nicholtl Posted May 21, 2005 Share Posted May 21, 2005 ---------------- On 5/21/2005 10:06:50 AM JewishAMerPrince wrote: First 70wpc then to 125wpc then to 200 wpc (all Rotel). Each time I upgraded the sound from the 7s got less compressed at high spl. Everything just became "more" effortless. ---------------- Absolutely. Such was the case when I moved from a 7x100 watt receiver to 250wpc amp separates. Quote Link to comment Share on other sites More sharing options...
mdrums Posted May 21, 2005 Share Posted May 21, 2005 Here the deal: I went from a mid line Yamaha Receiver to a Pioneer top of the line Elite Receiver and noticed a sound differance for the better. I then went from the Pioneer Elite Receiver to a seperate MacIntosh pre-pro and MacIntosh amps and notice a huge differance...basically same amount of power but better sound. My friend went from a Yamaha receiver to a Parasound amp and noticed a differance for the better. Again about the same amount of power too. What we both noticed is the RF7's are very smooth and clear and detailed with the better amps (i.e. MacIntosh and Parasound Halo) Quote Link to comment Share on other sites More sharing options...
Spkrdctr Posted May 21, 2005 Share Posted May 21, 2005 ---------------- On 5/20/2005 3:26:12 AM DrWho wrote: ---------------- On 5/19/2005 1:02:03 PM Kriton wrote: If amperage is what is important, than why do we even talk watts? Would a Sunfire 400~7 be necessarily better than a 200~5 (apart from the obvious more channels, which I wouldn't use anyways) and does this amp have the amps necessary to put out for the RF's, Please clear this up! K ---------------- Proper headroom is having the ability to play at least 10dB louder than the normal listening volume. So let's say you normally listen at 90dB (which is just starting to sound loud), then you will want an amp capable of driving your RF-7's to 100dB, At 1 watt, your RF-7's are already putting out 102dB! For every 3dB, double the amplifier power (so 105dB = 2 watts, 108dB = 4 watts We talk watts because that is what is important. Using the above example of VERY loud listening, (108db at 4 watts) you are using almost no current at all! You are talking a minimal four watts. Even the run of the mill Pioneer reciever can easily supply all the current needed at 4 watts. The differnt sound of different recievers/amps can make a huge difference at times. But, the power is not even a factor at 4 watts, except of course your common amp/reciever does have a lot of headroom, causing the Klipsch speaker line to sound so much better than other speakers because you will most likely not drive them into clipping, except for demonstration purposes. Remember, high current is not usually the reason for improved sound with Klipsch speakers at any normal listening level, of say less than 105db (which is loud!) The RF-7 at 102db is using a whopping 1 watt!!! Any way you figure it, you can't stress a cheap reciever with 1 watt. I try not to delve into this too much as I don't want to be a killjoy. But 1 watt is 1 watt.....very tiny! Quote Link to comment Share on other sites More sharing options...
Spkrdctr Posted May 21, 2005 Share Posted May 21, 2005 ---------------- On 5/20/2005 3:26:12 AM DrWho wrote: ---------------- K ---------------- Proper headroom is having the ability to play at least 10dB louder than the normal listening volume. So let's say you normally listen at 90dB (which is just starting to sound loud), then you will want an amp capable of driving your RF-7's to 100dB, heck 20dB of headroom would mean needing to "only" reach 110dB. At 1 watt, your RF-7's are already putting out 102dB! For every 3dB, double the amplifier power (so 105dB = 2 watts, 108dB = 4 watts....120dB = 64 watts which is the "threshold of hearing"). An amp capable of running a clean 50 watts will be more than enough to power your RF-7's. ---------------- Dr. Who, the above is very well written. You beat me to it! Oh well.... I had to work... Quote Link to comment Share on other sites More sharing options...
Kriton Posted May 21, 2005 Share Posted May 21, 2005 Awesome! Thank you, clear as mud ... So can any body answer or remember my original question(s)? If one watt is one watt and it is very tiny, and therefore any receiver/amp can out out one watt and current doesn't matter, then why do we bother with any different amps/receivers/etc? My puny receiver is certainly capable of one watt and no current, so why should I bother looking for an amo at all, what difference does it really make, using your example? Back to the original question, is there any difference between a 200 watt amp or 400 watt amo in teh same amp line (like a Sunfire)? I use this example because it is my understanding that these are high current amps? Please get me back to the original question...please give me some examples...why is a yamaha not as good as a B&K not as good as a Krell? By your analysis, they are all 99% hype and 1% science? Thanks! Not trying to be smart ***, just never seem to get an asnwer to my original questions sometimes... Thank you! K Quote Link to comment Share on other sites More sharing options...
