G - GRS 10SW-4 T - Tymphany TC9FD-18-08 S - SB Acoustics SB19ST-C000-4 10 - 10" woofer The Bulldog is a fat, robust, and loveable speaker. This is a truly "rockin" monitor designed to allow all day long fatigue free listening to compressed and poorly recorded music. That's not to say it's going to transform these recordings into something they're not, but it will take the edge off while injecting some life into the mix. This speaker is capable of a very wide soundstage with focused imaging, if your room allows it.
The speakers should be spaced wide, with the offset drivers to the outside and a slight toe in. There should be at least a couple feet to each side wall. The design axis is on the mid, NOT THE TWEETER. That means you want your ear at midrange height. A 24" tall stand will achieve this height for most people.
The woofer alignment is aperiodic aka a "leaky sealed box". The woofer chosen has a fairly high Qts to Vas for a 10" woofer which normally requires a large sealed box. This alignment is an old fashion way of cheating the box size issue (see slide show at bottom of page). There is an impedance peak so it isnt truly aperiodic, but the level of the peak in both the woofer's response and impedance is reduced vs sealed.
This design was intended for the Iron Driver NY competition. That required use of the SB19 tweeter (iron driver), placement on 24" stands, a budget under $225, and a design that could easily be repeated by any DIYer. The prices of some of these drivers have gone up a few $ since January 2015 when I started this design, but I still come in under $200! I took every opportunity to simplify crossover requirements with my design considerations. I feel like I have met my goals.
The basic box construction details below. A pair of speakers should be mirror imaged. All dimensions below are in inches. The tweeter is offset 1" from the center line and the mid is offset 2" from the center line. The offsets were chosen based on optimizing driver diffraction effects for the given baffle dimensions. The driver height tab gives you the driver locations from either the top or bottom of the baffle.
This is a blended far field (1 meter) with woofer near field measurement 1/48 octave. All measurements are centered on the midrange driver. So yes the bass is hot, sue me.
Below we see horizontal off axis response 1/48 smoothing at 24 in. This was measured to the far side of the mid on the baffle. This speaker sounds best with the offset drivers to the outside. The below measurement should show why with an ultra wide and constant dispersion pattern.
Below we see a response comparison with the mid wired opposite polarity of what the crossover requires. This is one way I verify my design is working as intended. This measurement was taken at 24" which is too close to see an optimized reverse null as I optimized the response at 2.5 meters. (the cutoff at 16khz is due to an issue with my measurement setup that has been solved)
Here we have system distortion showing the top notch performance of the mid and tweeter. The woofer is showing a less advanced design, but it is not objectionable.
Impedance dips low from a 4 ohm woofer with a massive cap in the low pass circuit, but it is not brutal. Note that phase is also at 0 degrees at the imp min (good). I drove this speaker extensively at high spl with a Yamaha A800 receiver which is not rated for 4 ohm loads without issue. I have also tested with a couple of dirt cheap chip amps, again without issue. Yes this speaker likes power and can handle it well, but it should also work with most amps just fine.
Below you can find a slide show full of build details. This should make construction of the aperiodic box loading, and mid chamber fairly clear. Please view every picture for comments on various details.