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Betsy/Boomer OB speaker kit

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Hello Wild Burro Audio Lab fans!

Oftentimes simpler is better. Nothing is simpler than placing a Betsy on an open baffle to enjoy music. But the Betsy can use help in the lower octaves so I designed the Boomer. The Boomer is an easy way to add bass. It’s an Alpha 15 woofer mounted close to the floor that’s powered by an external subwoofer amp. While taking up the same amount of floor space, the addition of two 15 inch powered woofers really fills out the bottom octaves producing full, warm, rich bass that’s adjustable to taste using the amps separate volume and crossover controls. Once you listen to the Betsy with the Boomer you will find it very difficult to enjoy the Betsy, or just about any other speaker, without the added bass to round out the sound. If you have any questions about the Boomer don’t hesitate to ask.

Open Baffle Speaker - Betsy and Boomer Open Baffle Speaker Kit

Godzilla
 

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There is a surplus store out at this end of the state that carries reasonably priced motor run caps. A first order high pass could really extend the dynamic range of the Betsy +Boomer, and it would get the slopes of the woofer and FR a little closer by making the Betsy rolloff acoustically second order or so (6db rolloff from the baffle +6db from the crossover). I think 120uf would be about right on the Betsy, and the simplest way to accomplish that with common sizes appears to be two 60uf caps in series. A nice 60uf motor run is $6.50, and you'd need four. If anybody is interested, let me know and I'll grab you a quad. I'd be happy to pack 'em up for free, provided you reimburse me for the caps and shipping. Motor runs are big, but they are film in oil, which will sound much less bad than a cheap 'lytic. Motor runs also live forever, and if you don't like them on your speakers, they are great for tube amp power supplies. They are also much cheaper than the big polypro film speaker caps.

let me know if you are interested,

Paul
Wild Burro Audio Labs - DIY Full Range Speakers
 
I did mean parallel. Thanks for your sharing your experience. I haven't tried motor runs in a crossover, but then, I haven't used a crossover for a few years! However, PIO's are known for having a signature. Newer motor runs are film and oil, so depending on your point of view, they might be preferable for speaker use. Some motor runs are also fused, which isn't good for audio. I can't imagine the film cap isn't preferable to 'lytics in the crossover, and I'd be surprised if they don't have a wider bandwidth than many of the caps often used in woofer crossovers. Folks tend to like motor runs as cathode bypass caps in tube amps, which is a wide bandwidth app. I would have a pair in that function if I could fit 'em! I've also seen them used as coupling caps. I will do a little research, as I'm sure folks have tried them in crossovers before. For $25, I think they are worth a shot.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers
 
Manu,

Sorry to get back to this thread so late! I missed seeing your questions. On the motor run front, I just built an amp that has a couple more (one as PS, one has preamp output cap) and it sounds great! I do hear a loss of resolution when I try large motor runs (120UF total) as a HP filter, but the distortion reduction may be worth it. And I suspect they sound better than most other reasonably priced options.

The Betsy-K could be made to work with a helper woofer, but you may have to cross the woofer over a little higher. Its lower Qts leaves you with less to work with around 150hz and down. Now, if your SET amp has a fairly high output impedance, it would raise the Q of the speaker/amp system, meaning that the BetsyK may be a fine choice.

You are right about the Alnico. The only motor I have access to on a reasonable budget would have not only a smaller Xmax, but a very limited Xmech. That isn't good for OB.

Shipping to Italy would run $55 USD. Let me know if you are interested!

Paul
Wild Burro Audio Labs - DIY Full Range Speakers
 
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