Zu Druid questions

Macrojack,

The issue of the SoundStage measurements came up. I posted a possible explanation. Note that Zu hasn't really described what their enclosures do, so we are left to surmise - and note also my request for clarification and correction on the specifics. Is trying to understand the SoundStage measurements and correlate what little we know about the encloure design with subjective impressions really so out of place as to be called "hijacking"?

I'm going to do it again, just so you know. Shadorne commented on a similar-looking frequency response curve in a PMC loudspeaker as possibly shedding light on the Druid's design. I'm going to reply to him.

Also, just so you know, it's not the numbers themselves that I value. It's the knowledge and insight that can be conveyed if you understand what the numbers are saying. I wish to understand loudspeaker design (and the Druids are a particularly interesting design), and I wish to share my understanding with others who are interested in loudspeaker design. If you feel I have mischaracterized the Druids in some way, by all means take me up on my request for correction. If you just object to my interjecting numbers and science in general, I invite you to start another thread and we'll discuss it.

Shadorne,

Thanks for bringing up SoundStage's measurements of the PMC speaker. I think there's some information there that may shed light on the mysterious Druids.

The PMC is clearly a tuned pipe enclosure - in this case a transmission line having a factory-specified line length of "2 meters". The midbass notch location would lead me to expect a line length of about 2.15 meters, so the specified line length corresponds pretty darn close with the location of the notch. I think the notch is too severe and too low in frequency to be related to an internal resonance. It looks like what I used to get in some of my transmission line designs. I'm pretty sure the PMC woofer has a higher Qts than the fullrange driver in the Druid, which would be consistent with the PMC's measured response holding up better below 100 Hz.

From the location of the notches, we can conclude that the PMC and Druid have similar path lengths. The PMC uses a three-fold transmission line. We don't know what's inside the Druid yet. Maybe one of these days I'll try to map out the internal partitions by knuckle-rapping.

There's something else we might gain insight into from a comparision with the PMC measurements. Take a look at both impedance curves. You see how the Druid's impedance peaks rise up much higher in the bass region? My guess is that's partly due to the Druid having relatively little damping material in its enclosure. Now some of the difference could also be due to high a high mechanical Q (Qms) of the Druid's driver, but even a little damping material in a tuned pipe should bring those peaks down considerably. I'm not saying there's no damping material in the Druid, but what's there is evidently not very effective at low frequencies (intentionally, I would guess - the impedance curve may be an indication of the design's muffler heritage).

By looking at both speakers' frequency response and impedance curves, I think you can see a family resemblance. Something similar to the PMC's transmission line - but obviously not identical - seems to be going on in the Druid's enclosure.

Duke

Sorry, guys. I didn't mean to attack anybody but time and again I have seen these simple requests turned into engineering dialogues which completely abandon the original poster. I suppose if he were to come on board and request clarification this might make sense. As it is, I believe he has been left high and dry.
For a few of you, the emphasis seems to be on what went into the speaker but you may be surprised to learn that most of us only care about what comes out of it.

Macro...I agree completely!! Why does this happen so frequently? I posted my impressions of the Zu's sound in comparison to the Ushers as the original posted requested...NO one else makes mention with the exception of Mondonitro about how the Ushers compare or that they heard them at all.

Look you are all entitled to your opinions and offer your suggestions, but lets keep to the posters query,and not make it a platform to grandstand your knowledge of speaker designing,, share scientific measurements that dont offer any help at all as to the sound of any speaker, much less a comparison of two differnt designs, or bash a very sucessful company (Zu) who got it right and still has many detractors who cry over that fact.. Im sure Mr. Jack Dotson is left scratching his head over all this...come on man!

Kehut,

The original poster said that the Druids "have peaked my interest". I didn't read that as excluding interest in all commentary other than a direct comparison with Usher and/or Klipsch speakers.

And... well, I don't know any other way to say this. Since when is talking about speaker design on the "Speakers" board in a thread about a speaker with an intriguing and mysterious design "grandstanding"?

Kehut, not everyone shares your belief system that "scientific measurements dont offer any help at all as to the sound of any speaker". (Have you run that by Sean and Adam?) I guess you missed it, but what I was doing was explaining to the best of my understanding (given the lack of published design details) how the Druids can still have decent-sounding bass when they measured 25 dB down at their rated low frequency limit (38 Hz) and have a similar notch at 150 Hz. On paper, that really is abysmal performance. Come on man indeed... I was trying to keep your speaker in the running in the eyes of someone who may still give science some credibility.

Duke

OK, I'll remember from now on:
No digressions from simple answers to simple questions.
Thanks for filling me in on the rules here.