Intro

The drivers for this project were the NSBs and a Meilloon tweeter that PE had on buyout for quite some time. Unfortunately, PE is now out of the Meilloon tweeter, but they may be able to be found somewhere on the used or surplus market. The Tech Talk board would be a great place to try to find some.

Crossover

This was the first project where I tried to use software to help design a crossover. My friend Dave Brown helped me get driver files put together for the NSBs, I spent some time learning how to use Speaker Workshop, and then went to work. At first, I wound up very frustrated -- I just could not seem to get any crossover that looked like it could be decent at all. Finally I got something that looked like it might work and gave it a try. It was a first order on the NSBs and a third order on the tweeter. Unfortunately, the mids were very blarey or shouty, and the highs lacked air.

So off I went to TechTalk and SpeakChat seeking advice. Many many folks responded, including Dave Burke and Curt C. At Dave B's suggestion I lowered the value of the second cap in the high pass filter. Curt C. suggested some different values for the L pad on the tweeter. I wound up actually settling on a parallel resistor value midway between what I had originally and what Curt suggested. Curt also suggested I not reverse polarity on the tweeter. SpeakerWorkshop had been telling me to do so, so I had been doing so. But the minute I went with normal polarity and fiddled with the cap and resistor values, it all fell into place. The shouty mids went away, and the air came into the high end. Then someone else -- who at this point I cannot remember -- suggested I put a bypass cap on the series resistor in the L Pad. This basically creates a shelving network that holds the tweeter response up at higher frequencies. That brightened up the high end a bit more, and I called it good.

I should note that I used the same crossover in all five speakers, including the center channel.

Here is the final crossover schematic:

Note with respect to C1 that you can find nonpolar electrolytic caps in either 31 or 33 values; either will work.

Here is a picture of the assembled crossover, with each part labeled (well almost; see below):

The orange wire is not labeled. It is the Tweeter Positive.

My friend Dave Brown measured the final product for me. Here is a picture on axis:

Reasonably flat, especially given the parts I was working with.

Impedance

These are pretty clearly 4 ohm speakers. I have not had any problems running them on my $200 TEAC HT receiver, but still, I feel constrained to note that you should be sure your equipment can take the lower impedance. The last thing I want or need is someone building the UBHTs, frying a receiver, and claiming its my fault. I'm just a hobbyist and do this for fun. If I can help someone out, I feel very good about that; but I sure don't want to be blamed if things don't go right.

The Enclosure

Front and rear enclosures were built with 1/2 inch MDF except for the front, which is 3/4 inch MDF. The internal dimensions are 6.25 inches W x 19 inches H x 9.25 inches D. External dimensions are 7 1/4 inches W x 20 inches H x 10. 1/2 inches D. All drivers and the port tube are on vertical center. The top woofer center is 3 3/4 inches from the external top; the tweeter center is 8 1/8 inches from the external top; the bottom woofer center is 12 3/4 inches from the external top; and the port center is 17 5/16 inches from the external top. There is a 1/2 inch MDF shelf brace that fits right between the bottom of the top woofer and the top of the tweeter. There is also a cross brace that is a bit above the top of the port tube and halfway down the sides of the cabinet. Here is a picture showing the bracing:

The crossover board is 3 7/8" x 6 1/8", both so it would fit through the woofer holes and because there is not that much space for it on the back baffle. The top of it is located on the back baffle just below the shelf brace; and the top of the hole for the terminal cup is just below the bottom of the crossover board. By the way, I used 5 watt resistors less for budget reasons (using 10 watt resistors only adds about $3 to the total cost) than because of the size of the crossover board.

The port for the fronts and rears is PE part number #260-324, which is 2.88 inches in diameter and 5 inches long. I have left the port at that length.

All interior surfaces except the front baffle and the area over the crossover are lined with egg crate foam.

Center Channel

As noted above, I used the same crossover on the center channel. However, I changed the dimensions of the cabinet a bit, and used a different port and rear ported that speaker. And I must made a confession: I have long since sold these speakers, and I cannot find my records for the dimensions I used. I do know I used a 1.88 inch port trimmed to about 2 inches long, centered above and behind the tweeter, with the terminal cup below, and that I made the front baffle less long and a bit wider, and the cabinet less deep. I put a shelf brace in between one woofer and one tweeter. Sorry to be so imprecise, but knowing that the cabinet volume is .63 cubic feet should allow you to come up with workable dimensions. Against all conventional wisdom, I centered all drivers on the baffle, and did not elevate the tweeter. I built a prototype that way, and did not like the way it sounded as well as with all drivers centered. The picture at the top of the page shows the center from the front; here is a picture of the center from the rear:

Trim Rings for the NSBs

The NSBs are pretty ugly speakers, with little brass tabs sticking out for mounting, and a 1/8 inch tall ring around the surround. After someone else noted they were going to make trim rings for them, I thought that was a good idea. So here is how I did it.

