New John Krutke project - minimonitors!

[fjhuerta]

Including the Aurasound tweeter... a 4" woofer. Quite interesting,considering a friend just asked for a small minimonitor. Thank you, John! :T

[jkrutke]

Including the Aurasound tweeter... a 4" woofer. Quite interesting,considering a friend just asked for a small minimonitor. Thank you, John! :T

Thanks for the comments. If anyone has any questions or clarifications, I'll listen to them here. This is one of several small speakers on the design bench right now. Probably the cheapest of them.

I'll be doing another higher end (more expensive) version with the Titanium TB someday, unless I find a better 4" woofer. Aside from that, it will probably be the last box-style minispeaker I do for a while.

There was that other thread somewhere about a project for "filling a niche". I think one niche needing filling is on-wall specific designs. The first experiment I did in that regard was the "slimline wall mount" with the Aura woofer. There is a limit to how good a box style speaker can sound placed up against the wall. I'd like to expand on new cabinet shapes that smooth on-wall response.

Another niche might be low budget projects that actually sound good, and maybe this mini can satisfy that one.

Last night on these minis, I fired up Pink Floyd's Pulse on DVD that I bought last year and never watched. I hooked up a Dayton RSS315 crossed over at 100hz LR4. There were a few "ooh, ahh" moments. There were also a few "Grrr, I wish this was 16x9 with less video compression" moments, but at least the sound was great.

John

[Rolex]

John, I have followed your designs with interest and am eager to start on work on your Silver Flute design. I noticed you mentioned this could be the last of the "box style" minispeaker for a while. Would you mind elaborating on that a little? For example, when you say mini speaker do you mean your stand mount designs with a 6 1/2 midbass driver as well, or are you speaking more of your 4" woofer designs? Thanks!

[Jonasz]

John, which tweeter are you using in the ER18 design and are they also boxes?

Hope to see a dipoledesign or two from you in the future! 8)

[Jim Holtz]

Hi John,

I have a question too. You had indicated a RS52 design with the Aura tweeter and RS180's was in the works a while back. Is that still in progress or has it gone to the back burner?

Thanks!

Jim

[jkrutke]

John, I have followed your designs with interest and am eager to start on work on your Silver Flute design. I noticed you mentioned this could be the last of the "box style" minispeaker for a while. Would you mind elaborating on that a little? For example, when you say mini speaker do you mean your stand mount designs with a 6 1/2 midbass driver as well, or are you speaking more of your 4" woofer designs? Thanks!

By minispeaker, I mean something with a 4" or smaller woofer. And by avoiding "box style" minispeakers, I merely mean something non-rectangular, specifically designed to avoid the sonic signature of the average "box on a wall" system.

I might mention that I recently discontinued that Silver Flute design in hopes of publishing something better soon. If you still need a copy of the web page, let me know. (here, since I don't post my email address)

John, which tweeter are you using in the ER18 design and are they also boxes?

All I know for sure is it will be a 104mm Seas standard. I have a 27TDFC in there right now. Yup, it's a box. Oooh, exciting huh? :B

I have a question too. You had indicated a RS52 design with the Aura tweeter and RS180's was in the works a while back. Is that still in progress or has it gone to the back burner?

I'm currently using them as stands for the Minis in my HT room. I'm sure I'll eventually get them to a point where I consider them finished, but that's not to say I'll be publishing them. Feels like the world has enough RS 3-way systems. I just wanted to hear one with the RS52 myself. I'm a little slow on the RS driver bandwagon but I do like them.



At any given time, I have 4-6 projects in the works. I generally finish whichever one gets me the most excited.

[Brian Bunge]

I might mention that I recently discontinued that Silver Flute design in hopes of publishing something better soon. If you still need a copy of the web page, let me know. (here, since I don't post my email address)

Have you found other inexpensive drivers which you feel are better than the Silver Flutes? I was thinking of doing some really inexpensive TM's and MTM's with the Silver Flute woofers and some low buck tweeters but am also open to other ideas for the woofers.

[jkrutke]

Have you found other inexpensive drivers which you feel are better than the Silver Flutes? I was thinking of doing some really inexpensive TM's and MTM's with the Silver Flute woofers and some low buck tweeters but am also open to other ideas for the woofers.

I've found the Tangband W5-704 to be a better woofer. It's a couple bucks more, but generally an all around better driver. I've got a bunch in my stock that I intend to use.

