Amp under-sized?? Marantz PM-47 (40w) amplifier + JPW P1 (70w) speakers.

This is my first post here.

I have an Marantz PM-47 amplifier from 1996. The label behind the case showing 8~16 ohm.

Online information shows:

Power output: 40 watts per channel into 8 ohm (stereo)
Frequency response: 10Hz to 50kHz
Total harmonic distortion: 0.008%
Damping factor: 60
Input sensitivity: 2.5mV (MM), 150mV (line)
Signal to noise ratio: 86dB (MM), 96dB (line)
Channel separation: 80dB (line)
Dimensions: 439 × 103 × 340mm
Weight: 5.4kg
Year: 1996

The two speakers are 2-way JPW P1:

Nominal impedance: 8 ohms
Power handling: 70 watts
Sensitivity at 1w/1m: 89dB

Is the Marantz amp (40w) too weak to handle the JPW speakers (70)? I see people recommending the power of amp should be 50%-100% more than the speakers. In my case, my amp should be 60~80w, right?

I find the sound quality of the speakers to be less satisfying although almost everybody from different online forums are praising the these speakers. I wonder if it is the undersizing of my amp?
 

Helix Hifi

Well-known Member
Not necessarily. This speakers are pretty efficient speakers. 40 watts is more then enough.

Sensitivity, ohm is more important then power handling. It only means 70 watts is the “minimum” power handling the speakers can tolerate.

However in the great scheme of things power handling means nothing. Since this are efficient speakers, 8 ohm speakers. The Marantz more then enough.

However the damping factor is 50. Over 100 is better. It means the amplifier we’ll control the speakers better.

You can drive this speakers with 100 watts amplifier if you like, but you need to be careful with the volume control.
 
Not necessarily. This speakers are pretty efficient speakers. 40 watts is more then enough.

Sensitivity, ohm is more important then power handling. It only means 70 watts is the “minimum” power handling the speakers can tolerate.

However in the great scheme of things power handling means nothing. Since this are efficient speakers, 8 ohm speakers. The Marantz more then enough.

However the damping factor is 50. Over 100 is better. It means the amplifier we’ll control the speakers better.

You can drive this speakers with 100 watts amplifier if you like, but you need to be careful with the volume control.
Thanks for the quick reply. Really appreciate.
 

Helix Hifi

Well-known Member
Soon other members we’ll help also.
 
Or should I connect the speakers in series instead of parallel (currently)? My amp is rated 8~16 ohms. Each speaker is 8 ohms. So, in series, it will be 2 x 8 ohms = 16 ohms and well within the specs.
 

Helix Hifi

Well-known Member
4 speakers? You didn’t mention this. No it we’ll not sound great. 2 speakers are more common. An amplifier with speaker A/B switch is more common for two speakers at one time. Not 4 speakers all the time. If you understand.

Also the amplifier won’t handle it. 4 speakers mean this amplifier gets far difficult load then what’s it is designed for.

2 ohm with 4 speakers!! Not recommended! I am not sure, but I believe it we’ll be 2 ohm.

The amplifier we’ll shutdown. In worst case ( most likely) the speakers well say bye bye.
 
I am waiting for more advice before i change the speakers from parallel to series.

So for the new series setup, the config will be as below for each left/right channel :

99303FFD-FEDC-4001-BF71-59ABB6D71914.jpeg


In this case, the overall impedance is 8 + 8 = 16 ohm, which is still within the rating of my Marantz amplifier (8~16 ohm)

This is a safer setup, right?
 

Helix Hifi

Well-known Member
@Orobas might answer this question.
 

Orobas

Well-known Member
@mrlawrencelam

Those JP's power rating is not what amp it needs.. but it's maximum power handling (rms)

So that 70w of the JPW means it can handle "UP TO" 70w of power....
Your PM-47 is fine at 40w .. just don't go overboard with the volume dial :) remember once that volume goes north of about 10 o clock on the dial.. you are already at full power and will be introducing distortion..
 
Thanks for all the valuable advice.

I have just re-wired the speakers. Now they are in SERIES (previously in parallel). That means from the amp, the current will flow through a Pioneer speaker (25w, 8 ohm) and then a JPW speaker (70w, 8 ohm). So total is 16 ohm. The Marantz amp is rated 8~16 ohm. Does that mean it is now safer to pump up the volume slightly compared to before in parallel? I don't see any difference in sound quality or volume before and after.
 

Orobas

Well-known Member
the higher the resistance.. the less power you get....

at 8ohm you have 45w from your marantz... if you go to 16ohm.. you are probably down to around 15-25w mark at a guess....

Also having 2 mismatched speakers will affect the sound too.. especially when one is only 25w.. and the other is a max of 70.. you are restricted by your smallest speaker in power now..

A speaker switch box, depending on the type will either give you a 16ohm or a 4ohm output depending on how they are wired.. but the fact is.. regardless.. you are limited by that 25w pioneer...
 

Helix Hifi

Well-known Member
I just don’t understand why you should connect one JVC speaker, one Pioneer speaker.

It’s going to mess up the soundstage. Two entirely different speakers with different crossover, different sensitivity.

It’s not optimal. However if you are happy, this is what counts😊
 

Khazul

Well-known Member
We seem to be getting alot of post from people wanting to use 2 pairs of speaker for some strange reason.

For those who are actually ok with the resulting sound, then maybe you dont need hifi and might be better off using a cheap multi-channel AVR in stereo party mode. At least then you get an amp per speaker and dont have to further torture a poor innocent little stereo amp. If more oomph needed, then at least you can add a sub and get bass management and have a proper blast.

