Seeking Advice Regarding Low Power Receiver and NHT Speaker Match - AVS Forum
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post #1 of 13 Old 05-28-2012, 01:41 PM - Thread Starter
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I recently purchased a TEAC CR-H500NT AM/FM Stereo CD Receiver.

This stereo only unit has a power rating of 40 watts per channel at 6 ohms.

I am interested in matching this receiver with a set of NHT bookshelf speakers, including possibly the NHT Classic Absolute Zero, Classic Two, or Classic Three.

I spoke to a Crutchfield customer service representative, and he recommended the Absolute Zero because the high efficiency of this speaker.

I would appreciate your thoughts regarding my ability to properly power the Classic Two (6 ohms) and/or Classic Three (8 ohms) on the TEAC receivier.

I believe that the minimum power rating for the Absolute Zero is 10 watts. I could not find published minimum power ratings for the Classic Two or Classic Three.

I have already returned a PSB Image B4 speaker (20 watt minimum power rating) because the stereo could not sufficiently power this speaker.

Your comments are appreciated.
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post #2 of 13 Old 05-28-2012, 02:51 PM
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None of those NHT speakers are particularly efficient, including the Zero. And so far as I could find in 90 seconds on Google, NHT doesn't publish a minimum amplifier spec for the Zero, so I don't know why you believe it was so low. At any rate, you should probably forget about NHT speakers.

As you've discovered, you really do need a very efficient speaker for that Teac. I'd suggest something like the Infinity Primus P163. It's got a sensitivity of 90 dB (the NHTs are only 86 dB) and a minimum amp power of 10 watts. If you don't like the Infinity's, you should be looking for something with those kinds of numbers.

Also, don't put too much stock in advice from Crutchfield salesmen.

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post #3 of 13 Old 05-28-2012, 05:32 PM
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Quote:
Originally Posted by suburbguy View Post

This stereo only unit has a power rating of 40 watts per channel at 6 ohms.

I am interested in matching this receiver with a set of NHT bookshelf speakers, including possibly the NHT Classic Absolute Zero, Classic Two, or Classic Three.

Also, if you buy 8ohm speakers, it will be less than 40 watts per channel.

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post #4 of 13 Old 05-29-2012, 07:10 AM
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For that 40 watt amplifier, you need a speaker that has an sensitivity of 90 db/watt or higher.

The NHT speakers have an sensitivity that is way too low, as do many of the Pioneer speakers etc. They are an extremely poor choice for any amplifier less than 100 watts. The NHT Absolute Zero has an 86db per watt sensitivity, which is very low. The Classic 3 also is 86db/watt. Bad.

The PSB Image B4 has a rating of 87db/watt, and the speaker is pretty small, so its ability to put out an adequate sound level for your room is questionable, even if power were not an issue. A 4-inch driver is just not big enough for main speakers IMO. I would always recommend a main driver that is 6 inches or more.

The Monitor Audio Bronze BX-2 has a 90db per watt sensitivity rating, and is a very nice-sounding speaker with a 6.5 inch main driver and 8 ohm impedance. I think you would be very satisfied with its performance. It should be an ideal load for your amplifier to drive, and deliver good sound levels.

20 watts applied to a speaker with a 90db/watt sensitivity will produce a SPL of 103 DBA, which is very very loud.

If you want to go louder than that, the Klipsch RB-81 is a speaker with EXTREMELY high sensitivity; 97db per watt. 20 watts applied to that speaker will give you a SPL of 110 DBA, which is super-loud!

Both of the above-mentioned speakers are available for under $500 per pair.
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post #5 of 13 Old 05-29-2012, 07:50 AM
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Quote:
Originally Posted by suburbguy View Post

I recently purchased a TEAC CR-H500NT AM/FM Stereo CD Receiver.

This stereo only unit has a power rating of 40 watts per channel at 6 ohms.

I am interested in matching this receiver with a set of NHT bookshelf speakers, including possibly the NHT Classic Absolute Zero, Classic Two, or Classic Three.

I spoke to a Crutchfield customer service representative, and he recommended the Absolute Zero because the high efficiency of this speaker.

I would appreciate your thoughts regarding my ability to properly power the Classic Two (6 ohms) and/or Classic Three (8 ohms) on the TEAC receivier.

I believe that the minimum power rating for the Absolute Zero is 10 watts. I could not find published minimum power ratings for the Classic Two or Classic Three.

I have already returned a PSB Image B4 speaker (20 watt minimum power rating) because the stereo could not sufficiently power this speaker.

There are several hidden agendas in your question such as:

(1) What sort of music do you listen to?

(2) The size and acoustics of the listening room and where you sit

(3) Your preferences for loudness.

Some basics:

A 40 wpc power amp has only 3 dB less output than an 80 wpc power amp. It would take a 400 wpc power amp to give the perception of "twice as loud" in which case the speakers might be damaged.

Comments have been made about speaker efficiency, but again a 90 dB/W speaker is only 3 dB more sensitive than a 87 dB/W speaker. It would take a 97 dB/W speaker (very rare in home audio) to sound twice as loud.

