This design is the result of three prototypes and over 10 months of listening/adjustment work. 
It is a folded ML-TQWT designed using MJK's excellent worksheets.
I wanted an enclosure that would bring the FX-120 driver to a true fullrange speaker, i.e having a convincing bass extension without sacrificing the outstanding refinement of the FX-120 driver.
Everything has been done to keep the frequency response flat, and to avoid port noises pollution.
Damping and port position have been optimized for a minimal midrange output through the port, keeping the driver the only sound source above 200Hz.
The port has been flared and its length corrected within 1/100mm precision to avoid chuffing issues.
The cabinet is made out of 19 and 22mm MDF and has been built by a carpenter on a CNC machine.
Every angle on the front has been flared to avoid edge resonnances.
When I plugged them for the first time, without any damping, I was struck by the bass reproduction.
It was clean and surprinzingly tight for such a small driver ! I experimented further with damping and got an even cleaner bass.
As I wanted it, the port is totally silent above 200Hz.
Everything that comes out from the driver is crystal clear, very well defined and detailed.
Coherence is a strong advantage with this enclosure, and imaging is ultra-precise.
I rediscovered my musics !
Now a few specifications :
BW : 47Hz - 20kHz -3dB
SPL max = 100dB 10W/1m (downside of the very large cabinet)
THD+N = 0.15% 3W/1.5m (including amp, soundcard, microphone etc...)
cost : 260€/pair max
I decently think it is one of the best designs possible for those drivers
Enjoy
It is a folded ML-TQWT designed using MJK's excellent worksheets.
I wanted an enclosure that would bring the FX-120 driver to a true fullrange speaker, i.e having a convincing bass extension without sacrificing the outstanding refinement of the FX-120 driver.
Everything has been done to keep the frequency response flat, and to avoid port noises pollution.
Damping and port position have been optimized for a minimal midrange output through the port, keeping the driver the only sound source above 200Hz.
The port has been flared and its length corrected within 1/100mm precision to avoid chuffing issues.
The cabinet is made out of 19 and 22mm MDF and has been built by a carpenter on a CNC machine.
Every angle on the front has been flared to avoid edge resonnances.
When I plugged them for the first time, without any damping, I was struck by the bass reproduction.
It was clean and surprinzingly tight for such a small driver ! I experimented further with damping and got an even cleaner bass.
As I wanted it, the port is totally silent above 200Hz.
Everything that comes out from the driver is crystal clear, very well defined and detailed.
Coherence is a strong advantage with this enclosure, and imaging is ultra-precise.
I rediscovered my musics !
Now a few specifications :
BW : 47Hz - 20kHz -3dB
SPL max = 100dB 10W/1m (downside of the very large cabinet)
THD+N = 0.15% 3W/1.5m (including amp, soundcard, microphone etc...)
cost : 260€/pair max
I decently think it is one of the best designs possible for those drivers
Enjoy
Attachments
And finally, the plans. Note that the port dimensions are given for an unflared port !
With a 9.6mm flare radius, the length must be increased to 32mm.
WARNING : this plan is only intended for DIY purposes ! Any other use, including commercial use and profit making is strictly forbidden !
With a 9.6mm flare radius, the length must be increased to 32mm.
WARNING : this plan is only intended for DIY purposes ! Any other use, including commercial use and profit making is strictly forbidden !
Attachments
Had time to measure the port response and the port impulse response.
The microphone was placed right at the output of the port, aligned with the front plate. I hope it doesn't modify the port response too much because we can see a peak at 1kHz. It could also be the signal coming from the driver itself, as it is not that far from the port.
The microphone was placed right at the output of the port, aligned with the front plate. I hope it doesn't modify the port response too much because we can see a peak at 1kHz. It could also be the signal coming from the driver itself, as it is not that far from the port.
Attachments
... and the pulse response. I find it to behave quite well for a ported design. The main pulse is damped in 4ms, far better than my home theater JBL subwoofer !