Personally I dont much like most AVRs for music (seem a bit dull and lifeless, but then the same can be said of alot of pop production too), but really I hate multiple sets of speaker more but understand that can work well quiet localized background music rather than active listening which may suit some people better.

They may be better options for those who just need music everywhere and want it loud sometimes - with an active a sub taking a load off, then they can be more abusable, not to mention can be often safed from drunken idiots at a house party trying to crank the volume to max by presetting a volume limit...

Also maybe some of the dull lifeless pop production that has been inflicted on us over the years might actually sound more lively with the sub cranked, enhancer on and stereo to surround upmixing enabled :)
 
Last edited:

Helix Hifi

Well-known Member
It’s an never ending quest...
 

password1

Suspended
It will be fine as long as you're prepared for the amp to blow up, get hot or shut down or develop a fault.

Mismatched 2 pairs of speakers is not recommended. Stereo music is recorded in 2 channels, why would you want to add mis matched speakers? If the speakers don't fill the room then you need larger speakers or a sub.

A cheap AVR running in 4 channel giving each speaker its own channel will be safer.
 
I just don’t understand why you should connect one JVC speaker, one Pioneer speaker.

It’s going to mess up the soundstage. Two entirely different speakers with different crossover, different sensitivity.
Yes, I find the idea silly at first. After all the Pioneer is a pair of 25w from a broken cheapskate CD player.

I repeatedly experiment with
  • only a pair of JPW 75w speakers
  • the JPW + Pioneer

I also tested them with series and parallel connection.

I get the best result when I use JPW + Pioneer in parallel.

I am not a Hifi pro. I hope you can understand my description below:

With the JPW alone, I find the overall sound frequency to be very low. With the cheapskate Pioneer added, it brings up the pitch and give me a more "sharper" and 3D feel.

Currently the JPW speakers are not facing me. I will see if I can get rid of the Pioneer once I have repositioned the JPW.
 

Orobas

Well-known Member
Yes, I find the idea silly at first. After all the Pioneer is a pair of 25w from a broken cheapskate CD player.

I repeatedly experiment with
  • only a pair of JPW 75w speakers
  • the JPW + Pioneer

I also tested them with series and parallel connection.

I get the best result when I use JPW + Pioneer in parallel.

I am not a Hifi pro. I hope you can understand my description below:

With the JPW alone, I find the overall sound frequency to be very low. With the cheapskate Pioneer added, it brings up the pitch and give me a more "sharper" and 3D feel.

Currently the JPW speakers are not facing me. I will see if I can get rid of the Pioneer once I have repositioned the JPW.
In Parallel .. you are halving the speakers resistance.. taking them from 8 to 4ohm.. which increases the power from the amp from 45w to about 60-65w i think at 4ohm.. hence why your "Best result" is in that configuration
At 4ohms.. you amp is having to supply more current which ups the bass a bit too..

However.. the pioneer speakers will have been naturally voiced quite bass heavy anyway as that is what pioneer sounded like back then along with JVC and Kenwood!
 

Helix Hifi

Well-known Member
@mrlawrencelam, far from hifi is expert. Tons of other members far more skilled then me.

But I’ve learned few tricks up trough the years. Bought my first hifi kit in 2001.

After this there’s no going back. Getting SoundBar is going very sad day.

Drinking glass scotch, putting on jazz. Heaven. With SoundBar you need to be drunk.
 
1BE80A71-8D99-436F-89FA-AEF900F64070.jpeg
951D22B7-F2D5-44BB-9FE4-2E937F11D8D2.jpeg
Really good advice from this forum. Thank you for being patient with me. The next thing I need to do is to reorient the direction of the JPW speakers. Currently it is wall mounted too high and facing wrong direction.

Please see images below. Hope to get some advice. Both the JPW speakers are facing the RED WALL. I didn't think much about the drop of sound quality when I renovated the house 17 years ago.
 

Ugg10

Distinguished Member
Just put one pair, which ever your ears like after trying both, on the ends of the tv cabinet facing your seating position. This will be mikes better than those mounted up by the ceiling pointing at the wall.

If that works just get some foam isolation pads to reduce bass vibration of the cabinet.

4D195817-1579-44B3-96BC-C3AE30C673B2.jpeg


0C16ECC6-1D02-444D-8319-8715918FDB20.jpeg
 
@Ugg10 Thanks for the suggestion. Thanks also for taking time to sketch the position for me.

I think of this arrangement too earlier but wasn't sure if it was a good idea. Just felt a bit wasted for laying the wires underneath the walls 17 years ago.

But after seeing your suggestion, I quickly measure the width of the speakers and the space on the cabinet. They fit in nicely. I will go with your suggestion. After posting this message, I have to order some wires online. Thanks again.
 

password1

Suspended
They're fine where they are if they're only for a bit of quiet background mood music and not for serious music listening.

If they're used for the TV then the suggestion above would be more optimal.
 

gibbsy

Moderator
Lot of harsh surfaces in your room which is playing a massive part in what your are currently hearing. The high mounted speakers will be bouncing every which way. I agree with @Ugg10 that you should place the speakers on the cabinet have then on isolation pads or feet. The distance looks right to the seating area for a good stereo image.

I also agree that the ceiling speakers should be dispensed with as they are more likely that not having a very poor impact on the overall sound. Should you experiment with placing the speakers on the cabinet then have them sitting proud of the edge by around 25mm.
 

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