Sealed Infinity Kappa Perfect VQ

[mike c]

the EP2500 can put out 1600w at 20hz bridged 4 ohms (or stereo 2 ohms) at less than 1% THD

 

[TLS Guy]

Does the EP2500 have enough power to apply the boost around 30 Hz and not introduce large amounts of distortion or risk of damaging either driver or amp?

Yes it would have enough power. You can blow any speaker if want to behave like an idiot.

 

[Guiria]

Is there a way to calculate bracing to insure you have enough to raise the resonant frequency above the crossover frequency of the sub?

I'm specifically referring to the 1.25 cubic foot design.

I noticed in flippo's thread about his kappa perfect you (TLS GUY) point out two different volume displacement figures for the driver itself. .108 and .07XX. Which one should be used?

I plan on starting the build before having the drivers / amp / etc.

 

[TLS Guy]

Is there a way to calculate bracing to insure you have enough to raise the resonant frequency above the crossover frequency of the sub?

I'm specifically referring to the 1.25 cubic foot design.

I noticed in flippo's thread about his kappa perfect you (TLS GUY) point out two different volume displacement figures for the driver itself. .108 and .07XX. Which one should be used?

I plan on starting the build before having the drivers / amp / etc.

The correct basket volume is 0.108 cu.ft.

 

[Guiria]

I will be pricing out some hardwood cabinet grade plywood in my area today (hopefully) and I'd like to know what are the best hardwoods to look for?

Oak
Birch

Any other?

 

[TLS Guy]

I will be pricing out some hardwood cabinet grade plywood in my area today (hopefully) and I'd like to know what are the best hardwoods to look for?

Oak
Birch

Any other?

Well only the thin veneer is oak or Birch, the ply is fir. I personally use veneered MDF board, the sheets that a re veneered both sides. There is always a good side and a less than good side. If you are careful you can design it so you can put 1/4 round at the edges. Be careful not to scratch the veneer as you work with it.

Good luck!

 

[annunaki]

Cabinet grade plywoods are expensive. I priced some birch recently at $69.00 a 4' x 8' sheet. MDF is heavier but a heck of a lot cheaper. If braced correctly, mdf is every bit as good as plywood for subwoofer enclosures.

Plywood can be easier to finish by applying some stain or something but at nearly 3x the cost for material.

 

[TLS Guy]

Cabinet grade plywoods are expensive. I priced some birch recently at $69.00 a 4' x 8' sheet. MDF is heavier but a heck of a lot cheaper. If braced correctly, mdf is every bit as good as plywood for subwoofer enclosures.

Plywood can be easier to finish by applying some stain or something but at nearly 3x the cost for material.

Actually I think MDF is better. It probably is the best material we currently have for speakers. I hate plywood, because it warps. I think MDF is better acoustically.

 

[Guiria]

Finishing MDF

The finish is the part that always kills me. I've only finished speakers in high gloss black which takes FOREVER to get a good end product.

I haven't tried my own veneer yet though maybe that is easier.

Using hardwood gives me an edge in the finishing department.

As for weight, the sealed subs won't be that huge so MDF isn't ruled out, I am just looking at what else is available.

A flat textured black is probably the most practical as I will have kids using the sub tops as tables for tea parties and beds for dolls.

 

[TLS Guy]

The finish is the part that always kills me. I've only finished speakers in high gloss black which takes FOREVER to get a good end product.

I haven't tried my own veneer yet though maybe that is easier.

Using hardwood gives me an edge in the finishing department.

As for weight, the sealed subs won't be that huge so MDF isn't ruled out, I am just looking at what else is available.

A flat textured black is probably the most practical as I will have kids using the sub tops as tables for tea parties and beds for dolls.

I have moved to natural finishes, at the urging of my architect/interior designer daughter, who has an antipathy to staining wood. Red oak looks very nice. You can get red oak veneered MDF board.

Then sand it well. Use oil based products not latex, as latex raises the grain.

Then seal it and coat with multiple coats of mat varnish, use very fine grain sanding between each coat. It will look fine. That is what my daughter made me do in this studio, as she was the architect for the big renovation two years ago. If you click on the link in my signature you can see what it looks like.

 

[Alex2507]

Cabinet grade plywoods are expensive. I priced some birch recently at $69.00 a 4' x 8' sheet.

Thought I'd mention that I saw 3/4" Birch and Oak hardwood plywood at Home Depot for just under $50. However there did seem to be some voids in the plys that could be seen from the edge.

I keep seeing hardwood plywood recommended. Is there a void free hardwood plywood? Maybe a cabinet grade void free hardwood plywood?

One thing that I'm not getting about all this is why the veneer on the plywood matters. Once you run screws into your bracing, the veneer is shot. I can't imagine doing all that fastening from the inside of the box.

 

[TLS Guy]

Thought I'd mention that I saw 3/4" Birch and Oak hardwood plywood at Home Depot for just under $50. However there did seem to be some voids in the plys that could be seen from the edge.

I keep seeing hardwood plywood recommended. Is there a void free hardwood plywood? Maybe a cabinet grade void free hardwood plywood?

One thing that I'm not getting about all this is why the veneer on the plywood matters. Once you run screws into your bracing, the veneer is shot. I can't imagine doing all that fastening from the inside of the box.

