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AK Design Collaborative - Insignia-Class Economy Speakers (a.k.a Indignia)

Zilch said:
Unless I screwed up in AutoCAD, it should be about the same distance to both driver flanges.
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Your drawring looks good. I was probably hurrying a bit too much. It's not much different, just noticed it looks a little closer on the tweet. Could be an optical delusion too.

In the stock PE cabinets, the port's gotta get past a frame at the front and the brace in the middle.
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Yeah, I didn't feel like going snorkelling so I did it without internal bracing (unless I need to put something in later and I'll do that somewhere other than behind the port). I've got a friend with some nice cherry stock that I might be able to talk him out of (he's got a whole tree worth so 4 board feet might be easily doable). I was thinking of going matte black on the box with natural/oiled cherry cheek pieces. Should stiffen up the sides pretty well.

[Now, we all watch Ray's glue dry.... :p: ]
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You want a picture series or an AVI?

Ray
 
mightym said:
Wow,

I'm going to be re reading this thread over and over.

There is A LOT of meat here.
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Thanks, mighty one, and welcome to AK!

I read it over last night myself to see if I missed anything, and it's amazing the contributions so many members have made to this project.

AK ROCKS! :thmbsp:
 
RayW said:
For the new-to-DIY crowd:

-the driver cutouts are done with a router and circle jig. Find your center, set depth for the counterbore, and start at the outside. Move the jig in and continue until you get to the size of the through-hole. Then, and only then, cut through. If you start at the middle then you won't have a center reference for the outer stuff and finding a rabbet bit that's the right size is tough and usually expensive.

Ray
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Thanks for the explanation, Ray. Are the circle jigs what I see in the PE catalog, or are they common hardware store items?

I'm confused about this: "Move the jig in and continue until you get to the size of the through-hole. Then, and only then, cut through....." I guess I can't picture it because I have not used a router.

Maybe some kind soul will post a Youtube tutorial.....
 
Hmmm, if I hadn't cut the holes already... Maybe next time I do one I'll work on a video. By way of explanation how about this:

-for the woofer cut the counterbore (outer edge of the woofer frame) is 6 15/16" and the through hole (inside of mounting flange) is 5 5/8"

-the circle jig I use is the Jasper 200 that PE sells. I also have one that came with my router (Craftsman) but it's not as easy to use. You can make your own too, if you're inclined. It's nothing more than a way to keep a constant distance from the center point.

-First you drill a center hole for the circle you want. My jig uses a 1/8" pin for centering.

-I start with the biggest circle I'm going to need. In this case, the woofer flange counterbore. The jig has a pin that you move to different locations for different hole sizes. So on this one I started with the pin at 6 15/16 and the depth set the same as the driver flange depth stick the pin into the center hole and cut a circle by rotating the router around the center pin.

-since I'm just using a straight cut bit it only removes 1/4" width of material (the track it leaves). That means that the inner diameter of the track is 1/2" less than the outer. So for the next pass, move the pin to the 6 1/2" hole (I like round numbers) and make the cut.

-next move it to the 6" hole and make the cut (note, the depth is still the same as the driver flange depth).

-Next step would be 5 1/2" but the driver cutout is 5 5/8" so we go with that one.

-Then increase the depth at 5 5/8" and make another pass. Repeat the "increse depth, make a pass" bit until you cut all the way through. I usually cut about 1/4" at a time so it'll take 3 passes to get through 3/4" MDF. If you cut all the way through at once the bit gets really hot and you start burning through the wood instead of cutting.

-So now we have a cutout where the basket drops through and the flange sits flush with the baffle surface.

Does that make a little more sense? After you do it, it seems like common sense but attacking it the first time sometimes you don't look ahead far enough.

Ray
 
Indignia Crossover V3.5

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Optional:

Input binding post terminals:

http://www.partsexpress.com/webpage...bpa-38&search_type=main&WebPage_ID=3&x=15&y=6

Prefinished PE cabs, curved:

http://www.partsexpress.com/webpage...C-0.38&search_type=main&WebPage_ID=3&x=15&y=7

or rectangular:

http://www.partsexpress.com/webpage...-0.38&search_type=main&WebPage_ID=3&x=19&y=11

Blank front baffle only:

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=302-719

Magnetic grille only:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=302-718
 

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Perfectly clear Ray!
Thanks so much.:tresbon:

You just gave me the confidence to lose a digit:thmbsp:
or two.:thmbsp::thmbsp:



RayW said:
Hmmm, if I hadn't cut the holes already... Maybe next time I do one I'll work on a video. By way of explanation how about this:...[see post 305 http://www.audiokarma.org/forums/showpost.php?p=1950325&postcount=305]
Does that make a little more sense? After you do it, it seems like common sense but attacking it the first time sometimes you don't look ahead far enough.

