Bi-amped my RTi8's finally! (200 watts/channel)

MattN03

My AQ Diamondbacks came in today, allowing me to biamp the Rotel 985 to the RTi8's giving me 200 watts/channel. Wow, biamping really makes a difference I switched the 8's over to large and turned the SVS off so I could listen to a few CD's. After trying Saliva, Metallica, Brooks & Dunn, and Toby Keith, I can definately say without a doubt biamping made the RTi8's sound better than running them off the H/K alone. Heck, even my wife thought they sounded better! The RTi8's play clearer and have more presence in the room if that makes sense. It also seemed to tone down the brightness to some degree. Bass is punchier and much improved also.

For anyone wondering about the effects of biamping their RTi8's, I'd say go for it. They love the extra power!

I want to send a special thanks out to Olkiepolkie who has helped me get all this gear together and provided a great deal of technical insight. Thanks Zach! You're the man!!

audiobliss

Awesome! Bi-amping is cool.

So, is the HK handling the highs and the Rotel the lows?

MattN03

Actually, the Rotel fronts are handling the lows while the Rotel rears are handling the highs. I have another Diamondback to use between the Rotel center channel and the CSi5-I just ran out of time to hook it up last night. That'll leave the H/K powering the FXi5's only. Too bad I can't bi-amp the H/K

audiobliss

Oh, oh, you have a 5-channel Rotel. I got ya. Well, that's awesome. Now get that center hooked up!!

MattN03

audiobliss wrote:

Oh, oh, you have a 5-channel Rotel. I got ya. Well, that's awesome. Now get that center hooked up!!

I think the CSi5 will like the extra juice too

okiepolkie

Enjoy the improvements. Now get an SPL meter and calibrate your system, again. Since the bass is so much better now, you can send the SVS over my way

zombie boy 2000

Good deal Matt:)

Seems to me you've been on the upgrade warpath of late:p

joeparaski

okiepolkie wrote:

Enjoy the improvements. Now get an SPL meter and calibrate your system, again. Since the bass is so much better now, you can send the SVS over my way

Hey OlkiPolkie...when you mentioned the spl meter and calibration, I was thinking...should a bi-amped system have its highs and lows calibrated individually or together?

Joe

okiepolkie

From my understanding, it depends on how they are biamped. Matt, for example, is using a four channels of five channel amplifier to power the fronts. Theoretically, each channel should be at the same level. Since they are at the same level, the highs and lows should already be calibrated. Again, in Matt's specific system, the 8's as a whole should be calibrated to blend with the rest of the system.

When you use two separate amplifiers, the internal gain is most likely different for each amp. Even with amplifiers of the same brand and model, there may be some slight differences. Since the gain is different, the sound coming out of the highs might be at a different level than the lows.

My understanding hits a bump at this point, as I am not sure what frequencies to send each section to get the levels balanced. I don't know the frequency of regular test tones, but I know it doesn't cover the whole spectrum. Plus, room acoustics may play a part in what frequency you do your calibrations. What if you have a null at 3500Hz due to room acoustics, and you do your high calibrations at 3500Hz. When you calibrate your lows, you might run into the same problem. Therefore, your soundfield as a whole might be compromised at the other frequencies.

I guess the surest way to calibrate as a whole would be to have test tones at regular intervals throughout the spectrum. This is done with subwoofers very extensively, since the boominess is often more of a distraction than problems in the upper register.

Again, this is my current understanding, and I might be over analyzing or under analyzing the things.

So, to answer your specific question, yes and/or no. In the first instance, they wouldbe calibrated together. In second system, they could be biamped separately.

The actual setup of the biamped system will be the biggest determining factor.

jdhdiggs

If you are using the same amp, you'll have the same gain across both channels. No need to calibrate seperately. Besides, without a variable gain amp or lin attenuaters there is no way to calibrate them seperately.

Matt:

Have you tried using the rotel for all the speakers instead of bi-amping? You may find more of a gain for the whole system going that route. If you really want to bi-amp, experiment with the HK on the tweets.

MattN03

jdhdiggs wrote:

Matt:

Have you tried using the rotel for all the speakers instead of bi-amping? You may find more of a gain for the whole system going that route. If you really want to bi-amp, experiment with the HK on the tweets.

