Hello!
I have a pair of Fostex FE206NV2 arriving soon.
Since this is my first speaker project and I am not that good at wood working, I was planning on building this bass reflex enclosure (the one suggested by Fostex), instead of the backloaded horn one.
Can I just mount the speaker on the 308mm width board, instead on the 248mm width one, without any modification?
What internal reinforcement to the box do you recommend?
Thank you!
I have a pair of Fostex FE206NV2 arriving soon.
Since this is my first speaker project and I am not that good at wood working, I was planning on building this bass reflex enclosure (the one suggested by Fostex), instead of the backloaded horn one.
Can I just mount the speaker on the 308mm width board, instead on the 248mm width one, without any modification?
What internal reinforcement to the box do you recommend?
Thank you!
Yes, you can orient the driver on the "side" 323mm wall, no problem. I would myself orient the driver some TEN millimeters horizontally offset from the centerline of the cabinet to avoid baffle-step frequency "additions".
And considering the outright smallness of the enclosure, if you were to bump up the panel thickness to 19mm, AKA "one inch"...reinforcing wouldn't really be necessary.
BTW, I simmed up my own enclosure size & got a smaller dimension than that of Fostex....my volumes of 27 liters, fb 66 hertz, -3.06 Db@62.78 hertz, to Fostex value of 39 liters worth of volume.???
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------Rick...
And considering the outright smallness of the enclosure, if you were to bump up the panel thickness to 19mm, AKA "one inch"...reinforcing wouldn't really be necessary.
BTW, I simmed up my own enclosure size & got a smaller dimension than that of Fostex....my volumes of 27 liters, fb 66 hertz, -3.06 Db@62.78 hertz, to Fostex value of 39 liters worth of volume.???
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------Rick...
I never trust Fostex’s reflex boxes.
Checking this one, looks like a pretty ugly alignment (not as bad as some i have seen). The nice sim is 12 litres, does much better thzan the previous FE206.
dave
Checking this one, looks like a pretty ugly alignment (not as bad as some i have seen). The nice sim is 12 litres, does much better thzan the previous FE206.
dave
Really curious why you chose that particular driver for a small BR enclosure? Must have something to do with efficiency.
jeff
T/S max flat alignment (no Rs):
Vented net volume (Vb) (L) = 20*Vas*Qts'^3.3 = 11.78 L
(Ft^3 = (Vb)/~28.31685) = 0.416 ft^3
Vented box tuning (Fb) (Hz) = 0.42*Fs*Qts'^-0.96 = 68.42 Hz
F3 (Hz) = Fs*0.28*Qts'^-1.4 = 82.51 Hz
(Qts'): (Qts) + any added series resistance (Rs)
Vented net volume (Vb) (L) = 20*Vas*Qts'^3.3 = 11.78 L
(Ft^3 = (Vb)/~28.31685) = 0.416 ft^3
Vented box tuning (Fb) (Hz) = 0.42*Fs*Qts'^-0.96 = 68.42 Hz
F3 (Hz) = Fs*0.28*Qts'^-1.4 = 82.51 Hz
(Qts'): (Qts) + any added series resistance (Rs)
thank you. what software did you use for sim? do you have the same pair in Bass Reflex?
you suggest this speaker on a 12litre box?
is that the black curve? whats the yellow one? cannot really see it
The black line without the whoops*. Yellow is impedance, red is excursion, blue is group delay.
The FExxx drivers typically want to be in a horn if you want bass. Or you put it in a selaed box (7 litres) and cross to woofers at 120 Hz (Bottlehead style).
dave
*(a guidline i follow is that the 1st derivative of the FR does not cross zero more than once. Quality over quantity [or in actuality, LF extension]).
I looked up the T/S parameters of your Fostex & plugged them into the WINisd beta simulator. The program processed all the parameters, selected the vented bass-reflex as the best choice...as shown by an obvious Efficiency bandwidth product pushing one-hundred. The "factory suggestions" of enclosure volume & box tuning frequencies (fb), I felt could be reworked slightly to get some extended bottom end abilities.
By manipulating both box volume and frequency, one can get better performance. By paying attention to the response graphing & manipulation of the numbers, one gets a larger box as your attempting to increase low-end performance.
No, I don't own these Fostex units, I do however have a pair of full-range five-inch drivers that I fabricated an enclosure for, an aperiodic alignment. Since the drivers had been in production virtually unchanged for many years, others had experimented endlessly & I took their recommendations, a seventeen liter-sized enclosure with a one-inch hole in the back, the hole itself "plugged" with sound absorbing material...a resistive vent, an aperiodic alignment.
The performance was better than I expected...a result of taking others advice derived from numerous experiments.
-----------------------------------------------------------------------------------------------------------------------------------------------------------------Rick...
Thank you @Richard Ellis / @GM / @planet10
What would you suggest to get a little better bass performance?
May be changing vent tuning?
F3 at 82Hz might be a little too high for my taste.
Thank you again.
What would you suggest to get a little better bass performance?
May be changing vent tuning?
F3 at 82Hz might be a little too high for my taste.
Thank you again.
It seems like Fostex recommended box is designed for use with high resistance amps like SET or similar. That gives higher Qts, so vented box aligment can be shifted to bigger box and lower tuning.
If you have low resistance amp like standard transistor type, just add 2-3 Ohm resistor in series with driver. That will boost the bass and smooth the response. At expense of some efficiency.
If you have low resistance amp like standard transistor type, just add 2-3 Ohm resistor in series with driver. That will boost the bass and smooth the response. At expense of some efficiency.
Yes, that's the usual. Until the NV series the baseline assumption was that they were on the end of a SET or similar with about 2ohms - 4ohms output impedance depending on driver model, or were going to be used in a fairly typical small Japanese space, potentially leaching LF that might disturb neighbours & the like, hence some of the alignments that can look a bit odd to others, often entering some form of EBS or similar trending. With the NV series, that's changed a bit; they're a bit nearer to the values of the old FExx7E series units. Still better, at least in the case of the 206, with a higher amplifier output impedance than a typical SS amp etc. provide. A series resistor as suggested, or resistive speaker wire can help if you don't have a suitable amplifier & want one of the larger cabinets but with a slightly more linear alignment trend.
That is the impedance of the transformer tap, not the output impedance of the amplifier.
dave
Could be if designed as such, but really need it measured to find how much series resistance to account for.
Quick search => OP mentioning SET & Kegger's KT88 design (over on AK) at ~3W. If that's triode & 5k, rough-tough 5k || 6150 reflected 25:1 ~ 4.4 ohms so a bit less than that with the Schade. If it's not triode (UL), it'd be worse...to blindly throw a dart at a frequency-dependent quantity (commonly SE Zout drops at LF, rises at HF). Corrections welcome, but I'm not seeing any global NFB to lower it any. FWIW.