[technimac]

Hi John,
I have a question too. You had indicated a RS52 design with the Aura tweeter and RS180's was in the works a while back. Is that still in progress or has it gone to the back burner?
Thanks!
Jim

That'd be my question too........

I believe that was the TMWW project where the cabinets gave you some (ok, a lot of) grief and ended up as ex-mdf chunks in the trash.

Using those drivers in that configuration appeals to me as well. I've got a pair of RS52's, four RS180's on hand as well as a pair of D26CN55's (but could easily go with the Aura's).

Presently I'm building Jon Marsh's HiVi D6.8-based WMTW CC, but would love to do a pair of RS180-based TMWW towers to flank it.

"Feels like the world has enough RS 3-way systems."

Nawwww.........If at some point you decide to resurrect and publish that project, it'd get a huge :T from me.

Thanks for your continued contributions to audio DIY :thanku:

[Spanky Ham]

Another niche might be low budget projects that actually sound good, and maybe this mini can satisfy that one.


John

I think you or someone else may have mentioned doing a competition with speakers of $100 or less. I think this would be a kind of cool little contest. Maybe these will spur some interest in some extreme low cost designs. :T


Regarding the RS52, I am not aware of a lot of designs using this driver. Could someone give me a heads up of all the speakers with RS52s?

[Rolex]

By minispeaker, I mean something with a 4" or smaller woofer. And by avoiding "box style" minispeakers, I merely mean something non-rectangular, specifically designed to avoid the sonic signature of the average "box on a wall" system.

I might mention that I recently discontinued that Silver Flute design in hopes of publishing something better soon. If you still need a copy of the web page, let me know. (here, since I don't post my email address)

John, thanks for the response. I already have a copy of the silver flute design. I'm wondering though, should I hold off for this "something better" design, or continue on with the Silver Flute design? Thanks!

[Finleyville]

I would LOVE, LOVE, LOVE to see an all metal Seas 3-way floorstander from Mr. Krutke! Something which would compliment his already great L18 design. (Can you tell I'm a big fan of this pair? ;x( ) I know I would be one of the first to build them.

[fjhuerta]

Hi John,

I've read the project throughly... and I do have a couple of questions.

Regarding your choice of a small woofer, I noticed you mentioned not enough 4" woofer models, and hinted at a high-end minimonitor using the Titanium Tang Band W4-1337 (which I really like). What do you think about the Dayton RS125s? I know they are (on paper) a 5" unit, but it is almost as small as a TB 4". I was considering using it on my minimonitor speaker. Do you consider this driver a good alternative? Is the MCM a better choice because of its performance, or price (I assume taming the 125's peaks would require a more complex / expensive x-over)?

IIRC, you mentioned you were still looking for a 3/4" tweeter you liked. Is the Aura tweeter "it"? Or, is a 3/4" tweeter a better choice when building a 3 way speaker or a small 2 way (due to off-axis response, and a feasible higher crossover point?)

Once again, thanks! It's always a great day when you post one of your projects. :T

[Nemophyle]

i think the choice of john (without wanting to put any words in his mouth) for the mcm rather than the dayton rs125 , besides the fact that it costs 2* more (wich still isnt muchà, is that it will require both a more expensive tweeter , since you can't cross as high, and more expensive crossover, since the breakup is more pronounced, boths things wich raises the price quite significantly

[jkrutke]

John, thanks for the response. I already have a copy of the silver flute design. I'm wondering though, should I hold off for this "something better" design, or continue on with the Silver Flute design? Thanks!

Well, it may take a while for me to finish up the replacement system with the Tangband W5-704. I guess it just depends on how long you can wait. I don't dare set a due date on it, or I'll surely miss it. Maybe I'll just say "sometime this year".

Regarding your choice of a small woofer, I noticed you mentioned not enough 4" woofer models, and hinted at a high-end minimonitor using the Titanium Tang Band W4-1337 (which I really like). What do you think about the Dayton RS125s? I know they are (on paper) a 5" unit, but it is almost as small as a TB 4". I was considering using it on my minimonitor speaker. Do you consider this driver a good alternative? Is the MCM a better choice because of its performance, or price (I assume taming the 125's peaks would require a more complex / expensive x-over)?

IIRC, you mentioned you were still looking for a 3/4" tweeter you liked. Is the Aura tweeter "it"? Or, is a 3/4" tweeter a better choice when building a 3 way speaker or a small 2 way (due to off-axis response, and a feasible higher crossover point?)

