Lavoce SSF153.00 15" based dual opposed subwoofer project

[glideslope]

Now let's see those measurements!
All measurement were done in the MLP

Sub with zero correction:
View attachment 342025

Sub crossed with mains at 80Hz, 24dB/octave, min. phase (using Jriver's DSP)

View attachment 342026

Dip appeared at 90Hz

Now let's see what Dirac could do with the situation:

View attachment 342027

Dip at 90Hz remained - I guess I will play around with the crossover (potentially trying linear phase too) to see if I can further remediate that
For the time being I am fine with these results

Let's see the Group delay:

View attachment 342028

Pretty good down to 26Hz or so

Waterfall (set to 400ms)

View attachment 342029

I might try some notch filters to fight those resonances later on - but again, I think this is not too bad

Spectrogram:

View attachment 342030

There is a 10ms peak energy time delay - I have seen many system with subs with way worse results

Distortion (%):

View attachment 342031

There is one peak at around 30Hz, other than that I am happy

Distortion (SPL):

View attachment 342033

Overall, I am pretty happy with these results
I am now fiddling around with setting a low shelf ('target curve') to taste - that will take days or even weeks

Further next steps:
- Once the shock absorber feet arrive in the coming days I will listen and measure if they make any difference at all
- Continuous fine-tuning of the low-end + considering the notch filters

At this point I think this beast is a keeper - in that case I will also need to fix the aesthetics as mentioned in post #3
Note: I consider the above results especially great if I take into account the fact that the whole thing cost me less than 500 EUR....

I calculate that you should have a baffle step at 45.5Hz, and there it is clear as day. Due to the cabinetry beside the sub enclosure. I think above that there is some cardioid thing happening and interaction with the front and side walls.

Would you consider losing the side cabinetry and the TV. Rotate the sub enclosure 90° so the MDF faces forward. It should run omnidirectional until 101Hz. Still cross it at 80Hz. See how that measures.

You can always wall mount the TV on an articulating bracket that will let you swivel left to center it (due to the window).

 

[neRok]

I calculate that you should have a baffle step at 45.5Hz, and there it is clear as day. Due to the cabinetry beside the sub enclosure.

How did you work this out (as in, what is the equation)?

 

[glideslope]

How did you work this out (as in, what is the equation)?

It's just a quarter wavelength distance around the cabinets, cone-to-cone. At which point it becomes bi-directional.

 

[ppataki]

And finally the aesthetics are in place too!

Overall I am extremely happy with this project, one of the bests I have done so far
I can strongly recommend the Lavoce drivers, mind-blowing price/value ratio!

I consider this project finished now

 

[Wolf]

I would have flipped the polarity on the mains and seen if the dip at 90Hz went away. Usually a 180° change is all it takes, and requires less group delay to become a factor than your active filtering.

I also would tend to agree that the bass response will be cardioid in nature due to placement. If you were to make it face side to side with a small slot loading the drivers between cabinets, say 3-4", you'd have a 3 piece setup with no drivers showing through that patterned face. Your response would likely be easier/better to deal with too.

I hate the ringing nature of plywood, and have to damp and mass load the snot out of it to make it go away. I prefer the damping qualities of MDF.

 

[Keith_W]

I hate the ringing nature of plywood, and have to damp and mass load the snot out of it to make it go away. I prefer the damping qualities of MDF.

The video in post #7 seems to indicate that plywood has better damping properties than MDF.

 

[Wolf]

After working with it in acoustic projects, I would tend to disagree. The ply panels are stronger, but also can survive flexure. While MDF may be more porous and need sealing more than ply does, I find it to be better damped, weigh more as in mass loading, and be stiffer than standard plywoods. Baltic Birch is stiffer than MDF, but still does not weigh as much and tends to ring more readily than MDF.

I used standard poplar ply in a short tower build a couple years ago, and I was only able to nuke the ringing by gluing/applying 4" marble tiles alternated with mass loaded Sonic Barrier and reinforced bracing in the corners. I don't have to go to that length to make MDF cabinets satisfactory for speaker builds.

Of note, I do apply epoxy resins to both materials a lot of the time. This is even with that application.

 

[ppataki]

I would have flipped the polarity on the mains and seen if the dip at 90Hz went away. Usually a 180° change is all it takes, and requires less group delay to become a factor than your active filtering.

I tried that yesterday evening, a huge peak has appeared + two more dips that were not there before
The group delay and the spectrogram curves became much worse too (even after correcting the FR)

I am happy with the sound (and the curves) using the crossover techniques I described in post #20
I keep switching between linear phase and minimum phase modes, depending on my mood

 

[glideslope]

Curious if you have tried no furniture cabinets beside the sub? I was asking this previously because I think with those furniture cabinets it is effectively one giant baffle with the drivers several meters apart. There's WAF and then there's the physics of it.

