2 amps, 7 channels. How 2 Configure?

[davidtwotrees]

I am in the midst of a most excellent dilemna. I have just purchased an Acurus A250 that is in the mail. Two channels of excellent clean 250w power.
Which effectively doubles my current setup with my Audio Refinement Multi 5, which is 125w x 5 channels(http://ultimateavmag.com/surroundsoundpreampprocessors/145/ ). The AR(yba) is an excellent amplifier, but I wanted to take the plunge and double my front watts. Here is the dilemna. I have the Mordaunt Short THX 500 series of 5.1 speakers, all biampable. The fronts have a 5"midbass, 5" mid range, 1" tweeter, and a side firing 10" powered 100w subwoofer. With my two amplifiers, I will have 7 channels of amplification. Should I just power the fronts with the new Acurus A250, biamp the center with the AR, and run one channel to each surround leaving a dead channel? OR, power the front's midbass with the Acurus, the midrange and tweets with the AR, biamp the center with the AR and one channel each for the surrounds?
I will listen and compare, but wondered if the sage pundits here might have some definitive insight into the whole thing.
I don't own an spl meter........I wonder if that would be a good way to measure the fronts output amped with the A250, or biamped with both amps running the fronts............?

 

[Adam]

No sage advice from me, but I wanted to say...that is a most excellent dilemma indeed!

 

[AVRat]

Option #1 and p/u an SPL meter you slacker!

 

[Seth=L]

I would use the Acurus for the fronts and leave the rest to the AR.

I got the implication this was a 7.1 system, please correct me if I am mistaken.

 

[davidtwotrees]

Nope, Seth, 5.1 only. When I said 7 channels I meant 7 available amplifier channels to go into 5 biampable speakers. And the two surrounds are really a non issue for me.........

 

[davidtwotrees]

Option #1 and p/u an SPL meter you slacker!

I know, I'm a bum......but they're almost sixty bucks at Radio Shat and I keep looking for a used one on ebay and they never come up...........

 

[audiofox]

You might look into biamping if your speakers are appropriately wired or bridged amplifier channels if the AR supports bridging. There is a way to bridge without having the feature internal to the amp, but I don't remember exactly how to do that anymore. You need to power combine two of the channels together so they add together power-wise, which probably means some sort of phase control for the channels to be added so the phase of the two amplifier signals add properly. I know how to design this for TWTA or SSPA amps for a satellite transponder transmitter, but the frequency range is a bit too high for your needs. -)

 

[Seth=L]

I know, I'm a bum......but they're almost sixty bucks at Radio Shat and I keep looking for a used one on ebay and they never come up...........

Your radioshack sucks, I think I got one from there for about $25-30, the digital one was the expensive one.

 

[davidtwotrees]

Well, I solved the problem. I liked the A250 so much, I bought another Acurus A250. So one A250 to biamp each front speaker, and the Multi 5 can handle the center and surrounds. Ok. I AM NOT BUYING ANYTHING ELSE FOR THIS SYSTEM!!!!!

(well......I will start saving for some new fronts....focal, thiel....)

 

[Seth=L]

Well, I solved the problem. I liked the A250 so much, I bought another Acurus A250. So one A250 to biamp each front speaker, and the Multi 5 can handle the center and surrounds. Ok. I AM NOT BUYING ANYTHING ELSE FOR THIS SYSTEM!!!!!

(well......I will start saving for some new fronts....focal, thiel....)

I thought I would crack down on myself and stop buying a long time ago, I was wrong to think I could do that, because it is impossible. I have learned to save money where it counts though.

 

[davidtwotrees]

I thought I would crack down on myself and stop buying a long time ago, I was wrong to think I could do that, because it is impossible. I have learned to save money where it counts though.

Yeah, I know....I don't drink, I don't toke, I don't smoke.......so this is my habit. I do like my set up now, or when the other A250 comes next week and I get this all set up right. I want to set the the A250's on the floor, one next to each front speaker........kind of like mono blox but in stereo....I have some TV trays, four to be exact, that never ever get used. I am going to break them down, glue two tops together and make amp stands for the A250s.
I guess they will over heat if you just set the amps on the carpeting.....

I keep meaning to ask someone why glass is bad to set components on. My rack looks really sharp but is all glass shelves.........

 

[jcPanny]

Amp upgrade

David,
Nice amp upgrade, however, I doubt your MS speakers can handle 250 Watts, let along 500. Also, you would need an external crossover to take full advantage of bi-amping the mains.

With multiple amps in your system, you will definately need on SPL meter, or mabe a measurement mic and RTA software to setup your system properly.

 

[davidtwotrees]

D'OH.....a little help here.....

D'OH!
Smiles. Never one to look before he leaped, TwoTrees realized there was no water in the bottom of the pool....

