The Debertin-Goldwood DC-01 (DG DC-01)

A Budget Floor-Standing Loudspeaker with Upward-Firing Drivers

The Debertin-Goldwood DC-01 loudspeaker is an effort to build a floor-standing speaker employing drivers that are placed on an angled top panel. The box design was inspired by the original EPI 201 as well as a subsequent design by Winslow Burhoe for the Direct Acoustics model. I started with the idea of developing something similar in design to the EPI but with only a single 2-way woofer-tweeter module.

The basic cabinet shape and size was determined and the cabinets were constructed before the drivers were chosen (always dangerous). I then faced the problem of trying to find a woofer and tweeter that would work with the rather large cabinet volume. I considered using both 6 ˝ and 8 inch woofers, but quickly discovered that a 8-inch woofer was going to crowd the angled baffleboard, and further, finding a tweeter that would be suitable to cross over to an 8-inch woofer was going to be difficult. At this point I settled on using a 6 ˝ inch woofer.(The saw illustrated wses a Black and Decker "Shopmate" and works like a "poor man's Radial Arm Saw!

The cabinet volume is rather large for a 6 ˝ inch woofer. The external measurements are 13 inches wide x 10 inches deep x 19 inches tall at the front, but at the back the height is 24 inches. The cabinet is made from 3/4 inch MDF, but this still results in an internal volume of approximately 1.2 cubic ft, or 33.8 liters. This is a very large cabinet volume especially for a 6 ˝ inch woofer!

Originally I thought I might use the Dayton drivers employed in the BR-1, but I quickly concluded that they were not a good choice in that in a sealed configuration the Dayton woofer called for a very small volume cabinet and even if vented they needed a cabinet volume of around a half cubic foot.

In using the speaker wizard I did discoverd that the were a couple drivers that would work, but some were outside the budget I had for the project. The one driver that did keep popping up was the inexpensive Goldwood 6 ˝ inch woofer, at only $11.70-even less expensive than the 6 ˝ inch Dayton Woofer.

Meanwhile, I got sidetracked and decided for the fun of it to build a pair of Dayton BR-1 units. Having priced out the parts from the kit individually I concluded that the kits were a bargain in that the pre-assembled boxes were essentially tossed in for free. I also thought it would be fun to have a pair of BR-1's available to compare directly with my own design.

The BR-1 and Dayton woofer is set up to operate in a vented box of 0.55 cubic ft. The Dayton woofer is really not well suited to a sealed design in that it calls dor a very tiny box of less than a quarter cubic ft, and then it ends up with a resonant frequency in the mid 70 Hz. So one COULD build a sealed system using the Dayton woofer but it would not have a lot of bass.

In contrast, the Goldwood woofer is designed for a sealed box, and a rather large one. The Goldwood woofer might be described as a "Fairly High Q" woofer, with a Qts at 0.61. As a practical matter, this means that it is likely to produce a boomy upper bass if put in a small sealed box of the size of the BR-1. And using the Goldwood in a vented box of any size is "not recommended".

The specifications on the Goldwood GW 206/8 (PE 290-305) woofer are:

Specifications:* Power handling: 90 watts RMS/180 watts max * Voice coil diameter: 1-1/2" * Frequency response: 60-3,000 Hz * Magnet weight: 20 oz. * Fs: 62.5 Hz * SPL: 87.3 dB 1W/1m * Vas: .42 cu. ft. * Qms: 3.50 * Qes: .97 * Qts: .75 * Xmax: 3.5 mm * Net weight: 3 lbs. * Dimensions: A: 6-1/2", B: 5-5/8", C: 3-5/16", D: 4", E: 1-1/4".

In contrast, the specifications for the Dayton woofer employed in the BR-1 are

Specifications: * Power handling: 50 watts RMS/75 watts max * Voice coil diameter: 1-3/8" * Voice coil inductance: 1.40 mH * Impedance: 8 ohms * DC resistance: 6.0 ohms * Frequency response: 33-4,000 Hz * Magnet weight: 15 oz. * Fs: 33 Hz * SPL: 88 dB 1W/1m * Vas: .98 cu. ft. * Qms: 2.75 * Qes: .37 * Qts: .33 * Xmax: 3.15mm * Net weight: 3 lbs. Dimensions: A: 6-1/2", B: 5-3/4", C: 3-3/16", D: 4", E: 1-3/16". *

About all these woofers share in common are the diameter. Clearly the Goldwood woofer, with its Fs of 62.5 Hz, will not go as low even in an optimal enclosure volume as the Dayton woofer, with an Fs of33 Hz. The other major difference in in the Qts parameter with the Goldwood at 0.75 and the Dayton at 0.33. This suggests to me that the Goldwood woofer in a sub-optimal-sized enclosure could sound boomy.

But, so far, so good. It's clear that the Goldwood might be happy in a quite large sealed enclosure, which is what I was in the process of building.

I then did some WinISD modeling to compare the Dayton woofer in the vented BR-1 box versus the goldwood woofer in the Box I had under construction.

