHEN PLAYED TOGETHER they create the fewest dips in the listening area, and the least variation across the listening seats.

THEN, EQ can flatten the peaks.

---

Sounds like a lot of work? Yeah, it feels that way, especially in a non rectanguler, non sealed room.

In fact, I went down the rabbit hole of getting dual subs 15 years ago......and sent one back after a couple weeks. The science and knowledge of how to get them working well in an unusual room just wasn't well known at the time. All the research by Welti, and other folks, about bass in small rooms was just begining to get published. Tools like REW, MSO, and miniDSP were mostly just ideas that hadn't been implemented yet. Gedde's research and ideas weren't common knowledge.

---

Anyway, I am going to say it again: Two sub SELDOM deliver linear response on their own. There are a few edge cases in rectangular rooms with specific placement of the subs and listener where they can. But that's rare and NOT the goal.

The goal is CONSISTENT response (may be very non linear) across your main listening area. That's the big thing that dual subs can achieve.

Moving them around and the phase adjustment, can let you choose from among different NON LINEAR response curves the curve that has the fewest dips. That is ideal.

THEN, EQ can effectively smash the peaks.

---

As far as I know, no automated room correction system can really set up dual subs correctly yet. That is why people still resort to using a miniDSP. Or, at the very least, adjusting the PHASE on ONE of the subs.

Here is the easiest approach. Not precise, but good: http://www.avrant.com/a-12-step-guide-to-setting-up-dual-subwoofers/

If you want to go down the rabbit hole on why this is, you can watch this video and follow the links (http://www.avrant.com/av-rant-737-interview-with-todd-welti-on-subwoofers/#more-4107) but that is not necessary for actually solving things. Rather, that is an explanation of why.

In your room and in your case, if you are willing to add a miniDSP, you might find this guy the easiest to follow.

Thank you for the resources and for the explanation. While I did not expect a magic bullet using 2 subs, perhaps my expectations were too high. If I was seeing more peaks, I wouldn't be as concerned as I am, but I know the nulls aren't going to get dealt with by Audyssey. I'm sure the response in the room (as a whole) is better with 2, but I don't want to sacrifice that linear response I get using one. Obviously not what I expected when I pulled the trigger on these.

 

[Pogre]

Are those sweeps just your subs by themselves? What do your sweeps look like with your main speakers and subs together? When I had a dip close to the same region I found a higher crossover helped things out. In your case maybe try a lower crossover as well and see if there are any improvement. End of the day speakers + subs is how you listen to your system so that's where you want it to be the most linear.

This stuff isn't simple, as you can see. I've spent many hours dialing my bass in and I'm still learning things.

 

[CoolHandDuke]

Are those sweeps just your subs by themselves? What do your sweeps look like with your main speakers and subs together? When I had a dip close to the same region I found a higher crossover helped things out. In your case maybe try a lower crossover as well and see if there are any improvement. End of the day speakers + subs is how you listen to your system so that's where you want it to be the most linear.

This stuff isn't simple, as you can see. I've spent many hours dialing my bass in and I'm still learning things.

Thanks, Pogre. Those measurements are subs alone. Today is my day off, so I'll experiment a bit to see if anything changes and report back.

 

[William Lemmerhirt]

Definitely measure with the mains and subs. But before that...
You found the sweet spot for one. Now instead of finding the sweet spot for the second one, leave the first one on. Then sweep and move. Sweep and move etc. if you get close to good, try moving the phase on the second one. See if it helps. After you get smooth, sweep with the mains. If you have a Xo dip, then add a couple feet to the distance in the AVR. See what it does. Delay and phase are the same thing, so that’s a good way to integrate. Pogre mentioned raising the XO too. That is also with a try. These guys have you covered so that’s all I got...

 

[CoolHandDuke]

Definitely measure with the mains and subs. But before that...
You found the sweet spot for one. Now instead of finding the sweet spot for the second one, leave the first one on. Then sweep and move. Sweep and move etc. if you get close to good, try moving the phase on the second one. See if it helps. After you get smooth, sweep with the mains. If you have a Xo dip, then add a couple feet to the distance in the AVR. See what it does. Delay and phase are the same thing, so that’s a good way to integrate. Pogre mentioned raising the XO too. That is also with a try. These guys have you covered so that’s all I got...

Thanks. This is the approach I'll try. I was also recommended to look at the phase alignment tool on REW so I'll play around with that as well.

 

[CoolHandDuke]

Did a ton of measurements today. Can't escape a null no matter where I place them. Some better than others, but still not as good as one sub in my MLP.

 

[shadyJ]

Did a ton of measurements today. Can't escape a null no matter where I place them. Some better than others, but still not as good as one sub in my MLP.

That is strange. You are getting some kind of phase conflict between the subs. You did try changing the phase values, right? Change the phase of one of the subs by 180 degrees to see what happens.

 

[CoolHandDuke]

That is strange. You are getting some kind of phase conflict between the subs. You did try changing the phase values, right? Change the phase of one of the subs by 180 degrees to see what happens.

I did. Changing the phase on the closer sub doesn't seem to do anything. I'm not sure what it's doing, if anything at all. I don't know if there's anything wrong. Changing distances in avr does make a difference. It still doesn't solve the issue though and the distances I'm inputting are very inaccurate compared to their actual distances.

 

[shadyJ]

I did. Changing the phase on the closer sub doesn't seem to do anything. I'm not sure what it's doing, if anything at all. I don't know if there's anything wrong. Changing distances in avr does make a difference. It still doesn't solve the issue though and the distances I'm inputting are very inaccurate compared to their actual distances.

Hmm, that is odd. It's very strange to see that two subs get you a worse response than one. The only reason that I can think of for that is a phase conflict, but you say that changing the phase does nothing. I wonder how something like Audyssey XT32 or Dirac Sub Control would handle this? The only thing I can think of to try at this point would be to change the physical positions of the subwoofers to see what that does.

 

[CoolHandDuke]

Hmm, that is odd. It's very strange to see that two subs get you a worse response than one. The only reason that I can think of for that is a phase conflict, but you say that changing the phase does nothing. I wonder how something like Audyssey XT32 or Dirac Sub Control would handle this? The only thing I can think of to try at this point would be to change the physical positions of the subwoofers to see what that does.

XT32 does take the peaks but makes little difference for my nulls. I'm also confused why I don't see a difference in measurements when physically changing phase knob on the sub. Seriously considering shipping them back and sticking with one after this experience.

 

[AcuDefTechGuy]

Are you using the Audyssey app?

 

[CoolHandDuke]

Are you using the Audyssey app?

XT32. Using REW before and after. I am using the app. However, that's not going to fix the nulls even if I manually try to boost them.