Crossover design

Finished the speaker design choices, now it's off to the hard part for me....I'm foreign to crossovers. I got some calculations on a Third Order two system...
C1=386.1mf
C2=1158.3mf
L1=27.1mh
L2=55.6mh
L3=18.5mh
C3=772.2mf

Here is the site http://www.globalnode.com/users/stevenr/spkrs/
let me know if you need more info, drivers, etc.

Couldn't I go with a more simpler xover??? How do I decide on the order things???
 

CHRIS8

Disabled Account
2001-12-12 8:47 am
VA, USA
Please remember that those are the formula, that while accurate...must be used considering for the acoustic response of the driver and it's frequency dependant resitance (impedance). In reality, those equations are only the electrical crossover frequencies. They could only be used in real life if you had a nearly resistive drivers with flat frequency responses extending 2 octave or more past the intended cross point. While such drivers do exist, you would have to search for them and then pay an arm and a leg to actually aquire them.

You will need to plot impedance, measure freqency response, sensetivity of the drivers on a test baffle(the same size as the intended finished design) and then design the initial crossover design with that data. This is not pratical to do manually today. Use computer program such as Speaker Workshop to speed up the processes. http://www.audua.com. There are of course others, but this one is free.

After you have reasonably accurate data and have a design to start from, then order your parts.

Another option is to make active crossovers, and provide a dedicated amplified channel to each driver. You may find some pro gear xovers useful, as many have infinite variable xover frequencies and digital delay to account for time/phase alignment..this would definately make things almost too easy.

Also, don't forget to account for baffle step when designing the crossover, or correct it at line level(much better IMO).j

All of the information that you need to make your own active crossovers as well as baffle step compenstion can be found at: http://sound.westhost.com

Of course, there are many other issues but it is not practical to even mention a small fraction of them. You really should do more research before building a design from scratch as to minmize your costs and trouble. You can find some good links from the main 'Speakers' link on the home page of diyaudio.com to get you started.

Why don't you build a predesigned DIY speaker first, then you can have a reference point and play with the crossover values in it, change the box tuning, etc. in order to get your feet wet.

Build something cheaps first, like the Dayton projects at: www.speakerbuilder.net

Have fun.

-Chris
 
cutting off bass below 50Hz is rather difficult to do using passive crossovers. trust me I tried. why do you want to limit bass to 45Hz?

I tried to limit bass (using a 1st order passive) to aa 6" woofer (ScanSpeak) and found that it was not required the XO offered little protection.

If you are building a 3 way or your midbass is very limited in the bass then you can move the XO point upwards (80-100Hz would be better).

If you want to limit bass to the entire system use a bass blocker cap/network available readymade with RCA plug attached at www.crutchfield.com.

Hope this helps.
 

griff

Member
2001-12-27 4:01 am
Melbourne
HELP ME!!!!!

hmmmm, please help me, ive got no idea

can u plz recommend me a Xover, im really stuck, im an extreme beginner, this is my first project, as i said above, i am using the Audax TW025A16 tweeter specs and the Seas CC17RCY H624 specs

thanks in advance for your much needed help, it will be a 13.5l box, studio moniter styles, any help would be much appreciated, values and design etc.
 
rules of thumb.

XO should be aprox 2 times resonance freq. of tweeter.

as a start stick to 2nd order corssovers. they offer enough protection and are not too complex.

The way I see it the woofer you arre using would prefer to be crossoed over at about 3k and 110hz. The 100hz is because the Sd (area) and Xmax (mm) are very small.

You will need a 8 or 10" woofer to fill out the bottom unless you want a system that is extremly limited in SPL.

You may try starting with a low Q (Linkwitz Riley 2nd order) with these drivers at 3000Hz. See if you like that and then work from there.

hope this helps.

Regards
Navin
 
given your drivers I think you can do the following.

1. build a pair of speakers that are extrmely limited in SPL.

2. add a 8 or 10" for the bottom 2 octaves (30-120hz).

If you are using option 1. a simpel 2 way XO at 3kHz will do.
The crossover will have to have the following.

1. difraction compensation that can be simply done by using an oversize inductor in series with the woofer. The exact value is dependent ofn the baffle width.

2. impedance compensation for the woofer.

3. level damping for the tweeter about 3db would be nessacaryy.

If you are using option 2. then things are a bit more complex.

To limit frequenices at 100Hz to the 4" if not cheap of simple. I would even suggest that you consider XO frequencies of 200hz and 3000Hz as your starting points only because 200Hz requires smaller values.

follow simple rules.

1. keep the 2 frequenices atleast decade apart (300-3000) etc... or there will be interplay between components in each crossover.

2. the difraction compensation gets a bit complex but for most part it will only affect your 4".

3. the tweeter padding will still be there

4. the 8-10" woofer would have be well matched in level to the 4" (a few db less than the 4" is better) as any level matching in the 8-10" using Lpads, resistors etc.. will seriously affect dampling factor of the bass.

5. download LSP cad demo and play with it to understand what various components do.
 
yeah i know 14 cm is 4" so that is why I recomend a higher freq. than 45-60Hz.

100-120Hz is the minimum. I perfer 200hz ot keep XO price down if you are using 8-10" woofer for last 2 octaves.

One very interesting cabinet design is what Roy Allison did with the Allison 9. This was copied a bit by Jim Thiel in the Thiel CS3.5 I perfer a combination of both.

DO you have a fax number I can fax you a sketch?

are we on the same page? if you need to contact me direct try navin@vsnl.com
 
5" or 6" either way it is a driver with limited Xmax and limited Sd whihc limits the ammout of SPL esp below 60Hz.

Building a Hihg pass XO at 60Hz is expensive.

1. a 12db network is expensive
2. a 6db network hardly offers any protection

best is to use a active network if you want to limit freq. to 60Hz.

you can get active network+amp for cheap since bass amp does not need to be very accurate, delicate, etc. There are many on the net. some as cheap as $100-150.
 
I believe in keeping things as simple as possible.

although I have heard speakers with some awful complex crossovers that sound nice this is not for beginners or even intermedite speaker DIYers as most DIYers do not have the equipment to build/design speakers.

For example one would need a dedicated setup that consists of a good signal generator, stand mounted mic, PC card to store data read from mic and a software like MLSSA to analyse this data. And that is for starters. One would need access to materials suppliers (ceramic, wood, steel, etc...) and fabricators etc.

A DIYer must learn to trust his/her ears. I still believe this is the best measuring device made. I have had expereinces wiht relative novice music lovers who can discern small (0.5db) differences in the midrange (changing a resistor in a LR difraaction compensation circuit from 3.3ohms to 4 ohms). My wife is my testing ears. Since I am the one doing the soldering I know my opinion will be biased so I use her ears.

Enjoy!
 
ok navin, time to get serious here.

I am now into building a MTM centre channel, and i would love your assistance if possible.

I have a couple drivers combonations that i am throwing up,

1) SEAS CC17RCY x2 with an AUDAX TW025A16
2) VIFA P17WJ x2 with a VIFA D25AG

What do you think of these combonations?

I intend on building after this a Shiva subbie, then floorstanding TM moniters, then finally loudspeaker mains, hopefully with all the same drivers bar the subbie. Budget is of concern, if i could keep driver cost down to around $250 AUD it would be really appreciated by my wallet.

Thanks in advance