Full Range Line array Efficiency and Impedance Question? - diyAudio
Go Back   Home > Forums > Loudspeakers > Full Range

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 13th June 2009, 12:57 AM   #1
rjp366 is offline rjp366  United States
diyAudio Member
 
Join Date: May 2009
Default Full Range Line array Efficiency and Impedance Question?

After this opening paragraph, the rest was taken from a different web site.

Please tell me if it is accurate especially as concerning a line array of Jordan JXR6 drivers. Mr. Jordan states that a line array of 4 per side running with NO crossover will have more power handling than a typical subwoofer. I think it was something like, "The power handling limit of the entire system will be determined by the bass unit."


Efficiency of direct radiators doubles for every doubling of cone area (coupling) up to a maximum of about 25%.

Example:
A woofer of No=4% is about 98dB in 2Pi, a pair would be 8%, or 101dB, four would be 16%, or 104dB, eight would be 32% (but will probably only be our theoretical 25% maximum of 106dB).

Maximum output must also add the extra dB from power handling, ie: eight woofers handle 9dB more power than one woofer.

Adding our 9dB power handling to our 8dB maximum from coupling yields 17dB more maximum output than one driver. If one driver can put out 125dB at full power (including power compression), then eight should put out 142dB. Remember though, we are using 8x (9dB) more total power too.

For maximum coupling effect, drivers must be closer than 1/4W. This is not normally a problem for bass.
djk
  Reply With Quote
Old 13th June 2009, 03:43 PM   #2
Speakerholic
diyAudio Moderator
 
Cal Weldon's Avatar
 
Join Date: Jan 2004
Location: Near Vancouver
I don't see your question.
__________________
Next stop: Margaritaville
Some of Cal's stuff | Cal Weldon Consulting
  Reply With Quote
Old 13th June 2009, 05:13 PM   #3
rjp366 is offline rjp366  United States
diyAudio Member
 
Join Date: May 2009
Default Sorry, let me finish...

Sorry, I thought I was done typing but did not clearly explain what I was thinking!

I want to calculate the SPL level in dB/ 1 watt of the 4 driver Jordan array.
I want to calculate the power handling of the 4 driver Jordan array running full range with no crossover.
I want to use that information to indicate which woofer to match them up with.
I want to learn enough about these calculations so I can answer myself the same questions for 4, 6, 8, 10, or 12 drivers per side.

You see, I can believe that they would handle the same power as a 10 inch, $40 woofer but I am having trouble picturing them keeping up with an 18 inch JBL woofer!

I guess I should know exactly what power and what efficiency they have in order to match them up with the right woofer. And if they don't quite match up the way I thought, is there any need to use 6 or 8 Jordans in each line array?

Using the information in the first post, It seems that 4 drivers would produce 6 more dB than one driver, bringing the efficiency from 85 to 91. I guess if you have them with 2 in series and 2 in parallel the impedance remains the same so you get no additional SPL from drawing more current. Please tell me if I am wrong there!?

And the power handling is around 15 watts for one driver. (IT s not published everywhere. It might be 20 watts i am not sure) Does that mean that the power handling for 4 is 60 watts? How can that be more power handling than a typical woofer?

So now I am tired of typing. If you did not tire of reading this before now, I applaud you and thank you in advance for your comments!
  Reply With Quote
Old 13th June 2009, 08:54 PM   #4
diyAudio Member
 
norman bates's Avatar
 
Join Date: Nov 2003
Location: iowa
well, 10 drivers picks up about 10db.

I think your question is moot.

You will bottom those out very fast for home theater.
There is so much rumble and bass setting the tone of a scene.

Run wide open you will make them slam into the bottom of the magnet.

Yes theoretically if 1 can take 15 watts then 4 should take 60.
But they have a short coil and small xmax.
It's physics.

And going much beyond 4 drivers, you will have no high end.
You can add some eq, but it won't sound as good due to combing.
you could curve the array, but then there is only 1 sweet spot in an arc from the array. Stand up, slump your head down, move closer or further and everything collapses. Most would find that intolerable.....................

An active crossover, preferably 24db would protect them (2 or 4 array maybe 200-250hz). But I havn't invested in a good quality active crossover, my dbx sounds bad. Most of up cringe at the thought of anything muching up the audio. Some even abhor the idea of baffle step, pushing the boxes up against the walls and taking those drawbacks.

I believe these (jordans) are low volume listening only.

But hey, i'm not a speaker designer and I'm adding just another opinion to clutter up your thought process.

