CARSOUND.COM Forum

Go Back   CARSOUND.COM Forum > Archived Forums > Richard Clark on Audio
FAQ Members List Calendar Search Today's Posts Mark Forums Read

 
 
Thread Tools Display Modes
Old 09-27-2006, 09:57 PM   #1
Majestik6
Senior Member
 
Majestik6's Avatar
 
Join Date: Sep 2000
Location: Redmond, WA, USA
Posts: 258
Default Twelve Inch Woofers In My Dash

If I had it my way, I'd put twelve inch woofers in my dash. Ten years ago Eric Holdaway let me listen to Harry Kimura's car, and I was *hooked*. Ever since then I've used BIG midranges, BIG waveguides, and BIG subs.

Is there a way to get the same BIG sound without resorting to twelves in the dash?

When I finish the install on my new Accord coupe, we're going to know.

Before I detail my new system, I'd like to share some information on my OLD system. Anyone who knows USD Audio or Image Dynamics would like my old system. The system in my OLD Accord is a lot like those classic USD setups. I'm using horn-loaded JBL compression drivers under the dash with 8" B&C woofers in the firewall. I swapped out dual 12s for a single horn loaded 8" about a year ago.

And how does the old system sound? People have told me that my Accord has the best image they've ever heard in a car. I am personally proud of the dynamics. Most importantly, few people realize just how much power I'm pushing, over 1000 watts. Which is a HUGE amount of power for a system with prosound drivers. I've invested endless hours tuning the system so that it's dynamic and sweet at the same time.

Now you might ask yourself, if the old system is SO good, why wouldn't I just move it to my NEW Accord?

The old system isn't perfect, so I'm starting the new system with a clean sheet of paper. The biggest problem is that it takes up a LOT of space up front. My horn-loaded compression drivers are the size of canteloupes, nearly twice as big as the B&C compression drivers used by Image Dynamics. My horns are ENORMOUS. I am using the smallest 8" woofer that money can buy, but it still takes up a lot of space. The bottom line is that the old Accord sounds fantastic, but it's hard to live with.

I'm confident that the old system sounds better than 99% of the cars out there. But it's not perfect. If I could change one thing, I would set the new system up so that it sounds great from BOTH seats. But that's tough to do! I'll explain why later, and I'll offer a solution too. Another problem is that i'm using huuuuuuuge JBL 2470 compressin drivers so that I can cross over very VERY low (700hz.) But you can't have your cake and eat it too; the low crossover point has taken a bite out of the last octave.

The bottom line is that I want my new car to sound BETTER and take up less space than the old one.

So how am I going to pull this one off?

Stay tuned...
Majestik6 is offline  
Old 09-27-2006, 10:38 PM   #2
bobditts
Senior Member
 
bobditts's Avatar
 
Join Date: Mar 2006
Location: Denver
Posts: 806
Default

I would think 12s in the dash would be bad. The sound wave wouldnt mature until it reached the back of the accord. Thats just my mouse wheels turning in my head. anyone else have a thought on this?
__________________
Soon to be current setup - ***UPDATED*** 10 Feb 07
"People with mullets live 40% longer" - Ricky Bobby
bobditts is offline  
Old 09-27-2006, 10:38 PM   #3
Majestik6
Senior Member
 
Majestik6's Avatar
 
Join Date: Sep 2000
Location: Redmond, WA, USA
Posts: 258
Default

As detailed in my last post, I want the system in my NEW Accord to sound better than the system in my OLD Accord, and to take up at least 1/2 the space. This is how I'm going to do it.

The first things that have to go are the HLCDs under the dash. The only problem is that I *love* HLCDs. Everytime I listen to conventional seperates, the lack of dynamics and vague imaging is a COMPLETE letdown. So how do I get the impact of HLCDs without losing legroom?

The solution is the BMS 4540ND. This lil' compression driver is no bigger than a conventional tweeter.

But what about the horn? A compression driver is useless without a horn, right?

Yes, the BMS needs a horn. But the best horn in your car is right in front of you; it's your windshield. In my Accord, the windshield and the dash form a horn that's practically ideal for both the mids and the compression driver.

The biggest problem with using your windshield for a horn, is how do you mount the compression driver?

I think I've solved this as well. Back in the 90s, there was a Camaro on the competition circuit that had HLCDs BEHIND a custom dash. But the BMS driver is so small, I can get it into the corners of my dash. The only problem is that the BMS doesn't go nearly as low as the JBL 2470 that I have in my old car.

If the BMS doesn't go as low, then what's the solution?

I think the solution is to clone a Unity horn, a novel horn loading arrangement patented by Tom Danley when he worked for Sound Physics Labs. I am going to be the first person to ever cram a Unity into a car!

Here's what the Unity looks like:



Now you're wondering how I'm going to cram that monster into my dash. Here's the plan.

First, the Unity uses a B&C compression driver that's the size of a frisbee; I'm using a BMS that's smaller than the palm of my hand. Second, my windshield IS the waveguide, so instead of a 16" horn, I can get away with something that's only 6 or 8 inches in diameter.

The tricky part is where to put the midranges. In SPL's Unity design, the midranges fire into the throat of the horn, from each of four sides. But there's no room on my dash for four midranges.

Even if I used 3" mids instead of the 6" mids in the unity, there's still no room for them. But why do we need to put the mids at the throat? In the Unity horn, the mids are ported to the horn through tiny holes in the throat. There's nothing stopping me from moving my mids away from the throat; the only essential element is the HOLES, not the mids. My solution is to use a wedge shaped enclosure, with a port connecting the enclosure to the throat of the waveguide in my dash. I know, I know, this is completely confusing. Take a look at my drawings and pictures, I've done my best to make this clear. In a nutshell, I am using two 3" mids in wedges, and they breathe into the waveguide just a couple of inches from the throat of my waveguide through a set of holes that tune the enclosures.

These are my cheesy notes, in classy ball point no less.


Here's a pic of my ghetto baffle and mic. The midrange I'm using is a AuraSound AS3. Seven bucks at PE. To pull off a Unity horn, you gotta use a mid with a high FS.
Majestik6 is offline  
Old 09-27-2006, 10:42 PM   #4
Majestik6
Senior Member
 
Majestik6's Avatar
 
Join Date: Sep 2000
Location: Redmond, WA, USA
Posts: 258
Default


Here's the response of the Aurasound AS3 on a simple baffle. It's fairly smooth, and it sounds good. For seven bucks, you can't go wrong. It's big brother is better, but it's FS is too low for my project.


The midranges on the unity are in a bandpass enclosure. The design above is what my computer said would sound good. Unfortunately, my computer was w-r-o-n-g. The only way to get the Unity mids to sound right is a lot of trial & error. I think this has something to do with the fact that my software was designed to model subs, not mids.


Here's a compression chamber I made for my Aura mid. In the car, this chamber will be wedged shape to blend into the dash. I used 3" pipe for this proof-of-concept. Note that the piece of pipe on the left is the FRONT chamber for the mid on the right. Just like a bandpass sub, but smaller!

http://spicealley.net/~johnv/carsoun...Unity926-5.jpg

Here's a pic of the Aura woofer in the compression chamber. Note the 1/2" hole in the front of the chamber; this is key to the design.
Majestik6 is offline  
Old 09-27-2006, 11:17 PM   #5
Majestik6
Senior Member
 
Majestik6's Avatar
 
Join Date: Sep 2000
Location: Redmond, WA, USA
Posts: 258
Default


I measured my three inch woofer under three different conditions. First, I measured it on a baffle. Then I measured it in the plastic compression chamber, using a dozen different sizes. When I found a size that worked well, I hooked it up to a 12" wide oblate spheroidal waveguide and measured it again.


After coming up with a design on the PC, this is how it measured. Which is AWFUL!!! This design is UNLISTENABLE. As soon as I hooked it up I could tell it was all wrong. The computer model didn't predict the resonances up high, which are due to pipe resonances. But all is not lost, keep reading, it gets better!!



This is one of the Mathcad predictions.



Are you interested in trying this yourself? I measured the specs on the Aurasound woofer, and you can get them here: (The dimensions of the original enclosure are here as well, but the first enclosure sounded awful.)
Majestik6 is offline  
Old 09-27-2006, 11:40 PM   #6
Majestik6
Senior Member
 
Majestik6's Avatar
 
Join Date: Sep 2000
Location: Redmond, WA, USA
Posts: 258
Default

Here's where it gets good. I tweaked the size of the bandpass box for the mids and came up with a response that's flat for about 2.5 octaves. Now that's not a lot of bandwidth, but it's the price we have to pay. There's no other way that I know of to get the output of my mids so close to my tweeter. Coupling the mid to the tweeter is the key to the Unity design, and if we violate that rule, the whole thing falls apart. A bonus is high efficiency; two 3" mids in a compression chamber will play louder than a twelve in a sealed box!


