Bi-amping using my NAD T773...awesome!!

dkg999

Sid - are you a chocolate or vanilla type of dude? That's the important question in this thread

VR3

I love chocolate ice cream!

danger boy

i call bi amping Howard

jdhdiggs

Amateurs!

I have actively quad amped a system. Actually, if you count the amp plugs into the wall, I hex amped that ****!

If you are not using a crossover before the amp, you are not providing the speaker with anything other than 1-2 watts of more power. Additionally, if you move the crossover in front of the amps, all you have done is added the 1-2 watts more power to each side and eliminated the harmonic distortion originated on the down side on the crossover slope. Things to research: Ratio of power vs frequency vs. dB (essentially ever octive you drop, you need to double the power output to maintain the same dB level). Another thing to research is how crossovers work. The 400kOhm reading was probably found based on a static resistance reading. Above the x-over frequency, it is around 4-8 ohms. Resistance in these systems means nothing without attaching a frequency to them. One of the common misconceptions around here is to use V=IR for everything without realizing R is a moving target and is different when heading to different parts of the speaker.

The only way you gain significant advantages IMHO is to use different amps with different strengths. For example, in my quad/hex amp I used my Knight mono 35W tub amps on the tweeter section, Counterpoint 170W Hybrid amp for the mids, adcom 565 mono's on the mid-bass/bass and a bash digital for the bass-sub bass. Sounded fantastic once dialed in.

Yashu

That is a lot of amps man... but what kind of speakers let you bypass their crossovers and use your own? Sounds like a DIY system.

I don't buy into the "only one to two watts" statement... at least not with all types of speakers, but I do agree about trying to match amps to their strengths.

jdhdiggs

Magnepan 3.3R's let me run 3 external crossovers if I want and I added an additional high pass/low pass combo to pull sub 45 Hz info to a sub.

The 1 to 2 watts statement comes from how power is used by a speaker. For simplicity, let's use a simple 2 driver configuration and 2 200W amps. The tweeter will rarely (If ever) take more than 1 or 2 watts. If you are running a watt or more to your tweeters, you're nuts-much more than 2 watts and they'll start melting.

For ease of the example, we'll just say your tweeter section is using 2 watts. The amp powering this section can generate 200 W but if the max signal is 2 W and you blow your speakers at 5 W. What are you doing with the rest of that power?

Now let's look at the lower section: This is where most of the power is consumed. In the mono amp situation the tweeter was pulling 2 watts leaving 198 for the midbass/bass. Now you've eliminated that massive load and can add it to the low end.

Congrats, you've gone from 200W of usable power to 202 watts and doubled your cost. Now you can go into some esoteric designs where this will change a bit, but that's a different ballgame. There's always an exception.

An example of how power cascades to the lower frequencies, here's how my rig was setup (freq ranges are approximate, I can't find the exact numbers right now):

35 W Tweeter (1.7 KHz +)
170W Mid Bass (180 Hz to 2 kHz)
450W Bass (40 Hz to 200 Hz)
900W Sub Bass (<45 Hz)

The 900W maxed out first, then the 450 W amp gave out, then the 170W amp. The amp that had the most loafing was the 35W amp. Now remember, this was a 82dB/Watt system in a 9,000 cubic foot room to even test where the powere would give out. (No I never clipped the amps or popped fuses, I had another method of protection that let me know when it was about to "blow").

heiney9

Yashu wrote: »

I don't buy into the "only one to two watts" statement... at least not with all types of speakers, but I do agree about trying to match amps to their strengths.

Check out Nelson Pass's First Watt products. There is some truth to low power amps not being right for every type of speaker.

H9

Yashu

Well yes of course, not all amps are made for all speakers, and when you combine several different types you run into problems like voice matching and whatnot... I was just thinking of how nice an all tubed mid/HF could potentially sound with the raw power of SS on the bass.

Extra 2 watts aside, I like the idea of using ALL the channels of the amp and better distributing the load, even if just a bit.

MGPK

FYI

Bi-Wiring Pros:
Easy; Inexpensive; choice of ideal cable for use (high frequency = low capacitance / low frequency = low resistance); lowered resistance in total cable solution; some perceived improvement in sound in non-scientific tests.

Bi-Wiring Cons:
Questionable effect of one cable on the other since they are connected in parallel (capacitance and inductance of one cable will affect the capacitance of the whole system); not always perceived improvement.

Passive Bi-Amping Pros:
All the same pros as Bi-wiring pros; dedicated power supplies for each driver for improved dynamics and maximum sustained output; improved damping; greater isolation between low and high signals; amplifier technology could be matched to usage (Class-A for treble, High Current/Power for bass); more perceived improvement in sound in non-scientific tests.

