6 replies to this topic

[ChrisinNH]

Hi, I've joined the group, and am having a great time learning about my speakers. I found the site after opening up a pair of old KLH 17s and I wanted to know what made them work. I pulled out the crossover circuit and rearranged everything on my kitchen table.

I will go ahead and try to replace everything, as you have described, before putting it all back in the cabinets. But I regret to admit I'm clueless with regards to electronics. It seems like a fairly simple circuit of wires and components, but I wonder where I can go to learn how it all works.

I can swap out the parts with a solder gun, I think. But I don't understand resistors and capacitors and the three way switch. Is there a page or a place I can go to get a crash course on how this thing turns an electrical signal from an amplifier into sound??
Thanks so much,
Chris

Chris Mills
Keene, NH

[Carlspeak]

Hi Chris & welcome aboard!

I know of no post that deals exclusively with the crossover workings of the KLH-17.

OTOH, here is a link to an animated crossover that may be of help (click on #8). You may have to watch it a few times to get the gist of it. There's no attenuation switch in the simulation like on the 17. However, what that switch does is put into service the various resistors that have different values.

http://wn.com/electr...lab_simulation#

[soundminded]

Hi, I've joined the group, and am having a great time learning about my speakers. I found the site after opening up a pair of old KLH 17s and I wanted to know what made them work. I pulled out the crossover circuit and rearranged everything on my kitchen table.

I will go ahead and try to replace everything, as you have described, before putting it all back in the cabinets. But I regret to admit I'm clueless with regards to electronics. It seems like a fairly simple circuit of wires and components, but I wonder where I can go to learn how it all works.

I can swap out the parts with a solder gun, I think. But I don't understand resistors and capacitors and the three way switch. Is there a page or a place I can go to get a crash course on how this thing turns an electrical signal from an amplifier into sound??
Thanks so much,
Chris

Chris Mills
Keene, NH

The electronic components inside the box are simple frequency filters. The 2 speaker elements, the larger woofer and smaller tweeter each perform a different function best. The woofer works well at low frequencies, the tweeter at higher frequencies. The filters act to separate the incoming electrical signals into different frequency bands and to direct each to the appropriate speaker driver. If low frequencies reached the small speaker, the tweeter, it would cause distortion and damage it. If high frequencies reach the large woofer, it could also cause distortion. The level switch adjusts the relative loudness of the tweeter compared to the woofer. It acts something like a treble control on an amplifier except its precise action is somewhat different.

There are many theories about how to design a crossover filter network. There are many textbook designs and there is a well established system of mathematical equations for calculating how they will behave. But in the real world, most products are the result of experimentation by the speaker designer. Trial and error arrive at designs the designer feels sound or measure best to him in light of his concept or how much the speaker will cost. In today's market, most speakers do not have a level control to adjust the relative loudness of the different drivers to each other the way your KLH Model 17 and many other speakers of that era do.

[ChrisinNH]

The electronic components inside the box are simple frequency filters. The 2 speaker elements, the larger woofer and smaller tweeter each perform a different function best. The woofer works well at low frequencies, the tweeter at higher frequencies. The filters act to separate the incoming electrical signals into different frequency bands and to direct each to the appropriate speaker driver. If low frequencies reached the small speaker, the tweeter, it would cause distortion and damage it. If high frequencies reach the large woofer, it could also cause distortion. The level switch adjusts the relative loudness of the tweeter compared to the woofer. It acts something like a treble control on an amplifier except its precise action is somewhat different.

There are many theories about how to design a crossover filter network. There are many textbook designs and there is a well established system of mathematical equations for calculating how they will behave. But in the real world, most products are the result of experimentation by the speaker designer. Trial and error arrive at designs the designer feels sound or measure best to him in light of his concept or how much the speaker will cost. In today's market, most speakers do not have a level control to adjust the relative loudness of the different drivers to each other the way your KLH Model 17 and many other speakers of that era do.

I find it kind of fascinating, kind of mysterious, that those 2 thin wires can provide both the electrical energy/current to power the speaker horns, as well as the entire sound spectrum simultaneously. Am I odd, or does this strike anyone else as somewhat incredible?

In the 17's circuit, the woofer gets the live wire and the ground wire directly from the posts on the back of the speaker - unfiltered. The path to the tweeter is through the three way switch. But it's not that straight forward. There are numerous components - I assume they are resistors or capacitors, and the different paths the current can take don't seem to make sense. I will try and post a picture of it and maybe figure out what they were thinking when they constructed it.

[JKent]

Hi and welcome
It DOES seem a bit like magic. Some members here are electrical engineers and the like, and they understand it. Others of us (like me) just follow along by rote. I'm sure you can learn the "how" if you are motivated.
In the meantime, here is a schematic that may help, and a photo of a 17 (or 20--they're the same) crossover. The photo of the original crossover shows resistors (tan rectangular blocks) and capacitors (black and red tubular thingies). Notice one cap has exploded! The new components are shown in the other photo--black and yellow film caps and new white resistors. The specific brands are not important. Just be aware that some of the original caps are "dual value", a single tube may have 3 wires coming out of it. It gets replaced with 2 new caps.
Just ask if you have any questions.
Kent

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[oiseaux]

Chris n NH,
If it helps you visualize what goes on in a crossover network for a KLH model Seventeen or any similar two-way speaker system try thinking of it in terms of a mixing water faucet.
Water faucet:
You want water output available to you at a certain temperature, say 90 degrees F.
Source - water incoming at 55 F.
One branch of cold water goes through valve limiting the flow to 35%.
Other branch of incoming hot water (120 F.) goes through valve limiting flow to 65%.
Both are combined into the output of the faucet and, voila, you have water at the resultant temperature.
If you want the resultant temperature different, you would change the flow of one or both valves.

A coil in series with a speaker (woofer) lets the lower frequencies pass and impedes the higher frequencies.
A capacitor in series with a speaker (tweeter) lets the higher frequencies pass and impedes the lower frequencies.
This allows each speaker to operate with the group of frequencies that it does best.
Resistors are added where needed to reduce the flow of energy to one or more of the individual speakers,ie.,reduce the high's.
The art and the science of speaker design is in the design of each speaker and selecting the components of a crossover that allow each to share the workload and create a transducer that changes the electronic output from your amplifier to sound, hopefully of a pleasing balance, of your music.

Hope this helps a little. Cheers!

[Horswispr]

There's a schamatic for the crossover of the KLH 6 here on Classic Speaker Pages. I believe the KLH 6 and KLH 17 had very similar crossovers. You should (I think) find a "coil" on the way to the woofer, rolling off signal at the top of the woofer's range (or maybe that's only in the KLH 6). The 8 mfd capacitor on the way to the tweeter rolls off signal at the bottom of the tweeter's range. Things get more complicated on the crossover board, where the resistors and two more capacitors (2 mfd each, I think) are a part of the 3-position tweeter level switch. I can stare at the KLH 6 schematic and sometimes almost have it figured out before my eyes start to water and my brain shuts down.