Active vrs passive - Page 81 - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 18th November 2012, 06:44 PM   #801
Pano is online now Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
Quote:
Originally Posted by SY View Post
I get 450 watts from Ohms law. (60V peak/1.414)2/4
I read:
Quote:
Originally Posted by Barleywater View Post
I come up with instantaneous power of about 450watts.
The instantaneous part means to me "peak", so I would not divide the voltage by the square root of 2 - but maybe that just my reading of the term. Anyway, it is explained above - thanks.
  Reply With Quote
Old 18th November 2012, 08:24 PM   #802
diyAudio Member
 
Join Date: Apr 2005
Location: Sitting behind the 'puter screen, in Illinois, USA, planet earth
Hi Barleywater

It’s worth pointing out that in audio two frames of reference are used and occasionally without realizing one isn’t the other.

The “peak value” as used in say with a signal the peak to average ratio, refers to the peak envelope value compared to the average value which is the long term heating value if one is dealing with heating power or a peak capture SPL meter.

If you use cool edit or other software, you can find these peak and average values for a given music track or short event.

For loudspeaker use, the “pink noise” or equal energy in all octaves noise signal has a Peak to average ratio of 6dB, this is used in many measurement systems is actually a little less dynamic range than a highly compressed FM station. Other systems use the old style 10dB peak to average ration which was the custom in RF and in this case more like a lot more like the dynamics of pop music.
In the latter case, a SLOW SPL meter has value X while the peak hold function is +10dB higher than X.

Some uncompressed music / hifi recordings can have 30dB or more peak to average but these sound “quiet” when played because the peak level is set by the medium while what we hear as loudness is much more like the average level (and why meter movement VU meters ignored short peaks).
OR, it could refer to the peak vs average value in a single sine wave or half sine wave.
But if one is dealing with sound specifications, one is stuck with the envelope definition while the true purest will examine the mic signal on a storage oscilloscope or the software equivalent.
For loudspeakers, the only real “peak spl” is the one you get when measure in a standard way, hopefully how it will be used and you convert the mic voltage.
Fwiw, 388 Watts with an 82dB sensitivity would produce 107.8dB in a perfect world, not 133dB.
10 X (Log (input power)) + 1W1M sensitivity = max output @1M in a perfect world.
133dB is actually harder than you might imagine to produce.

Take that driver, produce say 80dB spl at 1 meter (which is 68dB if you’re listening 4 meters from the speaker) , measure the harmonic distortion etc, raise the level 3dB and repeat.

Usually, somewhere around 1/10 to 1/8 the driver rated power (a figure which is derived in a near death test), you will see the response curve SHAPE start to change relative to the 1W response shape and this is when you are reaching the beginning of power compression or mechanical non-linearity etc.
Best
Tom
__________________
Bring back mst3k and futurama
  Reply With Quote
Old 19th November 2012, 01:32 PM   #803
diyAudio Member
 
Join Date: Jan 2008
Tom,

Thanks for shake out of math. 10 log for power, 20 log for voltage.

Continuing with burst testing, the brick wall 1kHz low pass test signal is filtered with Linkwitz-Riley 1kHz 24dB/Oct high pass, and also with 1kHz 1024 point FFT. Equal normalization is done to both and a response recording is made. Referencing for displayed results is -6dB at just below 1kHz for LR4 response:

LP1kFIR24k with HP1kLR4 and with HP1kFIR1k.gif

The LR4 high pass crossover filter results in generation of harmonic distortion and intermodulation distortion components, and in reality extend <1kHz. All of these show up as sum and difference side bands to desired pass band components.

FIR crossover results in lower level, well defined harmonic distortion generation.

The difference when crossover is implemented with LR4 v 1024 point FIR for my Pluto type speaker is night and day. Transient performance is truly cleaner. Sustained high levels are truly cleaner.

Regards,

Andrew
  Reply With Quote
Old 19th November 2012, 03:42 PM   #804
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by Barleywater View Post
Some details:

Square driver flange is milled round for mounting into end of 2" ID PVC pipe that is 12" long. Pipe is stuffed with Dacron, and other end is left open.

