"Loud Enough to fill a Small Hall" - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

Argus25 · 21st Oct 2019, 7:16 am

One of my transistor radio projects I decided to "beef up" the output stage to 4W.

I used 2 OC16's in push pull with an AC188 driver and a vintage Foster 10F3 speaker, that you can see on page 2, its a 3W speaker but it handles 4W.

Despite the lowly 4W this radio can appear to blast you out of a normal sized living room, and even outdoors it seems amazingly loud. It is very surprising what 4W can do with a good speaker:

http://worldphaco.com/uploads/THE_AF...OC16_RADIO.pdf

unitaudio · 21st Oct 2019, 9:11 pm

I occasionally use a Ferguson 205STA stereo receiver from 1967. I think it's rated at 10 watts per channel and goes plenty loud enough in a domestic environment. Bass goes nice and deep and it sounds satisfyingly "right" with high quality speakers of similar vintage although it's gutsy enough to drive modern speakers without getting out of its depth.

I have more modern amps at my disposal (newest is a 1997 Sherwood receiver) but I never need to play them any louder than the Ferguson and their power capabilities are never even slightly stretched. Even under these conditions things can get uncomfortably loud!

I used to have an Akai amp with peak power meters and I rarely got it over 5 watts without getting grief from the neighbours.

The selection of speakers I use tend to be inefficient hifi speakers (although that may be a bit unfair on some of the older ones) yet I still maintain huge amounts of power aren't really necessary unless you want to play at Glastonbury!

Regards,
Paul

G6Tanuki · 21st Oct 2019, 9:37 pm

Small amplifiers into decent speakers can sound good - in my student-days I would drive from Mid Wales down to a backstreet warehouse in London and return with Teleton SAQ-206B amplifiers/unbranded MDF-cased speakers, Garrard SP25MkIV record-decks etc - then sell them on to other students at a decent profit.

The little Teleton amps only did 7 or 8 watts/channel but in a typical student-bedroom and feeding efficient speakers they sounded good when playing The Police, the Stones, or Floyd/Kraftwerk/Tangerine Dream.

Beobloke · 22nd Oct 2019, 1:00 pm

This thread is worrying me. Does it mean the active hi-fi loudspeakers that I use in my lounge are slightly overkill, given the power amplification inside them totals 8200W?

Per speaker...

GrimJosef · 22nd Oct 2019, 1:09 pm

Transiently, I assume, or are they each fitted with a 32A mains plug

?

Cheers,

GJ

OscarFoxtrot · 22nd Oct 2019, 10:49 pm

Quote:

Originally Posted by wd40addict

Regarding record players I was once given the job at my primary school of playing records for the end of term 'disco'. It was the middle seventies, but the equipment was older and consisted of a solid schools type record player. It was probably a Goodsell or Comber in a wooden box which sat on a trolley with a large open baffle speaker. Was it Hi-fi? no. Was it deafening? no. Was it adequate for the job in hand? Yes.

Coombers of course were always rated in Badminton Courts

Found one still being used in a primary school a couple of years ago.

paulnd1 · 23rd Oct 2019, 12:18 am

Quote:

Originally Posted by raditechman

In the 1960's I worked at a large 1500 seats in circle and stalls cinema. The amplifier was rated at 30 watts. Although it used 4 gently run KT66's and they lasted for years! Efficient horn speakers, the fader (volume control) was never more than quarter up even with a full house.
John

That brings back happy memories. Whilst the output wattage was low by modern standards, the height of the amp cabinet we had was around 6ft with a full height door on the front. You can just about see the top of it beyond the furthest no1 mech. Controlled by mechanically linked stud faders by each 35mm projector. Not that you ever needed to turn them up far.

The valves could also be handy for straightening creased film, provided of course it wasn't nitrate stock, which was still around in the 60s especially if you were running a BFI archive copy.

Happy days.

Ted Kendall · 23rd Oct 2019, 7:28 am

Quote:

Originally Posted by Beobloke

This thread is worrying me. Does it mean the active hi-fi loudspeakers that I use in my lounge are slightly overkill, given the power amplification inside them totals 8200W?

Per speaker...

Pardon?

Herald1360 · 23rd Oct 2019, 11:28 am

If the system will run via a 3A mains fuse, it can't be capable of much more than perhaps 1kW continuous.

