Rerurn to Romy the Cat's Site

Mani,

I would leave the subject of DSET/horn setup for another thread and would drop a few words about Zu Druids. They are not the speakers that I would ordinary comment but since I have a local guy with Zu Druids and I had a chance to hear them a few times I think it would be worth to drop a few words. I will comment only about one area – the Zu Druids’ bass.

The Zu Druids’ bass is a freaky animal. If course Zu Druids has no bass in normal since but if whatever bass the Zu Druids is able to do would considered as bass then I was wondering why Zu Druids behave so strange. The guy who use the Zu Druids live in center city and use power right from the wall – so it is difficult to talks about absolute terms as sound changes each hour but some feeling about the Zu Druids I would pass. I did not measure Zu Druids properly, did not have them in my own and my view about Zu Druids might be a pure conjecture. But I heard the a few times and some of my sensations about Zu Druids do make sense to me. So, here it comes….

Forget all that you know, read, and heard about loudspeaker design for the sake of understanding and feeling the understood we need to embrace a totally different view. If you visualize a relationship between driver and enclosure (including port) then there are mass, there are velocity and there is volume (including port). The velocity and volume are fine let it be but let to look only at mass. The question would be the mass of what? Let to do even more idiotic and apply an abstract of General relativity to the example. What is mass in loudspeaker? If a cone has 200g for instance and the suspension has compliance X then we can presume that the dynamic mass would be 200X, right? Well, I would reply: it would depend from what frequency you are. If you are 100Hz then you have no problem to push 200X but if you 100Hz then to develop the force 200X at 100Hz is not much harder but you cave harder contra-forces of the moment. So, let introduce mass not as absolute kg or pound but as relativity to the “pushed” frequency, let measure it in mass per wave length – m/wl, or juts MWL. Ok, we have for 1000Hz a speaker cabinet has 150MWL but for 50Hz it has 10MWL. This is what happen with light speakers that starting from some frequency begin to drift upon own mass deficiency. The Zu Druids are one of the examples – the are light, the are resonant like hell (play with gasket bet the driver and box – you will see) and then as soon the reach some upper midrange then flip over and stop act as mass-scenic system.

Let even forget about port – it is a part of the big picture of mass killing. You are 50Hz, you come to the driver, the speaker has velocity but has no mass – what you do – you tell to the peoples that send you – “fuck it; there is nothing to do here”. It is exactly what bass does in the Druids – it destroys itself and modulation of this distraction poison the sound of Druids lower end. I know, the people with engendering background would read it as feel that it all full of crap but there is a detail: the know nothing about Sound but I do. They design the Druids but I am trying to explain why Druids sound very bad in bass.

So, what can we do? We need to add virtual mass to Druids but only at LF. I have a solution how it needed to be done but first I would like to say why I feel my solution shall work. I was observing how Druids’ bass reacted to different amps. Particularly interesting would be topology and deriving output impedance. The Melquiades lorded to 12K (!!!) for instance with no feedback sounded like “chewing carton” when it drove Druids. The SS Yamaha B2 pushed probably 25 db more, forces me to plug the port and it still was hugely bloomy. It shell not be this way unless the speaker experience the SMDS – or the Severs Mass Deficiency Syndrome. So, how to deal with it?

High-passing the speaker will work but it like trashing a half of the speaker away. If you have a speaker that does >150Hz then you do not need Druids but you need ¼ cub feet box. So, how to make the Druids to work its full range (whatever it is has) but prevent the MWL to lose steam and present the LF from self-distraction?  Well, let add mass to LF with dropping output impedance of the amplifiers that drive Druids at LF. Let up to have an amp with current feedback and let to have an attenuator that would moderate output impedance let say from 5R to minis 1R. I stipulate that listening the Druids in a given room and fine-adjusting the output impedance it would be possible to catch the moment when the LF go into suicide and is not to buffer them but at list to prevent their suicide screams to point the sound of the speakers. I personally fell that it will be a very narrow margin (for instance between 1.25R and 1.3R of output impedance) that would allow very fine tuning and would make the Druids bass to be not deep but not annoying. 

So, I think the problem of the Druids bass (and other similar speakers that are made to float on mass deficiency in bass) is not the bass but the randomness of amps (output impedance) that drive them and disability of audio people to dial the output impedance very precisely (for this time of SMDS speakers).

I do not advocate to do it and to run negative feedback. Will it affect many other things – you bet, it will. However, I think that it might be a good journey to confirm that concept that adding virtual mass to LF via feedback and the fact that it will be VERY important for the speakers that suffers from SMDS.  Warn you that all written above sounds like a complete idiocy --- but I have a very high confidence that the proposed solution will work very affectively.

Rerurn to Romy the Cat's Site