Fostex FX120 where did I go wrong?

[ODougbo]

Do you have any paint by numbers schematic diagrams? Chuckle.

An on line calculator, now that’s perfect for me, where would be a good place to start? 6 db reduction? (for the quickie mock up cabinets shown).

I am going to build the T-line speakers (-; (-;

15” woofers, yeah maybe someday. I have 12”s 10”s and 8”s laying around, in and out of boxes, I tend to go for the 8”s, (isobaric). I tend to crank out boxes in the winter season, not much else to do………

if I had two pairs of FX120 my project of choice would be that MLTL, expanded for two drivers per side, with the bottom driver rolled off at baffle step to make a 1.5 way.

With just one pair, my project of choice would be an OB with a 15" woofer. 😎

BTW here's an online calculator for BSC: Loudspeaker Diffraction Loss and Baffle Step Compensation Circuits

 

[ODougbo]

Dave,

I see a lot of folks are light years ahead of me on a lot of this, wish I found this site about 10 years ago!! The circuit is very simple, and now I have on-line calculator.

The schema in the article is as basic as it gets. I would consider the Zobel optional and leave it out unless the LR addition ended up affecting the top end as well

dave

 

[Chaz H]

An on line calculator, now that’s perfect for me, where would be a good place to start? 6 db reduction? (for the quickie mock up cabinets shown).

most people tend to start around 3 db; room gain usually makes up for the rest.

So again (sorry) am I missing something, I have FX 120s?

Yes, as in plural FX120. 🙂

 

[ODougbo]

Just for the record.

Woops, turns out there was nothing with the speakers or amplifier :-/ The DIP switches needed adjusted; the bass filter(s) were set to cut off at 70hz.

They actually have really nice strong bass. I did use a 5.6 air coil for the back driver, with a zobel circuit. I also added lead lining to the upper chamber, to smooth out the middle response.

Chazdrumzalot, thanks for the advise, the double box system is sounding pretty good and they are only the mock up cabinets. The tall needle cabinets will be ready next week.

 

[ODougbo]

’m hoping these sound as good as the proto type boxes (which have rich, generous bass). Unsure what’s going on? There are a total of 8 chambers. They are 55.5” tall 7.5”wide.

 

[chris661]

The schema in the article is as basic as it gets. I would consider the Zobel optional and leave it out unless the LR addition ended up affecting the top end as well

dave

Dave,

Having tried to get a notch filter to work on my Fostexes, I found that, despite the additional capacitor over a BSC, the transfer function gave an almost perfect shelf (same voltage output at 7,10,20kHz, notch set for ~7kHz). A BSC would, I suspect, taper off the high frequency response, so a Zobel would be required to avoid this.

Chris