Newbie Qxx and passive radiators

Jump to Latest
R

rthorntn

Member
Joined 2004
#1
Hi,

I'm a long time lurker.

I'm going to use two Wavcor WF168WA02 (+ Vifa NE25VTS-04 tweeter) with a DS270-PR (to keep the enclosure as small as possible) to build an active 2.5-way for fun, so I read Qts should be below 0.5, in "Explain it like I'm 5" terms, why and what happens if I break the 0.5 rule?

Wavcor Q:
7.10 - Mechanical Q (Qms)
0.56 - Electrical Q (Qes)
0.52 - Total Q (Qts)

I'm a hobbyist wanting to build a few speakers mainly to tinker with CamillaDSP and using a different amp channel for every driver. I'm not wanting to delve much into math, making perfect enclosures or passive crossovers. It's definitely not about perfection for me.

In the future I'll probably cannibalise old speakers and buy new drivers to experiment. I went with cheapish drivers because I figured I might mess things up.

I have a workshop, can work with wood and metal, know how to solder and have quite a few bits of electrical test equipment.

Cheers
Richard

Current main Roon system:
MiniDSP CH1 > Valvet A1r > Salk Songtower RT
MiniDSP CH2 > Valvet A1r > Salk Songtower RT
MiniDSP CH3 > SVS 3000 micro
MiniDSP CH4 > SVS 3000 micro
 
#2
re:'what happens if I break the 0.5 rule' - nothing much, it's a theoretical ideal. Higher Qts usually means larger enclosures. Your box calculator of choice should deal with the value you input. Really the only things you can change are the box volume & the tuning frequency, so play with them to see how the low bass frequencies are affected.
 
  • Like
Reactions: rthorntn
#3
Thanks, a question on only having the one 10" passive radiator on the side, I'm assuming I'll have to compensate with some sort of mass to stop the speaker physically rocking, any thoughts on the best way to do that, some lead weight perhaps?
 
#5
Thanks, yes, I can see it has a M5 threaded hole to allow different types of weights to be added.

It's more a question about balancing, as one side of a fairly narrow speaker will have 3kg of "moving" PR on it, I'm guessing it will need extra weight attached to the speaker enclosure to compensate for that
 
#6
Re:'need extra weight attached to the speaker enclosure" - no, the weight is to tune the frequency of the PR, just as the area of the pipe in a conventional reflex port is tuning the mass of air in the port. re:'3kg of "moving" PR' - I doubt the moving part of the PR has that much mass. The enclosure should be suitably braced in any case.
 
  • Like
Reactions: stv and rthorntn
#7
rthorntn said:
will have 3kg of "moving" PR on it
Click to expand...
I don't think you should add so much weigth to the passive radiator!!!

The weigth of the enclosure should usually be plenty enough to keep the speaker standing.

tuning for higher (>0.5) qts drivers tends to be difficult to get right, so you may end up with some ripple and eventually a peak at the resonator frequency.
But once you consider what the room does to the bass response of a speaker you might just disregard it.
 
Last edited:
  • Like
Reactions: rthorntn
#10
270-PR to this application is not suited. You have said you wanted an enclosure as small as possible.
In that case, only sealed cabinet comes to mind. Should you find bass performance underwhelming,
either bass boost or a larger vented enclosure.
 
  • Like
Reactions: rthorntn
You must log in or register to reply here.
Top Bottom