MrMcGoo Posted May 22, 2005 Share Posted May 22, 2005 Kriton, We bother with better amps because many amps cannot produce the current needed when the impedance falls below 4 ohms. Impedance varies with frequency. When impedance falls from 8 ohms to 4 ohms, current demand doubles. When it goes from 4 ohms to 2 ohms current demand doubles again. Receivers cannot produce the needed current when the impedance dips. When the current cannot be produced, voltage drops and frequency response suffers. Receivers usually use one pair of MOS-FET output devices per channel. The B&K Reference amps use 5 pairs, which do not limit current output and opearte within their linear range. A bigger power supply allows better current output. The B&K amps weigh 75 pounds. A typical Japanese receiver weighs 45 pounds or less which tells you it has a smaller power aupply. Japanese receivers do not drive 4 ohm loads. Receivers are usually over rated bt their amnufacturers. A 100 watt receiver may actually produce 35 watt per channel with all channels driven. A separate amp will produce rated power with all channels driven. Bill Quote Link to comment Share on other sites More sharing options...
Lurch Posted May 22, 2005 Share Posted May 22, 2005 What we are talking about is the power supply. You'll notice that receivers generally aren't rated to double their power as the impedance halves. This is because their power supply is "current limited". A "perfect" current source will double its power output as the load drops from 8 to 4 ohms (for example). There is no way a receiver can do this and this is why they are almost never rated into 4 ohms. They generally have a puny 10-30,000 uf of capacitance for 7 channels, while a 2-channel amp can have upwards of 100,000 uf. So, as the impedance drops, the amp has to produce more current to generate the same voltage across the speaker. For example, if we have an 8-ohm resistive (ie - no variance in impedance across all frequencies) and it takes 1 amp of current to produce a given voltage, then you will need 2 amps of current to produce the same voltage across a 4 ohm resistive speaker. So, your RF-7s would want more than 2.5A of current at certain frequencies to maintain the desired frequency response. "Well," you begin,"why can't my receiver put out 15 amps? It's plugged into a wall socket that has a 15A breaker down in the basement?" Every amplifier converts AC to DC and then stores DC in its power supply to deal with the demands. This is how the size of your power supply determines how much current your amp can safely deliver. Your receiver just can't produce enough current to keep up with the demand and you end up with a ragged frequency response. Why? Because the amp can't produce enough current. To see a big power supply in action, turn off a good power amp while the music is still playing. You will hear the music for several more seconds as the amp slowly drains its huge power supply. Jeff Quote Link to comment Share on other sites More sharing options...
MrMcGoo Posted May 22, 2005 Share Posted May 22, 2005 One fianl point needs to be made about home theater amps. If you listen at a quater of a watt, you will need 250 watts when a 30 decibel transient comes along. A quarter of a watt may be about 75 decibels at the listening position. THX speifications allow for 105 db peaks in movies which would give a 30 db transient. A 30 db transient requires 1000 times increase in amp output. Bill Quote Link to comment Share on other sites More sharing options...
Lurch Posted May 22, 2005 Share Posted May 22, 2005 And, a super-duper power supply doesn't guarantee great sound. One of the forum members bought an Adcom GFA-5800 to run his KLF-30s, because he thought it would improve the bass. It did, but he wasn't as happy with sound compared to his old Luxman integrated amp. Look for an amp that sound great and all of the current and wattage issues are going to be secondary. I'd bet this would be a great match for a pair of RF-7s: http://cls.audiogon.com/cgi-bin/cls.pl?ampstran&1121653909 Quote Link to comment Share on other sites More sharing options...
