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WHY NOT REFLEX? |
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airbell 
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Joined: 11 June 2009 Location: Berlin, Germany Status: Offline Points: 285 |
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 Topic: WHY NOT REFLEX?Posted: 20 October 2011 at 10:01pm |
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Well i considered this to put it in advanced discussions, but well,
can someone explain why all front loaded mid horn tops are not also reflex loaded? i mean to put a port from the rearchamber to the front of the box, like a hybrid..... what are the disadvantages? phase stuff, delay...? or is it just simply that most efficient mitrange driver have not enough xmax to do enough bass for the reflex part? thx |
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Dref
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Joined: 05 April 2010 Location: Denmark Status: Offline Points: 287 |
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Posted: 22 October 2011 at 11:24am |
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There are many aspect to it i would say.
Whether it is an advantage or not to port the rear chamber depends on what one want to achieve. If the drivers parameters is suited for the use in a ported horn then the result will typically be that the system can go lower when the rear chamber is big and ported but the efficiency up higher will be a little less than the horn with a small closed rear chamber. The response will also typically be a little more uneven. (How much depends on how well the driver is suited and how well the system i tuned.) An example could be my 2 x 12 exponential horns.  They have a big rear chamber with ports in the front (next to the hf horn). But they also have a kind of a hatch in the back, making i possible to change to a small closed rear chamber. When used in port mode the system is tuned to 70Hz, making it useful as a standalone system in a small indoor environment. But when used outside in 2 or 4 Pi environment, the response gets quite peaky. Then the system can be changed to closed rear chamber giving a much flatter response and about 2db more sensitivity. In this case the horn is only useful to around 100Hz. I usually cross them at 112Hz when used with a closed rear chamber.
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djeddie
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Joined: 26 April 2004 Location: Bristol Status: Offline Points: 4125 |
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Posted: 22 October 2011 at 12:29pm |
Clever idea.  Edited by djeddie - 22 October 2011 at 12:29pm |
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Chas n Dave : it's like Drum and Bass but with beards. E=mc² ±3dB
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CCAV
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Posted: 22 October 2011 at 8:42pm |
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Nice Cabinets Like the top box. Are these something you want to share?
Will |
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In my early years my favorite phrase was "If it's too loud your too old" Now I'm just too old
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Dref
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Posted: 23 October 2011 at 12:24pm |
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I am sorry but the only plan i ever made for these where a hand drawing
 I could scan it in for you one day if you like, but that should be in another tread
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CCAV
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Posted: 23 October 2011 at 4:09pm |
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I'm trying to decide on building an MT 122 or MT 130 type of box this would give me another option for either type I'm presently using 6 CBe-18 Cyclops in the sub area. So if you get time please scan It would be very helpful While I'm not great at design I do like to build But I'm always trying to learn and sooner or later I'll get the design thing down
William |
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In my early years my favorite phrase was "If it's too loud your too old" Now I'm just too old
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CCAV
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Posted: 23 October 2011 at 4:13pm |
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I was always wondering about what to do with all the wasted space around the hi Driver in these designs And this could be a great option
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In my early years my favorite phrase was "If it's too loud your too old" Now I'm just too old
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Dref
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Posted: 23 October 2011 at 5:48pm |
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Okay i think i will just post it here. Its still sort of related to the thread.
I changed a few thing on the final design, but here is original drawing:  And then a slightly modified drawing with some measures:  They are made with 20mm panels. But if i had to build them again i would use 18mm ply. The 12" speakers is mounted on a separate detachable baffle with round holes. Originally i would have made them with phaseplugs, but i tried one baffle with phaseplugs and one without and found that the drivers i used didn't go above 1000 Hz that well either way. Therefore i made the the baffles without phaseplugs and used a big 2" driver for the highs. Another reason for using a crossover frequency as low as possible is to keep the dispersion at a acceptable width. These long exponential horns has a very narrow dispersion if crossed over at high frequencies. I know this drawing isn't enough to build an exact copy of the horns i build, but i wouldn't recommend doing that any way. You should tweak the design to suit your needs. Considering how low they need to go, what dispersion you need, what size you can live with and what drivers you will use.
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CCAV
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Posted: 23 October 2011 at 6:29pm |
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Thanks
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In my early years my favorite phrase was "If it's too loud your too old" Now I'm just too old
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AndyWave
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Posted: 23 October 2011 at 6:32pm |
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Hi Dref
What drivers you use in your design? I've done something similar to go with my miss piggy subs. (other 12"in its own cabinet, other 12" with big 1,5" "tweeter" in other cab) I tried reflex rear chamber, ports on back wall, but didn't like the sound when tuning was high enough to give acceptable level rise in 90-150hz area. Teunos was trying something similar at the same time and he got the sound he liked. I think that reflex tuning frequency cannot be very near of the tuning of the horn part. Phase response sounded screwed in my experiment, lacking clarity and punch. To airbell About the driver parameters, when the horn is bit longer than in MT122, the driver can have more Xmax (2mm vs 6mm) and maybe bit heavier cone (35g vs 50g), more suitable for additional reflex rear chamber. Midrange (<1kHz) sensitivity still keeps up. These are for example only values in brackets. Look something like 18sound 12ND930, B&C 12NDL76. Andy |
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torturing electrons since ......
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Dref
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Posted: 23 October 2011 at 7:07pm |
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Hi Andy
At the moment they are loaded with Kenford PA 12" DYD300B-4-67. It was the driver the horns where design to initially. I have also got some B&C 12PE32, but i have choose to let the kenfords stay because they actually works unbelievably well. One should never trust the specs given for these cheep drivers. I think they are actually very similar to Eminence kappa 12A.Actually i haven't tried to tune the ports high because my sims showed that it would give me a big peak in group delay around the all important kick frequencies. I have tuned mine to 70 hz and then i only use them in port mode when i can find some nice corners to place them in. (this removes most of the dip) About drivers for this type of ported mid horns. I would recommend not using hardcore horn drivers with very high Bl, because then the dip between the port and horn tuning will get to big. Again, something like Eminence kappa 12A would work well in these designs.
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airbell
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Posted: 25 October 2011 at 7:14pm |
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Hey Dref,
have to agree its a very nice idea with your tops ! something similar like this i was thinkin about :) i know hornresp is not good for mid cabs, but do you know what the hell happens to the phase response if you put a port in it??  i surely dont think its reality what it predicts, but it looks strange.... For the rest it looks exactly what was described here; little bit more honky ect... what do you think how many 12" well loaded reflex tops (lets say 1x12") would be necessary to keep up with a single usb in reality??? and.....are you serious?  Kenford PA 12" DYD300B-4-67???Its around ~30€. Would you really recommend a try for professional usage? Fritz |
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Dref wrote: