Hello everyone.
First let me say that I've never built a speaker before. I've been thinking about building a couple cabinets for Fostex FX120 drivers. I've done a lot of searching and reading (on this forum and many other places) over the last few months and I've learned a lot but I still have some questions I can't quite find clear answers about.
Due to space issues, I had to give up my large vintage speakers and I've been stuck using headphones for a while. The only place I have for an audio setup now is my computer desk in a small (120 square foot) room. With my research I've become really interested in single driver speakers, and the FX120 became my top choice because of its apparently smooth response, decent bass capability, and the fact that it seems fairly easy to work with in a small bass reflex enclosure that will fit on my desk.
I've been playing around with various enclosure sizes and port tuning in WinISD, but this is where I'm still unsure about things. Fostex' recommended enclosure for the FX120 seems to be the same as the FE127E. They call it 10 liters tuned at 71Hz, but the numbers show it to be more like 9.3 liters tuned at 73Hz. With the FX120, this leads to a slight rise in the lower midrange and a peak of about +1.5dB at 90-100Hz, followed by a fairly sharp rolloff below that. I worry that this would leave to a boomy, one-note bass especially near/against a wall in my slow room.
Plugging in something more like 10 liters tuned at 58Hz gives a very smooth rolloff starting slowly at 200Hz but extending to 63Hz at -3 and and 51Hz at -6. This seems like it would give a more natural, controlled bass response in my setup.
However, I do have some doubts about that design. I'd really like to have as much bass presence as possible without it becoming boomy. I'd also like to avoid the use of an EQ or baffle step compensation if possible to keep things simple. Maybe the Fostex design with an increase in the lower midrange would actually be better for this?
I couldn't find much information about ideal bass reflex enclosure specs for the FX120, so I'd really appreciate any advice for what might be my first DIY speaker project.
First let me say that I've never built a speaker before. I've been thinking about building a couple cabinets for Fostex FX120 drivers. I've done a lot of searching and reading (on this forum and many other places) over the last few months and I've learned a lot but I still have some questions I can't quite find clear answers about.
Due to space issues, I had to give up my large vintage speakers and I've been stuck using headphones for a while. The only place I have for an audio setup now is my computer desk in a small (120 square foot) room. With my research I've become really interested in single driver speakers, and the FX120 became my top choice because of its apparently smooth response, decent bass capability, and the fact that it seems fairly easy to work with in a small bass reflex enclosure that will fit on my desk.
I've been playing around with various enclosure sizes and port tuning in WinISD, but this is where I'm still unsure about things. Fostex' recommended enclosure for the FX120 seems to be the same as the FE127E. They call it 10 liters tuned at 71Hz, but the numbers show it to be more like 9.3 liters tuned at 73Hz. With the FX120, this leads to a slight rise in the lower midrange and a peak of about +1.5dB at 90-100Hz, followed by a fairly sharp rolloff below that. I worry that this would leave to a boomy, one-note bass especially near/against a wall in my slow room.
Plugging in something more like 10 liters tuned at 58Hz gives a very smooth rolloff starting slowly at 200Hz but extending to 63Hz at -3 and and 51Hz at -6. This seems like it would give a more natural, controlled bass response in my setup.
However, I do have some doubts about that design. I'd really like to have as much bass presence as possible without it becoming boomy. I'd also like to avoid the use of an EQ or baffle step compensation if possible to keep things simple. Maybe the Fostex design with an increase in the lower midrange would actually be better for this?
I couldn't find much information about ideal bass reflex enclosure specs for the FX120, so I'd really appreciate any advice for what might be my first DIY speaker project.
9-10 litres is as small as i was willing to go with FX120. I have a Fonken this size. Plans (dFonkenFX) are on frugal-phile.com
Frugal-phile | Box Library / Fostex
dave
Frugal-phile | Box Library / Fostex
dave
10-12L tuned between 50Hz-55Hz looks like something I'd use on a desktop. Keep some provision to alter the tuning if possible. Don't forget to take into account any significant impedance, say from a single-ended tube amp, in the drive circuit.
You're forgetting the baffle step, which will rob you of about 3-4db in the midbass and low mids.
I wouldn't get hung up on max flat computer sims. Your room will screw things up by way more than 1.5 db.
The smaller Fostex BR designs are often tuned a little warm to compensate both for baffle losses and the small size of the driver. I had the old FX200 in their factory BR and they were very smooth and musical. They were cleaner and more lifelike in big pipes, but their flaws (mostly a peak at ~4k) were more on display too. A small BR somehow chilled them out.
I wouldn't get hung up on max flat computer sims. Your room will screw things up by way more than 1.5 db.
The smaller Fostex BR designs are often tuned a little warm to compensate both for baffle losses and the small size of the driver. I had the old FX200 in their factory BR and they were very smooth and musical. They were cleaner and more lifelike in big pipes, but their flaws (mostly a peak at ~4k) were more on display too. A small BR somehow chilled them out.
Many years ago I built a pair of mini-Onkens loosely based on Dave's original Fonken for the FE127E. They turned out to be pretty decent, but the 127's were just a bit too forward around the 6-7kHz range. With a bit of routering, I managed to shoe-horn a pair of FX120's into these boxes, and the result was impressive. This box is a little on the big side at ~14.5 Litres, with a bit of a hump at around 70Hz. If I were to build another pair, I'd probably go a bit smaller, say around 12 Litres. Either way they'd be better than the Fostex boxes.😀
BTW, the drivers were EnABle'd by Dave, which takes them to a whole notha level sonically, and they look very pretty too.
jeff
Attachments
Those look absolutely fantastic. Do you use any BSC with them or do you find that they sound balanced enough without it?
Never thought they needed it, but I've never had anything other than tube power amps in my main system with these speakers. With solid state amps, a little bit of BSC might be required. I've run them with a small powered sub thou, as they need a bit of help down low. Quite a good combo, even with the cheap sub.
jeff
Enabling with pre-treatment should have killed that 6-7kHz rise and in any case with the power of todays EQ's in computers any peak is no longer a (big) problem. Having said this I will do the trifoil and modge podge pre-treatment on three FE127E that I recently managed to obtain.
Treatment will ameriolat ethe problem but not completely eliminate it. EQ is a band-aid, it doesnotget rid of the resonance, just tries to hide it. I bever had an issue with the FE127 resonance once drivers were treated(i currently have mFonken in the office), but Jeff's wife did. FX120 is smoother.
dave
DSP EQ is a pretty good band-aid, though. One must be careful about over-doing it. Digital EQ does generate THD and phase distortion. The phase distortion become audible when more that ~6dB of correction is made, earlier if you are particularly sensitive to phase. Also, once you EQ to dead flat above 500Hz or so, you will remove the character of your system. Good/bad? Your call. I use DSP exclusively now, including XO's for FAST. Never looked back.
Bob
Bob
Yeah, she really didn't like them. I quite liked the mFonken+FE127 combo on the desktop, a little "light" in the bass IIRC.
They are real nice on my desktop, and "just" fit. Thanks to the OP, as I may never have tried them here.
jeff
They are real nice on my desktop, and "just" fit. Thanks to the OP, as I may never have tried them here.
You're welcome. It's nice to hear that they work well there.
The Fonken cabinets look amazing, although I doubt I could build one without a kit. If I decide to go ahead with a DIY project I'll probably start with a basic box.
As for EQing, most of my listening will be from a computer, so I imagine it would be fairly simple to do a little adjustment with software. It just wouldn't help for the bit of FM radio listening I do.
Thanks to everyone for the advice.
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