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 11th September 2019, 11:59 AM   #61
badman is offline badman  United States
diyAudio Member
 
badman's Avatar
 
Join Date: Sep 2003
Location: Ashland, MA
Quote:
Originally Posted by Snickers-is View Post

By adding this oval ring, and gluing the spider completely to it,
The only challenge I'd have would be to ensure sufficient glue area and strength, and enough overlap past the ring to ensure that it doesn't rub, but this is certainly an interesting idea.
__________________
"The dawn of Bose created the "Man Cave" and reduced testoterone levels worldwide by 18.5 per cent" Peteleoni
  Reply With Quote
Old 11th September 2019, 03:25 PM   #62
Hydrogen Alex is offline Hydrogen Alex  United Kingdom
diyAudio Member
 
Join Date: Dec 2014
Location: Cambridge
Quote:
Originally Posted by Snickers-is View Post
I believe it will end up around 5-600 USD/pc, and it is hard to get a classic TAD, Coral, Altec, Fostex etc. for that kind of money these days.
Not sure if you just building 1 pair or tooling up and buying parts in 20's which is the minimum for OEM prices, but please research the massively important but rarely discussed " Voice coil induced Thermal Distortion"

See the attached PDF by the genius Michael Gerstgrasser and his website here: Audio and Loudspeaker Design Guide Lines

PS, The attached Beyma 15 inch sounds superb crossed over at 800Hz to a broad band / full range driver, never tried a CD / horn but would be even better I guess. With Eq its flat to 30Hz at 105dB continuous (AES) SPL.
Attached Files
File Type: pdf Voice coil thermal distortion.pdf (120.8 KB, 9 views)
File Type: pdf Beyma 15 P80 Fe N.pdf (216.3 KB, 17 views)
  Reply With Quote
Old 11th September 2019, 04:38 PM   #63
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 badman View Post
The only challenge I'd have would be to ensure sufficient glue area and strength, and enough overlap past the ring to ensure that it doesn't rub, but this is certainly an interesting idea.
I have been thinking about this, and I think the solution is pretty safe:

The birth of a 15 inch woofer-resonance-control-ring-jpg

As you can see, the shape of the ring (where it is in contact with the spider) has the exact same shape as the spider. The spider should, off course, be fully glued to the ring. Any missing glue could quickly turn into some noise.
Attached Images
File Type: jpg Resonance control ring.jpg (209.0 KB, 465 views)
__________________
Live sounds better than HiFi.
  Reply With Quote
Old 11th September 2019, 05:07 PM   #64
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 Hydrogen Alex View Post
See the attached PDF by the genius Michael Gerstgrasser and his website here: Audio and Loudspeaker Design Guide Lines

PS, The attached Beyma 15 inch sounds superb crossed over at 800Hz to a broad band / full range driver, never tried a CD / horn but would be even better I guess. With Eq its flat to 30Hz at 105dB continuous (AES) SPL.
I am afraid this distortion document has some serious errors.

First of all, the way heat behaves in speakers. You do not have 115dB contineously in a speaker like this. It is, off course, possible, but 115dB on average is extremely loud. Even peaking at 120dB you rarely experience as much as 111dB contineous power over a 10 second period. That is 1/8 of the power, so if you have 115dB transients (which is how I read the document) you have just over 1W.

Secondly, assuming the cooling factor of the coil is far above 100K/W really does not make sense, not even for a tweeter. In the example shown in the link, he uses a 1 inch dome tweeter. My driver has 120 times the surface area and 4 times the efficiency as that tweeter.

But the really bad part of the document is how he handle numbers. First off all, if you increase the Re from 5,5 to 7,5 ohm, it does not add distortion. The parameters change, but it does not add any kind of distortion by itself. The change in T/S-parameters is real, but that is not a source of distortion by itself. As far as I can see, he assumes that the coil changes its temperature for every signal period (in his 10kHz example that means cooling from 120degrees to 20 degrees, and heating up again, 20 000 times every second). That would lead to a heavily modulated sound due to the rapid changes in T/S parameters, but we all understand that it is not going to happen anywhere near as fast as this.

