Help with MEH getting over 900Hz

[cemeterysounds]

I have taped over the comp driver part and remeasured and that was causing a cancellation. I will need to use a different compression driver.

That was a great shout. I did think about it when I first started designing it but I had the ports so close to the comp that it didn't matter at that point.

Also as a sanity check can you remove your compression driver and tape over the throat? the phase plug looks like an anular ring driver and apart from the coaxial comps that cross super low, these are not common to use in MEH.

I will adjust the ports and test it. I am trying out some slot ports.

I'd just leave out all the printed volume filler, between the driver's cone and the horn wall.
That's my first choice guess as to the problem....

When I was simming it in Akabak II needed to make the front chamber quite small and that seemed like the best way to still be able to have full xmax of the driver. Although this was when I was aiming for 2khz so I will see what I can do aiming for 1.6khz.

Are you gating your measurements? doing so should clean up the data a bit

I am windowing but my measurement technique for the moment isn't the best, very nearfield. When it stops raining I will take it all outside to get some better measurements.

 

[mark100]

When I was simming it in Akabak II needed to make the front chamber quite small and that seemed like the best way to still be able to have full xmax of the driver. Although this was when I was aiming for 2khz so I will see what I can do aiming for 1.6khz.

Hi, couple of things...hopefully helpful 🙂

Whatever drivers are on the horn, that aren't being tested, make sure to short them out, or they will effect the drivers under test.
I'm always a little amazed at how much an un-shorted CD, effects the mids and even lows. (alternative to shorting is connected to amp which is on, but with no drive signal)

I like to let go of sims red hot quick when there are problems....

 

[kipman725]

oh wow big effect from the comp, thats unusual but I guess it makes sense as the phase plug has so much open area until quite deep into the compresion driver. What driver is it?

I found measuring ungated directly in the center of the mouth of the horn was quite a useful measurment for assesing modifications to the mids chambers on MEHs. E.G you get results like this:

very good SNR on the measurment even if it isn't truly representative of the on axis response. Also this is with the far cheaper 3FE25....

 

[cemeterysounds]

That is how I have been measuring this but I am in quite a small room. I compared it to measurements taken outside and I think it is reasonable for a quick measurement.

The comp I was using is the Faital Pro HF1440. I also have a HF146 I can use although it's got a different exit angle.

This is how it is currently looking, it would be great without the dip at 1050 haha

 

[cemeterysounds]

This is where I have got to so far. green is 1 driver (2.83v), blue is 2 drivers in series (4v) blocking the other taps and compression driver hole

There is a dip at just over 800hz, when it stops raining I will take it outside and measure it properly

 

[cemeterysounds]

I printed the other bits to measure 4 drivers and it is looking good. blue is 4 drivers, green is 1 driver. Definitely less of a dip

It is sunny today so hopefully I will be able to get a decent measurement

 

[cemeterysounds]

I have finally managed to get some decent measurements outdoors, Got distracted making a small MEH haha. The nearest boundary wasn't that far away but it is more like what I am after.

I still need to get a comp and try it out with that. It is reasonably flat though. Vaguely +-3db between 300hz and 1.3khz

 

[pelanj]

How did this finaly work out?

 

[cemeterysounds]

Sorry for the very late reply.

I abandoned this project as I think the big bottle neck in this would be the compression driver. You would probably only need two of the 4" drivers for it to be more balanced