First OB build, with 2x15" + FR.

[mige0]

Despite that an IPhone would not be my first recommendation as for a reliable measurement device - why exactly do you want to down shift upper frequency slope of the woofer?

Michael

 

[oLjud]

I want to lower the upper frequencies to minimize H-frame quarterwave.

That measurement was done 1m from the woofers, I also measured from 1.5m. Got a 3dB rise between 170-250Hz... So if I lower the crossover point I may get rid of the rising.

But I gonna do a measurement on the FR when its done and see how it plays.


PS, the iPhone are not perfect but it's actually great. Have used CLIO and iPhone to see any difference on my first pair of speakers, the graphs where very much alike! So I trust the iPhone to give a good enough graph for this purpose.

 

[jerome69]

I'm using 2nd order filter for both woofer and FR. Just took a relook at the measurement, the woofers starts to fall at 250 and have lost 3dB at 300Hz(?)

FR: 22uF / 3.9mH (+ L-pad circuit ~2.5dB)
Woofer: 4.7mH / 150uF

According to MJK the crossover for the woofers in an H-frame would have 125Hz crosspoint. which would mean that I must double up the coil size, right?

sorry for the bad measurement, done with my half broken iPhone 3G

I am not understand very well because I suppose you have made the H-FRAME in the MJK paper with the same dimension but taller ?
I understand in this paper, the response of the H Frame is obtained with an electrical crossover LR2 - 125Hz. It gets a flat response with a crossover frequency near 350Hz -6dB. Acoustically it's a LR4 slope.
This means electrically LR2 125Hz for 4ohms speaker L=10mH C=160uF~150uF
Yes you are far from the good value for the inductance.
I think you need the MJK worksheet or good measurements to make the precise calculations because the online calculator doesn't take into account the actual impedance and the actual response.

Second reason to cut the frequency of the 15" as high as possible is distortion
:
Distortion of my open baffle, the distortion is higher because the 5' does higher above 500Hz. Crossover frequency is 500Hz.

An externally hosted image should be here but it was not working when we last tested it.

Hope this Helps.

 

[oLjud]

Yes I done the H-frame according to MJK worksheet, but the double height.
(40x40x80cm inner size).

I missed what crossover he recommended for H-frame when I read the document, so I just made an 4ohm version of his Dipole crossover. But, I later read the H/U-frame document again saw that he recommended 125Hz instead when building H-frame.

I'll may order a pair of coils later next week!

Very grateful of all help and advices!!

 

[oLjud]

I ones again plugged in the speakers, the woofers are much more transient the before, I guess the break in work well for them.
But for the Fostex drivers, they opened up in the middle region, voices sound awesome, but the highest notes are still sharp/edgy/intense... I'll hope it goes away are a few more play hours.

Otherwise I haven't time to measure anything yet, the quick listening today were great. The FR-baffle doesn't have as much vibrations as before, now it feels like the entire frame are moving instead of only the baffle.

I'll update with more info soon, study for a test on saturday at the moment....

 

[oLjud]

Well the sharpness/intense high notes were gone when I played from my MacBook instead of iPhone. So not it sounds pretty sweet 🙂

the quarterwave resonance is hearable now, but I'll hope the new coils will help with that.

Nils Lofgrens - Keith Don't Go solo part are just incredible, such controlled sound! 😀