Help with deciding subwoofer design.

[Sebr023]

Hi all!

I’ve been refered to this forum for my question.

I’ll try to make it short and as precise as I can.

and please don't be too harsh, its my first subwoofer design. so please, haha be kind! I'm still learning.

- I’m building a subwoofer coffee table.
I’ve discuss many design possibilities with my wife. She agreed on a table.

The design discussion included things like:

• - under the couch: cant really do it because couch is only 4in off the ground.
• - under the tv cabinet: she didn’t like it because the floating effect of the cabinet.
• - on each side of cabinet: she didn’t like it either.
• - behind the couch: not enough space to put a subwoofer, couch is already 6in forward to accommodate a table, and we could not forward it anymore.

- I already have (2) Dayton audio UM-15 to go

- I have 2 behringer inuke6000dsp to power the 2 UM-15

- pannels are already cut, but I’m willing to make (minor) modification to the box

- pannels are Baltic birch plywood. Bracing are mdf. And grille for design #1 is a mix of mdf and BB plywood.

- I don’t want to have visible hardware once the grille is removed.

- I’m working with ~ 135 liter of internal volume. As design #1 (facing outward) measurement of the table are : 16.5x16.5x40in outside. Inside measurement would be 15x15x37in.

- living room is ~ 10x 10, but is open on kitchen and hallway, which total gives a 18x30ft room.

- subwoofer will sit at ~ 16in from the wall on one side, and ~ 25ft of the next parallel wall. But will be in the “centre of the living room” (replacing the round coffee table in the picture)


Subwoofer use: tv/movie, video game and music.

So, I design the first one. And when I was brainstorming on ways to protect the subwoofer from our 2yo (1yo at that time) I came up with design #2 (bottom one). At that time, on another forum, people could give me the informations needed to confirm if #2 was a good idea and if it would work well. So I “scrapped” it.

When I started building the subwoofer again, I came up to the part where I need to think of how I’ll be making the grille.

In design #1, there are 2 baffle. Driver sits and screwed on baffle 1 and I have a second one over. Grille is made of (2) thickness of mdf Than the 1-1/4 slats.

So I started to think that this grille is going to be very heavy, and will need a sh*t ton of magnet to hold it securely in place.

That’s when I started second guessing my design.


So at this point, I think I have 3 option.
1- stays with design #1 and don’t make grile cause the driver is sturdy enough and my 2yo is kinda old enough to understand not to play with the woofer.

2- stays with design #1, and change the grille design for something Lighter ( I came up with a “acrylic folded box design” with a laser cut pattern

3- goes with design #2 and make a “slot” subwoofer.


My question is:
Would the slot subwoofer design would be a nice sounding subwoofer?!


Hopefully I provided enough information.

Thanks guys!

(Also, I added a picture of my CSS Audio Criton build as LCR)


Picture 1:

Picture 2

Picture 3:

Picture 4: grille

Picture 5: bracing

Picture 6-7 : LCR with laser cut grille, 3d printed grille stand off, and corian baffle (backed with 3/4 birch ply)

Edit: this is what I was talking about when saying folded acrylic sheet.

Open on 2 sides, top and bottom are used with magnet to old on the box. Different pattern than the one showcased because my computer had a hard time to render the one I wanted, and honestly, my skill in fusion are not on point, yet.

 

[BR52]

Why not down firing?

 

[Sebr023]

Why not down firing?

Thought of that.

Thw way the driver are place in the table will cancel vibration.

Down firing would not cancel vibration.

 

[ppataki]

@Sebr023 Just do a regular sealed DOS design (like in Picture 1) but without the divider in the middle - make sure that there is no divider at all inside the cabinet. Also make sure that the driver cutouts will be exactly symmetric (that will ensure zero vibration of the cabinet)
The ideal volume for the UM15 in such a configuration would be 152 liter assuming heavy wad stuffing
Since DOS design does not vibrate at all you don't really need a lot of bracing - I would even first try the box without bracing and then add some if needed

Will you connect the DVC in series to get 4 ohms and then connect the drivers also in series to get 8 ohms as the final impedance?

 

[Salt]

Skip braces, cut some broomsticks instead. Quick and (not) dirty.

 

[Timcognito]

Down firing or other design with ports or grill in the toe-kick of the existing cabinet with possible incorporation of existing sub with DSP.

 

[DVDdoug]

You can model/predict performance with WinISD (or other speaker design software). You can also model a ported design and decide which is best. If you have a divider in the box, that can be modeled as two separate subs.

As a generalization... A ported box puts-out more bass but the bass rolls-off more steeply... A sealed box rolls-of less steeply and eventually the curves cross so the sealed bos is putting-out more. With EQ and enough power you can (partially) overcome the loss of efficiency at the lowest frequencies. The maximum bass output is still limited but a pair of 15-inch woofers in a living room you'll probably be fine, depending on how the speaker characteristics interact with the box volume.

 

[poxymoron]

What am I looking at here? Glass/perspex in front of the drivers? How does that work? Looks good though.

 

[Sebr023]

@Sebr023 Just do a regular sealed DOS design (like in Picture 1) but without the divider in the middle - make sure that there is no divider at all inside the cabinet. Also make sure that the driver cutouts will be exactly symmetric (that will ensure zero vibration of the cabinet)
The ideal volume for the UM15 in such a configuration would be 152 liter assuming heavy wad stuffing
Since DOS design does not vibrate at all you don't really need a lot of bracing - I would even first try the box without bracing and then add some if needed

Will you connect the DVC in series to get 4 ohms and then connect the drivers also in series to get 8 ohms as the final impedance?

Forgot to mention it, but yeah, I was planning on filling all volume with rock wool.

