40th Birthday present

[BOOMINGRANDPA 5,000+ posts]

Sub sonic filter (if accurate) is 3db down point (half power). Setting sub sonic nearly a full octave below tuning may be adequate.
Also, did you model those subs in his airspace? Of course not, but I did and they suffer greatly, really they want an enormous box tuned much lower to play flat and wide, he is compromising with tuning higher because "optimum" airspace for those is impractical for a car.

I've been laying off, but seriously, don't spout off about things you don't know. I don't chime in about box size unless I've worked with the subs in question or at the very least modeled them.

do u think based on what he is saying he woulda just been better off doing down fired sealed box?

 

[Forcefed2002]

Sub sonic filter (if accurate) is 3db down point (half power). Setting sub sonic nearly a full octave below tuning may be adequate.
Also, did you model those subs in his airspace? Of course not, but I did and they suffer greatly, really they want an enormous box tuned much lower to play flat and wide, he is compromising with tuning higher because "optimum" airspace for those is impractical for a car.

I've been laying off, but seriously, don't spout off about things you don't know. I don't chime in about box size unless I've worked with the subs in question or at the very least modeled them.

How in the world does JL expect Joe blow to realize their w3's are best suited in an enclosure nearly 3 times bigger than they themselves recommend?

 

[Forcefed2002]

sealed is generally a flatter response with less output while ported has increased output around tuning and a more peaky response
you very well may prefer sealed with the type of music you listen to. im not an expert on the thiele parameters of loudspeakers so the sub you have may prefer ported over sealed.

Right on, I get that.

What I'm getting at is:

Because I'm sacrificing output due to me not being able to build a box large enough for them to operate properly (wouldn't have known by manufacturers specs) in a vented enclosure.

Would that loss of output be less than, equal too, or greater than that of a properly sized sealed enclosure?

I have the wattage to do so if that is in fact the case.

 

[Forcefed2002]

Working on some rear fill.

(Ignore pyramid box)

Once mounted, I'll cut out part of the panel that sits over them for a clean look.

 

[hispls 5,000+ posts]

do u think based on what he is saying he woulda just been better off doing down fired sealed box?

I don't recall if I modeled them sealed, but I doubt it.

How in the world does JL expect Joe blow to realize their w3's are best suited in an enclosure nearly 3 times bigger than they themselves recommend?

An interesting experiment would be to model out each size of w3 and see if that motor doesn't do better on a different sized cone. Perhaps they count on cabin gain filling in a bit? IDK, but what you described initially was precisely what modeling predicted it would sound like in that size/tuning.

Right on, I get that.What I'm getting at is:

Because I'm sacrificing output due to me not being able to build a box large enough for them to operate properly (wouldn't have known by manufacturers specs) in a vented enclosure.

Would that loss of output be less than, equal too, or greater than that of a properly sized sealed enclosure?

I have the wattage to do so if that is in fact the case.

Ported = free output over sealed. Sealed may give you a flatter response down low but overall won't be near as loud.

yeah but in this case box is made now, so unless he makes another one saying bigger box is better don't help today.. he just said doesn't seem like low freq problem so only other thing that will cause bottoming is to much power or airspace right? like he said in beginning he'd been better off to ask before making box.. also he plays music with higher freqs so tuning to 32hz or so wouldn't be great for him either., i understand he basically has wrong subs for what he's saying he wants.. i used to use wins but that was a loooong time ago..

Box size is fine, and was limited coming out the gate to the center console space. Again the size needed to get flat response down low becomes impractical (and would definitely kill power handling).

Guess I should have said that this bottoming out issue isn't isolated to under the tuning point (which is high 30's if I'm not mistaken)Also, most of what i listen to is 38 & up.it will hit the back plate all through the 40's & without much output. Quite strange to be honest.

It still may be lower than you think. Does your amp have subsonic filter? Have you played with it any? Is the overall response of the box good for you (how loud one frequency is vs other frequencies)? Again, you're at the point where JL voids warranty as far as the power you're running so it may just be you hit the limits of what those subs can do.

Hispls, due to that phenomenon, having to compromise with the tuning due to sub characteristics, would I see an increase in output if I where to design another box sealed?

Doubutful, but you should easily be able to screw a slice of plywood over the port hole and see if you like the way it sounds. It would very possibly solve the issue of hitting mechanical limits but you will loose output overall.

 

[Forcefed2002]

The JX1000/1D does NOT have a subsonic filter.

That being the case I am hyper aware of playing anything loud b4 knowing the song. If I suspect frequencies approaching dangerous places I either am Johnny on the spot with the volume or just avoid the track all together.

The freq response of this enclosure isn't terrible since the modifications but it's far from stellar.

I guess it is a possibility I've become greedy with the power, but after setting gains & accompianing variables using proper techniques I thought I'd still be on the safe side of the knob.

Again, It could be from the power, but there's just a gut feeling that leads me to believe otherwise.

For now I'll just turn it down.

 

[Forcefed2002]

Hispls, when you modeled my setup, what value was given for Qtc ?

