High Efficiency Speaker Asylum

Need speakers that can rock with just one watt? You found da place.

Return to High Efficiency Speaker Asylum

Message Sort: Post Order or Asylum Reverse Threaded

Bass control with low powered tube amps

161.185.150.82
Posted on October 24, 2016 at 07:41:16
tomtom58
Audiophile

Posts: 16
Location: New York
Joined: December 28, 2004
 I've always read that high efficiency speakers can be very dynamic and realistic with very low powered tube amps (does this mean SET or push-pull?). Suppose we take lets say some Klipsch Forte speakers at about 97db efficiency and hook them up to a 5wpc SET amp. Will the SET amp have good damping for the 12" cone woofer even though there is plenty of power? Would a lower powered push-pull amp at say 25wpc be better than a SET? In other words, can one get great dynamics and control out of the low powered tube amps and if so is one design, SET or push-pull, better for this?

 

Hide full thread outline!
    ...
RE: Bass control with low powered tube amps, posted on October 24, 2016 at 07:52:11
Tre'
Industry Professional

Posts: 17296
Location: So. Cal.
Joined: February 9, 2002
 "Will the SET amp have good damping for the 12" cone woofer even though there is plenty of power?"

No, but a high efficiency 12" speaker should not need much damping from the amp.

It should have a very strong magnet with a very tight voice coil gap and be self damped.

Having said that, a speaker of this type will not have much low bass.

I love low powered SET amplifiers but I only use them for the midrange and tweeters.

My JBL 2231 15" woofers are driven by a SS amp crossed at 200Hz.

This lets the low powered SET amps do what they do best without asking them to do what they can't. (drive the type of speaker that does have low bass but needs damping from the amplifier)

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

 

RE: Bass control with low powered tube amps, posted on October 24, 2016 at 08:00:53
rogerh113
Audiophile

Posts: 507
Location: San Francisco South Bay
Joined: October 20, 2014
 Personal experience with my Forte I speakers. I had a Primaluna Prologue power amp rated at 35 wpc. Tube selection I had to improve the sound may have pushed that down a fair amount. It sounded OK to me at the time, but my wife did comment on the lack of bass - I just thought it was 'clean'. I wanted to hear SET, and stumbled into an opportunity to build a 50 wpc SET amp. The bass difference is night and day from the Primaluna. In retrospect there was little bass - whatever power the Primaluna was putting out was inadequate, or maybe crappy caps rolled off the bass. If it was just the caps, then perhaps a lower powered amp would be ok with the Forte.

My guess is that the big woofer is going to demand a bit of drive, more than the squawker and tweeter, and that is where performance will suffer with a lower powered amp. I cannot recommend SET enough - it is lovely, and well worth experiencing. I would not go back to push-pull. If you read the SET posts, the ongoing issue with SETs is lack of power. There is sort of an ongoing focus on first watt, and a trend to low level listening. It is a tradeoff for the experience, and generally the tradeoff is wonderful mids and highs and somewhat deficient bass. There are tradeoffs in almost everything.

My experience - others may well disagree.

regards -- Roger

 

Damping isn't an issue, posted on October 24, 2016 at 09:24:32
Bill Fitzmaurice
Industry Professional

Posts: 5370
Location: New England
Joined: October 20, 2002
 This explains why damping isn't particulary important:
http://www.diyspeakers.net/Articles/Richard%20Pierce%20DAMPING%20FACTOR.pdf

 

RE: Bass control with low powered tube amps, posted on October 24, 2016 at 10:25:20
kitch29
 My JBL 2226s are 97dB but have very stiff cones with little Xmax of 8mm.
The motors (magnets) however are 12 pounders which exercise tight control; these speakers are known for their very low distortion. They also have a benign impedance curve.

All these factors make them ideal for use with both my direct-coupled, DHSET, 1.8 watt 45 and 6 watt single-ended KT-88 amps. The 45 is run in Parafeed configuration with very high quality plate chokes and output transformers. The bass is very nearly as powerful and controlled on, say, the 45 RPM re-issue of Aaron Neville's Warm My Heart as with my Mullard 5-20 style, 60 watt mono blocks.

What neither amp can do as well as the 60 watt Mullards is present accurate textural portrayal of dense orchestral scores, especially orchestra and chorus like the Mozart Requiem or Mahler Second.

