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brandon_s0854
02-01-2013, 09:24 AM
Didn't get much help at CACO, so I'll try here. Looking for suggestions on this design for two SA-8's. Goal is a loud daily system. Will have approximately 1000W given to the pair. Looking for near flat response from 25-60hz. Would love to be near the 140dB level, but I know that's shooting high for two 8's.

Design
Rear Chamber: 1.5cf @ 35hz with 15 in^2 port area
Front Chamber: 1.5cf @55hz with 30 in^2 port area

Just looking for general tips. Maybe a better layout can be had with my dimensions. Or different volume chambers would work better, maybe different tunings. Want to make sure it's not going to be too heavy on the upper frequencies. Really want it to pound in the 30-50hz range.

Thanks for the help gents!

26539742

Beatin'
02-02-2013, 11:34 AM
according to winISD, based on your volume and tuning, it will be EXTREMELY peaky with a sharp dip in the middle. I don't believe it will be "musical".

The response curve looks and like an "M". At around 68hz your at 0db reference, 55hz at +22db, 42hz at +5db, 35hz at +16db, 30hz at -3db.

It looks like it will sound terrible....

brandon_s0854
02-02-2013, 11:59 AM
My WinISD model didn't look near that peaky. Can you post the t/s parameters you're using? I don't have the model on my phone, but it was more like 6dB peaks at 35hz and 10dB at 55hz. With sixth orders, you're never going to get a flat response, but that doesn't mean they can't sound decent on music.

ciaonzo
02-02-2013, 12:01 PM
Actaully, it will always sound bad with 'music'. Take a look at the group delay on that 6th order.

brandon_s0854
02-02-2013, 12:05 PM
The M curve you're talking about is going to be with any sixth order. That's why they're not used in sound quality builds, but you can gain a lot of efficiency in the passband. That's what I'm going for here. This is for someone with a discerning ear, so I'm not too worried about 10 dB peaks, but 20 dB is a problem. Lol. I'm thinking cabin gain is either going to help me out here, or make it even more perky. Unfortunately, I have no idea what cabin gain is here, nor how reliable WinISD is at modeling 6th order alignments.

brandon_s0854
02-02-2013, 12:06 PM
Actaully, it will always sound bad with 'music'. Take a look at the group delay on that 6th order.

To each their own, I've heard several that didn't sound bad by any means.

ciaonzo
02-02-2013, 12:07 PM
How about a generous 4th order and let the transfer function do the rest?

brandon_s0854
02-02-2013, 12:10 PM
How about a generous 4th order and let the transfer function do the rest?

I think I modeled a 4th and there was quite a bit more output with a 6th.

Beatin'
02-02-2013, 12:44 PM
My WinISD model didn't look near that peaky. Can you post the t/s parameters you're using?

I got them from the sundown website. SA8v2 D2's....

RE: 3.36 ohms
FS: 34.6 Hz
VAS: 7.44 L
Qes: 0.35
Qms: 10.10
Qts: 0.33
Le: 1.34 mH
BL: 17.56 NA
Mms: 146.120 g
Sens: 81.5
RMS: 500 Watts

It seems like the subs have too high of an EBP rating for anything other than a ported box. The 4th and 6th order setups don't come out right. Too small of a passband, especially on the 4th order if tuned low.

That's the cost of going with 8" subs. I don't know how or why this trend with small subs got started.

NASTY08IMPALA
02-02-2013, 12:46 PM
just do a 4th order and be done ive seen 1 2 and 4 sa8.s in them and they turned out great

brandon_s0854
02-02-2013, 01:16 PM
I got them from the sundown website. SA8v2 D2's....

RE: 3.36 ohms
FS: 34.6 Hz
VAS: 7.44 L
Qes: 0.35
Qms: 10.10
Qts: 0.33
Le: 1.34 mH
BL: 17.56 NA
Mms: 146.120 g
Sens: 81.5
RMS: 500 Watts

It seems like the subs have too high of an EBP rating for anything other than a ported box. The 4th and 6th order setups don't come out right. Too small of a passband, especially on the 4th order if tuned low.

That's the cost of going with 8" subs. I don't know how or why this trend with small subs got started.


Oh, that's why it's so different. I'm using v1 SA-8's. Here's the models I have comparing the current box, a 4th (.5cf sealed 50hz resonance, 1.5cf ported @ 50hz), and discussed 6th order. One is group delay; other is SPL at 1000W. This is figuring in a 6dB/octave cabin gain starting at 50hz. That's a pretty minimal cabin gain.

brandon_s0854
02-02-2013, 01:23 PM
just do a 4th order and be done ive seen 1 2 and 4 sa8.s in them and they turned out great

And this is why I'm asking for help. The both v1 and v2 SA-8's model horribly in 4th orders. Unless you tune at like 40 and don't mind having any output above 50hz, and yet people still say they've heard 4th's that turned out great.

NASTY08IMPALA
02-02-2013, 01:30 PM
all the ones ive seen have been tuned mid 30.s

brandon_s0854
02-02-2013, 01:36 PM
all the ones ive seen have been tuned mid 30.s

:confused: That doesn't make any sense. Should've been EXTREMELY bottom heavy. Sounds like somebody was misinformed. Like almost no output above 45hz and overal output would suffer since you couldn't get sealed resonance low enough. Not saying that you're wrong, but I find that highly unlikely.

NASTY08IMPALA
02-02-2013, 01:40 PM
:confused: That doesn't make any sense. Should've been EXTREMELY bottom heavy. Sounds like somebody was misinformed. Like almost no output above 45hz and overal output would suffer since you couldn't get sealed resonance low enough. Not saying that you're wrong, but I find that highly unlikely.

ur right the numbrs dont add up but once put in the car sounded good..one of those test test test things

brandon_s0854
02-02-2013, 01:44 PM
Yeah, I hate doing that, but it's probably a must when you're building 6th's. They almost never come out right the first time from what I've been reading. I just want to throw it in the vehicle and sound right. lol. Just speaking from models, I could drop tuning to 30hz rear/45hz front and it would kill a big 4th tuned to 40 at every frequency above 25hz.

mlstrass
02-03-2013, 02:26 AM
Personally I wouldn't build it for a 10db hump somewhere, not always good on the subs. And my series tuned 6th order is very musical, no it's not an SQ set up, but it plays relatively flat from 30-60Hz, gains about 2db every 10hz and drops some at 60Hz.

If you do end up with a huge hump then I'd EQ that out for daily and take advantage of it when metering....