2.5 way crossover

[memphissound]

Can someone tell me or direct me to information about 2.5 way crossovers? Thanks.

peace,
memphissound <><

[rabbitz]

To understand the use of a 0.5 woofer, you have to understand baffle step as the 0.5 woofer provides correction for these losses. Have a read of these as will give you some background.

http://www.t-linespeakers.org/tech/b...intro-bds.html

Box designs that address baffle step?

Baffle step correction circuit - how to design?

I've found it's best to crossover the 0.5 woofer between 150Hz - 200Hz for a box width around 200mm. All you need is a 1st order crossover using a single inductor to the 0.5 woofer. The inductor value is calculated using the impedance at the crossover frequency and not the nominal impedance of the woofer.

For other box widths, I use this fudged forumula that was derived from tests.

0.5 woofer crossover freq = (115/baffle width in metres)/3.1416

If you find you are getting too much BSC you can reduce the woofer SPL with an L-Pad.

[memphissound]

Thanks for the info.

I tried a couple of "Searches" but could figure out the right stuff to put in for the terms.

peace,
memphissound <><

[Daveis]

Originally posted by rabbitz


I've found it's best to crossover the 0.5 woofer between 150Hz - 200Hz for a box width around 200mm. All you need is a 1st order crossover using a single inductor to the 0.5 woofer. The inductor value is calculated using the impedance at the crossover frequency and not the nominal impedance of the woofer.

For other box widths, I use this fudged forumula that was derived from tests.

0.5 woofer crossover freq = (115/baffle width in metres)/3.1416

If you find you are getting too much BSC you can reduce the woofer SPL with an L-Pad.

Ok, so the .5 woofer should be mounted on the back??? Is there any reason it couldn't go on the side or front?

Why couldn't you use the same low pass crossover for the .5 woofer as for the main woofer? (wire in parallel)

[Salas]

Originally posted by rabbitz
If you find you are getting too much BSC you can reduce the woofer SPL with an L-Pad.

Doesn't it alter the system Q? I think it does. Resistance does so to woofers. So the box must be altered too.

[rabbitz]

Originally posted by Daveis


Ok, so the .5 woofer should be mounted on the back??? Is there any reason it couldn't go on the side or front?

Why couldn't you use the same low pass crossover for the .5 woofer as for the main woofer? (wire in parallel)

Can go on the front and the back is a very good option for various reasons but needs room behind the box. Side is no good as it's reproducing frequencies that are directional and can be located unlike a sub.

The other woofer would be crossing over at a higher frequency such as 3000Hz and you don't want the 0.5 woofer crossing over there or you end up with a pseudo MTM. If you wire it in parallel to the other woofer, the impedance is halved and the existing crossover is cactus.

I've found that a gentle 1st order crossover works best for the 0.5 woofer and I crossover at about a third of the baffle step F3 frequency. This way you don't get a boost above that F3 when combined with the main woofer.

[tinitus]

Krutke thinks that it makes fore a better phase if the 0.5 woofer is connected through/after the "fullrange" woofer

http://www.zaphaudio.com/Waveguidetmm.html

[rabbitz]

Originally posted by salas


Doesn't it alter the system Q? I think it does. Resistance does so to woofers. So the box must be altered too.

An L-Pad maintains a constant impedance but does have an effect on bandpass filters. The 0.5 woofer only uses a LP filter so should have no major problems. If in doubt, a zobel could be used to provide the initial impedance correction so it's smooth sailing for the L-Pad.

A series resistor does have an effect and how much of course depends on the amount of attenuation. I take advantage the series resistor altering the Qts for OB use.
http://www.diysubwoofers.org/dipole/design.htm

[Salas]

So everything must follow a master plan. You adjust as an afterthought, it takes yet another alteration. That was my point.

[rabbitz]

You are right. Good planning is the key and have to be very methodical for good results.