 

[Forcefed2002]

I should also mention that I flipped the box so the woofers were firing up. I did this as a temporary test to get a better gauge as to what the woofers were doing. This is when I first noticed the bottoming issue. Could it be possible that when the box is in its originally designed downfiring position that there is a certain amount of baffling or loading of the speaker, in turn providing more control over the sub with a resulting absence of the current mechanical noise I hear at same power level?

Edit: I just didn't want that limit to be breached without me knowing it, is the reason for the inversion test

 

[hispls 5,000+ posts]

Hispls, when you modeled my setup, what value was given for Qtc ?

Not given by WinISD but may not be a great metric.

IDK if you can see the numbers, but yellow line is 3.8 cube sealed (.7 Qtc), red line is 7.8 cube tuned to 24hz, and green line is you after shortening the port. Any way you slice it you're compromising with these subs, either a ton of space for the red line, a load of low end for the yellow, or some linearity for the green but green line gives you a nice boost where actual music happens and should play down to mid 30s and keep things under control.

response - Imgur

Could it be possible that when the box is in its originally designed downfiring position that there is a certain amount of baffling or loading of the speaker, in turn providing more control over the sub with a resulting absence of the current mechanical noise I hear at same power level?

For the record 3.7 cube (for the pair) is .707 Qtc sealed BUT you're 3db down before 40hz. Overall the response looks very anemic though should be pretty flat.

Absolutely! The pressure on the front of the cone helps keep it under control as well. There's guys with high power builds who could be playing fine then if you open a door the cones will shred without that extra front pressure or can burp a big number with the seats out but music with seats out with break subs.

 

[Forcefed2002]

.707 to ironic.

Check this thread...

 

[Forcefed2002]

http://www.diymobileaudio.com/forum/showthread.php?t=64705

The last post.

Written by a different guy..Andy

The link to Andy explanation of why. 707 is the target is in the thread I copied. If you go to that "cabin gain" thread, the Qtc talk is about 1/3 the way down.

Talking about a Qtc of.707 giving perfect transient.

Why should I care about this?

 

[Forcefed2002]

Hispls, thx for linking the modeling (A picures worth..u know) all the effort, time & patients dealing with a random.

And 2 everyone else who've made me feel welcomed.

For comparisons sake, could you also post the graph for what the box was doing originally, b4 we modded the port?

Lastly, what would a sealed box at 1.125 ft3 each (JL sealed spec) look like?

I just think it's bad as.s how if you know how to work the program, that you can model manufacturers specs for both sealed & vented on a graph, then overlay what YOU think would work better, then sit back and take pride in the ability.

Thx man.

 

[Forcefed2002]

For the record 3.7 cube (for the pair) is .707 Qtc sealed BUT you're 3db down before 40hz. Overall the response looks very anemic though should be pretty flat.

Must be an SQ thing?

 

[Forcefed2002]

Holy shiit.

I flipped the box back over & the bottoming out is GONE!

Such an incredible change...I'd estimate 15-20% more clean controlled output.

I was honestly thinking I hurt a woofer with how easy it would bump the backplate, but that just wasn't the case.

What confuses me is what would have happened if the enclosure was designed to fire up.

 

[hispls 5,000+ posts]

Must be an SQ thing?

.707 is considered the target for SQ and home theater. Of course IMO you really don't want it down 3dB until you get a bit lower. Of course you may well have some compelling reason to shoot for something different, but most modeling software shoots for .707 as optimum for sealed. Way back in the day when I ran sealed I preferred a little closer to 1.0.

Hispls, thx for linking the modeling (A picures worth..u know) all the effort, time & patients dealing with a random. And 2 everyone else who've made me feel welcomed.

For comparisons sake, could you also post the graph for what the box was doing originally, b4 we modded the port?

Lastly, what would a sealed box at 1.125 ft3 each (JL sealed spec) look like?

I just think it's bad as.s how if you know how to work the program, that you can model manufacturers specs for both sealed & vented on a graph, then overlay what YOU think would work better, then sit back and take pride in the ability.

Thx man.

Sealed box is pretty forgiving on small changes, a smaller sealed would just push things to the right a little, slightly steepen the slope, and possibly give you a little bump where the curve hits the zero line.

Smaller ported tuned low (where you started) picture adding a narrow hump around 26hz into the sealed box plot. This is exaggerated by your cabin's resonance (mid to high 50hz range) giving you a plot that looks like a two humped camel which I can say from experience sounds absolutely awful.

I run winISD on a virtual machine on my Linux laptop so it's rather a chore to boot up. I may or may not have time to mess with it and save/upload the pic tomorrow morning while I'm having my coffee.

Win ISD is pretty easy to use really, just be careful to check your units (cubic feet vs. liters) as you input things. The ONLY specs you really need for this are Qts, Fs, and Vas. From there after you've done a whole bunch of them you get a pretty good idea of what changes to size and tuning will do to change the shape of your graph. Once you've seen enough and tested the boxes real-world you get a pretty good feeling about what to expect.

Location and positioning of the subs/port in the vehicle is dramatic. Once again you're running "voids warranty" power to those subs so risking running into mechanical limits isn't unexpected. You are fortunate that loading those subs down firing keeps them under control.