 

[ppataki]

Curious if you have tried no furniture cabinets beside the sub? I was asking this previously because I think with those furniture cabinets it is effectively one giant baffle with the drivers several meters apart. There's WAF and then there's the physics of it.

No, unfortunately this is not an option.....

 

[witwald]

- I have not yet calibrated it (only volume correction and a Linkwitz Transform filter) but it definitely sounds promising

@ppataki Would you be able to share the settings that you used for the Linkwitz Transform filter? I am curious about how much EQ it is providing for the closed-box woofers.

 

[ppataki]

@ppataki Would you be able to share the settings that you used for the Linkwitz Transform filter? I am curious about how much EQ it is providing for the closed-box woofers.

These were the settings I used:

Note that the LT filter was used only to listen to how the speaker sounds before calibrating it with Dirac
I don't use LT filters otherwise

In order to set the low end to taste I always use a linear phase low shelf filter (with settings: Freq=75Hz, Q=1, Gain is up to taste, currently it is +9dB for both my systems)
I leave the target curve flat in Dirac then I apply the above filter post-Dirac in the signal path (and also a high shelf, similarly, to taste)

 

[witwald]

Thanks for sharing the LT filter's settings, and I understand that it was only used for some preliminary testing.

I've plugged them into VituixCAD and I get the following filter gain response function. This is adding 12dB of boost at 40Hz, and almost 19dB of boost at 20Hz.

 

[ppataki]

Thanks for sharing the LT filter's settings, and I understand that it was only used for some preliminary testing.

I've plugged them into VituixCAD and I get the following filter gain response function. This is adding 12dB of boost at 40Hz, and almost 19dB of boost at 20Hz.

View attachment 405836

This is the reason I never use LT filters - if I add my room gain into the picture they quickly become an overkill
I am better off with a normal low shelf (and since I use a linear phase one, there is no impact on phase, group delay, etc.)

 

[jamescarter1982]

didn't read in the thread but could have missed it , are the drivers mechanically coupled together at the magnets? I was under the impression this was required to gain the force cancling benefits of the dual opposed subwoofers . thanks asking as I have something like this in the planning stages

 

[ppataki]

didn't read in the thread but could have missed it , are the drivers mechanically coupled together at the magnets? I was under the impression this was required to gain the force cancling benefits of the dual opposed subwoofers . thanks asking as I have something like this in the planning stages

I am not aware of that, I have not done it with any of my DOS projects (and still there is negligible to no vibration)
I would let others comment on it; might be a good idea nevertheless

 

[witwald]

...are the drivers mechanically coupled together at the magnets? I was under the impression this was required to gain the force cancling benefits of the dual opposed subwoofers.

The force generated by the woofer cone motion of one of the horizontally opposed woofers is transmitted from the woofer basket to the baffle on which that woofer is mounted. That force is then distributed over the entire edge of the baffle and transmitted as a distributed force into the left, right, top, and bottom panels of the enclosure. The second woofer on the opposite baffle is doing exactly the same thing, and the distributed force is identical in magnitude but opposite in direction. Hence, we still achieve force cancellation even without coupling the woofers.

 

[jamescarter1982]

I am excited to share my next project here!
After converting my MCLAs to a sub I have decided to look for a more traditional approach to subs - hence the below project came to my mind
I have designed and built several dual opposed subwoofers (DOS) already - I can say I really love this design

This time I am going to use two Lavoce SSF153.00 (4 ohm version) 15" drivers - they shall arrive early next week
I will put them in a sealed cabinet using 18mm MDF with a size of 630 x 450 x 400 mm

View attachment 340548

I will use a Sabaj A30A full digital amp to drive them with an approx. max power of 450W which will yield 105dB SPL at 1 meter at 24Hz

View attachment 340549

At around 70% of the xmax of this driver:
(so I expect low distortion)

View attachment 340550

Group delay:

View attachment 340552

I am planning to cross the sub at 80Hz with my main system in the living room
The sub will be placed in the front in-between the Ikea Besta storage units (they actually hold all my gear including the PC and the audio stuff)

Build will start this week or latest next week, stay tuned!

hi Reading through this as it was linked In another thread . which programmes are you using here to calculate extension etc please

 

[ppataki]

which programmes are you using here to calculate extension etc please

Can you please clarify? Not sure I fully understand the question, thank you

If you mean the simulation software, that is BassBox Pro 6

 

[jamescarter1982]

that is what I meant ,thankyou .
merry Xmas!!