SET amp owners thread

[bonzo75]

Hi what speakers/drivers are those who have SET amps (or low watt push pulls) on this forum using, in terms of multiway high efficiency speakers or OB?

Reason I ask is after going through various high efficiency threads I found many using Pro class D or SS amps, and I am looking for voicing with SETs, so will be better to understand who the users are.

Thanks

 

[AllenB]

I wouldn't let the amp dictate the speakers I build, meaning two things. Even if I didn't like high efficiency speakers (even though I do) I'd just use a transmitting triode instead. And regarding source and load impedance I account for this so it isn't impressed on the end result.

What do you mean when you say voicing for SETs, this could mean so many things?

 

[bonzo75]

I wouldn't let the amp dictate the speakers I build, meaning two things. Even if I didn't like high efficiency speakers (even though I do) I'd just use a transmitting triode instead. And regarding source and load impedance I account for this so it isn't impressed on the end result.

What do you mean when you say voicing for SETs, this could mean so many things?

The crossover and set up should be simple, efficiency and impedance matching for low watt amps to drive easilY.

It should be transparent to source and recordings

 

[piotr z]

There's no reason for "voicing for SET" - what helps is flat and high impedance and efficiency due to low wattage. Speakers should match room due to the room gain in lower registers and that's it. Best solution though seems like traditional 3way with large woofer and fairly simple crossover.

 

[waxx]

I don't own set amps for the moment, but what i mostly see when they are used, is that they use high efficient fullrange or dual concentric systems (Altec Lansing, Tannoy, EV SP12, Lowter, Fostex, ...) or a multiway setup with an active crossover and an set for mid and top and a PP tube amp or solid state amp for the bass/sub. I've used a 8w 300B set (i had it to watch it for the owner when he was abroad) with 92dB efficient full original Goodman Mezzo SL speakers, and that was enough for my living room of 8x6x2.5m.

But some SET amps (a 845 or 212 set) actually deliver enough power to power up speakers from 85dB efficiency. It all depends on the wattage, the room they are used in and what the owner want of volume.

 

[bonzo75]

Moreover I would like to visit and listen to some designs or drivers I am interested in but sonically I am interested in auditioning only if they are run by valves. It is not that I don't like SS but I prefer it if any only or bass or speakers like restored apogees, and some new commercial low impedance speakers.

Hence, just a request to know who SET owners are. Makes the search function easier and concentrated

 

[Quattrofish]

I use a 2a3 SET (3.5 watts) with Mark Audio Alpair 7.3 for 300hz and up.

Running a Crown XPS 1500 with a Mark Audio Alpair 12pw for under 300hz.

Crossover is PLL, 1st order.

Sounds great to my ears. Happy to offer an audition if you are ever in the DC area.

 

[bonzo75]

Thanks

 

[Dave R]

I have a small diy bookshelf (vented) pair that goes down to about 60-65 Hz. The crossover is series, and provides a constant easy load of about 5 ohms for my 6-8W SET amp (KT88/6550).
I use a pair of powered subs to fill in below that.

 

[Jeanper]

I have a 300B amp with about 7-9 w. I have it in a smallish room (16 kvm) and rarely play very loud, but i have found it to be sufficient for my needs with both open baffle and boxed speakers, using no more than maybe 1-2 W. It only have a 8 ohm tap and that means that it is a little impedance sensitive.

The speakers i have built are about 88-95 dB sensitivity.

I really do like open baffle sound, and 15" woofers are fun

 

[enzoastro]

I have a variety of SET amps, 833, gm70, 300b 4p1l and just built a 4 channel PSE 6e5p amp to drive my mid and highes, DH1a/940 horn formids and tpl150 highs. I built a pair of mofo MOSFET follower amps over Christmas, the TPL feels more extended, if not more real with the mofo. I was thinking of running my midbass horns with the mofo but after I tried it with my 6e5p it's staying valve powered, so much better. Might end up tube bass mid and ss treble?!

