Yes you can. BUT: the lowest secondary the output transformer can be configured for is 8R, so the 811s will see half the intended load impedance which means distortion will be increased and power output decreased. But it won't hurt to try.
Without changing the original output transformer? Yes, with an additional transformer between the Altec amp and your speakers.
How technically versed are you? Are you a subjective music guy, or do you care about minimizing distortion? Power output shouldn't be an issue with an amplifier like that.
How technically versed are you? Are you a subjective music guy, or do you care about minimizing distortion? Power output shouldn't be an issue with an amplifier like that.
I'm no technician. But I care seriously about distortion. If hooking up the U15s degrades sound quality I will not do it. I've just done a search for a pair of Speltz Zeros with no luck. Any suggestions?
First: hook your U15s up to the Altecs' 8R tap. Listen to that. How bad is it? Do feel sound quality seems degraded?
If you were a tech guy as most on diyaudio I'd say measure the amp into 4R and 16R and post what you get.
With a 1:2 transformer the Altecs will see a 16R speaker. As no airgap is needed on the impedance matching transformer you could try a toroidal 120V transformer with a 60V secondary. Buy from a place that accepts returns and give them back if you don't like what they do. Or contact Dave Slagle at Intact Audio for a matching autoformer.
Maybe someone else has a different idea?
If you were a tech guy as most on diyaudio I'd say measure the amp into 4R and 16R and post what you get.
With a 1:2 transformer the Altecs will see a 16R speaker. As no airgap is needed on the impedance matching transformer you could try a toroidal 120V transformer with a 60V secondary. Buy from a place that accepts returns and give them back if you don't like what they do. Or contact Dave Slagle at Intact Audio for a matching autoformer.
Maybe someone else has a different idea?
An autoformer would only have three leads. The link seems to be for 115v 50/60hz. Is it really made for audio? Always a chance the link if not working right for me. If it is then I would probably be happier with an autoformer rather than an impedance mismatch.
Other option would be to choose something like the U15 but with proper impedance.
Other option would be to choose something like the U15 but with proper impedance.
You could try wiring a power toroid as an auto transformer. A 120v:60-0-60 would do it. Wire the primary (if 120/240, use both in parallel) and the two 60V secondaries in all in series. Take the 4 ohm tap off the 75% point between the two 60V windings. That’s close enough to the 70.7% point. It will be able to tolerate at least 240V RMS input at 50Hz, or 120V RMS at 25 Hz without distorting. High frequency performance of power toroids is usually pretty good.
Have in mind that there is a 50% chance that primary and secondary may be connected in opposite polarity and cancel each other.
They are not marked, so you can't know.
This will produce strange effects, very low output, distortion, no bass etc.
If that happens, you have to reverse connect either the secondary or the primary.
Not both ...
They are not marked, so you can't know.
This will produce strange effects, very low output, distortion, no bass etc.
If that happens, you have to reverse connect either the secondary or the primary.
Not both ...
As shown in post # 12.
4R symbolises your 4 ohm speaker.
The two other terminals on the right go to the 8 ohm terminals on your amp.
4R symbolises your 4 ohm speaker.
The two other terminals on the right go to the 8 ohm terminals on your amp.
I have to ask what is your intended purpose for the amplifier/speaker? Is it outdoor PA, indoor home use in a larger room?
Are you doing stereo or mono? Just looking at what SPL power needs exist.
Just wondering if there is a better choice of speaker.
I have had lots of hands on experience with the Altec 1570. I rebuilt quite a few that may still be in use. I also ran an amp with push-pull 811as back in my college days.
I love the 1570 when you need lots of clean power. It does not really have the same tube sound as some lower power push-pull. Mine was accused of being closer to a better behaved mosfet amp.
Are you doing stereo or mono? Just looking at what SPL power needs exist.
Just wondering if there is a better choice of speaker.
I have had lots of hands on experience with the Altec 1570. I rebuilt quite a few that may still be in use. I also ran an amp with push-pull 811as back in my college days.
I love the 1570 when you need lots of clean power. It does not really have the same tube sound as some lower power push-pull. Mine was accused of being closer to a better behaved mosfet amp.
I happen to have this gear on hand and just want to try them out. I have not heard any synergy horns and the Yorkvilles are well regarded as are the Altecs which I have also not heard as yet. They are bone stock except that the bass limiters have been removed. So I'm guessing 30 watts of good distortion free bottom end? I will set them up in my living room in stereo. The room is approx 17X22. Do you have any suggestions in terms of simple mods on the Altecs to enhance their performance for this purpose? I will use a pair of Linn 5150 subs with them.
Frequency response will not be a problem with a toroid power transformer, but winding resistance (maybe several ohms) probably will be, depending on size. An E-I transformer as suggested will likely limit the high end.
The 1570b will probably get 80 watts at 35 hz. Up to 165 watts at higher frequencies, It was not built really do low frequencies.
You should expect full power if crossing over at 80 hz.
There may be enough filament hum to be a problem with 98db efficient speakers though.
I can say I have had the most perfect slamming bass with a subwoofer crossed over at 65 hz and the 1570 driving a good 8 inch woofer and dome drivers.
If you were pushing for a higher performing system I think I would get speakers that will not want an autoformer.
You can try them out and see how they sound as is.
Do you have the instruction manual for the amps?
Are you using them with input transformers or directly driving?
You should expect full power if crossing over at 80 hz.
There may be enough filament hum to be a problem with 98db efficient speakers though.
I can say I have had the most perfect slamming bass with a subwoofer crossed over at 65 hz and the 1570 driving a good 8 inch woofer and dome drivers.
If you were pushing for a higher performing system I think I would get speakers that will not want an autoformer.
You can try them out and see how they sound as is.
Do you have the instruction manual for the amps?
Are you using them with input transformers or directly driving?
The manual is on line. Input transformers? I was going to drive them full range and just blend in the 5150s where needed. If there is a hum issue, is there a way to quiet it down?