Building the NatalieP

[jerusalem]

I finally ordered natalie p parts from partsexpress to christmas gift , but because what comes to speaker building im completely amateur so... This thread will be my FAQ page, i will post here problems as i come across them (lot to be expected).Thanks in advance for anyone posting here!

As there are two enclosure recommendations, 30l for bookshelf speaker and 50l for tower it seems i cant make my mind which to choose.

These will be used mostly in nearfield usage, but having bottom reserve is not bad thing for barbecue parties could this kind of enclosure used for maxium authority???

Original: (cm)
30l bookshelf speaker 52x19x30~30L (inside)

Proposition: (cm)
50l Bookshelf speaker 55x25x36~50L (inside)

So in nutshell make bookshelf with inside enclosure 50L and give it 3" port in bottom tuned to 28?hz + speaker spikes like in the tower but still compact size.

I have no speaker building education, so is this now stupid idea, or could it work?

[JonMarsh]

That's the way I would do it; all things being the same, I prefer more extended bass. But sometimes folks don't have the room for the larger enclosure. Also, the original designs were done around the PE cabinets, which didn't give much flexibility, but gave a very nice ready made enclosure. Sometimes that's a reasonable trade-off.

~Jon

[jerusalem]

Another question about practicality:

If the port is in the bottom, it has to have free space under the speaker, which is in the original tower made by using spikes.It crossed my mind that what if i changed the spikes to stands integrated the speaker like in the subwoofer below:




and i would make wooden plate to bottom also integrated to speaker, so the whole system would be something like this:

Possible? and if yes how big space should i leave between bottom plate and port?

[jerusalem]

I ordered Sonic barrier 3/4" from partsexpress, but they had't that item in stock, so i got none.At local speaker building shop they said this would be ok, so can this be used on the side walls of natalie p?

It is like this: acoustic foam

[JonMarsh]

Use at least 2/3 the diameter of the port; preferabbly the full diameter or a little more. The other foam will be OK. I also usually use some polyester batting (like used for quilting, for example) right behind each driver.

[sturebjorvig]

Proposition: (cm)
50l Bookshelf speaker 55x25x36~50L (inside)

Hi Jerusalem,

I am not an expert on this, but I think you should keep the baffle width the same as the original, if you want to use the same xo as in the original Natalie P. But other than that, I think you can change whatever you like to suit your needs

Sincerely, Sture

[JonMarsh]

Most definitely the baffle width must remain the same or BSC comp in the crossover won't be correct any more.

[Brian Walter]

Unfortunately Jon, I think you unknowingly told him it would be okay to go with a wider baffle back on December 24th. I hope he hasn't already built the box.

Brian Walter

[JonMarsh]

well, a lot would depend on how much wider- 12" wouldn't be much of a problem, 16" would.

[jerusalem]

Unfortunately Jon, I think you unknowingly told him it would be okay to go with a wider baffle back on December 24th. I hope he hasn't already built the box.

Brian Walter

Well i thought again my needs (luckily) and my boxsize now is 31L with same front baffle width as in original.I would have builded this in christmas holidays, but woodshops were actually close all the holidays... :M

Now i dont know what actually is depht of the original parts express baffle, but is it enought to make front baffle from 3/4 mdf if i anyway make the tweeter chamber enclosure to strenghten front baffle?

I still have a time to go and buy another 3/4 to double front baffle as this is right now in progress...

[JonMarsh]

The original Parts Express baffle is 1"; you'll be fine if you follow the Modula MTM guide and include the tweeter back brace; this stiffens the front substantially.

Looks like you're coming along fine... :T

[jerusalem]

My crossovers are ready, and cabinet is half-ready, but i have a problem.How do you make perfect circles in frontbaffle for woofer/tweeter?I want them to be sinked in a bit, so the frontbaffle will be completely flat, like the tweeter is in the picture below.


I made frontbaffles with upper router ,but trashcan they went.They weren't actually that bad, but it would have bugged me to end of times if i had used those.

do i have to buy some tool for this???

