[matevana]

Nope!  Not those F-bombs. "F" as in flat-panel and designed to ride the backs of the Mini H-Bombs (see separate H-Bomb build thread here) ->  http://www.audiocircle.com/index.php?topic=119359.msg1255174#msg1255174.

The narrow panels image very nicely. Each F-Bomb sports an Usher 8137A 8" Mid woofer and an Usher 9950 1 1/8" dime tweeter. Crossed passively at 2 kHz. (2nd order electrical) they start to peter-out around 120Hz where they meet the H-Bomb, a 10" Usher woofer in an H-Frame bi-amped alignment. The tweeters are offset and mirrored to skew diffraction artifacts, and the base is designed to help align each of the drivers acoustic centers. The baffles are made of figured maple with roundovers on 4 sides, and the base is poplar and bamboo.  They can either sit on top of the H-Frame or sit on a separate bridge for complete isolation. The upside-down woofer/tweeter mounting allows for the elimination of two additional passive components and sounds great at a typical listening height, eliminating any remnants of fatigue that might otherwise be present.

With a bit of roll-off compensation they sound great on their own in a bedroom or office environment. When tandem mounted with the biamped H-Bombs, they require no additional EQ. The H-Bombs are filtered by a set of Harrison Labs 70Hz F-mods, passive inline crossovers.   

[bummrush]

Is a price available?

[matevana]

Is a price available?

These speakers are DIY and my own design. I was able to buy the drivers used for a total of $150. The crossover components were another $45 and the remaining baffle stock was less than $50. Depending on how you look at it, one's "time" may be the biggest cost factor, but most if us enjoy the work and don't see it that way.

[Brad]

Cool idea and nice work.  Any estimate on the efficiency?

[matevana]

Cool idea and nice work.  Any estimate on the efficiency?

As a freestanding speaker they measure around 87 dB 1w/1m. I run them in tandem with the bi-amped H Frame woofers that are about 86 dB 1w/1m with the inline passive crossover, or about 89 db if you were to use an active set-up and there was no insertion loss. 

[jimbones]

Thats what I was looking for a pair of OB sattelites if you will!! If I wanted to go down a bit more in Fr (say 100hz) what would you recommend as a driver and how big a panel? Those look nice on the table!

[matevana]

Thats what I was looking for a pair of OB sattelites if you will!! If I wanted to go down a bit more in Fr (say 100hz) what would you recommend as a driver and how big a panel? Those look nice on the table!

If you are looking to keep the small form factor (which I really like) you will likely need to go to a 10" mid woofer. An alternative would be a slightly smaller woofer with higher excursion and EQ but I don't favor that approach. The Dayton PA-255-8 is a good example of an inexpensive 10" driver capable of reaching below 100Hz in OB, with decent mid range qualities. It is the featured mid range driver in my Hestia-SL project, also on Audiocircle. This driver has a 95 db efficiency, a Qts near 50 (my pair measure 56) and an Fs of 46 Hz. Best of all, a pair will only set you back around 90 bucks. I would cut to the tweeter between 1800 and 2000 Hz, so you would want to select a tweeter with an Fs of 1000 or less. Even in a small form factor baffle, you should not have to strain to hear quality bass output. My baffles measure 10" x 15" in the F-Bomb project.

[persisting1]

I've always been a big fan of Usher drivers, but I have yet to hear this 8" kevlar.

Is this driver available anywhere? It's no longer sold on PE.

[matevana]

I've always been a big fan of Usher drivers, but I have yet to hear this 8" kevlar.

Is this driver available anywhere? It's no longer sold on PE.

That's a good question. I own one original pair that was purchased from PE, and a second pair that I purchased used on eBay. It's really a shame. Not only are they great drivers, but they are great drivers for OB. Every Usher driver I have ever used has virtually no motor noise, which is so important in open baffle designs. Not true for other quality drivers such as SB Acoustics, Seas and Aurum Cantus. They seem to be hit or miss.

There is a black version of the 8137a sold in Europe. It is basically the same driver with a nice black kevlar/carbon fiber cone. I would love to try those some day. I will buy Usher drivers on speculation, knowing that I can put them to good use.   

[jimbones]

I'm willing to go bigger on the baffle say 14x24? a 10 inch and dome would be good but would I get beaming from the mid-woofer?

If you are looking to keep the small form factor (which I really like) you will likely need to go to a 10" mid woofer. An alternative would be a slightly smaller woofer with higher excursion and EQ but I don't favor that approach. The Dayton PA-255-8 is a good example of an inexpensive 10" driver capable of reaching below 100Hz in OB, with decent mid range qualities. It is the featured mid range driver in my Hestia-SL project, also on Audiocircle. This driver has a 95 db efficiency, a Qts near 50 (my pair measure 56) and an Fs of 46 Hz. Best of all, a pair will only set you back around 90 bucks. I would cut to the tweeter between 1800 and 2000 Hz, so you would want to select a tweeter with an Fs of 1000 or less. Even in a small form factor baffle, you should not have to strain to hear quality bass output. My baffles measure 10" x 15" in the F-Bomb project.

[matevana]

I've used the Dayton 10" with the Hestia-SL project and in that context beaming wasn't much of an issue. Of course it cuts to a midrange driver below 1k Hz. You could try one in a test baffle and see if it's a problem. A lot of this will depend on near field/far field, your listening position, the size of the desired sweet spot, etc.