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Discussion Starter · #1 ·
ok so my setup for the past year has been onkyo 818 receiver ascend acoustics 340 for the lcr.

and for my surrounds ive just been using the ones that came with the onkyo htib setup. so i am having a room in a house converted to a media room, nothing major just about 132 square ft.

anyway i chose to go with 4 ascend acoustics cbm 170 and they are rated at 200rms 400 peak.

my question is will my onkyo reciever be able to adequately power my speakers? would i benefit from maybe adding a emotiva xpa 5 or maybe xpa 3?

i usually watch movies at or near reference level if that helps. ive never done any kind of external amplification before so i have questions about that myself like when you run audyssey will it run it for the speakers that are run off the external amp, or will it only do the ones connected directly to the onkyo?

any tips or suggestions would help thanks
 

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Will be fine with the onkyo as those speakers are easy load and easy to drive. 200W will be overkill. But if you did want to get dedicated amps I'd get something like Outlaw 7125 that will be plenty. Onkyo calibration will adjust pre-out channel adjustment to match external amps, and internal (so if gains are different) so it's all calibrated and matched.
 

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Discussion Starter · #3 ·
thanks for your advice. ill just set everything up then have a listen to how everything sounds before deciding.
 

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That is going to be a very nice system! Congratulations.

Your Onkyo seems more than capable of driving these speakers. The 340 has a sensitivity rating of 92 dB, while the 170s is at 89 dB. After you have everything going and if you find yourself unhappy (I seriously doubt it), your Onkyo has preamplifier output ports so you can add whatever amplifier you want.
 
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Discussion Starter · #5 ·
thanks! ive been reading alot of info on amps and how some people say they help and others saying they dont hear a difference. i guess its just something you have to hear and compare for yourself.
 

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^ Exactly. And let us know what you think when everything is up and running!
 

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Some speakers need the extra power to sound their best. After buying a $1000 amp the human mind says it *must* sound better cause it looks so awesome. Chances are there is some subjectiveness going on. If you want some entertainment go read some of the 'mono-block society' stuff over at the Emotiva Lounge. Anyways - $1000 has to sound better - right? All amps do not sound the same but they are so close that it is very difficult to tell one from another as long as they are operated within their normal parameters. A shiny new amp sitting in the audio rack may just sway the opinion a bit. Ever heard of the
? Thats just one example of how perception is influenced. Everything around us 'flavors' how we perceive - and often quite different than a person next to you who may have seen and heard something slightly or significantly different than you.
 
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interesting. i see what u mean and part of me thinks its that cool factor of seeing those amps in the av rack and not really hearing much of a difference. but like u said it depends on the speakers and maybe size of the room maybe?
 

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**********

ok so my setup for the past year has been onkyo 818 receiver ascend acoustics 340 for the lcr.

and for my surrounds ive just been using the ones that came with the onkyo htib setup. so i am having a room in a house converted to a media room, nothing major just about 132 square ft.

anyway i chose to go with 4 ascend acoustics cbm 170 and they are rated at 200rms 400 peak.
That is a terrific set of speakers! The Ascend SE's have a price/performance ratio that's very tough to beat. :)

The power figures you've quoted are maximum continuous and short term power (handling) figures. These are indicative figures, beyond which the speaker manufacturer believes permanent damage will be done to the speaker's drivers; for example through thermal overload (tweeter) or over-excursion (woofer). They are not an indicator that this amount of power is needed to "get the best out of" the speakers. They'll sound great on as little as 1W!

The figure on the CBM-170's spec sheet that's more relevant to your question is their sensitivity of 89dB/1W/1m. (That is, 89dBSPL of acoustic output with 1W of input power when measured at 1 metre.) I don't know exactly which Onkyo HTiB speakers you were using, but if they're anything like the speakers in this system, they'll have a sensitivity of 83dB/1W/1m at most. The 6dB sensitivity difference is significant and means that, on average, each Onkyo HTiB speaker required 4 times [dB = 10 * Log(Pout/Pin)] the input power of a CBM-170 to play at any given level. :eek:

In other words, you've effectively reduced your amplification requirements for the surround channels by upgrading to the Ascends. :D

my question is will my onkyo reciever be able to adequately power my speakers? would i benefit from maybe adding a emotiva xpa 5 or maybe xpa 3?

