PDA

View Full Version : Mix and Match



SMUAlien
03-03-2004, 02:24 AM
Scenario:
I have some M661's by Diamond and I don't like the Aluminum tweeter. I was considering buying some other brand tweeter, maybe the CDT silk dome tweeters for around $50 or maybe some focal tweeters or something.
My question is this: is it OK to put these tweeters in with the DIamond M661 crossover and woofers and remove the aluminum ones? It is my belief that every speaker has different impedance and reactance characteristics for which each crossover was designed. If this is true you would not get great performance from a crossover designed with a different speaker in mind if you changed speakers. Am I correct in this?

If not then I might be putting the M661s up for sale if where I bought them won't take them back. The Aluminum tweeters are just far too harsh for the music type I listen to and my small cabbed truck.

Looking for options and opinions.

adam71
03-03-2004, 04:14 AM
Scenario:
I have some M661's by Diamond and I don't like the Aluminum tweeter. I was considering buying some other brand tweeter, maybe the CDT silk dome tweeters for around $50 or maybe some focal tweeters or something.
My question is this: is it OK to put these tweeters in with the DIamond M661 crossover and woofers and remove the aluminum ones? It is my belief that every speaker has different impedance and reactance characteristics for which each crossover was designed. If this is true you would not get great performance from a crossover designed with a different speaker in mind if you changed speakers. Am I correct in this?

If not then I might be putting the M661s up for sale if where I bought them won't take them back. The Aluminum tweeters are just far too harsh for the music type I listen to and my small cabbed truck.

Looking for options and opinions.

Why didn't you get the Diamond M661s model.?? That one comes with a silk dome tweeter. See if you can exchange for that model. If not see if Diamond will sell you a pair of silk dome tweets that will be compatible with those crossovers.

Adam

SMUAlien
03-03-2004, 01:06 PM
I bought these from eBay, not an authorized dealer and didn't have the option to get the silk tweeters. I contacted Diamond and they say I can buy the silk tweeters for around $100. For that money there may be better tweeters, like CDT's or Focals. If it's bad to mix and match though then that option isn't available.

Berry47
03-03-2004, 02:35 PM
Go to an authorized dealer and get the silk diamond tweeters. THe frequencies that the tweeter begins to roll off might be different between the two comp sets. It could damage the tweeters for them to play lower then recommended.

nosaj070
03-03-2004, 04:45 PM
Just look into it, see where the x-over is set for the tweet, and find one that can handle that range.

helotaxi
03-03-2004, 07:58 PM
Without the proper Zobel network, it doesn't matter what the crossover point is for one tweeter because it won't match up with a different one. Sensitivity matching will also be off and the relative volume between the mid and the tweet will be off unless you use the speakers that the crossover was designed for.

nosaj070
03-03-2004, 08:21 PM
Without the proper Zobel network, it doesn't matter what the crossover point is for one tweeter because it won't match up with a different one. Sensitivity matching will also be off and the relative volume between the mid and the tweet will be off unless you use the speakers that the crossover was designed for.
And yet I was outsmarted again :) **** you helo. Now for the retards(Me) here could you put that in lehmans terms.

helotaxi
03-03-2004, 08:58 PM
If you look at the impedance plot for a speaker throughtout its frequency range, it is not flat. There is a peak around resonance (very pronunced on a woofer/mid usually and not as bad on a tweet.), a dip right after resonance and then a gradual rise as the inductance of the voicecoil becomes a factor at higher frequencies. A passive filter network (a crossover is just a frequency filter) depends on the impedance of the load it is connected to to determine its rolloff point. All a crossover does in fact is increase the impedance above the crossover frequency for a lowpass filter and below the crossover frequency for a highpass. If the impedance of the speaker is not relatively flat from the xover point and up for a low pass and from the xover point and down for a high pass (basically through the frequency range you are trying to attenuate with the filter) then the filter will not work correctly. What this means is for a woofer you need to counteract the gentle rise in impedance causes by voice coil inductance with a cap and resistor and tame the peak at resonance for the tweet with an inductor and resistor. This gives the drivers flat impedance curves through the crossover region and allows the crossover to be designed for a fixed load impedance and predictable frequencies and rolloff and response characteristics. A Zobel network is the name for the flter use to normalize the impedances. The values of the caps, coils and resistors used in the network are determined by the characteristics of the speakers so unless you are swapping out a driver for one with the same impedance characteristics, the Zobel won't be correct. If the Zobel is not correct, the crossover cannot be correct. You will either have a shift in frequency or a really ragged response.

The other function that a good crossover will perform is level matching. If, for example, the tweeter has a sensitivity of 92 dB/Wm and the woofer has 89dB/Wm the two drivers will not blend together nicely because the tweeter will be louder than the woofer. To fix this, you increase the impedance of the tweeter with an attenuation circuit and burn up a bit of power with a resistor. This presents the crossover with an even different impedance than just the Zobel and must be accounted for in the values of the components in the crossover.

As you can see, the design of a crossover is pretty complicated if you want to do it right. Its function is entirely dependant on the drivers being used and you can't take a crossover designed for one driver and expect it to work well with another.

nosaj070
03-03-2004, 10:05 PM
Never really understood crossovers until that, thank you very much.

SMUAlien
03-04-2004, 02:15 AM
I do most of my thesis research on Microwave Impedance matching structures in microstrip and the same thing applies here. The impedance (real and reactance) of a load can change the resonant points of all the resonators in the entire structure. Resonant points are placed to create a certain frequency response for a specific load, if the load is changed the frequency response usually changes as well. Like you described this can cause a shift but can also have the effect of reflecting energy and creating a standing wave ratio.

I figured that this would be the case but I honestly had no clue about the real and reactive characteristics of today's modern tweeters. I figured that since they were all designed with a car audio implementaion in mind at 4Ohm impedance, they would PROBALLY have similar real and reactive components. I didn't really even think of sensitivity matching. If I remember correctly every 3dB of sensitivity means another 50% increase in efficency. So something of 92dB has 50% of the remaining energy being used than something at 89dB. It's late and I probally got that wrong.

Thanks for your help, I guess I'll just have to sell my M661's and get a complete setup that has a tweeter I can live with. Cost wise this seems like the most effective thing to do rather than just buying new silk tweeters from Diamond.

Notwerk
03-10-2004, 01:40 AM
Helo,

I know it would be a more expensive and complicated solution, but couldn't he just use an active crossover and then use any tweeter of his choice?

helotaxi
03-10-2004, 07:13 PM
Helo,

I know it would be a more expensive and complicated solution, but couldn't he just use an active crossover and then use any tweeter of his choice?
Sure, and that will keep his crossover point stable once power compression sets in, but the nice thing about using the supplied crossover is that the Zobel network, by leveling the impedance across the frequency range, also levels the frequency response by normalizing the power delivered to the speaker across its range.