Forte Passive Radiator

[Jamey]

Just got my fortes out of storage. Plan on using them in my new home theater as the Front Speakers of a 7.1 system. I bought them in 1987, they are the original Forte. I need to either get two new or used 12" Passive Radiators or get the one's I got fixed. Both of the cones are sucked in, and are ripping away from the back of the enclosure. Any Ideas?

[RichardP]

<>A similar question was posted about two weeks ago. Here is the

thread:

http://forums.klipsch.com/forums/thread/907203.aspx

[djk]

The 12" model from Parts Express is pretty much a drop-in replacement. If you need the 15" one, the mass may need to be adjusted.

[bodcaw boy]

We make kd13 drones for the forte 1.

Blessed be your day,

Roy

[bhendrix]

Hi Roy,

Do you have any KD-14's (or equivalent) for the KP-320's? One of these out of the church in Texas doesn't appear to be OEM. It has a different foam surround.

[bodcaw boy]

Yep. We sure do.

Blessed be your day,

Roy

[bhendrix]

Thanks, Roy. Is there a schematic available for the KP-320 crossover?

[bodcaw boy]

yep there is. now if you only knew someone at klipsch? hmmmmmm. toughy....

have a blessed night bill,

roy

[Jamey]

I thought the forte 1 took the kd12 passive radiator. What size is the kd13 and will it work?

[vandyman]

Roy,

I am very interested in the KD-13 drone from Klipsch, if they are again making it. What is the availability and cost of the unit. I have some Fortes with some rough KD-13's in the back, that need some help. Thanks for the news.

Vandyman

[Rivendell61]

Very good news. I could use a pair. Thought they were no more.

Just a thought....if new drones are on hand.....would it be because a Forte III is forthcoming? Oh boy! That I would buy in a flash--

Mark

[seti]

How exactly does a passive radiator work? I know that one incarnation of the Jubilee had it but not sure how it really works......

[bodcaw boy]

I thought the forte 1 took the kd12 passive radiator. What size is the kd13 and will it work?

it's been awhile but i believe the kd-12 is used in the kg-4 while the kd-13 is the drone used in the forte i and quartet. the kd-13 is a 12" drone. we make both.

have a blessed night,

roy

[bodcaw boy]

Roy,

I am very interested in the KD-13 drone from Klipsch, if they are again making it. What is the availability and cost of the unit. I have some Fortes with some rough KD-13's in the back, that need some help. Thanks for the news.

Vandyman

call customer service and they should be able to tell you. or you might call colter.

have a blessed night,

roy

[seti]

How exactly does a passive radiator work? I know that one incarnation of the Jubilee had it but not sure how it really works......

I am getting passive radiator and drone mixed up....Jubilee had drone and forte had passive radiator lol bit of a difference.....

[WMcD]

I'm quite sure that drone and passive are terms for the same thing.

The drone is just a diaphragm with no voice coil. But it does have mass and spring and a large radiating area.

Other than those items, it act a lot like the mass of air in a port, in a ported design.

The "other" though makes it superior to or at least different from a port. One thing is that the diaphragm is bigger than most all ports. It can lead to the use of a smaller box.

I have a book by Prof. Leach which has a page or two on the technical points of use of a passive drone. If anyone is interested, let me know.

It is my understanding that the port and drone both act as filters and are effecitive over a narrow range of frequencies. In the critical range, I believe they reverse phase. In discussion we have to be careful about phase. Remember that the box and anything communicating with it is being driven by the back of the main, active driver. The back of the main driver is always in inverted polarity, or 180 degrees phase from the front at all frequencies. One side pushes while the other pulls as referenced to the magnet or basket, just by geometry.

In the range where the port or passive is working as we want them, the main driver moves out from the box, and so does the passive or the air in the port, move out from the box.

This would be phase reversal if you consider that the passive or the port is being driven by the back of the main . You'd expect that outward movement of the main driver would suck in the passive or slug of air in the port, and vice versa. They certainly do that at zero Hertz or d.c. We see the obvious effect when we check for the air tight seal of the box by pushing "in" on the active and watch the passive move "out".

Of course this phase reversal (in the active frequency region) is good because now we have two diaphragms acting in unison. The back of the active driver is reversed from the front and then the passive goes though a 180 degree reversal in the important region. Over a range, things work as if you had two active drivers in phase.

It looks to me that at some point in frequency, with the use of the passive, that 180 degree shift is lost and then the passive's motion does follow that of the back of the active. Then we get a notch (dip) in acoustic output. That notch comes about because the active moves out and the passive moves in. This occurs at above zero Hertz because the passive has its own spring. But this is at a frequency below where we get the wanted boost from two diaphragms moving. I.e. the system has to be designed to get that notch down to about 20 Hz or so.

Gil

[JoeRiff]

William,

Very interesting read. Thanks for the info.

[vandyman]

Gil

I would love to see this information on the speaker drivers. I am going to make a center channel using a Forte for the model. I had intended to put both the passive and active drivers on the front of the speaker. I had thought that by placing the drivers on the same surface the drivers would be out of phase at some frequency. How this would affect the sound, I don't know. I should look into this before I start my projects, and come up with some designs that will work sonically. I will send you a pm about this.

Thanks,

Vandyman

[seti]

I'm quite sure that drone and passive are terms for the same thing.

The drone is just a diaphragm with no voice coil.  But it does have mass and spring and a large radiating area.

Other than those items, it act a lot like the mass of air in a port, in a ported design.  

The "other" though makes it superior to or at least different from a port.  One thing is that the diaphragm is bigger than most all ports.  It can lead to the use of a smaller box.

I have a book by Prof. Leach which has a page or two on the technical points of use of a passive drone.   If anyone is interested, let me know.

It is my understanding that the port and drone both act as filters and are effecitive over a narrow range of frequencies.  In the critical range, I believe they reverse phase.  In discussion we have to be careful about phase.  Remember that the box and anything communicating with it is being driven by the back of the main, active driver.  The back of the main driver is always in inverted polarity, or 180 degrees phase from the front at all frequencies. One side pushes while the other pulls as referenced to the magnet or basket, just by geometry.

In the range where the port or passive is working as we want them, the main driver moves out from the box, and so does the passive or the air in the port, move out from the box. 

This would be phase reversal if you consider that the passive or the port is being driven by the back of the main . You'd expect that outward movement of the main driver would suck in the passive or slug of air in the port, and vice versa. They certainly do that at zero Hertz or d.c.   We see the obvious effect when we check for the air tight seal of the box by pushing "in" on the active and watch the passive move "out".  

Of course this phase reversal (in the active frequency region) is good because now we have two diaphragms acting in unison.  The back of the active driver is reversed from the front and then the passive goes though a 180 degree reversal in the important region.  Over a range, things work as if you had two active drivers in phase.

It looks to me that at some point in frequency, with the use of the passive, that 180 degree shift is lost and then the passive's motion does follow that of the back of the active. Then we get a notch (dip) in acoustic output.  That notch comes about because the active moves out and the passive moves in.  This occurs at above zero Hertz because the passive has its own spring.  But this is at a frequency below where we get the wanted boost from two diaphragms moving.  I.e. the system has to be designed to get that notch down to about 20 Hz or so.

Gil

Very interesting thank you for the explanation. I had to read it a few times..... Very cool. I would be interested in the Prof. Leach article.

[DrWho]

A drone and passive radiator are the same thing. As far as function, passive radiators behave like ports. In fact, you can replace any port with a passive radiator and you can also replace any passive radiator with a port. They're all functionally the same.