I used what Home Depot calls “standard hardboard” – 1/8 inch thick. I did several test runs with the Jasper jig trying to find the right hole to use for the outer and inner diameters. I should note I am using a 1/4" spiral upcut bit from MLCS. I finally arrived at using the 5 9/16" hole on the jig for the outer diameter and the 3 15/16" hole for the inner diameter. But not so fast, it is not that easy. It turns out that at least with my bit, 3 15/16" is a bit too small, while 4" is more than a bit too big. So, I had to cut the 3 15/16" hole, then carefully freehand the inner diameter with the router to get to the right size. I wound up with a size that snaps down over the ring with a little pressure.

More dirty details. Everyone has their methods, and mine are no doubt stupid. I duct tape the board to a working board. Then I cut the outer diameter. Once I knew the right hole to use, I cut the other three trim ring outer diameters one after the other by taping a piece of the hardboard to my working board and drilling 3 center holes the right distance apart. Then I taped the resulting circle to the board again and did the inner diameter pieces. This time I had to switch each time in the same place, that is, I did not try to do all three in a production line like I did with the outer diameters. Then I carefully lined those up and used masking tape along the edges to tape them together, then lined that bundle up and taped them to the model ring I had made (that is, the first one I was able to make that came out right). Then I carefully lined up the bearing on my flush trim bit with the model ring, and trimmed the inner diameters of all three of the other rings at once.

Then I put them on an NSB, marked screw holes and drilled them. You can paint them black or use truck bed liner if you want.

After the paint dried, I used a plastic knife and spread Goop on the brass tabs and pressed the rings into place. Then I put on latex gloves and freehanded Goop all around the ring on the back side to seal them.

Thereafter, flush mounting with a trim ring was a breeze!

Parts

I am not going to provide a parts list, partially because you cannot find the Meiloons at PE anymore, and partly because PE has begun carrying some different inductors now. Suffice it to say that you can get away with nonpolarized electrolytic caps -- using more expensive caps would be a waste. You can get by with cheaper, smaller gauge inductors too.

Final Word

These are very efficient speakers. They can be run off a boom box, so they are a fun project to do with a child or teenager, and will provide much better sound than the speakers that came with the boom box. A number of folks who have heard them say they sound much better than they have a right to. I choose to consider that a compliment.



The Jessicas

The Jessicas are a tower version of the Ultra Budget Home Theater speakers. You can find all crossover information there; I made no changes to the crossover to build the Jessicas.

As should be obvious, the Jessicas were made as a Christmas gift for someone named Jessica. She had an old Casio CD shelf system in her bedroom that fed 4 ohm speakers, so I knew it could take the impedance of the speakers. But I wanted to make a tower configuration so there would be no risk of the speakers getting knocked off stands. Also, I had some old 5/8" particle board around, so I decided to use it instead of MDF. It even worked for the front, since both the tweeter faceplate and the NSBs with trim ring are only 1/8 inch deep, leaving 1/2" of the baffle left after flush mounting.

To make a tower, I had to put a "false bottom" or solid shelf in the tower, thus making an upper chamber and a lower chamber. The internal dimensions overall were 38 1/2 inches high by 6 inches wide by 8 inches deep. The dimensions of the upper chamber were the same width and depth, with a height of 22 3/4 inches. I used scrap 3/4 inch MDF for each internal solid shelf. There are two shelf braces made from scrap 1/2 inch MDF, one between the upper woofer and the tweeter, and the other just a little below the bottom of the lower woofer. The port is PE part number 269-920, an Ultimate buyout port that is 1 7/8 inches in diameter by 4 3/8 inches long. I trimmed it to 2 inches long, and located it midway between the bottom of the lower woofer and the top of the internal solid shelf that acts as the enclosure bottom.

The cabinet is lined top, sides, bottom and everywhere on the back except over the crossover with cheap egg crate foam from Wal Mart. The crossover board is mounted to the back of the cabinet behind the tweeter and lower woofer.

