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-   -   Crossover design (http://www.diyaudio.com/forums/multi-way/123271-crossover-design.html)

hybridfiat 18th May 2008 04:35 PM

Crossover design
 
OK, Im going to reveal my ignorance here so be kind.
I have tweeters and woofers (Peerless: 2x P810921 1"tweeters and 4x 830883 6.5"woofers).
I wish to use pre-made crossovers as Im not an electrical engineer.
Now the question, is it possible to "tune" the crossover by replacing a component until the desired separation of frequencies is accomplished and the sound is right?:xeye:

Dave Bullet 18th May 2008 09:33 PM

Is it possible? yes. But how hard (without the ability to measure) depends on how well trained you are with music, identifying anomalies over a particular frequency band of annoyance, your knowledge of the behaviour of your specific drivers and how sensitive your ears are.

For most of us - that would be as easy as finding your way through Fangorn forest blindfolded without legs. :)

Worst case - you could blow your tweeters ($160+ shipping of damage) and blow your amplifier.

The drivers you have are worth implementing properly (they are good drivers). You don't want to "fry" your lovely Peerless 810921 with a guessed crossover. Another possibility is your initial guessed crossover could present a low load to your amplifier and cook that too.

An off the shelf crossover at the very least will not account for your specific drivers impedance - remember changes in impedance greatly affect crossover behaviour.

The options (most to least preferred):
1. Find an existing design using those drivers and implement that

2. Ask someone (like Jay) to simulate / model a crossover for you. You would need to let that person know the cabinet constraints (size) and driver layout you want. A 2 way MTM or 2.5 way TMM are possible. Or they could work it out for you....

3. Cannibalise 2 different designs that use those drivers. ie. "Copy" the woofer circuit of one MTM design usign the 830883, and copy the tweeter leg of another design using the 810921.

Whatever you do - make sure you measure impedance across the terminals of your completed speaker before you plug it into an amplifier to make sure you don't have a short somewhere and apply low power initially.

Cheers,
David.

Ron E 18th May 2008 10:33 PM

My recommendations, in order of preference.

1) Join or start a local audio club. You will certainly find people as interested in audio as yourself. One or more of them may help you with design and measurement.

2) Spend time learning Speaker Workshop or some of the other free design/measurement tools.

3) find a happy medium between the rolloffs of the low and high frequency drivers and design a cookbook crossover with zobels and experiment with tweeter polarity and padding to get a good balance. Do a lot of trial and error listening to lots of music and comparing your speaker to a known good reference speaker to try to get a good balance.

Dave 18th May 2008 10:58 PM

Off the shelf crossovers are a pretty poor solution.
Your best bet it to try and find an existing design that uses those drivers.
If your are going to design your own crossovers you need the right tools. I use SoundEasy V14 with John K's guide. The mic I use is based on a panasonic capsule. This does give very good results.

I think anyone who wishes to build speakers but does not have the tools to properly design a crossover should look to build an exisiting design or go with a kit. There are plenty to choose from.

Dave 18th May 2008 10:59 PM

Oh and I also a use a ESI Juli@ soundcard which works great.

rabbitz 19th May 2008 12:20 PM

Finding an existing design is the best choice but it's not going to be easy to find a design with those drivers together but you can get lucky. It's either a MTM or a TMM 2.5 way I imagine.

Have a look at Jay's site as some of his crossover designs could give you some clues and be a great starting point. He has a great article on designing a crossover using software only and would get you much closer than textbook formulae.

http://www.geocities.com/woove99/Spkrbldg/

Nanook 19th May 2008 12:46 PM

the art in loudspeakers...
 
is truly crossover design and implementation.

Crossovers can be quite difficult and are more than just a sum of parts or good simulations. One solution, suggested by Dave Bullet(#3 on his list) suggests finding some designs which use your particular drivers. Not an ideal approach, but maybe one worth investigating. An already suggested site, Jay's speaker projects , has a project using these drivers (simulations only, but it appears to be thorough) also see elsewhere on his site regarding tuning crossovers.

Commercial designs often go through several incarnations of the crossover to get it "right" based on the designer's tastes, biases and voicing requirements.

Another approach could be the use of a good electronic crossover and multi-amping. That way a great number of crossover orders and frequencies can be tried, until one that you enjoy can be found that works with your drivers. Then implement it using passive components (if that's what you want) or keep the setup multi-amped.

Just curious, does Peerless use these drivers (together) in any of their designs ?

stew

sreten 19th May 2008 01:33 PM

http://www.rjbaudio.com/Audiofiles/FRDtools.html
http://www.geocities.com/woove99/Spkrbldg/

http://www.diyaudio.com/forums/showt...361&highlight=

http://www.geocities.com/woove99/Spk...ss_HDS_TMM.gif

:)/sreten.

hybridfiat 19th May 2008 01:58 PM

Thanks
 
Ive learnt a lot and you are right Jay had the crossover already designed for these drivers.
Next will be some research and experimentation with enclosures.
Volume and porting can be altered as MDF is cheap and Ive lots of toys I mean tools to shape up just what is needed.
Ill keep looking and asking till Im happy with the theory then start:smash: working.

Dave Bullet 19th May 2008 07:55 PM

Hybridfiat,

Well - there you go! Sometimes you get lucky and sreten and Jay have come up with the goods.

Happy building and let us know how you go.

PS: You do realise Jay's design is a 2.5 way - not a classic 2 way MTM. Typically 2.5 ways are laid out in a TMM arrangement.

Thanks,
David.


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