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Kris

Why is Frequency Response of RP-150M Better Than RP-450C ?

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Why is the frequency response of the RP-150M better than the RP-450C ? Based on the cabinet size and number of woofers, it seems that the RP-450C should have the better/lower frequency response but it does not. Why ? 

 

RP-150M: 

Frequency Response: 48-25kHz +/- 3dB
Dimensions: 14.57” (37.0 cm) x 7.67” (19.5 cm) x 10.67” (27.1 cm)
Volume: 1192 cubic-inch
Power: 75W/300W
Woofers: 1 x 5.25" 
Enclosure Type:  Bass Reflex

 

RP-450C: 
Frequency Response: 58-25kHz +/- 3dB
Dimensions: 6.81 “ (17.3 cm)x 31.13” (79.1 cm) x 14.51” (36.8 cm)
Volume: 3076 cubic-inch
Power: 150W/600W
Woofers: 4 x 5.25" 
Enclosure Type:  Bass Reflex

 

Kris

 

 

 

 

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My guess is that it is engineered and tuned to optimize dialog in movies.

 

https://en.wikipedia.org/wiki/Voice_frequency

 

The voiced speech of a typical adult male will have a fundamental frequency from 85 to 180 Hz, and that of a typical adult female from 165 to 255 Hz. Thus, the fundamental frequency of most speech falls below the bottom of the "voice frequency" band as defined above.

 

Bill

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My guess is that the sensitivity difference between the speakers is responsible.

The RP-150M has a sensitivity of 93dB/1m and the RP-450c has a sensitivity of 97dB/1m i.e 4 dB higher with the same model of woofers (and tweeters)

To achieve that increased sensitivity with the RP-450c the loudspeaker must be tuned to a higher frequency.

 

Jef

Edited by JefDC

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The center channel is still a full range channel and the center speaker ideally would be full-range and flat across entire frequency range. There should be no boosting of voice bands by speaker since the center channel provides more than just voice. The RP-250F has size and sensitivity close to RP-450C yet its frequency response is 35-25kHz. If the RP-450C had a similar low-end frequency response that would be great as I want my center to be full-range and matching my left/right speakers. I am starting to wonder if the RP-450C has high-pass filter as the RP-450C, RP-250C, and RP-440C all have lower end of frequency response within 2 Hz of each other. Does anyone know if they use high/band-pass filter for center channel woofers ? 

 

RP-250C: 60-25kHz +/- 3dB

RP-440C: 59-25kHz +/- 3dB

RP-450C: 58-25kHz +/- 3dB

RC-64 III: 57-24kHz +/- 3dB

 

RP-250F: 
Frequency Response: 35-25kHz +/- 3dB
Sensitivity: 96dB @ 2.83V / 1m
Dimensions: 36.10” (91.7 cm) x 7.87” (20.0 cm) x 14.82” (37.7 cm)
Volume: 4210 cubic-inch
Power: 100W/400W
Woofers: 2 x 5.25" 
Enclosure Type:  Bass Reflex

 

Kris

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Kris,

compared to the RP-250F I see the following differences:

Volume: 4210ci versus 3076ci = 36% more - that is not really 'close' and not taking into account that the 450C has 2 woofers more which take up more internal volume as well.

Power: the RP-250F maximum allowed peak power is 400W versus 600W for the 450c = 33% less 

and the sensitivity is a moderate 1 dB lower.

 

All this combined explains - to me - why the RP-250F is capable of a lower frequency of 35Hz versus the 58Hz of the 450C.

 

2 Woofers of the 4 have Band-Pass filter of 500Hz-1500Hz (see picture )

the 2 other Woofers have a Low Pass filter up to 500Hz

So basically - no the Center speaker does not have a filter that limits it's lowest frequency - that is a result of the tuning of the cabinet.

 

 

Jef

Klipsch-Reference-Premiere-RP-450C.thumb.jpg.abc065694e468724805f6fbd820277fa.jpg

Edited by JefDC
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9 hours ago, Kris said:

Why is the frequency response of the RP-150M better than the RP-450C ? Based on the cabinet size and number of woofers,

 

it seems that the RP-450C should have the better/lower frequency response but it does not. Why ? 

A more descriptive word than "better" would be "lower."  The RP150M digs deeper than the RP-450C.

 

The answer to "why" the RF-450C doesn't play as low is because it was designed that way.  Obviously I am not a speaker engineer but I would hazard a pretty safe guess that you don't want deep bass being produced by the center channel.  That would allow more power to be devoted to mid-range drivers for clarity and articulation.  Let the mains and the sub produce deep bass.