I think "Nemophyle" hits it pretty close to the mark. The RS125 is a great little woofer, but I'd rather cross it over lower, which rules out a cheap tweeter. Essentially, the cost for an RS125 system would be double overall. The MCM does really well for it's price. The performance of a 4" woofer above 2 or 3kHz weighs as heavy as the price on the choice. I've got something else in mind for multiple RS125s, but I can guarentee it's not going to cost less than $150 a side.

I wouldn't call the Aura NT1 the ultimate 3/4" tweeter, it doesn't have enough low end balls. There is no ultimate 3/4". The Hiquphon has the low end but not the best non-linear distortion numbers. I can summarize the choice of the NT1 in this system by: Small diameter flange, low distortion from 3Khz up, and inexpensive. Actual dome diameter and off axis response were not a factor. To me, I'm perfectly happy with the top end dispersion pattern of an XT25 so obviously, off axis doesn't mean much to me.

Thanks for the interest everyone. I've got to travel for about a week, so I won't be back to this thread for a while.

[Audio-fiilis]

Happy holidays, John!

Looking forward to see a high cost approach from you. After all, the woodwork is such a pain to me that I would rather see quite lot of benefit gained after all the work.

Have you ever thought of an approach like in Amphion or Gradient? The theoretical judgement can, at least partly, be found from the AES paper written by Leo Backman. I consider it a recommended reading.

[fjhuerta]

Thanks for your answer, John. I think it's quite possible I'll build your project before the end of the year

[noah katz]

"There is a limit to how good a box style speaker can sound placed up against the wall."

I'd think a waveguide would be a good bet by keeping the sound radiation directed forward.

[fjhuerta]

Wouldn't off axis response suffer?

[noah katz]

"Wouldn't off axis response suffer?"

It would be lower in level, but better - less disproportionate rolloff of high freq.

[JonP]

A FYI for those contemplating this design... or any other that uses the tiny Neo Aura or Dayton tweeters...

I just got my Rockler catalog last night in the mail, they have the elusive 35mm forstner bit on sale. This one is list at $16.99, now on sale for $9.99. They have a few different kinds, from the price this one looks like the carbide one.

Since John states drilling the right sized hole for a good press fit is about the most difficult part of the project, thought I'd pass that along... The sale will probably last a month, but if someone comes along months later, there's still a $13 one for the cheapskates...

35mm Forstner Bits

[augerpro]

I don't see any for $9.99

[ThomasW]

I don't see any for $9.99

It's in their latest retail store sale flyer on page 5

[JonP]

I don't see any for $9.99

Doublechecked... it's the 46532 one that lists for $16.99. Nope, the low price is not visible on the site, but is in the mail flyer... Flyer says Sep4-Sep30, but retail stores only.

So, if you got to mail order, get the $12.99 steel one.

[jkrutke]

"There is a limit to how good a box style speaker can sound placed up against the wall."

I'd think a waveguide would be a good bet by keeping the sound radiation directed forward.

A waveguide is great for reducing the baffle diffraction effects, but it doesn't operate low enough to help out the real problem area. Here's an example dug out of my tidbits:

crappy cheap cube style speaker anechoic response
Same speaker placed against the wall

The depth of the box causes cancellation and combining of the wall reflection at frequency multiples, and it happens right smack in the midrange. Of course the same thing happens out in a room, but then it's lower in frequency making it less noticeable, and other boundaries can be positioned at different distances to cancel/smooth the effect.

I just got my Rockler catalog last night in the mail, they have the elusive 35mm forstner bit on sale. This one is list at $16.99, now on sale for $9.99. They have a few different kinds, from the price this one looks like the carbide one.

Thanks for the tip. I'm hoping a 35mm is enough to fit the tweeter in with minimal sanding. I would expect the 35mm bit to make a hole slightly larger than 35 mm, which would be just about perfect.

I'm an accuracy nut. Just so you all know, the diameter on the outside is 1.392" (35.36mm) and 1.417" (35.99mm) on the inside. It's not perfectly cylindrical but more of a tapered cone. If you get the hole size just right, it will press fit really well. My hole was 35.5mm. I used my Sears circle jig to do it.

A 36mm forstner bit seems a little harder to find, but would also work. It would not be a press-fit though and you'd have to use some 3/8" #4 screws into predrilled holes. Careful not to drill through from the back if you do that.

If anyone happens to try a 35 or 36mm bit to fit one of these tweeters, let us know how it works.

[dawaro]

Maybe on-wall isnt the answer, what about in-wall?

With PE now selling the blanks for in-wall instillations may be that is a direction that can be explored.

