DIY Back-Loaded Horn Speaker Kit

DIY Back-Loaded Horn Speaker Kit

Like many of you, I love speakers, but my woodworking skills are mediocre and I don’t have a suitable setup and proper tools for loudspeaker enclosure building. As a result I am often browsing the many DIY speaker kits that are available. When I came across the Tang Band D4-1 DIY Horn Speaker Kit, which is pre-cut (no cutting or drilling = no saw dust), pre-finished (no painting or staining) and looks like it goes together much like ready-to-assemble furniture, I figured it would be the perfect kit that can be built indoors as winter already had a firm grip on Winnipeg.

Exlpoded View - Tang Band D4-1 DIY Horn Speaker Kit

Photograph 1: Exlpoded View – Tang Band D4-1 DIY Horn Speaker Kit

Tang Band D4-1 DIY Back Horn Speaker Kit

One week after ordering the speaker kit arrived via UPS from a warehouse in California in two boxes with shipping weights of 11 lbs (5kg) and 49 lbs (22.3kg). The speaker kit was packaged very well and there was no damage to any parts. The smaller box contained the speaker drivers, hardware, damping material, hex keys and instructions.

Photograph 2: Tang Band D4-1 Speaker Kit Parts

The enclosure comes as a flat pack which was extremely well packaged, double boxed with durable foam padding. The speaker enclosure consists of CNC cut HDF (high-density fiberboard) and the exterior faces are pre-finished with a low-gloss clear finish that I could not identify.

Photograph 3: Ready-to-Assemble Horn Enclosure Speaker Kit

Technical details specified by the manufacturer are noted in the Tang Band D4-1 Speaker Kit Datasheet. Examining the enclosure (Photograph 1, exploded view) you will note that the horn is not the typical back loaded horn. After the compression chamber there are two differently shaped expanding throats which later rejoin at the mouth of the horn (resulting in a long folded horn in thin sections).

Tang Band W4-1617 Full Range Speaker Driver

The D4-1 speaker kit comes with the 4″ (100 mm) Tang Band W4-1617 full range speaker driver. The driver is constructed on a die-cast aluminum basket with a large under-hung neodymium magnet motor system. The cone is paper made from sugar-cane fiber and mounted with a rubber surround. Full technical specifications are available on the Tang Band W4-1617 driver datasheet. The noted sensitivity of 89dB / 1W / 1m is optimistic – I measured about 86 dB with a radio shack 33-2050 sound pressure level meter.

Photograph 4: Tang Band W4-1617 Speaker Driver


Construction – D4-1 DIY Horn Speaker Kit

Enclosure construction is ultra simple. If you have built ready-to-assemble furniture before you are likely over qualified. The kit comes complete with everything you will need except for an optional soldering iron which we will discuss later on. The step-by-step instructions are very simple to follow with plenty of illustrations. All of the parts are clearly labeled with a lettered sticker and this is how they are referred to in the instructions. The photos below show the basic idea of the enclosure assembly. Be sure to read through the instruction (14 pages / 10 minutes) before you get going. I used a marker to label the pieces which are only marked on one side. There really are no tricks to construction, just follow the instructions. The one thing to watch out for is the damping material. Only peel back a little of the backing to expose the very sticky-back felt to get you started. Tack that down and peel as you go. The large damping sheets are floppy and if they come together it may make a mess much like when packing tape comes together. You want the hex screws to be tight, but don’t over tighten them.

Photograph 5: Tang Band D4-1 Horn Speaker Kit Construction 1


Photograph 6: Tang Band D4-1 Horn Speaker Kit Construction 2


Photograph 7: Tang Band D4-1 Horn Speaker Kit Construction 3

Photograph 8: Tang Band D4-1 Horn Speaker Kit Construction 4

Photograph 9: Tang Band D4-1 Horn Speaker Kit Construction 5

Photograph 10: Tang Band D4-1 Horn Speaker Kit Construction 6

Photograph 11: Tang Band D4-1 Horn Speaker Kit Construction 7

The connection from the binding posts to the driver can be made in a number of ways. The simplest being soldered – if you are not familiar with soldering a search for “soldering tutorial” will provide plenty different tutorials. Alternatively one could use a crimping tool with a blade disconnect and ring or spade terminals. Make sure you have a good connection from the binding posts to the driver. The red binding posts should go to the speaker tab marked “+”.

