dB313	Back to Speakers
This is a small speaker for use in a home theater surround system as left/right mains, surrounds and center channel. The drivers are shielded. I chose these drivers based on positive recommendations by some folks on the Tech Talk forum. Dirk had used this tweeter and liked the clarity and detail. Another good thing about it is its small faceplate. John Krutke did an evaluation project of several small mid-woofers and he came up liking the Hi-Vi 3" mid-woofer alot. He did a very nice project using just one B3S (identical to the B3N except for the square frame) to make a full range speaker. Another thing nice about these drivers is the price. $9.58 for the B3N and $14.10 for the TM025F1. That makes the cost under $70 per speaker. You could do a five channel system for around $350. Then add a small subwoofer such as a Quatro 10 with the PE 120 Watt sub amp for around $180 and have a complete system for $530.
The configuration uses two woofers primarily because the sensitivity of the B3N is only 81 dB. Running two in parallel provides 87 dB which is just enough to mate with the tweeter as long as it is attenuated 4 or 5 dB.
Audax TM025F1	Hi-Vi B3N
I did the initial crossover design using SpeakerWorkshop with .frd and .zma files downloaded from the PartsExpress site. These measurements are done by Darren Kuzma using CLIO with the drivers mounted on a quasi-infinite baffle and not flush mounted. I chose the crossover point of 3600 Hz to give the tweeter enough room above it's resonance frequency of 1100 Hz and still be able to roll off the woofer well below its sharp break up at 7K Hz. Note that even though the crossover pic shows reversed polarity for the tweeter, it should be connected positive. Initially, I mistook the green marking on the tweeter terminal to be negative -- green for ground as is the standard in electrical industry. However, when I connected a 1.5 volt AA battery to the tweeter, I found that the green mark meant the positive terminal. Once I had assembled the speaker and crossover, I took some measurements using SpeakerWorkshop. I was surprised that the level matching of the drivers was right on and the overall response looked very good. I ended up adding the RC filter to tilt down the tweeter's rising output, but that was it. I did determine that the tweeter polarity needs to be reversed; with normal polarity, the null at the crossover point is very strong.
This is the SpeakerWorkshop simulation using downloaded .frd and .zma files.
And this is the response I measured. My mic roles off the upper range somewhat. I would suspect that the tweeter goes well above 15K Hz. The green trace is with the tweeter connected with normal polarity and without the RC component added to the high pass. The lower black traces are with the RC filter.
This is a BassBox simulation of the enclosure. The net volume is 0.1 cu.ft. (~2.8 liters). F3 is 89 Hz. Qtc is 0.93 when heavy acoustic stuffing is used.
The enclosure is as simple as it gets although care must be taken to locate the driver cutouts on the baffle. In actuality, I used two enclosures I originally built for a pair of dB41s and ended up not completing. So, I cut the baffle off, chiseled out the slot port, and attached a new baffle. I had to make the third speaker for the center channel from scratch, but it only took a couple of hours. I wanted a small speaker, and this is about as small a baffle as can be used and still fit the drivers. It is a tight fit though. One could increase the width and height by 1/2" each and have a little more room to breathe.
The spacing between the tweeter and woofers is only 1/8" so some care is warranted in locating the holes.
You can assemble the crossover on a small piece of Masonite/hardboard. There is a pair of slots on the back of the terminal cup for this to slide into.  I epoxied the components to the board then connected and soldered when the glue set. Something else I did different was to solder lead wires to the drivers before mounting them. Then I connected the wires to the crossover.
You'll need to use both sides of the board. Here's the other side.
Parts and Cost for One Speaker Item Quantity Cost/Each Price Hi-Vi B3N Woofer 2 $9.58 $19.16 Audax TM025F1 1 14.10 14.10 3/4" MDF, 4' by 8' Sheet 1/4 5.00 5.00 Polyfil Stuffing, 20 Ounce Bag 1 2.89 2.89 Terminal Cup 1 3.95 3.95 Crossover Parts (Parts Express part number)       C1 (027-420) 3.3 uF 1 1.77 1.77  Ce (027-418) 3.0 uF 1 1.67 1.67  C2, Cz (027-348) 22 uF 2 .75 1.50 L1 (255-218) 0.3 mH 1 2.39 2.34 L2 (266-814) 0.4 mH 1 3.91 3.91 Rs, Rp, Rz (016-8.2) 8.2 ohm 3 .39 1.17 Re (016-2) 2 ohm 1 3.50 3.50 Grille Cloth 1/8Yard 2.00 2.00 Grille Guides, Small 3 1.90 1.90 Glue 1/8 Bottle 4.00 2.00             Total $66.86 Notes:
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