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Kilomax-18 [message #63470]

Wed, 21 July 2010 13:19

Wayne-o
Messages: 225
Registered: May 2009

Master

Can the Kilomax 18 be used as a sub crossed over at 250 hz with clear sound in the 100-250 hz region ?

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Re: Kilomax-18 [message #63471 is a reply to message #63470]

Wed, 21 July 2010 15:58

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

You betcha. Put it in a 10ft³ cabinet tuned to 25Hz. It will actually work well in even larger boxes, up to 20ft³, if you have the space for a cabinet that large. Give it plenty of vent area, at least 50in². That will work very well down low.

Below ~100Hz, the only things that matter are box tuning and room modes. Your main concern isn't summing, because boundary reflections come into the mix. Having multiple bass sound sources increases the number of modes, and helps average everything out.

Above ~250Hz, the sound averages into a reverberent field. Modes from interaction between the source and reflections become so closely spaced they aren't noticeable anymore. This isn't the same thing as freespace, but you still want summing between direct sound sources to be constructive. So the distance between high frequency sound sources should be made closer.

Between these two frequency ranges, you transition from discrete modes at low frequencies, to more densely spaced modes as frequency goes up, to indistinguishably close modes at high frequencies. In the transition region, between about 100Hz and 200Hz or so, the upper midbass to lower midrange, you don't really want the sound sources to be too far apart, because then you can detect the distance between them and it doesn't sound natural. But neither do you want a point source because there are still some noticeable room modes. The floor bounce notch usually falls in this range.

I tend to like having sound sources in this transition range separated by a few feet. Not tens of feet but not less than a foot either. This is a good way to get smoothing of the upper midbass and lower midrange, around 100Hz to maybe as high as 200Hz. Either run a midrange and woofer separated by a foot or two, or run a flanking sub near to the mains, just a couple feet away. Overlap them in frequency range to obtain modal smoothing.

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Re: Kilomax-18 [message #63476 is a reply to message #63470]

Wed, 21 July 2010 21:36

Wayne-o
Messages: 225
Registered: May 2009

Master

Thanks, I was looking at a smaller box 4.5 to 6.5 cu ft. Is there any problem with a smaller box?

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Re: Kilomax-18 [message #63477 is a reply to message #63476]

Wed, 21 July 2010 22:45

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

Yeah, this woofer really isn't happy with the smaller boxes. Unlike many of the JBL 22xx 18" woofers that can be used in smaller boxes, the Eminence Kilomax 18 peaks in the midbass and low bass drops off fast when used in a smaller box. If you need to go with a 6-8ft³ cabinet, I'd probably look for a different woofer. Maybe go with a 15" woofer instead.

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Please forgive my jumping in... [message #63481 is a reply to message #63470]

Thu, 22 July 2010 12:11

GarlandB
Messages: 27
Registered: July 2009
Location: Natick, Massachusetts

Chancellor

...but I have a couple of Eminence delta 15s and a couple of Omega 15s. Can either of these woofers be used in a small box for sub-woofer duty with my Pi 4s? I'd probably prefer to use the Omegas and keep the Deltas for use in my old Theater 4s.

Thanks for any advice!

Garland

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Omega 15 and Delta 15 [message #63483 is a reply to message #63481]

Thu, 22 July 2010 13:02

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

The Delta 15 needs a huge box for subwoofer tuning, so that's probably out. I wouldn't use the Delta 15 in anything smaller than about 5ft³, and even at that, it's really a midwoofer, not a sub. To get the low notes out of a Delta 15, you really need a box that's like 20 cubic feet or so.

The Omega 15, on the other hand, makes a capable sub when put in a moderately sized 5-8ft³ box. The Omega 15 is one of those woofers that can do midwoofer duty in a 2.5³ to 5.0ft³ cabinet tuned to 38-40Hz or as a subwoofer in 5.0ft³ to 8.0ft³ tuned a smidge lower, around 35Hz.

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Re: Omega 15 and Delta 15 [message #63488 is a reply to message #63483]

Thu, 22 July 2010 18:51

Wayne-o
Messages: 225
Registered: May 2009

Master

Ok, If you had your midhorn that started to cutoff at 225hz and a woofer with a high cutoff at 250hz how close would you want them for the best summing ? Thanks

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Re: Omega 15 and Delta 15 [message #63489 is a reply to message #63488]

Thu, 22 July 2010 19:01

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

The midhorn doesn't cutoff firm at 250Hz, but rather has a fairly gentle rolloff down low. I like to overlap the midhorn and bass bin, to run the midhorn down as low as it will go and use a slow LP rolloff, usually just a ~5mH series coil. The midhorn and woofer are separated by a couple feet, and aren't in the same position in any of the three planes. This provides some modal smoothing in this range, eliminating the floor bounce notch, etc.

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Re: Kilomax-18 [message #63490 is a reply to message #63470]

Thu, 22 July 2010 21:47

Wayne-o
Messages: 225
Registered: May 2009

Master

Ok, Pure Genius! If you crossed them over at 500hz could you put them closer together like 5-6 inches?

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Re: Kilomax-18 [message #63495 is a reply to message #63490]

Fri, 23 July 2010 08:05

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

That would remove the modal smoothing. You need the distance to provide the smoothing. You also couldn't get the midhorn that close to the woofer, it's too large.

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