External amplify front & center speakers Denon x3700h.

[Golfx]

Good morning. I always try to find answers that will “push” me toward upgrading. You will enjoy upgrading and any new amp purchase. The majority of experts on this website just want you to understand wattage and how it relates to your speaker’s sensitivity. Because you most likely will buy a two channel amp to power your fronts, why don’t you just focus on your front speakers?


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[PENG]

Ok confusion set back in!! I am still a little hung up on the 105w receivers power pushing 9 speakers with the large RF7S 250/1000w rating and hearing that an amp should be 1.5 as powerful as the rms. So I went to the on line calculators and confusion set back in!! What speaker specs do I use for the calculation?? Do I average the totals? Use lowest or highest?? Same question for sensitivities. I have 9 Klipsch speakers, ranging from 4 ceiling @ 50rms/200peak; to the front RF7 @ 250rms/1000peak with sensitivites from 93 to 102? Second question, does it matter much if my theater is a rectangle 15x20 with one side completely open to another 15x20 kitchen vaulted ceiling long ways (all speakers set up in the one side long ways). Listening position is 16.8’ from fronts centered against back wall. Seems like a difficult room but audessy has it sounding pretty good! The atmos effects do come through nicely. cant do much about the living space but can afford some more power if necessary. Again, we watch movies 4/5 times a week and listen at exciting sound levels (svs PB1200pro does handle the low frequencies). I Appreciate that you all are still helping me through this!!

To avoid confusion, following THX standard, so do it for each speaker, because each has its own distance, sensitivity, and impedance, the 3 most influential factors.

For impedance, those calculators are normally based on 8 ohms, so if for 4 ohm speaker, subject the sensitivity by 3 dB unless the specs is given in xdB/w instead of xdB/2.83 V.

Once you the results you will see clearly what the worse case is.

So again, one speaker at a time..

 

[PABZ]

Good morning. I always try to find answers that will “push” me toward upgrading. You will enjoy upgrading and any new amp purchase. The majority of experts on this website just want you to understand wattage and how it relates to your speaker’s sensitivity. Because you most likely will buy a two channel amp to power your fronts, why don’t you just focus on your front speakers?


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Thanks for responses!! I agree with just powering the fronts. Just unsure as to what wattage range I should be shopping in with the fronts 250rms/1000p, 102 sensitivity at about 17’ from seat.

 

[PABZ]

To avoid confusion, following THX standard, so do it for each speaker, because each has its own distance, sensitivity, and impedance, the 3 most influential factors.

For impedance, those calculators are normally based on 8 ohms, so if for 4 ohm speaker, subject the sensitivity by 3 dB unless the specs is given in xdB/w instead of xdB/2.83 V.

Once you the results you will see clearly what the worse case is.

So again, one speaker at a time..

What should the headroom factor be?

 

[lovinthehd]

Thanks for responses!! I agree with just powering the fronts. Just unsure as to what wattage range I should be shopping in with the fronts 250rms/1000p, 102 sensitivity at about 17’ from seat.

Well with Klipsch I'd deduct 4-5 dB from their "in-room" spec to normalize it to the normal spec. So using the calculator you can get 105 dB, which is the THX reference level peak (average being 85dB), which is quite loud....so how loud do you want to aim for?

 

[PENG]

What should the headroom factor be?

0 for now, for simplicity.

 

[PENG]

What should the headroom factor be?

I took a look of the specs of your RF7s:

When using the previously linked calculator, I took 7 dB off the specified 102 dB just to be on the conservative side and also to keep HD happy.

You can see that assuming you sit 10 ft from the RF7, with no room gain, just 1 single speaker can hit reference level with 100 W based on 8 ohm nominal impedance. If you sit further than 10 ft, just punch in the distance, basically doubling the distance will result in 6 dB reduction in spl.

If you add an external amp rated 200 W, 8 ohms, you can gain 3 dB, that's all. Yes with more speakers driven at the same at the same level the Denon AVR will not be able to sustain 100 W into 8 ohms, but even with 5 speakers driven at the same time it can still do at least 70 W per channel, and spl will only drop by 1.5 dB to 103.8 dB that is still do loud for most people.

The stories you heard from those who emphasized the so called ACD (all channel driven) power output are often by people who might have exaggerated it to make their point.