No, I haven't tried the amp on the whole system. I might leave it alone for a couple weeks and enjoy the improvements (after recalibrating) and then give the Rotel a shot at all the speakers. So would it be alright to send the 8's less power to the tweeter by using the H/K and using the Rotel for the mids/lows?

MattN03

zombie boy 2000 wrote:

Good deal Matt:)

Seems to me you've been on the upgrade warpath of late:p

Yeah, this forum is the cause of that I *think* I might be done for a little while though. :eek:

MattN03

okiepolkie wrote:

Enjoy the improvements. Now get an SPL meter and calibrate your system, again. Since the bass is so much better now, you can send the SVS over my way

Now I don't know if it's THAT much better I still have to be able to shake the neighbors house as well as my own

jdhdiggs

MattN03 wrote:

No, I haven't tried the amp on the whole system. I might leave it alone for a couple weeks and enjoy the improvements (after recalibrating) and then give the Rotel a shot at all the speakers. So would it be alright to send the 8's less power to the tweeter by using the H/K and using the Rotel for the mids/lows?

Yes, you'd be fine from a speaker protection point of view. Having less power available to the tweets is not a problem. Does the rotel have a gain control on it? If not, i might not work really well (might be VERY bright or VERY laid back). If you don't have gain control on the rotel, as long as its a higher gain than the HK amps through line attenuaters.

Also, honestly look at how much bi-amping the 8's gets you versus one amp per speak and giving the extra juice to the rears. Don't just assume it's the bi-amp that's getting you the improvement but rather the quality of amp. Might be fun to experiment BEFORE you get used to the sound.

GATOR3000

MattN03 wrote:

allowing me to biamp the Rotel 985 to the RTi8's giving me 200 watts/channel

Matt congrats on your new AQ Diamondbacks! Enjoy!

But I don’t get this 200 WPC bi-amped? While back I did bi-amped my 8’s with B&K AV5000 105W x 5 and I thought I was getting 210 WPC up front. Than someone (I don’t remember who) on that particular thread corrected me that even when I bi-amped the fronts I was still getting only 105 WPC for the front 8’s.

The explanation was that I still get only 105 watts to the tweeter and 105 watts to mid woofer. All in all it is only 105 watts per speaker and not 210 watts/speaker.

One thing I can say from my experience, when I got Parasound HCA 1500A 205 x 2 WPC, I was getting real 205 watts and the 8’s were singing a lot better than when bi-amped with B&K at 105 watts to tweeters and 105 watts to mid woofer.

Can someone clarify what is correct? Is it 105 WPC or 210 WPC?……………Thanks.

Gator

jdhdiggs

Gator:

Depends on the frequency and comparitive volumes. It is not 210 except in the most theoretical of cases in which case your tweeter would burst forth from the speaker and head towards you like a frisbee from hell. In real world terms (ie: actual programming) you'd be maxing out at around 110W. In other words, it depends. Below is some background on my "guess":

Some typical rules of thumb:
tweeters are between 3 and 10 dB's mor effecient than woofers (hence why you generally only have 1 tweeter and multiple mids and woofs)
a 3dB increase Accoustic power (the volume you hear) requires twice the watts
Every octave drop requires a doubling of power for the same dB's

So, a woofer playing an 50 Hz tone would roughly need about 512 times more power than a tweeter playing a 12.8 khz tone for the same dB level. This is how I can run a 30W amp and a 500+W amp and the big amp begs for mercy well before my little tube amp does sine it runs the bass end of things.

Because of all of this you limit how much benifit the second amp gives you. Also remember, while mids and woofs can handle say 50-1,000W per driver, a typical tweeter can only handle 2-3W before melting. You'll have some wasted power into the crossover but on a simple speaker where the top posts go only to the tweet, I can't see you pushing more than 5W.

Hope that clarifies it a bit... If you want more esoteric and theoretical jargon, look up an old thread with MM and I debating real world versus theory and biamping.

GATOR3000

jdhdiggs,

Thanks for sharing your knowledge/experience. Make sense. I will look and research theory on biamping.

