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Combining a 2" exit driver with a HF unit as a point source. Is it possible?
Combining a 2" exit driver with a HF unit as a point source. Is it possible?
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Old 9th January 2020, 02:36 PM   #11
kipman725 is online now kipman725  United Kingdom
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It could be that the reason the large comp sounds bad even when EQ'd is the diffraction slot in your current horn. I haven't personally listened to horns with such 'hard' diffraction features but other people complain of 'frying eggs' noise especially at high output. Have you tried it on a more modern horn design? perhaps biradial?
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Old 9th January 2020, 03:42 PM   #12
pelanj is offline pelanj  Czech Republic
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Combining a 2" exit driver with a HF unit as a point source. Is it possible?
Yes, I completely forgot about them! Thanks for reminding, that should work At least somehow - I will need to print a new pair with longer part without a the slot, so that the slot starts right above the horn wall.
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Old 9th January 2020, 03:44 PM   #13
pelanj is offline pelanj  Czech Republic
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Combining a 2" exit driver with a HF unit as a point source. Is it possible?
I think it sounds bad because it needs really large boost for the HF. I have no problem with the sound of a Beyma CP385/Nd on the same horn.
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Old 9th January 2020, 04:01 PM   #14
kipman725 is online now kipman725  United Kingdom
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Quote:
Originally Posted by pelanj View Post
I think it sounds bad because it needs really large boost for the HF. I have no problem with the sound of a Beyma CP385/Nd on the same horn.
What kind of processing are you using to apply the boost? perhaps you loose too much dynamic range or have clipping or numerical instability. There is nothing intrinsically wrong with large boosts but a lot can go wrong, for example using IIR filters the coefficients need to have a high numerical precision.

This is one of the reasons I use a passive crossover on my comps as I can include most of the EQ in that crossover so don't need large boosts in the digital domain and improve dynamic range.
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Old 9th January 2020, 04:41 PM   #15
pelanj is offline pelanj  Czech Republic
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Combining a 2" exit driver with a HF unit as a point source. Is it possible?
The boost is via Thomann DSP 4x4, the output had still tons of headroom - but maybe the result would be better with passive attenuation instead. I will definitely need to try that, too.

I revisited my K-Tube measurements and I shortened the window to take out the first reflection. Above means the part without the slot. I do not think I can resist sticking the K-Tube into the horn now The main point as I see it is bringing the output closer in the vertical direction, which would be my goal.
Attached Images
File Type: jpg K-TubeHorNew.jpg (116.3 KB, 207 views)
File Type: jpg K-TubeVerAboveNew.jpg (101.3 KB, 165 views)
File Type: jpg K-TubeVerBelowNew.jpg (101.7 KB, 168 views)
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Old 9th January 2020, 05:38 PM   #16
kipman725 is online now kipman725  United Kingdom
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The Thomann DSP is a quite low cost unit I would guess it uses fixed point processing so I would try a basic passive network to equalise and then do the 'fine tuning' in the DSP. Even if its floating point (which avoids the problem of accidentally digital clipping in the processing pipeline) its probably only 32 bit which isn't sufficient precision for high Q IIR filters. If you open it up you will be able to see the DSP chip it uses and the data sheet you should be able to check this. You could also try as a quick fix to split your overall EQ into half boost and half cut and/or trying to use low Q PEQs.

The way you could actually test your DSP is to put in the EQ you want and measure the response using REW, comparing it to what you expect to get. They should exactly match if they don't you have issues!

I'm using a Symetrix Symnet 8x8 DSP, they are sometimes available very cheaply and have a 40 bit floating point data representation (enough for 24bit data), they use multiple xilinx spartan 6 FPGAs for processing the audio data.
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Old 9th January 2020, 05:41 PM   #17
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Quote:
Originally Posted by pelanj View Post
I revisited my K-Tube measurements and I shortened the window to take out the first reflection. Above means the part without the slot. I do not think I can resist sticking the K-Tube into the horn now The main point as I see it is bringing the output closer in the vertical direction, which would be my goal.
Looks great! the K-tube should also have minimal interaction if put in carefully, I would keep it away from the diffraction slot.
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Old 9th January 2020, 06:32 PM   #18
pelanj is offline pelanj  Czech Republic
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Combining a 2" exit driver with a HF unit as a point source. Is it possible?
I was digging through some old measurements and now I know why that actually sounded so horribly...it was the microphone which had bad HF response - and when equalized flat, there was just too much breakup treble at least by some 6 dB or maybe even more. The Thomann DSP main chip type is scraped out for some reason. And it was also another horn which was not as flat as the ARB-2. I can definitely drill a hole into one of the horns and compare the result. I will try two K-Tubes - one shorter about the size I have now and one longer that would time align the drivers - which will require a longer tube - which in turn can screw up the response. In the picture on the previous page, it actually seems they are trying to align the HF driver with the midrange.
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Old 9th January 2020, 07:47 PM   #19
pelanj is offline pelanj  Czech Republic
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Combining a 2" exit driver with a HF unit as a point source. Is it possible?
This is what I came up with in XSim. How does it look like?
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Old 9th January 2020, 08:22 PM   #20
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Try padding the comp with a series resistor and a parallel resistor that way the padding is less sensitive to impedance variation. Also I think your absolute levels are a bit low as the raw driver should be 110dB+ mid band.
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