Kriton Posted May 22, 2005 Share Posted May 22, 2005 Amazing! I have learned more in the last 10 minutes reading your posts in reply to my frustration that I have in the last month lurking around and reading this board, thankyou! However, this raises new questions...I understand the need for current when the impedance drops, and I have read that the RF-7 impedance can drop precipitously below 8 ohms...under what circumstances exacly would it do this? Why would Klipsch make a speaker that has a devilish drop, knowing that these things will sound their best being played on ordinary (big box) equipment (which I am assuming that you are saying my puny amp can't muster that surrent at low impedances, therefore bad sound as the ohms dip, and I also make the assumptiont that the majority of the folks pushing these things have crappy receivers playing them)?? Do the heritage speakers have this drop in impedance too? (I have a trusty and recently rebuilt pair of Cornwall II's in different listening room with, yes, a crappy receiver for them as well (only listen in two channel there however), get the reason why I want to upgrade ALL round?) You also mention a ragged frequency response, what exactly, does that sound like? I can go to a high end audio store all day long, and no body be able to show me, by example, a "ragged frequency response" - Do you have any specific movie or music examples, when I make a side by side comparison, I could hear the response on a big box receiver or a quality theatre or two channel amp, all other things considered equal? What happens, say when one of these sound transients comes along and the receiver can't meet the current requirements? Does the moment pass silently by, does the receiver belch it out as noise, does the receiver clip, what?? I am really more interested in the silence AFTER the transient, in other words, will I be able to hear quieter passages more clearly with a separate amp, or will I have to keep turning up the damn volume, or more specifically changing the balance of the speaker volumes depending on the movie? Will the receiver just clip and die ( I can dream can't I, make the wife more amenable to the upgrade!) Next question, I have seen amps that are heavier than hell, but does that necessarily mean high current/wattage or quality? Is the Sunfire series just smoke and mirrors, as the CG 400~7 weighs only some 40 pounds? I have seen some great reviews about warmth and the "down tracking" power supply, is this just hocus-pocus, and would I be better served getting a real behemoth amp that runs hot and is a hulking steaming pile of power (oooh, that was almost poetic, I like the visual, cut to a picture of the Levinson monoblock towers for sale on 'gon, I bet I could cook an egg on those things when they are rocking). I am getting closer to enlightenment boys, now just bring me home. Thank you for your responses, truly...I greatly appreciate you sharing your learning... K Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted May 22, 2005 Share Posted May 22, 2005 'Proper headroom is having the ability to play at least 10dB louder than the normal listening volume. So let's say you normally listen at 90dB (which is just starting to sound loud), then you will want an amp capable of driving your RF-7's to 100dB, heck 20dB of headroom would mean needing to "only" reach 110dB. At 1 watt, your RF-7's are already putting out 102dB! For every 3dB, double the amplifier power (so 105dB = 2 watts, 108dB = 4 watts....120dB = 64 watts which is the "threshold of hearing"). An amp capable of running a clean 50 watts will be more than enough to power your RF-7's.' I just wanted to commend DrWho on his very thoughful, yet simple explanation. Them classes are paying off, aren't they College Boy! Michael Quote Link to comment Share on other sites More sharing options...
Spkrdctr Posted May 22, 2005 Share Posted May 22, 2005 I have to work today. I will post tomorrow a lengthy explanation/answer to your questions. Your eyes will be opened, you will never fear an amp again! Oh, before I go, no the Sunfire is the real deal it IS NOT smoke and mirrors. They will kickass. More to post tomorrow...... I hate it when work interferes with my personal life! Quote Link to comment Share on other sites More sharing options...
MrMcGoo Posted May 22, 2005 Share Posted May 22, 2005 Kriton, The Sunfire amps are VERY good. However, Bob Carver has a tendency to overstate their performance in terms of total watts produced with all channels driven. My surrounds seem to have come alive on a Sunfire 400x5. When frequency response suffers due to lack a of current, bass becomes boomy. In worst cases, a receiver will go into protection mode and shut down. You hear more of what is on a DVD with a good amp. As far as Klipsch is concered, most receivers will do an ok job with RF-7s. A 60 watt tube amp with 4 ohm taps will do a great job. However, best sound quality requires separate amps of high quality, just like other speaker. Bill Quote Link to comment Share on other sites More sharing options...