The kit goes together quickly. I put the two speakers together in one afternoon while watching football. The overall dimensions of each enclosure is 162 mm (W) x 320 mm (D) x 500 mm (H) (about 6.4″ x 12.6″ x 19.7″) and each finished speaker weighs 10.9 kg (24 lbs). There are four metal feet at the bottom of the speaker. Finished photos of the speakers are shown below.

Photograph 12: Finished Tang Band D4-1 DIY Horn Speaker Kit

Measurements – Tang Band D4-1 DIY Horn Speaker Kit

After about two weeks of use I measured the impedance of the D4-1 speakers using the Dayton Audio Woofer Tester 3 (with no filters on the driver). The impedance (and frequency response) of the D4-1 speaker from the manufactures datasheet are shown in Figure 1. Figure 2 shows the measured electrical impedance (blue) and phase (red).

Tang Band D4-1 SPL and Impedance Response

Figure 1: Impedance and Frequency Response from Manufactures Datasheet

Figure 2: Impedance and Phase measured with Dayton WT3

The measured impedance is similar to that noted in the Tang Band datasheet. The impedance never dips below 7 ohms and is above 8 ohms for most of the audio spectrum. At the same time, the phase angles are only slightly capacitive so this speaker will present a very easy (tube friendly) load for amplifiers.

The small wrinkles in the impedance between about 270 to 620 Hz imply the presence of resonances. Investigating with a stethoscope the mode at 270 Hz is relatively strong on one side panel, but is not audible over the speakers output.

The near-field frequency response of the Tang Band D4-1 Speakers was measured using a Radio Shack 33-2050 SPL Meter. Figure 3 shows the summed near-field response measured at the driver and the mouth of the horn. The in-room response was measured with a Behringer ECM8000 microphone and is shown in Figure 4. The in-room response was measured in an open, carpeted room, about 4.6 x 6 m (15′ x 20′) with a 2.4 m (8′) ceiling at a distance of about 3 m (10′) from the speaker. The speakers are at least 1 m (3′) from any wall boundaries.

Figure 3: Near-field Frequency Response – Tang Band D4-1 Speaker Kit

Figure 4: In-room Frequency Response – Tang Band D4-1 Speaker Kit

In the near-field plot (Figure 3) the sub 500Hz response hump is the horn action. The idea here is the frequency response will flatten out in the far-field with the baffle difraction step which for a 162 mm wide baffle will be centered around 725 Hz. The intensity of the horn action appears to be somewhat exaggerated due to placement of the microphone at the horn mouth. The plot of the in-room response shows the havoc that the typical room will have on the response at the listening position. The room is often the weakest link of a hi-fi system. The bass response is typical of what would be expected from a 100 mm driver in a compact enclosure. Pulling the speakers into the corners of a room should provide some additional bass reinforcement. Pulling the speakers up against the back wall may also help extend the bottom end a tad. Given the small height of the speakers some will be tempted to raise the speakers to ear level using stands. This is not recommended as coupling with the floor is needed for the low-frequency response. Experiment with placement in your room to find the best results.

Listening Impressions – Tang Band D4-1 DIY Horn Speaker Kit

To the important part – how do the speakers sound? In short, very good. The sound is not boxy and larger than expected given the small driver and compact enclosure. As expected there is not much deep bass, but the bass that is present is very clean and accurate. For low-end reinforcement the speakers can be coupled with a subwoofer (a 50-60 Hz / 12dB crossover point worked well with my 10″ DIY subwoofer). With only a single driver (point source sound) the imaging is very accurate and there is also plenty of fine detail. I have been using the speakers with a pair of OddWatt Audio KT88 push-pull tube amplifier kits (25W) and they sound wonderful. About 6 to 8W of power will be sufficient for small to medium size rooms.

Photograph 14: Finished Tang Band D4-1 DIY Rear Horn Speaker Kit

Overall, the Tang Band D4-1 Horn speakers kits make for very nice sounding speakers. The kits are ideal for hobbyists who lack the woodworking skills / tools / space, or those who are not in the mood for saw dust or paint fumes. Go ahead and give them a try – they sound great and are fun to build.

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