Passive 2.5-way crossover design...

[chops]

Hi all, it's been a while but I'm going to be building a pair of loudspeakers soon. Unfortunately, I don't have the time to go into detail (have to go back to work in a few minutes), but are they any major differences or things I should look for when designing a 2.5-way crossover over a normal 2-way design?

I could be running up to 5 identical mid-woofers, 1 or 2 of which would run all the way up to the tweeter crossover point. So I could have between 3 and 4 drivers just playing only the bass frequencies.

Also, is there any decent "free" software that I can download just to play around with and get some ideas on for crossover designs?

When I get off of work tonight, I'll go into more detail of the desired project ahead.

Thanks in advance!
-Charles

[sreten]

http://www.rjbaudio.com/Audiofiles/FRDtools.html, /sreten.

[chops]

Wow, only one post on this, huh?


Anyway...

What I plan on doing is building a pair of taller than average, narrow, fullrange towers. The tweeters will be roughly 40" from the floor, and one of the 5 mid-woofers will be placed above the tweeter. It will be a vented design with a wood, rectangular port.

For drivers, I'm looking at Usher, Morel and Vifa in 6", 7" and 8" versions. The tweeters will be soft domes. The mid-woofers need to be able to reach down to around 35 - 40Hz with a matching FS if not slightly lower, and extend up to at least 4kHz, but the higher, the better. The tweeters will need to extend as low as possible, at around 1.2 - 1.5kHz.

I will want the crossover to be as simple as possible, -12dB for the upper mid-woofer and tweeter, and -6dB for the lower mid-woofers. The crossover points I'm not too sure of yet, but I'm looking at 150 - 200Hz for the lower drivers and somewhere around 2.5 - 3.5kHz for the top end.

The front baffle will be stepped for the tweeter to be time aligned to the mid-woofers. The entire enclosure will be built with 1" MDF, 2" for the baffle, and plenty of 1" MDF braces that connect all four sides throughout the entire length of the tower. The top and sides of the tower will be covered in a nice 0.75" hardwood with rounded edges. When looking at the enclosures from the sides, the stepped parts of the baffle will extend out an inch from the hardwood. There will also be a nice, healthy wood base on the bottom to help stabilize the tower. The crossover will probably be located here as well as be filled with sand.

That's basically it. Any thought, suggestions or ideas?

[tinitus]

One point, .. not many standard drivers above 5" will sound good with high xo point ... you mentioned 3.5khz
That they LOOK good on measurements, doesnt mean that they also SOUND good

[chops]

That all depends on what driver is used.

[tinitus]

Looking at JoeRasmussens 2.5way "Elsinore" using the Vifa 6.5" HDS Nomex it appears that a total of 4 drivers is well chosen - as is the waveguide on tweeter

If you want to use 4 drivers fore bass and 2 "midbass", you might get in trouble with lack of midrange sensitivity, and the result might be boomy bass - remember that in a 2.5way ALL drivers play bass - but ofcourse it also depends on the drivers

About the xo, I think that its more interesting to run the bass and midrange inductors in series - like Zaph does it on his "waveguide" 2.5way

[justblair]

I dont know much about crossovers, but I recently mapped out the XO in my mission 753's which sound similar to what you are doing.



I suspect that this is not an ideal design, as the larger values for the mid and bass XO caps mean you get kinda tied to lytics for these.

[sreten]

Originally posted by chops
Hi all, it's been a while but I'm going to be building a pair of loudspeakers soon. Unfortunately, I don't have the time to go into detail (have to go back to work in a few minutes), but are they any major differences or things I should look for when designing a 2.5-way crossover over a normal 2-way design?

I could be running up to 5 identical mid-woofers, 1 or 2 of which would run all the way up to the tweeter crossover point. So I could have between 3 and 4 drivers just playing only the bass frequencies.

Also, is there any decent "free" software that I can download just to play around with and get some ideas on for crossover designs?

When I get off of work tonight, I'll go into more detail of the desired project ahead.

Thanks in advance!
-Charles

Originally posted by chops
Wow, only one post on this, huh?


Anyway...

What I plan on doing is building a pair of taller than average, narrow, fullrange towers. The tweeters will be roughly 40" from the floor, and one of the 5 mid-woofers will be placed above the tweeter. It will be a vented design with a wood, rectangular port.

For drivers, I'm looking at Usher, Morel and Vifa in 6", 7" and 8" versions. The tweeters will be soft domes. The mid-woofers need to be able to reach down to around 35 - 40Hz with a matching FS if not slightly lower, and extend up to at least 4kHz, but the higher, the better. The tweeters will need to extend as low as possible, at around 1.2 - 1.5kHz.

I will want the crossover to be as simple as possible, -12dB for the upper mid-woofer and tweeter, and -6dB for the lower mid-woofers. The crossover points I'm not too sure of yet, but I'm looking at 150 - 200Hz for the lower drivers and somewhere around 2.5 - 3.5kHz for the top end.

The front baffle will be stepped for the tweeter to be time aligned to the mid-woofers. The entire enclosure will be built with 1" MDF, 2" for the baffle, and plenty of 1" MDF braces that connect all four sides throughout the entire length of the tower. The top and sides of the tower will be covered in a nice 0.75" hardwood with rounded edges. When looking at the enclosures from the sides, the stepped parts of the baffle will extend out an inch from the hardwood. There will also be a nice, healthy wood base on the bottom to help stabilize the tower. The crossover will probably be located here as well as be filled with sand.

That's basically it. Any thought, suggestions or ideas?

Hi,

Both of the above posts seem to imply you do not really understand
the purpose of the 0.5 in a 2.5 way, which is to give 6dB of full BSC,
(baffle step compensation).

The BSC midpoint determines the bass 0.5 way c/o frequency.

For this to work with identical drivers the number of bass only and
bass/mid drivers would need to be equal, 1 and 1, or, 2 and 2 (MTM).

However full BSC can sound bass heavy depending on the drivers.

TBH a 3-way is probably a better choice with that amount of drivers.

Electrical c/o slopes are not the same as acoustic c/o slopes.

http://www.rjbaudio.com/Audiofiles/FRDtools.html

/sreten.