The reduction in sensitivity, resulting from the reduction in current, is also real, but even with a 35% reduction in the current, the difference in output power equals a reduction in the pass band of about 2dB. This is not happening in every signal period, but even if it did it would still be less than 1% harmonic distortion.

So, as you understand, I have taken care of heat in this motor, but the reason why I have done that is not because it causes harmonic distortion, but because it changes the way the drivers sensitivity (relative to other drivers in the same system) and because it changes the relationship between the resonant response and the pass band (AKA T/S-parameters).

Even running really hard, It is highly unlikely that you will ever see more than 20 degrees increase in temperature. This is probably not going to translate into measurable distortion. The change in T/S parameters will be minor, and the change in both temperature, BL(x), Le(x) and suspension has been extremely precisely simulated, and it leads to the change you can see here:

The birth of a 15 inch woofer-zzz_test_15_inch_spl-png

As you can see, the change of intensity in the pass band is extremely small, and this is at a dynamic 150W input power, delivering 123dB for two drivers, one in each stereo speaker. The change in the resonant part (low frequency roll off) is also minor.

Remember that this not only includes voice coil heating, but also all other changes that would occur. This is a kind of a "worst case scenario".
Attached Images
File Type: png ZZZ_Test_15_inch_SPL.png (25.4 KB, 443 views)
__________________
Live sounds better than HiFi.
  Reply With Quote
Old 11th September 2019, 05:10 PM   #65
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 Hydrogen Alex View Post
Not sure if you just building 1 pair or tooling up and buying parts in 20's which is the minimum for OEM prices
The interest is really strong, and I have also been contacted by a loudspeaker manufacturer, so I most likely have to make at least 100 pcs. This is also why I have suggested s price.
__________________
Live sounds better than HiFi.
  Reply With Quote
Old 19th September 2019, 10:20 PM   #66
ICG is offline ICG  Germany
diyAudio Member
 
ICG's Avatar
 
Join Date: Jul 2007
Location: I had a Déjà Moo - I've seen that BS before!
Quote:
Originally Posted by Snickers-is View Post
@ICG:

I believe all of the issues you mention in your post are well covered by previous answers. For the purpose of the thread, I see no point in discussing those details further.
Actually, the issues are indeed not be covered at all. Intermodulation distortion is a HUGE issue and not adressed properly before. You've mentioned it but actually did not answer to oks81's argument nor mine. Since intermodulation isn't a harmonic distortion, it's VASTLY undervaluated by you. The problem is, since it's not a harmonic and even less a linear distortion, it is an issue you haven't adressed AT ALL and will have a huge influence on the sound reproduction in the midrange.

Aside from that, you did not have taken into account that any impedance control (pole plate copper cover or aluminium pole plate ring) will impact your magnetic flux, because it increases your effective air gap - the aluminium or copper ring does not 'count' towards the magnetic structure. And since you've planning on a double coil drive with two gaps, your calculation is off by at least factor 4, but since your 'brilliant' impedance compenstaion construction by most likely by 8 to 20x. Which means, you'll have to increase your magnetic motor by approximately that factor. That is the exact reason why double coil drivers are actually NOT used in the midrange.
__________________
I had a Déjà Moo - I've seen that BS before!
  Reply With Quote
Old 19th September 2019, 10:56 PM   #67
ICG is offline ICG  Germany
diyAudio Member
 
ICG's Avatar
 
Join Date: Jul 2007
Location: I had a Déjà Moo - I've seen that BS before!
Quote:
Originally Posted by oks81 View Post
First, as phase_accurate says, it doesn`t mather if the coils are in parallell or in series.
Well, mo matter if he says that, physics say otherwise. It's an actually very easy equation, since amplifiers are - in general - voltage sources, just apply Ohm's law to the appropirate impedance (added, since serial) curve and you will undoubtetly notice, it actually reduces the power (and therefore, the spl) by a huge ammount.

Quote:
Originally Posted by oks81 View Post
Second, the doppler effect. If this is an big issue, how about 6,5" and 8" thats more normally used in hifi speakers? Their freq range often about 30-2khz?
It's not (only) about the Doppler effect. It's about the intermodulation distortion! Yes, a 15" driver will have lower intermodulation distortion than a 6" or 8". But that's ONLY if it does a lower excursion. That means, if the 15" does the same excursion in the midrange like a 6" or a 8", it will have the same intermodulation distortion. And yes, that includes the lower beamwidth of the 15" already.

