I’ve just delivered these to Uncle Eli’s apartment and I miss them already. These compact ‘monitors’ are rear-loaded horns built from the most reasonably priced materials. Two sheets of MDF from Home Depot and the famous Radio Shack 40-1197 full range driver. Total cost is under $50 and a couple of weekends. These were my first horn project and probably will not be my last. I have heard some wonderful things with this design! But I have also heard some ‘interesting distortions’ which may enhance the sound quality of this design.
First, I would like to thank Pit Hinder who I met at the Full Range Driver Forum. The plans for the BK101 are at the following url:
Thanks Pit! I converted the measurements into inches and began planning.
As I built the cabinets I noticed this design has plenty of structural rigidity built right in. You don’t have to add any braces anywhere (except for maybe the rear wall of the cabinet). Once the cabinet is built it is very sturdy and solid to the ‘knuckle tap’. After completion, I spray painted the cabinets with black Fleckstone which provided and attractive and quick finish.
"Interesting Distortions"
I always built sealed or ported designs. Each time, I worked harder to prevent any vibration the cabinet may contribute by adding braces or extra panels of wood. In this case, I noticed the cabinet made a distinctive contribution to the overall sound. This, I believe, is the horn sound people either love or hate.
There is a reverb to the sound. I can hear the instruments fading away more clearly. There is a ‘live’ character to the sound. Impact is stronger with the horns than if the same drivers are placed in sealed or ported designs. Cabinet ‘contributions’ are apparent on all of the CD’s I listened to. Which can be a disadvantage! After a few days living with these speakers, I became accustomed to their sound. Going back to ‘regular’ speakers immediately revealed distinct differences and weaknesses in standard speaker designs. ‘Horns are superior.’ I thought. And they are! But the question is ‘Will everyone agree the horn sound is best?’
The horn made the speaker more sensitive too. The added sound of the horn is easily discernable. It extends into the bass and midrange adding its ‘interesting distortions’. This raised the overall loudness of sound and balanced out the driver. Since the RS 40-1197 is lean in the bass and lower midrange, this is a welcome addition.
Horns are harder to build. Probably why many commercial speaker designs don’t use them. But they are worth the effort if you want a more lively, dynamic, open sound. If you feel your speaker’s always sound small and closed in, I believe you will enjoy the horn sound.
The Sound
Good. Sure it’s better than anything at the local hi-fi shop up around $800/pair give or take. But the box does take a long time to build. And the driver, although cheap, can sound really terrific. Balance is fine, leaning toward the bright side. Midrange is forward and direct. It can sound very realistic with vocals and small-scale bands. Ella sounds wonderful! Bass is lacking (but much better than with sealed and ported designs I’ve heard with the 40-1197) and ultimately requires a subwoofer to sound its best. The top is clear and shimmers nicely but ultimately requires a super tweeter. If you can get past these flaws (and it’s pretty easy) there are plenty of positive things to report!
These speakers make music fun and exciting! They image beautifully! And with just a few watts they light up a small to medium sized room with sound. They are small enough to tuck into corners and light enough to experiment with room placement. All considered, they are very nice monitor speakers that compete very favorably with typical 2-way designs but with better imaging and a more natural (but forward) midrange. As is, the design is good.
Conclusion
For a hobbyist interested in finding out about the ‘horn’ sound, this is an inexpensive and fun project. My three and a half year old son helped me assemble and glue the pieces together. He also helped me paint them (pictures of the finished speaker are much more attractive than the raw MDF – picture to come soon). Ultimately I feel they need a sub and a super tweeter to sound their best. As is, they are pleasant speakers that communicate music in a very natural way. If you have a small to medium sized room and prefer a fast and forward sound or if you have a low power tube or solid state amp and want inexpensive, great sounding horn speakers, the BK101 with 1197’s could be just right for you.
When you decide to build bigger, more expensive ones, you can pass these along to your uncle.
