Would large home amps drive small (3678) cinema speakers?

[kenratboy]

From reading this (and other) forums about using pro speakers for home use, I have come under the impression that while sensitive, these speakers need a LOT of power and a LOT of current to sound good, even at low volume levels.

For the small guys (like the 3678 screen channels), instead of using the DSi amps (I would use one on the subwoofer without question, partly for massive amounts of power, partly for the needed EQ features) for the speakers, what about big home amps?

For example, Emotiva rates this at 200x3 at 8 ohms.

http://emotiva.com/xpa3.shtm

Or Outlaw's version:

http://www.outlawaudio.com/products/7500.html

Would an amp like this be able to drive these speakers well for even a larger HT space (5,000+ cu. ft.) - or would there be real benefits of the DSi amps?

Thanks!

[jcrobso]

1st. The size and the acoustics of the room.
2nd. The sensitivity of the speakers.
3rd. What are you listing to.
4th. How loud do you want it to be?
There are other things also, but these are the first ones that came to mind.
Bass requires the most power and the biggest speakers. Also due to the response cure of human hearing. (http://en.wikipedia.org/wiki/Fletche...3Munson_curves) the bass needs to be 10~20db louder to be heard at the same level as a 4kHz tone. Also every time you double the distance from the speaker the level drops by 6db.
Pro speakers are designed to fill very large rooms and will require a big amp to do so.
Now in you living room they will just be loafing to give you 100db with just a couple of watts. You still need a big amp for the bass.

[kenratboy]

I guess what I am getting at is in response to what a few people here have said.

Simply because the 2226 woofer is such a beast, even at very low levels, it needs a lot of current to sound good (to literally get the woofer moving at all). I am not sure this is true, hence my question.

In theory, if I hooked up a $500 Denon or Yamaha to the 3678's, would it even sound good at low levels due to the relatively low current compared to a beefy home amp, or a DSi series pro amp?

[Robh3606]

In theory, if I hooked up a $500 Denon or Yamaha to the 3678's, would it even sound good at low levels due to the relatively low current compared to a beefy home amp, or a DSi series pro amp?

Why wouldn't it?? A small home amp could drive them in your livingroom. Even if you are using a seperate 1000 watt amp you would only be drawing a couple of watts so no real current draw. In general stand alone amps sound better but there is no reason to think it can't sound decent using an HT reciever to power them. Just try it out in stereo with whatever you have available. The whole idea is the be on the right side of the power curve. After the first 100 watts it's all just a couple of Db of headroom. Using that first 100 watts the best way you can is where it really counts.

Rob

[Tom Brennan]

Yes. I've had good results with 2226s with small tube amps even. They are sensitive and easy to drive, a few watts will drive you out of the house.

Those 3678s are interesting speakers, kind of a JBL version of an Altec 19 in a utility format. Price is nice too. Were I single I'd be tempted to replace my Martin Logans with a pair.

[jcrobso]

It is a beast because of how loud it can play with a BIG amp. I have used them in a large Church, I could shake the pews with them.

[kenratboy]

Yes. I've had good results with 2226s with small tube amps even. They are sensitive and easy to drive, a few watts will drive you out of the house.

Those 3678s are interesting speakers, kind of a JBL version of an Altec 19 in a utility format. Price is nice too. Were I single I'd be tempted to replace my Martin Logans with a pair.

Thanks. I guess I got bad info.

I am guessing the 3678's would not need a lot of power in a smallish room to play LOUD. However, I have had issues driving large towers with smaller amps. Flat, undefined bass. Put a bigger amp into the equation (my Primare, which I could probably use as a welder), and the bass was significantly better (along with the rest of the sound). Isn't some of this due to a higher-current amp that is able to grab and control the woofers, even at lower levels? Does damping factor and other parameters play into this?

One concern I had on the 3678 was the 90x90 horn. Is that too wide for home use (or does that mean you will need carpeting, and an acoustically-treated ceiling)?

And yes, it seems to be an interesting speaker. Big enough to make a project like this worth its while (come on, it can put out 'THX levels' in a commercial cinema!), yet I could see placing three of these on the floor below a screen without having to go through too much work (they are the same height as a tower speaker, and not much taller than a big center channel on a stand)

[Eaulive]

I guess what I am getting at is in response to what a few people here have said.