The following figure illustrates the differences. The orange colored line shows the Dayton woofer in the BR-1 enclosure. The yellow line is the Goldwood woofer in a sealed enclosure of the volume I am building here.

The tendency of the Goldwood woofer to get boomy around its resonance was dealt with not only by the enclosure volume but also loosely filling the lined enclosure about 2/3 full of poly fiberfill

Once these decisions were made, then the question was what tweeter to pair with it. In keeping with the budget design Goldwater had a tweeter (GT-302, PE 270-170) that listed at only $1.95 and was a Mylar dome and ferrofluid cooled. It looked like an offshoot of several Audax Mylar models. And the diminutive size meant that it could be mounted very close in the baffle to the woofer-usually a good idea for the driver blend. Here are the specs on the Tweeter

Tweeter SpecificationsAvailable in shielded and non-shielded * Ferro fluid cooled * Power handling: 30 watts RMS/45 watts max * Voice coil diameter: 1/2" * Impedance: 8 ohms * Frequency response: 4,000 - 19,000 Hz * Magnet weight: 1/2 oz. * Fs: 2,600 Hz * SPL: 90 dB 1W/1m * Net weight: 2 oz. * Manufacturer part number: GT-302/GT-302S * Dimensions: A: 2-3/8" x 2-3/8", B: 1-15/16", C: 7/8", D: 1-7/16", E: 5/8".

At that point it was time for a crossover design. The frequency response curve for the 4 ohm version of the Goldwood woofer with the same parameters showed up on the PE Website rather late, well into the cossover design, and it was NOT reassuring. The problems included not only a rather high resonant peak centered around 200 Hz , very sloppy performance and a 10 db peak at 4500 Hz, and a funny-looking 10db drop at around 1500 Hz. Clearly this woofer is not a candidate for a simple 6 db per octave crossover.

But this still being a budget system, I had no desire to try to build a crossover where the parts cost more than the woofer, and further, since these speakers were really "test mules" for trying different drivers, I didn't want to get bogged down designing elaborate notch filters or contour networks specific to this woofer. I wanted to keep the design relatively straightforward. I settled on a Linkwitz-Riley 12-db per octave design with a couple of twists. I set the crossover frequency for the woofer at about 3,000 Hz, but the crossover frequency for the tweeter at 4,500 Hz, maybe a bit high, since I also added a 4-ohm, 5-watt resistor in series with the tweeter, which not only pads down the tweeter but has the effect of increasing the tweeter impedence. The final tweak was a continuously-variable L-pad on the tweeter to alow for fine tuning. In looking at this design there is some chance that I have managed to create a response dip in the 3,000 -4500 Hz range, but careful study of the odd peaks in the upper frequency response of the woofer suggests that perhaps this would not be a bad idea. While lacking elaborate test equipment, I will certainly be listening for response irregularities in that region.

The crossover boards were made from two scrap pieces of 5 ˝ inch wide x 5 ˝ inch long 3/16 inch poplar (Lowes) That just fits through the woofer hole with a fraction of an inch to spare. First, I sketched the crossover design on the poplar with a sharpie, to determine where the wires and parts would go. I then salvaged the bare copper wire from 16-gauge electrical wiring, and "sewed" the wire through the board to create the connections to be soldered. Thus, not all the connections can be seen from the top of the board. The heavy wire works pretty well in that it gives a secure spot to wind each component wire around, and acts as a heat sink to protect the components when soldering. The wires goint to the woofer and tweeter were salvaged from 16 gauge extension cords that have bad ends (a favorite source for cheap, heavy-gauge wire. Inductors were attached with a generous amount of hot glue

Ok so back to the cabinet assembly. Once the front, back and sides of the cabinets were complete, these were screwed and glued together with liquid nails (sturdy but quite a cleanup mess) the next step was to install the angled top panels and drill holes for the drivers, L-Pad and terminal cup. I had purchased MDF designed for shelving with a wood-grained surface, in hopes that some of this wood grain would show through, but this idea did not work wery well, and I ended up sanding nearly all of it off. What did remain, however was the rounded shelf-edge lip, which gave a nice routed appearance at the front of each side panel.

The top angled panel is a bit difficult to get even. You will likely need some wood filler, and I found my belt sander was an invaluable tool for smoothing the angled edges flush.

I am not too fussy about hole drilling. The tweeter fits nicely in a 2-inch hole cut with a hole saw, as does the Terminal cup. The L-pad was another matter. I initially cut a hole for it with a 1 1/4 inch drill but it was a real pain to try to get those tiny nuts attached while holding the L-pad in place from the inside. So I eventually ended up enlarging the hole just a bit, so I could slip the assembled L-pad in from the outside. To firther seal, I took a cover from a liquid detergent bottle and glued that in from the inside, with a hole just large enough to pass the three wires through.

The hole for the woofer was cut simply using a pencil compas and a saber saw. Its not absolutely round, but I did not intend to Flush-mount the woofer anyway.

