EXPERIMENTAL Quad JBL Devastator Build - Page 3 - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 389Likes
Reply
 
Thread Tools
post #61 of 446 Old 02-06-2020, 01:16 PM
AVS Forum Special Member
 
BP1Fanatic's Avatar
 
Join Date: Jan 2010
Location: Columbus, Oh
Posts: 1,186
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 432 Post(s)
Liked: 406
Cool

Quote:
Originally Posted by mtg90 View Post
What does the excursion of this design look like in the 20-30hz range?

The response of this design looks very similar to the Quad GRS 10" 6th order series tuned bandpass sub I built a little while back. One of the main issues with that design was that the peak in the response (~105-110hz on mine) caused an amplification of the driver 3rd and 4th order harmonics in the 25-35hz range which just happened to coincide with the excursion maximum where such distortion was most prevalent.

The JBL's are likely cleaner but I'd watch for the same kind of rise in distortion in the 20-30hz range.

Edit: looked at my measurements again and it was just the 3rd order harmonics that got boosted.
I've been playing around with dual GRS 12SW4's in BP4 in HR. I tried the BP6's, but the graphs were ugly.

Sony XBR65x900e / STR-DN1080 / original PS4 / WOW! Ultra TV / Quantum Access Mini PC Stick w/Windows 10 / 8 x Rockville SPG88 8“ DJ PA Speakers / Dayton Audio SA1000 / Kicker 08S15L74 in a Tapped-Tapered Quarter Wave Tube (negative flare tapped horn).
BP1Fanatic is online now  
Sponsored Links
Advertisement
 
post #62 of 446 Old 02-06-2020, 01:19 PM
AVS Forum Special Member
 
BP1Fanatic's Avatar
 
Join Date: Jan 2010
Location: Columbus, Oh
Posts: 1,186
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 432 Post(s)
Liked: 406
Thumbs up

Quote:
Originally Posted by Ricci View Post
Here are the measured specs from Chris's impedance files with the semi inductance. Doesn't radically change things from the basic factory specs but it does change the models. I'm a little skeptical of that SD figure. Seems high.


If I get some time maybe I'll give a shot at modeling this cab with the drivers separated inside of Akabak just to have a look. Haven't had an excuse to use Akabak in a long time.


What's the internal height of the ports and the depth inside from the front panel to the driver baffle?

Sd=551.00
Bl=12.39
Cms=1.63E-04
Rms=7.86
Mmd=153.97
Le=2.75
Re=3.31
Leb=0.74
Le=5.97
Ke=0.29
Rss=507.10
Rms=4.16
Ams=1.69E-05
I see you made it over from diyaudio.com!

Sony XBR65x900e / STR-DN1080 / original PS4 / WOW! Ultra TV / Quantum Access Mini PC Stick w/Windows 10 / 8 x Rockville SPG88 8“ DJ PA Speakers / Dayton Audio SA1000 / Kicker 08S15L74 in a Tapped-Tapered Quarter Wave Tube (negative flare tapped horn).
BP1Fanatic is online now  
post #63 of 446 Old 02-06-2020, 02:36 PM
AVS Forum Special Member
 
zeus33's Avatar
 
Join Date: Dec 2012
Posts: 4,426
Mentioned: 17 Post(s)
Tagged: 0 Thread(s)
Quoted: 1996 Post(s)
Liked: 2275
Quote:
Originally Posted by BP1Fanatic View Post
I see you made it over from diyaudio.com!

Josh always pops in from time to time with very helpful info.
EndersShadow likes this.
zeus33 is online now  
Sponsored Links
Advertisement
 
post #64 of 446 Old 02-06-2020, 08:39 PM - Thread Starter
AVS Forum Special Member
 
a77cj7's Avatar
 
Join Date: Aug 2019
Location: Sturgis, SD
Posts: 1,911
Mentioned: 70 Post(s)
Tagged: 0 Thread(s)
Quoted: 1020 Post(s)
Liked: 1071
Sadly I had some other stuff to take care of tonight, so just a few teaser pics:

This looks promising:


They’re here! A day early too!