Ray
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V3.5 Crossover Frequency and Phase Coherency

Inverse polarity notch is nearly 60 dB deep at 3.18° up from tweeter axis.

I'm calling that the acoustic crossover frequency, 1.940 kHz.... :yes:

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Translation: the drivers are pretty well in phase with each other at the crossover frequency. If you invert the phase of one driver then they will destructively interfere. That's what Z did there. The more interference you get with one out of polarity (180 degrees out of phase) the closer they are to being completely in phase when wired correctly.

Ray
 
They're certainly summing to flat(ish) in the crossover region, where our filters are controlling.

Above and below there, the individual driver responses are what they are, basically, in this baffle alignment.... :yes:
 
V3.5 Phase and Attenuation

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Note expanded (5 dB/div) scale for attenuation. About 1/2 dB per Ohm, looks like:

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I've been monitoring your progress, Gentlemen, and am getting ready to pull the trigger now that both kids are heading to school this fall with my used speaker surplus.

In order to get authorization from the purchasing department (SWMBO) and do it as inexpensively as possible, I need to build my own cabinets. As I am pretty handy but don't own a router or table saw, this may be impossible given the specified flush mounting of the drivers. I do have access to such tools (my brother) but they are not that convenient.

Question 1: I understand the potential value of the flush mounted drivers, but is a flush mount on the front baffle required to make them sound as good as they do at Chez Zilch?

Questing 2: Is MDF the preferred material for constructing the cabs for resonance and the like? I understand it is probably cheaper but was thinking that a butted cab made out of 3/4" scrap plywood might result in the "wolf in sheep's clothing" look that could be quite fun ("Those crappy looking unfinished speakers sound that good?"). I'm a "form follows function" kind of guy anyway.
 
My drivers are not yet flush-mounted, and they sound quite good without that. Like you, I don't have a router or table saw. As you can see in the pics of the prototypes, I used scrap plywood for the test baffles:

http://audiokarma.org/forums/attachment.php?attachmentid=90197&d=1210098124

http://audiokarma.org/forums/attachment.php?attachmentid=89791&d=1209771791

A friend is milling the stock PE baffles for me to use in the final design. It will be interesting to see how much of a difference that will make, as the flanges of both drivers are quite shallow.

The PE baffles also have rounded-over front edges. How important are these factors? We'll know soon, but I doubt they will alter the basic design. I consider them "refinements." Ray can tell us more.

Note that stock baffles are available from PE, ready for machining:

http://www.partsexpress.com/pe/pshowdetl.cfm?Partnumber=302-719

You can also purchase the grilles separately:

http://www.partsexpress.com/pe/pshowdetl.cfm?Partnumber=302-718


MDF is considered a good speaker building material because it is inherently damped, i.e., low-resonance. Scrap plywood or even solid wood may be fine for such small boxes as these, but I'd be looking for some scrap birch ply to build with. See what might be available in the scrap bin at your local cabinet shop, and don't forget IKEA's, either. You may find some nice laminate there.

Once Ray confirms the design, we'll post dimensions for the pieces to build the "standard" boxes. Your local home improvement center will precut them for you for a modest fee, most likely, if you buy new material from them. It doesn't have to be sheet stock. Look at their MDF shelving, for example.

Again, bear in mind that there is considerable flexibility with respect to cabinet design and dimension here, as long as they are well constructed and basically sized to enclose approximately the design internal volume.... :thmbsp:
 
Robie said:
Question 1: I understand the potential value of the flush mounted drivers, but is a flush mount on the front baffle required to make them sound as good as they do at Chez Zilch?
Click to expand...

Z kinda covered that one. The deal with flush mounting is that it takes out some of the re-radiation of sound. When the driver, and this is mostly a tweeter thing, is radiating hemispherically, i.e. a low enough frequency that it's not "beaming", the wave travels out from the driver but also along the baffle. If it hits something then a sound wave is radiated out from that point. The less things there are on the baffle (and this includes sharp corners) the less re-radiation you get and the more you hear just the drivers. Bottom line, like most things speaker, it can make a difference but it may or may not be audible to you in your room with your equipment and your ears. Vague enough?

