I'm trying to decide between a home theater system powered by either an Axiom M80 centered system, or Brand X. I say Brand X because I've done the research, and I know what to expect if I mention a specific name. I'm not here for that. I'm here because I have a power question.

My theater room will be probably about 2000 cubic feet, give or take, and sealed. The room will be well treated with acoustic treatments placed from a home theater perspective. (dead front wall, broadband absorption along the sides up to ear level, rear treatments, bass traps) So for the purposes of this query, I will probably be most interested in the Anechoic sensitivity rating. (don't worry, I'll be trying to keep the RT60 within a reasonable range)

Okay, with the background info taken care of, here is my question. How much power do I need to run an M80 system at reference levels? Reference being defined, as I understand, by 105db peaks at the listening position from each speaker. (115db from the sub. I'll have two SVS PB13Us on task for this)

I believe I have come up with the correct answer, but want to have my numbers checked.

Given the lowest sensitivity of 91db anechoic, and a seating distance of 3 meters, the Crown Audio Amplification Calculatgor tells me I need 451W of power to achieve 105db, and have 3db of headroom left over.

Based on this calculation, I have come up with two possible amplification options for an M80 system:

Axiom Audio Reference System 1

M80 Twoers at 91db @ 1w/1m
VP180 Center at 91db @ 1w/1m
QS8 Surrounds at 94db @ 1w/1m (2 pairs)
Yamaha RX-V765 Reciever (pre-outs going to external amps listed below)
Emotiva PMA-7350 350WPC 7 channel amp $3000

So, bearing in mind that I need 451W to play reference, and have headroom, the M80 and VP180 are both 4 ohm speakers, and the PMA-7350 is capable of 4 ohms. So, given that 4 ohm wattage is usually higher, the Emotiva should be able to give me 105db and still have some leftover headroom.

Will this provide reference listening levels without clipping?

Axiom Audio Reference System 2

M80 Twoers at 91db @ 1w/1m $1628/pr
VP180 Center at 91db @ 1w/1m $850
QS8 Surrounds at 94db @ 1w/1m $1316 (2 pairs)
Yamaha RX-V765 Reciever (pre-outs going to external amps listed below)
Emotiva XPA-2 300W @ 8, 500W @ 4 $799
Emotiva XPA-5 200W @ 8, 300W @ 4 $899

This is $1300 cheaper, but at the cost of headroom. The XPA-2 should have the headroom to drive the M80s at 4 ohms. But the XPA-5 could be an issue. The center will call for 226 watts of power at 4 ohms to achieve 105db. The XPA-5 is rated for 200W @ 8, 300W @ 4 ohms. That's only 1db of headroom for the center. The surrounds are 8 ohms, and will call for 113W to drive them at 105db. That leaves 2.5db of headroom.

So, will this system also be enough, or is it too borderline? Which of these setups would be the most balanced and cost efficient, without compromising the ability to play at reference volumes with no distortion?

Thank you!

I'm not certain about your figures (I'll leave that to Chris), but I would advise looking somewhere in addition to Emotiva. Budget amps (for lack of a better word) are just that--budget. If you're looking to push that much power, I'd be looking at Outlaw (maybe), Parasound (definitely), Rotel, ATI, Bryston, that sort of thing.

Jeebers! that kind of power in a 2000cf room is going to be loud!

Some of the pro-amps are connect friendly for HT use, if you don't mind occasional fan noise on quieter passages(unless you swap it out for a quieter fan). Of course, at those kind of levels you wouldn't be concerned about noisy fans.

You sound like a candidate for horns or some type of pro speakers as it seems high sensitivity and efficiency seems to be your main concern. That said most won't have the fidelity of the Axiom system. I would suggest buying as much power as you can afford. Maybe even look into some pro amps. The M80's are really geared for very high power handling. The limit will be the amp feeding it.

I've heard M80s playing at >105dB sustained. They can handle it just fine. The dude was powering 5 of them (!) and 2 QS8s with 4 Parasound Halo 500 WPC 2 channel amps.

I have reached 105DB continuous in my 20x13 room with a Rotel RB1080. I like it loud but that is to loud for me. The amp could handle it well, the M80s handled it just fine but my ears didn't do so well.

Emotiva has decided not to release the Emotiva PMA-7350 350WPC 7 channel amp $3000. I think you will have to select alternate power.

It's going to be hard to find a 450 Watt @4 Ohm amp, that isn't really expensive. The price is slightly justified too, because 200 Watts isn't too hard to do, maybe 300 into 4 Ohms, but once you start nearing 500 Watts the design work that goes into amps of that caliber has a cost.

The Behringer EP2500 will do that into 4 ohms and then some. It will also provide about 1000 watts into 2 ohms (verified by 3rd party testing). These would be the most cost effective solution and offer better performance than the Emotiva but you would also have fan noise to deal with which will be an issue if you do any low level listening or have to mod the fan on the unit(s).

Behringer can be hit or miss and quality issues can be a problem with their products just so you know.

The fact that Behringer has quality issues backs up what I'm saying. It's not cheap to build a rock solid 500 Watt amp.

The ButtKicker LFE amp does 1000 Watts into 4 Ohms, and 2000 Watts into 2 Ohms. But you don't want to listen to it through a speaker.

The EP2500 is not one of their products that is known for a lot quality issues. Their product line is hit or miss, the EP2500 is more hit and its build quality and performance has been verified by third parties. It's just a general tidbit about Behringer that one should be aware about. Some of their products offer exceptional value, the EP2500 being one of them. Some products are complete junk. Behringer has a love/hate relationship with the professional crowd.

I really need to go crash, but I'll throw out there that many have pointed out that Crown Calculator to have errors as it pertains to HT. JohnK and Alan will likely be along with the answers....

DanLW,

Here is some data on the EP2500.

8ohms

http://www.avsforum.com/avs-vb/showpost.php?p=10753603&postcount=56

4ohms

http://www.avsforum.com/avs-vb/showpost.php?p=10753638&postcount=57

2ohms

http://www.avsforum.com/avs-vb/showpost.php?p=10755537&postcount=64

2000 cubic feet?? That's not that big. 16 X 16 X 8 is 2048. You can go deaf with a simple AVR pushing 100 WPC in that room.

Dan, welcome. First, forget about the Crown calculator. It has no relevance to use in reflective home listening rooms and grossly overestimates the power necessary for such use.

I calculate as follows: use 90dB as the 1 watt sensitivity for the M80 at 1 meter. 100 watts would result in a 110dB output at that distance. Since, as Dr. Toole and others have reported, sound level in a typical home listening room falls off(taking into account both direct sound and room reflections)about 3dB per doubling of distance, at a 10' listening location the 100 watts are used for about a 105dB listening level on brief split-second peaks. Typical receivers rated anywhere in the 100 watt area are ample. Relax and enjoy.

Dan, not sure what your point is about mentioning another brand of speaker, there are lots of good speakers out there and you will find unbiased feedback, as long as your statements about those brand X speakers are factual.

""Deaf" is for wussies. Very low bar. My goal is to make my defibrilator explode right outta my chest. If I can still hear anything when I finally need one.

More the better!

You are soooooo right! C'mon! It's Rock and Roll!

my HT room is 15 x 16 x 8 and the 16 side opens via a 4' passage all the way to the other end of the house which is 30'. i have an emotiva XPA-5 powering my front 3 which includes a pair of M80v3's and a VP180v3 center.

if i have my volume about 1/4 of the way up while watching a blu-ray movie, lossless (action movie) it's loud but good, just where it's tolerable and not ear damaging. if i turn it up to 1/2 the way it's almost deafining and i'd have to go all the way back to the other end of the house,at the 30' wall to stand it. 3/4 of the way up there is no way i can stand it even at the 30' wall, it actually hurts my ears, head, it's just too damn loud. if i was playing an SACD and turned it up 1/2 it would crack my skull--i tried it with John Mayer "heavier things" DSD about 1/2 way and i had an instant headache, the music was crystal clear but it really hurt my head and i wasn't near reference levels either.

think quality and not quantity. the 80 series will take everything you have that you can give it and turn it into incredible audio (quality and level wise) i dont' like loud music, but it's nice to know that if i wanted to or for some reason needed to, i could crank it a bit and it would loosen fillings in my teeth!

Oh yeah, the XPA-5 barely just gets warm to the touch even after playing movies and gaming at the 1/4 volumes for several hours in a row. the other two speakers on the XPA-5 are a pair of QS8v3 surrounds. I have a pair of M2v3's doing surround back duty powered by an emotiva UPA-2.