I'm working on a focused 9 driver array using 2" frames.
If you want to build something and find out, I recommend the peerless 830983 from parts express for $7.80 in 4+ quantities.
.13ft3 each has f3 near 185hz. You could build 4 in a flat array. I'm sure jordans sound better, but this would be a cheap way to experiment.


The jxr6 has a 90mm frame.
4 would need some eq.
But if I remember, the jordans response climbs a bit to offset this.

Bcherry (do a search at audioasylum.com) ran 4 of the 2" jordans in a frame touching vert array.
"The 4 driver array is singing happily for the past few months. The combing effect is not noticeable."
""Yes these are smooth like ribbons, except they play almost full range; the moving mass is only a bit more than a gram. Very SET-like sound."

"The net volume of the box is 16L, sealed and starts to roll off ~150hz. "

"I'm using 12ohms/2u2 (tuned by ear) and it's 80% there." (to boost highs)."

then 9 ran

Combing and lobing are noticeable as you move around; the stereo image shifts as you move laterally and hfs drop out when moing vertically so listening requires staying within a narrow sweet spot. ""I ran them in a couple weeks, but never found the highs to be rough; it was more a case of them opening up and becoming more extended and relaxed as they ran in. It is a very smooth driver and very revealing, more like a ribbon than a cone in performance."

"The 9 drivers give much improved dynamics (in our room compared to the 4driver array) and excellent coherence as they are driven 100hz to their hf limit. They needed compensation to tame a midrange bulge so some of the efficiency gain of a line array is lost but our 300B drive them comfortably in our largish room. I would describe the sound as very silky smooth and and high resolution. Combing and lobing are noticeable as you move around; the stereo image shifts as you move laterally and hfs drop out when moing vertically so listening requires staying within a narrow sweet spot....I'm thinking of adding a single ribbon tweeter (a Jordan would be better but a Fountek ribbon would pretty well match the system in efficiency) crossed over at about 6K (where combing becomes noticeable) to see if the hf issues can be resolved."

""The Jordans' cover 100hz to 25k so this is fullrange sound with bass augmentation. Voices are so smooth and violins tones richly textured.""

For the price of dual 9 jordan arrays, I'd rather buy a flat panel electrostat....................

Norman
  Reply With Quote
Old 13th June 2009, 09:10 PM   #5
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Default Re: Sorry, let me finish...

Quote:
Originally posted by rjp366
I want to calculate the SPL level in dB/ 1 watt of the 4 driver Jordan array.
+ 6dB

Quote:
I want to calculate the power handling of the 4 driver Jordan array running full range with no crossover.
x 4

Quote:
I want to use that information to indicate which woofer to match them up with.
I want to learn enough about these calculations so I can answer myself the same questions for 4, 6, 8, 10, or 12 drivers per side.
All that was buried in your 1st post. Except that it isn't really coupling (althou the drivers need to be in proximity) and the limit has more to do with absolute max SPL & not the drivers themselves.

Note that when you start stacking drivers up you limit the top end based roughly on the driver-to-driver spacing.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 13th June 2009, 09:44 PM   #6
diyAudio Member
 
HareBrained's Avatar
 
Join Date: Mar 2009
Quote:
Originally posted by planet10

Note that when you start stacking drivers up you limit the top end based roughly on the driver-to-driver spacing.
This is critical to the success of a line array (or any multi-driver speaker). The distance is center-to-center. If the drivers are all the same and they're touching, this is equivalent to the frame size. I'm sure you've seen truncated or square frames. The small amount gained by have a thinner edge amounts to a significant increase in range.

Some numbers: 75mm = ~4600Hz, 150mm = ~2300Hz.

If you use the drivers above the frequency corresponding to the c2c distance, the speaker will sound unfocused and muddled. Many people would say a "full-range line-array" is an oxymoron because of this. What I've found in listening to line arrays is that given sufficient distance from the array, the sound improves.

I've never designed a line-array, but for a first effort I'd definitely use 1 or more tweeters (depending on SPL of the array) as the chances of success are much better than without them.
  Reply With Quote
Old 13th June 2009, 10:47 PM   #7
diyAudio Member
 
norman bates's Avatar
 
Join Date: Nov 2003
Location: iowa
Harebrained,
I have 2 vert stacked four inch drivers with 5" frames (touching).

I sit with my ear on axis with the top driver 12' away.

Literally I play with pennies under the front to get the most highs.
1 penny makes a difference.

That's much more than a simple c-t-c formula.

