New Project - Dayton RS180 and Vifa XT25

[DrDyna]

Hey fellas. This morning I've decided that I want to try an inexpensive build using the Dayton RS180 7" woofer and the Vifa XT25 that I've grown to like quite well.

I've attached what I've come up with so far on the crossover, but bear in mind I'm not used to making proper crossovers yet, so any comments or fun-picking are more than welcome.

What do you think?

[DrDyna]

Anyone see any glaring errors? Is that phase shift a concern? Is there any easy way to get rid of it?

[jerome69]

We are in a week-end time...

I think you should make a steeper slope for the RS180 to suppress the resonance peaks. Hard cone are hard to work, the result could be superb.

See a similar projects :
RS180-RS28 MTM
HTGuide Forum - RS180 Modula MT - you asked for it, you got it!

[DrDyna]

Originally Posted by jerome69

We are in a week-end time...

I think you should make a steeper slope for the RS180 to suppress the resonance peaks. Hard cone are hard to work, the result could be superb.

See a similar projects :
RS180-RS28 MTM
HTGuide Forum - RS180 Modula MT - you asked for it, you got it!

Hey Jerome

I think I might try a little steeper. One of the things I was concerned with was the peaks. I wasn't sure if they'd be down far enough like this or if I should go steeper.

Steeper it is! One question though, if I make that slope steeper, maybe I should move the crossover point up a little bit? I suspect that the XT25 might be better off a little higher as well.

I'll tinker with it a little bit and post another one later today before I order parts tomorrow or Monday.

[5th element]

It isn't the peaks as per say that need to be so far down. The issue is the peaks created in the distortion profile. Lets say a peak occurs at 9khz in the frequency response. If the driver produces a 3khz tone, then it will naturally create 6khz and 9khz etc as the 2nd and 3rd order distortion products. In this case as the cone rings at 9khz, the 3rd order product will be amplified by the cone and thus you get a peak in the third order distortion product at 3khz. Hence cross before it.

You can see this in action on Zaph's website with his measurements of metal cone drivers. The RS180 wants a steep, low xover. The XT25 doesn't want low, but it can do 2khz with a 4th order slope.

[DrDyna]

Originally Posted by 5th element

It isn't the peaks as per say that need to be so far down. The issue is the peaks created in the distortion profile. Lets say a peak occurs at 9khz in the frequency response. If the driver produces a 3khz tone, then it will naturally create 6khz and 9khz etc as the 2nd and 3rd order distortion products. In this case as the cone rings at 9khz, the 3rd order product will be amplified by the cone and thus you get a peak in the third order distortion product at 3khz. Hence cross before it.

You can see this in action on Zaph's website with his measurements of metal cone drivers. The RS180 wants a steep, low xover. The XT25 doesn't want low, but it can do 2khz with a 4th order slope.

Aha, makes sense. Commence more fiddling! lol.

Edit: I haven't ordered the drivers yet, is there a tweeter that you guys know of that might be a better mate..maybe a little lower where I could simplify the network a little? Maybe I should look at what Zaph used in his :S

Edit2: Meh, the RS28 tweeter is a little too much money.

[5th element]

The RS28 was only one choice that JonMarsh used. He also did a version with the SEAS 27TDFC.

For doing low crossovers on a 'budget' you don't get much better then the chambered 27 series from SEAS.

[jerome69]

Yes 70$ a RS28 is little expensive.

You have some choices :
Soft domes
Dayton Audio DC28F-8
SEAS 27TDFC
Scan speak or ViFA DX25
Vifa NE25VTS
etc.

Hard domes
SEAS 27TBCG
Vifa NE25VTA
etc.

[DrDyna]

Originally Posted by jerome69

Yes 70$ a RS28 is little expensive.

You have some choices :
Soft domes
Dayton Audio DC28F-8

Hm, that DC28F looks decent, and cheap as hell too, with good reviews.

[5th element]

I'd rather use the Vifa DQ25 over the DC28F. Or rather I've used the DQ25 with the RS125 with great results.

The DQ wont go down low as comfortably as a SEAS 27TDFC will. As Jerome says the vifa DX25 is rather good for the money too.

The crossover is very important however as any tweeter will be working close to it's operating limits. In this regard the DX25 has the most extended low end response and could well make designing the crossover a little bit easier. Whatever tweeter you use you want to use 4th order acoustic slopes no higher then 2khz as this will provide reasonable attenuation for the 3rd order distortion peak in the RS180.

If you've extrapolated the phase response decently then flipping the polarity on any even order network will show a symmetrical notch at the xover frequency if the drivers are well integrated with respect to phase.