High impedance loudspeakers.

[southall-1998]

Just out of curiosity, any particular ''British'' loudspeakers that have high impedance?

[Oldpinkman]

The LS35a is the obvious one springs to mind - the 15ohm version always being cited as the "real deal" for that speaker

[southall-1998]

Those 15 ohm LS3/5a's have a huge cult following over in HK!!

[Martyn Miles]

The LS35a is the obvious one springs to mind - the 15ohm version always being cited as the "real deal" for that speaker

I am intrigued by the 'real deal' as applied to the LS3/5a. I don't think Sterling Broadcast would agree...

[Beobloke]

How high did you want? One version of the Philips 9710 "full range" drive unit was 800 Ohm, IIRC!

[realysm42]

This has always confused me.

If a speaker has a higher impedance, then it's considered harder to drive right? so 16ohms is harder to drive than say, 4.

So why do people talk about amps struggling to drive 1ohm loads, or 3rd of an ohm load?

[Macca]

An amp rated at 50 watts into 8 ohms will in theory put 100 watts into 4 ohm and 200 into 2 ohm. Except that most amps have crappy power supplies that will not supply enough current double up like that so the lower the impedence the more stress placed on the amp and you get sonic effects like no bass, muddy bass, hard treble, dull treble and so forth. So a 16 ohm load will give amps with poor power regulation an easy time but will also limit overall volume i.e the 16 ohm loudspeaker will be less efficient than the 4 ohm one.

[realysm42]

Thanks Martin, that makes a lot of sense.

[Macca]

You've got no worries with that monster Sanders thing you are using anyway :)

[Arkless Electronics]

How high did you want? One version of the Philips 9710 "full range" drive unit was 800 Ohm, IIRC!

You beat me to it Adam! I believe it was designed for use with an output-transformerless valve amp that Philips also produced...

[Beobloke]

This has always confused me.

If a speaker has a higher impedance, then it's considered harder to drive right? so 16ohms is harder to drive than say, 4.

So why do people talk about amps struggling to drive 1ohm loads, or 3rd of an ohm load?

Other way round. It's all down to Ohm's law: If an amplifier is designed to deliver 100W into 8 Ohms (let's assume purely resistive for ease!) then it will need to develop 28.3 Volts (the square root of 100*8) and a current of 3.5A will flow through its output stages and the speaker (28.3/8).

Now change that 8 ohm loudspeaker for a 4 Ohm one. Now, to develop 100W into the 4 Ohm loudspeaker the amplifer will need to push out 20V (the square root of 100*4) but this will cause a current of 5A to flow (20/4)

Consequently the 4 Ohm loudspeaker actually requires less voltage but nearly 1.5 times as much current and it is current that causes things to get hot and bothered! As Macca says, this is made worse if the amplifier's PSU isn't up to the job and add in the fact that no loudspeaker ever made has ever been a nice, easy resistive load and it's a wonder they manage to make any noise at all...

[anthonyTD]

The original Leak Sandwich were 15 ohm too, i still have a pair kicking around...:)
A...

[Reffc]

The original Leak Sandwich were 15 ohm too, i still have a pair kicking around...:)
A...

Cracking loudspeakers too!

[loo]

You beat me to it Adam! I believe it was designed for use with an output-transformerless valve amp that Philips also produced...

Ah my grandad had a Philips radiogram with an otl and 800 ohm speakers , I loved that thing ,
Paul

[anthonyTD]

I still have a large philips stereo radio in the attic that had the capacitor based output stage, with the high impedance speakers etc...
This thread is starting to remind me that i have way too much old stuff...:)
A...
Ah my grandad had a Philips radiogram with an otl and 800 ohm speakers , I loved that thing ,
Paul

[loo]

Get it out , I bet it's got a luverly tone:)
Paul

[anthonyTD]

I have been meaning to for a while, trouble is, i don't really have space for it to be in use everyday...
which is a shame as its a great old thing.
A...
Get it out , I bet it's got a luverly tone:)
Paul

[loo]

I have been meaning to for a while, trouble is, i don't really have space for it to be in use everyday...
which is a shame as its a great old thing.
A...

Sadly I too have some great old stuff that never see's daylight wish I wasn't so attached to it all, so does the wife:)
Paul

[Barry]

Back in the sixties when valve amps were common, most speakers were 15 Ohm impedance. Speaker impedances were reduced to 4 - 8 Ohm when solid-state power amps were introduced, as transistors are low impedance, current driven devices.

Stentorian speakers had a series of tappings on the voice coil, permitting a choice of 4, 8, 16 Ohm operation.

[anthonyTD]

I know how you feel...:)
A...
Sadly I too have some great old stuff that never see's daylight wish I wasn't so attached to it all, so does the wife:)
Paul

[Marco]

Aye, Becky's rather attached to an 'old thing' too, eh? :eyebrows:

My previous 15" Tannoy Monitor Reds were 15ohms... In terms of the mid and top end, they were utterly sensational; in that respect probably the best I've ever heard. However, rather strangely for such large speakers, they lacked 'heft' and had little in the way of low bass - and as oi loikes me bass, they had to go!

They were replaced with 15" Monitor Golds (used in the same Lockwood Major cabinets), which are 8ohms, and so match the 6ohms taps on my Copper amp rather better, giving me the 'physicality' and visceral 'grunt' that I lurve!! :hairmetal: :hairmetal:

Marco.

[Firebottle]

You hooligan :hairmetal:

Sounds like you really want your speakers to have this much grunt :dynamite:
Would love to hear your setup some time :D

Alan

[Marco]

Lol... 'Tis true, I'm just an uncouth ruffian! :D

You'd be welcome anytime to pop over for a listen-ette :cool:

Marco.

[anthonyTD]

Aye, Becky's rather attached to an 'old thing' too, eh? :eyebrows:
It would seem so :eek::)
A...