[ATB]

Near field

How would these be for near field listening compared to the 3" single driver project? I see that the crossover for the mini is not (yet) adjustable for BSC like the single drivers. My near field application is a computer desk in the middle of a small room and would be used for 2-channel music only, prob no sub.

[noah katz]

"A waveguide is great for reducing the baffle diffraction effects, but it doesn't operate low enough to help out the real problem area."

Thanks for the pic's, I see what you mean.

Somewhat OT, but have you investigated whether this can be effectively dealt with by EQ, either conventional parametric and/or the types including time domain correction like Audyssey?

[JonP]

How would these be for near field listening compared to the 3" single driver project? I see that the crossover for the mini is not (yet) adjustable for BSC like the single drivers. My near field application is a computer desk in the middle of a small room and would be used for 2-channel music only, prob no sub.

Going on generalities, they would be better on stands off the desk. Tweeter raised to ear level. You'd want to have them out away from the cubical wall behind them... but it sounds like you don't have that problem. Best would be to put them on stands, either on the desk, or on the floor behind it. PE has a small set of "satellite stands" that are cheap but nice, and adjustable. If you get them out and away from nearby objects, the BSC concerns don't matter anymore...

Check out the Cardas site for ideas on how to arrange the speakers best for your particular room...

Hope that helps...

[mtnickel]

I took the plunge and ordered parts for 5 of these. I figure it'll be nice to have a decent but cheap 5.1 system...

Hoping these will be an improvement over my CSS FR125's. good speakers, but i think it'll be nice having a dedicated tweeter.


Question:
Would there be many mal effects from using the center channel on it's side? the horizontal and vertical dispersion seemed good, so i don't see why it would be a BIG problem. Just curious as to anyone's thoughts on this.

I'll also probably run front mounted ports in case i have to mount them in the not so popular "close to wall" location.

I'll keep project status updated here, or can start a new thread if need be.

Comparisons to come vs my Dennis Murphey MB-27's (MBOW1 with Seas TFFC instead) and also my FR125 full rangers.

I've been meaning to do a zaph project for a while, but no project seemed to completely fill my requirements.

Mark
Surrey, BC, Canada

[happy]

Does anyone know where to buy the woofers for these? I would like to try a pair, but they seem back ordered everywhere for 3+ months.

I took the plunge and ordered parts for 5 of these. I figure it'll be nice to have a decent but cheap 5.1 system...

Hoping these will be an improvement over my CSS FR125's. good speakers, but i think it'll be nice having a dedicated tweeter.


Question:
Would there be many mal effects from using the center channel on it's side? the horizontal and vertical dispersion seemed good, so i don't see why it would be a BIG problem. Just curious as to anyone's thoughts on this.

I'll also probably run front mounted ports in case i have to mount them in the not so popular "close to wall" location.

I'll keep project status updated here, or can start a new thread if need be.

Comparisons to come vs my Dennis Murphey MB-27's (MBOW1 with Seas TFFC instead) and also my FR125 full rangers.

I've been meaning to do a zaph project for a while, but no project seemed to completely fill my requirements.

Mark
Surrey, BC, Canada

[jkrutke]

Would there be many mal effects from using the center channel on it's side? the horizontal and vertical dispersion seemed good, so i don't see why it would be a BIG problem. Just curious as to anyone's thoughts on this.

Generally this will work fine though I'd recommend the reduced baffle step version for the center. If placed on top of a TV, some of the lower baffle step will fill in a bit. The response due to baffle diffraction will change also, but not enough to be noticeable. There is a vertical lobing vs frequency plot for that project, which simply becomes the horizontal lobing when you lay the speaker on it's side. It's pretty wide and there should be no loss of dialog clarity for those sitting to the side, +/- 20 degrees

The crossover is relatively high on that system, therefore as you go past 20 degrees the off axis null that appears is also high, and a little less noticeable for those waaay of axis. This is completely unlike a sideways MTM, where the two woofers and the great distance between cause an off axis null right smack in the middle of the vocal range. (thus complaints about dialog audibility problems with many commercial center channels)

Does anyone know where to buy the woofers for these? I would like to try a pair, but they seem back ordered everywhere for 3+ months.

These woofers are only available at one place: MCM electronics. Unfortunately, they are indeed backordered. This is normal for every project I post. Drivers sell out until the initial excitement fades. They had about 100 of them when I first posted the project.

I tend to favor drivers that are available at multiple vendors but sometimes the drivers I want to use are only sold in one place.