I did measurements of the frequency response but lost all the data due to a battery failure of my laptop
It showed a ruler flat response from 800Hz to 50Hz, but seemed to have a "bump" of +3dB between 1kHz and 2.5kHz that rather comes from the driver (it did the same in my previous enclosures)
Now I have the speakers in my little listening room, I will remeasure them but it will be likely to look awful
I did measurements of the frequency response but lost all the data due to a battery failure of my laptop
It showed a ruler flat response from 800Hz to 50Hz, but seemed to have a "bump" of +3dB between 1kHz and 2.5kHz that rather comes from the driver (it did the same in my previous enclosures)
Now I have the speakers in my little listening room, I will remeasure them but it will be likely to look awful
Attachments
Finally, I were able to take a far field frequency response graph :
the measurement was made in the middle of my bedroom, at 1m of the speakers.
My room is 4.3m*3.8m, and it is not acoustically treated.
As I assumed, it needs some BSC if used in a big room. a cap+8ohms in parallel with the driver should do the trick.
Probably due to the room, bass surprizingly extends down to 43Hz.
Any comment, suggestions ?
the measurement was made in the middle of my bedroom, at 1m of the speakers.
My room is 4.3m*3.8m, and it is not acoustically treated.
An externally hosted image should be here but it was not working when we last tested it.
As I assumed, it needs some BSC if used in a big room. a cap+8ohms in parallel with the driver should do the trick.
Probably due to the room, bass surprizingly extends down to 43Hz.
Any comment, suggestions ?
Attachments
Hmm, not bad at all, especially in the middle of a fairly normal room. One suggestion -what speaker wire and amp are you running? Part of the slump below 1Khz is Baffle-Step loss, but if you're running solid state amplification a quick tip would be to go for a very thin gague wire. I use 24AWG magnet wire with my FF165Ks and it works very well -basically, it's adding some series resistance. You can get the same effect by adding a resistor in parallel, but this is the easier way! Cheapest way is to buy a single piece of Cat5, then extract 2 of the twisted pairs from it, and use one pair each side as the cable. That's 24AWG and will do the job. Interesting effect that's worth experimenting with if you haven't already as it's very cheap to achieve and invariably lifts the bass performance.
Best
Scott
Best
Scott
I'm running a LM4780 bridged amp with enhanced PSU, and I use 2 pairs phone cable for each pole.
Thanks for the cable suggestion !
I have the best way to compensate the baffle loss without compromising the damping factor, which I found to be very important for the sound : as I use my computer as source, I adjust the equalizer in Foobar2000.
It has moreover the advantage of precisely compensating the room's resonnances after measurement (this measurement was not taken in the listening position to be more objective).
But, if the speakers are in corners, or on a wall, you won't be likely to need any baffle step compensation : I don't apply any in my case. Just room correction.
Thanks for the cable suggestion !
I have the best way to compensate the baffle loss without compromising the damping factor, which I found to be very important for the sound : as I use my computer as source, I adjust the equalizer in Foobar2000.
It has moreover the advantage of precisely compensating the room's resonnances after measurement (this measurement was not taken in the listening position to be more objective).
But, if the speakers are in corners, or on a wall, you won't be likely to need any baffle step compensation : I don't apply any in my case. Just room correction.
Greets!
Interesting! Your design is very similar to my old pre-T/S rule-of-thumb style ML-horns. Good work, thanks for sharing!
FWIW, my take on the FX120 using just its Sd and Fs*0.707 (all dims i.d.):
L = ~91.75"
SO = ~0"
SL = ~103.57"^2
zdriver = ~0.6809 (~29.27" up from bottom)
Rear firing slot vent = Sd (12.946"^2)
A wad of acoustic fiberglass in the point and a little around the driver area.
Coupled up to a typical SET amp with several ohms of output impedance, there should be no need for any BSC.
GM
Interesting! Your design is very similar to my old pre-T/S rule-of-thumb style ML-horns. Good work, thanks for sharing!