The time offset is micro seconds, much smaller than any formula would say of timing errors affecting the high frequencies (size of the wavelength).

We are very sensitive to time (phase) and delay.
That's where the issues are.



Norman
  Reply With Quote
Old 14th June 2009, 12:09 AM   #8
rjp366 is offline rjp366  United States
diyAudio Member
 
Join Date: May 2009
Default Mr. Bates,

The opinions you passed on about the 4 driver array were all favorable weren't they?

I am guessing they handle power better than you think. Does the natural roll off in frequency response protect them from the BASS at all? And then spreading the power over 4 drivers helps even more.

I don't think Ted Jordan could recommend them to be used full range if they would bottom out all the time. Someone would have noticed that back at the factory :^)

I do respect your opinion. I do appreciate all your advice because I agree it is risky to plop down $1000 for 8 of them when I don't know what I am doing. I think you helped me decide to forget the JBL woofers and match them with the 10" seas or vifa instead!

The experience I have had was with the JX92s jordans and one pair of them produced a very satisfying 40-50hz response in an 11x14 sq. ft. room, certainly more than you would ever guess by looking at them!

Kind Regards...
  Reply With Quote
Old 14th June 2009, 12:53 AM   #9
diyAudio Member
 
norman bates's Avatar
 
Join Date: Nov 2003
Location: iowa
No problem, I enjoy discussing and chatting bout this stuff and am corrected often.

I agree the sealed box will give some protection, but 4 mini drivers asked to do 105db at 1m at 150hz will bottom out.

To me, you have to put the numbers into a simulator to see how much power it takes at what frequency to skip past xmax or slam into x-mech.

I understand that you like the jordans.

I would look forward to your opinion of a 4 array if you make one. The cone area would be 24cm2 x 4 and xmax of 6mm p-p or 3mm with 1.5g cone. The jr92s has 78cm2 but 9mm p-p or 4.5mm with 7g cone.

I believe that the 4 smaller ones will give better detail and wider dispersion, but the size of the frame, I'd be leary to go 4 in a vert array. 2 would be nice, or some way to do 3 without under 3 ohm load. And you may need a bit of hf boost.

Even the bandor had some high problems in an old review of the nonsuch 4 in HiFi magazine a while back.

I don't think many here have built the 4 driver arrays, but the FAST term is catching on (using full rangers and woofers).

For the money, the alpair 5 may be better but they have a larger 100mm frame......... 2 wired in a vert stack, inexpensive too.

If you want more sparkle than what you have, I recommend the jx92s plus aurum cantus g2si ribbon.

Norman
  Reply With Quote
Old 23rd August 2009, 06:26 PM   #10
sangram is offline sangram  India
diyAudio Member
 
Join Date: Sep 2002
Location: India
I'm working on (thinking about) an array of cheap 3" drivers, 11 in a line - and I have two questions related to the direction the thread has taken, but not the OP. didn't want to make a new thread.

The drivers are $6 each, made by Eastech, an OEM for some PC speakers. I have not managed to find the driver data (and don't have equipment to measure ). They have a very thin square frame, and look suitable for a vertical array with the surrounds literally touching.

I will be sitting on-axis to the middle driver of the array, and it will be LF-augmented with a couple of very sensitive (but low xmax/extension) side firing and back-to-back 12" woofers in a sealed isobaric configuration, and actively crossed over and amplified with a 2x50 watt chipamp. I expect to cross them over at about 300-330Hz.

My questions are:

1. With the ctc spacing of 75mm and a seating distance of about 9 feet, will lobing be audible if I power taper the drivers? I will be using the center driver at full power, the other will be wired in series-parallel so the whole array is about 4ohms. Individual drivers are 8 ohm, 30 watt power handling and go down to about 130Hz just fine. I'd like to cross over higher to get some decent power handling out of them (and because I will be running the center driver quite loud).

2. Does the width of the 'baffle' have any implications in the design - is there some kind of cancellation based on that width, or can I assume that it will basically mimic the response of a single driver?

Thanks for the help I'm basically using junk box parts for everything except the small fullrangers and the 'boxes'.
  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
Full range line array inrank Full Range 39 20th January 2009 12:27 PM
Jordan JX6 full-range line array bcherry Full Range 74 3rd April 2007 07:53 AM
Full-range line array? mazeroth Full Range 20 1st November 2004 03:47 PM
line array with full range drivers? leadbelly Multi-Way 9 25th January 2003 04:48 PM


New To Site? Need Help?

All times are GMT. The time now is 01:07 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