Lowther in a cab between BVR and Onken

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Hi there,

I'm designing a cab for a friend. The driver is Lowther (PM6) and the design goal is relatively small box(compared to BLH).

Been played with hornresp, I figured out a combination of Vb and vent(s) which looked like an Onken, or BVR with smaller vent(s). It looks funny:




And the sim looks pretty good, or it seems too good to be true:



Grey line is output of vent, black is summed of vent and driver. I used the "Combined response" under "Tool" to get that.

And this is the input screen:


I used the configuration of a compound horn and make the front horn almost disappear.

Bad thing is an obvious peak in group delay which seems not so good, but I'm not sure how audible is that:




Will this work? The FR chart seems too good to be true. Ruler flat down to 40-some and the sensitivity is approaching 100db/2.83V with tube amp (Zo=3 Ohm) !

Any comments?

[mondogenerator]

Ive had a few near 'eureka' moments with HornResp too! I must say that i dont understand why you are using the 'compound horn' feature, since it would be BLH wouldnt it? there is only one flare and that is to the back. i think youve used the expansion from driver into the room as a front flare where there is none, unless im misreading it. And assuming i got that right, then also the distance between vent and driver wouldnt be 0, UNLESS it was cunningly folded around. even then, path length difference would be some figure other than 0.

response wise it looks nice, although a 2Pi response may possible be more useful, unless its going to be in a corner forever!!! I had some similar experiments with a totally different driver, they too yielded good frequency response but the trade off seemed to be a poor group delay response, at Fs or from Fs and below. Im no expert in horn theory, but i think this is one of the many audio compromises, that speaker builders must negotiate.

I think the group delay would be audible. I have no idea of the threshold where group delay becomes audible, but 10-20ms is in the area where 'chorusing' guitar effects are based. Whether this is audible to the same degree at 40-50hz as it is in the midrange, i dont know. personally i would still like to get a lower group delay, particularly with a light FR driver cone, since transients are what the SHOULD do best, even at LF.

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Thanks for reply

Tried again without the "front horn" section, it turned out very similar with a broad and very shallow dip (1dB) in midbass range. So the previous "front horn" should be seen as a baffle load, and it does contribute some in the MB.

And yes the path length is 0 (the openning of vent is at the same surface of driver).

Turned it into 2pi, then the SPL dropped to about 94db. I think in most home environment, the speaker cabs should be more or less near the wall and floor, so pure 2pi is not the case. Something between 1 and 2pi, and comes nearer to 1pi is my guess.

Peaked group delay is pain in the *** and can't be improved, unless I give up the bass. Sigh~