You just can’t say it loud enough: the creations known as “Needles” have long ago become synonymous in the DIY world with the trick of pulling greatness out of small wide-range speakers. When we measured the small wide-range speakers from Dayton Audio, we thought of the Needle right away. Would they work well enough here, too?
The greatest fault of many wide-range speakers in the 4-inch category is their fairly high resonant frequency of more than 100 Hz in most cases. That also applied to most of the chassis elements we tried in the Needle cabinet. Below the “fres,” they just don’t put out any sound worth mentioning. You can imagine how happy we were when our impedance measurements for the two RS 100 models peaked at 79 and 74 Hz. After all, that’s almost 40 Hz lower than the products that made the Needle famous.
A stable die-cast basket with six screw holes and narrow bars, ventilation and phase plugs drilled from solid material are the shared characteristics of the shielded eight-ohm RS 100 S-8 and its four-ohm counterpart, the RS 100-4 without a shield. The aluminum membrane has a shiny black coating to protect it from noticeable resonance peaks in the upper frequency range, and the rubber surround material allows for a large lift. Of the two RS 100 models, we chose the 4-ohm version because it has the three-dB-higher efficiency level with the same amplifier output.
Approx. price: 30,00 EUR/USD
Item No.: 1381990
Measurements as a zip-file
||Air gap height:
|Pole piece hole:
||raised flat spider
|Voice coil former:
Anyone who simply uses other people’s intellectual property online can quickly earn a justified lawsuit from the rights owner. Although we were confident Berndt wouldn’t file a lawsuit against us, we naturally asked him whether we could use his Needle diagram for our Dayton project. “Of course,” he responded. We’ve known each other for years now, so we weren’t really surprised by his answer.
But you know how it is when you think you can do everything better – naturally we had to play around with the diagram a little bit, and we built the sides, lid and floor from 25-mm MDF, which gives the box more weight and stability. We didn’t change anything on the inside – well, except for the position of the insulating material. We cut a Sonofil mat into three strips, 10 cm wide. We put one in the front chamber and two in the rear chamber. The front strip and the top rear strip came together at the lid.
This kind of cabinet is known as a TQWT, or a Tapered Quarter Wave Tube. It does have a certain similarity with the structure for transmission lines, although in a different way. In general, the TQWT is a widening sound conductor whose closed end has a cross-section near the membrane surface. The cross-section increases at the open end by a factor of two to three. The channel length corresponds to a quarter of the wavelength for the desired resonant frequency of the TQWT. Unlike the TLs, the channel ends in an outlet with about half the area of the membrane. The conductor line can be constructed as a tall pillar or with a bend in the middle. The chassis is placed at a distance between one-third and one-half the length of the line from the closed end. The structure of the TQWT is based on a 1934 design by Lowther inventor Paul Voigt, which went down in the history of loudspeaker construction as the Voigt pipe.
Needle-cabinet assembly plan as a Sketchup-file
Reporting on the crossover for a wide-range speaker is not an evening-long production. As a rule, it consists of three parts that are connected in parallel in the signal path. Their function is limited to balancing out the volume increase caused by reflections on the baffle board by way of a controlled increase in resistance. The RS 100-4 also required this type of correction, since its frequency curve shows a long bulge from 400 to 5000 Hz. Here we had to make a moderate intervention, particularly including the area around 3 kHz in the reduction. The ear is sensitive to any exaggerations in this range, which it perceives as annoying and bothersome. I also could have worked on the peak at 18 kHz, but since it doesn’t even show up in the distortion curve and disappears with a small angle, I saved myself the extra parts. We saved the measurements for the two wide-range speakers used in the original Needle on our computer, which were recorded under similar conditions and even using the same hardware and software. The benefit in the bass range is clear from the much lower resonant frequency of the Dayton BB. In the overall curve, too, the American part has a much more balanced line, without the waviness of the other two chassis elements. Berndt used the loudspeaker responsible for the red curve without an anti-resonant circuit, and the other one with the circuit.
People who trick others are not normally popular folks, we agree whole-heartedly. But because the intentions were good, we have decided to absolve ourselves in this particular case. We had just made the Needles available for a listening test in the shop when the phone rang; at the same time, Michael walked into the studio. During the phone call, we turned on our KT 88, put “Acoustic Live” by Nils Lofgren in the CD player and played “Keith Don’t Go” without commentary. When we finally turned our attention to the visitor, he said, “If those had been around when I was building my Duetta, I would have considered them too.” Now, what you need to know is that a newly developed tall free-standing box happened to be standing next to the Needle, and Michael assumed it was responsible for our listening enjoyment. His incredulous face had a bit of the embarrassed look that one always has at being caught out, when we showed him where the cables were connected. “Oh well, you fooled me pretty well with guitar music, but if there had been just a hint of bass, that little box would have conked out.” But after the beginning of Patricia Barber’s “Use Me,” with a plucked contrabass and creaking strings very clearly hitting the wood, he was speechless. A day later he sent us an email: “…after I got home, I did a listening test with the Duetta right away, and sure enough: there was much more to be heard. Clear, airy high notes and a true, clean bass (but the fat one is really good at plucked basses). The Duetta was the right choice after all!! It’s like you once said: the missing parts are not disruptive; what’s annoying is the excess. (At least as long as there’s not too much missing.) Anyway, it’s a great sound for a very small price, that Needle with Dayton.”
Having gotten a taste for this little experiment, we continued to test our customers. We consciously and very intentionally did not take advantage of the fact that people don’t expect much from small boxes and are then blinded by the results. Our visitors were convinced that they were listening to large boxes, and they were far from complaining about any missing bass. Of course we kept the volume low enough that the little wide-range speaker wasn’t overwhelmed, but with four millimeters of lift you can get well above a reasonable living-room volume”. The voices, room and localization, the representation of quiet sounds even with a large orchestra, fascinated all of the listeners equally. In the end, Charly, without consulting his father first, said, “It’s outrageous how much it’s showing off!”
Of course we can’t accept this great compliment just for ourselves; we are only responsible for a small part of the boxes’ success. Berndt did the calculations for a terrific cabinet, without which the good work of Dayton’s chassis developers would only have resulted in a conventional shelf loudspeaker. It would have languished in a little box, once again heralded as the end of the squallbox. All of these fortunate circumstances coming together made for an incredible box at a small price. We’re sure you can settle it into your living room as a “can opener” for larger projects – just ask my wife.
||1 x Dayton RS 100-4
||16, 19, 22 oder 25 mm MDF:
| Enclosure box:
||90,0 x 19,6 (4x) sides
| Cross over:
||15,0 x 19,6 (4x) lid/ floor
||12 mm MDF:
||1 Matte Sonofil
||90,0 x 10,0 (2x) back wall
||87,5 x 10,0 (2x) front
||77,7 x 10,0 (2x) back divider
|Approx cost per box:
||4,2 x 10,0 (2x) bottom divider