I don't have a problem with a 12". I have just not heard much of them before so I have no judgement but a trusted and VERY experienced friend recommended the Magnum 12HO for being good to 1KHz.
P.S. I added something to my last message.
P.S.S I considered different woofers for about 4months. The Magnum 12HO is the one for the job! The JBL2206 might also do very well or maybe even better but I'm not sure where to buy it in the UK and it is stupid expensive.
P.S. I added something to my last message.
P.S.S I considered different woofers for about 4months. The Magnum 12HO is the one for the job! The JBL2206 might also do very well or maybe even better but I'm not sure where to buy it in the UK and it is stupid expensive.
The pole piece of my Fostex's is very strongly magnetized. With a magnetic pole piece, how close can the back of the tweeter be to the pole before that magnetic field interfere's with the tweeter operation?
Also note that the dust cap has a purpose, to keep dust, sand, insects, and whatever else out of the magnetic gap. If you plan to use the speakers in a harsh environment, you may want to reconsider removing it.
Also note that the dust cap has a purpose, to keep dust, sand, insects, and whatever else out of the magnetic gap. If you plan to use the speakers in a harsh environment, you may want to reconsider removing it.
Sensitivity is not an issue I'm doing this active.
The point about the magnetic field of the woofer is good though. hmm.... I had better put a shield around the back of the tweeter. Maybe this http://www.madisound.com/cgi-bin/index.cgi?cart_id=6432456.4395&pid=414
It is a bit deep and not quite wide enough but I could probably make it fit.
Anyone got some good places to get a shielding cup that will fit a 77mm wide tweeter body 25mm deep??
The point about the magnetic field of the woofer is good though. hmm.... I had better put a shield around the back of the tweeter. Maybe this http://www.madisound.com/cgi-bin/index.cgi?cart_id=6432456.4395&pid=414
It is a bit deep and not quite wide enough but I could probably make it fit.
Anyone got some good places to get a shielding cup that will fit a 77mm wide tweeter body 25mm deep??
I believe a shield will also affect the magnet of the tweeter.
I'm not trying to knock the idea at all. I've often thought of doing the same thing, but there must be some issues in doing it. If not, wouldn't we see the manufacturers doing so? Even with a selection of different tweeters to screw right into the front of the pole piece, for perfect physical time alignment. Is using a compression driver firing through a horn inside the pole piece superior in some way?
I'm not trying to knock the idea at all. I've often thought of doing the same thing, but there must be some issues in doing it. If not, wouldn't we see the manufacturers doing so? Even with a selection of different tweeters to screw right into the front of the pole piece, for perfect physical time alignment. Is using a compression driver firing through a horn inside the pole piece superior in some way?
Well, you often get shields that can be added to normal drivers (the one I linked is for a Vifa) so it can't have much of a negative effect.
Would the magnetic field of the woofer just give it greater sensitivity then, Snickers?
If you can't connect a ribbon directly to an amp then how do you power it?! Do you have to use a series resistor? If so, why don't they build that into it?
Seas may make some like that, but they can design both drivers to work together. I think mainly the tweeter will just gain a few dB sensitivity.
This is quite an interesting thread!
Would the magnetic field of the woofer just give it greater sensitivity then, Snickers?
If you can't connect a ribbon directly to an amp then how do you power it?! Do you have to use a series resistor? If so, why don't they build that into it?
Seas may make some like that, but they can design both drivers to work together. I think mainly the tweeter will just gain a few dB sensitivity.
This is quite an interesting thread!
Variac said:
I wouldn't say "matches" because typically those tweets have to be padded way down, but I appreciate the durability need for PA.
Snickers-is said:
I don't think it would take a lot of distance. I tried the socket for a phase plug on my Fostex 206's and the pole piece magnetism really grabbed the socket in the last few mm's and slammed it to the pole piece despite my firm grip with pliers.
Bucking magnets affect a driver's T/S parameters as do adding magnets to the back of drivers. Even adding the metal socket to the pole piece changes the T/S parameters of the big magnet 206, so if the pole piece is steel, I believe you'd want some safe separation from the tweeter. Since it's just over an inch deep, you may need some spacing to get the physical alignment you want anyway.
How are you going address the phase shift of your XO, since you are looking for perfect time alignment?
If the shielding is done right with a reverse magnet it will not affect the performance. If the shieling is done with a narrow cup alone the field may be short circuited as the cup shorts the magnet field from the base plate to the pole plate. On Seas drivers the effect of shielding is minimal. Normally less than 0,1 gain in BxL.
A ribbon needs to be connected through a capacitor or a resistor. This is to get some DCR, or to get some gain in impedance towards lower frequencies. When used with digital filters the most common way to solve it is to use a large capacitor that has minimum effect in the working range.
The magnet field will not have any gain. The magnet sets the magnetic potential of the magnetic circuit. The load is in the magnet gap. The only way to make the field stronger is to gain magnetic power in series with this circuit. Adding some magnetism at the base of the tweeter is almost like trying to add some current to a wire in a closed circuit. To get the current flow you will need to connect the other wire to something to.
A ribbon needs to be connected through a capacitor or a resistor. This is to get some DCR, or to get some gain in impedance towards lower frequencies. When used with digital filters the most common way to solve it is to use a large capacitor that has minimum effect in the working range.
The magnet field will not have any gain. The magnet sets the magnetic potential of the magnetic circuit. The load is in the magnet gap. The only way to make the field stronger is to gain magnetic power in series with this circuit. Adding some magnetism at the base of the tweeter is almost like trying to add some current to a wire in a closed circuit. To get the current flow you will need to connect the other wire to something to.
johninCR said:
I'm not going for 'perfect' phase I'm just trying to get it as good as I can. The main reason for going coaxial is to get as close to a point source as possible for good imaging and the ability to use high order slopes. As I am going to use a very steep filter, probably 48dB/octave, the phase changes, true, but the area it does it over will be minimal. Then at least the rest is in phase. Remember the digital Xover has delay so I can account for small differences, just not frequency specific ones. How would one normally account for Xover phase shift? …Why don’t people make Xovers with the choice to use FIR filters instead?
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