[Bretherman]

Hello,

I'm in need of some advice in designing a new enclosure for my Insignia drivers out of a pair of bookshelf ns-b2111 (popular with the GR-research upgrade) speakers.

One of my enclosures has recently been overcome by mold (result of not letting Water Putty dry completely before reassembling).
See: http://www.audiocircle.com/index.php?topic=148604.0

It was my understanding that I can just make another box with the same volume, and throw the same port on there, and be done with it.
Then I come across Baffle Step Compensation, and realizing port dimensions actually matter.

I used the GR-Research upgrade kit on these, and Danny included BSC into the circuit. It's my understanding that the baffle (the front of the speaker as I recently learned) should stay the same size.

Dimensions of the original baffle are:
8.75" wide x 13.375" tall.
5.75" driver hole.
2.5" wide x 6" long port tube.



Here are some pictures of the original enclosure:







Measured volume: 0.318 cubic ft = 549.50 cubic in.

The issue I'm having is with volume. The Insignia enclosure is curved and has less volume than a rectangle. Keeping the baffle the same size with the port up front, the box would have to be under 6" deep. That would give me a volume (roughly compensating for 3/4" MDF) of about 600 cubic inches, and no space for a 6" long baffle.

Considering BSC, does it only depend on the width? If so, I guess I could make the speaker much shorter, and maybe throw the port in the back.

Or maybe keep the original baffle dimensions, and put the port up top or bottom, so I can make it the necessary length. Maybe multiple smaller ports?

Any suggestions are appreciated.

[charmerci]

Why don't you just make a new front piece and use/refurbish the rest of the cabinet?

[Bretherman]

I'm fed up with the mold:





I've been trying to fight the mold for a few weeks. I just don't want this in my home anymore.

[charmerci]

No kidding. And black mold is awful stuff. Make you really sick. Be careful.

[S Clark]

These aren't exactly high end speakers to start with, so they aren't worth buying cabinets from Parts Express. If you have a table saw, I'd cut a rectangular box and use the front.  That front looks like it creates a bit of wave guide, so I'd look for a way to include it.  Or spray the hell out of it with Clorox and give it Goodwill.  Speaking of Goodwill, you might look around for a similar cabinet.  They often get non working speakers donated. 
Damn shame.  Projects are supposed to be fun, not frustrating. 
 

[Bretherman]

These aren't exactly high end speakers to start with, so they aren't worth buying cabinets from Parts Express. If you have a table saw, I'd cut a rectangular box and use the front.  That front looks like it creates a bit of wave guide, so I'd look for a way to include it.  Or spray the hell out of it with Clorox and give it Goodwill.  Speaking of Goodwill, you might look around for a similar cabinet.  They often get non working speakers donated. 
Damn shame.  Projects are supposed to be fun, not frustrating. 
 

Tell me about it.
I've already bought some MDF. Table saw, jigsaw, and minimal carpentry skills prepared. Got a router too if I can find all the bits. Not high end speakers, but imagine how good they'll sound if I go through all this trouble 
The front is just flat with a driver hole, and a port hole. I don't know if I want to mess with trying to separate it. It looks like it's already split down the middle, so it might be too much work to salvage it.

I saw some enclosures with an L-shaped port designed right in it -- similar to what is used for subs, or those cool looking horn speakers. I wonder if I can use this for a port instead. I'll try to draw up a design with a round port on top of the box though, and see if I can come up with around the same volume.
I feel like the box would end up being pretty shallow (with keeping the baffle the same dimensions). Is there any major downsides to having the back of the speaker closer to the back wall of the enclosure? Or at least for a cheap speaker like this?

[S Clark]

If you've got the tools then just make new boxes.  Keep the front baffle width the same.  Ports can be placed where you like them as a general rule.  L shapes are simply a way of getting the appropriate length in the cabinet. 
The panel that you show to the left of the screwdriver, does it attach to the front of the speakers?  If so, it is going to have an effect of the output.  The driver opening creates a bit of waveguide, and the port opening adds a bit of length and smooths the movement of air in and out.  That what I was suggesting that you use- if I interpret the photo correctly.

[S Clark]

oops, double post.

[Bretherman]

If you've got the tools then just make new boxes.  Keep the front baffle width the same.  Ports can be placed where you like them as a general rule.  L shapes are simply a way of getting the appropriate length in the cabinet. 
The panel that you show to the left of the screwdriver, does it attach to the front of the speakers?  If so, it is going to have an effect of the output.  The driver opening creates a bit of waveguide, and the port opening adds a bit of length and smooths the movement of air in and out.  That what I was suggesting that you use- if I interpret the photo correctly.

Oh, the black panel. Yes, that screws onto the front. I thought it was just for decoration, but you are probably right on the waveguide.
The main thing I was worried about was getting too much volume as a result of making the box large enough to accommodate the factory 6" long port.
It turns out there are a few factors that work in my favor, and I'm an idiot.

