Low power amplifer recommedation for Altec 511B horn

[Altec Best]

I've tried the low power diet, if i only listened later at night i could probably live with it. However, lack of power always became the culprit in listening fatigue during extended sessions. When i find a color i like, i can live with the coloration of valves(tubes). But, fatigue caused by over-driven amplifiers is just not a compromise i can live with at the end of the day. Sign me up as a solid state class A space heater fanboy.

Me too ! One watt has never been enough power for me, ever... I enjoy higher SPL's while listening to music.

[alancohen]

Ditto, though there's a certain synergy when a compression horn is driven with a ~matching output impedance, so want this as part of the system design.

I read an article by the designer of my OTL. I quote: "A good rule to follow is that amplifier output impedance must be at least ten times lower than speaker impedance for good control of cone motion. This is called damping factor. Amplifier output impedance must be less than one ohm for best performance."

Here's the full article. I'm trying to understand as much as I can. Amplifier Output Impedance

[alancohen]

Me too ! One watt has never been enough power for me, ever... I enjoy higher SPL's while listening to music.

I try to reproduce the SPLs that I would be experiencing if I was listening live.

For example, my son and I were watching (listening to) the PBS broadcast of the 25th Anniversary Concert for Les Miz. It was taped in a large arena with full orchestra and maybe 200 choral members on top of the cast. (BTW, if you haven't seen it I highly recommend you do.) I can only imagine what it must have sounded like being there.

We were sitting on the couch about 9.5' away from the Heathkits and I adjusted the volume knob to achieve a sound level of what I believe it would have sounded like sitting in the middle of the venue. With 3W/channel available form my cathode follower I got the knob to about 5 where the sound began filling our heads more than sufficiently. It was loud. I don't know how many watts I was actually pushing, but it couldn't have been much more than 1ish.

So I agree, I might be a little powered starved with a 1W amp. But 3Ws is more than enough.

Go Altec!

And BTW, we listened for almost 4 hours in one sitting and not a bit of listening fatigue. If I had the time I could have started it again.

[amandarae]

I think he's bi-amping; if so, there's no crossover between the amp and driver. I was afraid the headphone amp wouldn't drive the 8 ohms properly, but bowtie427ss pointed out that 1W probably wasn't going to get the job done with a 902.

There should be a crossover somewhere. In this case, a line level type. As for the 902 using 1W at 104dB, wonder why that is not enough especially using a line level XO which makes the full 1W is directly behind the driver.

[amandarae]

Me too ! One watt has never been enough power for me, ever... I enjoy higher SPL's while listening to music.

Is it wrong for me to think that it is not the power from the amp if 1W is an issue, to get the SPL you want, it is the sensitivity of the driver?

So to say that 1W is not enough is not entirely accurate. Are we forgetting that the probable goal of having a high sensitivity low power set up is to minimize the distortion that is directly proportional to the amount of power output of any amplifier, tube or SS? To me, if you want high SPL at low power, then change the driver. Maybe I am wrong.

Just curious.

[bowtie427ss]

wonder why that is not enough especially using a line level XO which makes the full 1W is directly behind the driver.

My comment was based on the specific system mentioned using the BMS 4550 and 1 watt solid state headphone amplifier(typically designed to driver higher impedance loads) and assumed a ~500hz XO. I think it's also safe to assume that said headphone amp driving an 8 ohm load will have little headroom to offer, i would expect it to clip easily on dynamic sources.

For my own personal preferences, the 110db sensitive BMS driver might develop satisfying dynamics for me on that particular 1 watt amp. The 902 surely will not.

Is it wrong for me to think that it is not the power from the amp if 1W is an issue, to get the SPL you want, it is the sensitivity of the driver?

Agreed, IMO&E, micro-watts need mega-speakers.

If money and space were both no object for me, i'm pretty sure i could get along on a couple good watts for most of my listening. The clincher is that my speaker system would need to be all horn loaded and large format(read massive) to achieve the necessary sensitivity particularly at low frequencies.

[Altec Best]

Is it wrong for me to think that it is not the power from the amp if 1W is an issue, to get the SPL you want, it is the sensitivity of the driver?

So to say that 1W is not enough is not entirely accurate. Are we forgetting that the probable goal of having a high sensitivity low power set up is to minimize the distortion that is directly proportional to the amount of power output of any amplifier, tube or SS? To me, if you want high SPL at low power, then change the driver. Maybe I am wrong.

Just curious.

Well I prefer the sound of my Altec drivers and a lot of the time I don't just sit there still for hours. I'll crank up the tunes and work around the house.So I will need to hear it all through the house..

[amandarae]

My comment was based on the specific system mentioned using the BMS 4550 and 1 watt solid state headphone amplifier(typically designed to driver higher impedance loads) and assumed a ~500hz XO. I think it's also safe to assume that said headphone amp driving an 8 ohm load will have little headroom to offer, i would expect it to clip easily on dynamic sources.

For my own personal preferences, the 110db sensitive BMS driver might develop satisfying dynamics for me on that particular 1 watt amp. The 902 surely will not.

Agreed, IMO&E, micro-watts need mega-speakers.

If money and space were both no object for me, i'm pretty sure i could get along on a couple good watts for most of my listening. The clincher is that my speaker system would need to be all horn loaded and large format(read massive) to achieve the necessary sensitivity particularly at low frequencies.

Yes, understood. It is cheaper to increase the power of the amp than increase the sensitivity of the drivers.

[amandarae]

Well I prefer the sound of my Altec drivers and a lot of the time I don't just sit there still for hours. I'll crank up the tunes and work around the house.So I will need to hear it all through the house..

Yes,in that case, a 1W amp will never satisfy the need especially if you have a humongous dwelling. That's why I still have a back up SS amp. When I do something inside the house, or around it, and wants great background music where loudness is the importance, I use the SS amp instead of DHT's as it is way cheaper in the long run.

[wws944]

My now-departed uncle used to talk about how, back in the late '50s, he would show off how efficient his 820 was by hooking it up to a cheapo transistor radio. When I asked him how it sounded, he said "like a *big* cheapo transistor radio".

I had the 820s hooked up to a MC2100 (105 w/ch), which I had plugged into a Kill-A-Watt meter. According to the Kill-A-Watt meter, the MC2100 draws about 40 watts at idle, and about 40 watts at 'loud'. So it barely knew the Altecs were hooked up.