Suggestions for technical articles

[ODUODU]

1.) room accoustics - how to get the basics right
2.) measuring equipment that can be employed to help with room correction
3.) rms and pmpo - what's the difference?
4.) speaker design - open baffle or closed baffle?
5.) space age materials in speakers - is kevlar really that good?
6.) crossover quality - single most important electronic component in the speaker's signal path?

[joel]

I wrote an article on RMS vs PMPO for Speed and Sound mag a while ago.

Result was that according to my calculations, what I would call a 50 watt car amp (50 wpc at 4Ohm) could also be called asomething like a 3200 watt PMPO amp (dont remember actual figures).

I was accused of being too technical for SNS in hat article, but perhaps AVSA readers are a little more on the ball.

Perhaps I should find the article and rework it for AVSA or mail ot to Ampdog so he can see if he agrees with my calculations or not.
 

[Hi-Phibian]

PMPO=Practicaly Magical Power Output

Agree with 1, little theory and just a few easy to carry out practical solutions suggesting readily available materials.

[Ampdog]

OK,
not to start an explanation [which I do not think exists - you can really do with PMPO what you like (I mean the manufacturer)]

...but if possible take a look at the amplifier's mains power consumption; on the back-plate or in a manual (dangerous again). The power output for both channels cannot be higher; rather about 70% of that. Again that figure might be for stand-by power, but it will at least give an idea.

But in Joel's area (car amplifiers) that might be difficult. How exactly do those things specify power consumption, Joel?  Still, the above to give some indication (only ask the salesman for an explanation AT YOUR PERIL    ).

[joel]

Hi Amp

Very few car audio amplifier manufacturers rate consumption, but almost all put a fuse on the amp.

I always recommend that people look at the PMPO rating, then look at the fuse, and multiply fuse rating by 12.

I then explain that maximum power (even assuming 100 % efficiency) can be no more than fuse rating times power supply. I then let people decide if their amplifier can actually make the claimed power.

I dont argue anymore if they still think that their amplifier is actually as strong as they think it is.

FYI I have been told (by a distributor) that class D amplifiers are capable of making more power than they consume. Silly me thought that Ohms law was a law and not a theory. I still learn new things everyday

 

[Blues]

actually I believe that everybody serious about hifi knows what to think about pmpo (pimp my power output) ratings. it could even be regarded as a time saver, since when I see pmpo stated, i don't waste anymore time on that unit...

but I'd also be interested in articles about room acoustics/ treatment, speker placement, as well as fundamental differences between different technologies like ss/ tube amps and speaker designs (open baffle, bass reflex, ribbon speakers and so on).

[RR]

FYI I have been told (by a distributor) that class D amplifiers are capable of making more power than they consume. Silly me thought that Ohms law was a law and not a theory. I still learn new things everyday

Are you talking about 'Digital' amps or narrow bandwidth Class D (or C) amps as typically found in subwoofers?

Wrt Digital amps AND to a lesser extent the other type of Class C/D, I have heard that as well (more RMS power than AC power consumed) would be interested to know why. Anybody has an (understandable ) explanation?

RR

[chipwelder]

Yes they don't know about the law that energy can't be created or destroyed, it can only be transformed into a different form.
Well I guess RMS is also not a given i.t.o measurement so you could measure spikes on a cold day in hell, that would seem to be incongruent with the above.

[Mervin]

Floccinaucinihilipilification of Class-D being the source of Eskom's problems?
Now that is an oxymoron if I ever saw one... ROTFLHMT

[Shonver]

... ROTFLHMT

ROTFLHMT ??!!! holding my tummy? ... and that other word?

[Mervin]

Floccinaucinihilipilification - the act to determine if something is worthwhile... but I have used it in the way of indicating depreciation of value.. (also accepted) longest english word (non technical) and also without an 'e'.

[Rodney_gold]

computer Audio for Old Geezers.....Seriously

[Mervin]

Old Geezers?   I am as young as the girl I feel 
....'BUT OFFICER!  SHE SAID SHE WAS 18!'...

[KenM]

I guess some people think you can get a quart out of a pint jar (hands up all those young enough not to know what on earth a quart is). The way I always try to explain it is that an output transistor - or valve, if you insist on being pedantic - is little more than a remote controlled tap that sends the mains power - softened somewhat by the PSU - to your speakers in sympathy with the incoming signal. An amplifier can therefore never deliver more power than it can receive, the same applies to a car audio system with even heavier constraints with respect to the power available.

Back on topic. The HD PVR requires 4 input cables, 1 for tuner 1 used for watching, 2 and 3 for tuners 2 and 3 used for recording and 4 for tuner 4 used for the EPG and other stuff. If your existing dish has a dual LNB then you need a multiswitch which accepts the 2 inouts and has 4, 6 or 8 outputs. There are different manufacturers of multiswitches as well as active or passive ones. I suggest that AVSA look at these multiswitches and maybe do some tests on the virtues - or lack thereof - of the different makes and philosophies.

[georgev]

Room Acoustics definitely and the influence of room acoustics on the sound.
Valves vs. transistors how do both work, not a face off.
aLL these confusing terms. PCM LPCM etc, in a laymans terms.
Just some thoughts.