Need help with bi-amping.... McLeod? :)

Jack from Indo

I got an alpine H701 ready to add to my Focal K2P's and JL sub. I'm thinking of getting a 4 channel amp so I can bi-amp my front splits and take advantage of all it can do. McLeods posts on bi-amping and this alpine unit have made a lot of sense to me.

My installer here is recommending the same series amp I have (Steg K series, which I really like and do not want to change) but one that will only be 80w x 4. This is quite a bit lower per channel than the 155 x 2 I am currently using.

The K2P's are rated at 100 watts when used normally with the passive crossovers.

QUESTION:

Is 80 watts per channel enough, if I'm going to be bi-amping? There is a 4 channel amp that puts out 115 per channel and it's $200 more, and a bit more inconvenient size wise. Should I spend the extra money? My speakers sound so good with the 155 watts right now I'm afraid to make too many changes. I realize that bi biamping I will take some of the load off, but enough to go down from 155 to 80 per channel and not lose any SQ?

Please advise, and many many thanks for your help, McLeod, or anyone else.

exalted512

80x4 will give you more power than 155x2...

Bi-amping is putting each tweeter and each mid on its own channel. Right now youre tweeter and mid is splitting 155w, so essentially youre getting 78.5w to each speaker, with the 80x4, youll be getting 80w to each speaker.
-Cody

Jack from Indo

Cody, because the tweeters are so much smaller than the mids, and because you got that passive crossover in there that must do something to the wattage going to the tweets, wouldn't it be more accurate to say that the tweets are getting, for example, 50w of that 155, and the mids getting 105?

And thus, my question still has some relevance, anyway?

Please correct me if I'm wrong!

MacLeod

80x4 bi-amped wont be as much power as 160x2 straight wired. With the 160x2 youre not getting 80 to each mid and 80 to each tweeter. The power will go to where its needed and tweeters draw MUCH less power than midrange speakers. For instance, you send a 500 Hz tone thru your amp and all 160 watts will be going to the midrange. The difference isnt drastic but it is noticeable.

*disclaimer*
This is just as I understand it from reading articles and so on but as Im not educated in physics I could totally be talking out my **** here. Hopefully Brian can chime in and set me straight if Im off base.

That being said, 80x4 is plenty to bi-amp those speakers with. Id go with it.

Jack from Indo

Great, thanks. McLeod, If you got any tips on tuning the whole shebang, fire away. I'm gonna let the installer do what he wants for a couple of the presents on the H701, and then I'm going to do the rest.

I can't wait to sit in my car for hours tweaking the dang thing when I should be out contributing to society or doing something useful....

MacLeod

I start out with everything flat.

The first thing I messed with was crossover points. I roughly set them up to where they sounded good and moved on. You can come back to fine tune them later.

After that, the first thing I spent serious time on was the time alignment/phasing. First thing to do is either use a test disc or if you dont have one use an AM radio talk station. While the guy is talking flip the RIGHT MID in and out of phase. If his voice is in phase, it will be easy to locate and appear to come from a single postition. If its out of phase, itll be virtually impossible to locate and will lose low end response.

Once youve got the polarity right start with the time alignment. Just add delay to the right mid until his voice is in the center of the soundstage or roughly the middle of the dash.

After youve got the time alignment done then you move on to the EQ. Turn the sub off and EQ the front speakers only. When youve got them dialed in, then turn on the sub and EQ it. After youve got them all done, save it to preset 1 and then start playing with the crossover settings. When you find the settings you think you like, save it to preset 2 and then go back and forth between 1 and 2 and see which one sounds best.

Jack from Indo

Ok, cool. Understand, thanks heaps Mcleod, here's more!

1. Would I notice any difference to spend the extra $225 for the 115w x 4 to get more power, or would that be money wasted? Sorry to beat the horse. You said the 90w would be enough and I trust you, but I feel superstitious, lol, I guess, about going down from the 155 I have now. Irrational superstition maybe, but I feel it.

2. If I'm biamping, with the h701, I should set the time delay separately on every speaker, no? Or, is that not really necessary? After all, the 5 speakers are all slightly different distances from me.

3. re: your tips above: I'm confused. The right mid is the one furthest away. So wouldn't it be the LEFT mid that I have to add delay to? Cause without the delay the left signal gets to me quicker?

PoweredByDodge

Jack from Indo wrote:

Cody, because the tweeters are so much smaller than the mids, and because you got that passive crossover in there that must do something to the wattage going to the tweets, wouldn't it be more accurate to say that the tweets are getting, for example, 50w of that 155, and the mids getting 105?

