fr125s and sdx7 2-way project

[squidlydeadly]

Hi,

I have been using fr125s in small boxes (tried vented, sealed and Aperiodic boxes) and really like the general sound of them specially for near field monitoring and small rooms.
However, I find that they get overworked and lose some clarity when playing heavier and more complex music.

So the plan is to build a 2-way tower using the sdx7 and fr125sr crossed at around 350-400hz with the hope of getting better bass and alleviate some stress of the fr125s.
I played around with winISd and right now am looking at a 7litres sealed chamber for the fr125sr and a vented 30 litres chamber tuned to 30hz for the sdx7.

This is my first XO and I suck at soldering ( I do know which tip is the hot one on my soldering iron but that's about it ) so I was hoping to keep it simple and go with a 1st order butterworth XO as both drivers are able to go above and below the crossover point. At least that's what my basic understanding suggests...

The values I got from 2-Way Crossover Designer / Calculator
are C1 = 64.9 uF and L1 = 2.91 mH

Any ideas on how to improve this while keeping it simple? Any obvious wrench in the plan or obvious newbie mistakes?

Thanks!

E.

[planet10]

Here is a good backgrounder CSS 3 way bookshelf speakers

Sam's XO is 1st order at ~350 ... you can just use his proven values of 68 uF & 3.76 mH. I'd strongly suggest a poly cap. Personally i'd XO lower (and likely biamped)

I've played quite a bit with SDX7, and i really like them sealed. This also avoids the abrupt hitting of the stops that the FE125 also has when pushed to the limits. I had to make my TLs aperiodic (port almost stuffed enuff to be sealed) to deal with this. 14-21 litre is optimum. I usully go 14-17 litre with damping pushing the aparent volume close to the max.

Also, do consider the minimal treatment on the SDX7, it helps a lot.

dave

[squidlydeadly]

Hi Dave,

Thanks for the input! I'll see if I can steal some modpodge from my wife and work up the nerve to coat brand new drivers :-)

I quickly read Sam XT's thread but hadn't realised that his XO had similar values to what I was planning since it was for a 3-way design (shows how little I know). Thanks for the heads up, I'll stick to his numbers.

BTW, How accurate should the values for the caps and inductors be? I am not sure if there is a % of error as I can't get the exact value with one cap (from solen.ca) and was hoping to avoid multiple caps in parallel and inductors in series (if thats the way of it)... any tricks or tips to help with that?

Thanks,

E.

[planet10]

In a situation like this probably 5% is fine... you could also try the same values in a series configuration.

With the mod podge just make sure you have the cone tipped such that when you are 1st applying any runs will travel away from the phase plug/vpoce coil gap.

dave

[consort_ee_um]

I found that the air leakage past the phase plug compromised the design of the enclosure for the FR125S. Having said that it gave good results in a 4.5l ported cabinet. Try modelling it with a Ql (leakage factor of 1 or 2)
I partnered it with a tweeter since for me it had 'cone cry' probably the break-up mode at 6.5K. The effect lessened with running in but was still there. I haven't tried Planet10's treatment though.

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