i usually watch movies at or near reference level if that helps. ive never done any kind of external amplification before so i have questions about that myself like when you run audyssey will it run it for the speakers that are run off the external amp, or will it only do the ones connected directly to the onkyo?

any tips or suggestions would help thanks
Yes, that sure does help! :)

Various room and equipment factors aside, a system correctly calibrated by Audyssey (and other auto set-up routines) has a total electro-acoustic gain set up such that when at THX/Dolby/SMPTE “Reference" (0dB master volume), program peaks can theoretically be up to 105dBSPL (ie. with a 0dBFS input signal) for each “satellite" channel, when measured at the listening position (LP).

Now in typical residential rooms, sound pressure attenuates at what equates to 3 - 4dB (net) each time you double the distance from the source (speaker). Just going on your room size, I’m guessing the distance from the speakers to your LP will be about 10ft. So at an average of 3.5dBSPL attenuation per doubling of distance, we get a total attenuation of about 5dBSPL. This means that each of your CMT-340’s will need to play at 110dBSPL at 1m from the baffle to produce those 105dBSPL peaks at your LP.

The CMT-340’s have a honestly rated sensitivity of 90dBSPL with 1W at 1m. So they require 20dBW (dB referenced to 1W) of gain from the amp to play those 110dBSPL peaks. This equates to 100W. That's right - the maximum amplifier power required to produce program peaks at 0dBMV at a 10ft listening distance, with your speakers is a 100W burst.

The next aspect to be aware of is that amplifiers specified continuous ("RMS") power ratings are measured with sine waves. Sine waves have a 3dB crest factor (average to peak), so we can legitimately reduce the peak amp power by 3dB (or half) to determine the minimum equivalent RMS rating required. So in this "Reference/0dBMV" scenario, 50WRMS is indicated. (Alternately, you could consider that the 3dB of headroom is already built in to the calculation.)

This power level is comfortably within the continuous power capabilities of your Onkyo (135W; 8Ω, 20Hz - 20kHz, 0.08%, 2 channels driven, FTC). So unless your preferred maximum volume level increases to beyond Reference Level in the future, your Onkyo is more than capable of adequately driving the Ascends in your situation, and the addition of power amps would be of no real benefit.

interesting. i see what u mean and part of me thinks its that cool factor of seeing those amps in the av rack and not really hearing much of a difference. but like u said it depends on the speakers and maybe size of the room maybe?
Speakers and room size brings me to my last point... The Onkyo TX-NR818 carries the THX Select2+ certification. An AVR carrying this certification will play any commercially available multichannel program material to Reference Level in a "Select2+ sized" room when hooked up to speakers with a sensitivity of 89dB/1W/1m and nominal impedances of 4Ω (LCR) and 8Ω (surrounds).

A Select2+ sized room is up to 2000ft^3 with a viewing distance of 10 - 12ft from the screen. The Ascends meet or exceed the above two speaker metrics, and (based on an 8ft ceiling height) your new media room will be 1060ft^3 or significantly smaller than the specified size. So again, this should demonstrate that your Onkyo will have capability to spare (headroom) at Reference Level, in your room.

I guess that's a very long way of saying what others have already told you: you'll have no worries with the Onkyo/Ascend combo in your new room.

Great speakers! Enjoy! :)
 

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It probably doesn't affect the OP with the Ascends...

But what I've been learning is that low impedance dips can throw off the armchair back-of-napkin calculations.

Sensitivity will vary by frequency...
  • You can figure either 1w will give you different output at one frequency vs another.
  • Or you can figure that while 2.83v may give a fairly even db SPL, the power requirements will vary wildly, based on impedance.

So, sure, one can generalize based on 8ohm and XX sensitivity...I do all the time.
But when certain speakers are mis-spec'd as 8ohm but should be 4-6 ohm, AND they have impedance dips in mid-bass with an extreme phase angle, the power requirements can be way higher.

So e.g. a 100w requirement with a 3dB cushion can disappear and one is short of power. And either the amp is clipping, or the speaker is being fed way more power than expected (and thus distorting), or at least dynamic peaks are clipped and we're missing some impact.

Point is, to truly know what a speaker will do, we need to see impedance and phase. :)
 
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