8"+1"

This project is slowly progressing, sorting out a CNC run of 4 of these cabs now for the passives.

dlyxover wrote: I was going to put a zobal network on, am I right in thinking I want to add it to the driver then remeasure to get the impedance at the crossover points?

You know the impedance curve of the box above resonance now so you can calculate that as an impedance with the base resistance subtracted, then work out your zobel components to flatten it. After you build the filter then yes, if you measure the impedance again then above resonance you should see a flat line, ideally purely resistive with frequency. This will help simplify your xover design, but always bear in mind the actual acoustical response of your drivers. Getting a flat electrical response is one thing, but it will be multiplied by the acoustic TF to form the final response. And then you have all the fun of impulse response, directivity, power dispersion etc if you want to go a level deeper.

Sorry if you knew all that anyway!

Upon looking at your plot Teunos I'm thinking my calibration mighty be out.

dlyxover wrote: Upon looking at your plot Teunos I'm thinking my calibration mighty be out. on my 8" plot its not hitting 8ohm anywhere, same with the 1". Do I need to subtract the base resistance? A Odc04r mentioned I presumed the measurement on the plot is the actual measurement.

Remember that what is usually quoted is the DC resistance, so if you take the plot down to nearer 0Hz it may get closer to 8 ohm. Also you have loaded the driver into a cabinet now and that will affect the electrical load it presents to the amplifier. I recall off the top of my head measuring a Volt 8" in a reflex cab not too different from yours in terms of volume at about 11 Ohms nominal a couple of years back. From the amplifiers point of view this is an easier load to drive. If you take the driver out and measure it you might get closer to the nominal impedance.

If you are concerned about the calibration of your rig try measuring the impedance of a resistor measured with a multimeter and see what you get. Even a cheap multimeter should get to near 0.1Ohm accuracy if it is calibrated ok. For best result measure the sense resistor with a good DMM but not everyone has access to that.

When I say subtract the base resistance I mean that from about 200Hz and up the total resistance is made up of the DC coil resistance and then the frequency dependent impedance. Depending on how you calaculate the Zobel you will probably need to enter those separately, although they are both a component of the total reactance. Just one depends on frequency and the other is a constant.


Edited by odc04r - 19 June 2015 at 4:29pm

The measurement was mad with the driver in the cab, have re checked the calibration is correct.

Is there a way to just increase the baffle size and increasing the vent size to accomodate a Faital 10" PR300 neo was just curious since I also have a pair looking for a nice cabinet design like this?