8 replies to this topic

[~Spyne~]

ok, i have some crossovers at home that are really quite good and they are designed for 8ohm midbass drivers and 4ohm tweeters. the crossover point is 3.5khz @ 12dB

what i want to do is build some diy home audio speakers to improve on my first effort that used focal 165v2 (which turned out pretty good)
now the dilemma is the drivers i want to use will either be an 8ohm midbass (fine) teamed with a very good 8ohm tweeters, OR the same 8ohm midbass teamed with a slightly lower performing, but significantly cheaper 4ohm tweeter.

what i want to know is, by using the 8ohm midbass AND 8ohm tweeter, how does this effect the crossover?

help appreciated, cheers

[Pulse-R]

the tweeter crossover will be an octave lower - 1.75kHz or so.

also, since the crossover is likely for different drivers, the impedance (and hence phase) would likely be wrong.

any Zobel correction would also likely be incorrect, leading to low efficincy, or humps in the impedance response - again causing phase errors.

if the Le (inductance) of the woofers is the same, or within 20%, should be fine for the woofer.

the tweeter crossover will be the problem, and possibly also the impedance and sensitivity may be an issue for level matching.

[~Spyne~]

bugger

thanks simon

[muzzy66]

On top of this, the crossovers will also be designed to level-match the two original drivers, so there would be sensitivity compensation in-built.

If the new drivers don't have identical sensitivities to the original drivers they are replacing, then the levels will be incorrectly matched and the tweeter will be too loud for the mid (or vice versa).

Edit: Never mind, Pulse-R listed that already

Edited by muzzy66, 13 May 2009 - 10:42 PM.

[NiFTiTEk]

Pulse-R, on May 13 2009, 09:46 PM, said:

the tweeter crossover will be an octave lower - 1.75kHz or so.

I haven't designed a crossover for some time now I get all mine outsourced from
someone that measures the TS specs of my drivers and response. impedance etc.
as its too hard to get it right with only theory, calculations and ts specs.

But isn't the crossover point be shifted UP one octave not down with a higher
resistance/impedance load?

-Frank-

Edited by NiFTiTEk, 16 May 2009 - 12:06 AM.

[Pulse-R]

down for HP, up for LP

[NiFTiTEk]

Just revisited the past and its a bit hard to say.

1st order butterworth crossover frequencies will increse with the high and low pass as resistance is
increasing.

2nd, 3rd, and 4th order crossovers will vary as the inductor changes are not constant with the capacitor
value changes as resistance increases, I would just re-design as its too complex to predict what it will do
with anything other than a 6db/1st order filter.

Cheers,

-Frank-

Edited by NiFTiTEk, 22 May 2009 - 07:34 PM.

[xMplar]

yeah what he said ^^^

[Pulse-R]

HP crossover is 4 ohms at XO, 8 ohms below XO.
so the HP XO will be lower with an 8 ohm driver.

LP crossover is 4ohm at XO, 8 ohm above XO
so the LP XO will be higher with an 8 ohm driver