Why skip the divider?

What's a Sealed DOS

both baffle was done with a flush cut bit for the opening. so they're are as symmetric as I could make them. Reading your comment I think I get what you mean. Id have to make sur the opening are positioned exactly at the same distance from the back and the front for example.

Also made me realize I forgot to put a picture of my "folded acrylic grille" concept.

Will you connect the DVC in series to get 4 ohms and then connect the drivers also in series to get 8 ohms as the final impedance?

I really dont know how to answer to this. I dont know.


thanks for you reply!

 

[Sebr023]

Skip braces, cut some broomsticks instead. Quick and (not) dirty.

Good idea!

but I already have 2 "window" brace already cut, and lot of "T" brace cut too.

Are broom stick better as bracing then what I already did and have on hands?

 

[Sebr023]

Down firing or other design with ports or grill in the toe-kick of the existing cabinet with possible incorporation of existing sub with DSP.

I have one existing subwoofer (Jamo 10in) but I'm lending it to a friend.
Cannot incorportate in tv cabinet as they're full.
One has the AVR, other one has ps5, apple tv and security camera hard disk recorder. 2 left has children book and games.
Didn't want to build subwoofer in the cabinet.

Also, the cabinet is 10in from the floor. didnt had enough space for 10in driver. and didnt want to build a subwoofer with 4 or 6 8in driver.

also, If im not mistaken, the internal volume didnt allow to have a port with those driver. port would have been to big to be able to fit in.

 

[Sebr023]

You can model/predict performance with WinISD (or other speaker design software). You can also model a ported design and decide which is best. If you have a divider in the box, that can be modeled as two separate subs.

As a generalization... A ported box puts-out more bass but the bass rolls-off more steeply... A sealed box rolls-of less steeply and eventually the curves cross so the sealed bos is putting-out more. With EQ and enough power you can (partially) overcome the loss of efficiency at the lowest frequencies. The maximum bass output is still limited but a pair of 15-inch woofers in a living room you'll probably be fine, depending on how the speaker characteristics interact with the box volume.

thanks for your answer.

box volume didnt allow to have a ported design. port lenght was way too big and cut on internal volume too much. I wasnt able to find the balance between internal volume, port size and port velocity in that box size for those driver.

as for the divider, honestly i dont remeber where ive seen this recommended and why it was better. And when I modeled 2 driver in the 'big box' or 1 driver per smaller box, I didnt see nay difference, and I think it makes some sort of sense in my mind. But I'm faaaaar from being a pro. In fact, its my first subwoofer design.

 

[Sebr023]

What am I looking at here? Glass/perspex in front of the drivers? How does that work? Looks good though.

they are paradigm inspired acrylic/ plexiglass laser cut grille. Probably not the best sound wise, but I wanted something good looking, unique but not too flashy, easily removable, with no visible hardware when grille are removed.

I usually prefer speaker without grille, but I have a 2yo child (1 yo at the time) and I didn't want her to put her finger on the driver and push in the tweeter haha.

thank you!

 

[Salt]

Good idea!

but I already have 2 "window" brace already cut, and lot of "T" brace cut too.

Are broom stick better as bracing then what I already did and have on hands?

Not better, but easy going and an option to insert, if necessary, after finishing the enclosure.

 

[Salt]

The divider would, literally, divide differences of the drivers. This, and driving parallel or dual amped, could minimize influence of each driver to the other.
My vote is +divider.

thanks for your answer.

box volume didnt allow to have a ported design. port lenght was way too big and cut on internal volume too much. I wasnt able to find the balance between internal volume, port size and port velocity in that box size for those driver.

as for the divider, honestly i dont remeber where ive seen this recommended and why it was better. And when I modeled 2 driver in the 'big box' or 1 driver per smaller box, I didnt see nay difference, and I think it makes some sort of sense in my mind. But I'm faaaaar from being a pro. In fact, its my first subwoofer design.

 

[poxymoron]

they are paradigm inspired acrylic/ plexiglass laser cut grille. Probably not the best sound wise, but I wanted something good looking, unique but not too flashy, easily removable, with no visible hardware when grille are removed.

I usually prefer speaker without grille, but I have a 2yo child (1 yo at the time) and I didn't want her to put her finger on the driver and push in the tweeter haha.

thank you!

Aha, I see the laser cut perforations now. I thought they were part of the driver. Doh! Does look good though.

 

[Salt]

Probably not the best sound wise, but I wanted something good looking

With these grilles You split one wave source into a hundred? or more with small diameter and add a resistance to the drivers front.
Would really love to see measurement with and without grille and the influence on FR and directivity. Interesting approach.

 

[Sebr023]

With these grilles You split one wave source into a hundred? or more with small diameter and add a resistance to the drivers front.
Would really love to see measurement with and without grille and the influence on FR and directivity. Interesting approach.

There was nothing scientific behind my reasoning.

When I’m home alone and can take measurement, I’ll be happy to provide them!

 

[Sebr023]

The divider would, literally, divide differences of the drivers. This, and driving parallel or dual amped, could minimize influence of each driver to the other.
My vote is +divider.

So it’s better to have a divider?!

I have it cut at an angle for now.
Like this

It’s supposed to help with standing wave. Or at least, or having an almost cube box for each driver.

Bracing are all over the place in this screenshot. Didn’t care to arrange them after changing the angle of the divider.

What does “divide difference”

They will be driven either each with an amp, or both on the same amp, i don’t know yet. Haha. Still to be determine.

 

[Sebr023]

I’ll update my first post, but this is the folded acrylic grille I came up with.

Open on 2 sides, probably. Top and bottom with magnet with a laser cut pattern. Probably not the one showcased, my computer had a hard time modeling it.