Test cart assembly:


I’m off work tomorrow, so this is priority one. I’ll get the test cart working and break the drivers in a bit free-air.

Bad news, it is currently snowing, so ground plane is probably a no-go. Hopefully close-mic will tell us enough. Along with some demo material of course.

Chris
a77cj7 is online now  
post #65 of 446 Old 02-06-2020, 10:02 PM
Advanced Member
 
Chris Popovich's Avatar
 
Join Date: Dec 2005
Location: Phoenix AZ
Posts: 806
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 385 Post(s)
Liked: 365
You're an animal. A savage animal.

I'm glad you're not very close to me. We would definitely get into a lot of trouble.
BP1Fanatic, Nalleh and a77cj7 like this.
Chris Popovich is offline  
post #66 of 446 Old 02-06-2020, 11:49 PM
AVS Forum Special Member
 
Nalleh's Avatar
 
Join Date: Aug 2014
Location: Norway
Posts: 4,811
Mentioned: 501 Post(s)
Tagged: 0 Thread(s)
Quoted: 3288 Post(s)
Liked: 5108
^^^ The AWSOME factor is off the charts on this one !!!!

We are close to getting answers on this project, so cool
a77cj7 likes this.

Dual AVR 13.1.8 SWAtmos - Atmos 13.1.8/DTS X 9.1.8/Auro 3D 13.1 - Denon AVCX8500H+AVRX7200WA - Klipsch+KEF - 4xSI18" - 12x12" w/6xSLAPS M12 VNF - 4x12"HB+2x18"CLHB - 6x Crowsons - 4xBK-LFE - 2x12"BB - 2x "4DX" fans- 6xNU6K - Minidsp 10x10HD-Vertex2-Oppo UDP203-XB1X-ATV4K-JVC RS600-Dreamscreen V2 120"-Samsung QE82Q60.
>>>>Nalleh’s HT<<<<
Nalleh is online now  
post #67 of 446 Old 02-06-2020, 11:59 PM
AVS Forum Special Member
 
Join Date: Aug 2018
Location: Sonoma County, CA
Posts: 3,578
Mentioned: 50 Post(s)
Tagged: 0 Thread(s)
Quoted: 2094 Post(s)
Liked: 1719
It’s like Christmas, but for everyone who isn’t even getting one of these “presents”.

a77cj7 likes this.

Leave it at 8 ohms and call it a day :)
Russdawg1 is online now  
post #68 of 446 Old 02-07-2020, 01:15 AM
AVS Forum Special Member
 
BP1Fanatic's Avatar
 
Join Date: Jan 2010
Location: Columbus, Oh
Posts: 1,186
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 432 Post(s)
Liked: 406
Thumbs up

Quote:
Originally Posted by zeus33 View Post
Josh always pops in from time to time with very helpful info.
I know! I follow his builds too! Josh Ricci is a subwoofer designing monster! I've been registered to the data-bass forum for some years too. I might have posted once or twice.

Sony XBR65x900e / STR-DN1080 / original PS4 / WOW! Ultra TV / Quantum Access Mini PC Stick w/Windows 10 / 8 x Rockville SPG88 8“ DJ PA Speakers / Dayton Audio SA1000 / Kicker 08S15L74 in a Tapped-Tapered Quarter Wave Tube (negative flare tapped horn).
BP1Fanatic is online now  
post #69 of 446 Old 02-07-2020, 01:44 AM
AVS Forum Special Member
 
BP1Fanatic's Avatar
 
Join Date: Jan 2010
Location: Columbus, Oh
Posts: 1,186
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 432 Post(s)
Liked: 406
Question

Quote:
Originally Posted by mtg90 View Post
So harmonics occur at multiples of the fundamental frequency, 2nd order occurs at 2x the fundamental, 3rd order at 3x and so on. So if your subwoofer is playing a 30hz tone the 3rd order harmonic will occur at 90hz. EQ does not reduce the level of the harmonics since they are generated off the fundamental frequency.

