| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 1281.1 | | SUBURB::PARKER | GISSAJOB | Thu Nov 01 1990 17:43 | 9 |
| I can't remember the calculations, but you want to make sure that the
impedance is right. If not properly matched, this could give the effect
you have noticed, particularly if your Clarion is rated RMS, and the
speakers are music power.
I suggest that you give us the power/impedance of both amp and
speakers, and that may give us a clue.
Steve
|
| 1281.2 | Its the amp. | CRATE::WATSON | Rik Watson | Fri Nov 02 1990 08:16 | 4 |
| What you probably hearing is the amplifier clipping. Its usually a
better idea to have a large amp and small speekers (power wise).
See UK_AUDIO (MARVIN:: ?) for more discussions.
|
| 1281.3 | have them with same ratings! | HOO78C::DUINHOVEN | Weird scenes inside the colemine... | Fri Nov 02 1990 08:40 | 6 |
| The output rating and matching speaker values should not differ a lot.
You'll loose a lot of sound quality when they don't.
You don't carry a small parcel in a big lorry as well!
Hans
|
| 1281.4 | | CHEFS::EDINBOROUGHS | Not Ken Dodd's Lovechild | Fri Nov 02 1990 09:35 | 21 |
|
I know the speakers to have a 4 ohms impedance. The hi-fi was given to
me by my father who ripped it out of his old car. Unfortunately it
doesn't have a sticker on it displaying the power. Is there a quick
way of testing this apart from ripping open the casing ?
One point I forgot to mention it that when four speakers are connected,
the other two being door mounted Blaunkplunt's, the quality of sound is
greatly enhanced. The 100w speakers decide to throw out more power
and they have much better response in all frequencies, but I believe
they are still not reaching their potential.
Another thing I noticed on the sticker of the 100w speakers is :-
Nominal power 50w.
Does this mean that my hi-fi has to throw out 50w of power before the
speakers decide they want to work correctly ?
Thanks for the replies so far,
Stephen.
|
| 1281.5 | | SUBURB::PARKER | GISSAJOB | Fri Nov 02 1990 11:12 | 8 |
| Again, I forget which way round it is, but if you wire an extra pair of
speakers in parrallell (or is it series?) you half the impedance, and
in series (or is it paralel) you double it. You also cut the perceived
power at the speaker by more than half. It all looks like the speakers
are ill matched to the amp. If it sounds better with all four
connected, why not just run them like that?
Steve
|
| 1281.6 | 50W RMS | HOO78C::DUINHOVEN | Weird scenes inside the colemine... | Fri Nov 02 1990 12:07 | 7 |
| 50 Watts nominal means RMS (Root means squire).
This is the real power possible with sinuswave.
The 100 W means peak load.
Anyway I could not live with 50 watts noise in a car.
Must be more than 100 db in such a small compartment!
Hans
|
| 1281.7 | Wrong impedance??? | VIVIAN::M_ELLAWAY | | Fri Nov 02 1990 12:50 | 8 |
| When you said the speakers work alot better when you connect another
two speakers to your system and that your speakers are 4ohm impedance
you are probably connecting them in series therefore doubling impedance
to 8ohms. As far as I can remember speakers tend to be either 4 or 8
ohms impedance, so it sounds like you have the wrong type of speakers
if you want just the two for your stereo.
Regards Martin
|
| 1281.8 | Use the front/rear outputs in Series | SUBURB::SCREENER | Robert Screene, UK Finance EUC | Fri Nov 02 1990 18:16 | 33 |
| Steven,
You will probably find the output of most amps in a Radio/Cassette is
rated around:
20 watts PEAK output x 2
6 watts RMS output x 2.
I agree with the crowd, it's probably the amp's clipping distortion you
are hearing. Check the installation manual about wiring for 2
speakers. There will be 4 wire pairs comming out of the set
(negative is the black/colour striped one of each pair).
If there are only 2 pairs comming out, and you are wiring in parallel
forget the following paragraph...
You will probably find that when only driving 2 channels you should use
the positive wire from the FRONT and the negative wire from the REAR
output. So you will be using the front and rear internal amps in
series. Don't just leave the front or the rear wires redundant.
Important:
Get hold of an installation guide for that Clarion model. It may be
that the above will not apply (and may ruin the internal amps
immediately). It may also be that the positive supply comes from the
rear, and negative from the front.
Rob.
p.s. I have speakers rated at 200w peak input, they still distort when
their amplifier is driven into clipping.
p.p.s. Yes I know 200w for a full-range speaker in a car is wild, but
I didn't but them for volume/SPL, they just sound superb!
|
| 1281.9 | Out of phase? | SUBURB::SCREENER | Robert Screene, UK Finance EUC | Fri Nov 02 1990 18:19 | 8 |
| You may also find that you wired the speakers out of 'phase'. Perhaps
got the +/- output swapped at the speakers.
