My new OB Speaker

[Hari Iyer]

Now for some technicalities -
Below is the measured FR curve with the plastic Dayton waveguide. This is 1 3/8" in diameter (34.925mm). Converting that to frequency is 9850Hz. You can see that from the curves, the HF roll-off happens exactly around that frequency as the waveguide is not able to guide the frequency above that as there is no support from the flares. It will be interesting to see if the DIY horn is also able to demonstrate such a good FR curve which the Dayton waveguide is offering.

 

[availlyrics]

Nice taming of FR curves. Can u also post pics of your testing equipment please

 

[Hari Iyer]

Nice taming of FR curves. Can u also post pics of your testing equipment please

Measuring equipment os a simple Dayton Audio UMM-6 microphone and REW.

 

[Hari Iyer]

After using the field coil drivers in this format for a year, I may plan some modifications to the driver as below,
- change voice coil from 4 ohms to 6 ohms impedance to match mu OPT
- Change the retro paper cone. This is because when this field coil was made in 1938 I persume there was no tweeters around. For this reason the paper cone was made very thin and soft to emit some HF. This extended bandwidth sounds too sweet to my liking. This. FC driver had a very low MMS of just 7gms.

I have narrowed down with trial and error a very capable paper cone which is quite rigid with honeycomb structure in front and back. It weighs just 9 gms. The spider is same reusable type. Adding voice coil weight of 2.5gms will make a total MMS of 11.25gm which is not very high to loose sensitivity. What I would get is a less distorted mid range compared to the vintage cone. The vintage cone also showed signs of aging which eventually would have to be anyway replaced.

Will update outcome later as appropriate

 

[Hari Iyer]

The current state of the FC driver