Matching sub for RF-7's

[Zen Traveler]

I power the RF-7's with only 40Watts a channel in stereo-mode which is more then enough for me askbob1

Even in surround mode,.. where there is only 30Watts a channel, they still go very very loud.

Today a guy came by and brought his Denon AVR-1909 receiver with him to check if yhe Audessey-function on that receiver could solve my "low"problems.

I have no experience with HK AVRs but have had considerable experience with Denon. I don' think the Denon AVR 1909 (or any bottom of the line AVR) has enough current to drive those RF-7s efficiently and is the reason you are not getting the low end that you want from them.

[redux999]

I have no experience with HK AVRs but have had considerable experience with Denon. I don' think the Denon AVR 1909 (or any bottom of the line AVR) has enough current to drive those RF-7s efficiently and is the reason you are not getting the low end that you want from them.

Not enough current even at low volume ... is it that what you mean tkdamerica ?

[CECAA850]

The RF-7's shine with good amplification, more than what some receivers can supply. A stout 200wpc (or so) amp will drive the bottom end much better than an AVR.

[CECAA850]

Edit to above post. When you're watching movies, I would still recommend a sub as a good sub will dig lower than the RF-7's can. You'll need that for the LFE channel.

[twistedcrankcammer]

I have no experience with HK AVRs but have had considerable experience with Denon. I don' think the Denon AVR 1909 (or any bottom of the line AVR) has enough current to drive those RF-7s efficiently and is the reason you are not getting the low end that you want from them.

Not enough current even at low volume ... is it that what you mean tkdamerica ?

redux999,

That is exactly what he means.

Redux, in a good sub amp, you will notice that the class D amplifiers have a huge range of wattage output in the RMS wattage output vs: their peak wattage output. example; on my velodynes, 1250 watt rms, but peak wattage of 3000 watts. Good Bass extension doesn't need continuous or rms wattage the way it needs that peak wattage capability to slam home an explosion.

On a stereo rig, a good solid state amplifier has large capacitors to store power for when it is needed. On my 200 watt / channel stereo amplifiers, I have 4 capacitors the size of pepsi cans only taller in each 2 channel amplifier, that is the reason why my amps weigh 67 pounds each. I use 4 of these stereo amps for surround sound. These large capacitors hold more in storage than little capacitors do for slamming a bass note, even at lower volumes, the reserve is there and improves low listening volume bass output.

Now when you have a receiver with 5 or 7 channels, you not only have to fit in the capacitors for 5 or 7 channels of amplification, but you are cramming in a control amplifier and a tuner as well, and I bet your whole receiver does not weigh half of what one of my amplifiers weigh, it is a comprimize to give the most features in the smallest space, for the cheapest price, and there is no way you can fit in a buch of huge capacitors in a reciever to help with the low end on your speakers at low listening levels.

For comparison, some Krell stereo amps can weigh 150 pounds just for the one amplifier!!

Roger

[michael hurd]

Many small capacitors can store as much or more than equivalent in large cans, and if the voltage is higher ( say they step up the voltage @ inlet ) can store more energy than a lower voltage system. ESR matters, and also many small caps charge faster than a few pepsi can sized ones.

[twistedcrankcammer]

Many small capacitors can store as much or more than equivalent in large cans, and if the voltage is higher ( say they step up the voltage @ inlet ) can store more energy than a lower voltage system. ESR matters, and also many small caps charge faster than a few pepsi can sized ones.

Mike,

I would not try to tell you how to build a sub, but give me a F$@KIN break!! I was in electrical engineering before I went into the medical field, do you really want to stick with this tripe?? [bs] [bs] [bs] [bs]

Roger

[askbob1]

totally being an un-biased smarta$$ here, but.... have you been to a concert lately and seen the wall of bose acoustimass cube speakers!? [:|]

[SWL]

????

[TheEAR]

Nah nah nah some still do not grasp a simple concept !

It is not you need anamplifier with a huge wattage rating to drive the RF-7 propely,you need n amplifier capable of driving more complex and changing loads that varry with frequency. The RF-7 have dips in the load they present to an amplifier depending on frequency.

This is what makes receivers sound anemic when powering the RF-7's.

Take a tiny Parasound Zamp 45 watts/ channel(60W into a 4 Ohm load) and it beats flat most if not all receivers under $1000 amp sections(in two channel mode driving the RF-7's full range).

Now take a Parasound Halo A21, this amp is rated at 250 W into a 8 Ohm load and 400W into a 4 Ohm load. This unit wakes up RF-7's like no receiver can(besides the very large Pioneer reference receiver(~$6000) with ICE amp modules(also used by BelCanto and a few others)that receiver is damn close to the large Parasound.

Fact is ALL the budget receivers have more or less anemic power amp section,ALL of them. I use power amps since many years and ditched receivers(even a Denon 5802)in favor of the stand alone power amp,where I pay for the actual AMP. And not 57000 worthless echo modes(called DSP acoustic simulations worth ZERO value).

Yamaha is one of the most funny ones,a truck load of bull DSP modes. Read sound coloring garbage no self respecting audiophile will ever use.

I dare you to take YOUR receiver and compare with a good quality separate power amp and not notice a gain in bass control and the speakers come alive.

Run the RF-7 full range. The gain is real and too obvious.

I now use the Parasound JC1 monoblocks with RF-7's...they are alive and kicking.No receiver can match that setup.

[twistedcrankcammer]

The EAR,

Your Parasound Halo JC1 mono blocks are very similar to a Nakamichi PA-7 if it were bridged mono. Your Mono blocks put out 400 watts rms using 4 x 33,000 microFarad output capacitors for a total of 132,000 microFarad of filtering output capacitor.

Likewise, my Nakamichi PA-7s use 4 x 33,000 microFarad output capacitors for 2 channels at 200 watts rms, so I have the exact same ratio at 1/2 the power.

If you had 7 JC1 mono blocks, you would have a total of 924,000 microFarad of capacitance.

As I have 8 channels, but only use 7, I use 462,000 microFarad of capacitance.

No 7 channel AVR made can match these numbers, but let's examine the post that bothered me.

Many small capacitors can store as much or more than equivalent in large cans, and if the voltage is higher ( say they step up the voltage @ inlet ) can store more energy than a lower voltage system. ESR matters, and also many small caps charge faster than a few pepsi can sized ones.

I want to examine this post 3 ways:

A) First; the meaning of the post, was it meant to be helpful to the discussion at hand??

The poster that I directed my comment too, was not sure of the reason of a previous post as to why he did not have enough bass at low volumes. I tried to simplify this for his understanding, so coming in with discussion on ESR, is clearly not putting things at an understandable level for the person that asked the question, so I descipher that it is supposed to be to me.

At this point, I try to decypher if the post is humorus, supposed to be informative, or to complete something I left out, or correct something I stated that was wrong.

Let's go too examination number 2; Let's go to mister Rogers neighborhood to visit King Friday in the land of make believe an pretend that everything in that post is correct. (everyone pretending now??)

Even if we belive that we can come up with similar capacitance levels from many tiny capacitors, we are comparing AVRs, and budjet AVRs at that, but I will conceed that even at the highest level of any AVR produced, I do not think anyone can show us an AVR with my output capacitance of 462,000 microFarad, let alone what would be 924,000 with 7 mono blocks like yours, so I guess we build this AVR with all of these wonderful little capacitors that will equal or better these amps.

C) Time to evaluate this post in the third way, back to real life;

Let's check the validity of the statements??

1) "Many small capacitors can store as much as or more than equivelent in large cans". --- Well yes, that is possible, but it would require even more space.

2) "and if the voltage is higher (say the step up voltage @ inlet) can store more energy than a lower voltage system." --- Let's study this one for a moment, there are many different kinds of capacitors, and I think it self evident that the more expensive ones are more likely to be in the higher end piece, but for discussion sake, let's pretend they are of the exact same makeup, and we want to use the equivelent in smaller capacitors, but we want to use capacitors that we can step the voltage up on.