Lurch Posted May 22, 2005 Share Posted May 22, 2005 Kriton, The impedance curve of a speaker is a constant thing. So, when we say that the RF-7s drop to 2.8 ohms, the amp has to deal with that all of the time. It is essentially a combination of the load the amp sees because of the crossover and the drivers. The RF-7s have 2 bass drivers operating together which causes the bass to be rather hard to drive. If you have an "8 ohm" driver and you put two of them together to operate over the same frequencies, you will have a "4 ohm" load on your amp. Whenever I have listened to RF-7s in a store, they are invariably hooked up to some receiver. As a result, I've never heard them sound that great. When I compare them to other speakers, they might do well in certain areas, but they end up sounding colored (ie - not as clear, muffled, strained, etc). Dynamics should be a strength, but when I've listened, they end up sounding bland and uninvolving. What I was hearing was the equipment upstream of the speakers. On the other issue of power supply, there are a FEW exceptions to the heft rule. The Sunfires employ an unusual solution to this problem and get around the problem of needing a massive power supply. Although they will drive the RF-7s with ease, you may still not like the way it sounds. Everyone has different listening preferences or everyone would just buy the Sunfire and be done with it. Let me tell you about another danger you are facing: constant upgrades. Once you start listening more critically and to better, more revealing equipment, you will find more and more reasons to buy new amps, speakers, etc. I started out in high school with an Onkyo receiver and Genesis Physics bookshelf speakers. Since then (19 years), I have owned the following stereo speakers: Boston Acoustics 100s Altec Lansing 301s Vandersteen 1Bs Dahlquist DQ-12s Vandersteen 3s Klipsch Heresy IIs Klipsch Forte Is Infinity IL-40s Infinity Kappa 600s I have owned the folowing preamps: NAD 1700 Forte 40 McCormack TLC-1 Sonic Frontiers SFL-1 Signature AES (Cary) AE-3 Signature Chinese-made preamp similar to AE-3 HK Citation I HK Citation IV HK Citation 21 Dynaco PAS-3 Outlaw 950 I have owned the following amps: NAD 2400 (then 2 in mono) Forte 6 Mark Levinson 23 Quicksilver 8417s HK Citation II HK Citation 22 Dynaco ST-70 Heathkit WM-4s Anthem MCA-5 McIntosh MC250 (x2) B&K Reference 4430 You get the picture???? I haven't included CD/DVD players, turntables, tubes, power conditioners, interconnects, speaker cables, etc, etc, etc. Also, think about how many different items I've demo'd!!!! You are on the right track here though. Find out what you really need, talk to folks who have been through the same kind of decisions, try to get the piece of equipment into your home for an extended listen and don't convince yourself that something that bothers you about the piece doesn't. If you don't like something about it, don't keep it. Trust me; in the end you won't anyway! You will have to be very disciplined to avoid going thru equipment like yours truly. Make sure you maintain your perspective on this hobby. Jeff Quote Link to comment Share on other sites More sharing options...
DrWho Posted May 22, 2005 Share Posted May 22, 2005 ---------------- On 5/22/2005 11:03:46 AM Kriton wrote: However, this raises new questions...I understand the need for current when the impedance drops, and I have read that the RF-7 impedance can drop precipitously below 8 ohms...under what circumstances exacly would it do this? Why would Klipsch make a speaker that has a devilish drop, knowing that these things will sound their best being played on ordinary (big box) equipment (which I am assuming that you are saying my puny amp can't muster that surrent at low impedances, therefore bad sound as the ohms dip, and I also make the assumptiont that the majority of the folks pushing these things have crappy receivers playing them)?? Do the heritage speakers have this drop in impedance too? (I have a trusty and recently rebuilt pair of Cornwall II's in different listening room with, yes, a crappy receiver for them as well (only listen in two channel there however), get the reason why I want to upgrade ALL round?) ---------------- As mentioned, the "drop" in impedance is a constant thing, but dependent on frequency. In other words, the impedance of a speaker is different at every frequency and we call it a drop because it looks like that on a graph. When a speaker is rated at 8ohms, the total average is generally 8 ohms, or 8 ohms at 1kHz (basically a meaningless rating). And as already mentioned, cutting the ohm load in half at a particular frequency means the amplifier ideally is sending twice as much current to maintain the same voltage. It's best to think of the amplifier as a voltage "changer" where the actual change in current is dependent on the speaker it's driving. The reason we're concerned about voltage is because the electromagnet force of our voicecoil is dependant on the voltage across the magnetic field. So if the resistance goes down, the amp doesn't notice that the current doubles because it's putting out the same voltage. This is all fine and dandy until you reach a point where the amplifier can no longer supply enough current...which means the voltage can't get any higher and the result is a clipping amp. Clipping for short periods of time are generally not realized as clipping, but rather more like a fuzzier sound (in fact, short enough clipping won't even trigger clipping circuits or even show the clipping lights). When driving a low impedance load (like at certain frequencies with the RF-7), the amplifier is using more current. This excess in current also results in an increase in temperature. This not only effects the normal characterstics of wire, but also effects the way a transistor functions. In order to