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Matching amps to speaker efficiency

45.26.128.222
Posted on October 7, 2020 at 09:43:57
M3 lover
Audiophile

Posts: 6604
Location: SW Mich
Joined: May 29, 2005
Contributor
  Since: July 4, 2007
 Reading the post and comments below on the PASS X150.8 reminded me of a past experience.

For 19 years I owned and enjoyed Duntech Princess speakers. They were rated at 90 or 91 dB, so a little more efficient than an average model. However the owner manual recommended "at least 200 wpc for musical enjoyment". From my own experiences in auditioning amps over the years I was always puzzled by that relatively high efficiency rating. I suspected it was based upon ratings for the selected drivers rather than an actual measurement of the completed speaker.

My knowledge of electronics is very limited but I suspected I figured out why those speakers seemed to demand greater power than their efficiency rating would suggest. First, the 1st order crossover was very complex and so contained a number of parts. Not as bad as the link photo but the PC board was loaded. Second, the impedance curve dropped just below 3 ohms in the bass range. That had to demand a fair bit of power.

After trying numerous amps over the years I found two solutions that made the speaker come alive. I was using a pair of VTL 300 mono amps which were quite good. On a whim I borrowed a pair of VTL 225 monos and connected them for passively bi-amping. The speaker had a bi-wire option so I was still going through the internal crossover. That combination was amazing, but 4 amps and 32 output tubes was not practical for me. I finally settled on JC-1 mono amps rated at 800 wpc into 4 ohms. That was my final solution. Regardless if it seemed to be overkill for 90 dB speakers.

The moral of my story? You can't rely on speaker ratings when considering amp choices. You may need to research the speaker specs, and still experiment with amps.


"The secret of life is honesty and fair dealing, if you can fake that you've got it made." Groucho

 

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RE: Matching amps to speaker efficiency, posted on October 28, 2020 at 11:02:19
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
 2 things we are NOT told.
Sure, speaker may be at or near the sensitivity the manufacturer calls out.
BUT?
What is the reactance of the speaker in terms of looking like a capacitor or inductor at various frequencies?
What is the Ability of the various amps to work into such a load? Some amps.....are very incapable when presented with a highly inductive or capacitive load.
Too much is never enough

 

Hey Tim! I had some Vandersteen 3A's and ...., posted on October 9, 2020 at 11:27:25
Cougar
Audiophile

Posts: 4593
Location: SoCal
Joined: June 25, 2001
 These were really nice sounding speakers but one day I was at Jeff's Sound Values and Jeff let me barrow some Classe M-700 mono blocks he had just got in. First off, these were some heavy amps. Anyways, I hooked up to the Vandersteens and I could not believe how much better the Vandersteens sound. Sound was so close to sounding real I just couldn't stop listening. If it wouldn't have been for the weight if these amps I would have bought them.

So what I have found out since then that every time I use a good amp with alot of power 300+, the speaker sound way better. The only draw back is if you accidently drop a needle down on the record or forget you have the volume up too high when turning to another station or selecting a different input while music is playing, you could damage your speakers. Other than that, more power is always good! :)

 

RE: Matching amps to speaker efficiency, posted on October 8, 2020 at 23:02:14
RGA
Reviewer

Posts: 15177
Location: Hong Kong
Joined: August 8, 2001
 Generally speaking, I find it is far simpler to go to your local dealer and try the speakers with the amp you intend to use. I have read far too many comments that run counter to each other on these "will X drive Y speaker?"

Some people say that their 85dB speaker is happy with a SET while someone else will moan that their SET doesn't drive their 98dB sensitive Klipsch. So then you get into endless discussions on how many drivers being too much for a SET or which SET or quality of power supplies - or such and such speaker isn't as sensitive as claimed - or impedance and phase at Z frequency is why it doesn't have enough power.

I sort of think - okay but if you bring a few torture tracks to the dealer and you play the SET or other low powered amp and you play it louder than you would ever play it in your home and the result is satisfying then I really don't care if some other speakers is 5dB more sensitive or will play 8dB louder.

The point is not paying for something you won't use. If the speaker amp combination plays all the music you listen to and at a level you like then "success" you have found the right system for you. Tour ears can tell you all this all on their own without ever needing to read the specs or graphs. If you need the specs and graphs to tell you, because you can't hear it, then this is probably not a hobby or avenue to put in any serious money.


 

RE: Matching amps to speaker efficiency, posted on October 7, 2020 at 19:05:04
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 "1st order crossover was very complex"

I guess I don't know much about crossovers. My 1st order crossovers consist of one coil for the woofer and one cap for the tweeter with a series resistor to match the tweeter's efficiency to that of the woofer. Anything but complex.