I know not everyone likes or loves the emotiva amps but they have always done right by me and they have powered all of my Axiom speakers in my HT 7 channel system without a problem or exception; no excuses either and my front 3 are crossed over at 40hz so i do put that amp to work during movies! still, barely warms up!

best of luck, hope you can find what your looking for. please keep us posted.

You might actually want to use the in room response of 95db for your calculations, it makes quite the difference. I suspect your Yamaha would be sufficient on it's own as I can hit 105 db peaks easily with my Denon 3808 in my ~4000cf room and I am sitting 12 ft away from my M80s with a single PB13 ultra.

I know my M80's actually shut off my Sherwood at higher volumes playing BD tunes , yet to test the Onkyo.

Wow, thanks for all the replies! I would have responded much earlier, but my internet was down for most of the day. So this will be a long reply.



I double-checked, and it seems to be working correctly. If I put in 91db as the sensitivity, 91db as the desired listening level, and 1 meter as the listening distance, I get 2 watts. (3db headroom) This is correct. If I make the distance 2 meters, I get 8 watts. This falls in line with the rule that with each doubling of distance, 6db is lost. (I know, you have 3db per doubling... I'll get to that) So at 4 meters, we would be 12db down. So, we should have 32 watts, which is what the calculator gives me. At 3 meters, we should be 9db down, and require 16 watts. The calculator gives me 18 watts, but I suspect that is because they are using a bit more of a complex formula.

So, 91db at 1 watt at 1 meter. Move 3 meters away, so approx. 9db down. 82db. I want 105db, which is 23db higher. So, 1*10*10*2=200. Plus 3db for headroom, 400 watts.

But why am I using 6db considering...



I'm sure that is correct, for the typical home listening room. The typical home listening room is a completely untreated acoustic "hall of mirrors". If my room was typical, it would have the .45 second RT60 I measured before I started putting my treatments up. But now that I have done the front wall (the Air Force deployed me to Afghanistan before I could do the sides, back, and bass trapping) my room's RT60 is now .25 seconds in the 250-10KHz range. I know that sounds low, but from some of the charts I've seen, I should be shooting more for .21 seconds.

So, my room is probably going to have a greater than 3db attenuation per doubling of distance. If I were home, I'd whip out my SPL meter, play pink noise out of a speaker, and I'd have an actual measurement for you. Perhaps that is what I'll have to do when I get home. That way I'll have a better idea of exactly how much amplification I need.

And here's some antecdotal observations. We (me and my wife) can now listen to movies with the volume turned up louder than before. I'm fairly certain this is because of the reduced reflections (i.e. noise) in the room. I'm probably butchering the term signal to noise ratio, but basically with less reflections, the room's signal to noise ratio is better, so we can play louder without the "noise" being as loud.



I'll look into the Behringers, but this is the first I've heard of quality issues with the Emotiva amplifiers. (their signal processors are a different story)

I found something disturbing on Behringer's EP2500 page, however...



Wha? GAA! EVIL! EEEEEVIL! THE POWER OF CHRIST COMPELS YOU!

Sorry... seeing as I plan to get two PB-13 Ultras, and plan to run them in sealed mode, that statement... I could go on quite a rant about that.

Of course, I know I wouldnt be routing the LFE channel through the external amp, but just the thought that an audio company considers low frequencies distracting... I need to wash my eyes after reading that.

Anyhow, their price doesn't seem bad. I'd definitely fan mod them, though.



Where is reference level on your amplifier? I'm guessing it would be somewhere at the 1/2 way point. At least, in my calculations, 105db would be somewhere around the half power point. Of course, that's 105db peaks. The whole soundtrack shouldn't be at that level. I'd be interested to know what SPL white noise calibrated to -30db plays at for those settings.



Again, I wish I was at home so I could check to see where my room stands. I'll have to experament with my current speakers and see how they measure in relation to their rated sensitivity. Hmmm. But I'm not sure how to assure I am sending exactly 1 watt to them without buying expensive test equipment...

So, to conclude, looks like I'm going to have to do some measurements in my room to see which set of calculations to use in determining how much power I will need. It's likely going to be somewhere between 6db per doubling and 3db per doubling of distance, since my room is not anechoic, nor is it a typical listening space. Well, I have 5 1/2 more months before I get back home. So I'll have plenty of time to get more educated.

In the meantime, for those of you with well treated theater rooms, I would be curious what db loss you measure per doubling of distance. Or perhaps somebody already has such information?