I put the binding posts near the bottom of the tower in the back, and ran the input wires through a small hole in the shelf that acts as the enclosure bottom. I sealed the hole (as well as all seams in the top chamber) with silicone. I also put a vertical brace, about halfway down the sides, in the bottom chamber, that was made from scrap 1/2 inch MDF. It measures 6 inches wide by about 10 inches long.

The bases are made from 5/8 inch particle board. I have forgotten the exact dimensions, but they are about 1 1/4 inches wider on all sides than the cabinet. I rounded each corner and then rounded over the edges. Then I sprayed them with truck bed liner. I then put rubber feet from PE under the bases, part number 260-771. The bases are screwed to the bottom of the cabinet with hex head screws.

Finish of the speakers is PE's cherry vinyl #260-014, which is very nice looking and easy to work with.

For the first time, I actually attached a name to speakers I built. I went to a trophy shop and had nameplates made. They cost $12 a pair, making them the most expensive part of the project, but they really finished them off nicely.

Ami's NSB Line Arrays

Ami has designed computer speakers using 6 NSB drivers per box, wired in two series groups of three drivers in parallel.  The nominal impedance is just under 6 ohms.  The boxes are sealed, trapezoidal, 0.5 inch mdf, and painted to match her computer.  After completing the pair, Ami will add a small subwoofer.

Isaac's 2.5 MTM NSB

These are my finished NSB surrounds.  The MTM's are wired in series and crossed to the tweet at 4000k. The lower driver is run parallel to all that and has a low pass at 300 hz.  Drivers are mounted from the inside of the cab, and I included a very well sealed removable back.   Finish is a kitchen counter type laminate I got out of the scrap pile at a cabinet shop.   The sound is good but boomy b/c of the small cabinet.   I think i will add a resistive port (aperiodic) made from PVC drain vent and some stuffing.

Mary Ann and Susan's Small Sealed Box

Maryann and Susan (sisters) decided to build small sealed boxes around single NSB drivers (PE #269-570) also nicknamed the 90 cent wonders. Very nice, a bit "airy", clean and smooth. The Clio response graphs are included below. They could use a baffle step compensation circuit and a small subwoofer.

Here are some details for those who might want to copy their design:

Thick cardboard trim tab was removed from the edge of the driver surrounds using a razor utility knife. This caused the surround to separate from the cardboard beneath it and the frame, so we reglued it using PE # 340-076.

The two response curves represent overlays of the measurement of each box separately. It is clear that about 4 dB of BSC wouldn't hurt at all. One should ignore the readings below 100 Hz as they are subject ot random room noise and other artifacts. The girls were very pleasantly surprised at the quality of the sound these speakers produce.

The bandpass subwoofer designed to support the NSB satellites from 140 Hz and down. An 8 inch Vifa (unknown 4 ohm model, donated by dB) plus a 150 watt PE plate amp melds very well with the NSBs.

Dave Burke's MTM's (photos)

Bruce's Array

One - Tweeter
Eight - 269-570 4" Mids
Two - 6 x 9 subwoofers

Robert's Coffee Can Speakers

Folger NSB's - I got the idea of using coffe cans for construction from Wil Kelch. The volume happened to be just right, and in keeping with the low cost nature of these drivers, the were a perfect choice. The tweeter used is the Meiloon silk sheilded that is on sale at PE. I found it difficult to make it sound as I wanted, and ended up using a textbook 2nd order x-over at 4000hz and padded the tweeter more than I would have liked, plus added an external L-Pad (you can't see it in the picture). If you look at Dan's UBHT project, you'll find a much nicer implementation of this tweeter. I used a 1" by 7" port. The can is lined with "Peel 'n Seal" and it does a great job. It is also about 75% stuffed with pink fiberglass insulation.

Low-Tech Can System - This attmept was a down and dirty, spend no money what-so-ever project.   Again, using coffee cans,  I used some cheap mylar tweeters, with a 5 uF cap and of course the NSB with a .7 mh coil.  Actually not bad, but a little peaky in the mids that work well with my nephews PlayStation.   He doesn't care, he just wants BASS.  So therefore I built him a sub using a 10" Peerless woofer that I couldn't find any specs for and hooked it up to a mini 75 watt JVC system that the CD function had broken and just used the amp function.  Heck he's even got a remote with this!  He's got the baddest  PlayStation on his block and now his Uncle Bob rocks!   The crazy paint scheme reflects his request of the colors of the Tampa Bay Bucs and their Superbowl win.   It isn't pretty, but he loves it.