I totally agree with bare. "Complex Crossovers can and do Suck the power."

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

Princess complexity, posted on October 8, 2020 at 10:32:29
M3 lover
Audiophile

Posts: 6604
Location: SW Mich
Joined: May 29, 2005
Contributor
  Since: July 4, 2007
 Hey Tre',

The Duntech Princess has been unavailable in the US for years now and didn't sell in big numbers when it was. So not likely many Inmates are familiar with them.

It was a 5-driver, 3-way design in a very large sealed cabinet. It followed the D'Apolito array design. John Dunlavy favored time/phase coherent designs.

The Princess crossover PC board was mounted on sliders and could be accessed from a panel on the back of the cabinet. An audio buddy with pretty deep electronics experience brought over a 30 or 40 watt stereo tube amp he'd built to audition on my speakers. He suspected that should be adequate for a 90-91 dB speaker. His amp fell flat, it was lifeless in driving the speakers. So he ask about the crossover design. I didn't know enough to explain it so I opened the back to show him the board. When he saw the crossover he joked that if it had a transformer added it should be able to power the speakers. Sorry I don't have a photo to share.

"The secret of life is honesty and fair dealing, if you can fake that you've got it made." Groucho

 

RE: Matching amps to speaker efficiency, posted on October 7, 2020 at 20:34:49
hahax@verizon.net
Audiophile

Posts: 4310
Location: New Jersey
Joined: March 22, 2006
 Almost no drivers are really flat. More complex crossovers are never pure 2nd or 4th order but also include equalization to flatten the response. This can be done if there are enough parts to do both equalization and crossover.

On a pure 1st order crossover there are only enough parts to do both jobs, only the crossover portion. So many designers first equalize the drivers to flat and then apply the simple first order crossover. And you end up with zillions of parts for what began as a simple problem.

If you do a simple 1st order electrical crossover, due to driver problems and interaction you probably don't end up with a 1st order acoustical crossover which is what you want. And you probably end up with crazy stuff at the extremes of the crossover/speaker becaus it doesn't roll off fast enough to go low enough inlevel where a driver really goes crazy. But you do get a simpler load on your amp which probably makes it work more easily.

 

RE: Matching amps to speaker efficiency, posted on October 7, 2020 at 19:18:05
B. Scarpia
 1st order crossover was very complex"

I had the same though. Nothing simpler than a First Order unless the Woofer is allowed to roll off without a coil.

Many parts smells like a L-R 4th Order.

 

RE: Matching amps to speaker efficiency, posted on October 7, 2020 at 19:32:06
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 My only other thought was maybe the drivers have server FR problems and there is an attempt in the crossover to fix that? That would make even a 1st order crossover complex.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

Must also consider (low) impedances and (severe) phase angle, posted on October 7, 2020 at 12:45:01
Brian H P
Audiophile

Posts: 1291
Location: Oregon
Joined: December 18, 2012
 Particularly in the bass. Highly sensitive speakers can still require LOTS of current from the amp, even if they don't need much voltage to put out high SPLs.

First-order crossovers, with the minimum possible number of reactive components in series with the drivers, are often anything but "simple," as they may require multiple components in parallel with the drivers to whip their responses and impedances into a shape where the series filters will actually work as intended. These parallel circuit elements may drop the impedance of each driver/filter section to a point where only high-current amplification will be suitable.

First-order "quadrature" filters (both drivers -3dB with 45 degree phase shift at crossover), combined with physical time-alignment of the drivers, used to be the only way to obtain a perfect step response and non-horrible square wave on the (very narrow) design axis. Multi-amped systems with DSP active crossovers have largely rendered this approach irrelevant, as they allow perfect time/phase alignment in combination with steeper filter slopes. Pat McGinty of Meadowlark used to be a champion of first-order passive crossovers, and is now a big cheerleader for DSP.

 

Reasonably astute observations.., posted on October 7, 2020 at 10:08:58
bare
Audiophile

Posts: 1879
Joined: April 14, 2009
 Clearly not All Audio weenies are mouth breathers :-)
I have found similar over my years in this.
Complex Crossovers can and do Suck the power.
Often the dynamics out of speakers..but that's a pointless digression.. here.
Really Does illustrate just How 'competent' (or at least dishonest) Makers are .
Did they Not measure their product for efficiencies during development?? And yet they produce misdirection info, in hopes of 'mo' sales. Interesting industry.. ain't it.

 

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