For this Quad JBL devastator design the peak in response looks like it occurs around 87Hz, the 3rd order harmonic that will land on that peak is then generated by a 29Hz signal. 29Hz looks to be about 8dB lower then the response at 87Hz which means that 3rd order harmonic will have an 8dB head start over the fundamental (nearly double the distortion %). The excursion maximum where 3rd order distortion will be most prevalent also occurs near that range so you end up with a double whammy.

Another example of where this can occur is on woofer or midrange drivers with a large cone breakup peak, any harmonics that land on that peak are amplified by it. So you would want to crossover at least 2-3x lower then the peak to prevent spikes in 2nd or 3rd harmonic distortion.

A driver or enclosure design that can maintain a smooth flat frequency response will then be free of any of those harmonic distortion amplifying properties.
1. Why does it matter what happens at 87hz when most of us would have a 12db low pass filter at 80hz for home theater?

2. I thought the original Devastator was designed for more mid bass (60-80hz) due to BP6's flat responses in a room adds too much sub bass (20-40hz)?

I designed my negative flare tapped horn for flat response. I originally had it firing into the corner. The SPL was great! When I turned the enclosure 180*, more mid bass kicked in and sounds better to my ears.

Pic 1 = 2013 firing into corner.
Pic 2 = 2019 firing away from corner.
Attached Thumbnails
Click image for larger version

Name:	My HTS 1.jpg
Views:	157
Size:	19.5 KB
ID:	2681574   Click image for larger version

Name:	20190215_214555.jpg
Views:	160
Size:	727.0 KB
ID:	2681576  

Sony XBR65x900e / STR-DN1080 / original PS4 / WOW! Ultra TV / Quantum Access Mini PC Stick w/Windows 10 / 8 x Rockville SPG88 8“ DJ PA Speakers / Dayton Audio SA1000 / Kicker 08S15L74 in a Tapped-Tapered Quarter Wave Tube (negative flare tapped horn).
BP1Fanatic is online now  
post #70 of 446 Old 02-07-2020, 04:58 AM
Member
 
Heide264's Avatar
 
Join Date: Oct 2011
Posts: 171
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 69 Post(s)
Liked: 39
Quote:
Originally Posted by BP1Fanatic View Post
1. Why does it matter what happens at 87hz when most of us would have a 12db low pass filter at 80hz for home theater?
You aren't sending 87Hz to the sub if it's harmonic distortion. You are sending 29Hz. The sub itself creates the harmonic output. Your crossover is in the signal chain. The 87Hz distortion is created during output.

Can't EQ/filter anything that isn't there to begin with.
jcr159 and a77cj7 like this.
Heide264 is offline  
post #71 of 446 Old 02-07-2020, 06:55 AM - Thread Starter
AVS Forum Special Member
 
a77cj7's Avatar
 
Join Date: Aug 2019
Location: Sturgis, SD
Posts: 1,911
Mentioned: 70 Post(s)
Tagged: 0 Thread(s)
Quoted: 1020 Post(s)
Liked: 1071
EXPERIMENTAL Quad JBL Devastator Build

Quote:
Originally Posted by BP1Fanatic View Post
1. Why does it matter what happens at 87hz when most of us would have a 12db low pass filter at 80hz for home theater?


Not applicable here, as @Heide264 explained, but...

You also have to remember that crossovers are not hard cutoffs, but slopes. With a standard 12db BW at 80hz, you’re only down about 4db at 87hz.
This is why rule-of-thumb is to keep the first port resonance one octave above crossover frequency. Many of us push that down to 130hz or so for an 80hz crossover on the low-tuned designs, but not ideal.

Chris
Chris Popovich likes this.

Last edited by a77cj7; 02-07-2020 at 07:29 AM.
a77cj7 is online now  
post #72 of 446 Old 02-07-2020, 09:49 AM - Thread Starter
AVS Forum Special Member
 
a77cj7's Avatar
 
Join Date: Aug 2019
Location: Sturgis, SD
Posts: 1,911
Mentioned: 70 Post(s)
Tagged: 0 Thread(s)
Quoted: 1020 Post(s)
Liked: 1071
Test cart is live and working with control woofer:


Time to break in some jbl’s!