I shrunk the front chamber in the bandpass by 2/3rds, and the response flattened out nicely. From 800 to 1600hz, this is pretty darn flat. If you were expecting flat response out to 20khz, I'm sorry to disappoint you!!! All I intend to do is used 2 or 2.5 octaves. The top end is going to be covered by the compression driver.



Here's the response of the driver in a bandpass compression chamber, on a waveguide. Note that the upper midrange has flattened out a bit, as we'd expect.


If anyone's found a smaller compression driver, let me know. The waveguide is oblate spheroidal, built by yours truly. In the car I will blend it into the windshield, for maximum control of the sound.


Here's a mock up of the waveguide and woofers on my dash. The compression driver is tucked into the corner of my dash, and the waveguide on the CD will be blended right into the dash and the waveguide when I'm finished. Dual 3" woofers will sit in low-profile bandpass boxes that form the bottom half of the waveguide. Can you picture that?
Majestik6 is offline  
Old 09-27-2006, 11:52 PM   #7
Majestik6
Senior Member
 
Majestik6's Avatar
 
Join Date: Sep 2000
Location: Redmond, WA, USA
Posts: 258
Default


I didn't bother to check the voltages on the SPL measurements, so here's a 12" prosound mid for comparisons's sake. (This is a P-Audio SN12MB in case you're curious.) It's 6db more sensitive than my Aurasound 3" woofers. But once I add a 2nd woofer in parallel and double the power, my puny lil' 3" mids will be just as loud as a prosound 12!! Unreal.


Side view of the BMS compression driver, the waveguide, and the enclosure for the mids. (this is just a mock-up.) Both the mids and the waveguides have a perfectly unobstructed path to the listener, insuring the most pristine response possible!


This is just a mock up, I'll do my best to make the real thing blend into the dash, for sonics AND aesthetics.


The waveguide and the woofer are crossfired. This is the only way to get a solid center image for both the passenger AND the driver. When I get a chance, I'll explain why this is the only option that works.
Majestik6 is offline  
Old 09-28-2006, 12:12 AM   #8
winslow
Senior Member
 
Join Date: Apr 2000
Location: Charlotte, NC
Posts: 4,037
Default

Been wanting to mess around with the Unity horn for a couple years now.

What kind of pattern control are you going to get with those horns you made?
__________________
Team Image Dynamics/Werewolf/JK Labs
Sick Bastard Audio SQ
Who feels it knows it
winslow is offline  
Old 09-28-2006, 12:23 AM   #9
Majestik6
Senior Member
 
Majestik6's Avatar
 
Join Date: Sep 2000
Location: Redmond, WA, USA
Posts: 258
Default

Quote:
Originally Posted by winslow View Post
Been wanting to mess around with the Unity horn for a couple years now.

What kind of pattern control are you going to get with those horns you made?
Though I've studied the Unity for about five years, there was one piece of the puzzle that I couldn't figure out... Until last Sunday. Now that I understand how that last piece works, I'm certain I can build one.

My pattern control is mostly dictated by my windshield. So that's 90 degrees horizontally and 45 degrees vertically. 90 degrees is simply the angle dicated by the corners of my dash.

Having said that, the coverage angle will collapse a bit near the throat; this is a compromise so that I can have a smooth transition from the throat of the compression driver to the windshield.

:: PB ::
Majestik6 is offline  
Old 09-28-2006, 04:34 AM   #10
Puggie
Member
 
Join Date: Aug 2006
Posts: 67
Default

Nice, I wondered about running horns up the back of the dash and using the windshield as a waveguide but whenever I suggested it people said NO it wont work. I'm now starting to listen to the voices in my head more than the 'experts' and try more things.

I almost bought a pair of those BMS Compression drivers, I wish I had now.

I never thought of tryng to build a Unity horn in the car bt IMHO it looks very cool.

would there be any way you could drop the throat of the horn into the top of the dash firing upwards and bend the horn where it meets the screen/windshield, you could then put grille cloth over the top of the dash to make it very stealthly.
Puggie is offline  
 


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -4. The time now is 03:30 PM.


Powered by vBulletin® Version 3.6.8
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.