4722-HF (2432H) to 2226H crossover point/slope (active crossover)

[Jonas_h]

Hey,

I have 4722-HF's with 2432H CD's and a 2226H which I would like to optimize as much as possible.

I have measured the HF without any crossover, and this is the response:

http://dl.dropbox.com/u/10759510/ForumPics/4722hf.jpg

I am surprised that it rolls of that early and that steep. I have used the speakers for about a year now with a "quick and dirty" crossover setting, but I would really like to do it the correct way this time. Especially in regards to phase alignment at the crossover frequency which I have never done before.

Any input on how I can identify the best solution for the crossover settings is appreciated! For EQ/Crossover I am using a BSS Soundweb BLU160 and measurement mic is an Earthworks M23.

[pos]

This is a textbook constant directivity horn response, quite impressive in fact, and probably very similar to the natural response of the 2432 on a tube. Any compression driver will have a 6dB/oct rolloff above its mass breakup frequency (between 2 and 4khz depending on the mass of the diaphragm and strength of the magnet), and a non-beaming horn will show this rolloff untouched (which is regarded as a good thing in most situations).
This type of compensation is typically achieved with a resistor and a cap in parallel in a passive crossover (look for econowave filters and Zilch's "quick and dirty" posts). With your BSS a simple 6dB/oct +15dB hishelf (or negative lowshelf) with the 3dB point at 4khz (the "corner" frequency vary from one filter to another...) will probably be enough.

[Jonas_h]

Thanks! What crossover freq. and slope would you choose between the 2226h and the horn? and how would you verify that you have chosen the best settings?

[Jonas_h]

Another thing I'm unsure of... Should I choose a slope for the HF that follows its natural roll-off or should I "force" it to follow a slope by using EQ?

[pos]

To make decision in the <2khz range you will need to do good measurements using holm impulse and proper gating, which is not easy (you will need lots of distance from nearest objects/walls/floor).
I am not sure I understand what you mean about the rolloff, but you are supposed to compensate for it using eq, making the final response curve almost flat (you can allow for some limited rolloff in the high, depending on the house curve you are looking for).

I am surprised JBL does not provide eq curves and parameters for this product.
Looking at the spec sheet (http://cn.jblpro.com/catalog/support/getfile.aspx?doctype=3&docid=621) it seems that the horn does beam a little in the UHF (on purpose, as it is meant to be used behind a perforated screen), but it is very limited and controlled. Looking at your measurement a very simple eq will be enough, and you can look for obtaining a flat curve up to 20khz on axis and get a nice power response that will rolloff very gently above 6khz. These look like very fine horns indeed!

EDIT: you should use some HP filter, at least at 200Hz or 300Hz, to protect your driver from overexcursion during these measurements

[grumpy]

It could be what is being asked is the lower crossover for the horn...
i.e., set an external crossover to follow the 'natural' 700Hz rolloff,
making the filter+acoustic rolloff even steeper.

Considering tradeoffs in power handling, pattern control,
and in listening tests might help. It would be 'safer' to
rolloff the horn's low end at a higher frequency, but this
is likely for home use, so -some- margin in slope rate can be
used up for the sake of personal preference (e.g., Pass' L300
redux)

[Jonas_h]

It was exactly the lower crossover I wanted to know about. I tried yesterday, and found that the best/smoothest sounding setting was 820hz. Lower than that, I think there are some audible artifacts from the horn.

I tried setting it up yesterday and used Smaart for phase aligning the drivers - here is the result:

http://dl.dropbox.com/u/10759510/ForumPics/Screen shot 2012-04-24 at 9.15.09 PM.png


It sounds very promising already even without any EQ. I still think the gap between the horn and the 15" is too big. It would be optimal to add the 2x8" section from the ScreenArray series, but I dont have the space :(

Do you think 820hz is too high for the 2226H?