Chris
a77cj7 is online now  
post #73 of 446 Old 02-07-2020, 11:26 AM
AVS Forum Special Member
 
asarose247's Avatar
 
Join Date: Mar 2010
Location: DIY enabled in SoCal / OC
Posts: 4,700
Mentioned: 118 Post(s)
Tagged: 2 Thread(s)
Quoted: 1340 Post(s)
Liked: 1177
^

intimations of omnipotence



LIGHT IT UP!

DIY FAN Denon X4400 , ATI A 2000 for 7.4.6 SCATMOS Sammy 82" 4K/HDR
L/R: Fusion 15 V2 , C: 88 Special , SL/SR: 88 Special(V2) , RL/RR: F-3, TF/TR: Volt 6's TM: SLX, FH: F4Q4
SUBMAXIMUS V2, ,Submaximus V3,LOWARHORNCustom Dual Driver VBSS,2 x 6000DSP
asarose247 is online now  
post #74 of 446 Old 02-07-2020, 01:47 PM
Senior Member
 
MTBDOC's Avatar
 
Join Date: Oct 2007
Posts: 350
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 162 Post(s)
Liked: 109
Cool! This is a little bit like watching a child open my Christmas gift, it is fun being part of this (even if only in the simplest way, a few keystrokes to buy drivers). Chris, your investment of time, material, and expertise in this experiment is great. It is strange being on this side of things, I have always been a 'doer' rather than an observer.


I think that my contribution to the JBL 12" story may be a 4 driver / 2 PR sub, not just randomly thrown together, but with thought-out parameters of cabinet size & PR mass. Just got WinISD running under Wine, still trying to figure out what driver specs to use.


Eagerly awaiting some numbers (on the Dev4x12). BTW, it is sunny but cold down here in AL ... definitely no snow

Last edited by MTBDOC; 02-07-2020 at 01:57 PM.
MTBDOC is offline  
post #75 of 446 Old 02-07-2020, 02:35 PM
AVS Forum Special Member
 
Ricci's Avatar
 
Join Date: Mar 2007
Location: Louisville KY
Posts: 5,539
Mentioned: 195 Post(s)
Tagged: 0 Thread(s)
Quoted: 423 Post(s)
Liked: 974
Ok...Sorry for not following up here but I've been busy.


Finally had a chance to fire up Akabak and run this cab real quick. No inductance modeling on this. It's like I suspected. Driver excursion behavior looks nasty unless all of the drivers are wired in parallel. There is still some uneven behavior with them in parallel but it looks much better. Anything involving series driver wiring appears to cause things to go awry at least according to Akabak.
Wish I had better news.


Teal is the HR type sim with the drivers sim'd at the midpoint between the physical locations.
Green and black curves are the FR with the driver pairs sim'd at their separate physical locations. Black is with parallel drivers and green with series/parallel









Cone excursion with the HR type sim with the driver placement averaged.









This is with all drivers wired in parallel and modeled with the driver pairs separated locations. Not too bad.









Here is with the drivers wired in series / parallel. Ugh oh...All drivers in series looks the same.









That's all I have time to post now. Gotta run.
Attached Thumbnails
Click image for larger version

Name:	DEV4x12 Akabak FR Comparison.jpg
Views:	655
Size:	99.5 KB
ID:	2681830   Click image for larger version

Name:	DEV4x12 cone excursion AK model.png
Views:	503
Size:	117.8 KB
ID:	2681832   Click image for larger version

Name:	DEV4x12 cone excursion AK model series.png
Views:	515
Size:	119.1 KB
ID:	2681834   Click image for larger version

Name:	DEV4x12 cone excursion HR model.png
Views:	517
Size:	109.0 KB
ID:	2681838  
OJ Bartley and Nalleh like this.
Ricci is offline  
post #76 of 446 Old 02-07-2020, 02:53 PM
Senior Member
 
MTBDOC's Avatar
 
Join Date: Oct 2007
Posts: 350
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 162 Post(s)
Liked: 109
Interesting graphs, wondering about how different wiring patterns might work, such as vertical vs horizontal pairs run as two separate channels. Then, if one were running two Devs (8 drivers) what happens with 2 lower & 2 upper drivers wired in parallel, then run in series with the second Dev. That would give all the drivers seeing the same relative position in the horn the same circuit. Wiring would be a little bit of fun, but honestly it wouldn't be that big of a deal, especially if they were located on the same wall.


