SPL only Vented Tempest (1 Viewer)

[Chris Tsutsui]

I'm trying to design an SPL competition enclosure for a single tempest with maximum SPL at 43-47hz in mind, (tuning frequency of car). I've been crunching numbers in WinISD and Adire Audio but am still undecided on a design.

The size range preferred is between 70 and 200 liters.

I have two flared 3" diameter vents I can adjust length. The tricky part is the smallest flared port possible is still about 6" from flared tip to tip. So for a box that's 100L, tuned to about 40hz but it asks for a port that's 13cm which is the length of a flared port without a center tube. (am I right?)

The other designs such as bandpass 4th and 6th order were interesting but they don't have the option of having the ports plugged for a "sound quality" conversion like a vented sub does.

Basically what I'm looking for is a box that has maximum SPL at about 45hz that has the option of the ports being plugged for sealed operation. I guess that another limitation is the minimum size of the flared port which would be a center tube of 0".

Any advice or suggestions from fellow bass people would be appreciated.

Here's my first design:

Box volume = 100L
Dual Ports: Length = 13cm (Which is 0" center tube)
Res. Freq. = 39.5hz
Result 1w/1m = 93db @ 43hz (with a -3db downpoint at 39 & 57hz)
Has an 8-10db boost over a 100L sealed box.

I still don't know if I should just slightly alter Adire's SBB4 design by decreasing the volume and tuning it slightly higher for a just plain SQ car sub. (SBB4 = 194L tuned to 18.8hz).

Do you think I'll be capable of SPLs to enter in a competition? I have a bridged 600 watt amp @ 4 ohms 12V for it. I also have a 1 farad cap, 4 gauge wiring, and the whole back of a Toyota 4runner to work with.

 

[Dave_Gib]

I'd just make 2 ports with 1 to tune it low and the other for spl. I haven't played with the tempest too much, and I'm no master of the metric system, but if a 5.0 is 305 in^3, that's like a 3.5 cu.ft. box. have you checked the group delay on a 3.5 cu.ft. sealed box?

Ok I went and put it up on ISD. Go about 15 cu.ft. or 454 Liters. But that will throw SQ right out the window

How did you find your resont freq of the cab?

 

[Chris Tsutsui]

454L is huge, I was simply trying to find the optimal vented SPL box design that is between 70-200L.

To calculate my cabin resonance I simply played various sine waves and specific test tones and wrote down the ones that consistently had the most spl. The main two peaks were about 45 and 52.

I have others subs for this testing, and I'm able to isolate them because I have easy access to the amps.

That's actually a good suggestion, I havn't considered using two differently tuned ports.

For a 100L box (3.5 CF) the group delay peak is at 7.5ms @ 30hz which is plenty acceptable.

 

[Mark gas]

Anyone can enter spl comps, are you going 5to win the DB Drag world championships not likely. what amp are you running? Also check out www.termpro.com home of DB Drag racing.

 

[Chris Tsutsui]

Thanks for the link, I don't expect to win anything, just see if I can get break the 140s which for me would be pretty neat.
I'm running the "1500" watt Alpine MRV-1507 which is really going to be pumping 600 watts RMS @ 4 ohms with 12 volts into my tempest (parallel VC). I actually don't have the amp yet but I bought if used off someone here on the HTF and it should be here soon.
I know I wouldn't stand a chance for sound quality unless I custom fit some new speakers in.
Here's my 94' Toyota 4 runner SR5 V6 with too many name brands (most of the stuff is a year or 2 old):
Pioneer TS-G1040 4" 2-way front dash, in ported box that I sealed
Alpine SP series 5 1/4" component 2-way, in rear ported boxes
PPI 2200 (100wpc for rear)
Dual 10" PPI subs (replaced with tempest)
Alpine MRV-1507 (600W for tempest)
Sound Stream USA-100 (40wpc for front)
Sony CDX-4K receiver
Installation is mostly gold plated generic parts from Parts express, other brands include Amp king, Scosch, Radio shack gold series, Phoenix gold, and Monster cable.
1 Farad capacitor, no distribution block used, all my wires go from battery to fuse to amp.
I use Dynamat Original on rear quarter panels
I replaced the factory speaker wiring with 18 gauge home depot stuff, everything is hidden except for the sub box. I have done absolutly nothing to the external parts or performance of the car itself, only Audio.

 

[Dave_Gib]

a 15 cu.ft. box will give you a 12 dB spike at 45 Hz, if you want spl, that's how alot of people do it. I did low 150's with 2 $90 12's in a 9 cu.ft. box with this method.

"To calculate my cabin resonance I simply played various sine waves and specific test tones and wrote down the ones that consistently had the most spl. The main two peaks were about 45 and 52."

did you measure the response of the subs out of the vehicle and compare?

 

[BrendanL]

check out teamamp.com
its adire's car audio forum, and there are some guys getting mid 140's with a tempest.

 

[Mark gas]

a 15 cu.ft. box will give you a 12 dB spike at 45 Hz, if you want spl, that's how alot of people do it. I did low 150's with 2 $90 12's in a 9 cu.ft. box with this method.

was that score legal?

 

[Dave_Gib]

only did 147.9 on the dash, low 150's on friends AC, outlaw style. I didn't top out, just got bored with it.

 

[Chris Tsutsui]

"Did you measure the response of the subs out of the vehicle and compare?"

No I have not, but am pretty positive that 45hz is my cabin resonance because I've tried two different subs in my car with similar spikes. I would assume the the cabin resonance doesn't change at different volume levels but I could try checking it at higher spls. The measurements were taken at about 90db and the spikes were adding about 6-8db.

If I really wanted to get into competing I'd probably have saved for a Brahma or Tumult and used a bigger amp. I simply want a system that can shell some decent SPLs (more than your typical car boomer) and have the option of sounding "ok".

A high Q interests me like the 0.9 Chebychev sealed alignment by Adire. It would be great if that box could open up ports to produce a spike at 40-50hz. (If it's possible)

I'm not looking for deep extension, a cut off at 33hz is suitable. I have my listening room and HT for my other types of music. In my car, I crave bass that's not necessarily accurate, but can kick the crap out of people inside. My system isn't all that great for listening carefully anyways.

Here's what I'm looking at right now.

90L box
Qa = 100
Ql = 15
(I don't know what Qa or Ql is so I kept them at default)

Port = 12cm (flared port w/o center tube)
Min Dia. = 7.6cm (3 inch)
Flare radius: = 6.0cm
min area = 45.4 cm^2
Res. Freq = 42.4 hz
Number of Vents = 2

Results: -3db downpoint @ 34hz, large spike at 45hz. Skyrocketing group delay at 45hz.

But the problem is I don't know if that's all there is to it to equate to sound given at 600watts. I read a 20mm P-P excursion, Group delay at 22ms... is that realistic?

This will be my first sub box design and I'd like to get it right so I don't get a bass hump at 60hz or something. Any comments on if this one will suit me?

Maybe I should head on out of this forum to the Car audio places for advice on this, I just thought that there were ppl who could simply give me the "ok" before I build my 90L convertable car boomer.