Designing a crossover for a DIY speaker project

[jaygeorge1979 10+ year member]

alright guys i need some more help here...i have been browsing over alot of the DIY projects lately and i cant figure out how these ppl design the crossovers...i understnad how to build them ( i am an engineering student) but i cant figure out how they can choose a driver and know:

A. How to design the box, how big, seperate chambers, etc

B. How to design a crossover that fits the speaker perfectly

anybody wanna take a stab at teaching me?

Click to read more...

 

[thylantyr 10+ year member]

You need to buy a book to get the general idea, the topic is too advanced to cover in

one post.

Pick a random midwoofer from PE with charts and maybe we can give you a

though process on how to tackle the crossover issue, simplified.

If you really want to expedite your learning, do this;

1. Buy a woofer.

2. Buy a midwoofer.

3. Buy a tweeter.

5. Buy a Behringer DCX2496.

6. Buy 1 amplifier channel, full range.

This will be a test bench rig so you can learn FAST on what goes on.

I can guarantee that you will understand if you follow my lead.

 

[jaygeorge1979 10+ year member]

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=296-145

i chose this audax midwoofer cuz it looked kool...it has all the charts on there, so if someone could enlighten me //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

also, i have been looking at the passive crossover explanation on the12volt.com, and it has cleared a little of it up, but im still no understanding why to build them certain ways depending on which speaker you get...anyone?

thx thylantyr

 

[jaygeorge1979 10+ year member]

You need to buy a book to get the general idea, the topic is too advanced to cover inone post.

Pick a random midwoofer from PE with charts and maybe we can give you a

though process on how to tackle the crossover issue, simplified.

If you really want to expedite your learning, do this;

1. Buy a woofer.

2. Buy a midwoofer.

3. Buy a tweeter.

5. Buy a Behringer DCX2496.

6. Buy 1 amplifier channel, full range.

This will be a test bench rig so you can learn FAST on what goes on.

I can guarantee that you will understand if you follow my lead.

how much am i looking at spending? what is a behringer DCX2496? wouldnt i also need to get crossover parts/etc? how about a box?

 

[thch 10+ year member]

typically there are 3 engineering methods to use:

1.) get drivers that have a large overlap in bandwidth, then use a simple filter.

2.) use a complex, steep filter with speakers that have little overlap in bandwidth.

3.) use modeling software to find a middle ground for speakers with some overlap using moderatly complex filters.

from here, the crossover points are chosen based upon driver performance. drivers have well-known issues at both high frequencies (beaming, breakup) and low (overexcursion, T/S model). these issues help to define usable bandwidth. for instance, a speaker may have an excelent response up to 3khz, but then have a terrible response at 4khz. this means that even with a steep filter, the cutoff may need to be 2khz.

generally, filters should be below 300hz and above 3khz. 300-3khz is the most important band for voice recognition. this is only a loose rule though. i've used filters at 2khz with no issues.

 

[thylantyr 10+ year member]

how much am i looking at spending? what is a behringer DCX2496? wouldnt i also need to get crossover parts/etc? how about a box?

DCX2496 is a digital crossover. $250 shipped.

Amplifier - you choose.

Drivers {individual speakers} - you choose

Get a cheap dome tweeter, cheap midrange to start the learning process.

Connect the DCX to your source and the speaker to your amplifier and play

with the digital crossover so you can understand what happens when you

change settings.

http://www.behringer.com/DCX2496/index.cfm?lang=ENG

For DIY, I only use 'active systems', one without passive crossover because it's

elite. //content.invisioncic.com/y282845/emoticons/cool.gif.3bcaf8f141236c00f8044d07150e34f7.gif

For business, it's not practical to design an 'active loudspeaker' system, but

they do exist. It's more economical to do passive crossover design and just

hook up the speaker to an amp.

But, many DIY loudspeakers are passive crossover based too.

I prefer complete control over the drivers in loudspeaker design, hence all

active system so I can change settings.

You could develop on an active test bench to find the best settings then try

to make a passive crossover to mimick performance.