[ThomasW]

You need to use a flat bottom bit (1/2"-3/4") bit to plow out the recess. Do that before you make the cutouts for the drivers.

BTW I retitled your thread to reflect the real topic, since the way it was originally titled would make people think there were 'problems' with the NatalieP design itself.

[JonMarsh]

Take a gander at the Modula MTM thread, Jerusalem. Lots of info regarding physical construction; difference between the two projects is the crossover.

Here's what your baffles should look like after routing, and cutting out the holes, and mounting the baffle braces behind the tweeter cutouts.




And when the drivers are mounted, like this- here I was testing tweeter crossover.

[wildfire99]

You need to use a flat bottom bit (1/2"-3/4") bit to plow out the recess. Do that before you make the cutouts for the drivers.

I just use the Jasper Jig (worth every penny) and a 1/4" spiral upcut bit and start out at the maximum diameter of the driver cutout and work my way in, after setting the router to the proper cutting depth for the driver and gasket material. Never any problems that way, and no surprises with compensating for router bit widths, nor issues with changing out bits. Just move in (on the jig) by 1/2" each time. Then make the through-cut/cutout when you get to the right diameter.

Of course, always figure out your depth with scrap and make a test cutout first before messing up your proper baffle. That's obvious but I still try to cut those corners sometimes, with bad results.

Here's a tip if you don't do it right and you don't want to waste your baffle:

I ended up still messing up the depth on my last set of baffles. Instead of playing the "find the center of the hole" game, I just cut out new holes the proper size of the driver (diameter) in two pieces of scrap. I stacked them (so they were 1.5" high so my router bit had clearance), brad nailed them together, and ran them through the table saw, cutting off the corners of the top-most piece of MDF.

I then centered them (visually) over the existing hole, and brad nailed it to the baffle to hold it in place (just use two brads and don't shoot them all the way down - you'll only have 3/4" of material to go thru since you cut the corners off of the top piece in the previous step). It was then an easy process to use a pattern bit (flush trim with the bearing on top of the cutter) set to the right depth to clear out the existing hole to the right size and depth. Worked like a charm, especially since I had to fix 14 holes. Remember, even if you write down your measurements, make sure you wrote them down correctly. :x

[jerusalem]

Well i have learned a lot building these speakers, one thing is you don't try something on the border of impossible without right tools.These are as perfect as eye can see after smoothing the edges.Upper router was my brother's and after some consultation i found tool for makeing circles with upper router in dephts of our family's garage.

tomorrow i have to go and buy tool for tweeter holes, after that its wrap up & listening test that crossover works.

Maybe next weekend i can finally finish this, btw what would you use for piano black surface?

[ThomasW]

Real piano black finishes are REALLY difficult and time consuming to create. Consider buying a spray can of gloss black polyurethane paint and leave it at that. Add top coats of clear gloss poly to add depth....

[jerusalem]

This might be a bit stupid question, but i have to be sure, so this is for the "slim bookshelf" model:

"If space and size are a factor, then a slim bookshelf enclosure of ~ 30 liters can be used with a 2" port tuned to 32 Hz, which will result in an F6 of ~ 38 Hz, with some in room extension below that. "

"Next step is to cement the inner port flare in place; in my case, with a 3-1/4" long cut center tube, the back of the port flare sits flush with the inner brace. You'd think I planned it all that way.... "

Is the port tube 2" wide and 3-1/4 long overall from the backbaffle?

[ThomasW]

When you quote text from a project that's different from yours, it's easier to get help if you refer to the thread you're quoting...

To answer your question. The flared ports have 3 sections, 2 flares and a straight center tube section.

Now reread Jon text "with a 3-1/4" long cut center tube,....". That means 3 1/4" is only the length of the straight section of the port, excluding the flares

[Dennis H]

I think Jon used a double-flared port which has 3 pieces you glue together -- 2 flares and a center tube. 3.25" is the length of the center tube.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=268-348

[jerusalem]

Beside that top enclosures of cabinets are off, speakers are almost ready for finishing touch.Before i seal those cabinets i have few questions:

-I heard that LCR zobel could be added to eliminate hump in tweeter in this desing too, so since it seems that this project takes more and more time it is proper to do it "right" and hell with the expences.

