IOTAVX AVXP1 7 Channel POWER AMPLIFIER

Conrad

Moderator
Thanks for the excellent analysis. The speakers are a pair of monitor audio MR6 rated at 150W/CH and according to the manufacturer, can go down to about 33HZ. Despite this I set the crossover to 80HZ ( which is nothing for these speakers ) at the receiver end so any amplification that takes place is 80HZ and above.
The issue isn't where you cross over to the subs, I'm in a similar position (-3dB at 33Hz, measured in room lower) the issue is the crossover in the speakers.

If you have an 80Hz - 20kHz signal that you feed two of to the speaker, the HF terminals will discard anything below, probably, around 2kHz. So you're left with about 4 octaves of content. The LF terminals will discard anything above 2kHz, leaving you with about 5 octaves of content, so pretty even.

When I had it bi-amped with the internal amp of my RXA 3060 rated at 150W x 2 into 8ohms I definitely heard a difference. The front stage sounded more open and spacious, with lots of headroom vs before, plus it was noticeably louder and the dynamic range also seemed a tad more aggressive.

My thinking is if the internal amps of an AVR could have made such a difference, imagine what bi-amping from a dedicated power amp could do? I was just wondering whether 250W from one amp into one speaker will sound better than 110W x 2 bi-amped into the same speaker?
Just FYI, I bi-amp both my dedicated cinema mains and my office mains. Cinema has 300wpc into 8 and 600wpc into 4ohms, office has 350wpc into 8 (Rotel don't publish their 4ohm specs but it is the only amp I've ever seen with a BTU rating!). In both cases it made no difference. I've also run those same mains with PA amps, duals sounds better than singles (two transformers) but four didn't sound better than two.

I'm not saying you didn't hear a difference, but expectation bias and audio memory are tricky characters.
 
The issue isn't where you cross over to the subs, I'm in a similar position (-3dB at 33Hz, measured in room lower) the issue is the crossover in the speakers.

If you have an 80Hz - 20kHz signal that you feed two of to the speaker, the HF terminals will discard anything below, probably, around 2kHz. So you're left with about 4 octaves of content. The LF terminals will discard anything above 2kHz, leaving you with about 5 octaves of content, so pretty even.


Just FYI, I bi-amp both my dedicated cinema mains and my office mains. Cinema has 300wpc into 8 and 600wpc into 4ohms, office has 350wpc into 8 (Rotel don't publish their 4ohm specs but it is the only amp I've ever seen with a BTU rating!). In both cases it made no difference. I've also run those same mains with PA amps, duals sounds better than singles (two transformers) but four didn't sound better than two.

I'm not saying you didn't hear a difference, but expectation bias and audio memory are tricky characters.
Ha ha ha ha I love the last line. So you don't think bi-amp with two amps rated at 110W each into 8 ohms will sound better than than a single amp rated at 250W into 8ohms?
 

Conrad

Moderator
I think it's tough to say for sure. If you have the cables and the amps it's free to try. I wouldn't worry about going out to buy amps unless to bi-amp unless you're unhappy with what you have now.

Despite my negative stance on the issue, as I mentioned, I do bi-amp both of my main speakers! Mainly because the terminals are available and I had the cable.

That said, even if it is expectation bias but you feel that it sounds better, does it matter if it does or doesn't? What matters is your enjoyment of the system.
 

rccarguy2

Distinguished Member
I went from biamping front three to single amp powering front three.

Biamping for HT seems a bit ott
For hifi I would do it and I have
 

Isco 3

Active Member
You are bi-amping a passive crossover, so I would expect the better amp to sound better and that's it. It offers no other benefit when it comes to how the internal crossover is used. You are not bypassing any circuitry with bi-wiring, so you are not gaining anything. I would watch this video and you can see what is happening inside the speaker.
 
Wow thanks for the input guys. I was actually planning to purchase an IOTA and then test it bi-amped vs my current XPA in single amp? It's a calculated risk as I can always return the IOTA if there's no benefit albeit unfair to the retailer.
 

Isco 3

Active Member
You can use your existing XPA and bi-amp your speakers and you will see what it has to offer. That would actually be a better test because you will use the same amp, and the only variable would be the power-doubling. You can't use a single channel of a powerful Krell and then bi-amp with a Rotel, and expect the bi-amped combo to sound better, because you just bi-amped. I would say it is a waste of resources when you already have 250W on a single channel.

Also, bi-amping with the 110W IOTA power amp you will have less power going to the speakers' woofer, so more likely they would sound worse. (Unless you had 110W Krell Watts :D )
 
Last edited:
I must have misread your post. I now understand. Bi-amping with a lower rated amp won't sound better than a more powerful single amp.👍
 

Isco 3

Active Member
If the lower rated amp is exotic, might sound better.
 

