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jaygeorge1979
11-06-2005, 08:36 PM
ok...i finally think i understand the concepts of designing speakers: this is just something i have put together using stuff i have learned...someone help me fill in the holes:

You choose drivers…

You look at freq response graphs for drivers…

You figure out where the graphs get ugly and mess up, choose a crossover point which does NOT include the bad parts

Use a crossover calculator to figure out which caps/inductors to use and how to design filter

Using T/s parameters, and a box building computer program, compute box dimensions.

Rest of design is up to me

what am i leaving out? i know this is a basic overview...im just trying to generalize it into lamens terms so i can understand...

thylantyr
11-06-2005, 09:17 PM
You choose drivers…

This is important especially finding the right combination of drivers to give
best synergy across the audio band.

You look at freq response graphs for drivers…
This tells a tale about the drivers but doesn't tell everything. You have to figure
out what region the drivers work best in, ie a cheap mylar tweeter will probably
be crossed over at 5khz or higher where a quality dome might work down to 2khz, or
a horn driver may work from 2khz and up but drop off beyond 12khz... etc ...

One you figured out the basics you can rule out combinations that don't work
and focus on ones that might work.

You figure out where the graphs get ugly and mess up, choose a crossover point which does NOT include the bad parts

The crossover is the minimum requirement, meaning it will pass high frequencies
to the tweeter and only pass midrange frequencies to the midrange drivers and
pass lower frequencies to the woofers. This would be a 3 way example.
The crossover is like a frequency splitter sending the signal to the proper drivers.

There are different types of crossovers;
http://www.audioholics.com/techtips/audioprinciples/Loudspeakers-Crossovers.html

Four type shown.

Then, there is different crossover slopes on can use, 6dB, 12dB, 18dB, 24dB, etc.

So, once you figure out which type you want and which slope for a particular
design the next step is to figure out if the drivers themselves have issues within
their operating range and if you have problems you have to change your
mind on crossover type and/or slope, perhaps add more electronic circuits [filters]
to fix the response [EQ it].

Then, you have to look at the impedance of the driver across it's passband
to see if it drifts from nominal as you may have to add a zobel network to help
keep impedance more constant otherwise if impedance drifts alot, your crossover
point changes.

The crossover design will make or break your system if you don't get it correct.
Now, since this is DIY the active setup is superior because many of these
issues are easy to solve.

For example, using a digital crossover in a active system;

*You don't need a zobel as impedance variation doesn't matter {unless you
are using a sensitivity tube amplifier that doesn't like lower impedance}

*Filter type/slope can be selected in real time.

*Crossover frequency can be changed in real time in increments.

*These digital crossovers have parametric EQ's to fix issues if needed.

While this is cool you still have to understand what you are tweaking.

Most people that make loudspeakers just pick drivers that might work
well together and try to use simple crossovers to keep it simple, so
passive crossover design can be easy if you have drivers that are 'easy'
or it can be a PITA if the drivers you choose are difficult to work with.

If you really want to understand this, you need a active crossover test bench
otherwise it will take you forever to really understand what is going on.

There is also the 'full range driver camp'. Where you use 1 driver to cover
the whole audio band without using crossvovers. The problem facing this camp
is getting high end and low end extension.

jaygeorge1979
11-06-2005, 10:17 PM
"Then, there is different crossover slopes on can use, 6dB, 12dB, 18dB, 24dB, etc.

So, once you figure out which type you want and which slope for a particular
design the next step is to figure out if the drivers themselves have issues within
their operating range and if you have problems you have to change your
mind on crossover type and/or slope, perhaps add more electronic circuits [filters]
to fix the response [EQ it].

Then, you have to look at the impedance of the driver across it's passband
to see if it drifts from nominal as you may have to add a zobel network to help
keep impedance more constant otherwise if impedance drifts alot, your crossover
point changes."

how do you figure out which crossovers to use ( out of the 4)....how do you figure out which slope is best? how do you figure out which crossover and inductor to use in a zobel network and how do you connect that to the crossover?

thylantyr
11-06-2005, 11:17 PM
how do you figure out which crossovers to use ( out of the 4)....how do you figure out which slope is best?

Crossovers are not without flaw, they have their pros/cons and you have to
determine what will work for your design. The Linkwitz-Riley type is popular
because it's the lesser of the evils. But are you limited in slope selection.

These crossovers are not brick wall in spitting the frequency range, rather they attenuate the frequency. The steeper the slope = more attenuation. You have to
determine how much attenuation will work for the design. Also, steeper slopes =
more electronic parts to make it work.

Lets use the Seas Excel 8" midwoofer as an example. Some folks like this midwoofer but it has nasty cone breakup modes in the upper frequency range.
If you were to use a narrow slope you will still hear the nasties and it would force
you to use a very low crossover point rendering the design useless. But if you use
a steeper slope you can raise that crossover frequency higher to the range you
want to operate the driver and still provide good sound as the nasties won't
be as annoying.