FWIW, my take on the FX120 using just its Sd and Fs*0.707 (all dims i.d.):
L = ~91.75"
SO = ~0"
SL = ~103.57"^2
zdriver = ~0.6809 (~29.27" up from bottom)
Rear firing slot vent = Sd (12.946"^2)
A wad of acoustic fiberglass in the point and a little around the driver area.
Coupled up to a typical SET amp with several ohms of output impedance, there should be no need for any BSC.
GM
Attachments
As I'm not a fan of high impedance amps (that makes speaker sound boomy), I prefer to use either the computer's equalizer or a shelved lowpass buffer. Not a fan of passive notch filters : they reduce the damping factor in the midrange.
I'm not a fan of rear-firing vents either : it causes problems with the rear wall, adds group delay and makes the sound less natural. I once built a speaker with rear firing port, and modified the enclosure to put the port on the front. Got too much problem for 1 or 2dB of room gain IMHO.
I designed this speaker almost two years ago, and if I had some new FX120 drivers to use, I would probably put them in sealed or open baffle, then cross to a sealed subwoofer. More SPL, less distorsion and cleaner sound.
These speakers are still my main speakers, but not for long : I've got a 3-way system on the go with 15" drivers, and the FX120 will probably be used as surrounds.
I'm not a fan of rear-firing vents either : it causes problems with the rear wall, adds group delay and makes the sound less natural. I once built a speaker with rear firing port, and modified the enclosure to put the port on the front. Got too much problem for 1 or 2dB of room gain IMHO.
I designed this speaker almost two years ago, and if I had some new FX120 drivers to use, I would probably put them in sealed or open baffle, then cross to a sealed subwoofer. More SPL, less distorsion and cleaner sound.
These speakers are still my main speakers, but not for long : I've got a 3-way system on the go with 15" drivers, and the FX120 will probably be used as surrounds.
I wouldn't write it off. You might not know this, but GM's been in this game for a while... and bluntly, he's one of the finest speaker designers in the DIY community (and streets ahead of 99% of the commercial brigade too IMO). If he says it'll work, then it will. Period. Different type of presentation to your boxes (and certainly better damped around Fc), but I suppose we can call this a matter of taste.
I noticed you were shifting to a multiway setup elsewhere -you might want to look at Karlsons at some point.
I noticed you were shifting to a multiway setup elsewhere -you might want to look at Karlsons at some point.
OK, didn't know this so far. Didn't want to offense anyone lol.
I was just communicating my own experience, which may be different. I'm rather oriented towards solid state amps, active Xo, electronic equalization, but it is only a point of view.
I assume when you say "better damped" that you talk about the 55Hz peak. Well, that's true, I've put little damping inside to give the impression of more bass in the 50Hz region. I find this tiring right now, and maybe one day it will be corrected.
Also, there is still too little damping around the driver, the CSD could be cleaner I think.
What do you mean when taliking about Karlson's ? Has he got a similar system somewhere ?
I was just communicating my own experience, which may be different. I'm rather oriented towards solid state amps, active Xo, electronic equalization, but it is only a point of view.
I assume when you say "better damped" that you talk about the 55Hz peak. Well, that's true, I've put little damping inside to give the impression of more bass in the 50Hz region. I find this tiring right now, and maybe one day it will be corrected.
Also, there is still too little damping around the driver, the CSD could be cleaner I think.
What do you mean when taliking about Karlson's ? Has he got a similar system somewhere ?
It's the Karlson coupler I'm talking about rather than a person. See http://home.planet.nl/~ulfman/ The Karlson has a mediocre reputation, it's main problem being that nobody has yet figured out a way to model & size the things properly. Hopefully at some point in the future Martin King will take an interest as if anyone can crack the math he can. I think GM's got a excel spreadsheet on the Single Driver Site which takes some of guesswork out of it. The Karlson's a fascinating way of loading a driver though, & could well be to your taste. Dynamics are supposed to be a strong point -they certainly were on the pair I heard a while back.
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