Gator

jdhdiggs

Watch out for active vs passive biamping
and anyone who eliminates frequencies and crossovers from the equations should be flat out ignored.

okiepolkie

jdhdiggs,

What is the recommended way to biamp, using two different amplifiers, with individual gain controls?

ahorvitz

Matt,
I've got a somewhat similar setup to you, in that I'm using the same (MKII) amp. I tried bi-amping with the amp running highs and lows. I tried it with the amp running the low and the receiver running the highs. And I tried the 5 amp channels to 5 speakers approach. At the end of the day, I thought it sounded best this way(bearing in mind this is a 50/50 rig). I have the fronts bi-wired, and it seems to me that removing the stock jumpers (probably same result bi-wiring or with DIY jumpers, but can't verify) is what (in addition to the power) made the difference. Your results may vary. Keep us in the loop as to what you settle on.

jdhdiggs

Okie:

Get one big **** amp and call it done...

Beyond that, experiment and have fun. There is no "recommended" way that I am aware of, all I can tell you is what I have done and some of the math on AC circuits and accoustic power...

The power point is what most people think they are getting when that not the best way to look at it. You do get more power, but it isn't double, or any where near that... To me, you do need 2 amps that have different charectoristics to really gain much. In my mind this is a question of SQ and not Watts.

How I think you should look at it as an oppurtunity to make the most of two seprate amps that each have a strengths and weaknesses against eachother. Ideally, you'd have a situation where you can pull the crossover to infront of the amp, but lets not bother with that. Let's just simplify things and say that you have a great amp that makes your tweeter sing but lacks bass authority due to power/feedback/damping issues, and another that can drive your woofs like no other but sounds clinical and dry. This is my case.

In this case, I use a line level high pass X-over to keep bass signals from contaminating the highs on the tube amp. This keeps the THD down a bit and increases the life of the tubes a bit (in theory). the x-over seems to clean up the signal a bit and helps with attenuation. Since the gains of the 2 amps are vastly different and neither offers gain controls, I used line level attenuaters before the tube amp to correct the gain to match the SS amp.

In the end, I have the warmth and tubiness for my highs and mids with the authority of SS for the low end. Best of both worlds.

Now would I get better results from one great amp? Maybe, Mark's BBQ sounded awfully close to my bi-amp setup on a similar set of speakers. To improve on Mark's amp, you'd really have to move into the $3,500 range street (JC-1's right?) price so having that level of performance for ~$1,800 is nice.

One amp is a hell of a lot easier to do right and ones with gain controls are easier to customize.

YMMV of course... Just don't electricute yourself.

Ahorvitz- Your results matched what I would assume the result would be with a majority of people but experimenting can be fun and educational.

MattN03

jdhdiggs wrote:

Okie:

Get one big **** amp and call it done...

I think that'll be what I do in the end anyways Not to mention, I want a 12 volt trigger so I don't have to manually turn the amp on/off.

MattN03

ahorvitz wrote:

Matt,
I've got a somewhat similar setup to you, in that I'm using the same (MKII) amp. I tried bi-amping with the amp running highs and lows. I tried it with the amp running the low and the receiver running the highs. And I tried the 5 amp channels to 5 speakers approach. At the end of the day, I thought it sounded best this way(bearing in mind this is a 50/50 rig). I have the fronts bi-wired, and it seems to me that removing the stock jumpers (probably same result bi-wiring or with DIY jumpers, but can't verify) is what (in addition to the power) made the difference. Your results may vary. Keep us in the loop as to what you settle on.

I bought AQ Type 8 speaker wire in a single bi-wire config and it helped only slightly. While waiting on the Diamondbacks, I ran the 8's off the Rotel with the Type 8 wires, and the 100 watts/channel only made a little difference over the 75 watts (90 watts in stereo) the H/K was putting out by itself. Bi-amping like I did last night made a much more noticable difference.

My main reason to put as much power to the 8's is an attempt to "tame" some of the brightness they have when listening to music. For H/T use their great, and I'm not really looking for an improvement in that department.

jdhdiggs

Did you recalibrate before and after bi/mono amping them. Bi-amping will can result in a slight gain increase and louder often sounds better.

MattN03

jdhdiggs wrote:

Did you recalibrate before and after bi/mono amping them. Bi-amping will can result in a slight gain increase and louder often sounds better.

No I have not recalibrated. I'm leaving for the weekend today, so I'll report back next week. Everyone enjoy Labor Day.

knownalien

i am using the 7500 to bi-amp the fronts. the difference is astounding and when your wife (like mine) takes notice of it then you know it is no error.