Advice on speaker and XO impedance, please explain to me like I'm 5 years old...

[Luke H]

Hi,


Im building a boombox type set up so I dont need stero audio, my plan to econonimise on time and money is only make one crossover curcuit, split it half and run tweeters on L and woofer on R with the amp potentimeter shorted to mono. I've simmed up this design on Xsim, all is well but the impedence values change drasticly whe I "cut the system in half" as explained.


This has lead me to one question... whats the deal with impedence man?
More specificaly how do I tell if my impedance levels are "safe" for the amp and system? Also how do I understand this is terms of xsim and more genrally?


Heres some screen shots for refference:
If these impedance values are problomatic any surgestions on how I might fix them would be greaty apriciated



Thanks, Luke.

 

[rayma]

You can just use each driver full range with no crossovers. The bass should be better with both
woofers playing. If you still want only mono, short the wipers of the volume control together.
I would use a switch for this so you still have the option of stereo. Load impedance won't be a problem.
Make sure that the woofers are connected in phase.

 

[Luke H]

Heres a better view of the impedance graph with a better scale

 

[Luke H]

You can just use each driver full range with no crossovers. The bass should be better with both
woofers playing

Won't you get all the cone break up from the woofer that way? (not that the Dayton DC160 is too bad for break up in this case) Also won't you risk distoration and damage to the tweeters when they try to drive LF?
In this design both woofers are playing already but maybe I misunderstand what your saying?



Thanks, good tip with the switch! Taking that idea further do you think you could use a low value pot to attenuate tweeter (or woofer) volume by wiring it in a "pan" config. i.e.

PIN 1 : L input
PIN 2 : MONO output (to amp)

PIN 3: R input
Could this be a simple alternative to tuning the tweeter volume (by ear) opposed to soldering and desoldering ristors? Just a side thought.


Re: woofer phase, thanks will do!

 

[Galu]

Hi Luke!

For boombox purposes, I'd be inclined simply to run the two series woofers straight off the R channel without a crossover, letting their natural rise in impedance with frequency and their mechanical roll off act as an elementary low pass filter.

The series tweeters can be run off the L channel, but of course you must include your high pass LC filter to prevent the bass frequencies from destroying them.

The impedance of such a combination will be safe for your amp.

Have I interpreted your intention correctly?

P.S. I would lose that resistor in parallel with the tweeter combination?

 

[AllenB]

Your impedances will work (notwithstanding what I said in another thread). They look like they vary alot, but in this case it should be OK.

Won't you get all the cone break up from the woofer that way?

I'd have thought so. Maybe the other members have some experience with this woofer? or maybe are trying to oversimplify your options?

 

[Luke H]

Thanks for your help so far everyone! I'm glad to know the inpedance is ok, but how do I know for myself if its ok? Am I looking to see if it drops below 4ohm (or whatever the minimum nominal limit of amp is) or is there other factors to take into account too?

 

[AllenB]

Start like that, looking for low regions, that will get you by most of the time. Some more experienced designers might take an interest in the finer details.

 

[rayma]

do you think you could use a low value pot to attenuate tweeter (or woofer) volume by wiring it in a "pan" config. Could this be a simple alternative to tuning the tweeter volume (by ear) opposed to soldering and desoldering ristors?

Sure. Do try the woofers full range, many good speakers are made that way.
You can use the balance control as a relative level adjust for the tweeter and woofer,
if you leave that in the circuit. Or add a different one.

 

[Luke H]

quote: Do try the woofers full range, many good speakers are made that way.


True, thats a good point. I'm always surprised at the low number of components in some good sounding commercial hifi speakers. Cheers

 

[Luke H]

Start like that, looking for low regions, that will get you by most of the time. Some more experienced designers might take an interest in the finer details.

Thanks AllenB

 

[Lojzek]

If I were you, I'd get a pair of car audio co-axial units, the larger ones for better bass and use as a stereo. These already have some kind of simple hp filter for tweeter. No need for further crossovers.