I'm going to give you a direct piece of advice. MDF is better and easier to work with. Forget plywood.

Now you don't need to put any fasteners in from the outside. You rout all edges, rout for the braces and and use tons of Tightbond glue. You need lots of cabinet clamps. You clamp it together tightly with cabinet clamps until the glue sets. You don't need fasteners. If you plan your design right you can cover exposed edges with oak strips and quarter rounds.

Make the speaker face 1 1/2 inches thick. Use retentive bolts for the driver, and rout the baffle so the driver is flush. The driver mounts from the front.

Fill the cavity with Polyfill. It must be completely filled but do not compress it.

This might give you the general idea.

http://mdcarter.smugmug.com/gallery/2424278_zibdm#127083295_J9QXN

Try and avoid having to use veneers. They are very expensive and often peel down the road. The veneered MDF boards have industrial bonding of the veneer. Don't even think of using plastic veneers, they are a dead loss.

 

[Gimpy Ric]

I wish I could build stuff, but I'm gimpy. That Kappa driver must be really killer. You guys have fun .

 

[Guiria]

My local Lowes has hardwood void-free birch and oak plywood 3/4" for 41 bucks and 49 respectively. A sheet of MDF costs 29. I might try the birch and figure something out for the edges, perhaps something that goes over the edges instead of in the edges like a 1/4 round.

 

[WmAx]

I'm going to give you a direct piece of advice. MDF is better and easier to work with. Forget plywood.

You must be from a different planet than me. MDF is far more difficult for me to work with - it splits/cracks easy and makes the most horrible/toxic dust I have ever encountered from a wood product. I despise this garbage and will not recommend it for speaker building. I would recommend a medium density particle board over MDF, even. Georgia Pacific has a particle board with the same density as MDF for floor under layment but the particle board does not have nearly as horrible a dust as MDF, and I believe it is also cheaper. But a high grade cabinet ply is lower density, yet stiffer/stronger than MDF, and it will have a higher resonant frequency per a given panel span, making it easier to keep resonances out of the passband of the subwoofer with less bracing.

-Chris

 

[TLS Guy]

You must be from a different planet than me. MDF is far more difficult for me to work with - it splits/cracks easy and makes the most horrible/toxic dust I have ever encountered from a wood product. In addition, a high grade cabinet ply is lower density, yet stiffer/stronger than MDF, and it will have a higher resonant frequency per a given panel span, making it easier to keep resonances out of the passband of the subwoofer with less bracing.

-Chris

Well I prefer MDF. It does not warp and I find it easier to work with. The routing especially goes better. I think there are a lot of reasons why manufacturers use it other than cost. Once a cabinet is put together it is VERY strong. I agree you have to be careful of the edges while working with it. And I agree about the dust, but for all other reasons, I prefer MDF for speaker building. It also has much better internal damping than plywood.

 

[WmAx]

Well I prefer MDF. It does not warp and I find it easier to work with. The routing especially goes better. I think there are a lot of reasons why manufacturers use it other than cost. Once a cabinet is put together it is VERY strong. I agree you have to be careful of the edges while working with it. And I agree about the dust, but for all other reasons, I prefer MDF for speaker building. It also has much better internal damping than plywood.

I would say it is a huge error to count on internal damping properties of MDF or anything - it is woefully inadequate by itself. I always recommend, in full range systems, at minimum, a 3 layer wall using constrained dampening layer system, which will be several magnitudes more effective as compared to the internal dampening properties of MDF, regardless if you use MDF or plate steel(which has very little internal dampening on it's own).

-Chris

 

[Guiria]

Speaking of internal dampening, is poly-fill (acousta-stuff) as good a damping material as any for subwoofers?

I helped make an 8 inch sub with a passive radiator before that turned out great. We used acousta-stuff, the sub was used for music and never used at extreme listening volumes (probably never over 90 db). Building a sealed box with a high powered 12" driver has got me paying closer attention to details. I like acousta-stuff because it's readily available.

 

[Guiria]

Magnetic Stray

How far away from my tube TV will I have to keep these subs? I don't need an excuse to buy a new TV just yet.

Miner detail...

 

[WmAx]

Speaking of internal dampening, is poly-fill (acousta-stuff) as good a damping material as any for subwoofers?

I helped make an 8 inch sub with a passive radiator before that turned out great. We used acousta-stuff, the sub was used for music and never used at extreme listening volumes (probably never over 90 db). Building a sealed box with a high powered 12" driver has got me paying closer attention to details. I like acousta-stuff because it's readily available.

Depends on the size of the cabinet and the bandwidth it's used in. For a very small sub, polyfill is fine; but it has a bit different purpose than the stuff I recommend(high density fiberglass/rockwool boards). Polyfil and other loose fills in a sub are used typically to increase apparent volume inside the sub and to act as a dampening variable for the port or passive radiator. The material I recommend actually absorbs energy so that it can not effective reflect or resonate from internal boundaries. In a very small sub, the frequencies are so large in comparison to the internal dimensions, that no resonance or nulls can take effect in the first place, making such absorption material pointless. However, the loose stuffing materials have a function still.

-Chris