"Loud Enough to fill a Small Hall"

[Herald1360]

The best disco around when I was a student in the '70s was one run by a guy who used a couple of 30W KT66 amps into homebrewed horn loaded speakers and ran either 301s or 401s (can't remember which) as decks. Compared to the headache inducing transistor / SP25 setups all the others used it was just a VERY loud HiFi.

[ms660]

First amp we used when doing the WI huts and church halls back in the day was a homebrew 30 watt job, more than ample for all the halls we did.

Filling the hall with sound was no problem, it's filling the floor that was the trick....lads on one side...ladies on the other...no one on the floor...solution =:

https://www.youtube.com/watch?v=R-Tfm70dL5s

Never failed.

Lawrence.

[emeritus]

Re #17. I believe that, in the 1960's, the Odeon , Leicester Square used a 15W PA, evidently driving highly efficient speakers. I guess that, in the days when optical sound tracks were the norm, an extended frequency range was not needed.

[Nuvistor]

Poor cinema sound systems mean I don’t go, it gives me a head and earache. Too loud, too much of the very low frequencies.
Not really a problem for me as the films produced today are not to my taste.

[barrymagrec]

My HMV model 3030 tape machine has a 2 watt N78 amplifier driving a 13 x 8 speaker - it can be astonishingly loud when turned up, much more than is required for a medium size living room.

[TonyDuell]

I remember seeing somewhere that the Mullard 5-20 (20 Watt output using a pair of EL34s) was 'adequate for a small cathedral'. To which a friend of mine replied 'Alas my living room doesn't have the acoustics of a small cathedral'

['LIVEWIRE?']

I am by no means a loudspeaker design expert, nor a HiFi Fanatic, but, with all this talk of older loudspeakers being more efficient than modern ones, is it not possible to design and produce really efficient speakers, which have the wide frequency range to merit the term 'HiFi', but which can also fill a room with sound when driven by, e.g., a 10 watt amplifier?

[barrymagrec]

Yes, many modern speakers are quite efficient but also large - if you want a small speaker to sound good they tend to be inefficient and most people these days want compact speakers and also high power amplifiers are cheap.

[GrimJosef]

Sadly not (if it was then loudspeaker manufacturers would have done it).

Strictly speaking the trade-off is a three-way one between efficiency, bass extension and physical size. Using horn technology adds a further option, with an increase in efficiency at the expense of a narrower frequency range and, in the bass, again large physical size.

The main issue though is that there is no 'driver' to do this. Power these days is dirt cheap and the amps are low-distortion, compact and reliable. So folks choose to have the sound they want from a reasonably sized box and just accept that it'll involve investing in some silicon.

Cheers,

GJ

[emeritus]

In the 1970's one of my more affluent friends bought a pair of Lowther speakers. Massive things, but really efficient, deafening sound from the external speaker socket of a battery cassette recorder with the volume on less less than a quarter turn.

[Andrew2]

Originally Posted by MurphyNut

What people considered loud in the 1950's would be deemed quite modest now.
Saying that I'm often appalled at the over-loud and poor quality sound coming from systems used at functions these days.
Despite all this power and technology they often sound horrible and you go home with a headache......Bring back the 1950's Dansette!

Indeed. I find that modern DJ's go for the 'boom and tizz' sound. Loads of thumping bass and a top end so boosted that it sounds like steam escaping from a leak. It hurts my ears.
Back when I were a lad (early 70's) we ran a mobile disco with all home-made gear. A pair of Sinclair Z50's (there's bravery for you, but at least they were separate channels so could run independently should there be a fire) and two SP25 Mk 3's plus a tape player. The combined 70 watts was plenty loud enough with the two speaker cabs each consisting of two 12" drivers and a single piezo HF unit.
Things were not quite so good when we were persuaded to do an outdoor gig at a cricket club. Those 70 watts disappeared into the night and we had to mic our system up through the groups PA. Happy days!

[regentone001]

At school the two dining rooms in each house block were separated by a removable screen for morning assembly. The screen was removed so the two houses had combined assembly. We had a Dansette Tempo, not exactly the most powerful of machines, but it would fill those combined rooms with sound even when all us kids were in there. In fact I got a glaring look from my house mistress for turning it up when I was egged on by the rest of my form (I was in charge of the house electronics gear).
Steve

[paulsherwin]

Originally Posted by 'LIVEWIRE?'

I'm inclined to agree with you, Clive. Maybe a little more power and fidelity that some of the fifties kit could provide is desirable, but hundreds of watts is, IMHO, ridiculous, even in a large hall, never mind in home or car stereos.

The main factor determining power requirements isn't the size of the 'small hall', it's what's going on inside it. A record player with a 3W single ended amp is easily loud enough to fill a hall containing a few dozen people sitting quietly. The same space full of a few hundred drunk people shouting at each other will need 10, maybe 100 times that power.

Modern cinema systems use kilowatts of power because they reproduce lots of low frequency effects. You certainly don't need hundreds of watts for ordinary dialogue.

[McMurdo]

One day in the 1970's our school hall caught fire, and when the Christmas party came, we had to have it up the road in the Weston Inn, as they had a large dance floor.
The music for the fun and games was a dansette perched on a bar stool. It was soon drowned out by 150 screaming juniors and Pass the Parcel, Musical Chairs and the Hokey Cokey had to be abandoned. A far cry from the Grampian we'd always used.

[MurphyNut]

Originally Posted by Andrew2

I find that modern DJ's go for the 'boom and tizz' sound. Loads of thumping bass and a top end so boosted that it sounds like steam escaping from a leak. It hurts my ears.