Hmmm ... might need to get playing on a tuned PR box!


A funny observation from the pics: 2 pairs of drivers ordered at the same time ( I think) and yet 2 different "models"!
MTBDOC is offline  
post #77 of 446 Old 02-07-2020, 03:21 PM - Thread Starter
AVS Forum Special Member
 
a77cj7's Avatar
 
Join Date: Aug 2019
Location: Sturgis, SD
Posts: 1,911
Mentioned: 70 Post(s)
Tagged: 0 Thread(s)
Quoted: 1020 Post(s)
Liked: 1071
EXPERIMENTAL Quad JBL Devastator Build

Finally ready to fire this thing up.

And I check in here to see that Josh has posted the models. Huge thanks @Ricci !

It looks to me like the response curve is generally unaffected in the operating range. Diaphragm displacement isn’t pretty, but could be worse. Too bad these are 4 ohm drivers, and I don’t have a 1ohm stable amplifier.

Two questions Josh.
First, how much power does it take to hit 15mm excursion series/parallel?
EDIT: With a 19hz 2nd order BW HPF.

Second, could I sidestep this issue by running two sets of parallel driver pairs on identical amplifier channels, instead of running one bridged channel?

EDIT: Third question, does it matter which drivers are series, and which are parallel? I assume not if all-series looks similar. I have them wired series with horn path, parallel across horn path.

Close mic response should be posted shortly!

Thanks,
Chris
brettus and Nalleh like this.

Last edited by a77cj7; 02-07-2020 at 03:36 PM.
a77cj7 is online now  
post #78 of 446 Old 02-07-2020, 03:58 PM - Thread Starter
AVS Forum Special Member
 
a77cj7's Avatar
 
Join Date: Aug 2019
Location: Sturgis, SD
Posts: 1,911
Mentioned: 70 Post(s)
Tagged: 0 Thread(s)
Quoted: 1020 Post(s)
Liked: 1071
And here’s the close-mic:


Blue: Measurement
Green: HR sim factory specs
orange: HR sim ChrisP/Josh semi inductance

Chris
a77cj7 is online now  
post #79 of 446 Old 02-07-2020, 04:25 PM - Thread Starter
AVS Forum Special Member
 
a77cj7's Avatar
 
Join Date: Aug 2019
Location: Sturgis, SD
Posts: 1,911
Mentioned: 70 Post(s)
Tagged: 0 Thread(s)
Quoted: 1020 Post(s)
Liked: 1071
This sub has some potential. I’m nervous due to Josh’s excursion sim, but know the BOSS guys have proven these drivers to be quite durable.

So I cranked it up a bit. It has the “devastator sound”, and is more usable without EQ than my mini’s are.
I was trying to listen for driver distress, but didn’t hear anything.
It is fully capable of rattling all the sheetmetal in my shop: the main door, ductwork, and ceiling were all buzzing severely.
The air velocity in the horn opening is impressive. I don’t remember that kind of velocity from the mini’s. Due to the higher compression ratio possibly?

It has way more output than the “control sub”, a PA460 tuned to 27hz in 3.5cf.

I’ll get some ground plane measurements tomorrow if the wind cooperates.
Hopefully, setting the quad just outside my shop door will work. I don’t have the ability to get if to the middle of a field.

I’ll definitely have to get it inside for a side-by-side with a mini devastator.

