TH 15" flat response to 35Hz (-3dB) - By LORDSANSUI - Page 2 - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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 8th November 2016, 02:36 PM   #11
diyAudio Member
 
Join Date: Sep 2016
Xoc1,

Should I redo all parametric fold and unfold sketch to do it or I can change just the areas as you indicated? I think just changing that areas it will create the effect indicated below. The path length will increase but at the cost of add restriction.

The compression ratio was my mistake "reading" once I was sleepy. But talking about it, using under 800W power, do you think a CR 3:1 would be a problem for not special cone made driver?

Click the image to open in full size.
  Reply With Quote
Old 8th November 2016, 03:37 PM   #12
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by Xoc1 View Post
As for the cone compensation, I would not recommend the extra timber as it reduces volume and increases weight.
Agreed.


Quote:
Originally Posted by Xoc1 View Post
The cone correction is not to increase the compression ratio. It makes the ratio correct to your sim, therefore increasing the accuracy.
Exactly. To address it, you either have to

(1) adjust the sim to take cone correction into consideration (usually done by setting Atc~Sd and increasing Vtc to account for the extra volume of air that sits between the cone and the entrance to the horn @S2), or

(2) modify the layout of the horn @S2 to compensate for that volume
__________________
www.diysubwoofers.org
  Reply With Quote
Old 8th November 2016, 07:57 PM   #13
diyAudio Member
 
Join Date: Sep 2016
The cone correction and bracing will be the final part, together with plan.

Some feedbacks regarding hornresp cone displacement accuracy will help me a lot to conclude this project, I ready a lot of posting telling that the simulation show higher displacement than reality.

The second point is about compression ratio for common cone material, 15" drive can manage 800W with compression ratio 3:1 ?

Regarding those two doubts I prepared a third proposal (C). The compression ratio was increased from 2:1 to 3:1, first horn expansion was increased from 3 degrees to 4,5 degrees and the 2nd expansion increased to 32 degrees. As a results the SPL rise and cone displacement reduces. The price was loosing some low frequency as a trade off.

Click the image to open in full size.
  Reply With Quote
Old 8th November 2016, 09:54 PM   #14
diyAudio Member
 
Join Date: May 2006
Quote:
Originally Posted by LORDSANSUI View Post
The cone correction and bracing will be the final part, together with plan.
Why? All you have to do is fill in Vtc and Atc and the sim will be as accurate as it's going to get. You could probably even get the cone shape correct by using Ap1 and Lp if you want to get as accurate as possible. I haven't actually tried this but it looks like to could be used to accurate describe the cone shape. Either way, it's pure negligence no not fill in Vtc and Atc. In most cases it doesn't matter much but if this is something you are actually thinking of building you should definitely have the throat chamber included in the sim.

Quote:
Some feedbacks regarding hornresp cone displacement accuracy will help me a lot to conclude this project, I ready a lot of posting telling that the simulation show higher displacement than reality.
Unless you can measure cone excursion accurately I wouldn't worry about it. Even if you could I don't think Hornresp's predictions are going to be off by much. We all use Hornresp's predictions as the best guess we have.

Quote:
The second point is about compression ratio for common cone material, 15" drive can manage 800W with compression ratio 3:1 ?
You can look at pressure in Hornresp. Then you can compare that with pressure in other similar simulated designs with similar drivers. If the compared design is well vetted and known to be ok with the pressures then your design will likely also be ok.

Quote:
Regarding those two doubts I prepared a third proposal (C). The compression ratio was increased from 2:1 to 3:1, first horn expansion was increased from 3 degrees to 4,5 degrees and the 2nd expansion increased to 32 degrees. As a results the SPL rise and cone displacement reduces. The price was loosing some low frequency as a trade off.
Look at the pressure on the cone at xmax with all 3 proposals in Hornresp. I'm not sure why you ask for opinions about this stuff when you can just look in Hornresp and it will show very clearly how much pressure each design puts on the cone. Make sure you check at xmax, not at 1 watt.

Speaking of 1 watt, I'm pretty sure your 1 watt sims are still not 1 watt. I told you before not to sim everything at 2.83V, this is VERY different than 1 watt unless the speaker's Re is exactly 8 ohms.

Last edited by just a guy; 8th November 2016 at 09:58 PM.
  Reply With Quote
Old 8th November 2016, 10:22 PM   #15
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by just a guy View Post
Speaking of 1 watt, I'm pretty sure your 1 watt sims are still not 1 watt. I told you before not to sim everything at 2.83V, this is VERY different than 1 watt unless the speaker's Re is exactly 8 ohms.

The only point I disagree with. All that you'd be accomplishing with this is having HornResp sim the efficiency of your sim referenced to the driver Re, not its sensitivity. As basically all pro audio amplifiers these days can meet or exceed their 8 ohm ratings at lower impedances, the sensitivity rating is more important and certainly more indicative of the output you can actually achieve with your build.
__________________
www.diysubwoofers.org
  Reply With Quote
Old 8th November 2016, 10:25 PM   #16
diyAudio Member
 
Join Date: Sep 2016
Quote:
Originally Posted by just a guy View Post
Why? All you have to do is fill in Vtc and Atc
Each cab has different geometry so I can do this at the end, with cone correction added there is no reason to add Vtc/Atc.

