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Need help with crossover design [message #67035] Wed, 13 April 2011 12:09 Go to next message
endrek is currently offline  endrek
Messages: 2
Registered: April 2011
i want to build this speaker design:

but i want to change the HF compression driver + horn .

Which parameters should i look?? Dispersion? Same sensitivity?? Any advice please?? Wich parameters should be good with the two woofers from the speaker??


THX for all
Re: Need help with crossover design [message #67036 is a reply to message #67035] Wed, 13 April 2011 12:11 Go to previous messageGo to next message
endrek is currently offline  endrek
Messages: 2
Registered: April 2011
I'm working on a X12 from Speakerplans.com
and i'm doubting of some things,
first of all, wich type of filter should i use if i want to make a pasive filter? Wich order? wich type?(with wich type i mean, bessel, butterworth,etc.... (my knowledge about electronics, isnt really good)) Sad

And the other question is, at what frequency should the filter separate the 2 woofers freq from the horn-driver???

possible answer:
1) You can ask the designer Smile
2) You can use an electronic crossover ,since it's a PA design it may be appropriate .
3) You can use the magic formulas that give you the values ,which may be adjusted later when listening and not finding them good enough.

but :

1) designer isn't avaible at his email Smile Smile
2) if i use a electronic XOVER (DSP right??) i will need to put two connectors to the X12 right? so i can separate the signal into MF and HF right? Or can i separate it with just one connector?? any advices please?
3)About the magic formulas, i'm starting to look/learn about it. Any good site to look? or cookbook?

the speakers are intended to be for high volume application, as loud as possible hehe.

My final goal is:
I'm building 2 bassreflex box with Fane Colossus 18 XB driver each. (40-250HZ aprox.)
And i'm building two X12. Thats why i'm thinking of a passive filter inside the X12 to sseparate MF and HF.
And I'm going to buy the correct amplifiers for them and a digital XOVER/COMP/LIM/EQ (DSP) for the all the PA
Any suggestions?? Or wich should be the better configuration???What i'm doing wrong? What can i improve?

pd: don't be cruel, i'm newbie, and i'm starting to learn everything Smile
thx for your help Smile
Really appreciate you can take me to the good/best goal Smile Smile
Re: Need help with crossover design [message #67037 is a reply to message #67036] Wed, 13 April 2011 14:04 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 17776
Registered: January 2001
Illuminati (33rd Degree)

You've asked a lot of questions, and there's a lot to cover.

Here are some answers, at least hitting the high points:

First, there are a lot of interactions in a loudspeaker that prohibit casual choices of drivers, horns and crossover topologies. If you don't want to enter into a design/test development cycle that may take some time, you might be better off with a stock design, without any changes. Find a manufacturer and/or designer that you trust, and stick with the plan.

Then again, a loudspeaker is a simple machine, and you can "play around" without doing too much damage. You may not get the best performance, but it will be a learning experience. If you want the best performance, you'll need to do some research, make some educated choices and then optimize the proposed design with models and measurements.

Horns are usually chosen for the directivity and/or loading characteristics. Basshorns are usually chosen by their acoustic loading. Midrange and tweeter horns are usually chosen for their directivity. There are some other concerns, but the main things are acoustic loading and directivity.

HF compression drivers are generally chosen for their passband and their diaphragm breakup characteristics. Voltage sensitivity is a small consideration, and of course, the average impedance. Those two things are inter-woven. Basically, you can expect all compression drivers to be pretty close in voltage sensitivity, and the couple decibels difference is easy to compensate in the crossover. But the size of the diaphragm sets its upper limit, and the composition of the diaphragm, its material and shape sets its breakup modes, how it acts at the top end, above its mass rolloff point. Phase plugs are also a consideration, but really, most of the modern units are similar.

The crossover is the brains of any loudspeaker. If the drivers are its heart, the crossover is its brains. It is not a trivial matter to design a crossover for a speaker, nor is it something you can discuss intelligently without detailed knowledge of the loudspeaker cabinet, the physical relationship between drivers and the electro-mechanical properties of the drivers, themselves.

Some people take the strategy that using active crossovers, they can work through any acoustic kinks they may encounter. I suppose in a prosound environment, where some anomalies are acceptable, this is probably a reasonable approach. You can get the basic tonal balance right and leave it at that. But to get the best summing, to make the forward lobe clean and put the nulls and outer lobes well outside the listening area, you need to be able to optimize the crossover more than just setting up crossover frequencies and maybe turning on a CD compensation switch. There is potential in DSP, certainly, but it is rarely ever realized.
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