Depending on the contents, if you do listen at spl close to reference level, I do think it is a good idea to add a 3 channel power amp. The RB 990BX you mentioned would be a great choice, but its a 2 channel amp.

You may also consider class D amps such as the Hypex or Purifi amps. The best value currently seems to be the Buckeye amps. For $649 you get 350 W/500 W 8/4 ohms, or $1,049 for 4 channels.

Feel free to ask if you have more questions.

 

[PABZ]

Well with Klipsch I'd deduct 4-5 dB from their "in-room" spec to normalize it to the normal spec. So using the calculator you can get 105 dB, which is the THX reference level peak (average being 85dB), which is quite loud....so how loud do you want to aim for?

So I played the intro to Transformers “Revenge of the Fallen“ and in seating position I held my spl meter at ear height and it averaged between 76 and 81…..

 

[lovinthehd]

So I played the intro to Transformers “Revenge of the Fallen“ and in seating position I held my spl meter at ear height and it averaged between 76 and 81…..

Is that as loud as you want to get, tho?

 

[PABZ]

thank you for calculating that for me!,, Btw. Seating is 16’8” from RF7

 

[PABZ]

normally till my friends visit then Im sure it goes higher by likely 5 to 10

 

[PABZ]

Good morning, have been researching amps and have stumbled across this Rotel RB-976MKII 6 CH Bridgable amp for fronts and center (basic specs below) would this work, be a good fit, with my setup?

Power output: 60 watts per channel into 8Ω (6 channels), 150 watts into 8Ω (mono)

Frequency response: 15Hz to 100kHz

Total harmonic distortion: 0.03%

Damping factor: 150

Input sensitivity: 1.5V

Signal to noise ratio: 116dB

Speaker load impedance: 4Ω (minimum)

 

[PABZ]

Forgot to ask the important question!! Is bridging about the same as result as biamping?

 

[PENG]

Good morning, have been researching amps and have stumbled across this Rotel RB-976MKII 6 CH Bridgable amp for fronts and center (basic specs below) would this work, be a good fit, with my setup?

Power output: 60 watts per channel into 8Ω (6 channels), 150 watts into 8Ω (mono)

Frequency response: 15Hz to 100kHz

Total harmonic distortion: 0.03%

Damping factor: 150

Input sensitivity: 1.5V

Signal to noise ratio: 116dB

Speaker load impedance: 4Ω (minimum)

It will work but it's rated 60 W into 8 ohms and 150 W into 8 ohms if bridged so there is no point.

 

[PENG]

Forgot to ask the important question!! Is bridging about the same as result as biamping?

No, totally different. Bridging is connect the output of two amps in series so you get 2X the voltage. That means for the same load impedance you will get 2X the current. So you have to be very careful if you have 4 ohm speakers as the bridged amp will see the effective/equivalent load impedance half to 2 ohms vs when the amps are not bridged.

 

[PABZ]

Thanks PENG. Understand bridging better now! So based on what you said about the bridged 60w to 150w (a 45w increase over the Denon x3700h’s 105wpc) is negligible. So I should look to at least double it to 200wpc?

 

[PENG]

Thanks PENG. Understand bridging better now! So based on what you said about the bridged 60w to 150w (a 45w increase over the Denon x3700h’s 105wpc) is negligible. So I should look to at least double it to 200wpc?

Absolutely, and if you don't want to spend too much but still want excellent specs/measurements, check out the Buckeye amp that I suggested before.

Buckeye Amps: New US based Hypex multichannel amplifier builder, line-up announcement! | Audio Science Review (ASR) Forum

For so little money, you can't go wrong!

Buckeye Nc502mp Review (6 Channel Amplifer) | Audio Science Review (ASR) Forum

 

[PABZ]

Thanks PENG. Where can these be purchased from? Checked Amazon, eBay, Crutchfield no luck!

 

[PABZ]

Ok!! Went to site and found orderig info

 

[lovinthehd]

Forgot to ask the important question!! Is bridging about the same as result as biamping?

In a way, yes. They both are over-rated as to actual use and don't give the user the extra power advantage that is often imagined/implied. It's sort of the same result in the end....if you want a more powerful amp, get one that does so at the impedance rating and power level you want in the first place.