Need technical advice on amplifier & speakers.

[sand64]

Dear friends..

Being novice, I need your views on following two questions......

1. The SQ of my existing sterio system is good till I keep the volume knob within quarter. SQ is still OK till I crank it up upto half level, beyond which the distortion creeps in and it seems as if speakers are not able to cope with...... and sound starts booming. What does it mean??? My system is an old, unbranded but faithful one. I dont know its power rating but speaker pair (floorstanding) consist of 2x8" drivers 4" mid & a tweeter and a sticker at the back of speaker reads 4-way speaker system with power rating of 500w PMPO and 8 ohm impedence. Is my amp feeding more current to speakers?? Is there some mismatch of rms value?

2. If I presume that I need to replace existing speaker system with bigger ones....then I find that most of the budget speakers from brands like wharfedale, mission etc consist of 6" driver. So how does size matters in speaker systems????

Thanks if someone throw some light on above subject..

Regards.

 

[venkatcr]

1. The SQ of my existing sterio system is good till I keep the volume knob within quarter. SQ is still OK till I crank it up upto half level, beyond which the distortion creeps in and it seems as if speakers are not able to cope with...... and sound starts booming. What does it mean??? My system is an old, unbranded but faithful one. I dont know its power rating but speaker pair (floorstanding) consist of 2x8" drivers 4" mid & a tweeter and a sticker at the back of speaker reads 4-way speaker system with power rating of 500w PMPO and 8 ohm impedence. Is my amp feeding more current to speakers?? Is there some mismatch of rms value?

Distortion can happen at two places - your amp or your speakers. Though speaker distortion is rare, in your case as the system is old, the speaker could have worn out and could start to distort when pushed.

The most common reason for distortion is your amp. When pushed, an amp may not be able to create enough juice as demanded by the speakers and will start clipping. This leads to distortion in sound.

PMPO is non an industry standard and each manufacturer uses whatever figure he likes to mention PMPO. A lot depends upon the internal crossover used and how much voltage that it can take, and what is the speakers impedance. For example, if a speaker has fuse of 6 volts and it has an impedance of 8 ?, it peak power capability is calculated as

P(eak) = (6V)2 / 8? = 4.5 RMS.

It is nearly impossible to convert PMPO to RMS which gives a more accurate capability of both speakers and amplifiers. But, to take a shot in the dark, I would say your speakers (since it is four way and has a 8 inch woofer) could handle something like 40 watts RMS.

2. If I presume that I need to replace existing speaker system with bigger ones....then I find that most of the budget speakers from brands like wharfedale, mission etc consist of 6" driver. So how does size matters in speaker systems????

Unless we know the power rating of your amplifier, we cannot presume anything.

Driver size depends a lot upon what you are looking for. For most music applications, about 40Hz is the lowest signal you will ever get. That can be easily generated by a 6.5 inch driver driver by a good crossover. Modern drivers are well constructed, have better magnets, better cones, and can mimic an old 8 inch driver quite well.

The size of a driver also depends upon the size of the cabinet. The larger the driver, the larger is the cabinet that you need. Nowadays, people are not ready to keep large speakers at home, and are ready to compromise on sound quality vis-a-vis aesthetics. Thus manufactures are making speakers
of smaller sizes and trying to eke out the maximum possible sound from that size.

I would not be surprised if a modern speaker having 6.5 inch woofers generates better sound than a 10 year old speaker that had 8 inch woofers.

Cheers

 

[sand64]

Thanks venket for insight..

for the first question, my system is about 10 year old... and not run for extended sessions. The distorted sound at more than half level of volume control was observed from the very begining...since my purchase itself. So I feel perhaps the amp & speaker set was not matched perfactly.

Regarding distortion of SQ, the speakers never clip... but bass boominess is observed. Well I am not properly able to define this distortion but you can make out that there is mixing of different frequencies/nodes. Should I call it muddiness??? I have heard a system long ago in a friend's house and there tonal balances were maintained even at very high level of vol. control and you can distinguish different nodes cleary.

Also while calculating peak handling power, why have you muliplied 6v by 2 ? And in my case it is 40w rms per channel or 40w as pair?

Do throw some more light.

thanks & regards.

 

[sandeepmohan]

From what your saying it does look like a case where your amplifier is starting to struggle to push more power at higher volumes. Improper matching of impedance but more importantly the watts.

It could also be a case where your amplifier power supply is not sending enough current for the amplifier circuitry to run well at higher volumes.

I am a lover of custom made systems that do not cost much but it is in these systems where you find issues like these.

500 Watts PMPO makes no sense. Going by the speaker configuration you mentioned I doubt if it will be anything under 160 watts RMS per channel & this is no small figure for an amplifier to drive.

Try another Amplifier.

 

[venkatcr]

for the first question, my system is about 10 year old... and not run for extended sessions. The distorted sound at more than half level of volume control was observed from the very begining...since my purchase itself. So I feel perhaps the amp & speaker set was not matched perfactly.

If you have distortion from the beginning, then your amp and speakers are not matched, but more, important not made well.

Regarding distortion of SQ, the speakers never clip... but bass boominess is observed. Well I am not properly able to define this distortion but you can make out that there is mixing of different frequencies/nodes. Should I call it muddiness??? I have heard a system long ago in a friend's house and there tonal balances were maintained even at very high level of vol. control and you can distinguish different nodes cleary.

Speakers don't clip. It is the amplifiers that clip.

Your muddiness could be because of two reasons. If it happens in the amplifier, it is called Inter Modular Distortion or IMD. It could also happen in the speakers when the internal crossovers are not made well. Please read my post in Amplifier Burn In (http://www.hifivision.com/introductions/4939-amplifier-burn-3.html) for details on all amplifier distortions.

Also while calculating peak handling power, why have you muliplied 6v by 2 ? And in my case it is 40w rms per channel or 40w as pair?

That is the mathematical formula used to calculate Peak against voltage and impedance.

As I said before the PMPO figure has no value. I threw a 40 watts figure as a shot in the dark. Generally power of an stereo amplifier is calculated as watts per channel

Cheers

 

[sand64]

Thanks friends..

But I am in delimma. This means that I should replace my amp. or it is speaker's cross over problem. Speakers are 900x300x330 mm is size (without bass post) and to crarry them for audition is problem. Should I go for AVR?/

 

[sandeepmohan]

I won't recommend a AVR. Stick to a stereo amplifier with good specifications

 

[sand64]

Ok sandeep,

If not AVR then a stereo amp.? Then I will be having two stereo sets as I am not wanting to reject my existing system. After all SQ is good upto half the volume and db of this volume is enough.

But yes, I can connect both stereo amps with 5.1 'out' of dvd player to get the 5.0 (4 channels and front through TV amp). This is because i also want a bit of fun of occasional movie with 5.1.
OR
buy a AVR.

Do suggest...

thanks