Speakers question ...

[Opsimath]

... because I know nothing about speakers and amps and stuff, but I'm willing to learn.

My friend down the road has electronic equipment from his roommate, a sound engineer and local radio personality, who passed a few years ago. There is enough to do professional grade recordings and broadcast a radio station, which he did for some years. In this extensive collection of boards, mixers, and vintage microphones is a pair of speakers that used to be in a movie theatre. Unfortunately an amplifier or something went out and my friend can't use the speakers, which he says at full tilt will blow the windows out.

My question is, do speakers that size need an amp of some minimal amount of power to make them work; does the amp need a specific amount of power to be able to push the speakers?

 

[Midnight Toker]

There are many factors that can come into play w/ commercial grade speakers (like for a theater) Many are set up for bi-amp setup.(which requires more than one amp, as one will drive the low end and another the high end) then there’s ohm rating. 8 ohms is a general standard, but high end gear can often differ from that. But…as far as power (wattage) ratings. If a speaker says “max input 500 watts”, you can drive them w/ just about any amp from 35 to 500 watts. You just never want your amp’s output power rating to exceed the max power rating of the speakers.

Try and get a picture of the info plate and input jacks on the back of the speaker, and we can go from there.

 

[Opsimath]

Thank you!

 

[davidbeinct]

Did the amplifier in the speaker go, or did a separate amplifier go? The first would require opening up the speaker and fixing the amplifier, the other would just require getting an amp.

 

[matsickma]

Not sure of the speaker type, model or size but if you look at the way speakers and cabs were designed years ago power was very expensive per Watt so the cabinets were designed to improve the efficiency of the speaker so that low power was still pretty loud and had a strong low end. If you Google vintage Altec Lansing, JBL and Klipsch you will find modest size speakers with large cabinets. Many different techniques were used. The default vintage was the Altec Lansing Voice-of-the-Theater. These have a 5' tall cab for low and low mid frequencies. Typically a crossover freq of 500 Hz or 800 Hz. I would describe them as a sub woofer type only because of compromise. Above the crossover frequency you typically had a metal horn "tweater" of various types. In some high end systems the horn covers frequencies up to about 6000 Hz to 8000 Hz and then a high end horn tweeter for the sizzlers.
Once you see a few of these systems things can get very elaborate like the JBL Paragon or Hartsfield. The Klipsch low end cab may have been the first to design a long folded horn inside the cab such that the length was able augment the rear speakers sound to radiate in phase with the forward facing low end speaker so as to amplify those lower frequencies.

If you have spent a lot of time in bands or listening to live music you may find you like the way theater designed speakers sound. It mimics much of the live performance sound tone and intensity. If you tended to listen to music with smaller "Hi Fi" speakers the tone and balance of theater grade speakers may be overpowering to you.

As with most things...it's a matter of personal taste. I for one wish I had a very large room with high ceilings to emulate the live music sound. Unfortunately the other in the house may not appreciate it. And I didn't even consider the neighbors!

M

 

[Nuuska]

There's one more thing - "professional speakers" are much more sensitive - ie 95-100dB @ 1W versus 80-85dB @ 1W with home speakers.

In clear language - You'll be astonished how loud they sound w just regular home amp.

Assuming they are not bi-amped - as @Midnight Toker said earlier.

Have fun

 

[matsickma]

And if Bi-Amped you will be blown away by the volume! Adjusting a bi (or tri) amp system is really fun. You bring up the low end then the high end and then tweak a bit. It really gives you a perspective of how you hearing dynamic range and frequency response is. In Hi Fi, the receivers used to have a button that shifts the frequency response to compensate for how you ear hears different frequencies at volume. I'm sure new receivers have the function but it is probably automatic. Guys, PhD's named Fletcher and Muncy developed those compensation curves back in the 30's or '40's. They likely worked for the old school Bell Labs and needed the info for optimizing telephones.
Bottom line when you have a bi-amped system you get to appreciate the dynamics of your hearing. Also, once you have a bi-amped system you will never go back. Most people have one and may not realize. Adding a powered sub-woofer is effectively Converting a basic sound system to a bi-amped system.
M

 

[Opsimath]

Wow! I had no idea there was so much to know about speakers! I don't know if my friend is really interested in getting the speakers going again, but I know I'd sure like to hear them. I'll ask him more about them the next time we talk.

In the meantime, thank you all for the information!

 

[Soul Tramp]

You have my curiosity up! Would be interesting to see pics. Depending on how old "old" is, there could be some fun surprises.

 

[SFIV1967]

Try and get a picture of the info plate and input jacks on the back of the speaker, and we can go from there.

+1 !

Ralf

 

[Guildedagain]

My question is, do speakers that size need an amp of some minimal amount of power to make them work; does the amp need a specific amount of power to be able to push the speakers?

Amps and speakers have to some matching characteristics, not just for efficiency but for the sake of the components.

The speakers might be of interest to high end audiophiles, as well the drivers/horns/crossovers might be quite valuable.

I once bought these crazy uber rare Leslie home stereo speakers, wasn't quite sure what to do with them, so I listed them on CL and out of the blue a young guy from across the stateline offered me a rare model of 70's Gibson SG in trade from them.

Good trade.

 

[matsickma]

Wow! That's crazy. Never heard of a Leslie audio cab! I have a few in the back room for either guitar or keyboard applications. I fortunately rescued a Hammond B3 type A102 from the side of the road years ago and use them with the Hammond.
I like that idea of adding a plexiglass rear baffle to show the rotation drum in action. Organ Leslies typically have the rotating drum for lower frequency amplitude modulation type effect, aka Tremolo, and a high frequency horn that provides a Frequency Modulated Doppler shift effect where the pitch shifts up as the horn rotates towards you and shifts lower as the horn spins away from you.
Seems like using a Leslie for audio would be a bit funky. However in the old days before modern signal processing pedals it was the only option.
M

 

[Nuuska]

When I was young and eager - my mind came up with propably fantastic ANALOG Leslie-simulator - a line-level box w mono input and stereo output.

I never built it - because there was no real need for it. For those interested in building it - here's the scoop.

Naturally we start w sine-wave oscillator to control the speed - there might be two or more presets and selectable ramping speed between them. The output of the oscilator is divided in two parts - one being "straight" - the other 90 degrees shifted. These two outputs then get further divided into "direct" and inverted outputs.

The signal goes in and is also divided into two lines - each having their own tremolo and pitch control - pitch control is achieved by using short controllable delays - like SAD512 bucket brigade chip - one side goes down the other goes up - in sync. This makes for the effect of the rotating horn moving closer and further from listener by every turn.

The function of the tremolo - in sync w delay - 90 degrees shifted - is to simulate the horn pointing away from you and towards you at every turn. By adjusting the amount of tremolo and variable delay right - what could go wrong ?

EDIT - this applies for typical double-horn Leslie

EDIT # 2 - is there an oopsie ? Likely - the tremolo oscillator needs to have double frequency - since there are two horns flapping around.
For single-horn version - only one pitch control combined w stereo tremolo in sync.