Another "build a pair of subs" thread

MaxeII

Active Member
I'm edging closer to building the subs, but would like to know if I should go with a Behringer NXD amp or consider a MiniDSP 2x4 HD with a Behringer NX amp.
The subwoofers will be equidistant from the MLP and I don't intend to use an boost at all. So would the 2x4 HD offer any benefits for me over the DSP of the Behringer?
 

scartlead

Active Member
Get both ;) utilising the minidsp for BEQ is brilliant.

 

MaxeII

Active Member
Get both ;) utilising the minidsp for BEQ is brilliant.

Not sure how I haven't seen that before. I must be blind.

So does this BEQ thing break my rule number 1? (no boosting)
 

Conrad

Moderator
It's related to the content, not your response. So yes, it boosts the signal, but it's not boosting it to change your in room response, it's boosting it to recover the filtered content in the source.

You apply the BEQ filters to the input of the minidsp which affects the incoming signal, that's then passed through to the outputs which is where your room correction sits. Those filters (the output ones) would still not have boosting in.

Just be sure not to watch content that doesn't match the loaded filter. ezBEQ makes that super easy though.
 

MaxeII

Active Member
It's related to the content, not your response. So yes, it boosts the signal, but it's not boosting it to change your in room response, it's boosting it to recover the filtered content in the source.

You apply the BEQ filters to the input of the minidsp which affects the incoming signal, that's then passed through to the outputs which is where your room correction sits. Those filters (the output ones) would still not have boosting in.

Just be sure not to watch content that doesn't match the loaded filter. ezBEQ makes that super easy though.
I'm quite impressed by the concept of this. Again, not sure how I haven't seen it before.

Can this be done with the new Arcam AVR's or the JBL SDP-55 without needing a MiniDSP?
 
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MaxeII

Active Member
Pictured here, the inner dimensions are 460mm wide, 420mm high and 320mm deep.
This is the 12mm inner wall, but I'm also adding an 18mm outer wall.
The front baffle will be 3 layers, 18mm plus 2x 12mm.
So hopefully quite solid, but is this good enough for bracing?
 

Attachments

  • Bracing.jpg
    Bracing.jpg
    140.1 KB · Views: 19

IWC Dopplel

Distinguished Member
I don’t know if it’s good enough for bracing but I’d think more about how you can pin the panel centres, without consuming too much volume. I see quite a number of small subs with profiled MDF that stiffen by pinning panels together. It will be stiffer with them in place, but quite a lot of volume for the level of stiffening ?
 

MaxeII

Active Member
I'm guessing that
I don’t know if it’s good enough for bracing but I’d think more about how you can pin the panel centres, without consuming too much volume. I see quite a number of small subs with profiled MDF that stiffen by pinning panels together. It will be stiffer with them in place, but quite a lot of volume for the level of stiffening ?
With the depth of the driver, the closest I'd get to a straight run from centre to centre of each panel is a third. I could have used MDF, but with the space I have available, I'd be using a similar pattern to what I'm suggesting above, but less rigid?

I tried to keep things simple and using what timber I have available. But maybe I need to re-think this.
 

IWC Dopplel

Distinguished Member
If you think about one of the panels when they resonate They will move mostly from the centre so it’s trying to stop the panel flexing. One of the uprights will add stiffness it’s just that bending that upright is much harder if it’s pinned to something opposing. Not sure if you can add any struts that are strong enough to brace but not flex

Another thought is triangle braces that might tie the sides together as well

I was an engineer so it’s only really applying engineering thoughts. I may well have over engineered my build. Interesting I can still hear some resonance when knocking
 

MaxeII

Active Member
If you think about one of the panels when they resonate They will move mostly from the centre so it’s trying to stop the panel flexing. One of the uprights will add stiffness it’s just that bending that upright is much harder if it’s pinned to something opposing. Not sure if you can add any struts that are strong enough to brace but not flex

Another thought is triangle braces that might tie the sides together as well

I was an engineer so it’s only really applying engineering thoughts. I may well have over engineered my build. Interesting I can still hear some resonance when knocking
Thanks. I appreciate your advice.

It's not easy to find good examples of bracing used in relatively small subwoofers.

I've been searching again and I think I need a donut brace to get the support around the centre of the depth, where the magnet will be.

Donut.jpg
 

IWC Dopplel

Distinguished Member
Yes that makes sense, I'm no expert, I've built 2 subs in total !

Some of these if you used some of the offcuts might work well, obviously the bigger the triangle the better the brace, just avoid it being too restrictive for air movement

Screenshot 2021-09-30 at 15.10.27.png
 

MaxeII

Active Member
Yes that makes sense, I'm no expert, I've built 2 subs in total !

Some of these if you used some of the offcuts might work well, obviously the bigger the triangle the better the brace, just avoid it being too restrictive for air movement

View attachment 1578972
Thanks. I thought about something like that but if Bill Fitzmaurice know what he's talking about, he states that bracing in the corners of the cab is of no benefit, as that's where the cab is most resistant to vibration.
 

IWC Dopplel

Distinguished Member
No doubt the centre of the panel will move the most, the further away any support or strengthening is from the centre and the less direct the brace the less effective it will be

I have seen an almost space frame suctucture used a well

This looks good but a lot of work

Screenshot 2021-09-30 at 16.13.22.png
 

MaxeII

Active Member
No doubt the centre of the panel will move the most, the further away any support or strengthening is from the centre and the less direct the brace the less effective it will be

I have seen an almost space frame suctucture used a well

This looks good but a lot of work

View attachment 1579018
Yeah, I've seen some extremely intricate bracing designs that seem like they would be a nightmare to try and recreate, to some that are so simple and don't look like they would do a thing.

That looks like what I'm heading towards but with just the one donut brace, as my subs will be probably about half the depth of that one.
 
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Matyam

Active Member
Let's hope they don't go 😁walkies
 

mattkhan

Distinguished Member
I have built barely braced subs and subs built like a tank, knuckle test or similar (orbital sander was always a good test for this) is audibly different, in use, makes literally zero difference (assuming the box itself is well built).
 

MaxeII

Active Member
I have built barely braced subs and subs built like a tank, knuckle test or similar (orbital sander was always a good test for this) is audibly different, in use, makes literally zero difference (assuming the box itself is well built).
So what are your thoughts on the bracing in the picture I uploaded please?
 

mattkhan

Distinguished Member
The 18mm outer wall means the box will be 30mm thick all round (except the baffle which is even thicker)?
 

MaxeII

Active Member
pretty chunky :)

I think it will be fine, if you wanted to go belt and braces then you can tie each of those pieces together with some extra links. V similar to how http://libinst.com/SynergyDIY/SmallSyns/SealedV2/Sealed Box Drawings.pdf is designed basically
The double wall helps me achieve the final finish for the top/bottom and sides. The extra 12mm layer on the front baffle is the first layer to start "sinking" the driver into the cabinet. I'm planning to have 2 more layers of 12mm to make up a front grill, clothless, but covering the bolts and enough to stick out a few mm more than the roll surround of the driver.
 

IWC Dopplel

Distinguished Member
When my Sub is on, I can still feel energy in the cabinet, no noise or vibration but happy I spent the extra time bracing, even if its was only for completeness. I have also been pleased with a washing machine matt half under the front and half under the back as this does seem to be very rigid but compliant enough to soak up some of the cabinet transmission into the room
 

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