Ok this is pretty strange. I bought a pair of older Yorkville SW800's (18"
direct radiating / rear horn loaded sub) for a small bar. The back panels
indicate 800W program at 8 Ohms, but it's actually a 4 Ohm driver (RCF
L18/851N), which I suspect is 800W RMS.

The store tech said it's because that driver's impedence curve behaves like
an 8 Ohm driver in the sub-bass range. So I had the pair loading a bridged
RMX1450, 1400W into 4 Ohms bridged, and it had plenty of shove for that size
of room, but when I had to push bass guitar it would trip the thermal
protection occasionally, yet never lit the peak lights while operating. So
I switched it to stereo mode and drove them with the modest 450Wx2 at 4 Ohms
output, and holy ****! They were much more efficient, sounded much better,
and plenty more volume. No doubt the amp was previously working with too
small a load. I've now got an AP4040 on them (1200Wx2 @ 4 Ohms), and they
really kick ass, quite reminiscent of LA400's in terms of stiffness and
SPL's.

The question now remains that since EAW bought RCF, Yorkville has been using
Eminence drivers, so I wonder how well the LS808 compares to the SW800, and
if they've actually switched to a 400W RMS 8 Ohm driver, like the claimed
ratings suggest. The only appropriate driver Eminence lists is the 4 Ohm
Omega Pro 18, whose T/S parameters are reasonably close enough to use the
same cabinet, but certainly not as efficient

Actually I just discovered something even more outrageous. In the service
manual for all LS series subwoofers, it lists the SAME part #7458, 18" *4R*
800WPGM speaker in all of them, including the LS1208, whose declared rating
is 1200W program at 8 Ohms! The LS1004 says 1200W program at 4 Ohms, or
600W x2! Three subs, same driver, three different incorrent ratings!
http://yorkville.com/downloads/servman/smlsseries.pdf - page 3, "AP800 Parts
List 12/6/2005"

I'm going to email them and ask why they're marketing 4 subwoofers which all
have different incorrect power ratings, yet use the same driver. While I'm
at it I'll also ask them how a sub that used to employ a 99dB efficient
driver to produce 105dB @ 1W/1m, can still do it with Eminence's 95dB
efficient Omega Pro!

Oops, the LS1208 actually lists part #7460, 18" 4R 1200WPGM. Still
different from the posted ratings, and is not an Eminence product.

Zigakly wrote:

Oops, the LS1208 actually lists part #7460, 18" 4R 1200WPGM. Still
different from the posted ratings, and is not an Eminence product.

4 ohms eh ?

No surprise an RMX had trouble driving it bridged.

Graham

Zigakly wrote:

but when I had to push bass guitar it would trip the thermal
protection occasionally

For ages I've been saying that QSCs have lousy thermal capacity !

There's a limit to what one pokey 80mm fan can do cooling wise !

What did you expect ?

QSC only test @ 1/8 power !

Graham

but when I had to push bass guitar it would trip the thermal
protection occasionally

For ages I've been saying that QSCs have lousy thermal capacity !

There's a limit to what one pokey 80mm fan can do cooling wise !

What did you expect ?

QSC only test @ 1/8 power !

Graham

Actually that same amp drove a 2 Ohm subwoofer (pounding the limiter on
every kick shot) on one side and two 4 Ohm tops on the other for 2 years,
narry a problem, in fact it wouldn't get especially warm. It now drives
just the two 4 Ohm tops in stereo mode. It seems to have no ill-effects
from the three weeks it was driving a 2 Ohm bridged load all day and night
(house music is patched through PA), and it did get the job done adequately
despite the misconfiguration.

"Zigakly"

Ok this is pretty strange. I bought a pair of older Yorkville SW800's
(18" direct radiating / rear horn loaded sub) for a small bar. The back
panels indicate 800W program at 8 Ohms, but it's actually a 4 Ohm driver
(RCF L18/851N), which I suspect is 800W RMS.

The store tech said it's because that driver's impedance curve behaves
like an 8 Ohm driver in the sub-bass range.


** Maybe so - but the impedance will be back to around 4 ohms in the range
from 200 to 1000 Hz.

Be a damn good idea to plot ( or get a tech to plot ) an impedance curve
for the box.

IMO - all makers should be forced to publish them.




.......... Phil

"Zigakly"

Ok this is pretty strange. I bought a pair of older Yorkville SW800's
(18" direct radiating / rear horn loaded sub) for a small bar. The back
panels indicate 800W program at 8 Ohms, but it's actually a 4 Ohm driver
(RCF L18/851N), which I suspect is 800W RMS.

The store tech said it's because that driver's impedance curve behaves
like an 8 Ohm driver in the sub-bass range.


** Maybe so - but the impedance will be back to around 4 ohms in the range
from 200 to 1000 Hz.

Be a damn good idea to plot ( or get a tech to plot ) an impedance curve
for the box.

IMO - all makers should be forced to publish them.




.......... Phil

Phil Allison wrote:
"Zigakly"


Ok this is pretty strange. I bought a pair of older Yorkville SW800's
(18" direct radiating / rear horn loaded sub) for a small bar. The back
panels indicate 800W program at 8 Ohms, but it's actually a 4 Ohm driver
(RCF L18/851N), which I suspect is 800W RMS.

The store tech said it's because that driver's impedance curve behaves
like an 8 Ohm driver in the sub-bass range.



** Maybe so - but the impedance will be back to around 4 ohms in the range
from 200 to 1000 Hz.

Be a damn good idea to plot ( or get a tech to plot ) an impedance curve
for the box.

IMO - all makers should be forced to publish them.


Agreed!! There should be a benchmark to compare to.

when you want to get all matching stuff
let me know I need two 851's for my bh800's
george

when you want to get all matching stuff
let me know I need two 851's for my bh800's
george

Yeah I recall that, fact is that one of my SW800's was reconed in the past
year, and the other is pending reconing, terms of my purchase. The seller
is having issues getting a recone kit as well. In the meantime I have a
free rental of another SW800 that works well, but I managed to make it cough
when the recently reconed one didn't.

Perhaps because the ****heads were driving them in pairs with a bridged
MX1500 for the past 15 years...

Thankfully it's on paper that they owe me a reconed SW800, no matter how
much it costs them, in addition to the recently reconed one in my
possession.

I can't wait for them to try to pass me my other SW800 with an Omega Pro 18
in it...




[my dad's a lawyer]

On Tue, 07 Feb 2006 23:54:13 GMT, "Zigakly" wrote:

Ok this is pretty strange.

Measure the DC resistance. This is the closest you'll
get to an estimate of how the amplifier sees the speaker
as a load.

At low frequencies lots of reactive components increase
measured impedance, but the amplifier still must deliver
and absorb current from the reactances.

At higher frequencies, all kinds of stuff happens and
none of it matters (usually). Maximum power requirements
tend to be in the valley of woofer impendance range,
above the fundamental resonance(s) and below parasitic
reactive effects.

IOW, the DC resistance. Strange, but useful.

Good fortune,

Chris Hornbeck
r.a.p FAQ at www.recaudiopro.net

I HATE PROGRAM POWER

Program power is a garbage measurement unless several factors are published

i have only seen JBL publish it right

Program implies the peak value of an instantaneous power dissipation
based on a certain crest factor the crest factor is a multiple in DB

Assuming you have an 800 watt program sub measured in its published
range (whatever it is) on pink noise with a 6db crest factor

lots crap right

in english that means your speakers only have an RMS or true power of
200w despite calling them 800

lets up the crest factor to 9 DB

your 200 watt speaker now has a "Program" rating of 1600 Watts

Mystical numbers and fake truth

Now here is an example of program numbers done right so that i dont just
go slagging everything here is an example of a power rating done right

JBL Vertec 4887

Input power rating1: 225W (900 Peak) 100 hours

Then in subscript

1 AES Standard One decade Pink Noise with a 6dB crest factor within the
devices operational band. Free Air. Standard AES 2 hr rating plus long
term 100Hr rating are specified for cone transducers.

In english the Vertec is a 225Watt array RMS but the peak power could be
called 900 watts if someon wanted to be colorful with the truth


see how there can be some very colorful interpretations of the truth here?

Brent Philion

Zigakly wrote:
Ok this is pretty strange. I bought a pair of older Yorkville SW800's (18"
direct radiating / rear horn loaded sub) for a small bar. The back panels
indicate 800W program at 8 Ohms, but it's actually a 4 Ohm driver (RCF
L18/851N), which I suspect is 800W RMS.

The store tech said it's because that driver's impedence curve behaves like
an 8 Ohm driver in the sub-bass range. So I had the pair loading a bridged
RMX1450, 1400W into 4 Ohms bridged, and it had plenty of shove for that size
of room, but when I had to push bass guitar it would trip the thermal
protection occasionally, yet never lit the peak lights while operating. So
I switched it to stereo mode and drove them with the modest 450Wx2 at 4 Ohms
output, and holy ****! They were much more efficient, sounded much better,
and plenty more volume. No doubt the amp was previously working with too
small a load. I've now got an AP4040 on them (1200Wx2 @ 4 Ohms), and they
really kick ass, quite reminiscent of LA400's in terms of stiffness and
SPL's.

The question now remains that since EAW bought RCF, Yorkville has been using
Eminence drivers, so I wonder how well the LS808 compares to the SW800, and
if they've actually switched to a 400W RMS 8 Ohm driver, like the claimed
ratings suggest. The only appropriate driver Eminence lists is the 4 Ohm
Omega Pro 18, whose T/S parameters are reasonably close enough to use the
same cabinet, but certainly not as efficient

Actually I just discovered something even more outrageous. In the service
manual for all LS series subwoofers, it lists the SAME part #7458, 18" *4R*
800WPGM speaker in all of them, including the LS1208, whose declared rating
is 1200W program at 8 Ohms! The LS1004 says 1200W program at 4 Ohms, or
600W x2! Three subs, same driver, three different incorrent ratings!
http://yorkville.com/downloads/servman/smlsseries.pdf - page 3, "AP800 Parts
List 12/6/2005"

I'm going to email them and ask why they're marketing 4 subwoofers which all
have different incorrect power ratings, yet use the same driver. While I'm
at it I'll also ask them how a sub that used to employ a 99dB efficient
driver to produce 105dB @ 1W/1m, can still do it with Eminence's 95dB
efficient Omega Pro!

"Brent Philion" wrote in message
.. .
I HATE PROGRAM POWER

Program power is a garbage measurement unless several factors are
published

blah blah blah

program power for pro speakers is generally accepted as 2x RMS power

the Yorkville LS subwoofers being a remarkable exception...

In article ,
Zigakly wrote:

"Brent Philion" wrote in message
. ..
I HATE PROGRAM POWER

Program power is a garbage measurement unless several factors are
published

blah blah blah

program power for pro speakers is generally accepted as 2x RMS power

the Yorkville LS subwoofers being a remarkable exception...

Since the RMS power ratings of most pro speakers come from the marketing
department and are based on tenuous measurements at best, why would the
program power ratings be any better?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote in message
...
Since the RMS power ratings of most pro speakers come from the marketing
department and are based on tenuous measurements at best, why would the
program power ratings be any better?


Scott - I'll put my experience up against yours. And frankly are wrong. If
you wanna talk about Hi FI and car stereo junk you are right. But I think
most Pro speakers are honestly rated these days. And program is accepted as
twice RMS by virtually all manufacturers.

"liquidator" wrote in message
om...

Scott Dorsey wrote in message
...
Since the RMS power ratings of most pro speakers come from the marketing
department and are based on tenuous measurements at best, why would the
program power ratings be any better?


Scott - I'll put my experience up against yours. And frankly are wrong.
If
you wanna talk about Hi FI and car stereo junk you are right. But I think
most Pro speakers are honestly rated these days. And program is accepted
as
twice RMS by virtually all manufacturers.



isn't rms by definiton something like 70% of peak

so unless I am confusing terms or simply confused how can x= rms
x(1.3ish)= peak
then how can
2x= some point between rms and peak?
george

liquidator wrote:
Scott Dorsey wrote in message
...
Since the RMS power ratings of most pro speakers come from the marketing
department and are based on tenuous measurements at best, why would the
program power ratings be any better?

Scott - I'll put my experience up against yours. And frankly are wrong. If
you wanna talk about Hi FI and car stereo junk you are right. But I think
most Pro speakers are honestly rated these days. And program is accepted as
twice RMS by virtually all manufacturers.

How does it get this honest rating, then?

I have a recording here that is mostly top end. I play it into a speaker
cabinet rated at 200 watts, with a 200 watt RMS signal. The cabinet is
damaged.

Is this the fault of the rating, or because I misused it?