Thank you!

The dB loss you measure per doubling distance would be the same in any situation. Proper treatments will assist in a flatter frequency response within your room (bass traps, panels) however most people with properly furnished rooms will be fine. You will come to a point where you will rather just enjoy the system versus worrying about 1-2dB's which you can't perceive anyway.

The thing is, people on this site are saying 3db per doubling, and elsewhere it is 6db per doubling. At 3 meters, that can mean either 4.5db down or 9db down. 4.5dbs makes quite a difference, considering it can mean the difference between needing a 200W amp and a 500W amp.

Ah, another question I forgot to ask in the last post. How much headroom is generally recommended? Is 3db a good rule of thumb? If it is more like 1 or 2db of headroom, is that sufficient, or flirting with disaster? I mean, let's say I know I need 226W to get to 105. And I calibrate my system so that 0 on the volume knob is reference. Would getting a 250 or 300W amplifier be "safe", or should I really go for that 3db of headroom, and get a 500W amp?

I guess the real question is, how many movies have peaks above reference? Properly mastered movies should peak out at 105db... but it seems there is no shortage of movies with bad mastering...

Truth is i have no idea where reference level is with my amp. i don't get that deep into this stuff. i do know when something is too loud for me to enjoy myself! perhaps someone else with an emotiva XPA-5 amp and my pre-amp know at what point you hit reference level. when i watch the news on tv the volume is set at 40 absolute. when watching movies or sports the volume is between 50 to 60 absolute or -32db to -22db relative. the settings just listed are great/perfect for me/us watching movies and it never gets louder than mentioned or it's unbearable! on my preamp, to hit 0db, relative (which is 82 absolute) that's about at the half way point and it can go higher up to 100 absolute or +18.0db relative which are the max volumes and no, i never want to make a mistake and somehow hear that!

The point at which you hit reference level would be dependant on the output voltage of the pre/pro and that voltage varies between manufacturers and even models within the same company.

DanLW, I may hive missed this, but why are you even trying to achieve 'peak reference level 105db'? I know movies are mixed for peaks to reach 105db but that is also with normal noise in the 85 db range which is actually quite loud and not many people listen at this level in a home theater. I believe I listen to movies with normal range around 75-80db with peak levels around 95-100db.

Pretty sure he said peak at 105.

You would be correct and that was what I meant, I have now corrected it.

What, pray tell, is a properly finished room? What if I really like concrete furniture??

You should upholster the ceiling.

Fred Flintstone had great acoustics in his home.

He was one of the pioneers of Hard Rock.

Speaking of Fred Flintstone, why did he celebrate Christmas?

To sell more merchandise.

That's a good one! Because Freddy was BC.

That's BCE, you anti-revisionist!

Also, I believe that Moses' tablets were made for God at Fred's Quarry. They were given to Deputy Dawg for safe keeping, until Bambi found them in the forest and brought them to King Arthur.

At least that's what I kinda remember the 3rd grade nun telling us.

Thank you for your service, Dan.

"Deputy Dawg"?? that is going back. You probably remember "Snagglepuss" and "Quick Draw McGraw"?

Bing, bing, bing! Ricochet Rabbit!

Baba looey and Huckleberry Hound.

Anyone remember a (very) silly cartoon called "Batfink"?

Exactly. (and I know you're replying back to Solardadd at this point) It used to be, amplifiers went up to 10. Then, Spinal Tap found an amplifier that went up to 11, meaning that it was "one louder" than everything else. Not to be outdone, other amplifier companies made amps that went to 12...15...30, etc. Finally, some genius got the idea to create a standardized volume control scheme. So now we have amplifiers that go from 0 to -100 (or so) db. Ideally, any amplifier set to -20db will play at the same volume as any other amplifier at -20db. But this will not happen unless both amps are calibrated. Ideally, an amp's auto-calibration routine (if equipped) will set this for you. Or, you can get a SPL meter from Radio Shack, and some white noise recorded at 30db below reference, and adjust each channel for 75db at the listening position.

Yeah, for most people, that's way too involved. But if you're a geek like me who actually has fun running sweeps with Room EQ wizard, then knowing exactly what your system is outputting becomes relevent.



The reason I want the ability to go to reference is because I'm trying to put together the last speaker system I'll ever own. I don't want to be one of those people who spends $5000 every couple years on a new set of speakers. I want the peace of mind that knowing what I get is the best. Not the best in terms of quality (sure, you could spend >$100K on a pair of speakers with .00001%THD), but the best in that it sounds good, and is capable of playing well at levels put forth in an industry standard, and as such there is no need to get more. Once I get my speakers and amplifiers, I want to be done. No reason to upgrade, because I am there. Then all I have to do is worry about replacing bulb in my projector (though I'm hoping LED will be cheap enough by the time I'm ready to get a new projector).

I guess it's more for peace of mind than anything else. I don't want to always be wondering if my speakers would have sounded better if I got a 500W amp instead of a 200W amp.

Of course, once I retire, and am done moving, I might go ahead and augment my system with a DIY subsubwoofer to get me deep into single digit response... but hopefully by then Thigpen will be producing reasonably priced radial subs.

Yabadabadooo!

I hear ya. It isn't so much as a need as a desire and only one chance to get it right the first time. This is how I am also.

Right now I am looking at the DIY amp from ClassD that SRoode put together or D-Sonic with a 500W 3 channel amp for the mains, as well as the usual suspects, Parasound, Rotel, Bryston etc.

Exactly. I've been actively researching for probably 8 years now, ever since I heard a pair of Klipsch RF-7s in a store, and how much better they sounded than any other speaker in the lineup. (of course, now I realize that may have been because they were playing louder, and the louder speaker almost always sounds better) Ever since then I realized that for serious home theater sound, I would have to look at towers. (all the towers sounded better than the bookshelves)

Now I am at a point in my life where I am almost out of debt. And it's amazing how much money one has to spend once they are out of debt! I intend to buy nothing on credit - It will all be purchased with cash in the bank. And so, like you said, I want to assure that I get it right the first time.

I've gotten lots of excellent info and stuff to think about from this thread. So I may as well let everybody know that my Brand X is a system centered around the Klipsch RF-7IIs. I know, horn loaded, bright, harsh... like I said, 8 years of searching. But the Klipsch defenders will say that while their lower end stuff which most people have heard can be described as such, their higher end stuff (RF83 line, and again, the RF7s) aren't like that. I have considered the Paradigm Studio 100 series, and considering that they cost as much as the Klipsch, and require the power of the Axioms, I have written them off my list. That, and I have read that the Studio 100s and M80s sound similar. Also, Paradigm seems to be focusing on pretty looks and astetics, and that makes me wonder what I'm really paying for. Briefly looked at AV123, but wasn't impressed. Was interested in SVS' new offering, but they have taken that off their page since it's release is nowhere in sight. Looked at RBH, but they don't have what I need at a price I am willing to pay. Axiom still stands as an excellent quality ID brand. And I am starting to realize that even the Klipsch system will require an XPA5/XPA2 (or equivalent amplification) since portions of their frequency response dip into the 2 ohm region, and therefore require a lot of current delivery capacity.

Now, I don't want to turn this into an M80 vs RF7 thread. I've read plenty of those, and have come to the conclusion that I will just have to hear them both for myself. However, I've encountered a setback. Did some research on shipping, and the M80s are too big to ship to an APO. The only way to get them to me is to have them shipped international, and that costs approx. $2017 for a pair of M80s after all is said and done. ($1674 base price + $268 VAT tax + $75 duty) I have E-mailed Axiom and was told that this is correct, and that Axiom does not accept VAT forms. (A VAT form is a form US Military personnel in Europe are able to use in order to not pay the 16% VAT tax)

The good news for Axiom is that even though Klipsch has dealers in Germany, they charge $3800 Euros ($5428) for a pair of RF-7IIs. If they accept a VAT form, that brings it down to $4559. But that's still $1361 over the US price of $3198... and even if I walked in with cash on hand, I doubt I'll get a 30% discount out of them.

So, looks like I'll just have to wait until I get back to the US in 3 1/2 years, and I'll just suffer with my Infinity Primus 150s...

Okay, here's an idea. what if I purchased a pair of M22s and a pair of RB-81 IIs. (Those ARE small enough to go to an APO.) Do you think that would be a fair comparison of the Axiom vs Klipsch sound, or would I be comparing apples and oranges if I compared those two in order to make a decision on which towers to buy? Originally, I had wanted to go with bipolars all around for 7.2 surround, but I suppose I could use monopoles for the back channels. Or, I could use them for the "presence" speakers. Hmmmmmmmmm....

Sorry that my posts are so long! It's kinda my way of thinking out loud. I actually figure a lot of stuff out in the course of typing these posts of epic proportions!

I don't know anything about the Klipsch lineup, but the M22s would be a good representation of the Axiom sound (almost the canonical representation!)

The M22's are VERY representative of the Axiom sound as all of them use the 5.25" for midrange playback and share very similar SQ.

The only Klipsch that I heard were the RF82 and RF62 and also the horns didn't bother me, I thought they lacked in the midrange area. I haven't heard the RF7s.
It looks like you are over analyzing everything. No matter how much you read, it will be no substitute for hearing the speakers. I know that it might be difficult in your case but as others have said, the M22s and even the M2s will be representative of the Axiom sound and as for Klipsch, you might be able to listen to them at the dealer. Good luck.

Dan, by your own suggestion, it might be the best idea to go with the M22s/Klipsch equivalent bookshelf, since you can always switch them to rear channels(7.1) once you decide or are able to go with towers up front. You may feel towers are unneccessary in the end scheme of things but knowing you have the option of using them as rears may make your decision easier.

Well, sounds like the M22s it is. For Klipsch, I will buy their equivalent bookshelf so I can have them both in my room so that I can listen back to back. I've been to dealers but between differences in rooms and audio memory, I'll just have to have them both and try them both out. Bookshelves can be shipped APO, so the shipping issue will not be an issue.

How do you think I should set it up? I'm thinking I'll hook one set up to the front outputs, and the second set will be hooked to the B zone outputs. Everything will be level matched, and I'll cross them both over at 80Hz, above their cutoff, so that the differing bass extension will not be an issue. I will assure the reciever's settings are identical for both speakers with the exception of distance. I'll try to get them both acoustically centered. I'll set them up in an AB AB configuration so that they both have identical spacing. Before critically listening, I'll work on positioning both sets for optimum soundstage. I'll also have friends over to listen to try to overcome any bias I may have on my part. Heck, I'll even try to get the same color and have my wife make the connections to the speakers so that I don't know which ones are playing. I want to try to make the playing field as level and objective as possible.

Any other recommendations?

Seem like a lot to go through to make a decision? Maybe. But I'm a geek - I love this type of thing!

The wait is gonna kill me... (not literally, I hope) 5 more months in Afghanistan (hence why I have so much time to think about this kind of stuff), then a new baby in Sept, then hopefully by January, time to make it happen! At least I'll have plenty of time to select sample music and movie scenes!

Initially I would set them up strictly as stereo pairs, one set Axiom then the Klipsch. Play some music with each set and take notes as to what you are hearing, ie, too much treble, muffled midrange etc. be sure to try varying music styles. Once that is done sit back and read your notes, you might be surprised by what you are hearing between the different speakers. I would then do an A/B comparison as you are suggesting to really hammer home the differences or similarities. One suggestion would to have some else switch between the 2 speakers on the amp without the listener knowing which set is on, this makes it about as blind of a listening test as possible without going through coverings for the speakers etc.

Dan, first let me express our thanks to you for the service that you're rendering our country and extend best wishes to you and your wife for the upcoming arrival of your new baby.

Your plan to test the Axiom and Klipsch sounds good, but I'd suggest that the RB-61II would be a closer match to the M22 in overall size and cost. Yes, a key difference will be the significantly higher sensitivity of the Klipsch, and you're aware of the necessity for level-matching. Your setup description sounds fine, but I didn't follow why the distance settings would be different.

I was going to respond re the Crown calculator in your other thread, but was delaying because you'd indicated that you might have time to test with an SPL meter, and those results might be interesting. Although I didn't doubt the findings of Dr. Toole and other authorities on the point, I did check for myself a couple years ago. If you'll able to do this at least at 1, 2 and 4 meters you may be surprised to find that the reduction in sound level is indeed far less than would result from applying a 6dB per doubling of distance formula, which is of course theoretically correct, but applies only to an omni-directional sound source in an anechoic environment.

