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Should I go ported?


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#21 3ll3d00d

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Posted 26 March 2017 - 08:00 PM

I don't know what you are doing in Hornresp, but for the frequencies that you are interested in, that port is definitely not "far away" from the driver.  It's less than 1/4 wavelength at the port resonance, which is what will give you trouble if anything.  Depending on how strong it is, you might want to try to knock down the port resonance with a PEQ.

that's what I thought (that the port is not far away in wavelength terms) but it seems like that setting has a relatively strong effect (in terms of making the port dominate output if you move the port closer to the listener). This makes me think that that setting doesn't do what I think it does (wouldn't be the first time in hornresp), It's described pretty plainly as

 

The distance from the port outlet to the listener can be adjusted if necessary using the length difference parameter. A positive value for path length difference increases the listener distance.

The path length difference is the distance from the port outlet to the listener minus the distance from the direct radiator diaphragm to the listener. The difference is positive when the distance from the port outlet to the listener is greater than the distance from the direct radiator diaphragm to the listener.

 

Example of the effect - http://imgur.com/s3IwddN



#22 SME

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Posted 26 March 2017 - 08:28 PM

I have no idea what's going on there.  Assuming the driver is front-firing toward the listener, the distance difference to the listener from the port vs. driver is like 20 cm at most.  You definitely shouldn't be losing 3 dB at the 15 Hz tuning frequency with that distance.  Is there an issue with the units used in the field?  Even if there was, I would expect to see a ripple across the response, so I really have no clue what that setting is doing.

 

I've used Hornresp for some ported models before, and I don't recall seeing that behavior either.  I can't recall whether I filled in that parameter or not.  Maybe someone else with Hornresp experience can chime in.



#23 3ll3d00d

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Posted 27 March 2017 - 07:18 AM

I don't know what you are doing in Hornresp, but for the frequencies that you are interested in, that port is definitely not "far away" from the driver.  

 it seems like that feature adjusts spl of one source by an inverse square law sized amount which I suppose is where the "surprising" result comes from as I'm thinking of "what will happen in a room" and the model is not. 



#24 3ll3d00d

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Posted 31 May 2017 - 06:09 PM

My 21DS115 turned up today, seems like a nicely built driver and I can definitely feel the benefit of the lighter magnet (vs lugging around my UXL)


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#25 Ricci

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Posted 02 June 2017 - 01:56 PM

Have you started on your cab?



#26 3ll3d00d

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Posted 02 June 2017 - 02:18 PM

only in sketchup atm, trying to decide exactly how best to size it so it fits where I want it to go + I have to space to build it + tune is where I want + not really wasteful of sheets of wood. The design has been complicated somewhat by the fact I might now build a screen wall and hence put the sub in a different place as well






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