Thanks. Its based on our friend Kegger's one, yes. Running on triode mode.
My sense is everyone is awaiting a more firm Zout number from a measurement to best provide commentary. If you have a couple dummy loads (maybe 10W R's, pref non-ind, or 5W if you are fast), all you need is a quick delta V over delta I for a couple values of dummy load. It's just too dicey for these lower-Q driver + SET amp pairings to go in blind and hope. It need not be a highly accurate Zout for this, people just need to know if the thing is closer to 2 ohms or 5 ohms or whatever. Then the box tradeoffs can be juggled more confidently. I don't know those drivers at all so I'm not the guy to ask regarding balancing compromises.
Will you be adding a tweeter or staying single-driver? What sort of usage/location is intended--eg small office/near etc...proximity to boundaries, etc. The more you can paint a picture of how you wish to use them the better input you will get. Do you want to cram them against a wall or will they be out in a room a ways, etc?
BTW, just saw your Keithley & loadline Python stuff -- nice 🙂 Did you build the amp? If so, I'm feeling better about asking you to get a couple AC voltages across a dummy loads. If you are a spice-head, maybe you already have that amp modeled and can just drive it backwards (w/ and w/o the Schade strap) and plot V/I to verify veracity of my swag. The way I see it (could be wrong), the Schade 200k is just another thing in parallel to the plate resistance and the OPT load so it drops Zout to maybe 4.2+ ohms. Adding back some (say) half an ohm for a bunch of wire (another question for you to answer--how far/long), the Qts' is .42 (Qes' .442). If I'm right, no matter what it is, the Fostex recomm reflex box wont have the LF you seek for a single driver only type speaker but you could easily grow the box some as mentioned by others.
Will you be adding a tweeter or staying single-driver? What sort of usage/location is intended--eg small office/near etc...proximity to boundaries, etc. The more you can paint a picture of how you wish to use them the better input you will get. Do you want to cram them against a wall or will they be out in a room a ways, etc?
BTW, just saw your Keithley & loadline Python stuff -- nice 🙂 Did you build the amp? If so, I'm feeling better about asking you to get a couple AC voltages across a dummy loads. If you are a spice-head, maybe you already have that amp modeled and can just drive it backwards (w/ and w/o the Schade strap) and plot V/I to verify veracity of my swag. The way I see it (could be wrong), the Schade 200k is just another thing in parallel to the plate resistance and the OPT load so it drops Zout to maybe 4.2+ ohms. Adding back some (say) half an ohm for a bunch of wire (another question for you to answer--how far/long), the Qts' is .42 (Qes' .442). If I'm right, no matter what it is, the Fostex recomm reflex box wont have the LF you seek for a single driver only type speaker but you could easily grow the box some as mentioned by others.
Last edited by a moderator:
Thank you @grindstone. No tweeter will be used. This is for a small living room area. 20 square metres approx.
Regarding the circular vent port. Can I just replace it with a square (full speaker width) front vent at the bottom?
The circular area is rather small. If replaced with a square vent, full box width, I imagine the height of that new vent would be really short. What's the math behind this? What about the length of the port?
Thank you!
Regarding the circular vent port. Can I just replace it with a square (full speaker width) front vent at the bottom?
The circular area is rather small. If replaced with a square vent, full box width, I imagine the height of that new vent would be really short. What's the math behind this? What about the length of the port?
Thank you!
Thanks for the reply but hold-up, man 🙂 You are going to be asking one driver to do a lot and people are just seeking to give you the best chance at success. Get your hands on a couple power resistors and post an amp output impedance number. It's worth it and the people upstream in your thread are experts. While you have a meter out, get a DCR number for a length of your speaker wire that will be used as well.
Yes. I assume so, but not that simple if I'm following due to major differences in pipe end correction, high aspect ratio acoustic resistance losses that usually requires some fine tuning (critical damping) of the vent design.
Output impedance seems 1,59ohm. (signal of the Sig Gen is 1Vrms at 1Khz).RL=120.4ohm,A1=1.457Vac,A2=1,438Vac)
Perfect--thanks. So my impedance theory of single-stage loop feedback was crap because it inverts 🙂 Thanks for that.
Umkay, give people a bit. In the interim, if you haven't seen it, maybe drop-in this Chang-looking video about 3:30 through 3:45 or so and you can see how the previous rev beams if you hadn't known that. You might plan to angle things (or reconsider some form of HF augmentation, etc.) or tilting with feet or something, etc. Not selling, just pointing out potential considerations.
Umkay, give people a bit. In the interim, if you haven't seen it, maybe drop-in this Chang-looking video about 3:30 through 3:45 or so and you can see how the previous rev beams if you hadn't known that. You might plan to angle things (or reconsider some form of HF augmentation, etc.) or tilting with feet or something, etc. Not selling, just pointing out potential considerations.
After a look, the slot port along the full width of the bottom (with your driver move to the wide side) would get too thin/high-aspect to be functioning similarly, so here's one the shorter way (depth direction) that should get close to the same tuning that the round port in the plan achieves if you still seek such a thing. It's still pretty thin/high-aspect ratio but requires no fancy work. The net size of the reflex box in the plans is basically a cubic foot, give or take so the factory reflex tunes 37-ish with the driver param adjustments.
Last edited by a moderator:
Hi @emartine - I don't know that it was a suggestion, just an effort to make an equivalent tuning to the plan that satisfied a slot shape and bottom location. I just eyeballed the port to be ~55mm/23.8cm2, flipped k-factors for bottom slot tuning and shortened it until it was the same as what the recommended VB was with the 1R59 source-resistance-modified numbers for the driver, the 37.some indicated above.
Last edited by a moderator:
emartine and others:
I have worked with a pair of fe206e off and on for a number of years (about 14 year-old drivers) .
What do members here think about using a passive radiator with the FE206 series, in place of the port, in a box similar to that proposed here? The PR could go on the back.
The FE206 has a short xmax, so an 8” PR should have plenty of displacement, right?
The “affordable” Dayton Audio DSA215-PR 8" has a fairly low Fs (25.6) and high Mms (67g) for it's size; would it force the tuning too low?
What easy-to-use program would work well to model the PR system?
I have worked with a pair of fe206e off and on for a number of years (about 14 year-old drivers) .
What do members here think about using a passive radiator with the FE206 series, in place of the port, in a box similar to that proposed here? The PR could go on the back.
The FE206 has a short xmax, so an 8” PR should have plenty of displacement, right?
The “affordable” Dayton Audio DSA215-PR 8" has a fairly low Fs (25.6) and high Mms (67g) for it's size; would it force the tuning too low?
What easy-to-use program would work well to model the PR system?