Simply because the 2226 woofer is such a beast, even at very low levels, it needs a lot of current to sound good (to literally get the woofer moving at all). I am not sure this is true, hence my question.

No offense intended but this statement obviously comes from somebody that lacks even the most basic knowledge of electronics.

The current draw is directly proportional to the voltage applied and the resistance of the load. There's no way to have more current flow in a given load without increasing the voltage, hence the loudness of the sound.

Any 8 ohms speaker will draw 1A when driven by a voltage of 8Vrms, no matter the amplifier.

[Ruediger]

Hi kenratboy,

what You heared may be based on facts. I am writing this with care because some “audiophile people” invent all kinds of junk theories and we must keep these apart from proper engineering sciences.

Below You find the abstract of an AES paper which describes the phenomenon You heared about (or a similar one). Well known designers of real world professional amplifiers such as Douglas Self take these things seriously. See "Self on Audio", year 2000, page 332, "Loudspeaker undercurrents".

The conclusion is not that the 2226 is so hard to drive and thus needs a super amplifier. The conclusion is rather that if You want to hear the full potential of good speakers You need a very good amp as well. If You had Bose speakers You would not need to think about this

Ruediger (proud owner of two Yamaha MX-1)

Peak Current Requirement of Commercial Loudspeaker Systems

Measured terminal impedances of several commercial loudspeaker systems are developed into their equivalent electrical circuits by using the Brune network synthesis method. The synthesized circuits accurately describe the properties of the load as seen by the amplifier feeding the loudspeaker system. A group of non-sinusoidal audio signal sequences, which cause the loudspeaker system to draw momentary currents considerably in excess of what could be expected from the rated terminal impedance is identified using computerized network analysis methods. The maximum value of peak current of peak current reported for a commercial loudspeaker system is 6.6 times larger than that of an eight ohm resistor. The current peaks typically last a few hundred microseconds. The current peaks are caused by simultaneous parallel excitation of several of the drivers of a multiway system, by summation of cancellation currents originating from the energy stored in the mechanical and electrical reactances of the circuit, and by impedance transformation effects in the crossover network. The results imply that for short periods of time, an amplifier should be able to drive, with full output voltage swing and without appreciable distortion, loads equal to a resistor of one ohm.

Authors: Otala, Matti; Huttunen, Pertti
Affiliations: Otamation Inc., Helsinki, Finland ; Polarpro Inc., Kuusamo, Finland(See document for exact affiliation information.)
AES Convention:79 (October 1985) Paper Number:2293

[Eaulive]

Hi kenratboy,

what You heared may be based on facts. I am writing this with care because some “audiophile people” invent all kinds of junk theories and we must keep these apart from proper engineering sciences.

Below You find the abstract of an AES paper which describes the phenomenon You heared about (or a similar one). Well known designers of real world professional amplifiers such as Douglas Self take these things seriously. See "Self on Audio", year 2000, page 332, "Loudspeaker undercurrents".

The conclusion is not that the 2226 is so hard to drive and thus needs a super amplifier. The conclusion is rather that if You want to hear the full potential of good speakers You need a very good amp as well. If You had Bose speakers You would not need to think about this

Ruediger (proud owner of two Yamaha MX-1)

Peak Current Requirement of Commercial Loudspeaker Systems

Measured terminal impedances of several commercial loudspeaker systems are developed into their equivalent electrical circuits by using the Brune network synthesis method. The synthesized circuits accurately describe the properties of the load as seen by the amplifier feeding the loudspeaker system. A group of non-sinusoidal audio signal sequences, which cause the loudspeaker system to draw momentary currents considerably in excess of what could be expected from the rated terminal impedance is identified using computerized network analysis methods. The maximum value of peak current of peak current reported for a commercial loudspeaker system is 6.6 times larger than that of an eight ohm resistor. The current peaks typically last a few hundred microseconds. The current peaks are caused by simultaneous parallel excitation of several of the drivers of a multiway system, by summation of cancellation currents originating from the energy stored in the mechanical and electrical reactances of the circuit, and by impedance transformation effects in the crossover network. The results imply that for short periods of time, an amplifier should be able to drive, with full output voltage swing and without appreciable distortion, loads equal to a resistor of one ohm.

Authors: Otala, Matti; Huttunen, Pertti
Affiliations: Otamation Inc., Helsinki, Finland ; Polarpro Inc., Kuusamo, Finland(See document for exact affiliation information.)
AES Convention:79 (October 1985) Paper Number:2293

You're gonna kill the poor guy, he doesn't even know what Ohm's law is and you're jumping right away into reactance and AC circuits

[Tom Brennan]

I am guessing the 3678's would not need a lot of power in a smallish room to play LOUD. However, I have had issues driving large towers with smaller amps. Flat, undefined bass. Put a bigger amp into the equation (my Primare, which I could probably use as a welder), and the bass was significantly better (along with the rest of the sound).

One concern I had on the 3678 was the 90x90 horn. Is that too wide for home use (or does that mean you will need carpeting, and an acoustically-treated ceiling)?

Well it's hard to tell how a given speaker is going to sound with a given amp. When I bought my Martin Logans I'd planned on using a 75 wpc Denon receiver that with my Altec 19s sounded great. But with the MLs the Denon sounded dead, flat and lifeless and my little EL 84 Jolida with about 15 watts a channel sounded much better. So I ended up buying a more powerful EL 34 Jolida with a claimed 50 watts a channel. And a remote, gotta have a remote.

IME&O 90 degree horns sound just right in most home situations; I've used horns as narrow as 60 degrees and as wide as 120. The 60s were too beamy and the 120s too diffuse though the 120s did sound kind'a neat bouncing sound off the side walls--BIG image. But too big and not as well "anchored" as 90s.

Note that these are my opinions and experiences in my rooms and with my associated gear; don't take any of this as gospel.

[kenratboy]

I know what ohms law is (I am vaguely familiar with TS parameters, mostly from using WinISD, reading some speaker design books, etc.), but I am certainly not at a point where I have a good grasp and the ability to interpret these numbers.

To take a step back, the issue was framed that the moving mass of the driver was so heavy, a wussy amplifier would have an issue controling the woofer. The amp would tell the woofer to move, but not have the ability to stop and reverse that movement. I personally do not have the knowledge to know if that is true or not, but *intuitively* it makes sense.

And no, I am not offended, I am grateful you are taking the time to teach me about the hobby I love.

If we were to boil it down to a more qualitative level - would the amps I have in the first post (~200 watt consumer home amplifiers) be able to drive these speakers easily to THX (105 db.?) levels in a ~5,000 cu. ft. room? Is there anything the DSi offer which would make them a compelling choice for these speakers in a home environment (I understand the DSi is the amp to get for a 4645C subwoofer).

[Tom Brennan]

To take a step back, the issue was framed that the moving mass of the driver was so heavy, a wussy amplifier would have an issue controling the woofer. The amp would tell the woofer to move, but not have the ability to stop and reverse that movement. I personally do not have the knowledge to know if that is true or not, but *intuitively* it makes sense.

They also have a powerful and sensitive motor to move the cone. How well the cone stops (transient response) is determined mostly by the cabinet design; cones heavier than that of the 2226 and with less powerful motors can be designed in proper cabinets to have excellent transient response.

I think you have plenty of power, 200 watts from a competently designed amp is alot no matter how you dice it. The speakers have a sensitivity of 98db so to hit 105db should take about 8 watts; I don't think dynamic compression is an issue yet at that low a volume.

But if you're really worried about it buy a couple QSC RMX 850s from Guitar Center for 325 bucks each. Those drove the 2226s in some bi-amped CS-3115s I had to house shaking levels with no sweat. I was probably using 10 watts.

[kenratboy]

How is the sound quality on those cheaper pro amps? I know compared to home gear, they are sold at MUCH lower margins, so $500 in the pro world might cost you $1000 in the consumer world. However, I have to imagine they are willing to cut a few corners in the sonics department for the sake of lower cost and higher power. I would rather spend a few more bucks to gets something that would really let the speakers shine.

[rlsound]

QSC DCA or CX amps are good pro amps for home use. Inrush protection so you won't pop breakers on power up, both lines are similar, although the gains is different.