A benefit of not flush mounting is that you can make some raggedy holes for the drivers and the driver flange will cover them up. :thmbsp:

Questing 2: Is MDF the preferred material for constructing the cabs for resonance and the like? I understand it is probably cheaper but was thinking that a butted cab made out of 3/4" scrap plywood might result in the "wolf in sheep's clothing" look that could be quite fun ("Those crappy looking unfinished speakers sound that good?"). I'm a "form follows function" kind of guy anyway.
Click to expand...

I like MDF because it machines well and it's pretty dimensionally stable and I can get it easily. Plywood will also be, by it's nature. However scrap plywood like the cheap pine stuff you get at Home Depot will most likely have voids in it and that can be a bad thing. Having empty spots in your speaker walls will add coloration. If you can find something void free then you'll be fine. If you can find something like 11-ply baltic birch plywood you'll have some good stuff for speakers. It's tough for me to get that stuff down here in the hinterlands so I usually go with MDF. Marine grade plywood works well too. MDF doesn't take abuse well though. However, I try not to throw my speakers down the stairs if I can help it.


Ray
 
RayW said:
A benefit of not flush mounting is that you can make some raggedy holes for the drivers and the driver flange will cover them up. :thmbsp:
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Don't be peekin' behind my flanges, now. :nono:



RayW said:
I try not to throw my speakers down the stairs if I can help it.
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Well, not after puttin' all that effort into resetting the magnet, anyway.... :p:
 
Just noticed that if you order a standard premade rectangular cabinet rather than the curved side .38 cu. ft. premade cabinet from Parts Express, they are over $20 cheaper per cab (~$72 for uncurved, ~$94 for the curved side cabinet). Lowers the price of "store boughts" by over $40 but still means you have approximately $250 invested unless you build your own cabinets. BTW, they look very well made.

I presume you can use the rectangular premades which are approximately an inch less in depth.

However, to avoid the $140 (plus shipping at 17 lbs. each) I'm pretty close to biting the bullet and attempting to build my first cabs, but cheating with butted sides and surface mounted flanges. It appears Ray is building rectangular cabs.

I'm awaiting a cabinet pattern that I think is forthcoming?

Thanks guys for this exciting project. I'm looking forward to it as it also give me a chance to try out my new brad nailer.
 
I also, am awaiting this cabinet pattern. I am excited to try my hand at bulding these beasts as well.
 
Robie said:
I presume you can use the rectangular premades which are approximately an inch less in depth.
Click to expand...

Yup, that was part of the appeal, availability and diversity of the box.

with butted sides and surface mounted flanges. It appears Ray is building rectangular cabs.
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Yup, as plain as possible on the build. Trying to work on a cool but inexpensive finish.

[/quote]I'm awaiting a cabinet pattern that I think is forthcoming?[/QUOTE]

What do you want? In simplest terms, it's a 8W x 14H x 10.5D (exterior) box made of 3/4" MDF. In order to make it viable for the PE baffle, I made the front and back 8 x 14, the top and bottom are 8 x 9, and the sides are 12.5 x 9. For construction, what I did was put the bottom down, stand the sides on it, put the top on, get all that squared away and clamped, then laid that assembly over onto the back, put the front on and clamped them. Doing it this way you can use clamps on the front and back to keep the other pieces squared up. Alternately you can do the top, bottom, and sides and use corner clamps to keep them square and then add the front and back later.

After thumping around on it a bit I have decided that I'll put a side-to-side brace inside. I'll just have to keep it out of the way of the port.

Helpful hint for those who have not done something like this before. If you're using a table saw then set it up to do one dimension and cut all the pieces that size at once. Then move on. For instance, set your fence at 8" and rip enough wood that width to do 2 x 14" (front and back) and 2 x 9" (top and bottom). Then go to your next dimension. That way all the parts that need to be 8" wide will be the same. If they're off a little it won't matter.

I'll have to fire up my Pro/E and do a real drawring for it some day, I guess. I'll have to remember how though so it may be a day or 2 (or 30).

Ray
 
If it turns out better to have the drivers recessed into a rabbet, would adding a second baffle layer of thin material have the same effect, soundwise, as routing a recess for the drivers? That is, surface mount the drivers, then make a second baffle of 1/8" or 1/4" hardboard (whatever thickness is needed) cut to fit the OD of the drivers, that would be glued to the front of the first baffle. This could be an alternative method for those who don't have access to a router to cut recesses for the drivers.
 
Thanks, Ray.

Great idea Jimbofish, but I'm guessing the flanges are pretty thin so matching their depth will require a second piece that is pretty thin too (approximately .15" and .125" according to Zilch's diagram), and therefore pretty tough to work with.
 
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