Chris
a77cj7 is online now  
post #80 of 446 Old 02-07-2020, 04:30 PM
Advanced Member
 
jcr159's Avatar
 
Join Date: Dec 2007
Location: NE Ohio (Go Steelers!)
Posts: 583
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 274 Post(s)
Liked: 144
Impressive work, thanks for all you guys do for the community

Have a question and want it answered in podcast format?
[email protected]
http://www.avrant.com/
https://www.youtube.com/c/avrant
jcr159 is online now  
post #81 of 446 Old 02-07-2020, 04:38 PM - Thread Starter
AVS Forum Special Member
 
a77cj7's Avatar
 
Join Date: Aug 2019
Location: Sturgis, SD
Posts: 1,911
Mentioned: 70 Post(s)
Tagged: 0 Thread(s)
Quoted: 1020 Post(s)
Liked: 1071
EXPERIMENTAL Quad JBL Devastator Build

Quote:
Originally Posted by MTBDOC View Post
Interesting graphs, wondering about how different wiring patterns might work, such as vertical vs horizontal pairs run as two separate channels. Then, if one were running two Devs (8 drivers) what happens with 2 lower & 2 upper drivers wired in parallel, then run in series with the second Dev. That would give all the drivers seeing the same relative position in the horn the same circuit. Wiring would be a little bit of fun, but honestly it wouldn't be that big of a deal, especially if they were located on the same wall.


Hmmm ... might need to get playing on a tuned PR box!


A funny observation from the pics: 2 pairs of drivers ordered at the same time ( I think) and yet 2 different "models"!


Lol, missed your post earlier. I see you had the same thought I did on splitting it into two channels.

As for wiring multiple cabs, run all drivers parallel for 1ohm. Then series two cabs, 2 ohm load. One channel of a nx3000d will run that nicely.
That leaves an open channel though, better add two more.
Four of these would be very serious output, might just give 8 VBSS a run for the $.

EDIT: As for the two different “models” of drivers, the CS1214’s were ordered from amazon, while the gx1200’s were sent by @gpmbc .

Chris

Last edited by a77cj7; 02-07-2020 at 04:48 PM.
a77cj7 is online now  
post #82 of 446 Old 02-07-2020, 05:09 PM - Thread Starter
AVS Forum Special Member
 
a77cj7's Avatar
 
Join Date: Aug 2019
Location: Sturgis, SD
Posts: 1,911
Mentioned: 70 Post(s)
Tagged: 0 Thread(s)
Quoted: 1020 Post(s)
Liked: 1071
Main posts are updated

Chris
Chris Popovich likes this.
a77cj7 is online now  
post #83 of 446 Old 02-07-2020, 05:44 PM
AVS Forum Special Member
 
gpmbc's Avatar
 
Join Date: Jun 2006
Location: AZ
Posts: 3,151
Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 459 Post(s)
Liked: 373
Looks good so far!
gpmbc is online now  
post #84 of 446 Old 02-07-2020, 05:50 PM
AVS Forum Special Member
 
Nalleh's Avatar
 
Join Date: Aug 2014
Location: Norway
Posts: 4,811
Mentioned: 501 Post(s)
Tagged: 0 Thread(s)
Quoted: 3288 Post(s)
Liked: 5108
WOW!! This is so cool! So far it seems it measured pretty well according to sim!
It defenitely need a comparison, so get it into your HT and compare to your mini dev

Awsome work, thanks so much

Dual AVR 13.1.8 SWAtmos - Atmos 13.1.8/DTS X 9.1.8/Auro 3D 13.1 - Denon AVCX8500H+AVRX7200WA - Klipsch+KEF - 4xSI18" - 12x12" w/6xSLAPS M12 VNF - 4x12"HB+2x18"CLHB - 6x Crowsons - 4xBK-LFE - 2x12"BB - 2x "4DX" fans- 6xNU6K - Minidsp 10x10HD-Vertex2-Oppo UDP203-XB1X-ATV4K-JVC RS600-Dreamscreen V2 120"-Samsung QE82Q60.
>>>>Nalleh’s HT<<<<
Nalleh is online now  
post #85 of 446 Old 02-07-2020, 06:46 PM
Member
 
DigiWega's Avatar
 
Join Date: Feb 2003
Posts: 124
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 71 Post(s)
Liked: 83
Super impressive results so far Chris. I can't wait to hear and see more. I wish I could send you a virtual six pack.

When do you plan to bring it into your theater for a showdown with the mini's?
DigiWega is online now  
post #86 of 446 Old 02-07-2020, 06:53 PM - Thread Starter
AVS Forum Special Member
 
a77cj7's Avatar
 
Join Date: Aug 2019
Location: Sturgis, SD
Posts: 1,911
Mentioned: 70 Post(s)
Tagged: 0 Thread(s)
Quoted: 1020 Post(s)
Liked: 1071
Quote:
Originally Posted by DigiWega View Post
Super impressive results so far Chris. I can't wait to hear and see more. I wish I could send you a virtual six pack.



When do you plan to bring it into your theater for a showdown with the mini's?

Thanks!

After the ground-plane measurements. So likely tomorrow.
It’ll be on 2500w in the theater, I don’t want to accidentally toast it before getting measurements. I have trouble resisting the urge to turn it up.

Chris
a77cj7 is online now  
post #87 of 446 Old 02-08-2020, 09:40 AM
Senior Member
 
MTBDOC's Avatar
 
Join Date: Oct 2007
Posts: 350
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 162 Post(s)
Liked: 109
How did you decide how much power to use in the measurements last night? If I am following the discussion, the different impedance produces different excursion levels, so there is risk in destroying the driver getting the most juice. So is it the total limit on power input (due to the variable load presented by each driver) the primary problem, and if so, how does one assess individual driver excursion? Simply, is there any way to assess how much output would be lost by running these as a single 4ohm load?


This issue has been quite interesting as I have tried to follow what Ricci has shared... things I had never pondered! I enjoy the intellectual stimulation as well as the practical enjoyment of these toys


And PLEASE, clarify if/when I am missing the boat. Horn subs = new ground for me!
MTBDOC is offline  
post #88 of 446 Old 02-08-2020, 10:11 AM - Thread Starter
AVS Forum Special Member
 
a77cj7's Avatar
 
Join Date: Aug 2019
Location: Sturgis, SD
Posts: 1,911
Mentioned: 70 Post(s)
Tagged: 0 Thread(s)
Quoted: 1020 Post(s)
Liked: 1071
EXPERIMENTAL Quad JBL Devastator Build

Quote:
Originally Posted by MTBDOC View Post
How did you decide how much power to use in the measurements last night? If I am following the discussion, the different impedance produces different excursion levels, so there is risk in destroying the driver getting the most juice. So is it the total limit on power input (due to the variable load presented by each driver) the primary problem, and if so, how does one assess individual driver excursion? Simply, is there any way to assess how much output would be lost by running these as a single 4ohm load?


This issue has been quite interesting as I have tried to follow what Ricci has shared... things I had never pondered! I enjoy the intellectual stimulation as well as the practical enjoyment of these toys


And PLEASE, clarify if/when I am missing the boat. Horn subs = new ground for me!


For close-mic measurements, its really irrelevant. I just turned it up until it was 10db under clipping the mic.
Close-mic takes so little power that its not possible to damage the drivers.

Now when I actually turned it up and demo’d it, there was full possibility of driver damage. I just slowly increased the level while listening for evidence of bottoming out.
This is in no way foolproof, but the BOSS crew has proven these drivers generally survive bottoming out. I decided to take the risk, and didn’t get burned THIS time.

My understanding is not that the drivers are taking additional power, but are exhibiting extra excursion due to the acoustic loading of the horn path. I could be completely off here, this is for @Ricci to answer.
I have detected no coil-smell. My fear is mechanical damage, not thermal.

The amp I’m using has no indication of power level. I’ll try to figure out voltage measurements during the ground-plane sweeps. I am worried about destroying the drivers during that process. And more so in the theater on 2500w.

Don’t get me wrong, I’m not trying to damage the drivers. I would greatly prefer them to survive. But the whole point of this experiment is to determine how this setup performs and if its worth building. I can’t claim to have proven anything without pushing it to the limits.

