Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

The birth of a 15 inch woofer
The birth of a 15 inch woofer
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 26th August 2019, 07:28 AM   #31
JMFahey is offline JMFahey  Argentina
diyAudio Member
 
JMFahey's Avatar
 
Join Date: Mar 2009
Location: Buenos Aires - Argentina
Looks very good so far, congratulations.

Can you please link to the full "JBL document" where this graph was copied from?

Click the image to open in full size.

Would love to read the rest.
Thanks.
__________________
Design/make/service musical stuff in Buenos Aires, Argentina, since 1969.
  Reply With Quote
Old 26th August 2019, 01:32 PM   #32
oks81 is offline oks81  Norway
diyAudio Member
 
Join Date: Jul 2014
Here is the JBL document, and som more.

TECH NOTE 1-3A
__________________
  Reply With Quote
Old 26th August 2019, 01:41 PM   #33
Snickers-is is offline Snickers-is  Norway
diyAudio Member
 
Join Date: Nov 2004
Location: Rakkestad
Send a message via MSN to Snickers-is
Thans Oks!

If you want to read more, there are tons of stuff here:
JBL Technical Notes
__________________
Live sounds better than HiFi.
  Reply With Quote
Old 26th August 2019, 02:18 PM   #34
JMFahey is offline JMFahey  Argentina
diyAudio Member
 
JMFahey's Avatar
 
Join Date: Mar 2009
Location: Buenos Aires - Argentina
Thanks to both
__________________
Design/make/service musical stuff in Buenos Aires, Argentina, since 1969.
  Reply With Quote
Old 26th August 2019, 05:23 PM   #35
oks81 is offline oks81  Norway
diyAudio Member
 
Join Date: Jul 2014
When reading the JBL tech notes, the ones about their low frequency drivers.
I see they often mentoin and show curves of 2nd and 3rd harmonic distortion.
It looks like it has been their main object to reduce these distortion figures.

Example in the Vol.1 No9: Distortion and power compression in low-frequency transducers:
http://www.cieri.net/Documenti/JBL/T....1,%20No.9.pdf

How about the higher harmonic and non harmonic distortion?
Like in an amplifier the higher harmonic is really unwanted, and the 2nd and 3rd we are not so "afraid" of. Like in single ended amps.

How are your toughts about this into the plans of your bassdriver Snickers?
__________________
  Reply With Quote
Old 26th August 2019, 08:25 PM   #36
Snickers-is is offline Snickers-is  Norway
diyAudio Member
 
Join Date: Nov 2004
Location: Rakkestad
Send a message via MSN to Snickers-is
I have to warn you that that question is fairly large. We could easily fill a book about just that, so let me take this a bit more in general first. I have some not yet covered issues that should further highlight this area, but at bit of sneak peak should not hurt anyone.

The very short answer is that the weighting between high and low harmonics tends to tilt towards higher harmonics as the driver reaches its limits. This means, if you can keep 2.nd and 3.rd harmonics really low, you would most likely have extremely low 4.th, 5.th, 6.th, 7th... etc.

But an increasing high order harmonic contribution is also some degree of proof that one has some serious non harmonic issues as well. An example of this is violent break up, which is normally measured as harmonic distortion, but what it actually is is a high Q resonance that completely breaks down waveform shape and leaves a broad spectrum of harmonic components.

A loose wire would also measure as harmonic distortion at some frequencies. A suspension that has come loose, leaks air, and flaps around making buzz at certain frequencies will also measure as harmonic distortion. It is fair to say that if 2.nd and 3.rd harmonics are well under control, you most likely do not have too many other distortion issues either.

That being said, energy storage in the moving parts is a very common source of non linear distortion that does not show as harmonic distortion. Many drivers have extremely nice parameters and measurements, but still sound a bit muddy or colourless. A really great driver is able to reproduce the fine and most gentle details with finesse, but is also able to reproduce grand transients with all of their energy, impact, slam, timing, tonal balance and low distortion in an absolutely convincing way. Some drivers does not do that, and it does not always show on the T/S data.

Factors that can make energy be stored and released from the cone is if the cone is very soft and has high internal damping. But also, if the cone is connected to heavy suspension and a heavy voice coil, this could mean trouble.

There are also an ever ongoing discussion of conductive or non conductive voice coil former. A conductive voice coil former will form eddy currents while moving through the gap. These currents will induce some heat in the former, which in turn translates to damping. A smoother frequency response is often the result. The distortion curves are often not that affected, but still many argues that drivers with conductive voice coil formers sound more dull and less lively. Since the former is places where the energy is induced into the cone, it is not necessarily the ideal place to add damping, so that might explain why this solution is less popular than what the smoothed response would indicate.

