Charles Phillips Posted May 22, 2017 Report Share Posted May 22, 2017 Hey, so I've been studying the decaf astra for a while and I can't figure out for the life of me what's going on that makes the lows hit so hard... but I have a theory. I'm thinking it's a quasi 6th-order bandpass with the cabin acting as an 8th order chamber. If you look at the specs of the woofers, here, the resonant frequency of them free air is 40hz. Thiele and Small stated at least in ported boxes that they should be tuned at f(s) because that's where the sub operates most efficiently, but hurricane winds don't lie. I know resonant frequency isn't the only parameter that matters, but I'm trying to figure out how to do something similar so I'd like to understand how it works. I've tried getting in contact with the owner over YouTube comments, but there's an obvious language barrier and I'm sure he doesn't have time in the day to answer all the many comments he gets. Thanks in advance for your help! - 2009 Toyota Matrix Base - - iPad 64GB - - miniDSP 2x4 HD - - PPI Art a200.2 - - SoundQubed SQ-2200.2 x 2 - Link to comment Share on other sites More sharing options...
the_garynator Posted May 22, 2017 Report Share Posted May 22, 2017 Contrary to popular belief, my opinion is that it's just a series tuned 6th, with the cabin and area above the rear 4 subs being the front, large chamber. The doors / windows act as the port when they are opened...think about it this way, if you built one big box with the same volume as his car's interior, then placed a box in it with 4 subs firing up, 2 firing forward, and port firing up, the larger chamber would act as one, even though 2 subs are firing forward. Current Build: Project Flexington: 157.6db @ 37hz Parallel 6th order walk through, DC Neo Elite 18s, 4 DC 5.0ks, JY Lithium, 12 banks of XS Caps Old Builds:150db and HAIRTRICKs from 2x 12" Power Acoustik Mofos (6th order blow through) ;<p>Roadmaster Wagon Build - DC LVL 6 M3, Kicker Warhorse ; Godzilla swapped 240sx ; 6th Order Bandpass Alpine Type R 12 ; Fully loaded DC Level 5 18" 240sx Link to comment Share on other sites More sharing options...
Charles Phillips Posted May 22, 2017 Author Report Share Posted May 22, 2017 I agree with that completely. So he's not just calculating the top portion as the chamber but also the cabin... So it's basically like sitting inside of the port. While a lesser box may do 140dB in the cabin, internal box sound pressure might reach 150dB or more. He's just taking advantage of that I suppose. But the inside doesn't look like it's that buff compared to the box. Just a stripper pole really, and you'd have to take every person and object in the car into consideration when determining the volume. - 2009 Toyota Matrix Base - - iPad 64GB - - miniDSP 2x4 HD - - PPI Art a200.2 - - SoundQubed SQ-2200.2 x 2 - Link to comment Share on other sites More sharing options...
rocking.that.eclipse Posted May 22, 2017 Report Share Posted May 22, 2017 I think a lot of the wind you are seeing moving is because the port it literally right at your head. Link to comment Share on other sites More sharing options...
Charles Phillips Posted May 22, 2017 Author Report Share Posted May 22, 2017 That also makes sense, but I can't get over why he's capable of getting those numbers on something like 17hz or even less with some pretty basic 1500 wRMS subs. I have 2 HDC3.118 D2s, so theoretically I could do something similar, right? I don't think I could expect a 160 at 15hz or anything, but I'd like to at least get 20hz - 40hz flat and have midbass take care of the rest. - 2009 Toyota Matrix Base - - iPad 64GB - - miniDSP 2x4 HD - - PPI Art a200.2 - - SoundQubed SQ-2200.2 x 2 - Link to comment Share on other sites More sharing options...
rocking.that.eclipse Posted May 22, 2017 Report Share Posted May 22, 2017 Where have you seen numbers that he has done? Link to comment Share on other sites More sharing options...
Charles Phillips Posted May 22, 2017 Author Report Share Posted May 22, 2017 Here's a link to it on a meter. I wasn't exact but that's still some pretty big numbers. I mean I have 1 SoundQubed HDS3.112 D2 on 2200 wRMS installed currently, so anything I do will be louder for sure. - 2009 Toyota Matrix Base - - iPad 64GB - - miniDSP 2x4 HD - - PPI Art a200.2 - - SoundQubed SQ-2200.2 x 2 - Link to comment Share on other sites More sharing options...
rocking.that.eclipse Posted May 22, 2017 Report Share Posted May 22, 2017 You don't know where the meter is for that run. He has a ton of cone area in a small cabin also. Link to comment Share on other sites More sharing options...
Charles Phillips Posted May 22, 2017 Author Report Share Posted May 22, 2017 That's true. 6 15's on 13000w (not sure if that power is still current) is nothing to sneeze at in any car. I was hoping by using thick materials for my box I could take up enough space that the cabin would act as 1/8th space or at least make it easier to pressurize. - 2009 Toyota Matrix Base - - iPad 64GB - - miniDSP 2x4 HD - - PPI Art a200.2 - - SoundQubed SQ-2200.2 x 2 - Link to comment Share on other sites More sharing options...
ShadeTreeMechanic Posted May 22, 2017 Report Share Posted May 22, 2017 I was thinking his box looked small for six 15s especially ported. What do you guys think? 91 C350 Centurion conversion ( Four Door One Ton Bronco) 250A Alternator (Second Alternator Coming Soon) G65 AGM Up Front / Two G31 AGM in Back Pioneer 80PRS CT Sounds AT125.2 / CT Sounds 6.5 Strato Pro component Front Stage CT Sounds AT125.2 / Lanzar Pro 8" coax w/compression horn tweeter Rear Fill FSD 5000D 1/2 ohm (SoundQubed 7k Coming Soon) Two HDS315 Four Qubes Each 34hz (Two HDC3.118 and New Box Coming Soon) Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.