Horn subs are new ground for many people.
Multi driver horns are new for almost everyone. Tom Danley and Josh Ricci are the only two people I’m aware of that have significant real-world experience with these. This is why I’m grateful Josh is helping out with models and explanations on this one.

Chris
MTBDOC and Daniel Chaves like this.

Last edited by a77cj7; 02-08-2020 at 10:19 AM.
a77cj7 is online now  
post #89 of 446 Old 02-08-2020, 10:25 AM
Senior Member
 
MTBDOC's Avatar
 
Join Date: Oct 2007
Posts: 350
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 162 Post(s)
Liked: 109
Chris, thank you for your quick and thorough response. So what you are saying is localized low pressure areas that extend the driver beyond what the motor is actually driving. Okay, as Josh had talked about the impedance variance, I was thinking that one driver had lower impedance and therefore got more current.



When I graduated with my bachelors degree in ChE (again, back in the Fred & Barney days!) I went to work for Owens-Corning for about 8 months before I went off to med school. It was fascinating to see the interplay between physics & 'black magic' as so much about molten glass flow at 2500deg was purely learned by empiric observation. In one sense, that is how ALL engineering operates: observation => theory => application & measurement which gives us 'the science.' But real-world application never seems to play by the rules. I actually LOVE this as it points to our arrogance, as in each age man convinces himself he has got it all FIGURED OUT! Humility is in such short supply in this present narcissistic age. Ultimately many folks do realize the two basic rules of life: (1) There is a God, and (2) I am NOT Him


So each year as I age I learn more, and recognize more of my own ignorance and shortcomings.
MTBDOC is offline  
post #90 of 446 Old 02-08-2020, 10:52 AM - Thread Starter
AVS Forum Special Member
 
a77cj7's Avatar
 
Join Date: Aug 2019
Location: Sturgis, SD
Posts: 1,911
Mentioned: 70 Post(s)
Tagged: 0 Thread(s)
Quoted: 1020 Post(s)
Liked: 1071
EXPERIMENTAL Quad JBL Devastator Build

Quote:
Originally Posted by MTBDOC View Post
Chris, thank you for your quick and thorough response. So what you are saying is localized low pressure areas that extend the driver beyond what the motor is actually driving. Okay, as Josh had talked about the impedance variance, I was thinking that one driver had lower impedance and therefore got more current.



When I graduated with my bachelors degree in ChE (again, back in the Fred & Barney days!) I went to work for Owens-Corning for about 8 months before I went off to med school. It was fascinating to see the interplay between physics & 'black magic' as so much about molten glass flow at 2500deg was purely learned by empiric observation. In one sense, that is how ALL engineering operates: observation => theory => application & measurement which gives us 'the science.' But real-world application never seems to play by the rules. I actually LOVE this as it points to our arrogance, as in each age man convinces himself he has got it all FIGURED OUT! Humility is in such short supply in this present narcissistic age. Ultimately many folks do realize the two basic rules of life: (1) There is a God, and (2) I am NOT Him


So each year as I age I learn more, and recognize more of my own ignorance and shortcomings.


I hate to elaborate too much, as there is a good chance I have it totally wrong.
I believe that the acoustic loading of the horn path causes variable loading on the drivers at different points along the path, thus exhibiting as variable excursion.
The variable loading will show in the individual impedance curves, so It could well cause power delivery variation.
I don’t understand how parallel vs series wiring effects this, only thing that comes to mind is delay caused by the series connection.

So far, I have no evidence that this thing is playing by the model. I was definitely sending it enough power to bottom drivers. I also have no evidence that it ISN’T playing by the model, which is why I have visions of driver destruction.

I am a Mining Engineer by education, but did start out in EE. The highly theoretical nature of the program caused me to loose interest, my school had much less focus on Power Systems. Its been many years since I used any of it though, so I’m beyond rusty here.

Hey, I’m just supposed to be the buillder/tester here.

Chris
Nalleh likes this.
a77cj7 is online now  
Sponsored Links
Advertisement
 
Reply DIY Speakers and Subs

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

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