Evening all...

After thinking much about what kind of sound i want for the car, i'm tossing up the idea of an ABC enclosure...

Has anyone here used these? And if so, does it behave in all ways the same as a ported box except with a tuning shelf rather than spike? If i tune low (25Hz or less), will it cause the top end to roll off quicker than a normal ported box?

In short, i want to know if it will sound better than a standard ported box given that i have about 120L of boot space available, will be lowpassing the sub at 63hz @ 24dB/o and subsonic highpassing it at 20Hz @ 24dB/o The subs i want to use have a Qts of 0.35, and i plan on using either 2x 10" or 1x 12" subs... if i use the single 12", the drivers Qts on the model i want is 0.25

Cheers for your help and/or suggestions

Have'nt heard one yet but from what people have said they are very very good
but as i said i havent heard one so wont give it my thumbs up yet

the appeal of a properly designed aperiodic enclosure (super good transient response read: tigntness/speed) is high.

the complexity and fiddling makes it one for my "too hard" bin, especially in my cramped skyline boot...

d

Hahahaha and you think your boot is cramped - you should see blackrazors. Damn s13 silvias and their mini boots.

Heh, i can fit in 112L, i worked it out yesterday

Remember, when your boot has no other purpose than to house a box, its surprising how much room you have...

On another note Dave, the Silvia has no back seat now, and the MDF is getting cut for the amp mount racks as we speak

lol. aaah i see. so basically your car is going to become a mobile stereo with 2 chairs in it!

silvia back seats are virtually useless anyway. ever tried to cram your mates in the back?? lol my mate's s13 and another mate's s15 have rear seats purely for novelty, cos i get out of them with a crook neck... every time.

and damn your boot to hell! its still larger and more practical than mine! *grr*

we want pics when its done!

d

Don't dis the s13 back seats. I teavelled 2500k's with four people in the car (christchurch/auckland return). Admitedly I was the one driving so I never experienced the rear seat.

BR good to see the install is moving along - damn it you're way ahead of me.

Least you got all your gear other than the amp, i've still gotta organise some subs :/

Bingo :wink: I have a Bluebird too, and the missus uses that and we use it for trips, the Silvia is simply to run to work and back, and to be my SQ wagon

I think I may have lost my Arvus tweeters - damn it I'm not used to having such small beauties Hopefully they'll turn up when I change house.

:shock:

:cry:

Man i'd be pissed

lol. yeah i lost one dyn crossover for like 3 weeks. turned the house upside down.

.... was in the box :oops: i nearly kicked the neighbours cat when i opened the thing. :x



d

dude what enclosure sizes and port sizes are u using for the 12"sub only plan? and how do u work it out for this type of enclosure???

I havent finalised the plan yet because i still havent finalised what subs i'm buying, once i decide all that i'll measure it up and post some box schematics for you to have a nosey through

i have built a couple of these myself, both with quite nice results. The main issue is see is that u plan to have one part tuned to 25hz, this means your frequency range will only be 25-50hz (admittedly with the rolloff after those freqs, unsure of what the rolloff is like though). I hope the arvus mids like playing low.

A better suggestion might be to tune for a bandpass between 30-60hz as you plan to have the lowpass on 63hz. You will find that the output below the lower tuning is still quiet good without losing control. The box i made for my PG had a bandpass between 38-76hz and sounded pretty good IMO. Better than the old standard ported box anyway.

so you have roughly 4.2cuft for the box? if so thats pretty similar to my old one (4.5cuft total, 1.5cuft & 3cuft chambers respectively)

-3dB @ 40Hz low enough? :wink:

I suppose the attraction of the ABC box is the great transient response, no bandpass or ported box can match it, at least not any i've personally seen..


The subs are low passed at 63Hz with a 24db/o crossover... the 25Hz is something i'd aim for... the chambers, from what i've picked up, dont HAVE to be the standard 33%/66% split, apparently if you're a bit inventive you can get some sneaky results, like a 20-60Hz freq range (admittedly with a slightly less flat response between the two peaks, but 1dB probably wont make much of a noticeable difference bass-wise)

hmmm, i thought the whole point of the ABC box was to keep the chambers exactly 1/3 + 2/3 and ensure all 3 ports are identical lengths, else it can stuff things up?

i personally havent messed with the theory by changing the chambers as i was happy with the way it sounded when built normally. i would be interested in what results you get by changing this though.