 

[system7]

There is a bit of a masterclass on building speakers for SET amps here at the forum:

Arpeggio Loudspeaker - diyAudio

I cannot emphasise enough just how good Morgan Jones is as an engineer. He has a famous track record in high fidelity.

First issue he solves is the adjustment of the Qtc on the preferred closed box with a SET amp:

After that, it's flat impedance and bafflestep.

In a multiway, impedance can be flattened with a conjugate network, here in red:

Sort of thing that might work with a speaker like this, if we lost the reflex:

I cribbed that one from the WLM La Scala...

 

[bonzo75]

I have a 300B amp with about 7-9 w. I have it in a smallish room (16 kvm) and rarely play very loud, but i have found it to be sufficient for my needs with both open baffle and boxed speakers, using no more than maybe 1-2 W. It only have a 8 ohm tap and that means that it is a little impedance sensitive.

The speakers i have built are about 88-95 dB sensitivity.

I really do like open baffle sound, and 15" woofers are fun

What drivers do you have

 

[cspieker]

I run 2 watt zen triode from 500hz up on a radian 475 {110db/w). 800 watt ss for woofers.

 

[Bill poster]

Have similar issue w 12w set. My alpairs are not suited. Looking at a variety of good budget largish drivers inc dayton RS225p. Good bass response and decent sensitivity

 

[Phenoholic Anonymus]

EL34 SE on a pair of Ciare HX 132's in a BLH. I think you need to ask about roomsize. And music styles.

 

[Brinkman]

Another consideration that allows some refinement is to use an active subwoofer. Not only is there the two-fold benefit of superior bass handling and extension, the reduced bandwidth requirements of the single ended output transformers means a smaller window and bobbin size, which translates to less losses across the transformer (increased efficiency) and reduced self-capacitance, extending the HF response. Additionally, the mains could also utilize an aperiodic type enclosure which helps reduce the mid-woofer’s low frequency impedance peak. Used with the aforementioned conjugate (Zobel) network, you’ll be presenting the OPT with a fairly flat load.

 

[Alex M]

Another consideration that allows some refinement is to use an active subwoofer. Not only is there the two-fold benefit of superior bass handling and extension, the reduced bandwidth requirements of the single ended output transformers means a smaller window and bobbin size, which translates to less losses across the transformer (increased efficiency) and reduced self-capacitance, extending the HF response. Additionally, the mains could also utilize an aperiodic type enclosure which helps reduce the mid-woofer’s low frequency impedance peak. Used with the aforementioned conjugate (Zobel) network, you’ll be presenting the OPT with a fairly flat load.

This is the way I'm going. My 300B amps are PP, not SE, but their lack of global NFB means they have a relatively high output impedance. My Troels 3WCs can sound quite glorious in the midrange and treble, but the bass from this combination doesn't have much impact or definition.

My current project uses the 300Bs for mid and treble, and Hypex plate amps for bass.

Alex

 

[Quattrofish]

This is what I've done as well, minus the Zobel.

PLLXO means the SET doesn't have to amplify below the crossover, freeing it up to work its magic on the mids and highs. I started using it with a prior WAW that already sounded pretty good, but everything improved to a surprising degree. I figured most of the improvement came from the speaker side of things, but apparently it is also beneficial to the amp.

Thanks, Brinkman, for the terms and explanation from the amplifier side. I'll look em up.

The sound improved even further with the new speakers, which do use an aperiodic enclosure.

Another consideration that allows some refinement is to use an active subwoofer. Not only is there the two-fold benefit of superior bass handling and extension, the reduced bandwidth requirements of the single ended output transformers means a smaller window and bobbin size, which translates to less losses across the transformer (increased efficiency) and reduced self-capacitance, extending the HF response. Additionally, the mains could also utilize an aperiodic type enclosure which helps reduce the mid-woofer’s low frequency impedance peak. Used with the aforementioned conjugate (Zobel) network, you’ll be presenting the OPT with a fairly flat load.

 

[enzoastro]

My 300b amps, even with decent lundahl opt have suboptimal bass, not as good as any of my other se amps. Seems to be a 300b thing.