Two Crossover Frequencies in Center Channel Speaker Spec - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 9 Old 06-12-2019, 03:51 PM - Thread Starter
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Question Two Crossover Frequencies in Center Channel Speaker Spec

I am starting to put together my first home theater and came across something I don't understand in some of the Klipsch center channel speaker specs. They are listing 2 crossover frequencies with only two speaker sizes in an enclosure, a woofer and a tweeter. For example:

RC-64 III: 1,000 Hz & 1,400 Hz
RP-504 or 404C: 500Hz/1500Hz

If these boxes had an WMTW or WMTMW configuration, I would understand that they are switching between woofers and mid-range, then between mid-range and tweeter. However, the above enclosures only have two speaker sizes, 6 in + tweeter in the 64, 5 in + tweeter in the 504, and 4 in + tweeter in the 404. Obviously, they have four woofers in each box. So, are they driving one pair as "woofers" and another pair as "mids"? How does that work when the "woofers" and "mids" are the same size? Also, the "mid" frequency range seems really narrow, especially in the RC-64...

Can someone explain what they are doing here?

Thank you!
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post #2 of 9 Old 06-12-2019, 04:05 PM
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Care to provide links to the speakers, so we can see what they look like and examine the specs?

I can look them up ... but so can you.

Steve/bluewizard
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post #3 of 9 Old 06-12-2019, 04:13 PM
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Quote:
Originally Posted by makke View Post
I am starting to put together my first home theater and came across something I don't understand in some of the Klipsch center channel speaker specs. They are listing 2 crossover frequencies with only two speaker sizes in an enclosure, a woofer and a tweeter. For example:

RC-64 III: 1,000 Hz & 1,400 Hz
RP-504 or 404C: 500Hz/1500Hz

If these boxes had an WMTW or WMTMW configuration, I would understand that they are switching between woofers and mid-range, then between mid-range and tweeter. However, the above enclosures only have two speaker sizes, 6 in + tweeter in the 64, 5 in + tweeter in the 504, and 4 in + tweeter in the 404. Obviously, they have four woofers in each box. So, are they driving one pair as "woofers" and another pair as "mids"? How does that work when the "woofers" and "mids" are the same size? Also, the "mid" frequency range seems really narrow, especially in the RC-64...

Can someone explain what they are doing here?

Thank you!
Nice!
The outer woofers are attenuated at different frequencies...something to do with the problems associated with horizontal design of center channel speakers.

Espo77's living room equipment: RECEIVER: Yamaha RX-A3030- SPEAKERS: Boston Acoustics M350, M25 center, surrounds, and front heights-
BLU-RAY: Oppo BDP103D- SUBWOOFER: HSU VTF-15H MK2- dedicated circuits for A/V- TV: Vizio P55C-1
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post #4 of 9 Old 06-12-2019, 04:25 PM
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Quote:
Originally Posted by Espo77 View Post
Nice!
The outer woofers are attenuated at different frequencies...something to do with the problems associated with horizontal design of center channel speakers.
To prevent Lobing, which is common in a sideways MTM speaker, they run the Bass Drivers at different frequencies. Likely they are some variation of 2.5-Way speakers, where below a certain frequency Both Bass Driver are engaged, above the first crossover, only one Bass Driver is working. This helps prevent drop outs to the size or lobing.

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post #5 of 9 Old 06-12-2019, 05:42 PM
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[QUOTE=bluewizard;58174692]To prevent Lobing

I’ve heard of “left lobing” before. A lady in a nightclub once did that to me...

Espo77's living room equipment: RECEIVER: Yamaha RX-A3030- SPEAKERS: Boston Acoustics M350, M25 center, surrounds, and front heights-
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post #6 of 9 Old 06-12-2019, 05:49 PM
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It prevents lobing effects due to having multiple drivers on the same horizontal plane.

You would get a lot of cancellation if they didn’t attenuate them and would be a very poor center channel.

Leave it at 8 ohms and call it a day :)
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post #7 of 9 Old 06-12-2019, 07:18 PM
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Originally Posted by Russdawg1 View Post
It prevents lobing effects due to having multiple drivers on the same horizontal plane.

You would get a lot of cancellation if they didn’t attenuate them and would be a very poor center channel.
The lobes tend to be off to the side, so if you are generally in the Center you won't notice it, but someone sitting off to the side could be in a dead zone (sort of dead).

This is illustrates what we mean by lobing. You see that the response has three lobes and two dead zones.

https://www.rane.com/png/n160fig2.png

Lobing in this fashion tends to occur at frequencies related to the distance between the Bass Drivers, but only when the speaker is horizontal. The lobes are still there when place vertical but they are at the ceiling and the floor, so they don't really matter.

If you determine the frequency where lobbing is strongest, then you can set the 2.5-way crossover below that frequency and the problem is solved. At what would have been the lobing frequency, both speakers are not playing so lobing doesn't occur.

Steve/bluewizard
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post #8 of 9 Old 06-12-2019, 07:21 PM
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Quote:
Originally Posted by bluewizard View Post
The lobes tend to be off to the side, so if you are generally in the Center you won't notice it, but someone sitting off to the side could be in a dead zone (sort of dead).

This is illustrates what we mean by lobing. You see that the response has three lobes and two dead zones.

https://www.rane.com/png/n160fig2.png

Lobing in this fashion tends to occur at frequencies related to the distance between the Bass Driver, but only when the speaker is horizontal. The lobes are still there when place vertical but they are at the ceiling and the floor, so they don't really matter.

If you determine the frequency where lobbing is strongest, then you can set the 2.5-way crossover below that frequency and the problem is solved. At what would have been the lobing frequency, both speakers are not playing so lobing doesn't occur.

Steve/bluewizard

Should have mentioned that in my post, but thank you for the clarification. I’m sure the OP will appreciate that.

Leave it at 8 ohms and call it a day :)
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post #9 of 9 Old 06-13-2019, 05:50 AM - Thread Starter
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Thank you all, especially bluewizard, for the explanations. Much appreciated!
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