Hi all,
Working on my new speakers with a JBL 2452SL that needs dropping in volume by 20db vs a TD10m as its producing a little too much hiss (Hypex Fusion NCore amp)
The driver is a 150w capable unit (not that I ever expect to be maxing this out)
Do you recommend a L-pad or soldered resistor version? most resistors seam to be much lower power (5w),although its for domestic use, I assume this is not enough to run safely?
Thanks.
Working on my new speakers with a JBL 2452SL that needs dropping in volume by 20db vs a TD10m as its producing a little too much hiss (Hypex Fusion NCore amp)
The driver is a 150w capable unit (not that I ever expect to be maxing this out)
Do you recommend a L-pad or soldered resistor version? most resistors seam to be much lower power (5w),although its for domestic use, I assume this is not enough to run safely?
Thanks.
You'd have to use discrete resistors, 20W or more each. Lower power multiples in parallel are ok.
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With such a large series resistor, you may want to add an RC Zobel across the new driver,
to keep the frequency response even.
to keep the frequency response even.
The type of amp doesn't matter at all. The driver inductance causes its impedance to rise with frequency.
The series resistor then attenuates less with increasing frequency, causing the hf response to rise.
This is why Zobels are used, to keep the driver impedance (and the response) constant.
With an acoustic loop this could be corrected, but it should not happen to begin with.
The series resistor then attenuates less with increasing frequency, causing the hf response to rise.
This is why Zobels are used, to keep the driver impedance (and the response) constant.
With an acoustic loop this could be corrected, but it should not happen to begin with.
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Is there still a theoretical advantage at all of a zobel into a fully digital active system, given I can EQ this back down?
That depends on your definition of correction. Almost all horns will need contouring, would this rise not help with the hump of upper mid horn boost.
I'm about to do this with my project so I'm interested to know, also.
I'm about to do this with my project so I'm interested to know, also.
That would be dependent on the details of the system. Feedback works best when it works least,
and acoustical correction is not as accurate as electrical.
You could put the attenuation at the input of the amp rather than its output. This uses the amp as a buffer. It's what I'm doing at the moment. It's not the only way to do it. In my case this reduces the noise with the level.
Would this be as simple as putting an audio grade pot inbetween pre and power amp? Dual gang for stereo?
It could be, yes. There are other possibilities. It would help to know the nature of the two interfaces rather than using a random pot.
Ah, I see. I hope the OP doesn't mind me getting involved, perhaps it might be of benefit.
I have a MiniDSP 8x8 (unknown output impedance and not even sure if it is relevant?) going to two Parasound Zamps (33k ohm input). One of which needs to be attenuated for compression driver/horns but I am not quite sure how much, yet. How would a pot be implemented?
I have a MiniDSP 8x8 (unknown output impedance and not even sure if it is relevant?) going to two Parasound Zamps (33k ohm input). One of which needs to be attenuated for compression driver/horns but I am not quite sure how much, yet. How would a pot be implemented?
Correct me if I'm missing the point, but in this case gain can be controlled through software. In order to reduce hiss, the attenuation amount doesn't need to be variable, or even precise.
I'm OK with discussing alternatives. The issue I sometimes find with pots is channel balance.
If I have understood you correctly, this would not work for me as its the amp producing the hiss.
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Yes. Some are very particular about the low power, low noise amp they choose to drive a compression tweeter for this reason.
Using an L-pad arrangement instead of a single resistor will reduce the effective source impedance driving the tweeter, but it won't likely be enough to prevent response variations sufficiently.
Compression tweeter impedance is often highly varied. High Q artefacts are typically less reliable to quash. Channel imbalance can be an issue. Some would use an impedance conjugate network tuned for each channel. You want to choose carefully how you manage this because you are relying on a secondary effect to maintain performance. Even if you measure each channel and EQ.
Using an L-pad arrangement instead of a single resistor will reduce the effective source impedance driving the tweeter, but it won't likely be enough to prevent response variations sufficiently.
Compression tweeter impedance is often highly varied. High Q artefacts are typically less reliable to quash. Channel imbalance can be an issue. Some would use an impedance conjugate network tuned for each channel. You want to choose carefully how you manage this because you are relying on a secondary effect to maintain performance. Even if you measure each channel and EQ.