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The Frugel-Horn existence directly follows from answering the question "DIY design similar to hornshoppe?" -- a thread that was on a previous incarnation of the Decware Forum (closed down now). (the person who asked the question is now enjoying his own set of diy Frugel-Horns with modified FE126e)

Initially we derived a modified Buschorn MK1, widely regarded as being a reference for compact corner-horns, by modifying it to accept larger drive units. The design was simulated (assuming free-space positioning) and the results compared to the measurements taken by
Stereophile of the excellent Hornshoppe Horn which rumour has came from a similar genesis. Free space positioning removes room influences from the response, and ensures that only the horn's performance is analysed. An impedance curve tells you a lot about a box, and in the case of a horn the peaks & nulls are a reflection of the horn's expansion and foldings. The respective responses, simulated and measured, matched closely. This assured us that we had a horn with bass alignment very close to the speaker in the thread title, and something we could build on. A sim won't tell you about all the little tweaks & tricks to make a good sounding speaker a great one, but, if one adds in years of experience, it does give high confidence that at least it is close. (plans for this modded B-Horn are in one of the appendices of the Frugel-Horn plan document).

The initial conceptual 3D line render with an FE108eSigma


Red (FR) & black (Imp) are the mod B-Horn sim, purple (FR) & green (Imp) the Stereophile measures -- clik for larger graph

  We built 2 of these so that we could get a handle on different drivers -- primarily the FE126 & FE108eS. We were happy with the 1st prototypes for the FE108; the ones with FE126 need some CC tuning. Detailing the CC and changing to modified FE126e has us preferring the 126 over-all. It is really astounding what these little babies can do (and we weren't done yet).

While developing these plans we saw places where some changes could be made to make the design more elegant and more versatile for DIY use. This primarily involved rerouting the 1st folds to move the voids to where they could be used as additional compression chamber volume (or as many have done, opened up to punctuate that these are folded horns). The width was also increased slightly givng an 8% larger mouth and a slightly less radical mouth aspect-ratio.

insides of Hornshoppe Horn -- this linked picture from the positive 6moons.com review and has also been posted by Ed Schilling on public forums a number of times -- it was the inspiration for the modified B-Horn test mules

This design was built and immediately some changes were made to simplify the horn path to make it easier to build (alpha 1.3.0). These plans were released. Some early adopters built this horn and the general consensus was that we had something worth pursuing further

Meanwhile Ron Clarke was doing his magic to the horn mouth. He derived the optimum curved mouth exit and the deflector. The curved mouth helps compensate for its high aspect ratio (ideally a horn has a square or circular mouth) and the deflector minimizes reflections back into the mouth and ~doubles the controlled mouth flare. We had already incorporated supraBaffles similar to those on his Austins. These 3 "add-ons" to the alpha 1.3.0 gave 5 possible levels of build. Renderings were done to illustrate the possibilities.

The full-up build of the horn (alpha 1.4.0 Level 3) was built and got its 1st public exposure at the 3rd annual Vancouver Island diyFest where acceptance was overwhelmingly favorable. Based on this, the build was elevated to Version 1 status (and alpha 1.3.0 builds became Version 1 Level 0 builds).

A comprehensive set of plans was completed & released. A number of horns have been built from these and feedback is coming in -- generally very positive. Minor updates have been released.

alpha 1.2.1b with supraBaffle & modified FE126e

Form follows function and comparisons with the horn that inspired the Frugel-Horn are inevitable. No-one has done a direct comparision. Technically the Frugel-Horn -- in level 1 & higher builds -- has some technical advantages, but as we all know the devil is in the details & execution will always play a role.

With size & format more or less fixed the Frugel-Horn will not pretend to offer things that really are the realm of larger horns. If you can live with something larger and more obtrusive there are other options such as Ron Clarke's A126 (the current reference for our evaluation), the Dalek Horn, and any number of others -- many now residing here on this site.