I’m working with some at Marcel Batik’s thread Acoustic Horn Design – The Easy Way (Ath4) to build a two-way speaker using one of Marcel’s horns. ATH - A460D https://cults3d.com/en/3d-model/various/ath-a460d-stl-kit
And we are designing the passive crossovers to include my clones of Gary Dahl’s midwoofers. Altec 416-8B in 100L Sealed
I intended to drive these speakers with my First Watt J2 or F4 amps. But after running simulations we found the midwoofers will have an EPDR (Equivalent Peak Dissipation Resistance) of 2.5 ohms at ~ 100Hz. Such amplifier loading concerns have been amply discussed here.
Stereophile has started calculating EPDR.
Said Fluid: I traced Joseph Crowe's measurements of your woofers and combined them with simulated directivity to make a start on what a crossover might look like. One thing I have noticed is that the EPDR is quite low around 100Hz the purple trace in the impedance graph. Dipping down to 2.5 Ohms.
What this means is that you will need to use an amplifier on the woofer that is OK to work with 2 ohm loads. I doubt the F4 and the like will do that. Although the ordinary impedance is not a problem, the combination of it with the negative phase angle gives the amplifier a hard time. A similar thing happens at 500Hz due to the positive phase angle. Using a notch at the woofers Fs flattens the impedance but does not really have much of an effect on the EPDR to make it worth the extra very large components.
This is an acoustic 2nd order at 600Hz. Anything from 500Hz to 800Hz 2nd or 4th order seems to work OK without needing a lot of components.
Please see attached measurements.
Below ~70Hz the speakers will be assisted by multiple subwoofers and my average peak listening level is ~ 82dB at 10 ft in a ~ 2700 cu ft room.
But given the speaker’s very low EPDR I don’t want to risk getting anywhere near amplifier clipping or overheating at lower than expected levels.
I haven’t asked Fluid about this yet but would not the best remedy be to design a series LCR conjugate network to add in parallel to the passive crossover so that the amplifier won’t see anything but an impedance of ~ 5 ohms or higher?
If not please recommend one or more low power solid-state or tube Class A or Class AB amps that can handle 2 ohms loads with low distortion at my relatively modest listening levels.
Ideally, an amp between ~ 15 watts to 7 wpc or less (e.g. a 2A3 DHT tube amp?). Power draw under 200 watts? Makes? Models?
Or a recommend custom builder? Tube or solid-state.
And we are designing the passive crossovers to include my clones of Gary Dahl’s midwoofers. Altec 416-8B in 100L Sealed
I intended to drive these speakers with my First Watt J2 or F4 amps. But after running simulations we found the midwoofers will have an EPDR (Equivalent Peak Dissipation Resistance) of 2.5 ohms at ~ 100Hz. Such amplifier loading concerns have been amply discussed here.
Stereophile has started calculating EPDR.
Said Fluid: I traced Joseph Crowe's measurements of your woofers and combined them with simulated directivity to make a start on what a crossover might look like. One thing I have noticed is that the EPDR is quite low around 100Hz the purple trace in the impedance graph. Dipping down to 2.5 Ohms.
What this means is that you will need to use an amplifier on the woofer that is OK to work with 2 ohm loads. I doubt the F4 and the like will do that. Although the ordinary impedance is not a problem, the combination of it with the negative phase angle gives the amplifier a hard time. A similar thing happens at 500Hz due to the positive phase angle. Using a notch at the woofers Fs flattens the impedance but does not really have much of an effect on the EPDR to make it worth the extra very large components.
This is an acoustic 2nd order at 600Hz. Anything from 500Hz to 800Hz 2nd or 4th order seems to work OK without needing a lot of components.
Please see attached measurements.
Below ~70Hz the speakers will be assisted by multiple subwoofers and my average peak listening level is ~ 82dB at 10 ft in a ~ 2700 cu ft room.
But given the speaker’s very low EPDR I don’t want to risk getting anywhere near amplifier clipping or overheating at lower than expected levels.
I haven’t asked Fluid about this yet but would not the best remedy be to design a series LCR conjugate network to add in parallel to the passive crossover so that the amplifier won’t see anything but an impedance of ~ 5 ohms or higher?
If not please recommend one or more low power solid-state or tube Class A or Class AB amps that can handle 2 ohms loads with low distortion at my relatively modest listening levels.
Ideally, an amp between ~ 15 watts to 7 wpc or less (e.g. a 2A3 DHT tube amp?). Power draw under 200 watts? Makes? Models?
Or a recommend custom builder? Tube or solid-state.
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