Double binding post-High and Low filter question???

[derrickdj1]

Speakers with two sets of binding posts: they usually come with removable, external jumpers shorting the high/low post pairs. Internally, there's typically a high pass filter between the tweeters and the high posts, and a low pass filter between the woofer and the woofer posts. The only connection between the two sections comes from the external jumpers. So you can remove the external jumpers and bi-amp in a way that's perfectly safe for the drivers. Would this be true for Klipsch reference line?

[djk]

Try bi-wiring first, that's what the extra terminals are for.

[derrickdj1]

This is a knowledge question. Are there filters for high and low and without the binding straps, the high and low terminals are completely independent?

The typical crossover unit from a loudspeaker: The frequency is divided up by inductors and capacitors and then sent on to the woofer, tweeter and mid-range driver.

This speaker has only only one set of binding post.

[JBryan]

As djk said, the double binding posts are for bi-wiring, not bi-amping. To bi-amp, you'd need to either run identical amps to the top and bottom terminals or bypass the internal xover and have an external one to adjust the gain to each driver.

[pzannucci]

I believe what djk is stating is that when you remove the straps, most people will bi-wire to a single amp.

You can remove the staps since each of the high and low filters are separated - the high filter is on the top posts, the low filter is on the bottom posts. It is safe to bi-amplifiy once the straps are removed. The problem with doing this is that there usually is not much to gain (if any) in the quality of the sound by doing a bi-amp using the internal speaker crossovers. It just adds complexity.

[derrickdj1]

Thanks for the responses, I am not interest in bi-wiring/bi-amping and I am familar with the concept of using an active XO. My question was concerning the xo design. It seems like the concensus is that there are filters for the Hi and Low terminals. After reading on xo's, there was not much discussion the filters. There are various xo designs and I did not Know which type the reference speakers had. This is audio school 101 for me.[]

[pzannucci]

If a manufacturer is going to put two or three binding posts on a speaker for home, if there are binding straps across those posts and they can be removed for bi-wire or bi-amp, it would be a reasonable assumption that each of the high, low, (medium) portions of the network are separated.

With some speakers such as old Frazier speakers, they used to do more of a series network where you could not separate the two portions of the network.

Reference this web page http://en.wikipedia.org/wiki/File:Series_parallel_xover.GIF

Frazier used to put the inductor across the high/mid frequency and capacitors across the low frequency making a series configuration which could not be bi-amped or bi-wired.

[WMcD]

Perhaps I can answer some questions.

1) Generally, there is a high pass filter for the treble and a low pass filter for the bass. The steepness of the filter depends on the "order" which is generally the number of inductors (L) and © in the design. Very generally each is worth 6 dB of roll off per octave (doubling of freq is an octave just like eight whole notes higher in music is doubling in frequency)

2) It should be stated that the speaker drivers have their own roll off in acoustic output. You often see some theoretic graphs showing the outputs of crossovers but thesre don’t show the actual acoustic outputs of the individual drivers.

3) The voice coil inductance in the woofer serves as its inherent low pass electrical filter. But we still want to turn it off at high freqs, often before the voice coil inductance will do this. We often want to turn off the woofer way before it has any high freq acoustic output because we want the woofer and the treble sounding (overlapping) at the same freqs.

4) We definitely want to keep low freqs out to the treble driver. If low freq electrical power gets to it,the treble driver will be blown out.

5) The modern design is a parallel input to the filter inputs; both are connected to the amp. As shown in the wiki. where there are no split inputs shown. In theory, the amp has a very low output impedance which means that there is no interaction between the inputs to the two or more filters driving the drivers..

6) If there are two input terminals, one is connected to the low pass for the woofer and one is connected to the treble. As far as I can tell in such designs, the ground or black terminals are not connected internally. So the strap provides that, if present.

7) We can take a look at an RF-7 here:

http://forums.klipsch.com/forums/p/60039/588209.aspx#588209

While the author did not show it, it is fairly implied that once the strap is removed there is no connection between the ground of the two filter or drivers.

8) It shows that the otherwise simple / clasic design of can be augmented by what is sometimes called Zobels of additional R or L or C in combinations to tailor the output to the speaker components, further. (Originally, Zobels were used to just compensate electrical impedances, but now they are used to alter the electrical signal delivered to the driver. Actually, classic crossovers work keep some freqs from getting through, but a mirror image of the concept is that they don't absorb the freqs at the input to the filter. Long story.)

9) The LF in the link would be a simple first order filter with an inductor connected between the input and the woofer. But we also see an RC series across (parallel) with the woofer. Therefore this RC is an additional load (increasing load with freq, or decreasing impedance) on the output of the simple low pass filter. So it is drawing off some of the power which would otherwise go to the woofer at higher freqs. .

10) The HF section is more complicated. Let's proceed from the (+) input. First we see a 1 ohm resistor which causes a voltage drop, a bit, cutting down on the signal passed or absorbed, depending on how you look at it.

Then we see a typical third order "T" type high pass with two caps and one inductor. This basically means that at the crossover freq, it rolls off the freqs passed though at 18 dB per octave as we go down in frequency. (Or rolls up 18 dB per octave as we go up. Smile.) This pretty much keeps low freqs out of the treble driver in a substantial degree.

But then we see something else in the diagram around the bottom of the diagram. It is a series R-L-C in parallel with the driver -- sort of an additional load on the output of the T filter. The R-C series has a sharp dip (notch) in impedance and becomes a short circuit to ground at its resonance freq -- but the R increases and broadens the dip in impedance.

I haven’t done the math to determine the center of band or how wide it is for the RLC. But apparently the treble driver has some sort of peak in acoustic output over some band. This circuit draws off some power delivered to the driver over the band.

11) It is worthwhile to discuss these "Zobels" a bit more. In both cases (LF and HF) they are absorbing power which would otherwise be going to the driver inputs by introducing an additional load. In one way of thinking they are not filtering out freqs, but rather diverting them the the resistors which are part of their circuits. Their role is to allow tailoring of the electrical energy received by the driver.

12) You may ask how to determine how the extra Zobels should be used. This is only possible with a sophisticated computer program such as Linear X. There is an on line paper concerning the Palladium crossover design which provides an illustration but not the operation of the computer analysis.

WMcD

[derrickdj1]

A sincere thank you to W.F.Gil McDermott, maybe I ask to many questions, but I enjoy the theory behind the speakers design as much as I enjoy listening to my speakers. After reading your synopsis, I see why people often refer to the Low Pass filter as a high cut or trebble filter. It is difficult to get schematics of the Klipsch speakers, which is what I was looking for on the net. There is a lot of thought put into the design of these passive xo's. One of the things behind my question was how the Dean G mod made the sound different than the original RF 7 xo and what frequency would be cut or made more prominent. Also what changes in the slopes of the xo are in his modification. Thanks for reading into my question on a little deeper level.