THSR-2 Crossover

[BEC]

I have never seen a schematic for this theater Heresy 2-way crossover, so I sort of made one.

Bob Crites

[BEC]

Here is what that crossover looks like on the spectrum analyzer.

Bob Crites

[BEC]

The owner wants a tweeter filter for a K-76 added. I just don't see that working right to just add the filter like the Heresy II has. Looks like this thing is really optomized for vocals perhaps.

Bob Crites

[Deang]

What drivers does it use -- does it use a K-700 horn?

[BEC]

K53K plastic and K-22 woofer. Has a cutout for a K-76 tweet.

Bob

[Deang]

So, once he drops the tweeter in -- he basically has a HII. I guess the HII uses a K-24 woofer, I wonder what the difference is between it and a K-22? I'd be tempted to tell him you can't use the current network and will have to build a HII network from scratch.

[BEC]

Building a new H2 network woud be easy, but will cost him more since not a single part would be usable from this THSR-2 network.

I don't think, from what I can see, that things would match up right just adding a H2 tweeter filter. Notice the roll off of the midrange at 4 khz and how pronounced the woofer is. I have trouble seeing how that combination is going to make good full range music.

Bob

[Deang]

It will cost him more, but it will be done right and sound great. I'm curious about that K-24 though -- hopefully DCR and Le are the same as the K-22.

[BEC]

It will cost him more, but it will be done right and sound great. I'm curious about that K-24 though -- hopefully DCR and Le are the same as the K-22.

Dean,

Same 2.5 mH woofer inductor are used for the Heresy 1 Type E crossover and for the H2 crossover, so I am guessing that is not a problem.

Bob

[Al Klappenberger]

There is no place to properly connect a tweeter filter to that network. God only knows what it was supposed to be for! Of course, you could just stick one in it like all the rest of the Klipsch networks do! The impedance will be all over the place.

Al K.

[Al Klappenberger]

Here's the woofer channel response assuming an 8 ohm driver with a 1.2 mHy voice coil.

AL K.

[BEC]

Al and Dean,

Thanks for the input. I had pretty much decided that there was no good way to just tack on a tweeter filter to this thing and make it into a full range speaker crossover. I think it needs a real Heresy II network to have a good chance of sounding right.

I can't even really imagine what this thing would sound like as a surround speaker like it was built to be. Why accent the woofer so much and why attenuate the squawker 12 db and roll it off? I am sure it must have done what Klipsch wanted it to do, but I don't understand what they wanted it to do.

Bob Crites

[Marvel]

Bob,

I think (would have to look it up) that the THX spec for surround actually has the highs roll off around 12k. Mike (DrWho) might know for sure since he is getting all that fancy learning in school. []

Bruce

[Deang]

Paging address/speech. Doesn't look good for anything else.

[BEC]

Bob,

I think (would have to look it up) that the THX spec for surround actually has the highs roll off around 12k. Mike (DrWho) might know for sure since he is getting all that fancy learning in school. []

Bruce

Burce,

This thing rolls the highs off at 4k. That is what I am having trouble understanding and they did it on purpose with an inductor and a capacitor.

Like Dean said, might make a good paging speaker.

Bob

[sfogg]

Bruce,

" think (would have to look it up) that the THX spec for surround actually has the highs roll off around 12k."

You might be thinking about the Dolby Surround 7kHz rolloff in the rear channel. I think that speaker is from that era so it was likely built for that sort of use in surround arrays. Hence two way instead of three.

As far as why is the woofer run so much hotter then the top end driver from the crossover.... you are comparing a direct radiator to a horn. The direct radiator isn't going to be as efficient as the horn... you have to feed it more signal....

The additional rolloff on the top end driver might be to acount for a rising response of that driver or it might simply to be a sort of 'x curve' on its response.

Remember this is only an electrical FR of the crossover. Without know the acoustic behavior of the drivers we can't really say what the actual FR of the *system* is.

Shawn

[DrWho]

The THX spec for pro cinema requires that all speakers drop off at 12dB/octave starting at 4kHz, or something around there. I've probably butchered the numbers but the concept is there. The reason for it is because all the upstream equipment is expecting there to be a constant-directivity horn and they are implementing the typical CD EQ - all the time. In the move theatre the idea is to have as even coverage as possible so constant directivity is almost always used.

In the case of the Heresy there is no way that the K700 is CD so the EQ is probably there to compensate for insane on-axis peaks due to beaming. That and the combination of the 7kHz rolloff from the 80's or whenever that was.

[Marvel]

From what Shawn and Mike both say, at least I'm not totally crazy....

... maybe?

Bruce

[BEC]

Here is the FR of the H2 crossovers which drive the same components as the THSR-2. And an added K-76 tweeter.

Bob Crites

[Jim E]

The spec you are refering to is the standard SMPTE ISO 2969 curve used for motion picture theatre alignment. The basic specification calls for a rolloff of 3dB per octave past 2 kHz. The intent for the filter was to help avoid excessive amounts of equalization being used in the surround channels. Typical cinema processors of that era from Dolby, Ultra-Stereo and most other manufacturers used op-amp one third octave eq with about 6 dB of range. Often there is not enough range to reach good settings in the auditorium and dialing in too much eq can introduce phase problems.

JBL also includes a circuit like this in several of their surround speakers as well. Some of the JBL's include a switch to disable the filter if not needed.