In reality, probably no more than a few tens of watts, maybe less.

Wasn't "IHFM peak" the ultimate in power output specmanship? ISTR that referred to what you might possibly get at the peak of a isolated single drumbeat with mains +10% and a following gale. Perhaps someone has come up with something even "better".

chaz007 · 23rd Oct 2019, 11:40 am

Quote:

Originally Posted by Beobloke

This thread is worrying me. Does it mean the active hi-fi loudspeakers that I use in my lounge are slightly overkill, given the power amplification inside them totals 8200W?

Per speaker...

It’s not though is it? ��

Refugee · 23rd Oct 2019, 12:17 pm

I have always been under the impression that the quoted power of a small HiFi is the at the leading edge of a square wave applied to the amplifier from idle with the smoothing caps fully charged.
I have seen amplifiers quoted for continuous sine wave by honest vendors in the past.

Beobloke · 23rd Oct 2019, 1:01 pm

Quote:

Originally Posted by chaz007

It’s not though is it? 🤨

Well, obviously they are not all running flat out all the time, so the likelihood of pulling 8200W from a 13A plug seems relatively slim. Especially as I suspect my ears would give in long before the speakers (or the fusebox) did! However, the fact remains that each speaker has 7 tweeters and 7 midranges that are each powered by a 300W amplifiier module (14 x 300 = 4200W).

There are then four bass drivers that are each powered by a 1000W amplifier module

4200 + 1000 + 1000 + 1000 +1000 = 8200W

GrimJosef · 23rd Oct 2019, 2:45 pm

I was wondering why a tweeter needs a 300W amplifier, but perhaps it's cheaper to use the same module for everything. 300W can be had for €70 inc VAT retail https://www.soundimports.eu/en/aa-ab31191.html and they will doubtless be a lot less bought wholesale and in large-ish quantities, so I guess price isn't an issue. As I said above, power is dirt cheap. 14 power supplies per box might set you back a bit more though.

Cheers,

GJ

m0cemdave · 23rd Oct 2019, 8:15 pm

Using the same module is going to be much easier to deal with. Not only for spares, but also the certainty that all modules have the same voltage gain, which makes setting up the (active) crossovers easier.

And it must be nice to have 20+ dB of headroom, so nothing ever clips...

Ted Kendall · 24th Oct 2019, 10:29 am

The first time I remember seeing this phrase was in an old advert for the Walter 303. Given that this was a dreadful old thing with a single EL84 and a skimpy output transformer, I can only assume it was a ubiquitous claim like "hi fi" later became...

vidjoman · 24th Oct 2019, 8:34 pm

A friend had a Walter 303 and it was LOUD. It had a larger than average speaker. Whilst lacking finesse it did make a lot of noise.

21st Oct 2019, 7:16 am	#41
Argus25 No Longer a Member Join Date: Oct 2016 Location: Maroochydore, Queensland, Australia. Posts: 2,679	Re: "Loud Enough to fill a Small Hall" One of my transistor radio projects I decided to "beef up" the output stage to 4W. I used 2 OC16's in push pull with an AC188 driver and a vintage Foster 10F3 speaker, that you can see on page 2, its a 3W speaker but it handles 4W. Despite the lowly 4W this radio can appear to blast you out of a normal sized living room, and even outdoors it seems amazingly loud. It is very surprising what 4W can do with a good speaker: http://worldphaco.com/uploads/THE_AF...OC16_RADIO.pdf

21st Oct 2019, 9:11 pm	#42
unitaudio Heptode Join Date: Sep 2013 Location: Manchester, UK. Posts: 862	Re: "Loud Enough to fill a Small Hall" I occasionally use a Ferguson 205STA stereo receiver from 1967. I think it's rated at 10 watts per channel and goes plenty loud enough in a domestic environment. Bass goes nice and deep and it sounds satisfyingly "right" with high quality speakers of similar vintage although it's gutsy enough to drive modern speakers without getting out of its depth. I have more modern amps at my disposal (newest is a 1997 Sherwood receiver) but I never need to play them any louder than the Ferguson and their power capabilities are never even slightly stretched. Even under these conditions things can get uncomfortably loud! I used to have an Akai amp with peak power meters and I rarely got it over 5 watts without getting grief from the neighbours. The selection of speakers I use tend to be inefficient hifi speakers (although that may be a bit unfair on some of the older ones) yet I still maintain huge amounts of power aren't really necessary unless you want to play at Glastonbury! Regards, Paul __________________ ...No, it's not supposed to pick up the World Service, it's not a radio!

21st Oct 2019, 9:37 pm	#43
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,995	Re: "Loud Enough to fill a Small Hall" Small amplifiers into decent speakers can sound good - in my student-days I would drive from Mid Wales down to a backstreet warehouse in London and return with Teleton SAQ-206B amplifiers/unbranded MDF-cased speakers, Garrard SP25MkIV record-decks etc - then sell them on to other students at a decent profit. The little Teleton amps only did 7 or 8 watts/channel but in a typical student-bedroom and feeding efficient speakers they sounded good when playing The Police, the Stones, or Floyd/Kraftwerk/Tangerine Dream.

22nd Oct 2019, 1:00 pm	#44
Beobloke Heptode Join Date: Oct 2007 Location: Southampton, Hampshire, UK. Posts: 821	Re: "Loud Enough to fill a Small Hall" This thread is worrying me. Does it mean the active hi-fi loudspeakers that I use in my lounge are slightly overkill, given the power amplification inside them totals 8200W? Per speaker...

22nd Oct 2019, 1:09 pm	#45
GrimJosef Dekatron Join Date: Sep 2007 Location: Oxfordshire, UK. Posts: 4,311	Re: "Loud Enough to fill a Small Hall" Transiently, I assume, or are they each fitted with a 32A mains plug ? Cheers, GJ __________________ http://www.ampregen.com

23rd Oct 2019, 11:28 am	#49
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: "Loud Enough to fill a Small Hall" If the system will run via a 3A mains fuse, it can't be capable of much more than perhaps 1kW continuous. In reality, probably no more than a few tens of watts, maybe less. Wasn't "IHFM peak" the ultimate in power output specmanship? ISTR that referred to what you might possibly get at the peak of a isolated single drumbeat with mains +10% and a following gale. Perhaps someone has come up with something even "better". __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

23rd Oct 2019, 12:17 pm	#51
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: "Loud Enough to fill a Small Hall" I have always been under the impression that the quoted power of a small HiFi is the at the leading edge of a square wave applied to the amplifier from idle with the smoothing caps fully charged. I have seen amplifiers quoted for continuous sine wave by honest vendors in the past.

23rd Oct 2019, 2:45 pm	#53
GrimJosef Dekatron Join Date: Sep 2007 Location: Oxfordshire, UK. Posts: 4,311	Re: "Loud Enough to fill a Small Hall" I was wondering why a tweeter needs a 300W amplifier, but perhaps it's cheaper to use the same module for everything. 300W can be had for €70 inc VAT retail https://www.soundimports.eu/en/aa-ab31191.html and they will doubtless be a lot less bought wholesale and in large-ish quantities, so I guess price isn't an issue. As I said above, power is dirt cheap. 14 power supplies per box might set you back a bit more though. Cheers, GJ __________________ http://www.ampregen.com

23rd Oct 2019, 8:15 pm	#54
m0cemdave Octode Join Date: Feb 2009 Location: Bletchley, Buckinghamshire, UK. Posts: 1,219	Re: "Loud Enough to fill a Small Hall" Using the same module is going to be much easier to deal with. Not only for spares, but also the certainty that all modules have the same voltage gain, which makes setting up the (active) crossovers easier. And it must be nice to have 20+ dB of headroom, so nothing ever clips...

24th Oct 2019, 10:29 am	#55
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,670	Re: "Loud Enough to fill a Small Hall" The first time I remember seeing this phrase was in an old advert for the Walter 303. Given that this was a dreadful old thing with a single EL84 and a skimpy output transformer, I can only assume it was a ubiquitous claim like "hi fi" later became...

24th Oct 2019, 8:34 pm	#56
vidjoman Dekatron Join Date: Jun 2013 Location: East Sussex, UK. Posts: 3,324	Re: "Loud Enough to fill a Small Hall" A friend had a Walter 303 and it was LOUD. It had a larger than average speaker. Whilst lacking finesse it did make a lot of noise.