Tuning a Base-Reflex enclosure with a impedance curve

[DualTriode]

Hello,

I am getting the stuff together to test the TS/P of the used JBL2226H driver(s) purchased.

See the attached photos.

Rather than fabricate at test enclosure I purchased one of those carpeted things that goes into a car. It is reported to be 2.1 cubic feet net. With the driver mounted on the face it will be 1.9 cubic feet. The box arrives Wednesday.

The driver will be kept on the shelf in the un-heated garage. I will turn the heat off indoors.

The raw impedance data and TS/P calculations will be recorded on the first sweep. The JBL data sheet stated driver mass will be used for the TS/P calculations. The overnight low temperature is forecasted to be 42 degrees F.

Thanks DT

 

[DualTriode]

Hello All,

I carried the new to me previously used JBL2226H driver in from the garage into Sparky’s (Sparky the Cat) Lab. I connected the driver to the APx555 + APx1701 and ran the TS/P test sweep only once.

The driver has been in the unheated garage for two weeks. The overnight low was 42 degrees F. The temperature in Sparky’s lab was 57 degrees F for the test sweep; 5 seconds at 5 volts.

I will test the driver parameters again in the 2.1 cubic foot box Wednesday or Thursday. I will test it again cold and a several steps of warming up.

See the link to the JBL data sheet; note JBL uses different test conditions.

https://jblpro.com/en-US/site_elements/2226h-j-specification-sheet

See the attached plots.

Comments?

Thanks DT

 

[GM]

Not looking good for the home team since 'cold' specs should still close enough 'fit' a factory spec cab alignment.

 

[weltersys]

See the attached plots.

Comments?

Pretty clean looking cone, it may never have been run to Xmax before you bought it. The latex surround will stiffen a bit after sitting unused, especially when only 57 degrees.

The Fs coming in 6 Hz high does indicate the suspension needs another "exercise period".

 

[DualTriode]

Hello All,

I got up this morning and put this same JBL2226H on this carpeted 2.1 cubic foot made for the trunk of a car sealed box.

I warmed everything up to 66 degrees F plus ran several sweeps to warm up the Voice Coil, driver and sealed box.

I put in my ear plugs set the amplifier output voltage to 5volts. 5volts or 3ish watts is wow kind of loud, over 100dB’s loud.

The factory data sheet TS/P and winISP box simulator are nowhere near the measured results. Knock me over with a feather.

The installed, Total Q, on a net 1.9 cubic foot enclosure is Q= 1.03.

Next I am taking the driver off the enclosure and going to stuff some Dacron pillow stuffing into the box to see what happens to the measured Q.

The expected result is that the measured Q will go down a bit with the added damping.

The theory stuff that I read suggests that a smaller (higher Q) enclosure is the place to start if an aperiodic tuned enclosure is the goal. Sounds like I am on track for that.

Thanks DT

See attachments

 

[DualTriode]

Hello All,

I stuffed the enclosure 2/3 full with Dacron pillow stuffing.

The resonance frequency and Total Q both went down only slightly.

See the attached.

Thanks DT