A capacitor has a dielectric between two metal plates. Assuming that we are using a bunch of the exact same capacitors, with the exact same dielectric, and the same voltage rating, except the small capacitors need to equal up to the same capacitance value, we will end up with the exact same surface area of the two metalic plates and dielectric.

So what about stepping up the voltage?? ---If you step up the voltage above the capacitors rating, the voltage (or push of a circuit) will arc through the dielectric making a small mushroom cloud of smoke, a bang, and an unusable capacitor.

So how do we increase the voltage rating of the capacitor?? --- That is easy, we increase the thickness of the dielectric, but there is a catch, as we increase the thickness of the dielectric, we increase that dreaded "ESR", and we loose capactance value, so to regain that capacitance value, we have to increase the size, or area of the two metalic plates and dielectric. (Suddenly those many small capacitors are getting larger!!!).

3) "ESR matters" --- Well, I am inclined to agree with that, but for the less informed, let's discuss what ESR is; For those in the medical field that know ESR as Erythrocyte Sedimentaton Rate, or a coag studdy, in this context of capacitance and circuits, it stands for Equivelent Series Resistance.

Equivalent Series Resistance rating of a capacitor is a rating of quality. An imaginary perfect capacitor would have an ESR of zero. Since we live in the real world, all capacitors have some ammount of ESR.

4) "and also many small caps charge faster than a few pepi can sized ones" ----- Well No, that is incorrect. We are not talking batteries here, we are talking capacitors.

Roger

[askbob1]

????

please tell me someone got that...

[TheEAR]

High power(rated at say 200-300W/channel) amps are NOT needed for any larger Klipsch speakers,this is a false and uterly chilish myth started by people with audio knowledge of a..." insert funny qualifier ".

What you need is an amp capable of ~40-50W honnest watts capable driving difficult(at times) loads. Again take a Parasound Z amp (45w/channel) and you will hear it beat a Yamaha/Denon...(list the budget receivers here) receiver rated at 100W /channel.

CURRENT is where it is at. Forget the low ERS,JPS,MTS(joking) turbo hooopla matched ultra speed caps...it is hoopla to put soap in your eayes and ears and make you buy a "new" old technology. Fact of the matter is you will NOT hear these speed gain,as human ears start to roll of way before 20KHz and the BS claims to 2GHz and more are there to sell the product.

Be it banks of small caps or a few larger "can" sized caps,if implemented well you can have an outstanding amp(Krell,Mark Levinson and SimAudio all use HUGE cans and sound AMAZING(beating the snot out of too many pro type amps using banks of small caps).It is all in the know how of the engineer ,not in what looks great on paper.

Same with the false myth small woofers 8" in dimameter are faster than a 15" woofer. Faster at what? Reproducing a 80Hz tone! Gimmie a break,a BREMBO break.

It is not about the cap size but the aproach taken to get high current when needed. Look at BelCanto and NuForce amps...tiny,puny looking and deliver GOBS of low end "torque" and drive difficult loads with aparent ease.

[Zen Traveler]

What you need is an amp capable of ~40-50W honnest watts capable driving difficult(at times) loads.

...CURRENT is where it is at....

Be it banks of small caps or a few larger "can" sized caps,if implemented well you can have an outstanding amp(Krell,Mark Levinson and SimAudio all use HUGE cans and sound AMAZING(beating the snot out of too many pro type amps using banks of small caps).It is all in the know how of the engineer ,not in what looks great on paper.

It is not about the cap size but the aproach taken to get high current when needed. ...

What do you think of this Denon AVR 4806 THX Ultra II driving an RF-7 bases HT in a slightly less than 2000 cu ft room: http://www.hometheaterhifi.com/volume_12_4/denon-avr-4806-receiver-12-2005-part-5.html

[askbob1]

Same with the false myth small woofers 8" in dimameter are faster than a 15" woofer. Faster at what? Reproducing a 80Hz tone! Gimmie a break,a BREMBO break.

hehe, i like that myth too. i like it when people say they like the 'tightness' of a small woofer. either they really don't like the impact of a sufficient woofer, or they have not heard how a larger diameter woofer controlled by a really good amp can sound.