 

That last chart posted by @JefDC directly upstream ^^^ shows the RP-450C is not really a two-way as I thought, but a three-way design.  Interesting.

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3 minutes ago, wvu80 said:

 

 

That last chart posted by @JefDC directly upstream ^^^ shows the RP-450C is not really a two-way as I thought, but a three-way design.  Interesting.

I thought it was a 2.5 way with all 4 woofers operating until it crosses to only 2 woofers and then to the tweeter/horn.  I know the RC-64 operates in that way.

 

Bill

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2 minutes ago, willland said:

I thought it was a 2.5 way with all 4 woofers operating until it crosses to only 2 woofers and then to the tweeter/horn.  I know the RC-64 operates in that way.

 

I was being brief in my post, but yes, I thought 2.5 way was the design with the outer two woofers having a slightly different XO to prevent lobing.

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I ran Audyssey calibration on the RP-250C and RP-450C with no subwoofer present:

 

RP-250C: Audyssey calibrates to small speaker with crossover of 40Hz.
RP-450C: Audyssey calibrates to full range speaker. 

 

This is an unexpected result based on the Klipsch datasheet frequency response specs:

 

RP-250C: Frequency Response: 60-25kHz +/- 3dB
RP-450C: Frequency Response: 58-25kHz +/- 3dB

 

I need Klipsch to provide their SPL plots for each speaker so I can properly design/chose my system.

 

Also interesting is that Klipsch has spec'ed the 440WC wireless center channel with lower frequency range than the passive 440C.

 

RP-440WC: Frequency Response: 48-25kHz
RP-440C: Frequency Response: 59-25kHz +/- 3dB

 

Kris

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On 9/26/2018 at 9:45 AM, Kris said:

The center channel is still a full range channel and the center speaker ideally would be full-range and flat across entire frequency range.

Bah, Humbug, in the era of modern HT.  Modern systems are designed to have speakers of varying sensitivities and frequency responses.  It assume that the system has a subwoofer/s to handle the lower frequencies.  There is no benefit to have all the speakers of the same size or frequency response since this can be handle by a good avr/DSP program.  By virtue of the various speakers locations in the room, the frequency response of the  same size speakers in an HT will be different even if identical speakers are used.  Trying to match the variou speaker in the low end is of no benefit.

 

If you are into HT, it is paramount to get a good avr or avp/amp to blend every speakers. You can't use one parameter to figure out the optimum setup.  Audio engineers put in a lot of R&D in developing a center channel.  I run an RF 7 system and just set all the speakers to small and take full advantage of the avr's DSP.  More full range speakers in the HT usually means more problems with bass management and reverb.

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On 10/7/2018 at 12:03 PM, Kris said:

I ran Audyssey calibration on the RP-250C and RP-450C with no subwoofer present:

 

RP-250C: Audyssey calibrates to small speaker with crossover of 40Hz.
RP-450C: Audyssey calibrates to full range speaker. 

 

This is an unexpected result based on the Klipsch datasheet frequency response specs:

 

RP-250C: Frequency Response: 60-25kHz +/- 3dB
RP-450C: Frequency Response: 58-25kHz +/- 3dB

 

I need Klipsch to provide their SPL plots for each speaker so I can properly design/chose my system.

 

Also interesting is that Klipsch has spec'ed the 440WC wireless center channel with lower frequency range than the passive 440C.

 

RP-440WC: Frequency Response: 48-25kHz
RP-440C: Frequency Response: 59-25kHz +/- 3dB

 

Kris

The klipsch response is as posted in their specs.  Many have charts available done by individuals that did it on their own. 

 

You cannot design your room to Klipsch specs...you select your speakers based upon your room!  Very important difference.  

 

Response is a factor of the room....walls treatment furniture size shape materials etc.

 

For example my rp160ms play down to 30hz on my walls, yet are not "designed" to do so.

 

Designs take into account how and where most users will use a speaker.  I've told people 50x here to get an rp250c....because it's just fine.  450c has specific applications where it helps or hurts more.  But all work in most situations and often klipsch suggests A is for smaller rooms B for medium and C for larger.

 

In doing so their goal is higher sensitivity to provide higher spl at a given power input.  I.e. bigger rooms need more spl...and designers assume few people have bigger more powerful avrs in those rooms.

 

Generally speaking a larger enclosure allows for deeper frequencies assuming the SAME number of drivers....i.e. a 2cft box with 1 woofer will play lower than a 1cft box with that same woofer.  2 woofers means 2x the volume for the same frequency range. So 4 woofers in a box roughly 2x a box with 2 woofers will have similar response but more spl capability.  In this case it is partially mitigated by their desire to also design for less lobing vs pure SPL.  

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