Quote:
Originally Posted by oks81 View Post
I don`t say it is an easy job for an 15" to play up to 1khz.
But you have to look at the real issues. Cone break up. Intermodulation in motor. Suspension. How much mms do it need, preferably light for the upper range.
YES! Exactly that! With that much of an excursion, the intermodulation will NOT allow a precise midrange signal reproduction! Excursion is the key since the intermodulation distortion is directly dependent on it! That means, a midrange capable driver cannot exceed a certain excursion since it would introduce a huge distortion! Look at midrange-able drivers of P-Audio, RCF or whatever brand you'd like, you'll find that (after calculating ((winding height-pole plate height)/2) the max linear excursion of midrange-able15" drivers are ~3,5mm. Give or take some for the drivers manufacturers cacluclation, but you'll find there are none of high excursion drivers among them. The reason is easy to determine, above that excursion the distortion gets too high to reproduce any reasonable midrange.


Quote:
Originally Posted by oks81 View Post
On the other hand there has been build 15" for long time that do this job quite good.
TAD 2402 monitor. JBL Everest series. JBL K2. JBL M2 and so on.
In the K2 the 15" is crossed at 900hz. I don`t see much complaints about these kind of speakers all having 15" crossed in the 7-900hz region.
YES! But none of it do an excursion of 12mm! Actually, you'll find, they'll do no more than 3-4mm!
__________________
I had a Déjà Moo - I've seen that BS before!
  Reply With Quote
Old 19th September 2019, 11:13 PM   #68
Demonkleaner is offline Demonkleaner  United States
diyAudio Member
 
Demonkleaner's Avatar
 
Join Date: Jan 2012
Location: Charleston WV
https://www.parts-express.com/pedocs...spec-sheet.pdf
__________________
These pretzels are making me thirsty.--Kosmo
  Reply With Quote
Old 20th September 2019, 12:26 PM   #69
phase_accurate is offline phase_accurate
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
Quote:
Well, mo matter if he says that, physics say otherwise.
I and the physics still say that. You should not take things out of context. The discussion back then was about the upper corner frequency caused by Lvc and Re.

Quote:
That is the exact reason why double coil drivers are actually NOT used in the midrange.
There are enough exaples to prove the contrary. For instance all those Studio and PA Woofers for two way systems by JBL.

Eighteensound for instance has two new tetracoil models aimed at two way applications. An interesting statment from them is:

"Dual gap motors linearize inductance and the perfect balance we reached between the motor and the ultra linear suspension allows both very high excursion and extreme precision in the mid band with the lowest intermodulation distortion in the professional market."

I also think that you completely misunderstood the intention behind that design. It is meant to lower nonlinear distortion by needing less excursion than a smaller driver for a given SPL and not for being used to reach disco levels. Personally I could do with 5mm of x-max. Which would also be sufficient for most users. His intention is to have a driver that still has some marging left when excurions in the 5 mm or whatever order are reached. How much benefit this will have I don't know.

But there is definitley a lack of affordable 15" studio woofers at the moment. But there are some Faital and Beyma Drivers (and others of Course) that are already close to studio woofers and which would probably only need minor changes in order to be considered as one. I guess one would also have to order 100 pieces or more to have them customise one of their existing models.

Regards

Charles
  Reply With Quote
Old 20th September 2019, 01:37 PM   #70
oks81 is offline oks81  Norway
diyAudio Member
 
Join Date: Jul 2014
1: I answered about VC serial/parallel in the matter of t/s, not the amp that is connected Yes I know ohms law.

2: I answered to the doppler effect, not intermodulation.

3: The intermodulation in the driver I will leave to Snickers to explain and what he has done in the motor to lower this. Keywords: Saturated VC gap, high flux, single layer VC.

4: Yes I know how to calculate Xmax. Yes I know much of the existing drivers have short Xmax. This driver have 12mm Xmax because it can, and not because it`s nessesary to use it to Xmax.

5: Several drivers have dual VC and works fine in midrange.

Try at least to listen to the moo and understand it, not moo against it.
__________________
  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 03:29 PM.


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