A single scalar value for "acceptable power" can never be accurate, because
the actual power handling of the speaker depends on the frequency, the
amount of time it's applied, and the actual power. You could probably
make a 3-D plot showing actual power handling, but it would just confuse
people to see real data.

So we get sort of meaningless numbers on the data sheet.

Note that I am talking only about SPEAKER ratings, rather than power amp
ratings. Power amp ratings are easy to make and mostly constant with
frequency in this era of transformerless output stages. As a result, you
can get an honest power rating for an amp if you try.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

liquidator wrote:
Scott Dorsey wrote in message
...
Since the RMS power ratings of most pro speakers come from the marketing
department and are based on tenuous measurements at best, why would the
program power ratings be any better?


Scott - I'll put my experience up against yours. And frankly are wrong. If
you wanna talk about Hi FI and car stereo junk you are right. But I think
most Pro speakers are honestly rated these days. And program is accepted as
twice RMS by virtually all manufacturers.



There is a standard test for long term power rating described in
ANSI/EIA RS-426-A 1980
It is a shaped noise spectrum applied for 8hrs to provide a test against
both thermal and mechanical failure modes
As an example EV describe their test setup for an SX300 as set at 300W
into the 7.1ohm EIA equivalent impedance at 46.2 V true RMS with
amplifier clipping the instantaneous peaks at 6dB above the continuous
power at 92.5 volts peak. Which you could imprecisely call 1200W peak.

They recommend that a skilled expert could use this speaker at its full
capacity with an amplifier with an RMS output 2 - 4 times the the long
term average power rating, but a more conservative normal amplifier to
use with it would be 1 - 1.4 times the long term average power rating.

The ANSI/EIA RS-426-A continuous power rating is quoted in the specs of
most pro loudspeakers since the mid 80s.

Brent Philion wrote:

I HATE PROGRAM POWER

Program power is a garbage measurement unless several factors are published

Read up about AES power ratings.

Graham

Zigakly wrote:
Ok this is pretty strange. I bought a pair of older Yorkville SW800's (18"
direct radiating / rear horn loaded sub) for a small bar. The back panels
indicate 800W program at 8 Ohms, but it's actually a 4 Ohm driver (RCF
L18/851N), which I suspect is 800W RMS.

The store tech said it's because that driver's impedence curve behaves like
an 8 Ohm driver in the sub-bass range. So I had the pair loading a bridged
RMX1450, 1400W into 4 Ohms bridged, and it had plenty of shove for that size
of room, but when I had to push bass guitar it would trip the thermal
protection occasionally, yet never lit the peak lights while operating. So
I switched it to stereo mode and drove them with the modest 450Wx2 at 4 Ohms
output, and holy ****! They were much more efficient, sounded much better,
and plenty more volume. No doubt the amp was previously working with too
small a load. I've now got an AP4040 on them (1200Wx2 @ 4 Ohms), and they
really kick ass, quite reminiscent of LA400's in terms of stiffness and
SPL's.

Okay, when you bridge an amplifier, you double it's VOLTAGE output, but
you don't double the CURRENT output. This means that a bridged amplifier
has a harder time driving low impedance loads, but can pput more power
into high impedance loads.

I'm going to email them and ask why they're marketing 4 subwoofers which all
have different incorrect power ratings, yet use the same driver. While I'm
at it I'll also ask them how a sub that used to employ a 99dB efficient
driver to produce 105dB @ 1W/1m, can still do it with Eminence's 95dB
efficient Omega Pro!

Probably because they have different cabinets. The cabinet tuning affects
the excursion a lot, as well as the efficiency. Thus, the power rating
changes.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote in message
...
Okay, when you bridge an amplifier, you double it's VOLTAGE output, but
you don't double the CURRENT output.

So far so good.

This means that a bridged amplifier
has a harder time driving low impedance loads, but can pput more power
into high impedance loads.


In theory but not always in practice. I have seen amps that will put out
just as much at the lower load. They are of course easier to thermal.

I'm going to email them and ask why they're marketing 4 subwoofers which
all
have different incorrect power ratings, yet use the same driver. While
I'm
at it I'll also ask them how a sub that used to employ a 99dB efficient
driver to produce 105dB @ 1W/1m, can still do it with Eminence's 95dB
efficient Omega Pro!

Probably because they have different cabinets. The cabinet tuning affects
the excursion a lot, as well as the efficiency. Thus, the power rating
changes.
--scott

Actually I've seen two side-by-side before, the only difference is the LS808
has a handle and wheels, which only changes the box volume by maybe 3-4L.
The horn flares are identical.

And my mistake, the LS808 uses a B&C driver, not Eminence.

The Yorkville tech claims that "It works out to apx. 8 ohms for the woofers
when loaded in the designated cabs." but it must be on the low side of 8,
since I've had the same RMX amp driving other 2-Ohm loads before and didn't
have any such issues. The DC impedence is 3.9 Ohms, and for direct
radiating 8 Ohm subs the DC impedence is typically around 7 Ohms. I can't
see the impedence being that different for the SW800/LS808's relatively
small horn flare.

He did make a valid point though, Yorkville wouldn't over-rate their
subwoofers when they have an unconditional two-year warranty on their amps.

I'm still confused, but I'm happy with the results I'm getting from an
investment of only $1650.

Zigakly wrote in message
. ..
The Yorkville tech claims that "It works out to apx. 8 ohms for the
woofers
when loaded in the designated cabs." but it must be on the low side of 8,
since I've had the same RMX amp driving other 2-Ohm loads before and
didn't
have any such issues. The DC impedence is 3.9 Ohms, and for direct
radiating 8 Ohm subs the DC impedence is typically around 7 Ohms. I can't
see the impedence being that different for the SW800/LS808's relatively
small horn flare.


Just nit picking- but it's DC resistance not DC impedance- comparing DC
resistance is not a way to compare impedances.

you are probably right that a small horn isn't going to cause that much of
an impedance rise. But you would have to graph the impedance plot to tell.

Zigakly wrote in message
.. .
The store tech said it's because that driver's impedence curve behaves
like
an 8 Ohm driver in the sub-bass range.

The impedance of a driver goes up in a horn loaded box.



The question now remains that since EAW bought RCF,

Just in the interest of keeping facts straight EAW never bought RCF. Mackie
owned both companies at one time but RCF has been an independent company for
some time now.

Zigakly wrote in message
.. .
Ok this is pretty strange. I bought a pair of older Yorkville SW800's
(18"
direct radiating / rear horn loaded sub) for a small bar. The back panels
indicate 800W program at 8 Ohms, but it's actually a 4 Ohm driver (RCF
L18/851N), which I suspect is 800W RMS.

The impedance of a driver goes up in a horn loaded box

The question now remains that since EAW bought RCF,

EAW did NOT buy RCF. RCF WAS part of Mackie but has been an independent
company for some time now.

Zigakly wrote:

The store tech said it's because that driver's impedence curve
behaves like an 8 Ohm driver in the sub-bass range.

Quite likely, but then there is the issue of phase angle. For a simple
guidelinie to probable amperage requirement match the resistance
measured via an ohm-meter to the amp specs. A nominal 4 Ohm unit then
ends up around 3.2 Ohms. You then count it like next lower step on the
ladder, and consider it a dynamic 2 Ohm load.

So I switched it to stereo mode and drove them with the modest
450Wx2 at 4 Ohms output, and holy ****! They were much more
efficient,

No.

sounded much better,

Amp sounded better.

and plenty more volume. No doubt the amp was previously
working with too small a load.

Read the power spec again, it may well be that the largest output power
is obtained in the next lowest permitted load. If all else fails, listen
..... O;-) ... 2 dB less or more in spl matters a lot less than sound
quality in the experience of the show.


Kind regards

Peter Larsen


--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

"Peter Larsen"

Zigakly wrote:

The store tech said it's because that driver's impedence curve
behaves like an 8 Ohm driver in the sub-bass range.


Quite likely, but then there is the issue of phase angle. For a simple
guidelinie to probable amperage requirement match the resistance
measured via an ohm-meter to the amp specs. A nominal 4 Ohm unit then
ends up around 3.2 Ohms.


** 3.2 ohms is merely the room temp, DC resistance.

At all audio frequencies, such a driver driver will have an impedance of 4
ohms or greater.


You then count it like next lower step on the
ladder, and consider it a dynamic 2 Ohm load.


** Why ????

The impedance cannot be less than 4 ohms.

Where the phase angle is high, the impedance will be 6 to 12 ohms.




......... Phil