Saturday, 4 July 2009

New Open Baffle Speaker Concept

Thinking about OB and Full Range speakers. The most apparent critical aspect is the omission of the cross over in the critical frequency range that humans are most sensitive to. This kind of conclusion is widely postulated on the web by a range of different people. Whether this is true or not can only be determined by iterative testing by the listener and the speaker setup. If we take the assumption that around the 200 Hz to 10 kHz range is the most imperative for removing cross overs, then a three way design can be explored.

This new concept is centered around 3 drivers driving the 20-200 Hz, 200-10,000 Hz and 10-40 kHz range, fully covering music from 20 Hz to 40 kHz.

Lower Frequency 20 Hz to 200 Hz (approx.)

Eminence Alpha 15A in a U baffle with approximate internal dimensions of 40cm x 40cm with a 13.5cm depth side wall. This most likely will be actively crossover with a 2nd order Linkwitz-Riley at somewhere between 100 to 200 Hz.

Mid Range Frequency 200 Hz to 10 kHz (approx)

Visaton B200 in an open baffle size of around 40cm by 120cm high. Using either 1 or 2 drivers. By having the baffle this size, and the speakers offset, it appears from EDGE simulations that the baffle boost around 200 Hz to 1000 Hz would compensate for the lowered response of the B200. This could lead to a relatively flat response from 200 Hz to 10 Khz, of which the rising mids can be balanced on the lower frequency by the baffle step response. The natural falloff of the baffle would be boosted with either 1st order or 2nd order filter to match closely with the Alpha 15A.

High Frequency 10 kHz to 40 kHz (approx.)

Fostex FT17H or other super tweeter that is relatively flat up to 40 kHz. This should be filtered with an inline capacitor.

More to follow!

Wednesday, 1 July 2009


In the past few months, work has been quite hectic as well as the family side of things, and haven't had much of a chance to do anything audio. Primarily, still enjoying my music through the Zen amp with the Fostex 127e. On one note, I have begun to be sensitive to the beaming of these speakers. Going to have to investigate ways to reduce this beaming... The plot thickens.

Recently, I purchased a Dayton Audio Class T amp from Decibel Hifi. This was very cheap and came with an power supply as well. This will be an interesting test to see how it sounds as it compares to my Zen amp and the Chipamp. Over the course of time, I am sure I will dismantle the unit and upgrade components where I can. I see already that the speaker connections need work along with the input and volume control. I would also like to build a new case and potentially use SLA batteries to power this puppy.

Still haven't had the opportunity to build the Linestage yet, nor have I even had the time to order the components for the Aikido stage. Shame on me. However, I will get around to it eventually and that should finally give me the missing link in my audio chain.

Been looking around the net for information on Open Baffle speakers. From my cursory reading it appears that OB are quite popular and have a good reputation for being a revealing speaker design. The alternate design I am also looking into are compression drivers mated to horns. In either scenario, a LF driver and amp would probably need to be used below 100-300Hz. At this point, it is interesting to read all the various opinions and technical background on the two designs, and should form the basis of my next speaker project. To that end, an order was placed for a pair of Eminence Alpha 15A speakers from Essential Audio. For the low end, I am currently thinking of a 2nd order Linkwitz-Riley active crossover at 150 Hz, with the Alpha's in a U frame open baffle. The construction and use of this should also assist in my current Fostex MLTL. The U frame should be quick to build, and I will mate them with the chipamp initially, but maybe target a 200W LF amp in the future.

Hopefully have some more updates later and actually get some more stuff done next time.