Quote:
Originally Posted by just a guy View Post
You can look at pressure in Hornresp. Then you can compare that with pressure in other similar simulated designs with similar drivers. If the compared design is well vetted and known to be ok with the pressures then your design will likely also be ok.
I could do it for sure but I don't have database available to compare with, so this is the reason I'm asking for help. The only one information I have close to this one is the SS16 with eminence drive but it's just 450 W and the compression ratio is 1,79

Quote:
Originally Posted by just a guy View Post
Look at the pressure on the cone at xmax with all 3 proposals in Hornresp
Without cone material specification on hand it's worthless to look at numbers. Some guys here have more experience building cabs than my age and this helps a lot.

I know 2.83V is not 1 watt, but sometimes we are lazy and the major part of the people use it as 1 W wrongly, so you can cover your eyes for this :P
  Reply With Quote
Old 8th November 2016, 11:51 PM   #17
diyAudio Member
 
Join Date: May 2006
Quote:
Originally Posted by Brian Steele View Post
The only point I disagree with. All that you'd be accomplishing with this is having HornResp sim the efficiency of your sim referenced to the driver Re, not its sensitivity. As basically all pro audio amplifiers these days can meet or exceed their 8 ohm ratings at lower impedances, the sensitivity rating is more important and certainly more indicative of the output you can actually achieve with your build.
If the intent is to see how they compare with equal power (which is almost always the intent when someone simulates everything at 2.83V), then the intent has not been satisfied because they are not comparing equal power.

In this case specifically I KNOW he intended to sim at equal power because he specifically said all the sims were shown at 1 watt, but that isn't true, they were shown at 2.83V so none of them were actually shown at 1 watt.
  Reply With Quote
Old 9th November 2016, 03:28 AM   #18
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by just a guy View Post
If the intent is to see how they compare with equal power
"Equal power" is a myth. The system's impedance VARIES with frequency. This is true for basically EVERY subwoofer system. So setting a "1 Watt" voltage without a reference frequency in reality makes absolutely no sense. And lets not forget too that there's a pretty good chance that the impedance of the subwoofer through its operating range will never hit as low as Re, so using Re as a the reference impedance for "1 Watt" may likely be incorrect too. Now, if you were to say "1 Watt" at a specific frequency, then that gets a little better, but who measures subwoofers based on their 1 Watt output at a specific frequency?

Secondly, I'd love to hear if anyone has ever seen a pro audio amplifier where the gain is set in terms of output wattage instead of output voltage, particularly considering that the output wattage will be based on the load's impedance and the output voltage will not be. Basically all pro audio amps can be considered as voltage sources once the load is above their minimum rated impedance.

In summary, comparing alignments based on an arbitrary "1 Watt" that's basically determined at what voltage is required to produce 1 Watt across the driver's Re simply makes no sense when the real-world use of these alignments is taken into consideration.
__________________
www.diysubwoofers.org
  Reply With Quote
Old 9th November 2016, 05:57 AM   #19
diyAudio Member
 
Join Date: May 2006
Quote:
Originally Posted by Brian Steele View Post
"Equal power" is a myth.

...
Sure the impedance curve is a roller coaster. But the intent of putting a sensitivity rating on a sub is to compare to other products. And the intent in trying to compare different designs in sims at "1 watt" or 2.83 volts is to compare to other designs.

Comparing at a single frequency doesn't make any sense.
Comparing every product at the same voltage doesn't make any sense.

So how can you compare?

You can take the minimum impedance in the passband, reference your voltage to that impedance and call it "1 watt". It's not 1 watt everywhere in the passband but it's as close as you can possibly get to an equal power equivalency test.

I'll say it again - for an equivalency comparison, comparing everything at 2.83V makes absolutely no sense at all, that makes things decidedly unequivalent. The most equivalent power level you can possible hope for is voltage based on watts referenced to minimum impedance in the passband.

A better way to compare would be frequency response at max spl, but that comparison is not small signal so it's fraught with complication.
  Reply With Quote
Old 9th November 2016, 06:15 AM   #20
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by just a guy View Post
Comparing every product at the same voltage doesn't make any sense.
Yes it does. And that's why basically every audio company quotes a 2.83V reference for their speaker products. It takes literally seconds with a voltmeter to check the output voltage from an amp to confirm that it's 2.83V. And amplifier gain is adjusted by Volts, NOT Watts. I don't have to sit down and work out what voltage I have to set the amplifier to in order to meet your "1 Watt" reference, which apparently has now been changed, by your subsequent note below, LOL. So which should I use now - Re, or measured minimum impedance in the passband?


Quote:
Originally Posted by just a guy View Post
You can take the minimum impedance in the passband, reference your voltage to that impedance and call it "1 watt". It's not 1 watt everywhere in the passband but it's as close as you can possibly get to an equal power equivalency test.
... which now requires taking an impedance response curve and reading off Rmin, then using that to calculate what "1 Watt" would be at that frequency (and that frequency alone, because impedance will be different at every other frequency) rather than simply setting the voltage at the amp to 2.83 V. How is that more sensible as a reference?
__________________
www.diysubwoofers.org
  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
TH-18 Flat to 35hz! (Xoc1's design) m R g S r Subwoofers 2530 26th May 2017 12:59 PM
OTH40C 15" loaded Compact TH Flat to 40hz sine143 Subwoofers 68 30th October 2016 02:46 AM
Flat FR, Flat Power Response, in-phase crossover? RockLeeEV Multi-Way 15 7th February 2012 08:07 PM
DCGold fullrange cones 35hz -3db @96db sensitivity?? human.bin Full Range 20 26th February 2010 01:34 PM


New To Site? Need Help?

All times are GMT. The time now is 06:21 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki