Axiom Home Page Forums General Discussion Advice from Axiom Owners Help! I think I need more power.

I’m pretty sure my poor Denon 2807 is falling short of the task of powering my speakers now that I’m out of the apartment and in a larger living room.

First some basic questions:

Is the information about listening levels and headroom for various type of music given on this site reasonably accurate:

How Much Amplifier Power Do I Need?

If given good info is this calculator realistic:

Amplifier Power Required

Until I completely set up the room I won’t know the exact speaker distances I’ll end up with but these numbers are most likely how far they will be from the primary listening position:

Mains/Center = 10 feet
Surround Sides = 6 feet
Surround Backs = 8 feet

The side and back surrounds may even end up farther if I ceiling/wall mount them instead of using the stands.

The loudest average SPL I typically use is 80dB.

I listen to everything except country and rap but I think the classical is probably the most demanding. Crown claims that classical music can have up to 25dB peaks so I used this number for the amplifier head room.

I ran the numbers assuming both worst case sensitivity 91dB and best case 95dB and came up with the following:

91dB
3 x M80s = 279w
2 x QS8 sides = 100w
2 x QS8 backs = 178w

95dB
3 x M80s = 111w
2 x QS8 sides = 40w
2 x QS8 backs = 71w

So even in the best case I think I’m going to need help powering the 3 M80s up front and will likely in the worst case or even somewhere in between need more power for the surround backs and possibly the sides.


A couple ideas I’m considering are getting the Outlaw 997 paired with the Axiom A1400-8 or a mid level Denon Receiver paired with the Emotiva XPA-3.

Any suggestions on other options to look at and the relative advantages/disadvantages of them are greatly appreciated.

More power?

Where is Tim Taylor when you need him...

Looks like he's going to play with some huge nuts.

Dean, as I've commented here before, the Crown discussion appears to somewhat nonsensically attempt to relate suggested amplifier capacity to the power handling ability of the speakers, e.g., 2 or 4 times might be suitable. This makes no sense because far less than the amount which the speakers can handle(which typically are in the hundreds of watts)might be actually used in typical home use(not the pro applications they emphasize).

The calculator there also doesn't seem to give realistic results. In Dr. Toole's book he cites studies indicating that in typical listening rooms the overall volume loss is about 3dB per doubling of distance. If we use a 91dB sensitivity number for the M80s, the loss at about 10' would be about 4dB, i.e., a level of about 87dB per watt. You want to use a 105dB peak, although I can assure you that few if any of even the most dynamic classical recordings have a dynamic peak 25dB above the average level. In a recent issue of my AES Journal, a group of CDs was analysed for dynamic range. The highest shown was about 18dB and what was rather amusing was a very uniformly loud rock item which had a dynamic range of essentially zero.

Be that as it may, using the 87dB per watt number at 10', 100 watts on a peak having a duration of likely much less than a tenth of a second would allow for playing the peak at about 107dB.

Thanks John. I figured there little calculator was a bit too easy.

I’ve read these articles by Alan.

Surround Sound A/V Receiver Buying Guide

Secrets of Amplifier and Speaker Power Requirements Revealed

In one article Alan suggests that the SPL weakens by 6dB for each doubling of the distance which would be a drop of about 9dB at 10 feet which assuming worse case 91dB - 9dB = 82db with 1 watt. So even assuming the higher weakening of the SPL with distance 100 watts should be able to deliver about 102dB which is still above the 18dB peaks you mentioned.

If 100 watts per channel is sufficient to get the SPL I’m looking for how do I go about finding something that can actually deliver 100 watts to all channels simultaneously.

My 2807 seemed capable of diving 2 x M80s and 2 x QS8s in my apartment w/no speaker more than 6 feet away at the 80dB average while still sounding good during peaks like the cannon balls crashing through the decks in “Master and Commander.” However, here in the house with more distance running 3 x M80s and 4 x QS8s it’s painful to listen at an 80dB average when the peaks hit.

Besides finding a review of an AVR that tests it with all channels driven is there any way to ferret out the true “all channels driven” power rating of and AVR?

Using Denon as an example the price goes up very quickly as the power rating goes up. Obviously I would prefer to not have to pay for power I’m not going to need but I also don’t what to buy something and be left wanting.

The other factor I was considering is paying to buy power over and over again. I’m not sure what the lifespan of an amp is, but might it not be less expensive in the long run to buy separate amp power that’s sufficient and then just upgrade preamp/processors as desired to keep up with the latest and greatest technology thus avoiding paying for the power section of the AVR with each upgrade?

Thanks for the feedback.
Dean

As long as he brings Heidi he’s welcome

A good amp, built with quality components should last a very long time. That's the direction I'm headed. My Pioneer receiver has 7 (8 including the sub) pre outs, so once I'm done upgrading my speakers I'll be looking for an amp or amps to take over the heavy lifting. Then I can move to a straight pre/pro and never look back.

Hi Dean,

The figures I mentioned in my article are the theoretical decreases in SPL with a doubling of distance, but since Floyd Toole was (is. .) my mentor, I'll certainly yield to his research and the figures quoted in his excellent book.

However, I'd point out that there is a lot of variation in personal preferences of playback levels. Even when I was on the NRC listening panel with Floyd Toole, my colleagues, including Floyd, listened louder than I did. I'd often sit farther back in the room to reduce the SPL at my seat. On average, I'd estimate they preferred playback levels at least 3 dB louder than what I was comfortable with.

In terms of my Axiom colleagues, I joke about some of the playback levels they like, which I find "deafening", at least 6 dB to 10 dB louder than my preferred settings (a 10-dB increase in loudness is subjectively termed "twice as loud"). And the playback levels they like are not uncommon--visitors to the listening room at the factory (of all ages) tend to use higher playback levels.

So factor in your own preferences, as it seems you have.

Regards,

Alan

Just remember that Crown sells amps. Of course they want you to believe you need more.

I suggest you try your current amp in the new place and see if you like it. If it under performs, then replace it.

BTW, IMO, you will have plenty of power (I just love TLA's ).

Isn't this where Wid chimes in about Rotel?

No, wait, this is where Randy talks about being so satisfied with Odyssey.

All threads lead to ecommerce.

How many threads must a man walk down.....

See, that's why being a troll is easier. Only one thread required!

Yeah, but that whole under-the-bridge thing never appealed to me.

Dean,

My speakers are about as far away from my seating area as your proposed room locations. When I was running the 3808 alone, and then later added the NHT (5X200) external amp, the differences were there, but not dramatic. I never bothered to set up the meter and see just how loud the room would get with the 3808, because it would play music much too loud for me to be in the room at max volume. I would have had to use double hearing protection, which would have made it impossible to detect clipping. So having said that, I have no idea what the max SPL level is before / after adding the amp. Where I did notice a difference (to the better) with the amp added, is scenes where there are large dynamic peaks. Master and Commander’s battle scenes are good examples to demonstrate this. No, this wasn’t a controlled double blind and sober test, just what my gut tells me. I’m pretty good about not getting swept away with the whirlwind of bullshit telling me how “things” can make my system sound better, for what it’s worth. Considering the 3808 has more power than your Denon, I think it’s safe to assume that you would in fact be able to detect an honest improvement if you add an amp or buy a more robust AVR.

Tom, your avatar has some competition.

Well, ya do get what ya pay for when it come to amps Tom. Rotel is among many brands that give a good bang for the buck, try one ya might just like what ya hear .

Oh, Rotel doesn't do ecommerce.

The calculators like that provided by crown are based on the physics of sound dispersion in free space from a point source. I expect that that would apply much more to the great outdoors where you don't have a lot of surfaces reflecting sound back at you.

Dean, when you used the Crown calculator did you remove 6db from your headroom to account for reflected sound in an enclosed space. Using the 95DB in room sensitivity of the M80 would be similar but only adjusting by 4 db. Either way, you will find that your power requirements drop a lot with this adjustment. 5-6db is what is suggested or implemented in calculators out there.

I suspect that in a small enclosed room, your gain could be a lot more, and in a very open large room smaller.

Have you considered a pro amp? They give the most bank for the buck on power.

From all the soundscape chart [thingies] I have seen, scenes like this pump out a lot of sound in the 40-200Hz range. I expect that the power demands would be quite high because this would drive the woofers in your mains quite hard, even with a crossover engaged.

I just wanted to point out that there's no real conflict between the 6dB loss per doubling of distance which Alan mentioned in his article and the 3dB loss per doubling which Dr. Toole describes(pp. 59-60). There's no question that a 6dB loss of sound intensity results when the distance is doubled with an omnidirectional sound source operating in an anechoic chamber or wide open area(e.g., top of the Axiom test tower)offering no sound reinforcement. This results because an omnidirectional source spreads out as a sphere, and the formula for the area of a sphere is 4pi x radius[squared], so when the radius of the sphere of sound is doubled, the surface area of the sphere is quadrupled since the doubled radius is squared. The intensity of the sound per unit of area is therefore only 1/4th what it was before the doubling of distance. Since 3dB gain is a doubling and 6dB is a quadrupling of sound intensity, conversely a 1/4th intensity represents a 6dB loss.

However, this number isn't applicable to home audio where the room boundaries add support to the sound and reduce the loss. This is the major reason why the Crown calculator doesn't give realistic results for home use, since its formula simply uses the 6dB per doubling figure. Only near the end in "other considerations" does it point out this key difference and suggest a 6dB adjustment(which would reduce the power number from the calculator to 1/4th of its previous value). Strangely, instead of suggesting that a much less powerful amplifier be bought, Crown suggests that the 6dB correction be applied to yet more headroom.

Dr. Toole, using previous research by Schulz, combined with his own work on the subject with speakers, finds that 3dB is the best number to use. Because of this research and earlier work I'd read about, I simply deduct 4dB from the 1 meter sensitivity number for a typical 9-10' listening distance and calculate the requirements at various dB levels from there, rather than using the Crown or other similar online calculators.

@ Chris - Thanks! I was pretty much set on just upgrading to a newer more powerful Denon but I started thinking it doesn’t make much sense to keep paying for a new power supply every time I feel the need to upgrade to some new feature in the processor.

@ Alan - Thanks for the clarification on the dB weakening with distance. Using either number puts me in the same general power range as my preferred average SPL of 80dB is well below the M80/QS8 91-95dB range.

@ michael - I was eyeing a 3808 for the move and am still considering one of the newer Denons near that range.

@ Fred - Yes I ran the number for both the 91dB and 95dB ratings coming up with a pretty wide range of power needed, however using the more realistic numbers supplied by John (-3dB/distance doubling and 18dB headroom) even the 91dB sensitivity leaves me needing at the most only 100-110 watts of power for the M80s and even less for the QS8s.

I would prefer to err on the side of a little more power than an insufficient amount and I wouldn’t mind the option of bumping up the stereo M80s higher when occasionally showing off or demoing the speakers.

What exactly is a “pro amp?” If that means going the separates route it’s looking more promising. Any suggestions on good pre/pro combinations?

An AVR is still a viable option I’m just not sure how to figure out if one will supply all the channels with the power they will need to reach the 80dB average with peaks of 18dB. Plus like I said above I’m not seeing the long term cost savings in replacing the power section every time I want to upgrade the processor side.

@ John - Thanks for the explanation. Either set of number seems to put me in the 100 to 110dB range for the max power I’ll need per channel. Is there any way to know from manufactures stated power ratings how much total power an AVR can deliver between all it’s channels or is an independent test needed?

Also, what are your thoughts on the long term economic advantage of using separates vs and AVR?

I see no economic advantage at all by going with separates over new AVRs. The problem is that they usually charge as much or more for the preamp-processor than they do for a receiver with similar features simply because separates are seen as higher-end. The main reasons I went with a pre-pro over a receiver is because the Integra DTC-9.8 seemed like the way to go at the specific time I was buying, since I don't remember any standout receivers that could decode the new sound formats. If the Denon 3808 had been out, I may have gone with that, but at least this way I got to have cool XLR connections. I have to say I like connections that click into place instead of connections that you slip (or force, red-faced) on.

There's a newer Integra out, but I haven't really read up on it. I'm still hoping the new Outlaw's Trinnov EQ is compelling enough to upgrade to. Other than that, I don't know what pre-pros are out there. I'm sure there are more options as you're willing to spend more thousands of dollars.

Dean, I'm not sure what "between all its channels" means. You don't add up the power each individual speaker uses to determine what the amplifier rating should be. For example, if five speakers were using 100 watts each(doesn't happen simultaneously in home use), a 100 watt, not 500 watt amplifier would be needed. The usual 2-channels driven at max for 5 continuous minutes rating, as required by the FTC regulations, is fine for real world application where all the channels aren't simultaneously driven at full power.

My general view is that unless more maximum power than the receivers with ratings in the 100-150 watt area can output is actually needed, the cost effective buy is the receiver. The economies of scale involved with receivers as compared with separate components practically amounts to paying the same or less than what a separate pre-pro with similar features(if available at all)would cost and getting the amplifier for free. If more maximum power was actually needed, a professional amplifier rated for at least 500 watts(less doesn't make that much difference)should be considered as a relatively inexpensive alternative.

@ Charles - I was considering the new Outlaw 997 which is another reason I was eyeing separates.

@ John - The example of the “Master and Commander” opening battle scene is about the best way I can describe what I mean when I say “all channels.” In my apartment when I set the volume so that the average SPL was about 80dB everything sounded very clear and precise albeit loud during the opening battle. Here in the house (larger room + 2 more QS8s) when I set the volume for and average of 80dB the opening battle is painful when explosions rock the ship, splinters fly and all the speakers seem to be pumping out lots of sound.

My assumption was that the 2807 had enough power to handle the 5.1 duties in the smaller room but is distorting/clipping with 7.1 here in the larger room. Is this a valid assumption or is there perhaps something else wrong with the 2807?

Assuming it is underpowered at “110 watts/channel” (Denons claim) how can I figure out how a “so many watts/channel” claim translates to being able to drive all 7 speakers in a demanding scene like the “Master and Commander‘s” opening battle.

Dean, I'm not familiar with Master and Commander(my music/movie ratio would be something like 99 to 1), so specifying that particular scene doesn't really clarify the problem for me. It's said that even seemingly very wild scenes very rarely have all the channels going near full-blast at the same time. Be that as it may, one of the receivers that actually does base its rating on an "all channels driven" measurement(e.g. HK, NAD)can be counted on to actually deliver the rated power to all seven channels simultaneously for at least five continuous minutes, because that's the test it had to pass to comply with the FTC regs.

Even some receivers that use the more typical 2-channels driven rating come rather close to that number even on an all channel basis when tested by labs such as Sound&Vision or Home Theater Magazine. Denon is one of those that usually does come close, so besides being able to count on the 110 watt rating being met, all channels might be something on the order of 90 watts.

Dean. A pro amp is what the musicians use. Crown is one example, Behringer another. The Behringer EP2500 puts out 800w/channel at a cost of around $350 new. Now, a lot of audio guys don't think the 2500 is clean enough for powering mains, but even if you go with more reputable pro amp suppliers at double the cost, it is still a lot cheaper than consumer grade separate amps.

There are some good discussions on avsforum about pro amps. The biggest downside is that some of these amps can have noisy fans cooling them that need to be moded for home use.

John. Thanks for the additional info on Toole. I've wondered if anyone did any measurements to verify how sound falls off in an enclosed space.

@ John - Thanks for the explanation and examples of manufactures. Just to be sure I’m understanding…something like the Denon 3310 rated at 120 watts/channel x 7 should be able to drive my 7 speakers to the parameters already discussed without distorting in even very demanding scenes?

@ Fred - Thanks for the advice. I’ll check out AVS hopefully those sub-forums aren’t as bad as the speakers ones. Noise should not be an issue as all my equipment is located in the office adjacent to my living room behind a set of French doors. I use to always be able to hear my computers and especially the Xbox running. Now nothing but silence from my equipment and its on an open rack so getting to anything is a breeze.

@ anyone - is there any disadvantage to having a long wire run from a pre-processor/receiver analogue outs to the amp. Reason I’m asking is that if I did get something like the Emotiva XPA-3 to power the M80s I could place it behind the screen which would also put it on a separate circuit from all the rest of the equipment in the office.

Part of the reason I ask is because sometimes on my weekdays off I can hear very faint music coming from my center M22 speaker when my system is on and nothing is playing. So I wasn’t sure what was causing it to pick up a stray signal or were it’s coming from . It’s inaudible when anything is playing so I haven’t tried to figure out why it’s happening or why only that speaker (only thing different about it is that it’s hooked up via a switch with the M80 center).

Not necessarily, Dean. Keep in mind that when a receiver spec says something like 7x120 watts, that doesn't mean that the rating was with all seven simultaneously driven at full power. If language such as "all channels driven" isn't used, it's to be understood that the rating was with two channels driven. But as I said above, Denon and some others have tested out with all channels fairly close to the two channel rating. Again, my view is that all channels simultaneously at full power rarely happens outside test labs, but someone with a different view should consider buying a receiver rated with all channels driven or should buy only units that have published lab tests showing high all channel numbers. For example, a very inexpensive receiver that I've owned for some time was rated at 75 watts with two channels driven, but tested well above that number and at 71 watts even with all seven channels driven. Plenty of power with even my most dynamic classical recordings.

The pre-outs are pretty low level which means strong outside interference will have more of an effect on them, than say the speaker level lines. Good quality, shielded coax will help a lot. Shielded XLR will help even more (provided the preamp and amp both have XLR jacks).


Sounds like an AM radio station is being rectified in some piece of gear. Get an AM radio and scan the dial to see if you can find the same music playing there. Not that it will help anything, just confirm the theory. Could be the switch, or even the power cord of the receiver--don't know why it would be only one channel, but stranger things have happened.

Dean, is the music you're hearing coming from the tuner?

Keep in mind that if you plug your external amp into an outlet on a different circuit, you might end up with some ground loop hum.

I used to hear 'ghost' radio stations all the time from my computer speakers when the computer was turned off. A bit freaky the first time you hear fuzzy voices and look at the power bar showing that everything is turned off.

That’s where balanced connections come into play. They are not needed if the amp will be within a few feet of the processor, but are needed if your runs are farly long. One aspect of going with separates over an AVR, or, use an AVR as a pre / pro, is it gives you a little more freedom to choose your processor without having to worry about the amplifier section. The last two to three years has been ridden with numerous technological advances in the HT world. About every six months we get to read about the “newest” change. If you go the separate route, you can stay on top of the changes by buying mid level AVR’s instead of the higher end units, which usually come with the larger amp sections. (IE: Denon 3808 verses 5308)

One other thing you may want to consider is to pick up a two channel amp and let the AVR drive the remaining speakers. You should also keep in mind that DD and DTS have new channels to consider when you are looking at buying a different audio processor. (height / presence / width channels). As soon as the Denon 4810 is released, I’ll be moving to that unit.

Nah, Adrian. With all due respect to Mike, the absence of head on the beer in the picture proves that it is not a Proper Pint.

oh, and, obontopic: Amps are cool.

Nah, it's a perfect Black and Tan. Notice the background too. Corks in a big martini glass......

@ Chris - Thanks! I suspected there might be more potential interference
problems using long runs from the pre-outs.

@ Mark, Chris & Murph - It's definitely music coming from the center M22 but it's
very faint. I'm off this Friday so I'll see if it happens again and try to
find the source.

The first time I heard it I thought it was coming from outside but when I
walked to the various windows it got softer. I finally figured out it was
the center speaker. I didn't give it much more thought since it was
inaudible with anything playing. However, it may become a factor if I run
long wires from the pre-outs.

@ Michael - If I do buy a separate amp for the front speakers it will likely
be something like the XPA-3 so it can power all 3 M80s. That's why I'm so
interested in how it works out for your M80s. Though it's looking like I
won't be needing anywhere near that much power so now I'm looking at what
other amp specs and design factors might play a more important role in my
situation. I'm sure I will have more questions about that.

Any word if Axiom will carry the Sherwood R-972?

Sherwood R-972

I believe I remember Alan saying something along the lines of they are awaiting its arrival.

In the "Official" thread on AVS, people have mentioned they're waiting for Axiom to start selling them as an indicator that the receiver is available to the public.

Cool! I guess I’m hanging out at the right place then.

Club - which Pioneer receiver. I just got the SC-07 and am trying to figure out how well it will do with the 80s - alternatively I will just stick to the 60s

Thanks!

So after all that help over there you come here and hijack my thread?

Just kidding. Welcome to the forum Mike.

I have last year's VSX-1018AH-K (which I still prefer to this year's model). I don't have M80s yet, but that's what I plan on buying. I don't have any fears about this receiver having trouble with them at least at reasonable listening levels. Considering that yours is several models above mine I don't think it'll have any problem at all with the M80s.

LOL - was thinking it was the same Grunt

not hijacking the thread - directly related go power and the Axiom speakers

Chris - thanks for the quick response. Guess I am not the only one online browsing AV stuff late at night. Bet I am the only one drinking an Alaskan IPA though

I think I should be fine with the 80s just know Grunt will give me hell for not matching up the center!!!

On a serious note though the fact that Axiom does free shipping to AK makes me want to support them (OK done hijacking the thread now)

Thanks!

No worries mate! Thread hijacking it a way of life here. I think it has something to do with how twisted we are.



BTW we do have a thread for that.

beer thread

Notice how originally it was named too.

I like hoppy beer so how is the Alaska IPA?

All this talk of beer makes me think I should have my last Bridge Port IPA and watch the “Beer Bad” episode of “Buffy.”

Damm! Now I’m hijacking my own thread.

I'd probably be kicked off this forum if I let it slip that I don't drink beer.

I will go to any length to match the center.

http://www.axiomaudio.com/boards/ubbthreads.php?ubb=showflat&Number=219121&#Post219121

Tea totaler, or just don’t like the hoppy stuff?

First time I drank beer it was just some pissy U.S. macro-brew but I still remember thinking who can drink the bitter nasty stuff. Now I like extreeeeeeemnly hoppy (bitterness, flavor and aroma) beers. Guess it was an acquired taste.

They'd have to kick me out, too. Wait, I'd better not give them more reason.

Totally about tea here. No drink, no smoke, no drugs, no gambling.

Home entertainment is my addiction.

I've mentioned before that my Denon AVR-3300 is rated at 110x5 (I think?) but actually starts to clip the signal at 84 watts, according to HT Mag. On the other hand, my QSC pro amp has not clipped yet (accoridng to lights!) and can easily triple the power output.

As for pro amps, I will warn that many lack RCA inputs, so you need XLR converters if you don't have a separate pre-amp. Not a big deal in theory, but my first proamp (Crown) made noise when using the RCA to XLR convertors. Just a word of caution. Also, be careful of the noise specs on the pro amps. The Crown I had had a S/N of something like 91 or something like that, and I could hear hiss in background. My QSC is around 100 and I don't notice a hint of noise even in dead quiet passages. For a reference point, QSC's THX amps are around >105 I think.

That’s the big problem I’m trying to figure out is outside of a reviewers measurements how to determine what the real power going to all the channels is. My Denon 2807 is rated at 110x7 and I can play 2ch music up to 105dB without a problem, however in a demanding multi channel scene it starts clipping/distorting way below that.

So I need to know for sure how much say a 120 watt Denon can really deliver to 7 or 4 channels. 7 if I used it stand alone, and 4 if I used it for the just surrounds/backs. Above 120 watts the price really starts going up fast.

OTOH if I do end up getting the Outlaw 997 then I’m going to need amplification for all 7 channels.



Good to know. I’ve checked out the Behringer A500 mentioned by fred and it looks promising. But now I need to start figuring out what other specs. in an amp are important. For instance what are good numbers for S/N ratio, crosstalk, frequency response, THD+N and anything else I‘m leaving out. Also in which direction are those numbers better and worse. I’m assuming smaller is better for the ones I mentioned. Plus, is there a sort of cut of were a better or worse number isn’t really noticeable. And how does the amp design A/B etc… effect it’s performance in various roles. I guess what I’m saying is I really need a good primer on amps but have yet to find one.

Basically I don’t want to pay for a bunch of power I don’t need while ignoring other factors that may be more important to me in the amps performance.

Thanks for bearing with me on this guys, I’m usually not this dense.

I would look at the numbers on quality amps - Lexicon, Krell, Bryston, etc., and try to get as close to those as you can. For S/N, you want the number higher, for distortion numbers, you want them lower. On pro amps, they worry more about 2 ohm suitability, bridging, crossovers, and power than the audiophile sector. But you can find all the information need to make a good decision. The QSC website has some good information on amp design and power, and their forum is run by real techs - just don't expect a HT tech.

Lavender screen of death!

Ok, more like lavender screen of not to healthy. Looks like my Denon is having more issues so it’s a good thing I’m looking to upgrade. Seems to be an HDMI handshake issue that was never there before. Turn everything on and the screen is all lavender with any HDMI output from the receiver to the TV. VGA from the PCs works fine and HDMI direct from the OPPO works fine. It’s happened a couple time in the last weeks but this time turning it off and back on wasn't helping. Changing between inputs on the TV finally got them talking again.

I’d like to see the Sherwood R-972 and the Outlaw 997 out soon so I could read some reviews.

Likely still looking for more power.

I think Charles has or had an Integra receiver so I’m wondering if anyone is using one with there Axioms. A local installer I’m talking with can get me a very nice deal (authorized dealer) on and Integra DTR-8.9. Main reason I’m upgrading is the new audio formats not the power but I didn’t see the point in starting another thread.

The DTR-8.9 should have all the power I need (unless I get upgradeitis). I specifically don’t want Dolby PLIIz. I already think PLIIx is a waste and don’t want to be spending time tinkering with PLIIz since I if I have it I know I will.

I’ve given up on the Sherwood Newcastle and the Outlaw. Maybe next upgrade Trinnov will be in the picture but I can’t see getting either of those with all the problems they’ve had and still seem to be having.

So any thoughts on the Integra 8.9 for running M80s?

It looks to me like it will work fine. I don't have a local dealer, or I would have had the firmware updated on my processor. I probably won't get around to sending it in until I'm giving it to my dad (after my next upgrade). That's the major inconvenience. It would be nice if the updates could be done via USB and without any hoopla. However, since you have a local dealer and can get a good deal, I guess it just comes down to how good of a deal you're getting. Hopefully someone will have experience with that specific model.

Dean, the 8.9 should be excellent for you if those are the features that you're looking for. Depending on how "nice" the deal is though, consider that the nearly identical Onkyo 876 can be had for around $900 a factory refurb.

It was one of their show room demos which they are clearing out both for the new models and a redesign of their showroom. The deal is $1,200 sold as new with full warranty. If it requires warranty work they will pick it up and handle it while loaning me a receiver until it gets back. They will also calibrate my picture.

I will look into the Onkyo but I’m a little leery of getting another factory referb like my current Denon since it only came with a 90 day warranty, not that it hasn’t worked fine (except perhaps for Audyssey).

Thanks,
Dean

If I may add to some of the questions that Dean mentioned re. Pro Amps specs. What is considered to be a desirable slew rate vs a poor one, is a lower/higher number better/worse?

I've been checking out a number of Pro Amps and I'm starting to believe that many of them are coming out of a single(huge) factory in China as they are virtually the same except for the face plates, including some of the "expensive" ones.

If you look at some of the amp porn over on avs you will see the internals are different. It is quite clear that a number of the newer amps are clones of designs from more established companies like Crest or QSC.

The EP series is a clone of Some QSC amp. The Marathon 5050 looks identical in layout to one of the Crest Amps.

I read on one of the forums(AVS?) that only the digital amps by QSC are still made in the US, the rest are made offshore. I'm quite sure that many amp companies are subbing their work to a common denominator offshore and perhaps they have to make a few minor internal changes to skirt whatever laws apply. It was actually stated on some forums that Behringer, Tapco and QSC(GX series?) were made in the same plant, right next to each other. I've also run across a number of other amps with "unknown names" that look and spec so similar to these that it makes you wonder(sometimes they hardly give you any specs at all, LOL). I guess it doesn't really matter where they're made as long as the company(Behr, Mackie, QSC ect) stands behind them.

I pretty much agree. What I did gather from all the amp pictures over on avs is that they are not all designed the same, even if there are clones of some designs.

Dean, I tend to share the view that factory refurbs are more reliable and have lower return rates than brand-new units, although I haven't seen any statistical study on the point. My personal experience with them has been excellent.

The best buy on the 876 at this time appears to be $860 with free shipping from Accessories4less .

Adrian, slew rate is one of the specs(damping factor is another)that the audio consumer doesn't have to worry about comparing between units he's considering for purchase. The reason is that the frequency response of the unit serves as a proxy for necessary slew rate. In order to reproduce 20KHz with a flat response and with low distortion an amplifier has to be able to respond to a signal moving 20,000 times a second quickly. The formula for calculating this at a certain power level is (6.28 x frequency x peak voltage)/1,000,000. For example, for 100 watts into 8ohms a peak voltage of about 40v is required, and the formula becomes (6.28 x 20,000 x 40)/1,000,000= 5.02 volts per microsecond. So, as long as the amplifier can change("slew")at a rate of 5.02 volts per microsecond, the 20KHz signal can be reproduced accurately at 100 watts. Typically, an octave higher response, i.e., 40KHz, is designed, which requires twice the slew rate, 10V/microsec. Since lab tests routinely show flat low distortion response to beyond 20KHz in even modest cost units, this establishes that the slew rate is adequate and not a matter of concern.

Of course, sometimes manufacturer hype(or naive audiophile belief)promotes much higher slew rates than required, with at least an implication that this would somehow make the sound "quicker". This is pure nonsense, and if a frequency was reproduced quicker than the Hz number, the correct term would be distortion. So, any number in the low double digits is fine for typical power levels, and specs showing rates of 50 or more which appear for some units aren't of real significance.

Thanks for the link John. Nice that they have a 1 year warranty.

The 6.28 is 2 Pi, which is the formula to calculate the slew rate of a sine wave. Other functions have higher slopes, and would require a higher slew rate.

I have a QSC GX-5. The inside is a very clean layout, but nothing about it implies made in a German lab or Swiss watch factory. I don't care if it is made in China if held to QSC's tolerances. I'd love a built in the US option, but I'm too cheap for that right now.

As to the competitors you mention, they may well be made in the same line with the same components - I have no idea. But when shopping I found the specs varied a decent amount - power, S/N, THD, etc. I tried a Peavy and it was too noise at idle for me. And the GX is a class-H layout, I did not remember those others using the H layout.

I am a big fan of the H topography as it keeps the heat to an absolute minimum except for high volume use when it switches to the high-current rail.

And note that the QSc GXs have RCA inputs so you don't have to work around the XLR inputs on most pro gear.

That does sound appealing, Charles.

Oh yes, I also forgot, under $400 for endless power. Took the fan out and toned down the laser bright power light and she was good to go. Nice thing about a $400 amp - not afraid to open it up and pull out the noisy fan.

I would never do that to a Krell or Bryston.

$400 is still a little steep for me to muck about on the insides, but I'm cheap.

I hear you - my AVR and speakers are 10 yrs old so I don't like to trash stuff. But when I bought it I knew of the fan noise issue so I went into the purchase knowing a repair might be needed if I mucked up something. It was super easy, just like the inside of a computer, unplug the fan and pull it off the plastic clips. No hassle.

There are a number of forums on the web regarding swapping out "noisy fans" on pro amps for home use. Charles, how much heat does your amp put out without the fans if you push it? The noisy fan(s) are one of the concerns I have if I were to get a pro amp. You use an external fan just in case don't you? I think I saw one of your posts where you had a fan off to the side of your amp.

When you get a chance, have a look at some of the EPX amps from Behringer and the Tapco(Mackie) J2500...these are also class "H" amps, and see how they compare to the GX-5. Also compare the Behr'er EP and Tapco J1400 to the GX-3....some of the similarities are uncanny. Whether this is a case of copying, subbing to the same production company or if all these amp builders basically ended up with the same design conclusions, I don't know. Maybe one of the tech guys here can enlighten us/me a little.

On the low current rail it stays cold - really, feels less than room temp, but just because it is metal. Comports with the low wattage needed for normal sound principle. When the high rail kicks int, you can cook on it without a fan. The external fan is nice b/c you can easily unplug it if don't want to run it hard, and when running hard, you can't hear the external fans anyway.

You cold replace the internal fan without much work at all. but the cause of the noise is the cheap mounting system, not so much the fan, and I did not want to mess around with better options to mount the fan.

I'll try to look at those other amps. I should have taken a pic with the amp opened up.

Charles, here is some pictures of the internals of these amps I mentioned. Scroll down to see the pics.

Well, they're not quite identical. Similar designs, certainly, but hardly identical.

That was not a pic of the GX, not from what i recall anyway. I agree they look similar in layout, but you can see they are built to different specs. Look at the caps, they are different sizes in each.

Zimm - do the amps you are using have current sensing so that they turn themselves on when they get a signal, or do you have to find some other way to sync the 'on/off' to when your AVR turns on and off? (or are they really easy and have a remote control that turns them on/off)

Thanks,

Jason

I forgot that pain in rear part, you must flip the switch. If you get a IR controlled outlet it would work, but it is easy for me to turn it on/off since it is in the open. But yes, that is another issue you have to deal with. Bit of a pain, but livable.

Do your receiver and amp have triggers you could use?

There are a couple of other similar amps besides those ones(EAW CAZ800/1400/2500). I guess the point I'm trying to get at, is that like many other branded products, some of these amps(despite some spec diff's) are likely being subbed out to the same manufacturer offshore.

From what Zimm wrote back, the amp does not. And in my case, neither does my receiver. (Denon 3808)

It has an outlet on it, but not one into which you'd want to plug a 4 million watt amp like Zimm is using.

You'd also have to watch those remote controlled outlets. Many of them are not rated for the kind of current an amp would pull.

Yep, I thought about plugging it into my Denon, but that seemed rather...well lazy. Risking some electrical issue so I wouuld not have to flip a switch once at the start of the session and once at the end seeme just too much. Now, if it was stored in a closet or something, I would likely find some work around.

No, no triggers. Again, this is a $400 amp. All the money is in the power supply, no frills. If you step up to the higher models from QSC you get all those fun toys - but the THX certified cinema line adopts the pricing of your regular Krells and Brystons.

No thanks.

There is a device that can plug into the back of your receiver and it would trigger your amp, It comes with different ends for different types of trigger inputs. I bought one a Best Buy a while back. I beleive they are called power converters. If you do buy one make sure it has the right connector for your particular trigger.

Does it also have the trigger...cause...again...I don't have trigger inputs on my cheap amp. You can rub it in another way if you like, but the fact remains it aint got no friggin trigger.

Perhaps I could plug the wire into...no, wait...no trigger!