[mtnickel]

Thanks for the advice.

I'm still undecided as to what i'll do.

I may play with LspCad and the diffraction simulator to see if there are any other shapes worth considering.

Perhaps a slightly taller Center maintaining a Tweeter over Mid setup (about 7").

I'll leave driver spacing as is, but move them around on different baffles to see what comes up.


As for the Reduced baffle step circuit, i think i'll end up buliding both for all 5 speakers as i live in a confined space where it may or may not be necessary. And in the event that they are moved to another location, the easy switch is nice. 1 jumper on inductor (2 taps), and 2 jumpers for L-pad circuit.

[JonP]

Does anyone know where to buy the woofers for these? I would like to try a pair, but they seem back ordered everywhere for 3+ months.

Yep, it's a bummer. I ordered two pairs... and one driver showed up with some shipping damage. (maybe just cosmetic, haven't tested it) Wish I had ordered more, but figured I could later. Hope I won't be waiting that long for the replacement...

Ah well...

[mtnickel]

For those who don't have a 35 or 36mm Forsner bit (a 1 7/16" would also work...if it could be found), i had a sort of DIY method.

I just looked through my set of router bits and found the closest one. It was actually 35mm as well. I drilled a hole so the bearing slides through, clamped down the router to the baffle, and slowly plunged out a nice hole.
Hope someone finds this useful and can save the $13 for the tool (Remember, this is supposed to be a budget project ).

Good luck guys, and i'll try and post some pics when i finish this.

[mtnickel]

Well that took a while to make some progress...
here's just a copy of a thread i started on my favorite forum diymobileaudio.com

link:

http://www.diymobileaudio.com/forum/showthread.php?t=31911

COPIED:
Hey guys, so i finally got around to taking a few pictures of these bad boys.

First some background...

http://www.zaphaudio.com/ZBM4.html

I'm staying fairly true to the original design.

Removable baffles - new for me, but this was pretty much necessary for the rear mount tweet. To aid in fitment, i made the front plates all slightly bigger, then bolted down the baffles tight and sanded flush with a belt sander. I'm pretty happy with how they turned out.

Front port - I switched to front port because i will likely use these on my desk which sits much to close to the rear wall for a rear port. On this subject, i also modded the crossover for the lesser baffle step compensation. I unwound the main inductor to the new value, added a tap there, then wound it back up. This way if i switch things around, i can quickly take the front baffle off and swap a few wires (also requires swapping some L-pad values).

Cheap mans flared port - I didn't feel like having a separate order from parts express (since i was already ordering from madisound and MCM), so i just used some 1" PVC pipe...FYI, did you know 1" spec'd PVC is actually 1 1/8" ID, YES inner diameter. So i have no idea where they get the 1" from, perhaps from the end fittings or something.
Anyways, for a cheap flared port, just use your round-over bit on the port . Maybe this is obvious, but i always love how it comes out, especially after painted.

Router work. These were slightly intensive on router work. The tweeter opening is an oddball size (35mm or something). Instead of buying a new custom/rare bit, i looked through all my router bits and found one that was very close (outer diameter of the entire bit...it was a decorative one of some sorts). So, i just clamped the router down and plunged the whole thing through. Worked like a charm. As zaph mentions, the frame on this woofer is pretty flimsy and hard to mount, i could have got away with 1 cutout, but i did the extra recess for a little more meat and sealing area.

Later this week will come crossover assembly.

Enjoy the pics.















My apologize, everything looks a little dirty, but they have been kicking around the garage for a while. They'll all get their share of sanding and filling. I usually go with the black textured finish as i can do it in about 20 minutes start to finish

Mark



EDIT:
More pics

Here's before paint, filled and sanded:

Preping for where i'll place these things

Painting:





Notice the lines from brush marks...not noticable at all after texture spray

Texture sprayed:



IF you look really close you can almost see the brush lines (go from bottom left to top right in the pic)...but it's really hard to tell and doesn't look bad at all.



Ok: it's like 2:30, so i just glued the mid in with some hot glue in 2 spots...will have to remove and seal properly and screw down, as well as use sealing tape for the baffle.



The fitment came out VERY nice, and the finish is pretty good too as usual with this spray. I used my typical 2 layers of carpet padding for damping (actually works not bad I think). Although i only had the 1 test crossover built, i listened to a little mono. WOW. The midrange is definately noticably better than my Dennis Murphy MB27- GR research/seas 2 ways (and parts are like 1/3 the cost). Bass isn't close to the 5.25" GR though (GR has 55hz f3). I"ll have to do more extensive listening and especially with 2 drivers. Might have to tweak the crossover too (i don't think the baffle step adjustment is necessary for on desk...tonal balance is a bit on the bright side). 3am...must sleep. More to come guys.