I have also split the amplification as does Tre' and that yields improved bass response with the real benefit being improved "SET-ness" of the...SETs midrange and treble. If I hadn't gotten old and moved to an apartment I'd still be bi-ampli-sexual. ;-}

Some say the large Altec woofers with their higher efficiency solve this issue but I've built the 8 cubic foot cabinet with 16" co-ax 416s and find they have what a friend calls "bungee chord" bass.

What was the question again?

 

RE: Bass control with low powered tube amps, posted on October 24, 2016 at 11:54:31
Grinnell
Audiophile

Posts: 709
Location: Front Range
Joined: December 23, 2007
 I use a Gommes PHI-26 a single-ended, Class A EL84 integrated amp (1.8wpc triode/6wpc pentode)with my Klipsch Quartets. Seem to have plenty of bass.

Had 10 wt Vista Audio el84 amp and I had to tame the bass it was too much

 

RE: Bass control with low powered tube amps, posted on October 24, 2016 at 13:20:36
91derlust
Audiophile

Posts: 1101
Joined: December 25, 2014
 I get satisfying bass from my 3W SET system, but my preferences might be different to yours. To me, it is tuneful, flowing, well-timed and reaches about mid-high 20s (assessed using test tones). My Drummer friend calls it natural and effortless; it is not teeth-rattling though. It is not the typical bass you hear from small long-throw drivers driven by massive solid state Watts.

Caveat: my speakers were designed specifically to work with SET amps in my room - this makes a difference - but my amp power supply could do with some redesign to improve bass performance.

Cheers,
91

"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

 

RE: Damping isn't an issue, posted on October 24, 2016 at 16:02:58
Tre'
Industry Professional

Posts: 17296
Location: So. Cal.
Joined: February 9, 2002
 Most SET amps have a damping factor of 3.

A damping factor of more than 20 makes no real difference.

With some speakers a damping factor of 3 vs. 20 will make a difference.


Tre'


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

 

RE: Damping isn't an issue, posted on October 24, 2016 at 19:23:41
hahax@verizon.net
Audiophile

Posts: 4306
Location: New Jersey
Joined: March 22, 2006
 I second your statement. A factor of 20 will cause variations of less than a dB. But be sure to use thick enough wire so it doesn't affect the damping factor of the amp.

 

RE: Bass control with low powered tube amps, posted on October 24, 2016 at 19:35:55
hahax@verizon.net
Audiophile

Posts: 4306
Location: New Jersey
Joined: March 22, 2006
 Any tube amp with few exceptions will interact with a woofer and boost bass at speaker impedance peaks, the box resonance and the port resonance. This is true for any amp with high output impedance(low damping factor) tube or not(some solid state amps without negative feedback). How high the bass resonances depends on how high the impedance peaks and how high the output impedance. Wire too thin will increase the affect by making the effective damping factor even higher.

Push/pull tube amps tend to have higher damping factor because they usually use negative feedback where SET amps rarely do. But the damping factor is still poor enough to affect frequency response in almost every case, just less so. The only tube amps I know with little affect are the old Melos amps with a damping factor of 20 but these are very high power pus/pull amps although they are triode output and they do use a fair amount of feedback.

 

IME the room's resonances, spkr positioning, and the speaker's onw Qtc dominate and DF is out of the race, posted on October 24, 2016 at 20:14:48
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
 Not HE, and no SET experience, either. SEUL yes.

But I've used critically damped QB3 RB speakers for a long time, carefully positioned at unequal path lengths from side wall, floor and front wall.

When I first put valve power amps into the system, a rebuilt Radford STA15 but still using a VR, there was very little difference in the bass.

But the Radford STA 25 - also provided in the same loan - and with a much higher storage PSU, sounded a whole lot better in the bass. I listen to acoustic organ music at least once a week, so I know how difficult reproducing that is.

I have persisted with rebuilt push-pull classic valve amps ever since, with SR SS diodes and great big PSU caps and high storage.

IME a high storage PSU PP valve amp of even just 20WPC can sound a LOT more powerful, and in control than any similarly powered SS power amp, even a medium power Class-A with a necessarily big PSU.

PSU storage is 1/2 the capacitance times the voltage squared. Valve amps have a big advantage when bass power demands are highest.

My current pair of modified 'once were' LEAK Stereo 20s have an output Z of 1.5 ohms at 100 Hz IIRC when the 8 ohms taps are connected.

I will soon be using them strapped in parallel, giving 40 Watts RMS in pentode, and on their 4 ohm taps, which in parallel is a virtual 2 ohm tap. I don't know how low the opt z will be but it will be low. ? Driving QUAD 63s.


Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

I knew that, but couldn't lay my hands on the data, thanks. , posted on October 24, 2016 at 23:55:59
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
 Bookmarked.


Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

RE: Bass control with low powered tube amps, posted on October 25, 2016 at 05:03:48
SETguy
Audiophile

Posts: 35
Joined: July 4, 2015
 Take a look at the "Talkin Tubes" section of the Klipsch forum which is devoted exclusively to using tube amps with their speakers. There are some very talented designers and builders hanging out there who can guide you into amps which will offer the proper synergy with the speakers. With a properly designed SET, bass is absolutely not an issue.

 

Damping isn't an issue, but damping factor can be , posted on October 25, 2016 at 09:15:59
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 A single ended triode amplifier without global feedback will have a damping factor much lower than 20, more like 3, and if it's connected to a speaker with a widely varying impedance curve (say a three way bass reflex speaker with a complex crossover), there will be noticibly variations in frequency response of the system. It's not a show stopper, but it makes matching speakers all the more critical. My amplifiers have damping factors of about 4-5, and it definitely impacts the frequency response with some speakers.

 

RE: Bass control with low powered tube amps, posted on October 25, 2016 at 09:25:12
6bq5
Audiophile

Posts: 4385
Location: SF Bay
Joined: August 16, 2001
 The salient point is more that controlling the bass is a function of damping factor over power-
In a tube amp this boils down to use of feedback and the transformer - or in an OTL- the feedback and circuit-

the higher the damping factor the better the bass response-
I had a friend - whose system is big thiels - before the sale- and Krell, and I have ProAc R3s w/ Music Reference RM-9 - he felt that I had more bass....
RM-9 damping factor is ~10...
Happy Listening

 

RE: Bass control with low powered tube amps, posted on October 25, 2016 at 13:05:52
SETguy
Audiophile

Posts: 35
Joined: July 4, 2015
 I've never found Klipsch speakers, whether from the Heritage Series or Reference Series, to be overly sensitive to amplifier output impedance. In fact, in the horn-loaded units such as the LaScalas, Khorns, etc., it seems to make no audible difference at all. An interesting take on df was given by George Augspurger of JBL fame back in '67. It's a worthwhile read as is a follow-up to his paper by John Murphy in part 2. As to speaker impedance variations over the audio spectrum affecting amps, triodes with a very low plate resistance are really quite immune.

 

Stuffing, posted on October 25, 2016 at 13:32:07
Duke
Dealer

Posts: 4429
Location: Princeton, Texas
Joined: March 31, 2000
 Regardless of how powerful the woofer's magnet is, its effective electrical Q is modified by the amplifier's output impedance. This effect is the sum total of damping factor's influence on the bass region, and it is easy to model: A 4-ohm output impedance will raise the electrical Q of a nominal 8-ohm woofer, assuming a 6-ohm voice coil resistance, by a factor (6+4)/6 = 1.67. This is true no matter how powerful the woofer's magnet is.

If we started out with a 16-ohm woofer (voice coil resistance of 12 ohms), then an amp with an output impedance of 4 ohms would raise the electrical Q by a factor of (12+4)/12 = 1.33, or half as much.

I design speakers to work well with a wide range of amplifier damping factors, from solid state to the Atma-Sphere S-30 OTL tube amp (which has a lower damping factor than most SET amps). The approach I use is to keep the impedance curve fairly high and as smooth as is reasonably feasible, and typically use multiple pluggable ports to adjust the box tuning. In practice, I can get about 1/3 octave deeper extension with a low-damping-factor tube amp, once the port tuning is adjusted.

The Klipsch Forte uses a passive radiator, as I recall, so you could theoretically add mass to it to lower the tuning frequency.

But before doing that, try adding a pound or so of well-fluffed Polyfill inside the enclosure. This will reduce the magnitude of the upper bass impedance peak, which is the one that makes the most difference in the bass region. You could theoretically get a 1.5 dB ballpark reduction in output at that frequency, which would be beneficial if that speaker/amp/room combination is giving you bass boom.

(If the Forte's impedance curve has significant peaks and dips elsewhere in the spectrum, those can cause changes in the frequency response that are harder to address.)

Of course changing speaker and/or listener locations to reduce boundary reinforcement can help too, but heavily stuffing the box is a trick that might be worth having up your sleeve.

Duke



Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.