Nick B's UBHT NBS's Center Channel

Ultra-Scrooge Center Channel I've built this "Home Theater" center channel speaker using inexpensive drivers from Parts Express .

They consist of the Onkyo 3/4" textile dome tweeter which cost a whopping 69 cents each and the 4" extended range shielded Pioneer driver. These drivers are so inexpensive because they are special "buyouts" from the manufacturer.

I used a simple 1st order crossover at 5000Hz and a Zobel network on the Pioneer to flatten its impedance gain.

The nice little Pioneer 4" driver. Parts Express #269-570

Front pic of the Onkyo tweeter. Parts Express #269-702

Rear pic of the Onkyo with the stock capacitor and wire harness removed.

Schematic of crossover used. NOTE: The 2 Pioneer drivers are connected in series.

Box made of 3/4" particle board that I had on hand.
The finished product! Box internal volume is .36 cu. ft. Port is 2" dia. X 4" long.
Internal damping is a layer of fiberglass on the back panel to reduce reflections.

Dan B's Mini-MTs

BOX: The inside dimensions of the sealed box are 6.5 deep 4 wide 9.5 tall. I think this came from Win ISD.

XO: A 2.2 uF cap on the positive side of the tweeter.

FILL: 2 hand fulls of fiberglass in the box

REVIEW: Not much bass but, these are lot nicer than the usual computer speakers. Most computer speakers have a real funky sound. I think the plastic box is partly responsible, none of that here. Since I don't have rear surrounds for my system yet I plugged these little guys in. They actually worked! I was afraid some thing would melt down but I kept the volume down and set the rears to (small). and they did pretty good. These should hold me over until I get some DHT - TMs built.

Single NSB and Meiloon Tweeter Network

Although not completed, I did have the opportunity to test the network in the enclosures. They work well! Again, more bass than they have a right to make. Because of the small enclosure size, I used 1/2" MDF with a single internal brace. They will receive a 1/2" roundover treatment. I mounted the NSB from the inside of the baffle. I cut a very close tolerance hole (basically a press fit) so that the the protruding lip on the woofer fit well. With the woofer frame in full contact with the baffle and the press fit, and usage of machine screws and nuts, it seems to be a much stronger mounting than I had anticipated. Works well so far and looks much cleaner than having to make trim rings.

NSB With Onkyo Buy-Out Tweeter

Driver features: 3/4" V.C. on paper former, large flat spider, paper cone, rubber surround, and a paper dustcap. 

And, with EQ boost, the bass on these is quite satisfying for nearfield (computer) listening. Imaging is good, but the clarity and detail is just unexpectedly good. Airy, clear, crisp, good depth and soundstage. For speakers that cost me under $10 to build, I'm a happy camper.
 
One NSB (269-570)
One Onkyo buyout tweeter with phase shield removed (269-702)
One 1.1mH inductor (20ga) in series with the NSB, one 10uF cap in parallel.
One 8.2uF cap in series with the Onkyo.

This should still easily be under $10 for a pair. I haven't tried the Onkyo, but have heard good things about this particular unit.

Since the Onkyo is a 4ohm, this is technically a 4ohm speaker (5 really). But, since it also doesn't get to the point where most amps would have issue till about 4800Hz, I doubt most 8ohm amps would end up having a problem with this. :)

Original concept of seven of the NSB’s in a line array using two of the 10” pioneer buyout woofers from last year (no crossovers!). 60’ tall 7” wide, 8” deep at the top & 16” deep at the bottom. They sounded bad! Tinny and no bass Removed one of the NSB’s and one of the woofers and added a 4” X 2” port for the six NSB’s and the same for the single 10” side firing woofer, much better! Burned a ¼” hole into the dust cap of each of the NSB’s, coated the cones with lacquer and covered the basket with PSA foam weather stripping. Better still. Did some basic bracing and sealing. Textured the outside with drywall mud using a course foam roller, sanded lightly and painted it gloss dark gray. Stained the front dark maple and flush mounted the line array . Built the base from MDF, painted it brown and the stained it with the dark maple stain, taking care to simulate a wood grain finish. Done at last! Sounds pretty good for less than $125 for the pair.