Passive Bi-Amping Cons:
Added cost; more difficult as amps must be matched in gain ratio; no improvement in amplifier efficiency; still not 100% perceived improvment sound.

Active/Passive Bi-Amping Pros:
All the pros mentioned above; slight increase amp power supply efficiency; reduction in amp noise; easier to calibrate output levels (assuming crossover has level controls); yet more perceived improvement in sound.

Active/Passive Bi-Amping Cons:
Some passive crossovers designed for shallow slopes requiring crossover to be several octaves outside of crossover point; Few active crossovers have settings for unique crossover points for high pass and low pass (in this design the high pass must be an octave or two high than the passive crossover and the low pass crossover must be an octave or two below the passive crossover); more complicated setup; significant added cost (especially as active crossover must be custom designed for unique crossover points for each output); perceived improvement may not be improvement but perceived difference as setup is quite complex.

Active Bi-Amping Pros:
Most efficient use of amplifier power; maximum damping from amp due to elimination of all passive components; improved phase response (with proper crossover design); faster sound/greater "negative" dynamics (no discharging of fields in capacitors and inductors that cause ringing); nearly 100% perceived improvement of sound.

Active Bi-Amping Cons:
Most commercial loudspeakers are not design nor are easy to actively bi-amp; commercial speakers often have tuning circuits in passive crossovers that are not easily replicated with active crossovers requiring EQs; Very complex to tune; Fixed matching high pass and low pass slopes cannot take into account acoustical slopes inherent in drivers; Expensive.

Systems

Good informative post MGPK,I can vouch for the improvements wrought by going fully active.

My set up is now fully active and the change has been worth the added complexity.I now hear more detail, the system can play louder without stress ,reduced distortion with far less listening fatiuge when played at higher levels.

Im using relatively small amps for more the mids and tweets (60 watt Bryston 2B LP's)and they are usually just loafing along and almost never run into clipping.The odd loud movie sound track will cause brief clipping in the mid amp.

The woofers are driven by a 120 watt Bryston 3B that seems to be just enough clean power to drive them without constantly running into clipping. The active crossover's slopes and xover points where optimized for the drivers Im using which is very important.
So Im convinced properly done,active offers big gains in SQ.

jdhdiggs

MGPK:

Since I have not noticed you before, let me say:

Welcome, you are DEFINATELY a welcome addition to the board!

dannyp

How did you bi amp your Nad T773?
What instructions did Nad give you?

dannyp

. I emailed NAD & they told me how to do it, very simple to say the least. WOW!!! not only am I impressed with the sweet, laid back sound of the NAD, the power is just awesome..[/quote]

dannyp

pearsall001 wrote: »

I emailed NAD & they told me how to do it, very simple to say the least. WOW!!! .

How.do you do bi amp the Nad T773?

audioluvr

Nice necropost!

gp4jesus

My 2 cents…

Sorry for coming past late to the party.
I’m calling it 100+WRMS ON TAP, on tap the key operative, for the top, bottom, & anything in between. Those late model Chrysler Hemis have 700+HP ON TAP.

NAD’s specs for the T773:
“Power output: 110Wx7 minimum continuous power @ 4ohms or 8ohms, all channels driven; 230W, 320W, 390W IHF "dynamic power" into 8ohms, 4ohms, & 2 ohms, respectively; switchable "soft clipping" feature “

From the “Sound & Vision” test bench
“With two channels driven, the NAD's power output at clipping (1% THD+noise) measured 114W per channel at 1kHz into 8ohm, and 179Wpc into 4ohm (left channel measured).

With all seven channels operating, the left channel measured to the nearest watt, the NAD clipped:
at 20Hz 103Wpc into 8ohms, 120Wpc into 4ohms
at 1kHz 108Wpc into 8 ohms, 131Wpc into 4ohms.”

https://www.soundandvision.com/content/nad-t-773-av-receiver-measurements

From HiFi Review:
The giant Holmgren toroidal transformer with a power of more than a kilowatt serves amplifiers, the circuits of which use the proprietary technology of soft amplitude limiting of the Soft Cliping signal (disconnectable).

If I were designing & building a HT amp for 7+ channels…
Marker posted:
“FWIW, the T773 has not just one, but two toroidal transformers, one for the front three channels, and a second for the other four.”

WilliamM2 posted:
“Everyone seems to ignore that the tweeter will only draw a few watts. I've done the experiment myself with my CSi40, I am currently bi-amping it with 2 channels of a 150wpc amp. It has no more output, or at least not enough to register on the SPL meter, than it did with one channel at 150wpc. Oddly enough, it still seems to sound the same as well.”

Bill Ayotte posted:
“I think you are putting 220 to each speaker....110 on highs, and 110 on mid/lows....Technically, those channels are still driving something, so the 145 rule would not apply....Just my thought......”