Please help with the designing of a passive crossover network!

[Big_Bill]

Hello, I am soliciting suggestions for a crossover network!

For my 3.5 Loudspeaker project I’ve designed Zobel impedance correction circuits, assembled them and taken corrected DC voice coil impedance measurements from each one of my drivers.

Now that I have the corrected values, its time to design a crossover network of some sort or another.

Listed bellow are what I have been able to find of the Thiele / Small parameters and response charts, along with the Zobel corrected impedance values for each of my drivers.



Tweeter: Vifa D26TG-05-06

Response chart and specs:
http://www.madisound.com/pdf/vifa/d26tg-05-06e.pdf

Zobel corrected impedance 4.2 Ohms





Midrange: Peerless 832873 HDS 5-1/4"

Response chart and specs: http://www.speakerbits.com/net/catal...aspx?id=PD150A


Zobel corrected impedance 5.8 Ohms






Woofer: Adire Audio AV 8

Response chart:
http://ldsg.snippets.org/graphics/adire/AV8full.jpg

Zobel corrected impedance 5.5 Ohms


Re (Ohms) 5.5Z
(Ohms) 8
Le (mH) 1.15
Fs (Hz) 35,8
Qms 4.19
Qes 0.43
Qts 0.39
VAS (L) 51.8
Sd (cm^2) 231
Xmax (mm) 6
Pmax (w) 100
SPL 89.3






Sub: Pyle PPA 15

Unable to find response chart.

Zobel corrected impedance 7.1 Ohms


Power (watts peak/rms) 800/250
Nom. Imp. 8 Ohms
FS (hz) 26.7
Qms 2.69
Qts 0.89
SPL(db) 90.2
VAS(cu ft) 11.357
Voice coil 2.5 KSV
Magnet 70 oz
Cone: paper
Surround: cloth
Spider: super
Dust cap: poly concave
Frame: stamped steel
Back plate: bumped and vented.



I’ve got an idea for the Pyle, I could go first order low pass since I’ve got iron core 18 gauge copper wire 12.7 mH inductors on hand which would cross at an actual 89 Hz @ 7.1 Ohms.

As for the AV8, I could go first order band pass. With a ten percent allowance (recommended to me by others here on DIY), high passing the AV8 at a stated 97.9Hz but an actual 107.69 Hz @ 5.5 Ohms with a 268.44 uF capacitor. Low passing the AV8 at a stated 300 Hz but an actual 270 Hz @ 5.5 Ohms with a 3.24 mH inductor.

As far as the Peerless and Vifa are concerned, I am out of my comfort zone.


Post Script: If any questions as to the very odd selection of drivers used in this project please see my original thread.

Need recomendations for 3-5" midrange driver?


Please post any suggestions!

[augerpro]

How did you measure the impedance? A DC multimeter is not going to read correctly because the cap in the zobel will not be "seen".

Designing any speaker with textbook values is not a good idea, but trying to do a 3.5-way is near impossible. I would focus on making a 2-way with the Peerless woofer and Vifa tweeter, somehow correcting for baffle step, and add the Pyle as a bass bin, and cross it low to the mid/tweeter with a cheap active crossover like the Behringer CX3210. Just my .02

[Big_Bill]

Thank you augerpro!

I did measure the impedance with an analog multi-meter. What type of meter should I use to measure the impedance?

Bill.

[augerpro]

Something that uses an AC signal to measure impedance. The Zobel calculators I've seen calculate the predicted impedance (or maybe it was just DCR) of the driver after the Zobel is in place. What did the one you use say?

BTW you don't need one the tweeter, won't need one the Adire if you don't use it (I wouldn't) and don't need one on the Pyle if you use an active crossover.

[Big_Bill]

This is the calculator I used for the zobel vaues.
http://diyaudioprojects.com/Technical/Speaker-Zobel/


This calculator does not predict the corrected impedance.

The calculators Ive seen for crossover values seem to ask for DC resistance, dont they?

Bill.

[richie00boy]

Crossover and zobel calculators do not use DC resistance, they use the impedance at the frequency of interest. To measure this you need a signal generator, resistor and volt meter.

[Big_Bill]

Originally posted by richie00boy
Crossover and zobel calculators do not use DC resistance, they use the impedance at the frequency of interest. To measure this you need a signal generator, resistor and volt meter.

Thanks for the post richie00boy!

As for Zobel calculators not using DC resistance to calculate component values, here is a qoute from the above referenced Zobel calculators supporting text: "Where:

•Re is the DC Resistance of the driver [ohms]
•Le is the Voice coil Inductance of the driver [H]
•Rz is the calculated Zobel resistor [ohms] and
•Cz is the calculated Zobel capacitor [F].
Use this online calculator to determine the required Zobel resistor and capacitor. Simply enter Re and Le into the boxes below and click the CALCULATE button. Use the CLEAR button to reset all the values."

I also have found simular text on many other sites dedicated to Zobel networks.

Can you please rectify this for me?

Bill.

[Moondog55]

OK
Hi Bill; as you can tell from the responses so far most people think that this is difficult going on impossible

I disagree; it is just hard

If you are going to swap-out the Pyle in the future for that other 15 inch driver I'd disregard it at this stage.
As you have made Zobels for the drivers already then the impedance should be relatively flat ( which is an excellent starting point )

1 / if you low pass -high pass the Adire it has become a 4-Way, Don't do that. Inductor values are too big, the .5 woofer is to boost the low bass so you want the Adire 8 to run from Fs/Fb to where you cross to the Peerless Mid-range.

2 / Run the mid-range as wide as possible; 300 to 3000 is what I would recommend.

3 / 10% is good as it stops overlapping, so yes cross the Adire 1st order at 270hz

4/ recalculate the XO for the tweeter using 3300 ( won't be too far removed from previous values )

5 / I think you will need to use second order XO for the Peerless at 300Hz but at the top end it already has a reasonably smooth second order roll-off so a first order should work at 3000Hz

6 / Do all of this outboard of the box as it will need tweaking.

7 / When all of this is done, then play with the .5 woofer with the biggest coil you can afford.

You already have that 12.7mH coil, it may be usable for a Linkwitz-Riley (L/R ) XO down low.


Do you have the formulae for calculating crossovers? I can't remember

This is where the fun starts.

Regards
Ted

[Moondog55]

I have been doing some calculations for you Bill
If I can't make speakers for myself ATM I can help you.

I checked the Ballpark impedance, and using 6.5ohms ( which is close enough ) for the Peerless mid and using a simple Linkwitz Riley XO at 300HzI get these figures

A 40 uF cap in series and a 6.8mH inductor in parallel, at the top end; if I use your value of 5.5R I'd be using a single low DCR coil of 0.29mH, if however the impedance is stabilized at 8Ohms, then that value is 3.3mH.

I'd go with a standard value and change the resistor value in the Zobel until it sounds best, which is why outboard XOs are so useful.

At 270/350 Hz the little Adire woofers impedance is going to be very close to the DCR so I agree with the inductor value of 3.24mH for a first order low-pass

[Big_Bill]

It has just now dawned on me that I forgot to list the values of the Zobel network components! I will remedy this now. Bellow are listed the values I used.

Vifa = 6 ohm resistor and 2.2 uF capacitor.

Peerless = 7.6 Ohm resister and 14.2 uF capacitor.

AV8 = 7 Ohm resistor and 24.2 uF capacitor.

Pyle = 7.6 Ohm resistor and 17.2 uF capacitor.