at your most cautious, what would you suggest. i'd rather not destroy good equipment through my complete ignorance when playing.
i'm sorry i missed this, and to be perfectly honest i don't entirely understand what you mean.
can you define what you mean by a passive system please.
sorry for my ignorance, only been reading about this stuff for a few months.
1.5uF in series followed by 0.33mH in parallel is plenty cautious, it should knock the tweeter off around 9khz and keep it from getting fried.
A passive system uses a filter after the power amp (e.g. almost every HiFi speaker you buy in the stores)
An active system uses filters before the power amp(s) (e.g. almost any professional monitor)
Passive is a system where the drivers use crossover components after the amplifier to send appropriate frequencies to each driver, where active means that each driver has it's own amplifier and the crossover is before the amplifiers, so each amplifier and it's associated driver receives the appropriate frequencies.
The issue with active here is, using a delicate ribbon tweeter, even though you're only feeding 9khz and up to the tweeter's amplifier, you still have the risk of a turn on / off "thump" or a sudden jolt of hum from, say, accidentally unplugging an RCA cable being sent to a ribbon tweeter and cooking it alive. People normally use a "protection capacitor" on a tweeter even if they have a fully active system just to keep accidental low frequencies from damaging their tweeters.
S'ok, we just wanna make sure you're armed with as much info as you can be.
Last edited:
so like this?
no need for the talk of resistors etc?
no need for the talk of resistors etc?
An externally hosted image should be here but it was not working when we last tested it.
Yes just like this!
Resistors can come into play if you want to match the sensitivity of the tweeter to the woofer, but because you are bi-amping you should do this with the gain of the amp(s)
Resistors can come into play if you want to match the sensitivity of the tweeter to the woofer, but because you are bi-amping you should do this with the gain of the amp(s)
ah, ok, thats a lot different then
you could have said from the beginning
midrange is the best thing there is, and bass
and low midrange especially
thats why we have the magic word BSC
but might depend on your driver size, and baffle size
but you definately want to tame the top
you have no idea how bad it sounds when theres no lower midrange
or too little of it
usually results in badly screaming tin sound
Oh, one more note, make sure you get a non-polarized capacitor. These would probably be great:
ERSE - PulseX
and
ERSE - ALQ Coils.
ERSE - PulseX
and
ERSE - ALQ Coils.
like TV speakers yes?
this is the plot of the experimental box that is in construction, with the correct room placement (@ 1m), using the MJK worksheets. i'm not sure how i would calculate the SPL for 2 of these however. they will probably be cut off @45-50hz and supplemented with the subwoofer mentioned previously. i'm hoping this will be enough for most my uses. the room position levels the port/terminus out quite drastically it seems.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
i have been playing with the EDGE. excellent piece of software.
i came across a paper on posted on the fullrange forums for baffle shape and i'll have a play with a few different designs and try and avoid having to use anything like that, or at least minimise it enough that slight electronic EQ fiddling will do the rest.
this is what EDGE gives me for the Fane driver on its own in the box.
from my reading i should be able to negate a lot of that peak with a better choice of baffle shape/depth and profile rounding apparently?
An externally hosted image should be here but it was not working when we last tested it.
He-he,
You must be feeling better now after >50 posts...
http://www.cartoonstock.com/newscartoons/cartoonists/mba/lowres/mban676l.jpg
Attachments
Last edited:
I know this is an old thread but after reading the whole thread I need to bring up a few very important points that either people don't know about or don't seem too worried about.
Most people when they look at a driver they notice it is typically either an 4 ohm or 8 ohm driver or something in between. This spec is the AC impedance that it presents to the amp output or the other xover passive components. It is this spec that is used in the calculations to select xover values for the other passive components.
This is not the spec that needs to be looked at to determine whether or not the driver actually requires a coupling cap. The spec that needs to be looked at is typically referred to as DCR in the data sheet, dc resistance is the resistive load that the amps output sees when the driver is connected directly to the amp output terminals. Most cone style drivers(with the typical voice coil) like bass drivers, midranges and dome tweeters have a fairly high DCR, typically around 3 to 5 ohms resistance, that's not impedance, it's impedance could still be 4 to 8 ohms with a DCR of 3 ohms. Most amps can handle this range of DCR from cone style drivers.
Most ribbons have a coupling transformer who's primary winding(the part you connect to the xover or cap) which presents (typically) a very low DCR. Ribbons like the Raals have a DCR of 0.25ohms, Founteks typically have a DCR of 0.02ohms, other slike Daytons seem to have a higher DCR up around 4ohms, Ravens have a DCR of about 3ohms.
If you connect a resistor(or the primary of a ribbon's transformer) of 0.02 ohms or 0.25ohms to your amps output that will look pretty much like a short circuit to most amps and will either take out the fuses or worst might take out the output devices, ouch. In order to protect your amp you would then need to put a capacitor in series with the ribbon's terminals. Some ribbons like the Ravens or the Daytons could get away without one, as far as your amp is concerned, but without one, a good turn-on thump, which is a high( a couple of volts to 10s or more) spike of DC voltage might just take or your tweeter.
Your choice, to use or not to use.