 

[thylantyr 10+ year member]

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=296-145
i chose this audax midwoofer cuz it looked kool...it has all the charts on there, so if someone could enlighten me //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

also, i have been looking at the passive crossover explanation on the12volt.com, and it has cleared a little of it up, but im still no understanding why to build them certain ways depending on which speaker you get...anyone?

thx thylantyr

Everyone has their approach to loudspeaker design. My metho involves more

listening to drivers than measuring them .. because in the end, I plan to listen

to them not measure them -- //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

I prefer a top-down approach to loudspeaker design. Start with tweeters and

work down.... because an excellent tweeter is harder to get than mids. After

you find 'your magic tweeter', find the matching midwoofer and so forth.

The frequency response for that midwoofer {midrange/woofer} you linked is

fine;

http://www.partsexpress.com/pdf/296-145g.pdf

Since my preference for audio is to use a tweeter that can perform well with

a 2khz crossover, maybe as low as 1.5khz using a steeper slope like 8th order,

we need a midwoofer than can play in this region well, with good SQ and

no nasty frequency response anomies like cone breakup modes in this region or

even higher.

The next question to ask. Does the midwoofer sensitivity mate well with your

tweeter? That midwoofer says 84dB sensitivity which is very low and inefficient.

Second, xmax is rated for 2.7mm so you need to understand that high excursion

isn't really possible with this midwoofer.

If you use a tweeter with higher sensitivity then make arranges by designing

an L-pad into the design to make sure you have a tweeter volume control to

attenuate the treble.

If you use an all active system, driver sensitivity matching is moot as you

will adjust levels on the source side.

What I like to do is make a list of driver candidates for a design and buy one

of each and hook them up to listen to them, this will be the final judging phase

on which one to choose. If you listen to enough tweeters and midranges,

you start visualizing in your mind on which ones mate better to certain drivers.

 

[jaygeorge1979 10+ year member]

wow...that really helped alot

is there anything about a tweeter that would make me want to use an 8th order crossover at 1.5kHz for the tweeter, or are you just saying that is what you prefer? once you decide 8th order 1.5khz, is there a calculator out there that tells you what value capacitor to use?

how about for the midrange...if i want it to play freq between 300Hz and 3kHz, how do you figure out how to design that crossover?

i am still trying to figure out if there are any characteristics of certain speakers or brands that help you figure out WHERE you want to cross it over...i understand that once you know what tweeter you are using, you want the mid to overlap...but how to figure out if that frequency for the tweeter is efficient for THAT tweeter?

 

[UndercoverPunk 5,000+ posts]

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=296-145
i chose this audax midwoofer cuz it looked kool...

Just for future referance, please don't ever choose anything audio based upon looks.//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[ballstothewall 10+ year member]

Just for future referance, please don't ever choose anything audio based upon looks.//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

You mean my audiobahn chrome flamed subs don't hit 189db's? What?....Liar!

 

[jaygeorge1979 10+ year member]

haha...i know...i just needed to pick one so that someone could explain to me how the system of deciding on crossovers works...which, i still dont quite get...see previous questions...

 

[ballstothewall 10+ year member]

Here is something thylantyr said in one of his posts helping me design my line array... Main thing is the link.

Or would it be better to make my own? I can solder, I just don't know anything about making a crossover.

I think it would be better.

read this and tell me what you think.

http://www.caraudioforum.com/vbb3/showthread.php?t=227180

the passive crossover design will make or break that system so

you need to choose the tweeter, ideally find one with response graphs

to determine best crossover region to use then plan a strategy.

Linkwitz Riley slopes are just better for SQ, i'd use those, but

the LR 24dB/octave is more complicated to build and cost more

because it has more parts.

It has some good information and calculators on there, I found it helpful

-Ryan

 

[PV Audio 5,000+ posts]

link is out

 

[ballstothewall 10+ year member]

Link Fixed

 

[jaygeorge1979 10+ year member]

wow...that IS beneficial...is the Linkwitz-Riley crossover the regular one that most ppl use?

i didnt know that all you needed to calculate crossovers was speaker impedance...thought it would be more complicated

i cant figure out how i would use taht calculator for a bandpass crossover for a midwoofer...say i wanted to filter out freq below 300 hz and above 2khz...how would i do that?