# Phoenix PB9 Speaker help



## BodsRailRoad (Jul 26, 2008)

I'm looking for some advice on speaker choice for my new LGB F7A+B set up.

The A unit houses the PB9 board and a stock Phoenix speaker. I want dual run a second speaker for the B unit driven by the A units PB9. I know to wire them in parallel, they both are 8 ohm, and that the B unit will just eco the A units sound.

My question is while I have a second stock Phoenix speaker that will work but I also have a several Visaton FRS8 speakers. The Visaton FRS8 sounds much better in single speaker setups that I have, but can the PB9 drive both FRS8s (in parallel 2 x 8ohm speaker) and still sound great, or would that require more watts that the PB9 can handle and stick with the 2 Phoenix speakers?


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## Greg Elmassian (Jan 3, 2008)

your answer is on page 16 of the manual...

given the same amplifier, a lower impedance will "draw" more watts.

It will also increase the harmonic distortion. 

Different people hear harmonic distortion differently. To an audiofile, HD makes it sound like crap, but I have met people who cannot tell the difference.

So not sure how to give you the best answer. the best way would be to know how you perceive sound.

Greg


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## BodsRailRoad (Jul 26, 2008)

Page 16 doesn't answer my question just says 2 8 ohm speakers are fine. My question is will the PB9 be able to power 2 of the larger Visaton speakers, which are are 8 ohm and have 30 watts max, and still maintain good sound and volume, or use the 2 Phoenix 8ohm speakers which are 2 watt max?


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## Greg Elmassian (Jan 3, 2008)

The question you asked was about sound quality.

So the first thing you do is see if 4 ohms will overload the amplifier, per the manufacturer.

So it is likely that 4 ohms will not cause so much distortion that they will "make" less sound.

There is the basic answer to your question, although the harmonic distortion will be higher. (back to quality of sound)

Now your new question is about how loud. Just because a speaker is rated at 30 watts (max) does not mean it draws 30 watts. It means it has the mechanical and thermal capability to handle that much power.

What you need is the sensitivity of the speaker, which means how loud is it for a given power.

You can find this on the visiton datasheet, but you won't find squat on the stock speaker you show (looks like the standard el cheapo you show is an Aristo from a steam loco)

So, to help you, you look for a sensitivity in the high 90's... look at the data sheet... (usually spec'd in db per one watt)

If you can find an efficient/sensitive speaker, you would do well.

Greg


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## BodsRailRoad (Jul 26, 2008)

By sound I meant volume and quality combined sorry not an "audiophile" just looking for a general yes it can or no not enough power stick with the Phoenix speakers, maybe there is someone who has run dual speakers with a PB9 that could give me an opinion.

Visaton FRS8 Specs- 











This is one of the 2 actual Phoenix speakers that will be used.


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## BodsRailRoad (Jul 26, 2008)

Found this as well on the 8omh









This is for the 4 ohm.


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## piercedandan (9 mo ago)

I would use the Visiton FRS7 low profile (these come in 4 and 8 ohm versions) as it should fit in the fuel tank without cutting up the engine frame. FRS8 is so big it only fits nicely in 1/20.3 engines for me.


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## BodsRailRoad (Jul 26, 2008)

Thanks have some of those as well 👍


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## Greg Elmassian (Jan 3, 2008)

FRS-7 has sensitivity of 88 db..



https://www.parts-express.com/Visaton-FRS7-8-2.5-Full-Range-Speaker-8-Ohm-292-530?quantity=1



look under specifications... sensitivity is easy to use number.

so this is not going to be very loud, and turning it up will increase distortion.... you may not like it, but I use them:

This is one with the flange trimmed to fit nicely in an F3 tank:



















I also had printed speaker boxes to hold them:










much more detail on my site:






F3 DCC install


Greg Elmassian web site on large scale trains and garden railroads, cigars, and computers




elmassian.com





Greg


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## Bob F (Mar 18, 2021)

BodsRailRoad said:


> I'm looking for some advice on speaker choice for my new LGB F7A+B set up.
> 
> The A unit houses the PB9 board and a stock Phoenix speaker. I want dual run a second speaker for the B unit driven by the A units PB9. I know to wire them in parallel, they both are 8 ohm, and that the B unit will just eco the A units sound.
> 
> ...





BodsRailRoad said:


> Thanks have some of those as well 👍


It isn't necessarily the size of the speaker, but the electrical load, or impedance. In the photo they both appear to be 3 inch or 4 inch speakers. The major difference is in the power handling of the speaker. The Vistaton has a larger voice coil and more "beef" to dissipate heat that can build up quickly in a speaker if over driven. 

Putting the two speakers in parallel will result in a 4 ohm _dynamic_ load. The Key word being "dynamic". The electrical load changes with frequency, and lower frequencies, which require more power will also distort more quickly. The speaker rating is Static, sans audio load. An 8 ohm speaker in general can run from 4-12 ohms in typical use.

A speaker is functionally a linear AC motor, moving with the audio sine wave being fed to it. Instead of spinning around an axis, the motor coil moves forward and back within the magnet. 
As distortion goes up (with volume) the audio signal approaches DC, which will then burn out the fragile coil that fits inside the magnet and drives the speaker in and out.
Distortion in a speaker equals Heat. Heat destroys the fine wiring in the voice coil and sounds awful right up the point of frying the speaker and possibly the amplifier as well. 

_No matter what amplifier you use, or what speakers you use, if you hear any sort of distortion, turn it down and leave it down. _

This all applies to ANY speaker. Car, home, headphones, ear buds, and trains. 
No matter the advertising, a speaker is Analog because your ears only hear analog - the physical movement of air. 
As I used to tell my customers, there is no such thing as digital sound. 

To get the most out of either or both speakers, build a tight box around them. There are lots of on-line articles in many forums on how to do that. Even the smaller speaker will sound greatly improved once you've created a tight chamber around it, and will require less power to drive it. 

Happy Rails,
Bob


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