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Discussion Starter #1
I searched but there were so many ported sub threads I could not find threads about porting Midbass.

If I were to build a door enclosure for Midbass, in this case JBL660GTi. Using JBL specs the sealed enclosure I get from WinISD is .14 ft3. But the F3 is 100 Hz. This seems very high. Making the box bigger actually seemed to make the F3 higher.

If I model ported I come up with is .325 ft3 61 Hz tuning freq which is about the F3, 2.75” Dia x 10” port.

The recommended sloped box is 14.3” x 9.5” x 6” tapering to 0”. This would seem to be possible, looking at my doors if I remove the bottom half of the door card and replace with the enclosure.

I know stock answer is to try it. But what are the drawbacks to a ported Midbass in a car?

Per the JBL Manual
The 660GTi woofer may be used in an infinite baffle or in a small sealed enclosure
with a volume equal to or larger than 1/8 ft3. The 560GTi woofer may be used in
an infinite baffle or in a small sealed enclosure with a volume equal to or larger
than 1/12 ft3.
 

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The real drawback is in the transition between midbass and subbass. The group delay is typically larger and the phase shift is larger as well. So the transition and "bass up front" illusion is tough to get right. Having said all this I am working on ported kicks right now. It will be a while but I will report results in my build thread.
 

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Discussion Starter #4
Cool I will check back with you guys. Per WinISD at 60 Hz there is 10.13 ms group delay and the phase shift is 180 deg. At 250 Hz it drops to .42 ms and 37 Deg. I see this could be a problem. But I would expect home speakers suffer from these same kind of problems.
 

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But I would expect home speakers suffer from these same kind of problems.
But typically in home speakers it is the lowest range speaker that is ported. This eliminates the integration issue (until you add a home sub to the mix).
 

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I did alot of research on this when putting in my JBL midbasses (2204's) in my car. On Langsing Heritage, the closest thing to a JBL Pro Audio website that there is, they run 12 and 15" midbasses ported as a matter of practice. From what I have read on group delay there doesn't seem to be a solid agreement as to how much is acceptable. At lower frequencies more group delay is allowable. But I am certainly not an expert on this.
 

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I think you can match the subs TA/phase to it and be ok, IMO FR is more important but that is just me. Not sure at 60Hz even it is that big a deal.

There are threads on here about ported mids/midbass for sure, how you find them I'm not sure lol.

I plan to do IB midbass and not have this issue or an enclosure lol, but its because of depth.
 

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Don't worry about group delay because of the port. You'll do all the real integration with the EQ, crossover and time alignment anyway. If you have enough power and EQ, there's really no need to use the port. Just change the Q of the crossover (HP) or add the bump with the EQ to fill in the rolloff. Just as valid as the port and easier to fine tune.

Sorry, you sent me a PM on this and I got sidetracked halfway through my response and then SOMEONE unplugged my PC. Damn Basset Hounds...
 

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Working on ported kicks to, I think it wil rule.
Crazy idea!

Cool I will check back with you guys. Per WinISD at 60 Hz there is 10.13 ms group delay and the phase shift is 180 deg. At 250 Hz it drops to .42 ms and 37 Deg. I see this could be a problem. But I would expect home speakers suffer from these same kind of problems.
No, they do not.

Ported works very well for home systems because these speaker cabinets with 6.5" or 8" drivers can use the help in the 30-60 hz range, and the enclosure sizes are large enough to ensure smooth response and efficiency.

I think the bad rep ported gets for being "slow" or "boomy" is all of the car audio sub enclosures that are just too small. 90% of a ported 10 or 12 in a car is smaller than a home audio enclosure with an 8" woofer.

Ported, horn loaded and similar type designs work well in home. And none of them need infrasonic filters to prevent the woofers from unloading.

But typically in home speakers it is the lowest range speaker that is ported. This eliminates the integration issue (until you add a home sub to the mix).
Lowest range speaker? As in cheapest?

Sure you see that, but you also see ported in expensive setups too. In fact, I don't think I've seen too many sealed designs except for small studio monitors/bookshelves were low frequency extension is understood to be compromised or where the woofer was larger than normal (~12" - 15").

Adding a home sub should be avoided in most cases. For the home audio hi-fi experience, especially the "audiophile" music I hear at these meets, it is completely unnecessary. :)

BANDPASS THAT **** :p

Kelvin
Finally, the right idea in this thread. :D

Ok, here's my problem with ported midbasses in cars:

Where are you going to put them?