 

RE: Bass control with low powered tube amps, posted on October 26, 2016 at 10:59:27
bare
Audiophile

Posts: 1879
Joined: April 14, 2009
 Speakers often need a reasonable instantaneous Current capability for IMO worthwhile Dynamics especially so with 12" and bigger drivers.
Tube types are erm.. lacking in this ... period.
Whether this is an issue of concern is entirely up to the listener /owner.. as always.

 

RE: What was I thinking? Taking an axe to my amps right now and..., posted on October 26, 2016 at 20:42:59
kitch29
 ...electrodes to my brain to rid myself of the 60 years of hearing orchestras and choirs from the perspective of the low brass section.



 

TRY! replacing them 'experimentally' :-), posted on October 28, 2016 at 10:35:21
bare
Audiophile

Posts: 1879
Joined: April 14, 2009
 Some notions are deep and difficult to displace.
I Did .. haven't looked back. Sound of Tubes is the Output transformers. Like it or not.
Should be no issue selling your glow tubes.
Lotsa takers .. still.
Some Amp designs insert the transformers at the inputs Sound of Tubes and the Current of SS.
Many ways to the same ends .. Just that some work better than others

 

Some notions are deep and difficult to displace" I can see that..., posted on October 29, 2016 at 00:15:45
Cleantimestream
Audiophile

Posts: 7550
Location: Kentucky
Joined: June 30, 2005
 Having owned Extremely expensive SS... From Conrad Johnson to Krell to Bedini~~~> {the only SS I still own} ... tube equipment retain whatever recording venue included in the 'recording' ... call it ambience... in a superior manner along with higher resolution. Speakers? Quads, Khorns, Altec, Infinity, Proac, B&W, KEF, Magnepan, and of course my own designs.

I build my own tube amps and I have not heard better...


yet.


The Mind has No Firewall~ U.S. Army War College.

 

RE: Bedini and Acoustat, my last store boughts , posted on October 29, 2016 at 05:23:35
kitch29
 Then I heard horns, tubes and Marilyn, the Oboe player 2 rows in front and I was hooked.

 

Enter the self-powered subwoofer....it can work, *, posted on October 30, 2016 at 12:16:11
Billy Wonka
Audiophile

Posts: 3761
Joined: April 25, 2013
Contributor
  Since: October 15, 2013
 .

 

RE: Bass control with low powered tube amps, posted on November 2, 2016 at 12:47:36
Jim D.
Audiophile

Posts: 854
Location: FL
Joined: October 26, 2000
 I have to come the same conclusion except I do use a 2A3 amp to drive my mid bass horn. My tapped horns OTOH which work from 65 hz and down are driven by a 700 watt Crest pro amp!

Jim

 

RE: Bass control with low powered tube amps, posted on November 3, 2016 at 21:15:24
tube wrangler
Manufacturer

Posts: 2484
Location: USA
Joined: January 29, 2007
 Control of the woofer cone requires three things:

(1) SPEED and timing accuracy (no time-delays) of CURRENT delivery.

(2) QUALITY of the amplifier's power supply.

(3) Quality, wire size and lengths of speaker cables.

Notice that I didn't mention whether Solid-State or tube, whether SET or P/P, or what watt rating.

ON TIME power delivery at the voice coil is what delivers stellar woofer control.

---Dennis---

 

RE: Bass control with low powered tube amps, posted on November 8, 2016 at 16:59:04
krankkall
Audiophile

Posts: 296
Location: New Mexico
Joined: April 5, 2014
 A low powered tube amp with solid state rectification, will 'tighten up' the bass better than tube rectification.

Steve

 

RE: Bass control with low powered tube amps, posted on November 17, 2016 at 01:02:54
KanedaK
Audiophile

Posts: 2519
Location: Brussels
Joined: April 27, 2010
 I have LaScala derived 3 way speakers with klipsch k33 woofers loaded by Peavey FH1 bass horns. I used to drive them fullrange with a Trends TA10.1 amplifier and bass was very ok. But since then i bought an active crossover and a second chip amp. The base amp is 25watts/8 ohms (3 times more than the Trends) and is directly connected to the woofer, so i was expecting better bass but I´m getting just the opposite! It's like the woofers are unabke to move, there's no impact, no "slam ". Had the same problem with a 120watts Technics SE-A5: too much damping factor! I would say for my speakers a damping factor between 20 and 50 is optimal...

 

F'whoop, the article is about damping factor., posted on November 24, 2016 at 00:56:10
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
 :-)!


Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

Page processed in 0.086 seconds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]