To your ear it may sound that way, but technically it's not.

A passive crossover will (ideally) burn off 0 watts. While this is obviously not the case, the power loss through a passive crossover is wholly negligable. I would venture to guess off the top of my head somewhere on the order of 2% of power output at absolute worst.

Whether you use active or passive crossovers... if you play a 10 kHz note at 150 watts (relative to a 4 ohm AC-nominal reactance at that frequency, which it won't be, but you have to estimate off of something) -- then that tweeter is 'getting' 150 watts.

Crossovers do not split power -- they split information. The musical information beyond the cutoff frequency is scaled down at 6, 12, 18, or 24 dB per octave. Put two crossovers together, one highpass, one lowpass, with the same cutoff frequency (provided it's a Linkwitz Riley model -- spelling?) and you should have a perfectly FLAT response across the two speakers (the mid and the tweet)... where the 'lows' fall off at the same rate that the high's increase.

So... 80 x 4 into a pair of bi-amped components is not as much power as 150 x 2 into a pair of passively filtered components.

Personally, I believe in gobs and gobs of power, and let the crossovers do their job. I'm running on the order of 200 - 250 x 2 to my component set and I could never dream of listening to 'quieter' music, even with the precise tuning advantages I gained when I had the entire system tri-amped with an outboard 12 dB bypass to mid-woofers, 12 dB bypass to mids, and 12 dB highpass to tweets. The headache was no where worth the tiny advantage I got in precision... and to be honest, in my opinion (disregarding the 'way music is supposed to sound') I like it better with the high power and less options setup i've got now.

MacLeod

^^^ Yay! I was right!

1. Would I notice any difference to spend the extra $225 for the 115w x 4 to get more power, or would that be money wasted? Sorry to beat the horse. You said the 90w would be enough and I trust you, but I feel superstitious, lol, I guess, about going down from the 155 I have now. Irrational superstition maybe, but I feel it.

Having the extra power would be nice. Its like having a whole lot of horsepower. Yeah you dont really need 600 horsepower but its nice to have when you do. If you can afford the 115x4 amp and make it fit, then get it. Just be VERY CAREFUL with gain settings and volume because that extra power can also fry those speakers a lot easier.

2. If I'm biamping, with the h701, I should set the time delay separately on every speaker, no? Or, is that not really necessary? After all, the 5 speakers are all slightly different distances from me.

You will use TA on all speakers except the one furthest away from you and your sub. The sub actually needs to be heard first to keep it from pulling to the rear. You hear it and then a split second later the imaging cues from the mids/highs kick in and you "think" you hear it from the front.

3. re: your tips above: I'm confused. The right mid is the one furthest away. So wouldn't it be the LEFT mid that I have to add delay to? Cause without the delay the left signal gets to me quicker?

Youre 100% right. Im a dumbass.

I have a bad habbit of just typing whatever is on my mind and immediately hitting submit without reviewing it and I often have type-o's like that.

Jack from Indo

Sorry to be a stickler for detail (pun intended) but here is what is still confusing me:


You will use TA on all speakers except the one furthest away from you and your sub.

Now, um, the speaker furthest away - the signal from that under normal circumstances is going to be the one that takes the longest to get to my ears, so seems to me that would be the one you add the least amount of delay, if any, to it, and the one closest to the ear is the one you need to add more delay, no?

PoweredByDodge

i believe the furthest away is left alone (no delay), and then all others are delayed with relation to that furthest away one.

MacLeod

Ideally you want NO delay on any speakers because this messes with things. Although youre delaying the signal from the close speakers, youre not doing anything to change their intensity that would normally be affected by increased distance.

Also youre trying to tie in the speakers so that they arrive at the same time at your ears. So you take the furthest speaker (usually the right mid) and leave it at 0 because its hitting your ears last and doesnt need any delay. Next will be the right tweeter if its mounted apart from the mid. Usually this will only need .1 which is basically nothing so you could leave it alone. Then you move on to the left side.

Phasing can also affect TA. For instance, my left tweeter is further away than my left mid BUT Ive only got .25 ms delay on my mid and .9 ms on the tweeter. However I have my left mid 180 degrees out of phase and both tweeters in phase.

So youre going to have to play with phasing too as that can make a huge difference. Just do like I said with the AM radio talk station and flop the polarity and see which sounds best.

Its best to drop the level of the tweeters down the whole 13db in the crossover so that youre JUST listening to the mids. Then drop the level of the mids all the way down so that youre just listening to the tweets.