This receiver has a subwoofer output jack (line level) and adding a powered subwoofer could give you a dB or more extra apparent loudness even though the receiver appears to lack bass management or an internal crossover.


General comment - this is a very expensive relatively low-powered 2-channel receiver. You could obtain most if not all of its connectivity far more economically in other ways.
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post #6 of 13 Old 05-29-2012, 08:06 AM
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Your statements re "basics" are in error.

A 3 db increase in SPL is perceived as "twice as loud". You are claiming it takes a 10db increase, which is nonsense.

A 10db increase in SPL is DEFINED as 10 times as loud!

As noted above, the Klipsch RB-81 has a sensitivity of 97db/watt (and there are several models that are even more sensitive). It is readily available at a reasonable price.




Quote:
Originally Posted by arnyk View Post

Some basics:

A 40 wpc power amp has only 3 dB less output than an 80 wpc power amp. It would take a 400 wpc power amp to give the perception of "twice as loud" in which case the speakers might be damaged.

Comments have been made about speaker efficiency, but again a 90 dB/W speaker is only 3 dB more sensitive than a 87 dB/W speaker. It would take a 97 dB/W speaker (very rare in home audio) to sound twice as loud.

.

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post #7 of 13 Old 05-29-2012, 08:20 AM
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Just a note to commenters: This is not really a 40w amp. The spec is:
Quote:
Minimum 40W + 40W (6 ohms, 1kHz, 0.5%THD)

It's clearly not as powerful as a 40w amp specced at 8 ohms over full bandwidth, and that's a pretty high THD tolerance as well.

If you can't explain how it works, you can't say it doesn't.—The High-End Creed

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post #8 of 13 Old 05-29-2012, 08:24 AM
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Quote:
A 3 db increase in SPL is perceived as "twice as loud". You are claiming it takes a 10db increase, which is nonsense.

I'm afraid you've got that wrong. 3 dB is a doubling of acoustic power, but that's not the same as perceived loudness. The rule of thumb is that it takes 10 dB to double perceived loudness.

If you can't explain how it works, you can't say it doesn't.—The High-End Creed

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post #9 of 13 Old 05-29-2012, 09:13 AM
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Quote:
Originally Posted by commsysman View Post

Your statements re "basics" are in error.

A 3 db increase in SPL is perceived as "twice as loud".

Simply not true. 3 dB is a doubling of power, but that isn't the same as perceived loudness. Anybody who works with professional equipment that has proper dB calibrations knows that 3 dB is clearly noticable, but nothing like twice as loud.

Quote:
You are claiming it takes a 10db increase, which is nonsense.

A 10db increase in SPL is DEFINED as 10 times as loud!

No, 10 dB more is 10 times as much power.

Here, lets do a little research:

http://www.gcaudio.com/resources/how...eloudness.html

"Looking at the chart, and starting at the left, we can see than an increase of 3dB results in a voltage increase 1.4 times the original, a doubling of power, and yields only a subjective increase in loudness only 1.23 times the original. To get a doubling of loudness, it is important to note that an increase of 10dB is necessary. And to reproduce that volume through our loudspeakers, note that we require ten times more power from the amplifier!"

If you Google around a bit you can find many recitations of the same basic idea. I'm not going to post any more because its so easy to confirm this.

Quote:
As noted above, the Klipsch RB-81 has a sensitivity of 97db/watt (and there are several models that are even more sensitive). It is readily available at a reasonable price.

That's a specification, and it may or may not be taken at face value. Speaker sensitivity is one of more often fudged specs that there are. For example, it is possible to build a speaker that has a 3 dB rise in the frequency range on which the specification is based (which is usually not given with the spec) but is actually half as efficient over much of the audible range. A 3 dB variation in speaker frequency response is often accepted by many listeners.

Building efficient midrange speakers and tweeters is not nearly as tough and inherently expensive as building woofers that have high efficiency, reasonable size and linear bass extension. In fact many permutations of the latter are completely impossible according to the laws of physics.
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post #10 of 13 Old 05-29-2012, 12:53 PM
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The Klipsch RB-81, measures around 91db > the marketing game continues.
http://www.hometheater.com/content/k...-labs-measures

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post #11 of 13 Old 05-29-2012, 12:54 PM
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Lies, damned lies, and specifications.

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post #12 of 13 Old 06-04-2012, 05:00 PM - Thread Starter
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Thank you for the helpful advice regarding matching the TEAC Receiver and NHT Speakers.

I returned the TEAC Receiver because it simply could not drive the NHT Absolute Zero or Classic Three at even moderate volume levels.
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post #13 of 13 Old 06-05-2012, 04:34 AM
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Quote:
Originally Posted by suburbguy View Post

Thank you for the helpful advice regarding matching the TEAC Receiver and NHT Speakers.

I returned the TEAC Receiver because it simply could not drive the NHT Absolute Zero or Classic Three at even moderate volume levels.

What wouldn't happen that you wanted to happen?
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