Ok.......My MS 502 fronts, (and the MS504 Center) specs are:
90dB Sensitivity, 4 Ohms impedance nominal, 15w-150w rms

or go here.......MordauntShort

The A250 amp is rated at
250 w per channel continuous both channels driven into 8 Ohms
350w per channel continuous both channels driven into 4 ohms

Is even one amp gonna work or will it be too much....I don't drive my speaks for hours on end, but am not above cranking it up for a scene or a song...?

 

[Seth=L]

D'OH!
Smiles. Never one to look before he leaped, TwoTrees realized there was no water in the bottom of the pool....

Ok.......My MS 502 fronts, (and the MS504 Center) specs are:
90dB Sensitivity, 4 Ohms impedance nominal, 15w-150w rms

or go here.......MordauntShort

The A250 amp is rated at
250 w per channel continuous both channels driven into 8 Ohms
350w per channel continuous both channels driven into 4 ohms

Is even one amp gonna work or will it be too much....I don't drive my speaks for hours on end, but am not above cranking it up for a scene or a song...?

You know, it is said time and time again, there is no such thing as "too much power".

While the speakers may be rated for a max of 150 watts the extra beef still helps. To be honest it isn't always about the watts, you have to consider amps(amperes) as well. If the nominal rating of the Mordant Shorts is 4 ohms and they are a good grade speaker (they are considered to me, but I have never listened to them to hear for myself) you can expect impedance drops that a receiver or many lower power amplifiers would fall short at higher volumes. The Accurus has headroom, lots of headroom, believe me it puts out short bursts of wattage over it's rating and the speakers take it and keep going. If you feed 250 watts constantly you may have a problem, but how many watts you might be using during one song could vary between 20-100 watts or 50-300 watts, crazy numbers. Most quality speakers can handle those short bursts of power, and those bursts are important.

I hope you enjoy this fine addition to your sound system.

 

[davidtwotrees]

Thanks, Seth. This just in from Mordaunt Short Support....
"The power rating of an amplifier is, of course, the maximum power output of the unit. So long as the amplifier is used sensibly, this will not cause a problem....If anything, an amplifier with a higher power rating than the speakers is preferable to one with a very low power rating, as a more potent amplifier will deliver a more controlled signal, reducing the chances of spikes or abnormal signals damaging your speakers.I have used various different amplifiers with my THX pack, varying between 100 watts per channel, up to 2 250 watt units biamping them, and have had good results doing this.
Best Regards Adam Shaw MS Support"

I have read up on BiAmping. Apparently unless you use an external electronic crossover, you are not biamping, but rather bi wiring. Unless your speaks are set up for biamping.......I am not sure if my MS's are. They mention biwiring in the manuals, but the tech support mentioned biamping his very same speakers.........So, JCPanny, what will happen to my speakers if I use these amps with them?

 

[Seth=L]

In concerns to having too much power it is likely that you will have problems, nothing bad will happen to the speakers unless you push them to a breaking point, which is possible but not likely that you would do so. I think your speakers would become uncormfortably loud before they would become damaged from overdriving them. Underdriving speakers is far more dangerous because a clipping amplifier is outputting a very difficult signal that can cause damage to speakers. Clipping signifies a square wave and speakers aren't intended to play square wave type signals and it is very hard on them to do that.

Bi-amping, your speakers are bi-amp capable. Bi-wiring is connecting a speaker to one output terminal at the amp and using two wires from the output terminal to each set of terminals at the speaker. Bi-wiring is nearly if not completely pointless, bi-amping can be useful (no external x-over is required, internal components still used unless there is a bypass switch). Bi-amping is practical if you can use two seperate amps or a multi-channel amplifiers with completely modular design (seperate power supplies for each channel and the only thing each channel shares is the AC cord). Most amplifiers, as said before can direct most of their power to any given channel.

 

[jcPanny]

Amp Power

David,
Your new amp should be fine with the MS speakers. Note that the speakers will reach their limits before the amp does and it should be pretty obvious in the form of distortion. Like you pointed out, 1 amp channel (350 @ 4 ohms) is more than enough power for your speakers, so 2 bridged amps, biamping, etc. is over the top IMHO. Your money would be better spend on acoustic pannels, HD-DVD player or other upgrades to your system.

 

[AVRat]

Ditto jcPanny's comment.

 

[davidtwotrees]

Whew. I thought I was dead in the water there. Ok. My speakers should be fine.....I will try this setup. If it is too much or over the top, I can always sell one of the A250s. They are really a bargain, imho, at $450 delivered.

My box of Owens Corning 703 showed up the other day. I am gonna buy an spl meter. The other amp should be here by end of week. Things are looking up at Chez TwoTrees. Wish I had one of you talking heads here to help with the set up......

 

[PENG]

Seth=L summed things up very well!