I often feel the quality of the speaker enclosures are largely to blame for poor sound, pumping large amounts of bass into them shows them up, the louder they are energised the more that unpleasant colouration takes over.

[GrimJosef]

Originally Posted by GrimJosef

... Using horn technology adds a further option, with an increase in efficiency at the expense of a narrower frequency range and, in the bass, again large physical size ...

By coincidence a friend is spending this weekend helping another friend to install some horns at home. The attached picture shows the work nearing completion. The boxes at the bottom with grey grilles house two 12" drivers each. These handle the deep bass in quasi 'open baffle' configuration (which is very inefficient indeed in the deep bass). The low- and mid-range frequencies come out of the two large black horns. The treble is dealt with using the horn-loaded tweeters which hang in the throats of the mid-range units. Each driver has its own amplifier and a digital signal processing package feeds each amplifier with the appropriate frequencies.

I'm not sure whether the sound is big enough to fill a small hall, but the speakers themselves more-or-less are. It's generally reckoned that such systems suffer from low WAF*. But you'll be pleased to know that the sound is "glorious".

Cheers,

GJ

*Wife Acceptance Factor, of course

[Vintage Engr]

Originally Posted by Herald1360

Real watts are not watts RMS, though they are volts (rms) * amps (rms) which gives the average power if the load is resistive.

Watts RMS was just another term coined to try to get round all the various claims about power output from "hifi" amps in the early transistor period.

See here: https://vintage-radio.net/forum/showthread.php?t=7054

(And many other threads in a similar vein).

I do realise that, perhaps what I should have said is, 'compared to watts PMPO', which what is often quoted on modern cheap audio units. I once had a pair of 'Computer speakers', i.e, (in case one wishes to be picky,- connected to a PC, not that the actual LS has anything to do with computing!)
These speaker/ amplifiers were supposedly 60W PMPO , & were powered via the mains from an internal PSU. The PSU's mains transformer was about a 45mm cube. Total current draw at 240v was around 25mA.

Amazing how one can apparently get something for nothing! They didn't sound that loud....

[Valvepower]

Hello,

This is from the Leak TL50 information sheet “For public address work the power output permits its use in the largest auditorium. Out-doors, it will cover crowds dispersed over a 10-acre field when using horn loudspeakers”

I can remember the TL50 with a simple mixer/preamplifier of some sort being used by gigging groups even up to the mid 70’s to drive the vocal PA system. One of my TL50’s is believed to have been used in a Reggae/Blues club sound system in the dim and distant past.

I used a 50 watt Sound City mixer amp with 2x12” speaker cabinet for my disco system in the mid 70’s – this was plenty loud enough for School, PTA and social club discos – good days.

From memory 100 watt was a typical power for mobile disco and also local gigging group vocal PA use in the 70’s – I suppose this power went up post Saturday Night Fever with the influence of big club systems and with the emergence of the Rave culture. But there is limit as to haw far one can go as the equipment had to fit it in the back of an average family estate car or similar sized van!

Orange/Matamp made a 200 watt 4x KT88 amplifier with massive partridge transformers and these were LOUD and were also rugged...!!

Finally, I remember and old timer using for his disco system a Mullard 5-20 amplifier driving a folder horn cabinet fitted with a 15” speaker and Fane cellular horn. This chap worked at the factory in Rayleigh, Essex that made the Orange folded horn speaker cabinets and he made a sneaky “copy” cabinet during his lunch breaks for his own use!

One last thing, I remember a Fairground ride owner coming into the Roost amplifier workshop around 1975-76 and we made him 100 valve amp head with modified inputs to take a turntable.

Terry

[dave walsh]

Going from "fake" and real watts to the psychology of listening, there is such an emphasis on "Deep Bass" during live performance, Cinema viewing, In-Car and High Fidelity systems now [half a century later] that it is hard for anyone, not there at the time, to grasp the excitement and effect created by very low powered set ups. Most Portable Record Players/Radios or TV's could fill a room with 2 or 3 watts. The sound quality was there but not demanded [or available, even on stage] at tremendous output at that point. It was great to hear the Beatles at high volume in the cinema [but drowned out]. They'd previously sounded just as exciting at at very low volumes relative to today.

I recall hearing the organ parts on Mr Moonlight [Beatles For Sale] emphasised on a friends parents new Radiogram. I thought the bass sound amazing but didn't go home wishing I had a really loud system at home. Perceptions have changed. Not always for the best. I spent 3 days at a Festival in August. Most of the time I wasn't near a stage as I could hear it [as per the front row] from some distance away, relaxing in the hot sun with a drink! Even though bands like the Hendrix Experience progressed from the AC30 amp to Marshall stacks, most local bands in the sixties produced an equally thrilling sound by overloading, maybe sometimes, only one small amp between them and it worked. The same restraint ciple applied at home. It's not just the equipment that has changed.


Dave W

PS. Those horns look amazing GJ but I'm guessing [by definition] they need very little input to produce a lot of sound.

[broadgage]

I recall an early home built germanium transistor amplifier built by a school friend.
This was impressively loud for a medium size hall. We had no way to measure the audio output but by measuring the DC input and assuming an efficiency of about 50%, the audio was about 15 watts.
Input was just over an amp at 24 volts from a series pair of car batteries, or about half an amp from 15 or 16 series connected dry cells.
5 of the 4.5 volt "door bell" dry batteries in series were often used, suggesting an audio output of about 5 watts in dry battery mode.