X/overs with 2 drivers in series Q?'s

[rolfy72]

Okay I need some help on some Xover questions. Im building 5 MTM's for my HT system using el'cheapo Jaycar 5" CW2102 x2 and Vifa D19SD-05-08 per box.

Im not electricaly minded, so please excuse me if Im barking
up the wrong tree here!

The two CW2102's are 4 ohm so they'll be in series to achive 8 ohm's to match the D19.

1. Do I design the zobel network for each CW2102, or do I wire
them in series first?

2. Do you double the Z and Inductance when inputing into a
Xover program for 2 drivers in series?

Zobel network@4ohms

Z= 4 C= 24 mF
V.C Inductance=.6 R= 5 Ohms
----------------------------------
Zobel network@8ohms

Z= ??? C= ??? mF
V.C Inductance= ??? R= ??? Ohms
----------------------------------
3. Is a Series Notch Filter needed, Fs of a CW2102 is 56Hz which
is lower than the X/0 point with the sub?
(70Hz@12db/mains and 80Hz@24db/sub)

4. Do I design a Series Notch Filter for each CW2102, or do I wire
them in series first?

Series Notch Filter
Fs = 56Hz C= 1618.94 uF
Qes= .439 L= 4.99 mH
Qms= 2.731 R= 4.64 Ohms
Re = 4

5. What do I do with the Qes/Qms/Re paramaters when the two
drivers are wired in series?

Series Notch Filter
Fs = 56Hz C= ??????? uF
Qes= ???? L= ???? mH
Qms= ???? R= ???? Ohms
Re = 8?

6. If L= 9.98mH!!!(assuming Qes/Qms stay the same)is it Ok to
use bar type inductors for a SNF?(not made of money...)

7. Should I remeasure the Fs of the CW2102's when installed into
their enclosures first before designing the SNF?

8. The CW2102 have a sensitivity of 87db and the D19 is 89.5db,
how much will the sensitivity change when the CW2102's are
in series 3-6db?

9. Should I keep all enclosure's the same for all 5 speakers?(DTS
5.1),or make the 2mains/1center the same and make the rears
dipole?

I allready have all the speakers so I gotta work with what I got!

 

[MarkMcK]

I advise keeping things as simple as possible. Yes, both impedance and inductance sum. Double both when identical drivers are wired in series, then run your calculations as if the two series wired drivers were one.

Your other questions, however, delve into regions of disputed opinions. We can only tell you what we would do, and that is different than telling you what you should do.

Good luck, and remember that this is supposed to be fun!

Mark

 

[rolfy72]

Yes, both impedance and inductance sum. Double both when identical drivers are wired in series, then run your calculations as if the two series wired drivers were one

So does the Qes/Qms stay the same as 1 single driver, using two drivers in series with a Series Notch Filter?

 

[MarkMcK]

Assume that Vas will double, but all driver Q values will hold constant.

Also, one other question I missed in the first reply. Sensitivity will increase by 3 db with the addition of second driver. There are so many problems with sensitivity ratings, however, that I would never trust what the manufacturer states (unless they give details about how they generated the number and also supply an accurate frequency response graph).

Again, best of luck in your project,

Mark

 

[rolfy72]

Thanks MarkMcK for the info, a little help goes a long way!