Most people when they look at a driver they notice it is typically either an 4 ohm or 8 ohm driver or something in between. This spec is the AC impedance that it presents to the amp output or the other xover passive components. It is this spec that is used in the calculations to select xover values for the other passive components.
This is not the spec that needs to be looked at to determine whether or not the driver actually requires a coupling cap. The spec that needs to be looked at is typically referred to as DCR in the data sheet, dc resistance is the resistive load that the amps output sees when the driver is connected directly to the amp output terminals. Most cone style drivers(with the typical voice coil) like bass drivers, midranges and dome tweeters have a fairly high DCR, typically around 3 to 5 ohms resistance, that's not impedance, it's impedance could still be 4 to 8 ohms with a DCR of 3 ohms. Most amps can handle this range of DCR from cone style drivers.
Most ribbons have a coupling transformer who's primary winding(the part you connect to the xover or cap) which presents (typically) a very low DCR. Ribbons like the Raals have a DCR of 0.25ohms, Founteks typically have a DCR of 0.02ohms, other slike Daytons seem to have a higher DCR up around 4ohms, Ravens have a DCR of about 3ohms.
If you connect a resistor(or the primary of a ribbon's transformer) of 0.02 ohms or 0.25ohms to your amps output that will look pretty much like a short circuit to most amps and will either take out the fuses or worst might take out the output devices, ouch. In order to protect your amp you would then need to put a capacitor in series with the ribbon's terminals. Some ribbons like the Ravens or the Daytons could get away without one, as far as your amp is concerned, but without one, a good turn-on thump, which is a high( a couple of volts to 10s or more) spike of DC voltage might just take or your tweeter.
Your choice, to use or not to use.
Hi Walter, no issue whatsoever with 10 years of using various ribbon tweeters on different amps.
I guess that's a problem with certain amplifiers.
I guess that's a problem with certain amplifiers.
If the crossover is passive, the cap in series with the tweeter sets the high pass filter effect -3dB point. For a one pole crossover, the formula is
C = 1/(2 X pie X Frequency (of rolloff) X resistance and driver impedance as viewed by the cap).
The resistance that needs to be added to the driver impedance is for the case where the tweeter is more efficient than the woofer, so needs a series resistor to reduce it's output a bit. If you're new at this, I wouldn't try to do a 2 pole or more passive crossover. Too hard to get it right. With X = 7kHZ or above, one pole should work fine unless you want it to run extremely loud.
If the crossover is active, implying that the tweeter will be connected directly to the output of a power amp, there's a different situation. Ribbon tweeters have matching transformers inside of them, since the ribbon itself is less than one ohm. At tweeter frequencies the power amp will see the impedance rating of the tweeter (8 ohms for example). At DC the power amp will see a short circuit of less than an ohm (the primary winding of the matching transformer inside the ribbon tweeter), and may blow up itself and/or the tweeter, despite any fuse protection.
Most transistor power amps have high negative feedback that forces the output to be at a certain voltage. When the amp sees a short to ground for DC, it has a tug-of-war, and can blow up. If the amp has a transformer coupled output (virtually all tube amps), there's no problem, since that will block DC. If there's a resistor in series with the tweeter that is over 4 ohms, then no problem.
More typically, the amp will connect directly to the driver, so you need to put a cap in series with the ribbon tweeter that is at least 10X the value that would give you the correct crossover frequency if the crossover was passive. If 4uF would have given you the crossover frequency you wanted in a passive crossover, you would want to put a 40uF non-polarized cap in series with a ribbon when the crossover is "active" (ahead of the power amp) and the amp is to be connected directly to the tweeter.
C = 1/(2 X pie X Frequency (of rolloff) X resistance and driver impedance as viewed by the cap).
The resistance that needs to be added to the driver impedance is for the case where the tweeter is more efficient than the woofer, so needs a series resistor to reduce it's output a bit. If you're new at this, I wouldn't try to do a 2 pole or more passive crossover. Too hard to get it right. With X = 7kHZ or above, one pole should work fine unless you want it to run extremely loud.
If the crossover is active, implying that the tweeter will be connected directly to the output of a power amp, there's a different situation. Ribbon tweeters have matching transformers inside of them, since the ribbon itself is less than one ohm. At tweeter frequencies the power amp will see the impedance rating of the tweeter (8 ohms for example). At DC the power amp will see a short circuit of less than an ohm (the primary winding of the matching transformer inside the ribbon tweeter), and may blow up itself and/or the tweeter, despite any fuse protection.
Most transistor power amps have high negative feedback that forces the output to be at a certain voltage. When the amp sees a short to ground for DC, it has a tug-of-war, and can blow up. If the amp has a transformer coupled output (virtually all tube amps), there's no problem, since that will block DC. If there's a resistor in series with the tweeter that is over 4 ohms, then no problem.
More typically, the amp will connect directly to the driver, so you need to put a cap in series with the ribbon tweeter that is at least 10X the value that would give you the correct crossover frequency if the crossover was passive. If 4uF would have given you the crossover frequency you wanted in a passive crossover, you would want to put a 40uF non-polarized cap in series with a ribbon when the crossover is "active" (ahead of the power amp) and the amp is to be connected directly to the tweeter.
- Status
- Not open for further replies.