The crossover in the David plans will take into account acoustic impedance.tomlang wrote:Excellent explanation. In my mind I'll think of this as "electric impedance" and "acoustic impedance". The electric impedance being the speaker impedance (eg 4 ohms) and acoustic impedance (eg 2 ohms).
OK, so now I have plans for the David speaker. It, like the Tuba 18 referened earlier, has in the plans stated a 6 ohm woofer impedance using the 4 ohm MCM speaker.
I'm thinking of getting a dvc speaker with two 4 ohm coils wired in parallel. OK, then 2 ohm "electrical impedance" and another 2 ohm "acoustical impedance" for a total of 4 ohms load now not 6 ohms.
The David speaker uses a crossover that would need to be modified for use with a 2 ohm impedance speaker.
The question is: Do the inductor and capacitor values in the plans reflect the 4 ohms "electrical impedance" or 6 ohms "electrical + acoustical impedance"? I need to know so I can scale the inductor and capacitor values. For example, if the woofer crossover was originally designed for 6 ohms, I need to scale the inductors by 2/3. If the woofer crossover was originally designed for 4 ohms I need to scale the inductors by 1/2.
Thanks!
So, as you say, not using the recommended driver will require recalculating components.
I'm not sure it's so simple as saying 2/3 or 1/2, because I think you also need to take into account the impedance plot (manufacturer supplied) of the driver you intend to substitute with, at the crossover point to mid bass. If you can't get an impedance plot, then you're stuck.
If it's about saving money that you're looking to substitute, then the recommended MCM is on sale right now at $30, the Dayton is $52 at PE and the Tang Band is $72, also at PE.
Use any of the three and you don't have to change anything!
You also know the results with these drivers will perform as expected.
If you go with a DVC, you need to look closely at depth (ie will it fit), and you going to reduce chamber space...