[travis-g]

I JUST BOUGHT DUAL MFW-15 SUBS FROM AV123 TO GO WITH MY RF-7'S ALL I CAN SAY IS THEY ARE AMAZING MAKE SURE ALL YOUR PICTURES ARE BOLTED DOWN BECAUSE I HAVE ALREADY BROKE A COUPLE THE IMPACT WILL SCARE YOU

[twistedcrankcammer]

High power(rated at say 200-300W/channel) amps are NOT needed for any larger Klipsch speakers,this is a false and uterly chilish myth started by people with audio knowledge of a..." insert funny qualifier ".

What you need is an amp capable of ~40-50W honnest watts capable driving difficult(at times) loads. Again take a Parasound Z amp (45w/channel) and you will hear it beat a Yamaha/Denon...(list the budget receivers here) receiver rated at 100W /channel.

CURRENT is where it is at. Forget the low ERS,JPS,MTS(joking) turbo hooopla matched ultra speed caps...it is hoopla to put soap in your eayes and ears and make you buy a "new" old technology. Fact of the matter is you will NOT hear these speed gain,as human ears start to roll of way before 20KHz and the BS claims to 2GHz and more are there to sell the product.

Be it banks of small caps or a few larger "can" sized caps,if implemented well you can have an outstanding amp(Krell,Mark Levinson and SimAudio all use HUGE cans and sound AMAZING(beating the snot out of too many pro type amps using banks of small caps).It is all in the know how of the engineer ,not in what looks great on paper.

Same with the false myth small woofers 8" in dimameter are faster than a 15" woofer. Faster at what? Reproducing a 80Hz tone! Gimmie a break,a BREMBO break.

It is not about the cap size but the aproach taken to get high current when needed. Look at BelCanto and NuForce amps...tiny,puny looking and deliver GOBS of low end "torque" and drive difficult loads with aparent ease.

Are you a carver amp salesman, because the pitch sounds very familiar as far as 585 watt per channel amps with high current and no large capacitors. Are we talking primarily A class amps, or are we going to throw everything into the mix.

You contradict your own statement when you state that all you need is a 45 watt amp that will handle a wide variety of loads. You had that amp. yet you felt compelled to go into a whole nother price level on 400 watt per channel mono blocks from the same manufacturer.

If you really want to get into discussion, and delve deaply on how and why things work ?? OK, but your statements are opinion.

At whatever room size, plus the efficiency of the speakers, we need X number of watts, but what we really need is headroom. Considder the Nakamichi PA-5, it is only 100 watts per channel, or half that of the PA-7, yet it has 3/4 as much output capacitance filtration. This is exactly why the PA-7II has 225 watts per channel, and the PA-5II has 150 watts per channel. The capability was always there, but they sacrificed headroom for higher output specks.

Roger

[TheEAR]

Roger Anger,

Carver amps,I do not like Carver amps and own ZERO Carver amps. With 40W you have plenty when your speakers are 100dB efficient for a 1 watt input,measured 1 meter away from the speaker.

How loud do yo listen to? What room size? Distance from speakers to listening position. Tell me you seriously use more than 20W and over 100W on peaks.

Why did I buy Parasound's larger monoblocks,let me guess...because I like overkill. Like I needed or pushed even a 15W tube amp driving the efficient Klipsch in a small room. Why did I buy larger SimAudio amps...to drive speakers that probably not take all the amps can deliver? Because I like overkill.

Most importantly WHY do YOU sound so angry? It is obvous a more capable amp is a superior choice when you have the money and space. Even if it will be used ~10% (during some very loud and rare times you show it off).

I use 20 drivers in my sub system,WHY? Because I can and why ~50KW in amps ...because I can and this is my kind of fun.