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Hello,
I am currently using an active filter on a TAD 4003, crossing over with a 1st order slope at 750hz. I have a 33uf cap in series to protect the driver.
Could I ask a couple of questons? Firstly, is it safe ot use 1st order at that frequency with the TAD 4003? It's used in a domestic enviroment and levels are typically below 100db at 10 feet.
Secondly, given that the active crossover is providing a 1st order slope below 750hz, would I be correct in thinking that the series capacitor increases that to a 2nd order slope an octave below the crossover point?
Any advice much appreciated. I am getting good results but I am getting paranoid about the effects of 1st order!
Follow Ups:
Hello
I have been using TD-4003s for a couple of years (after TD-4002s). I cut them at 400Hz/18dB oct. I think all depends on your amp. I use a 3w max transformer coupled 2A3 set amp and I am convinced it cannot hurt the diaphragms. I think they can endure a watt or two even at lower frequencies.
If you are using higher power and/or solid state amps, careless connection, switch on/off transients, clipping generated harmonics or dc caused by output transistor failure can be a risk. Having blown a woofer with the latter, I would not use a solid state amp without a capacitor or a relay protection circuit.
You could also try with and whithout the protection cap and listen whether you hear any difference.
The TD-4003 is a great driver imo.
Cheers
Christian
Many thanks Christian - yes it seems to be a superb driver.
I have the series cap in front of the driver so thumps etc should be OK. I am hoping this series cap also acts as a second pole on the crossover below 375hz. It seems difficult getting confirmation of that.
My Berning is capable of 70wpc, but in reality, anything above a few watts would deafen me so I doubt that would be an issue. But I'd like the reassurance that the slope I have (including both active and passive elements) results in similar attenuation to the recommended one!
What horn are you using if I might ask?
Yes, the cap before the driver will add a 6dB/oct slope at low frequencies. But the active crossover provides attenuation only of incoming signals. A problem generated in the crossover itself or in the amp (a defect or simply a transient due to plugging or unplugging wires, or a switch on or off transient) will be attenuated by the series cap only. It should be safe, but, considering the price of replacement diaphragms, I would go for an added protection (a relay muting and dc protection for instance). Low power transformer coupled tube amps are great also for the peace of mind they give (a problem could be HT ending up in the output transformer secondary but I have never heard of that).
I belong to the school which prefers large horns to round tractrixes or similar profiles (e.g. JMLC) and use the EV HR9040As at this time.
Christian
Hi Airwise,
I got the Tad 4001, 4002, 2001. You shouldnt worry about your crossover. Unless you got an SS amp that puts out alot of power. If using SET you might aswell bypass your Active and just run the Tads with your Passive. I havent blown one yet even xovered at 250hz the past 10yrs or so. Just crossover passively where you think sounds best.
Now Im assuming that you got proper horns that loads it though. If you got horns that load below 220hz then shouldnt be a problem.
Best,
Victor
Hi Victor,
thanks for that. I'm using a TH-4003 where the recommended crossover is of course 600hz second order. But I think the series cap at 375hz on top of the active unit an octave above, should attenuate LF as well as a 2nd order slope at 600hz.
I'm using a Berning ZH270 at the moment - but drawing any more than a few watts would deafen me anyway in my small living room!
I would NOT recomend a 6db per octave slope with a single cap in series
Tad recomends this driver at
600Hz to 20,000Hz
I would highly consider going with a steeper slope or a higher xover
point if you insist on a 1st order slope
Considering the price of those drivers and the diaphragms you might
want to consider 12db per octave or 24db per octave at that xover point
Hi Stuart,
thanks for the reply. I have a single cap in series but also use a first order slope on the active crossover. The active slope kicks in at 750hz. The series cap, at about 300hz. Would this not increase the slope below 300hz?
I'm also paranoid about the diaphrams, but they are rated at 60w and I'm never putting more than 1 watt through them I would imagine. Do you still think there is a risk?
The risk is mechanical damage, not thermal damage. If they're low Q drivers (not all compression drivers are) then at some low frequency, 1 watt might be enough to cause mechanical damage. What is really probably a risk is that the single series cap removes most electrical damping provided by the amp at low frequencies, so the diaphragm can be modulated by pressure from your low frequency section. However, if you're not running at live concert levels, it's probably not a big issue either. If you want to reduce said risk, either use a second order filter with an inductor in parallel or take out the cap and increase to a second order active filter (which will keep excursion constant or reduce it below resonance).
Thanks John. I apreciate all the input but have been thinking this through.
Doing the sums, I'm fairly convinced that there is no greater risk to the 4003 running this solution of effectively two seperate isolated poles and it sounds so much better than the 2nd order alternative.
Bearing in mind that listening at 106db at the listening position would draw less that 1 watt, and that the drive unit is rated to 60w, I don't think the remote possibility of it receiving 1db more at 400hz is likely to cause damage.
famous last words......
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