I will dig a bit further into the different distortion sources described in a previous post later. I am not sure if I have answered your question properly, but I will relate all of that, and more, to the choices made for this exact driver.
__________________
Live sounds better than HiFi.
  Reply With Quote
Old 27th August 2019, 04:25 PM   #37
oks81 is offline oks81  Norway
diyAudio Member
 
Join Date: Jul 2014
Thanks for good and thorough expelenation!
Yes I know the subject is large.

I learned quite a bit from your answer!

Maybe what I was thinking was more about the motorsystem.
In the JBL notes we find how they first with the SFG, later the SVG, and last Diff Drive have been working with lowering distortion.
The motor in your driver will be diff. drive and saturation in the VC gap.
That will bring the flux in the gap to 2,2T or so?
How much improvement will the saturated VC gap give?
I cant find other bassdrivers that has so much flux.
As an example the TAD 1601 has 1,24 T in the gap.
__________________
  Reply With Quote
Old 28th August 2019, 03:08 AM   #38
Drofdissonance is offline Drofdissonance
diyAudio Member
 
Join Date: Jun 2016
Quote:
Originally Posted by Snickers-is View Post
That being said, energy storage in the moving parts is a very common source of non linear distortion that does not show as harmonic distortion. Many drivers have extremely nice parameters and measurements, but still sound a bit muddy or colourless. A really great driver is able to reproduce the fine and most gentle details with finesse, but is also able to reproduce grand transients with all of their energy, impact, slam, timing, tonal balance and low distortion in an absolutely convincing way. Some drivers does not do that, and it does not always show on the T/S data.

Factors that can make energy be stored and released from the cone is if the cone is very soft and has high internal damping. But also, if the cone is connected to heavy suspension and a heavy voice coil, this could mean trouble.
most of the stuff you mention here (stored energy etc) doesn't show up as harmonic distortion as it is a kind of linear (frequency response) distortion its actually correctable with FIR filtering.
  Reply With Quote
Old 28th August 2019, 04:49 PM   #39
Snickers-is is offline Snickers-is  Norway
diyAudio Member
 
Join Date: Nov 2004
Location: Rakkestad
Send a message via MSN to Snickers-is
Quote:
Originally Posted by Drofdissonance View Post
most of the stuff you mention here (stored energy etc) doesn't show up as harmonic distortion as it is a kind of linear (frequency response) distortion its actually correctable with FIR filtering.
I am not too sure about that. It has causality intact, but the pattern tends to be somehow random. A bit like thermal noise, which per definition is random.

Have you tested this and made ETC after correction to see if it works?
__________________
Live sounds better than HiFi.
  Reply With Quote
Old 29th August 2019, 07:53 PM   #40
Ultima Thule is offline Ultima Thule  Europe
diyAudio Member
 
Ultima Thule's Avatar
 
Join Date: Jan 2004
Location: PKS, Finland
Quote:
Originally Posted by Snickers-is View Post
So the frame I went for is not the kind you would think of for a "5000W car audio competition subwoofer", but rather a transparent one that is far more sturdy than we would ever need, and in addition has some decent openings for air to escape from under the spider. It also has the necessary depth I need from surround landing to spider landing for a 15 inch cone with 3 inch voice coil (which naturally has a deeper profile than what it would with a 4 inch coil), good height from spider landing to motor mount to allow some serious excursion before something is damaged, and last but not least, a spider landing of respectable 204mm to allow for a more linear suspension.
Hi Snickers-is, interesting project, looking forward to see how it develops.
I am curious where we can find that aluminium basket and woofers as shown in the pictures, do you have any web link or name of product/manufacturer to share with us?
  Reply With Quote

Reply


The birth of a 15 inch wooferHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Best 8 inch woofer? acstcwrfrmn Multi-Way 95 3rd September 2019 11:43 AM
8 inch woofer for WAW Cerniu Full Range 31 25th June 2018 08:17 AM
Audax pr170mo Woofer selection... which 15 inch woofer 98db eff... youknowyou Multi-Way 15 20th June 2017 05:37 AM
Matching 12 inch woofer with 4 inch mid awdtalon21 Multi-Way 7 7th June 2017 04:43 PM
WANTED: 6-7 inch pro mid/woofer or some small box woofer Jimmy154 Swap Meet 10 18th August 2012 12:01 PM


New To Site? Need Help?

All times are GMT. The time now is 09:02 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki