Compound mid + basshorn (Pt I)

This is a ‘compound’ horn… a single driver, with a midrange front-horn and back-loaded with a bass-horn.

In my 13 April 2014 post, you can see the fibre-glass Tractrix Midrange Horn, which was designed for a ‘cut-off frequency’ Fc=140Hz.

The Bass-horn therefore needs to operate from 180-140Hz down to around around Fc=30Hz.

P3192047cropAtc-s

Now a 30Hz horn in ‘free-space’ would be huge!

A quick calculation…343/30 (speed of sound/freq) = 11.4m horn-mouth circumference!

So we must utilise room boundary loading (walls & floor) in order to have an acceptable sized horn.  By using corner-loading, we can reduce the horn mouth area by 1/8.

solid-angles

Corner-loading also has other advantages:

  • Bass output to match midrange horn in dB level and in LF extension, tonal balance.
  • In my case, I do not want the loudspeaker to extend forward too much, occupying unnecessary room space.  (Room size 6.1m x 3.6m x 3.3m height.)
  • With multiple horns, the listening position needs to be relatively far away, for best sonic integration.
  • Low frequency response is most uniform with corner placement – all of the room resonant modes are excited uniformly (see below):

Rasnake-room-resonance

Further reading – Best Placement of Sub-woofers (Sonic Design, Sweden).

Horn concept ideas:

This is the Yamamura Dionisio 27 – a nice ‘compound’, single driver horn, but the bass-horn does not utilise corner loading.  And the front output is not properly horn-loaded.

dionisio

Dionysio-1

Below, an early idea for corner-loaded bass-horns, built across the front wall – however this needs a separate midrange loudspeaker per channel:

Cnr-Horn1

Another corner-loaded bass-horn – ‘spiral’ horn folding, with 2 x 180° bends:

Cnr-Horn-4

A corner bass-horn variation with a single 180° bend:

Cnr-Horn-2

Below, is close to the final design – a single driver, with a rear, corner-loaded, folded, curved bass-horn, 4.0m long.  Bass-horn design cut-off frequency Fc=30-34Hz:  The Tractrix Midrange Horn attaches to the front.

Basshorn-12

(Part 2 to follow – detailed design using David McBean’s Hornresp and the horn construction.)

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7 thoughts on “Compound mid + basshorn (Pt I)

  1. Pingback: Midhorn + Basshorn (Part 2) | D a r k L a n t e r n

  2. Hi – I think we follow similar paths … always interested in the person who actually builds stuff …

    Can we talk about some stuff off forum and PM?? (reply).

    Shane C

  3. Great design. I am working on a pair of Voigt HC corner horns from the original ~1934 design which also load both sides of the driver. I am thinking of the Seas FA22RCZ driver as well. Will post. Kenny

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