Lets use my PT2 line array as an example. Nobody in DIY land will use the PT2
planar under 2.5khz with 4th order {24dB/octave} because the driver isn't
really designed to give you high performance at a lower frequency and you
may introduce more distortion if you drive it hard. But, if you use an 8th order
{48dB/octave} you can lower that crossover point down to 1.7khz as the steeper
slope 'filters' out the midrange crud that makes the driver sound nasty and
the lower crossover point can improve stereo imaging. Most hardcore loudspeaker
designers prefer a tweeter that can work lower in frequency, ie in the 1.5khz - 2khz range. You don't see many serious designs where the tweeter is crossed over much higher, like in the 5khz range. There are exceptions like super tweeters
but if you do use a tweeter that only works good with a crossover at 5khz,
this forces you to find an exception midrange to work well in this region. I think
you get better stereo imaging when you have a lower tweeter crossover point
provided that the tweeter has high dispersion.


how do you figure out which crossover and inductor to use in a zobel network and how do you connect that to the crossover?

There are online calculators that do zobel calculations for you.

More food for thought:

Give 10 people two tweeters, two midranges, two woofers and ask them
to design a passive crossover for a 3 way loudspeaker. What will happen is this.
Each person will most likely have a different design and each system created
will sound different. Same drivers, different sound due to different crossover design.

The artistic part of loudspeaker design is how you crossover the system. If
you ask other people the same questions you asked here, you'll get different
answers as each person has different methods.

The best way is to understand what sound you get by examining the behavior
of different types of crossovers using different slopes and crossover frequencies,
then you can visualize in your mind what combination gives you the sound you want.

On the other hand, other people design their system on software so it's 'technically' correct and settle for the sound it gives. I prefer a different approach,
buy only good sounding drivers and try to mix/match to get the sound you like.

jaygeorge1979
11-07-2005, 02:07 PM
i want you to know that you have been a HUGE help...i am very impressed

you earlier mentioned to me the need to purchase a behringer active crossover system for like two hundred fifty bucks...i am interested, but im not sure i want to put out that much cash...are there cheaper, perhaps used (ebay) active crossovers that will allow me to do the same kind of testing?

also, the zobel network...i found the calculator, but i cant figure out:

1. If the D. C. resistance it asks for is just the impedence of the speaker (say, 8 ohms)
2. How to figure out what is the voice coil inductance

come on thylantyr...i know you know :)

thylantyr
11-07-2005, 11:44 PM
need to purchase a behringer active crossover system for like two hundred fifty bucks...i am interested, but im not sure i want to put out that much cash...are there cheaper, perhaps used (ebay) active crossovers that will allow me to do the same kind of testing?

If the Behringer DCX2496 didn't exist, choices would be a $500 DBX product
or $1000 Rane product. The prices rise. There is even a $3000+ DEQX.

$250 shipped {no tax} is a bargain for such a powerful unit when you look
at alternatives.

For $120 you can get a generic analog crossover with only 24dB slopes
and some knobs to turn on the front panel. For $250, the digital crossover
gives you 100x more power for double the cost.

Behringer product is considered entry level in the pro audio industry because
they associate higher prices with sound quality when there really isn't a correlation, but
Behringer would be above Pyramid, Pyle, Gemini and other rock bottom brands. Basically, with
Behringer you have to choose product wisely as not everything they make
is a gem. The DCX2496 and the DEQ2496 are two gems in turd clothing.

I would take this gear and challenge any audiophile with golden ears to see
if they would pass a neutrality test with this gear installed in their system, it's
dang good for the money. It use to cost $350 plus shipping years ago when
it was introduced.

also, the zobel network...i found the calculator, but i cant figure out:

link?


Keep in mind, when interfacing home audio gear to pro audio gear, there is
preamp voltage level issues to deal with. Generically speaking, home gear is
in the 2 volt world on preamp signal and pro audio gear is in a 10 volt world
so a home audio source may not drive the pro gear well when it expects a higher
voltage to get the best performance out of it. I've done tests with the DCX and it
works well even with lower voltage signals in spite of what the elder audio-geeks
claim.

I've also done digital and analog pathway comparisons to see what the hype
is all about.

http://www.caraudioforum.com/vbb3/showthread.php?t=223239&highlight=roland+m1000

Database of DCX2496 babble;
http://www.caraudioforum.com/vbb3/showthread.php?t=219105&highlight=roland+m1000

jaygeorge1979
11-08-2005, 12:11 AM
http://www.carstereo.com/help/Articles.cfm?id=36

this is for the zobel network...i still dont know about the inductance or whatever...do u use these things for all drivers? or just certain ones? how do you determine...

I wasnt aware that the behringer was such a good deal...i am very interested i getting it, maybe with some christmas money...i cant wait to start playing

thylantyr
11-08-2005, 12:30 AM
http://www.carstereo.com/help/Articles.cfm?id=36

this is for the zobel network...i still dont know about the inductance or whatever...do u use these things for all drivers? or just certain ones? how do you determine...

I wasnt aware that the behringer was such a good deal...i am very interested i getting it, maybe with some christmas money...i cant wait to start playing

send me email to thylantyr at hotmail dot com.

I have a very basic noob guide on the DCX on the front panel buttons and LCD
menus.

re: zobel

To use this calculator, enter the D.C. resistance and the inductance of your driver, click the "Calculate Values" button and the required component values will appear in the remaining text boxes.

Enter D.C. Resistance Ohms
Enter Voice-Coil Inductance


Look at the manufacturer specifications to find the driver's DC resistance
and voice coil inductance. Enter the values and press the button to get
the resistor and capacitor value.

jaygeorge1979
11-08-2005, 10:23 AM
ahh....i didnt know those were manufacturer specs...i thought maybe i had to calculate em...check ur email :)