fully understand transistors, we need an understanding of quantum mechanics so I'll pass on explaining how they work for now. However, a transistor works on the concept that extra energy needs to be added to the transistor in order to get the electrons in an energy state where they will flow freely. If our transistor is warmer, then it takes less energy to get the electrons to flow and at a certain temperature, the input voltage no longer regulates the transistor, which means you can't stop the current flow and it all melts down (this is why blowing an amp generally breaks speakers...you get a crazy amount of current flowing). It may seem intuitevly like it might take a while for this to happen, but it actually happens very fast. In the case of the RF-7, the low impedance drop may be just enough to stress the amplifier to a point where the transistors no longer act correctly and we get all sorts of wierd things happening. The impedance of the RF-7 at those frequencies may not be enough to blow the amp or anything like that, but it could be enough to push it into a nonlinear region...and again, it doesn't take long for the extra current to cause this to happen (like on the order of under 1 second). An amplifier capapble of pushing more current generally has better cooling capabilities and you no longer have this issue (granted, there could be other drawbacks to the higher current design which explains why higher power amps don't always sound better). ---------------- You also mention a ragged frequency response, what exactly, does that sound like? I can go to a high end audio store all day long, and no body be able to show me, by example, a "ragged frequency response" - Do you have any specific movie or music examples, when I make a side by side comparison, I could hear the response on a big box receiver or a quality theatre or two channel amp, all other things considered equal? What happens, say when one of these sound transients comes along and the receiver can't meet the current requirements? Does the moment pass silently by, does the receiver belch it out as noise, does the receiver clip, what?? I am really more interested in the silence AFTER the transient, in other words, will I be able to hear quieter passages more clearly with a separate amp, or will I have to keep turning up the damn volume, or more specifically changing the balance of the speaker volumes depending on the movie? Will the receiver just clip and die ( I can dream can't I, make the wife more amenable to the upgrade!) ---------------- A jagged frequency response sounds muddy...the most noticeable attribute is that a more jagged response makes it harder to localize the sound. So when comparing two systems with your eyes closed, it should be able for you to picture where the intsruments are located on the system with a smoother response. If you want, I could make some recordings of some sounds with a smooth response and then introduce a jagged response and you could AB the difference. As far as differences between amps... a better amp is like looking through a cleaner window. It's possible to see through both windows, but the image is clearer when the window is cleaner. With a better amp, there is less "noise" that you need to listen through in order to hear the intended parts of the music. I can't think of a better way to describe it. ---------------- Next question, I have seen amps that are heavier than hell, but does that necessarily mean high current/wattage or quality? Is the Sunfire series just smoke and mirrors, as the CG 400~7 weighs only some 40 pounds? I have seen some great reviews about warmth and the "down tracking" power supply, is this just hocus-pocus, and would I be better served getting a real behemoth amp that runs hot and is a hulking steaming pile of power (oooh, that was almost poetic, I like the visual, cut to a picture of the Levinson monoblock towers for sale on 'gon, I bet I could cook an egg on those things when they are rocking). I am getting closer to enlightenment boys, now just bring me home. Thank you for your responses, truly...I greatly appreciate you sharing your learning... K ---------------- Amps are heavy because of their heat sinks. A heat sink is basically a piece of metal that conducts heat very well and they shape it in such a way so as to increase its surface area. Heat from the working electronics in the amp then get transferred into heating this piece of metal, which then gets cooled by the air (water would be cool, but we're dealing with electricity here...). As we all know from chemistry class, a larger surface area means the metal will cool faster. The metal will also cool faster if we blow air past it as well, and even faster if we blow compressed air past it. However, fans are a no go in a home environment because they're too noisy, so the only solution is to build a really large heatsink or design a more efficient amp (an amp that doesn't get as hot...like A/B or D class amps). Don't forget, heat is the enemy of a transistor so it's not something to be taken lightly...in fact, most amps nowadays have protection circuits on them that will shut the amp down if it exceeds a certain temp (which is good because it saves the speakers too). Though it's unnerving to test, a good amp will shut down in time even if you short the output. I mentioned different classes of amps...I don't want to get into all the details, but they all are different ways of supplying the current and have their advantages and disadvantages. Class A is your straight up "normal" amp, but it runs very hot. AB is the compromise here that uses A for the first few watts and then uses a B source for when the current demand exceeds a certain limit. Class D amps are typically only used for subwoofer applications. Quote Link to comment Share on other sites More sharing options...