I've joined that exclusive club a few years back of those that have attempted sealed enclosures for midbasses. I had an enclosure probably around 0.3 - 0.4 cubic foot for a Morel Elate 6.5", and it was too small. Sure that's what a "low Qts" driver would want, but the reality is that all the low end extension of a big car door is gone....the rich harmonics that is.

It sounded tinny to me, sort of like crossing a woofer over at 100 hz instead of 60. If you happen to LIKE that sound, then by all means build a sealed enclosure for the woofer. You'll get a nice hump and get even more detail....

However, if you don't, bad idea. And as such I learned an expensive lesson.

As far as porting, I'm not sure how big an enclosure you will need but I'd imagine you'd want a nice size....I've seen some crazy pics of installs of a rebuilt door that was essentially all MDF. Perhaps something like that could work, but how many on here are ready to go through that level of effort?

I doubt that you can do that sorta thing in the kicks. So where is this gonna go?

I think if you could build a sealed enclosure in a car door about 2 cubic feet or so then maybe the conversation can begin. To simplify the bass reflex concept, I would go with a passive radiator mounted on the same plane as the woofer. Assuming the PR on the same plane would work, then this seems a lot easier to tune and get right than a tube.

Also in order to reduce enclosure size, I'd probably go to a 5.25" woofer over a 6.5".

But at the end of the day, you go through this herculean effort to make it work and it works great, let's say. However, the SPL and bass is still going to be less than two woofers IB. :D

Maybe the bass reflex is better in eliminating rattles or what not. But I gotta tell ya, my sealed enclosure wasn't perfect either. I don't think there is such a thing in car audio.
 

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I wanted a lot more low end from the speakers I am using like in a home application, I would double the enclosure size and tune much lower.

However for the range I am playing the speakers, I can get away with a smaller enclosure tuned higher. This current enclosure I am working on has 4dB more output between 60 and 100 hertz over sealed...even with a 4th order filter high pass applied.
 

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The group delay of the crossover will probably have more of an impact on the total group delay of the signal than sealed or ported would.
 

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I wanted a lot more low end from the speakers I am using like in a home application, I would double the enclosure size and tune much lower.

However for the range I am playing the speakers, I can get away with a smaller enclosure tuned higher. This current enclosure I am working on has 4dB more output between 60 and 100 hertz over sealed...even with a 4th order filter high pass applied.
Which driver you want to port in the center? X57? Do you have specs so I can try to model it too? Thanks

Kelvin
 

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SDX7. Optimum ported is like half a cube tuned to 35. I'm at .25 cubes tuned to 45.

I have the T/S for the xS65, which is pretty similar to the xS57. I was going to send Erin the xS57 I have to be Klippel tested.

I have modeled the xS65 before...it was a tiny ported enclosure because of it having a pretty low Q. Something like .15 cubes tuned to 90.
 

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Jimbo, I would decrease your port size to 2". There isn't any need to run almost a 3" port on a 6" speaker. I am going with a 1.5" port on mine.
 

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I'm surprised that no one has mentioned the use of a passive radiator or aperiodic membrane. More difficult to tune, but I suspect it would be easier to build.

Sent from my ADR6400L using Tapatalk
 

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Nope on both.

A PR would have to remain vertical, you can't lay it down...and if you have the surface area for a drone cone, you would be better off using an active speaker. PRs make sense for subwoofers, not so much midbasses since you don't need or want to tune them super low.

And AP would have to be vented to another space. Not to mention tuning the AP mat takes either time to do it the old fashioned way or money to use a WT3. Generally AP systems have less output than sealed.
 

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SDX7. Optimum ported is like half a cube tuned to 35. I'm at .25 cubes tuned to 45.

I have the T/S for the xS65, which is pretty similar to the xS57. I was going to send Erin the xS57 I have to be Klippel tested.

I have modeled the xS65 before...it was a tiny ported enclosure because of it having a pretty low Q. Something like .15 cubes tuned to 90.
I like the group delay of a the SDX7 in a 0.4cuft tuned to 40Hz (2" round 11.71" long) HP set to 50Hz 12dB/oct slope
The XS doesn't look too good ported coz it asks for a really small enclosure (0.07cuft) tuned high (80Hz-90Hz)...

Kelvin
 

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Ported FTW...but I don't know by how much though.

I think it would win more using really low XO points on the bottom end with shallower slopes or no XO on the bottom end. With a sane XO point I think the benefits would go away.

Was a neat experiment where I had a known volume to work with and a driver that would work really well in that space. I don't know if I would do it over though.
 
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