[dawaro]

What kind of texture paint did you use on them?

[mtnickel]

The infamous Dupli-color Truckbed Liner spray. Available at Walmart ($9 here in canada,but I'm sure they have in the states too).

[jkrutke]

Nice job on the baffles. Ironically, I'm using the "more BSC comp" version at my desk and they sound ok to me, not too heavy. Probably because the baffle is so small. This is completely unlike larger baffled speakers. I set my L18 design on my desk and compared to normal in-room listening, it went from flat to mud.

Hey, now I have a center channel at my desk!

[Bill Schneider]

I've built a couple of speakers from plans and kits, and I'm considering this minimonitor project while I await better weather before undertaking the larger Zaph ZDT3.

There's one change I'd like to consider though - the larger driver looks like it was designed to mount from behind the baffle. It would certainly look better if mounted this way.

The circular ridge on the front of the driver extends 3mm (0.115") forward, so if this is flush with the baffle front surface, I'd be displacing the woofer rearward that distance plus the thickness of the flange metal (0.011"). This offsets the woofer a total of 0.126" rearward.

Rabbeting of the woofer opening on the rear of the baffle would be necessary, but I can do that. However the acoustic centers of the drivers will be displaced from each other ~1/8" from the design.

Does this present much of a problem?

I suppose that I could slant the front baffle to compensate for the displacement, but I'd rather not if the changes aren't acoustically significant.

Bill Schneider

[mtnickel]

Nice job on the baffles. Ironically, I'm using the "more BSC comp" version at my desk and they sound ok to me, not too heavy. Probably because the baffle is so small. This is completely unlike larger baffled speakers. I set my L18 design on my desk and compared to normal in-room listening, it went from flat to mud.

Hey, now I have a center channel at my desk!

Regarding the baffles, I had one funny goof. I rabbited the wrong side of the tweeter opening on 1 of the baffles only. You can imagine my face as i kept flipping it over and over trying to figure out what didn't look right. quite comical. It was also brutal because i had to setup the router for every other routering i had already finished, Plunging, recess, cutout, rear rabbit. Sigh. Oh well.

The less BSC crossover is growing on me a little. I think it sounded so bright because i'm just used to the sound of my Dennis murphy MB 27 (GR M130, 27tffc) which have a full 6db BSC i believe. I have an EQ from my computer source, and i mimicked the difference from the response graphs shown to simulate the Regular version. I think the regular version is probably preferred, but somewhere right in the middle would probably be best. Since i don't have the parts lying around, i'll probably just construct the regular version and deal with any slight EQ required for my computer. That way they'll be setup for regular room listening.

Zaph, any ideas on sealing the tweeter? It has to squish down to nothing so that the depth remains perfect. It does fit relatively snug, so perhaps sealed on its own. My only idea for now is a soft cocking just on the outside of the rear flange (Soft enough to cut and tear away if need be).
Between cocking and the friction fit, i shouldnt' even need to screw it in.

[jkrutke]

There's one change I'd like to consider though - the larger driver looks like it was designed to mount from behind the baffle. It would certainly look better if mounted this way.

You could do that, but you've have to redesign the crossover from scratch. The woofer response curve and acoustic center would be different.

Zaph, any ideas on sealing the tweeter? It has to squish down to nothing so that the depth remains perfect. It does fit relatively snug, so perhaps sealed on its own. My only idea for now is a soft cocking just on the outside of the rear flange (Soft enough to cut and tear away if need be).
Between cocking and the friction fit, i shouldnt' even need to screw it in.

I just glue mine in. In the event it gets poked, I tap it out with a small hammer and glue another one in. If I decide I'm done with the speaker, the tweeter goes in the garbage with the baffle. Heheh, you've gotta like these cheap tweeters. I didn't cry when I poked one in once. BTW, a little tiny ding or crease ruins these, according to some tests I did.

[jkrutke]

Just another note in this thread, I'll be gone for a bit but I'll check back in a week or so. Thanks all for the interest in this project.

[Bill Schneider]

You could do that, but you've have to redesign the crossover from scratch. The woofer response curve and acoustic center would be different.

Thanks for the concise answer. I don't pretend to be a crossover designer, so I shall not do that.