mwright31 Posted May 23, 2005 Share Posted May 23, 2005 Does anyone know if the Yamaha RX-Z9 would have any problems with the RF-7's? My configuration is listed below Mitsubishi WS-65711 Yamaha RX-Z9 2 RF-7's 1 RC-7 2 R-5800-W (Side Surrounds) 2 RS-35's (Surround Back) 1 RW-12 Thanks, Mike Quote Link to comment Share on other sites More sharing options...
Kriton Posted May 23, 2005 Share Posted May 23, 2005 Guys, thanks! I can't tell you how much I appreciate your responses, and I also understand that you ahve better things to do then educate a newb like me, that last post must have taken an hour! I am starting to get it...As a matter of fact, i am noticing some problems with my current set-up (crappy receiver and RF-7's with full Klipsch synergy surrounds) that fits exactly with what you ahve said...it is nore noticeable as a drop off in sound when there are dynamic highs...the drop-off is noticeable, and annoying as hell...the sound level drops the dialogue garbles, and the the sound, slowly begins to come back...almost imperceptibly at times. Does Carver really overstate his power outputs? Hey, is there any way to make the explanatory posts above a sticky of some kind, to place in a reference section, this should be memorialized for the masses. I am still at a loss as to the best amp, pre comnination, and whether it will be worth my while to get a kick-*** amp and wait on the pre for a while (using the receiver as a pre)? I know if I ask amp recommendations, I will get as many as the sun, from all different orners of the spectrum...I was looking at, and mention frequently, Sunfires, because I have a friend whose Sunfire I have listened to frequently, and I loved the sound (of course the Martin Logans didnt hurt either)... Thanks again! K Quote Link to comment Share on other sites More sharing options...
Deang Posted May 23, 2005 Share Posted May 23, 2005 http://www.audio-ideas.com/interview/carver.html Quote Link to comment Share on other sites More sharing options...
Spkrdctr Posted May 23, 2005 Share Posted May 23, 2005 If you are bound and determined to buy a high powered amp, get the Sunfire. As you know, you have heard it and it sounds awesome. Don't worry about the power, the Sunfire line is very high current and will provide all the power you need. I'm appalled that anyone thinks they need to listen to speakers above 102db other than for just the briefest peaks. This is ear damaging levels. So, listening to an RF-7 set up with a reciever at less than 102db, means that you are using less than 1 watt, most likely .750mw. It is darn near impossible to, oh heck, it is impossible to stress a reciever of the cheapest 100 watt type when using 750mw of thunderous power. But, again, if you want to buy power, then go for it. But, it is not needed unless you have a very large room to fill or want ear deafening levels with little to no clipping. In the end, buy what you like and enjoy it, ther are worse things than being a Klipschoholic in life! Quote Link to comment Share on other sites More sharing options...
MrMcGoo Posted May 23, 2005 Share Posted May 23, 2005 Michael, Re: Yamaha flagship on RF-7s You will get good sound from the Yamaha, but would get better performance from a separate amp. Most receivers use a a single pair of MOS-FETs for each channel. A single pair of the best output devices will heat up and play out of their linear region as well as limit current. Separate amps use many pairs of output devices to avoid there problems. Receivers have very limited space for output devices. The receivers that do not limit current are Sunfire, B&K, Harman Kardon and NAD. Bill Quote Link to comment Share on other sites More sharing options...
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