I tend not to like to use woofer caulk so that I can easily swap out drivers. Instead I use 3/8 inch closed cell foam weather stripping, available at Ace Hardware. I had a bit of trouble getting the sticky side to stick to the sanded MDF, so I first laid down a very thin layer of woofer caulk, followed by the closed cell foam

The next step was to add cleats for the bottom. I decided I wanted a screw-on bottom that could be readily removed if desired for repairs or modifications were to be made. The cleats are 3/4 inch wide strips of MDF, screwed and glued into the inside. Cailk rather than liquid nails was used on the bottom, along with short screws.

Then the inside of the cabinet was lined with egg-crate foam mattress pad, with a second layer on the back side. Then time for a trial fit of the drivers and checkout of connections on the crossovers. I hooked both crossovers to the drivers and an amplifier as well as the L-Pad wiring, and everything seemed to work as intended An electric carving knofe is the best tool ever invented for cutting the foam

At this point I am ready for a trial fit of the drivers. Everything seems fine. Next, major cleanup of excess glue to get ready for priming. I primed using cans of gray spray paint, followed by coats of black satin spray enamel. I never was able to get the gloss even, so I have been giving them additional coats of a spray flat black. I have some e-bay genuine cherry veneer, and I may eventually try veneering just the front panel.

I am also planning on a baffle board made from quarter inch plywood that will tend to level the space between the woofer and tweeter, although the angled mounting seems to minimize the baffle board problems ordinary box speakers have.

Now for the final assembly! I used solderless connectors to install everything, with the idea that these may be modified at some future point in time. Then I did my initial checks by connecting a VOM to the terminal cup, in serach of approximately a 6-ohm resistence, which is exactly what it checked. Even better, I was getting pops and clicks from both woofer and tweeter, and the sound of these pops and clicks clearly changed as the L-pad level was moved. Everything was ready for an amplifier check, and sure enough everything worked just as intended.

How do they sound? Well, these are NOT similar to the BR-1's. The BR-1's can go deeper, and probably have smoother highs. But the DC-01 does have some redeeming features.

First is cost. If you use some household and scrap materials, a pair of these can be built for under $100 for everything-maybe WAY under $100. So if you place a zero value on your time these are about as low-cost as DIY speaker building gets, and the "DC" in DC-01 really does stand for "Dirt Cheap."

Angled Top Panel Clearly the most successful part of the design is the angled top panel ,mounting of the drivers, which both disperses the sound into the room but also help the drivers blend together to the point where they nearly sound as a single full-range driver-of course, the diminutive tweeter helps in this regard too.

Floor Standing A speaker like the BR-1 calls for stands, and once they are up on stands they are likely to be dominant in room decor. Further, one could easily spend as much or more than the BR-1 kit cost on stands. The DC-01, being sealed and floor-standing can be pushed back unobtrusively against a wall. Since the drivers point upward, they can even be hidden behind a silk plant-something you probably would never do with a conventional floor-standing box. Thus the WAF should be pretty high on these as they can be made to nearly disappear behind a couple of potted plants.

Efficiency and Forward Soundstage I would be the first to admit that in comparison with the BR-1 the DC-01 is a bit more of a "party" speaker. It's particular strength is in bringing vocals a bit forward, and plucked instruments of all sorts sound quite realistic. For those who think the BR-1 is "nice but a bit laid back" these, as might be imagined are a little less laid back. I don't think it's obtrusive, just a bit different.

In my view the $1.95 Goldwood Tweeter is a real winner in that its smoother than other Mylar domes I have heard and yet not quite a recessed as the typical silk dome. Further, as near as my ears have been able to determine, the crossover actually works as planned seemingly without any major oddities in the crossover region between 3,000 and 4,500 Hz. I think the low price of the tweeter has deterred DIYers from experimenting with it ("A $2 tweeter CAN't be any good") In my mind the big box and the fiberfill did a good job of minimizing possible boominess from the woofer, and shows it off to its best advantage. Pjay recently noted that "DIYers tend to prefer the sound of their own DIY projects to the sound of kits they have just completed building as well" Lest I be accused of that, I think the BR-1 is a fine speaker, and probably would have a lot broader appeal than these speakers would.

Reviews of the Goldwood Project Speakers from Dayton 2003 DIY

Goldwood drivers. They sounded way too good for the price. It just goes to show you that proper crossover work can make anything sound decent.

Winner of the “bang for the buck” contest

Major bang for the buck. Great for what they are.

Slightly forward balance, nice bass texture, good vocals.

Here is a photo of the Goldwood projects at the event

Concluding thoughts

Why did I build these? I lack any sophisticated test equipment to fine tune the design. It's not that I am short of speakers to which I can listen. In addition to the BR-1's I have EPI 100/Epicure 10s, Epicure 11's (a large vented box with a 6 ˝ inch woofer-these are in some ways my favorite). A pair of original large Advents (owned since new) Utah MK-17 that I tweaked the tweeters on, plus even crazier things like a pair of 3-way BSR/Dak "Thunder Lizards" with 15 inch woofers, So I'm not exactly short of speakers to compare.

Thanks to Parts Express for the driver illustrations and the woofer response curve!!!

David Debertin

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