Isco 3

Active Member
Bi-amp with your Emotiva and see what bi-amping does. You will just waste 250W on a tweeter I believe.
 
You can use your existing XPA and bi-amp your speakers and you will see what it has to offer. That would actually be a better test because you will use the same amp, and the only variable would be the power-doubling. You can't use a single channel of a powerful Krell and then bi-amp with a Rotel, and expect the bi-amped combo to sound better, because you just bi-amped. I would say it is a waste of resources when you already have 250W on a single channel.

Also, bi-amping with the 110W IOTA power amp you will have less power going to the speakers' woofer, so more likely they would sound worse. (Unless you had 110W Krell Watts :D )
So the power rating can vary from manufacturer? So 100W from a krell is more powerful than 100W from IOTA?
 

Isco 3

Active Member
A Krell would probably give you [email protected] Ohm, [email protected] 4 Ohm, 400W @2Ohm. You get the idea. They are exotic power amps and they would sound better. What does the IOTA have to offer? Less power for sure.
Bi-amping does nothing; signal goes through the same filters inside the speakers even when you send a single channel. By sending 110W with the IOTA to the woofer I see you have less power available now. Why do that?
 

Isco 3

Active Member
Do you think I should sell my Parasound JC1 mono blocks and bi-amp with an Emotiva for example?
 

Isco 3

Active Member
The speaker inside has a low pass and a high pass filter. You send the full range signal to the tweeter and allows only the higher frequencies and the other filter allows the lower frequencies that go to the woofer. A single channel to the speaker sends the full range signal with a single cable and because you have a bridge on the terminals at the back of the speaker, it goes to both filters simultaneously. When you remove the bridge at the back and you bi-amp, you then just need two cables to send the same full range signal. It follows the exact same path inside, nothing is bypassed.
 
A Krell would probably give you [email protected] Ohm, [email protected] 4 Ohm, 400W @2Ohm. You get the idea. They are exotic power amps and they would sound better. What does the IOTA have to offer? Less power for sure.
Bi-amping does nothing; signal goes through the same filters inside the speakers even when you send a single channel. By sending 110W with the IOTA to the woofer I see you have less power available now. Why do that?
The IOTA is rated at 110W x 7 into 8ohms. So if I bi-amp with it, it would be 110W to the woofer and another 110W to the midrange and tweeter so 220W in total biamped Vs the 250 single amp from the XPA.
 

Conrad

Moderator
The IOTA is rated at 110W x 7 into 8ohms. So if I bi-amp with it, it would be 110W to the woofer and another 110W to the midrange and tweeter so 220W in total biamped Vs the 250 single amp from the XPA.
No.

You use 110w to amplify a full range signal which you then give to the LF terminal which then filters out half (55w). And you use another 110w to amplify a second full range signal which you give to the HF terminal which filters half out (55w). Leaving you with 110w of signal. But you’ve made the amp use up 220w to amplify them meaning you’ve used up headroom and increased noise and distortion.
 

Isco 3

Active Member
Woofer can only use 110W though. Tweeter doesn't need much, you are limiting the ability and you are adding extra unnecessary cables in the signal path.
 

Isco 3

Active Member

Isco 3

Active Member
The easiest test would be to bi-amp with your XPA and use two channels to drive a single speaker. I bet you will hear no difference and you will just end up with double the cabling. If you can't hear a difference going from 250W to 2x250W per speaker, then you can conclude that the 2x110W will not impress you. :smashin:
 
No.

You use 110w to amplify a full range signal which you then give to the LF terminal which then filters out half (55w). And you use another 110w to amplify a second full range signal which you give to the HF terminal which filters half out (55w). Leaving you with 110w of signal. But you’ve made the amp use up 220w to amplify them meaning you’ve used up headroom and increased noise and distortion.
Wow so the advice is to just leave the XPA as is? Though remember I said I set the crossover at 80hz so it's not a full range signal I'm amplifying?
 

Conrad

Moderator
80 up is a near enough a full range signal, it’s just bass managed.
 

The latest video from AVForums

Maverick UK Premiere IMAX Review + Top Gun, Tom Cruise, Tony Scott and 4K + Movie/TV News
Subscribe to our YouTube channel

Latest News

Movies Podcast | Maverick IMAX Review, 4K Disc News and More
  • By Phil Hinton
  • Published
What's new on Netflix UK for June 2022
  • By Andy Bassett
  • Published
Triangle announces new wireless Borea Active bookshelf speakers
  • By Ian Collen
  • Published

Full fat HDMI teeshirts

Support AVForums with Patreon

Top Bottom