To David McBean: question re path length difference

[jamikl]

David , in the attached diagram should the path length from the rear of the speaker include the internal length of the rear
part of the H frame, ie the length from the speaker cone back to the open rear of the H frame? Thanks for any help.
Mike, jamikl

[David McBean]

Originally Posted by jamikl

David , in the attached diagram should the path length from the rear of the speaker include the internal length of the rear
part of the H frame, ie the length from the speaker cone back to the open rear of the H frame? Thanks for any help.
Mike, jamikl

Hi Mike,

I'm not exactly sure how to interpret your diagram, but when you model the system in Hornresp the message that appears when the Combined Response tool is selected should help to clarify how the path length difference parameter value should be determined.

I think that the answer to your question may be "no", but I can't be certain without better understanding the system you are considering.

If you care to post a screenprint of the Hornresp schematic for your design, I might be able to provide a more definitive answer :-).

Kind regards,

David

[jamikl]

Hi David, thanks for your interest. The speaker is open baffle at the rear so I have modelled the open rear as a port equal area to the box cross section but very very short length. This was modelled using 2 x Eminence Beta 15 which would normally require a very large box but the results here if it works look very promising. It is not really horn loaded but uses the air load of the horn to drop the resonance frequency down to about 18 - 20Hz. Schematic from horn response attached.
Mike. jamikl

[David McBean]

Originally Posted by jamikl

The speaker is open baffle at the rear so I have modelled the open rear as a port equal area to the box cross section but very very short length. Schematic from horn response attached.

Hi Mike,

Thanks for the schematic - now I understand :-).

Differences in front / rear acoustic path lengths within the loudspeaker system are automatically taken into account by Hornresp. Path length differences external to the system must be specified by the user.

By default Hornresp assumes that the two sound outputs leaving the system are equidistant from the nominal listening position and that the path length difference is therefore zero. If this is not actually the case, then the user has to specify the difference value.

To answer your original question - yes, the path length does includes the distance from the speaker cone back to the open rear of the H frame, but this is automatically taken into account by Hornresp.

It would only be necessary to specify a path length difference value if the distance from the port outlet to the listener is different to the distance from the horn mouth to the listener.

Kind regards,

David

[jamikl]

Thanks for the reply David. The object is to get the rear path and the group delay working with the front path rather than cancelling it as in a normal dipole.
jamikl

[revintage]

How does it sim?