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Author Topic: crossing over between two sub models (like SB180's and SB250's)  (Read 664 times)

James Heyser

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Sorry if this is a redundant topic, but I'm not familiar with the term for when sub-bass is separated into different cabinets.  When you don't know the right words to choose in your query, you don't get any results!

I have SB180 cabinets and SB250 cabinets.  I am planning to "choose a lane" and get rid of one set and increase my inventory of the other, but I can't help wondering what it would be like if I ran both.  I have no idea where I would cross them over, I guess that would be trial and error, but has anyone had any luck using different cabinets to handle the frequencies generally allotted to just "subs"?

In some ways this feels like a "lab light" question, but since it is sub-specific I decided to start here.
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Chris Grimshaw

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Re: crossing over between two sub models (like SB180's and SB250's)
« Reply #1 on: July 19, 2018, 04:08:15 am »

If it was mine, I'd put them on seperate Aux feeds and run different instruments to each.
They're different drivers in differently-tuned cabinets, so I wouldn't expect them to play nicely together unless you're willing to put in some heavy DSP work - you could measure both, and use an FIR filter to match the phase curves up.

The SB250 is a 2x15" tuned higher than the SB180's single-18", so if you crossed between them at, say, 55Hz and let the SB180 do the low stuff, the SB250 will have much more output further up. You could make up for that with more SB180s.

Another option is to centre cluster a load of SB180s, and use a couple of SB250s a side to give the mains some grunt into the midbass, aiming for a 60-70Hz crossover to the subs.


So, it all depends.

How many of each do you have, and what are your main speakers?

Chris
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Don T. Williams

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Re: crossing over between two sub models (like SB180's and SB250's)
« Reply #2 on: July 19, 2018, 05:01:16 pm »

+1 on Chris' last option.  Remember, if you are running the subs with more gain (louder) than the mains (and for most music that's normal), the effective acoustical crossover is higher that the frequency chosen.  There are variables, but a 70 Hz selected at the cross-over might translate to an actual 85 or 90 Hz acoustical cross-over.
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John L Nobile

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Re: crossing over between two sub models (like SB180's and SB250's)
« Reply #3 on: July 19, 2018, 07:30:25 pm »

If it was mine, I'd put them on seperate Aux feeds and run different instruments to each.


That's an interesting solution. I've been trying how to make 2 different subs work. Putting kick in one pair and bass in another is worth a try. A mini version of The Dead's system. I'm thinking kick in the horn loaded subs and bass in the front loaded ones.
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Art Welter

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Re: crossing over between two sub models (like SB180's and SB250's)
« Reply #4 on: July 19, 2018, 08:19:07 pm »

I have SB180 cabinets and SB250 cabinets.  I am planning to "choose a lane" and get rid of one set and increase my inventory of the other, but I can't help wondering what it would be like if I ran both.  I have no idea where I would cross them over, I guess that would be trial and error, but has anyone had any luck using different cabinets to handle the frequencies generally allotted to just "subs"?

In some ways this feels like a "lab light" question, but since it is sub-specific I decided to start here.
James,

Assuming you have EAW subs (SB180 and SB250 are made by various companies) they both are front loaded ported cabinets that can each use the same upper crossover up to 150 Hz.
The SB250 has an Fb (tuning frequency) of around 40 Hz, the SB180 has an Fb of 30 Hz. They will need different HP filters, but once those are applied, the phase response should still be within 1/4 wavelength even at the bottom of their frequency range, and the upper range will be nearly identical if they are simply equalized for the same frequency response from 40 Hz to the upper crossover point.

The 28,38Fb screen shot below is an example of the resultant phase difference 10 Hz in Fb makes.

Even with different designs, such as horn and bass reflex, once the path-length difference between the mains and subs are individually addressed, the phase differences may be fairly little, as can be seen in the Horn, Ported screen shot, prior to application of delay.

Using them together therefore should present no particular problem, they will constructively couple above 40 Hz, with the response between 30-40 Hz primarily from the SB180s. In other words, you'll see around +6dB output above 40 Hz (where most of the "sub" range lives) by using equal quantities of both.

On the other hand, using separate Aux feeds and running different instruments to each would reduce those instrument's available LF headroom by as much as 6 dB, no louder than if you'd left one set of subs behind.

Art




« Last Edit: July 19, 2018, 08:51:07 pm by Art Welter »
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Chris Grimshaw

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Re: crossing over between two sub models (like SB180's and SB250's)
« Reply #5 on: July 20, 2018, 04:44:26 am »

I didn't realise cabinets with different tuning frequencies would have such similar phase responses - thanks for the data.

Chris
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