| Cyburgs Needle TQWT
DIY loudspeaker with Visaton FRS 8 driven by the LM3875 Gainclone Amplifier |
| The
speaker was designed by Berndt
Burghard and the plan is his copyright. All the information presented
here may be used to make speakers for personal use. Commercial use is
at Berndt's discretion. Here is Berndt's original plan and instructions, repeated here with his kind permission.  Cyburgs - Needle Floor standing speaker for Visaton FRS 8 or Tangband W3-871S (for Tangband use notch filter; C = 6.8 mF, L = 0.56 mH, R = 6.8 Ohm, all in parallel and in the positive cable) Material can be MDF or Chip Board, all dimensions in Cm. Assembly; make the cut out for the driver in A, (radius 3.6 Cm), make the cutout for the terminal you are going to use in B, put one side S on the workbench and mark the centre line, glue on A & B, the apply D at right angles to A, glue C in flush with D (either plane the angle or use lots of glue) and make sure that the other end is on the centre line, close with second side S. Damping is applied applied between A and C, tighter in the lower part and looser into the bend. The part between B and C remains undamped, glue top board E, glue base F, if you have children or cats make the base larger. This plan can be used and distributed freely for private use, commercial use is restricted. No warranty for whatever. Have fun. Experiences, ideas and photographs always welcome. mail to: cyburgs AT a1 DOT net |
| I'm Jim Read I live in NE
Derbyshire in the UK and was so impressed by Berndt's description of
his
design that I decided to make a pair for myself. I am at the
stage where I can listen to them but they are not quite finished, as
soon as I am happy with the stuffing I will glue the sides on,
chamfer the edges and varnish them. If anyone wants to contact me my
email is: jemraid AT
btinternet DOT com |
||
 To make it easier
for me I
altered the original plan so that only two widths of timber would be
needed to make the boxes. The bases can be made from the offcuts left
over after making the speakers.I bought a sheet of 12mm MDF from B & Q 1220 X 2440 and had it cut into 5 off 200 X 1220 and 8 off 100 X 1220. This gives plenty of spare in case of mistakes, the cost including cutting was £12.38.
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| I used the Visaton
FRS 8 drive units and in the UK they can be purchased from CPC Ltd part
of the Farnell Electronics group, mine cost about £20 for the
pair including postage and VAT. Start by drawing out the plan on a couple of the sides, check the dimensions from each other e.g the gap under 'D' should be 25 mm. Cut the lengths and glue them in place with white woodworking glue. I've illustrated this with a few tricks I use, I haven't got lots of expensive tools and have to use whatever is to hand. |
 |
 On the left is the speaker assembled with one side held on with Blue-Tack. Above is just before I put the side on, I twizzled the Blue-Tack into strips and then stood on the side to press it down. This seals and holds it in place, so much so that I needed the overhang at the back to prise it off. |
 Above is a close up of the top with the Blue-Tack strips and the filling which is pillow stuffing, thicker at the bottom of the taper and thinner up towards the drive unit. |
 Here you can see how I mounted the FRS8, doing it like this means I can change over to another unit fairly easily. The hole was cut out very carefully using a jigssaw fitted with a very thin metal cutting blade. |
 View of the top of the box showing the overhang at the back. |
 The cutout in A this was made by drawing around the drive unit flange and cutting on the outside of the line with a jigsaw. |
 |
 A few gluing tricks; the large heavy housebrick, the old transformer resting on the square, and the strong elastic. |
 |
 Two views of the finished speakers, I chamfered the front edges of the boxes and did the same on the edges of the drive unit baffles. I varnished them with some Ronseal pine coloured varnish, three coats of this and then did the chamfers and edges with some clear varnish I bought from the local pound shop. You may have noticed that I did glue another piece on top of the boxes, it did vibrate a bit but I do think it looks better with this piece on. I must say that I feel quite pleased with the result and will now polish them with some wax. |
| What
does it sound like? My first response was, this must be the quart out of a pint pot.! I did expect it to work I didn't expect the amount of sound especially from a 3" driver and this while listening in mono!!. I would recommend anyone to make a pair, it makes an ideal project for those like me who find woodworking a chore rather than a pleasure. I've used them for 4 years now and I'm thinking about trying another driver, I see that Visaton have brought out a more efficient version of the FRS 8 suffixed 'M'. I might try those or if I care to splash out more money some of the units mentioned in the DIYAudio Needle Thread which now runs to 500+ posts. |