It sounds really stupid I know, but I noticed my manufacturer supplied
cables had the wrong shaped terminals at the end. This caused me to get
it wrong, because I didn't bother to check the manufacturer's work.
Rob.
|
| 1281.10 | Crypto-Political Techno-Rant | KURMA::PFERGUSON | | Fri Nov 02 1990 18:42 | 47 |
|
Be careful of connecting the speakers in parallel.
This can damage your amp.
( Your home HiFi/Stack System/Music centre will likely say on the back
'use only speakers with nominal impedance 8ohms or greater.......for
similar reasons )
The reduced impedance means the amp tries to deliver too much current for a
given voltage and this can consequently waste the output transistors.
This is a result obtained from the maximum power theorm, the best you
can ever do is to deliver as much power as you dissapate internally in
the amp. This happens when impedances are exactly matched, something no
loudspeaker will ever manage....no matter what the manufaturer tells
you the impedance is.
If you connect them in series and it sounds bad then the amp may
not be powerful enough to drive the higher impedance.
This manifests itself as 'clipping' ( as a previous correspondent correctly
pointed out.)
Clipping should be avoided as it can damage you speakers.
He was also correct in saying to use a bigger rated amp than the speakers.
Car speakers tend to be efficient so you'd go deaf in ten minutes if you
drove them hard enough to damage them with too much (unclipped) power.
A car's not the best place for audio investment, it's the wrong shape,
made of the wrong things, too noisy and if you do have a decent tranny
some chap will soon separate it from your car.
Whew, that tale grew in the telling......I think I'll go and find a
HiFi notes conference and lie down for a while.
Peter
|
| 1281.11 | Guage to Current Capacity (amps) | SUBURB::SCREENER | Robert Screene, UK Finance EUC | Tue Dec 04 1990 17:51 | 39 |
| Cross posted in CSOA1::ELECTRO_HOBBY
There seems to be some electronic talent reading here, so...
I intend to invest in Oxygen-free Copper cable to connect amp to
speakers, through two 5 metre lengths of wire. I will have an amp with
claimed output of 140 watts peak per channel. Now running at about
12 volts, thats about 12 amps current.
I have a choice of 14 or 12 guage wire, costing �1.20 and �2.05 per
metre respectively. I want my wiring to be safe and edequate, but
don't want to waste a lot of money when re-wiring the whole system
later.
This raises my question:
How (roughly) does this 'guage' rating equate to SWG, metric wire
sizing (strands/mm-per-strand), maximum safe current (amps) and
maximum current (amps for clean audio signal transfer).
e.g.
Guage SWG Metric Max Current (amps) Desired Max (amps)
21
:
14 x y/yy z.z n
12
I have thumbed through my Father's 1977 Engineer's Yearbook (!) and
only found a Standard Wire Guage to Birmingham Wire Guage conversion
table, which has only served to confuse me more! Is what I am refering
to as 'guage' really AWG?
I do have a small table in a Car Hi-Fi mag listing amps against metric
sizes but nothing more. I have a very limited understanding of
electronics and have no background in the subject.
I would appreciate any help in understanding this.
Many thanks,
Robert.
|
| 1281.12 | | PRFECT::PALKA | | Tue Dec 04 1990 19:40 | 18 |
| I doubt you use 12 amps, unless you have very low impedance speakers.
If your speakers are 4 Ohm then the current at 140 Watts (peak) is
going to be about 6 Amps (peak). Your wire should not heat up to any
appreciable amount - it would probably degrade audio performance if it
had sufficient resistance to get warm. The spec for the wire may give
the maximum power speakers that can be driven by it. Or to put it
another way, you certainly dont want to waste even 10 watts of your
amplifiers output in heating the wire. The current limit for the wire
is not whether it is safe, but whether it produces good sound (which
is lower than the safety limit).
I believe that american mains wiring uses 14 gauge for a 15 Amp
circuit, and 12 gauge for 20 Amps. This is run inside walls, conduits
and other places where there is not much free air circulation. It is
also ordinary cheap copper, not high quality copper which presumably
has a lower resistance.
Andrew
|
| 1281.13 | SWG-->METRIC-->IMPERIAL (but not necessarily in that order)... | CHEFS::CLEMENTSD | Public Sector and Telecomms | Wed Dec 05 1990 09:06 | 72 |
| Cross-posted from SILK::ENG_IN_MINIATURE .......
<<< SILK::DUB1:[NOTES$LIBRARY]ENG_IN_MINIATURE.NOTE;1 >>>
-< ENGINEERING IN MINIATURE >-
================================================================================
Note 57.2 SWG conversion table? 2 of 3
CHEFS::CLEMENTSD "Public Sector and Telecomms" 61 lines 3-APR-1990 16:32
-< Full listing Of SWG Conversions >-
--------------------------------------------------------------------------------
Fuller list as follows.....