I posted picture of modula mtm crossover, with quite crappy highlighting what i think could be zobel.So in otherwords can someone show here what parts i need for LCR zobel, and where do i connect it in original natalie p crossover???

-Btw i bought shielded versions of rs28a and rs180, should i have bought unshielded or does this even matter?

[JonMarsh]

No, the tweeter LCR zobel is the L5/R4/C? (it's obscured by your cut and paste) network in parallel with the tweeter. This controls the tweeter impedance rise in the low end, and will elminate the bump up in the filter response due to that impedance rise. :T

Nice to hear someone taking my suggestions seriously, in spite of a few extra bucks cost.

~jon

[TEK]

so since it seems that this project takes more and more time it is proper to do it "right" and hell with the expences.

Been there done that! :T

[jerusalem]

What about stuffing? Since my cabinet is 30l ported, i heard somewhere that you dont stuff ported cabinets, but line inside walls???

Does this mean that using acoustic foam inside all around is what i should do??

[ThomasW]

Cut pieces and attach them to the walls. You don't want to stuff a little 30L ported box

[JonMarsh]

A small amount of batting behind the midwoofer is probably a good thing- I use quilt polyester batting. Don't fill the box, and don't block the port area. I use WhisperMat to line the boxes, but I'm sure many other types will work OK.

~Jon

[jerusalem]

Now before i screw down the elements, last verification:

-Whole box can be lined with acoustic foam to the walls?

-Little amount of batting (i have polyfill) Behind the midwoofers, how much is little (being overcautious here), and do i put it close the woofer, or leave a little space behind the woofer?

[JonMarsh]

Yes, cover the walls, and try sections of batting about 3-4" thick which fill the width and height behind each driver. Doesn't have to be right behind the driver. In the center of the space is better than at the wall boundary. Quilting batting is good to work with because it's a little stiff and folds nicely, can be cut to size and wedged in. Loose polyfill is more troublesome to work with.

[jerusalem]

They are ready now, but bass seems to be gone??? It doesn't feel right, my 1 element 7" kef has more output than natalie p right now.Propably too much batting in the middle.I will work it out on tomorrow because im too damned tired right now...

Pictures coming up when i have camera in order.And listening impressions when it has burned in and et cetera.

[jdybnis]

Yes too much batting. Listen first with nothing behind the driver. If it is impacting the bass then you've put in too much.

[cjd]

Well, it's always worth double checking to make sure you have the drivers wired in parallel properly...

I've done that even when I *have* double checked things. It's just too easy sometimes.

[jerusalem]

It wasn't about batting, and there is a flaw in sound, middle bass is boomy and upper frequences are coming from far away.I propably have to post here crossover pictures/drawing for cheking.

[cjd]

Sounds more like a phase issue (i.e. one of the mid-woofers wired out of phase) to me than before.

C

[jerusalem]

It wasn't either about connections, midwoofers were rightly connected, so there is still some options to go wrong.Down is a picture about speaker connection +/- , that's how i figured out it should be connected.

It's propably is right, so crossover mistake and port lenght are left.I didn't use original parts express tube so i couldnt know (or find) the actual lenght of whole tube from one end to other. Mine is (5.1"), is this correct lenght?

[ThomasW]

Mine is (5.1"), is this correct lenght?

That's the problem. 5.1" is length of the center section of the pipe, when one is using a flared port kit.

Depending on the size of your box (net 50 liters?) a straight port should be ~11" long

[jerusalem]

Depending on the size of your box (net 50 liters?) a straight port should be ~11" long

Mine's is around 30l,I have a small room to listen, these being speakers for computer so new porth lenght (whole lenght) should be ~11?

[ThomasW]

For a 30liter box, if you're using 2" tube, the length should be 8.6" for a 29Hz tuning. With your current length, 5.1", you've got a 36Hz tuning

[cjd]

That wouldn't give it a complete lack of bass though.

It will probably be fairly dry, but it should still have the extension.

C