The MDF is 3/4", which if I make a box with the original baffle dimensions, just extruded out, the internal volume is quite a bit smaller. That, and the port will only end up sticking 5.25" in the box as a result, not the 6" that I was worried about.

I can make the box 8.5" deep, which gives me an internal depth of 7", which is enough to fit the port.

This would give me an internal volume of about 600 cubic inches (the original is about 550 cubic inches), which I think is fine since the much larger GR-Research board and No-Rez will take up some volume as well. Oh, and I never took into consideration that piece of wood that goes in between the port and the driver that acts as an internal brace.

Here is a quick drawing I made (this does not include the internal brace):



Heck, I could probably add another inch.

[S Clark]

The No Rez is open cell foam with a thin vinyl sheet, and wont take up space. If anything it will effectively make the box seem bigger in the way that it pressurizes. But you could always add another brace or two and take up some space.  Extra braces are always a good thing.  A 3/4" dowel rod running front to back, placed below the driver and above the port would be a good addition.

[Bretherman]

I drew out the enclosure design a little more accurately.



Somewhat following the design of the original, the brace is kind of just a piece of wood covering roughly half the depth of the box.

In regards to crossover placement -- in this case, is there any wrong way to install it? I could glue it in perpendicular to the driver magnet like it was mounted in the original, and it will sit just as close. If I mount it parallel to the driver, it can sit further away.
It will have to be mounted upright due to size.

A question about No-Rez. Is this a case of more is more? The original Insignia upgrade kit came with enough to cover the sides of the driver area, and none for the port area. I was planning on applying it to the port area, but I'm not sure if there was a factor (other than cost) it was not included.

[S Clark]

I don't know about that brace.  It looks to me that it would significantly restrict air flow between the driver and the port, and that's going to change the back pressure on the driver.  I'd simply run a dowel or a strip of mdf from the front baffle to the back- supporting the baffle centers or weakest areas. 
If you keep that brace, at least make it a window brace or cut two holes in the rear of it.

[Letitroll98]

If you can put the crossover anywhere, I would pick outside of the enclosure.  Everyone pays great attention to having their electronics isolated from miniscule vibrations and think nothing of their crossovers being jackhammered inside the speaker.  My crossovers are in a separate enclosure under the speakers, a simple box outside of the speaker would be fine.

It's pretty hard to put too much No-Rez in a small enclosure.

I'm no expert on internal bracing, but usually I see braces that contact all four sides, with the center cut out for air flow.  Without some mitigating reason for not contacting the front baffle, I would want as much bracing of that front baffle as possible.  Hope everything works out great for your project.

[Bretherman]

I think you two are right about the brace.
I'll probably end up running a piece of MDF front to back.

An external crossover would be cool, but I'd like these to be as small as possible. They will be going on top of a small counter. I like the idea though, that would probably save some hassle with trying to install the crossover itself!

I was hoping the wide plank brace would give me a place to glue the crossover onto, but I guess I can glue it onto the strip of MDF.

[Bretherman]

Here is the updated brace (just a mock-up):





I also have this MDF stick that I will end up cutting down into small blocks, and glueing into the corners:

[Anonamemouse]

Skip the "stick in the corners", the corners already are the strongest points in the construction. No need to enforce ir even more. A better idea would be to add a connection from the baffle to the back, like the one you did from sidepanel to sidepanel.
Try to keep the volume the same, and the size of the baffle the same. If you find you are losing volume because you are using thicker material, simply increase the depth of the cabinet. Also, a bit of dampening material would not hurt either. Don't put in a ton, just so that it is loosely behind the woofer without touching it, and is well away from the reflex port. Or, if you can find it, buy a piece of pritex (DO look for the high quality stuff) and glue that behind the woofer and against the top panel and side panels. Again, stay away from the reflex port.

[Bretherman]

Skip the "stick in the corners", the corners already are the strongest points in the construction. No need to enforce ir even more. A better idea would be to add a connection from the baffle to the back, like the one you did from sidepanel to sidepanel.
Try to keep the volume the same, and the size of the baffle the same. If you find you are losing volume because you are using thicker material, simply increase the depth of the cabinet. Also, a bit of dampening material would not hurt either. Don't put in a ton, just so that it is loosely behind the woofer without touching it, and is well away from the reflex port. Or, if you can find it, buy a piece of pritex (DO look for the high quality stuff) and glue that behind the woofer and against the top panel and side panels. Again, stay away from the reflex port.

Thanks for the input!

I'll skip the corner reinforcement.
That brace actually is going from the baffle to the back
I don't have anything planned to brace the side panels.
I have some wood left over I could cut and glue on either side of the brace to make a cross brace.
I ordered some No-Rez to line the inside of the cabinet. I should have enough to line the two sides of the cabinet, probably even put a layer on top top.
Though if I opt for a cross brace, it would make installation of No-Rez much more inconvenient. 

I made the baffle the same size, and the internal volume without brace is 600 cubic in, compared to the original braced enclosure's 550 cubic in.
Brace will take up some space, but not enough to get me exactly the original volume.