At anyrate i was pleased with the sound of ABC boxes i made for my PG 15 and my 8" venom. havent really had any huge indepth look into furthering them so cant really help you much more.

Changing the chamber ratio simply brings the tuning points either further apart or close together Essentially if you had a 50%/50% split it would simply be a ported box with a very high efficiency per cone movement

Changing the port lengths, now THAT makes it tricky, so this dodgy Kiwi be staying the f**k away from fiddling with that

so what are the reccomended port lengths 2 start with for a 12"?? assuming the 1/3-2/3 ratios are used on a box that is 4.5cu/ft total volume??

Depends on the driver, you have to tailor the box to the driver you use Hence why i havent finalised the plans, i havent finalised what driver i'm getting

sorry man of course this is the case, ive been not thinking straight on this one....

if i put up all the specs for my sub could u give it a go 2 punch out some numbers for me reguarding the sizes???

Er, its quite easy to do a simple one dude

Just work out how big a box your sub needs when ported, and design a port that will tune it low (to 30Hz or less).

Then you make 3 of those ports, divide the box area by 1/3 and then divide off a section that size with a partition wall. Then you use one of the ports each to port the 2 chambers, and then use the third to port between the chambers, like so :




Of course, its a little bit more complicated that and you have to experiment a bit, but thats the basics

One question for VL Commy : When you design these boxes, is the tuning for the main chamber calculated with a single port? or do you factor the second port connecting the chambers into the calculation?

i thought the sub went in the wall between the 2 chambers??

or am i getting confused with 6-order banpass??

when i designed mine i calculated tuning for ONE port for 38hz tuning for the entire box size (4.5cuft).

Yep, you are

if those ports are the same size and one "half" of the box is 1/3 in relation to the rest of the entire box, then yes thats an ABC enclosure.

btw, how did that sound?

d

yes everything was made to specs of an ABC box ie. 1/3 + 2/3 theory. this includes taking into account port displacement for each chamber.

so was pretty good on both of them. The one with the venom suffered from port chuffing at higher volumes, however at lower volumes the SQ IMO, was pretty good.

i would recommend everyone should try to build one at least once, just to see how it sounds and try out different box designs.

ok, so i dont do this wrong and get crap results, lets re-cap

1; work out box volume for the specific sub tuned low in a big box(75-120 lts for a 12"approx)
2; divide this total volume in the ratios 1/3 and 2/3
3; use 3 identical ports as calculated for the single chamber big box (port size from step 1)
4; one in each chamber and one connecting them,
5;drop the sub in 2 the face of the bigger chamber, having exposed ports and sub all on the one face of the box.
6;put them in and play, tuning by shortening/lengthening the exposed ports 2 suit (or is it all three ports that need 2 be played with?)

Most of the posts i've read about it mention perhaps aiming to make the box 2x as large as the recommended enclosure for a normal ported box for the sub

typically you would go for the largest size ported box you can that would still sound musical.



if you change one port, you must change them all.

Guys just a quick note, in Step 1 you need to calculate this tuning with TWO ports not one.

Both ports in the final design will be in use therefore you need to calculate the starting value for both ports!

I've built quite a few and had REALLY good results with them. The tuning ends up being exactly 1 octave apart if the ratios are maintained. The roll-off on the bottom end is quite steep so I usually tune to 30 or 35Hz (therefore the top end becomes tuned at 60 - 70Hz respectively). The top end roll-off has not been an issue with any of the boxes I've built so far, in fact the peak gain typically ends up being approx 5Hz above the tuned freq. The 12" design will quite easily play up to 110Hz!

On the downside these enclosures are not the most accurate and can require some EQ adjustments to smooth out the response. In addition there is a fair bit of group delay as well.

Bang for buck though these things rock and LOVE the low notes while not loosing the upper end punch!!

Hope this helps...

crazy canadian! :roll:

OK this is going to sound weird, but...

Can i build an ABC box with a removable cover over the ports which bolt down via wing nuts, so that i can use the box as either a large sealed box for SQ comps or an ABC box for daily driving?

And if so, how hard is it going to be to get a sealed box of 0.707 Qts alignment AND still be able to port to 28Hz/56Hz or so without port noise for when the blocking panels are removed?