SWG Inches mm
7/0 .500 12.700
6/0 .464 11.786
5/0 .432 10.793
4/0 .400 10.160
3/0 .372 9.449
2/0 .348 8.839
1/0 .324 8.230
1 .300 7.620
2 .276 7.010
3 .252 6.401
4 .232 5.893
5 .212 5.385
6 .192 4.877
7 .176 4.470
8 .160 4.064
9 .144 3.658
10 .128 3.251
11 .116 2.946
12 .104 2.642
13 .092 2.337
14 .080 2.032
15 .072 1.829
16 .064 1.626
17 .056 1.422
18 .048 1.219
19 .040 1.016
20 .036 .914
21 .032 .813
22 .028 .711
23 .024 .610
24 .022 .599
25 .020 .508
26 .018 .457
27 .0164 .417
28 .0148 .376
29 .0136 .345
30 .0124 .315
31 .0116 .295
32 .0108 .274
33 .0100 .254
34 .0092 .234
35 .0084 .213
36 .0076 .193
37 .0068 .173
38 .006 .152
39 .0052 .132
40 .0048 .122
41 .0044 .112
42 .004 .102
43 .0036 .091
44 .0032 .081
45 .0028 .071
46 .0024 .061
47 .002 .051
48 .0016 .041
49 .0012 .030
50 .001 .025
Does this help?
|
| 1281.14 | | SUBURB::SCREENER | Robert Screene, UK Finance EUC | Wed Dec 05 1990 12:58 | 15 |
| Thanks.
Andrew,
So perhaps 14-guage will have plenty current capacity, over my 140w
peak output?
Dave,
How does one convert from guage/mm (solid core diam) into the
Metric notation for stranded cable (strands/mm-per-strand)?
I presume that you can't just divide by strands?
i.e. 2.032 mm (14-guage) does not equate to 50/0.4064.
Cheers, Rob.
|
| 1281.15 | | CHEFS::CLEMENTSD | Public Sector and Telecomms | Wed Dec 05 1990 13:27 | 11 |
| The SWG table gives a thickness (i.e diameter) from that you can work
out the cross-sectional area. The metric Strands/thickness per strand
can give a total cross-sectional area multiplying #'s of strands by the
area of each strand. That should give a reasonably accurate
relationship.
Two copper wires of the same material and the same cross-sectional area
should have the same resistance/unit length (specific resistance?) no
matter whether they are solid or stranded. I always thought that wire
was made from strands to make it more flexible. (Compare household
2.5mm Twin with Earth mains cable with the flex on an electric kettle).
|
| 1281.16 | | SUBURB::SCREENER | Robert Screene, UK Finance EUC | Wed Dec 05 1990 19:34 | 52 |
| Cheers Dave,
So I can convert between multi and single stranded, as long as they are
the same material.
So, to summarise the information I have recieved from both conferences
(from the many informative replies):
.........................................................................
. .
. AWG diam SWG Max Current Estimated .
. multi-strand- approx approx (amps) American .
. pairs (mm) Mains Current .
.......................................................... .
. 18 1.0 19 10 use of wire .
. 16 13 .
. 14 1.6 16 18 15 .
. 12 2.6 12 25 20 .
. 10 30 .
. 8 40 .
. 6 55 .
. 4 70 .
. .
.........................................................................
Note:
I have estimated the SWG for AWG gauges using the mm diameters.
The peak current from my amp will be around 6 amps, if the maker's
(usually optimistic) claim is to be believed.
Another question:
Are SWG and AWG really the same measurement? In England which of the two
does the term 'gauge' usually refer to?
I am going to have a read of a friend of a friend's reference book
tomorrow. Any criticism of my conclusions, and further help is very
welcome.
So, in answer to my initial problem, 14 guage (SWG or AWG) will be
sufficient to handle up-to >=18 amps. As the peak output is likely to be
1/3 of this, I guess the sound quality will not be effected by the
smaller cable.
Which cable would you choose?
Rear amp: �200
3-way spkrs �130 + �12/�20 pounds?
The other amp in my system is rated at 75w peak, so I would now
definitely NOT use 12-gauge OFC for the remaining 12 metres.
Rob.
|
| 1281.17 | | CHEFS::CLEMENTSD | Public Sector and Telecomms | Thu Dec 06 1990 09:28 | 9 |
| I don't think that SWG (Standard Wire Guage) and AWG (American Wire
Guage) are the same, but I'll check in another source. Don't get hung
up over the word "guage" it simply translates to "thickness".
Historically it arose out of the need to "guage" or "measure" every
piece of both plate and wire used for accuracy of nominal thickness
because of the tolerances accepted in the manufacturing process. Not so
necessary nowadays as when you get some sheet that is labelled 12SWG it
will be 104 thou +/- 2 thou no matter where you buy it. Same for wire
or rod. You can still buy the guages, though.
|