From recorded terminal voltage peaks (+/-) at center of waveform, -3.4dB is seen, corresponding to +/- 60.37 volts. Extrapolating this as true sine, this is divided by 2^0.5 for RMS voltage of 42.69 volts. Squaring this and dividing by 4ohms yields power of 456 watts.

I did not reference acoustic response for 1watt input, but driver specification is 82dB/1watt. This is horrible compromise made for size, cost, and intended applications. Nonetheless, at 388 watts this is 2^8.6 over 1watt or 6dB x 8.6 + 82db = 133dB estimated SPL.

I don't own any compression drivers, but have down loaded mp3 results from your previously posted links, and what I see is not impressive for domestic settings/critical listening, and is stock and trade performance for PA sound.

The maximal voltage swing is –46v to 60v. Sound is short, loud, and produces sensation similar to slapping palm of hand against ear. Ouch.
Barleywater,

Thanks for clearing up the details.
I think you would find (good) compression drivers to be quite clean at the same 133 dB SPL as you estimate your 82dB/1watt cone driver to be at 12".

With about 2 watts of input I measured 131.7 dBA at 13" from a B&C DE82TN 1.4” exit 3” diaphragm driver crossed at 1250 Hz (LR24) using a pink noise signal. At 6.5" from the driver's screen the level was 136.8 dBA.

At 2 watts, the driver is quite clean, at 128 watts, not so clean, but the level would be 167.7 dBA.

Probably quite a bit louder than slapping the palm of your hand against your ear, and smoke would emit from the cone driver long before that level .

Art

Last edited by weltersys; 19th November 2012 at 03:46 PM.
  Reply With Quote
Old 19th November 2012, 04:22 PM   #805
diyAudio Member
 
mondogenerator's Avatar
 
Join Date: Sep 2009
Location: City Of Villans
Blog Entries: 1
Art i agree. The one benefit of horn drivers, the low distortion due to their high efficiency can be wasted, even lower THD. (ive not been impressed yet, but im still young). The reason i am öt keen is due to the heavy duty diaphragm and voice coil former etc which is necessarmx for their intended use.
__________________
Every new piece of knowledge pushes something else out of my brain - Homer.....................Simpson
  Reply With Quote
Old 19th November 2012, 04:25 PM   #806
Pano is online now Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
I'm interested in what Barleywater is doing with the steep filters in terms of power handling and distortion. So far, I have not been crazy about the brickwall crossovers I've heard, but I have an open mind and ears.

If better power handling can be demonstrated for drivers like the little fullrange, that would go a long way in design. Getting clean, in room peaks at 105-110dB out of a "tweeter" like that would be great. Not breaking it would be even better.

What would be a good test level at 1M to simulate in-room peaks just above 100dB SPL? Remembering that two drivers would be used to achieve those levels in-room.
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 21st November 2012, 08:24 PM   #807
diyAudio Member
 
Join Date: Feb 2009
Location: UK
A tip for anyone wanting to do some experiments with active speakers without damaging them:

If the speaker has a port, simply disconnect the spade connectors at the drive units and thread your temporary cables in through the port(s). You can put a protection cap in series with the tweeter in the cable.

Just did this to a pair of B&W speakers in under an hour. Sounding good, but then they sounded very good in passive form too.

Kinda tempted to arrange a couple of relays so I can instantly swap between active and passive...
  Reply With Quote
Old 22nd November 2012, 05:49 PM   #808
diyAudio Member
 
Join Date: Feb 2009
Location: UK
In case anyone is interested, here are a couple of basic measurements of speakers before and after conversion to active (passing cables in through the ports!). My regret is that I didn't do anything to measure the insertion loss of the passive crossover. I'll do it when I convert them back.

In both cases the measurement is of a single speaker at about 1m in the listening room, traces averaged with 1/3 octave smoothing, using Room EQ Wizard and a WM61a mic with cal file off the WWW. The active crossover is your basic Butterworth-style linear phase done by a PC, without any phase or delay tweaking of any kind. 'Voicing' was highly involved and took almost 5 minutes. (I merely set the amp volume controls to get similar-ish traces between passive/active.)

The B&W DS2, is a two way, and I used an active crossover frequency of 2800 Hz 6th order. Passive is the red trace, and active the blue. Not a lot of difference!

The Tannoy R2 is a three way, and I used active crossover frequencies of 200 Hz and 2800 Hz, both 9th order. Passive is the magenta trace and red the active.

I've had a bit of a speaker-measuring, tweaking and listening binge this last couple of days, including writing my own software to correct individual drivers in various ways. What seems clear is that the basic character of the speaker comes through the passive-to-active conversion, and that a flat frequency and phase response does nothing to help a truly crap speaker!

Anyway, the Tannoys are sounding rather wonderful, now.
Attached Images
File Type: jpg bw ds2 before and after 2800_6.jpg (52.9 KB, 153 views)
File Type: jpg tannoy before and after 200_9 2800_9.jpg (53.6 KB, 152 views)
  Reply With Quote
Old 22nd November 2012, 09:14 PM   #809
diyAudio Member
 
mondogenerator's Avatar
 
Join Date: Sep 2009
Location: City Of Villans
Blog Entries: 1
I assume the bad passive is the 3way? One thing that put me off building a 3 way is the inversion of 1 driver, eg midrange, to align phase at xo points with a 2nd order passive network. Its bad enough in 2ways with a 2nd order network, aligning phase at Fc but sacrificing the original phase in the higher harmonics. Active for 3 ways and above makes perfect sense, but I feel its less significant in 2ways or a fullrange system. My stuck-in-the-dark-ages opinion is simply: The better a driver is, the lesser the need for EQ. Treat the cause to cure the symptom.
  Reply With Quote
Old 22nd November 2012, 11:59 PM   #810
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by CopperTop View Post
In case anyone is interested, here are a couple of basic measurements of speakers before and after conversion to active (passing cables in through the ports!). My regret is that I didn't do anything to measure the insertion loss of the passive crossover. I'll do it when I convert them back.

In both cases the measurement is of a single speaker at about 1m in the listening room, traces averaged with 1/3 octave smoothing, using Room EQ Wizard and a WM61a mic with cal file off the WWW. The active crossover is your basic Butterworth-style linear phase done by a PC, without any phase or delay tweaking of any kind. 'Voicing' was highly involved and took almost 5 minutes. (I merely set the amp volume controls to get similar-ish traces between passive/active.)

The B&W DS2, is a two way, and I used an active crossover frequency of 2800 Hz 6th order. Passive is the red trace, and active the blue. Not a lot of difference!

The Tannoy R2 is a three way, and I used active crossover frequencies of 200 Hz and 2800 Hz, both 9th order. Passive is the magenta trace and red the active.

I've had a bit of a speaker-measuring, tweaking and listening binge this last couple of days, including writing my own software to correct individual drivers in various ways. What seems clear is that the basic character of the speaker comes through the passive-to-active conversion, and that a flat frequency and phase response does nothing to help a truly crap speaker!

Anyway, the Tannoys are sounding rather wonderful, now.
1/3 octave smoothing is not revealing, and graph scale is tiny. What of reverse null response of crossovers? And what forms of waveform temporal distortions are revealed with burst testing? Distortion?

Phase response of your DSP crossovers may be flat, but what does REW show for acoustic response? Phase mayhem starts with coupling capacitors, including active capacitance of speaker diaphragms along with capacitors found in coupling between amplifier stages, as well voice coil behavior.


Quote:
Originally Posted by mondogenerator View Post
Art i agree. The one benefit of horn drivers, the low distortion due to their high efficiency can be wasted, even lower THD. (ive not been impressed yet, but im still young). The reason i am öt keen is due to the heavy duty diaphragm and voice coil former etc which is necessarmx for their intended use.
What? Low distortion due to their high efficiency? Whole principle of compression driver and horn is harnessing non linear properties of sound in high pressure air. The lower the distortion, the less efficient.

Regards,

Andrew
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Active or Passive bjackson Multi-Way 30 4th April 2005 10:49 PM
Passive into active MethMan Multi-Way 8 12th January 2005 04:58 PM
Active of passive audiobomber Multi-Way 9 31st July 2004 02:31 AM
dB loss by using passive crossovers? Active vs Passive and 1st vs 4th order Hybrid fourdoor Multi-Way 3 11th July 2004 09:16 PM


New To Site? Need Help?

All times are GMT. The time now is 01:41 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2