Of course, the Crown calculator is mathematically "correct" in performing the simple calculations under that formula, but as was said, that isn't the real world of home audio. You may not have read the more extended Crown discussion of power requirements published in conjunction with the calculator here . It clarifies the point that the calculator results don't apply to listening rooms at home as distinguished from professional applications out-of-doors, but unfortunately that rather key point is somewhat buried near the end under "Other considerations". They suggest adding a 6dB correction to the results, which you'll note would reduce the calculator's number to 1/4th of its previous value(Axiom uses 4dB for a similar purpose in its sensitivity ratings). Then(can't imagine why)instead of suggesting that an amplifier with 1/4th the power rating would be sufficient, they suggest that another "headroom"(already accounted for by the 105dB or whatever max is to be used, of course)be added on.

In brief, you appear to be too concerned with the power question. Clean power is cheap and plentiful these days and both the principles of audio technology and personal experience indicate to me that typical receivers rated anywhere in the 100-150 watt area are ample for all safe sound levels with speakers such as Axioms(even that 5 watt tube amp which Alan derisively commented on might work with those Klipsch sensitivities).

Thanks! I wasn't really mentioning my sitation because I want any special recognition, I was just trying to express why the ultimate comparison is almost a year into the future. But thanks all the same!



My current receiver (and hopefully the new one I plan to get - Yamaha RX-V1900) has an audible speaker distance fine tune (maybe it's delay) Where it plays a short tick on both fronts. Sitting in the listening position, I can hear whether it's left or right of center. The setting is adjusted so that the tick sounds like it's coming from exactly inbetween the front speakers. I figure I will do this with both sets to help eliminate localizability (is that a word?) of which pair is playing.



Once I get home (in 5 months), and once I have get my treatments finished, I will do that test. I suspect it will be more than 3db per doubling, but less than 6db. Perhaps 4db? I know that even with just the front wall treated, there is definite absorption going on. The room is noticeably quieter. (less echoey)



What numbers did you come up with? Was this a treated room? If it was, I'd be very interested in the results.



I see, a fine print error.



Over on the Klipsch forum, somebody did relate an experience where he drove his RF-7s with a 50W amp, and it sounded better than with a different 200W amp. The context was that it was a very very nice 50W amp capable of meeting the RF-7s current requirements. Apparently there's a point in the impedance curve where the RF-7 drops down to somewhere between 2 and 3 ohms. It's somewhere around 180hz. So for them to sound nice you either use brute force with a 300W amp capable of delivering lots of amps in the first place, or you get a really really nice low power amp from a boutique store.

An update on the comparison, the Klipsch side is throwing yellow flags on the field. The Rf-7's tweeter and horn are larger than the RB81s (1.75" vs 1"), and as such, it is crossed over at a different frequency. Whereas the RB81 is crossed at 1400Hz, the RF-7 is crossed at 1200Hz. As one user put it, "it definitely improves the clarity and impact of the midrange/treble". Another user said that the RB81s may not give me an accurate representation of the RF-7s, and that the RB-75 (discontinued) would be a better match. The RB75 had the same size compression driver that the original RF-7 had, and was meant to provide RF-7 sound to those who didn't have RF-7 space. However, the tweeter was attenuated to keep it from stomping all over the RB75's single 8" driver (after all, the tweeter was designed to keep up with two 10" woofers)

I expressed to them that I will not be looking at low frequency extension, nor would I be SPL drag racing them, as towers are certainly capable of higher outputs. But I fear they may have a valid point in that the RB81s may not be a good representative for the RF-7s sound...

I say you skip all the deliberations, buy a honkin' big amp and the M80s and report back here after the setup has been hooked up and tested.

Carver amps are on e-bay often. I have 3.
TFM-45 375 Wats into 8 ohms
500 into 4 ohms
1000 bridged mono

These are smooth, silent amps.

http://www.carversound.com/carver-amplifiers/tfm-55/

Check this out.

wow .5% THD that isn't very good.

according to many different double blind tests that have been conducted through the years, people cannot differentiate between 0.5% THD and 0.00025% THD.
i can't give references, but i would not be surprised if some of those had been done by the NRC.

I forgot to say that THD figures are not very important by themselves nowadays.
Amplifier manufacturers choose a particular THD distortion number or level, and then read the power the amp puts out at that chosen distortion level.
this means that the THD figures are not a specification by themselves.

the very best amplifiers costing many thousands of $ will have distortion figures much higher than what appears in the specs when the amp is driven harder.

All I know is you can drive these amps to dim the lights in the house & they are on their own circut w/200amp service. The M 80s are crystal clear as are QS 8s. Song over, dead silence.
I really like em.

To add though, when I run my 27K generator, lights don't dim. Hmmmm