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Multi-Way Conventional loudspeakers with crossovers

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Old 18th November 2011, 07:59 PM   #231
Starre is offline Starre  Sweden
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Hmm, so it is bigger than mine which is 28m2 but with a open wall to my kitchen to the right of my stereo making it a little bigger in total. Well maybe that is not the most important thing.
If I am smart I should probably start now with listening with different amout of filling behind the woofer. If I use 135mm when doing this, then later when I am satisfied with that I should fine tune the lenght, right?
I am afriad that testing with different amount will change the bass output so that should be in place first.
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Old 18th November 2011, 08:09 PM   #232
Salas is offline Salas  Greece
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The filling can damp mids, and can obstruct reflex circulation losing port bass amplitude, but not damp bass modes. If we could damp bass with just some wool filling then we wouldn't have those sci-fi anechoic rooms with children sized wedges in the KEF brochures from the 70's.
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Old 18th November 2011, 08:12 PM   #233
Starre is offline Starre  Sweden
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I have read that the more you fill the box the bigger it appears to the woofer, that it can be used to tune the size of the box, if it is made a little to small you can fill more and it appears bigger to the woofer, isn´t it true?
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Old 18th November 2011, 08:22 PM   #234
Salas is offline Salas  Greece
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A small apparent volume difference they do make, but the damping materials are there to damp the echoes inside the box mainly. If you use them as masses near diaphragms and ducts when moving relatively freely they can load the total Helmholtz thing and deprive enough wide Q output. Too much expense in energy. Better tune than control. Passive control is always involving energy loss. But do what you wanna do and find out how those things work for yourself. Its fun, nothing electrical to short. Ain't an amp, and you may find your best compromise.
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Old 18th November 2011, 08:27 PM   #235
Starre is offline Starre  Sweden
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Thanks Salas, this is interesting, I am learning a lot from this project. I will try some and post tomorrow, have a nice evening Salas .
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Old 18th November 2011, 08:32 PM   #236
Salas is offline Salas  Greece
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Have fun.
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Old 18th November 2011, 08:45 PM   #237
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by Starre View Post
I have now tried to move the speakers +-10cm from back wall and it was a rather small change
This is surely a lot of work, particularly using a handheld SPL meter. I understand you are tuning your port, maybe a tool like this spreadsheet may give you some idea of what your changes in room position will do.
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Old 19th November 2011, 10:12 AM   #238
Starre is offline Starre  Sweden
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Thanks for the link AllenB. I removed the polyester filling behind the woofer and it sound more open and present in the middle range. I had too much here according to Salas build and now I have even less since the sides are bare, so I will try with some filling there later. I wanted to remove all so I could hear easily what happens.
I am also trying now with 140mm tube lenght.
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Old 22nd November 2011, 10:10 AM   #239
Starre is offline Starre  Sweden
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I have settled for a 135mm port after testing 130-140mm. Small difference but anyway. I also put some filling onto the sides behind the woofer and it seems fine. Is it a bad idea to have bare surfaces on the sides near the woofer?
I will give them 50 more hours to settle in before I am ready to glue the baffle in place. Got a feeling it need that, the bass is a tad lean sometimes playing music. But I am rather sure that the 2.5mH coil is enough, more playing will tell. How does the sound vary in quality from a non-ferrite coil vs an air coil used for the woofer, same spec. otherwise?

Last edited by Starre; 22nd November 2011 at 10:24 AM.
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Old 22nd November 2011, 11:33 AM   #240
bbggg is offline bbggg  United States
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How does the sound vary in quality from a non-ferrite coil vs an air coil used for the woofer, same spec. otherwise?
Increased distortion, mainly 2nd harmonic at low signal levels, spiced with 3rd harmonic at higher levels. Both may sound superficially agreeable some times, but it's distortion nevertheless.
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