Bass Port Length and Shape for a JBL 2213H DIY Project

[Thomee]

Hello friends,

A while ago I bought an immaculate pair of JBL 2213H for a very fair price. I have always heard that these woofers produce a very clean and deep bass in large enclosures. So I decided to build a pair of speaker out of them. I got a pair of Morel TSCM 634 midrange drivers and a pair of Aurum Cantus G1 Ribbon Tweeters from Parts-Express. After two weeks of measuring and building xo, I managed to get a very flat and surprisingly fantastic sound from them. The only issue is that the woofers still play bass frequencies of 100-50Hz a little too loud for my taste. The test cabinet I have put them in right now were built for a DIY JBL L100T (ten years ago or so). I guess they are like 60L or maybe a little bit larger.

According to WinISD a volume of about 100L with a long port of 26" (length) and 4" (diameter) should make them sound right. So I have decided to use PVC swage pipes and use 90-degree bends to make the port fit. Please see the drawings attached.

Any input about what I am going to do is greatly appreciated. Do my calculations make sense? Is the port OK? How about, if the vertical end of the port goes even higher than the woofer? Should I be worried about any kind of distortion or resonance from such a port?

Please see the attached pics.
Thanks.

 

[homebrew]

Did you model different diameter ports? Multiple ports? Don't like the idea of a 26" port.

 

[tom3]

Used to test this with a battery. Tap the battery on the woofer's input and listen to the sound differences with different port size and length. These days you could probably just dial up a low Hz tone or a sweep on the phone/laptop and adjust the port to suit.

 

[homebrew]

Suggest you do a search on how to tune a ported woofer box. You'll need a multimeter and a signal generator that can be downloaded for free. The process is pretty easy but it will involve adjusting the length of the port tube.

 

[Thomee]

Hi,

Thanks for the suggestions. I am in process of building the cabinets. Once they are ready I am going to do tests. Right now I am working with the woofer's parameters and the simulations.

 

[toddalin]

Hi,

Thanks for the suggestions. I am in process of building the cabinets. Once they are ready I am going to do tests. Right now I am working with the woofer's parameters and the simulations.

They do sell adjustable length port tubes.

 

[painttoad]

slot port.

 

[z-adamson]

According to zilch the 2213h and 123a were best suited to large sealed, acoustic suspension designs. 3 cubic feet to 5 cubic feet produced best results. He did this and posted graphs to show it.

An acoustic suspension driver in a small ported enclosure will be boomey.

Here is the driver in various enclosure sizes showing response

 

[z-adamson]

This…

 

[Thomee]

Thank you for all the info. I am planning to build a 3.5 cubic ft (100L) cabinet tuned to ~25Hz. I can try blocking the port and see if it gets better. I hope that works.

 

[z-adamson]

Take a look at the ts parameters for the 2213h….it really is an acoustic suspension woofer.

 

[Thomee]

This Sunday, I finally built the front baffles. Here are some pics:

 

[donprice]

Very nice looking driver set

Easy to test with no port if the plan was to install it in the rear baffle. Trust Zilch on this one

 

[Thomee]

Very nice looking driver set

Easy to test with no port if the plan was to install it in the rear baffle. Trust Zilch on this one

Thank you. All the three drivers are brand new. Even the 2213H. They were left in a shop as demos, never used.

Yes, the port will be in the back. Question: if I install the port then block it, it will be sealed, right?

 

[z-adamson]

Yes, the port will be in the back. Question: if I install the port then block it, it will be sealed, right?

Yes, however if you block it you will want to add lots fiberglass insulation to the cab. If the port is unblocked, you simply want the walls of the enclosure lined with fiberglass.

 

[wiredbecker]

Zilch and I ran my 123A Econowave bass bins sealed and the cabinet size was quite small under 1.2 cubic feet. Bass response was adequate for my purposes. I ran these with waveguides on top at Wired Magazine offices for many years!

 

[GordonW]

I have an alternative suggestion.

I would be inclined, to thickly line the box (almost fill it with fiberglass- thick lining on all the walls, with just a small open area in the middle), and use a passive radiator (such as this: https://www.parts-express.com/Dayto...XqmVZWi01csk8fo9oyd9WkUaFiIc68eVQ1XoTmSApjQ5A ), INSTEAD of a port.

It will go significantly lower than a port in a 100 liter cabinet- close to 31Hz f3, as opposed to about 36Hz for the tuning above, and 42Hz sealed. And, it's flatter response in the passband than the port. You will need to add some weight to the back of the passive radiator, but not much- you want to reduce the PR's own resonance, from 18.6Hz to about 15Hz. Probably could do that just by ear- just tune it to where the bass is best.

The proposed port will take up a LOT of internal cabinet volume, that can be put back to use inside the cabinet, by using a passive radiator. That, plus the fact that PR cabinets tend to work well with lots of cabinet filling (compared to ports), means you can maximize the effective internal cabinet volume a lot better...

JBL did this themselves, back in the 1960s, with the 123A (same parameters as the 2213) and a 12" passive radiator, in an even larger cabinet (about 7 cubic feet), for the C70/S70 Alpha/ Alpha II/ Alpha III speaker systems. Those would play into the 20s. VERY impressive bass. So, it's a known concept, to work well.

Regards,
Gordon.

 

[Thomee]

Hello friends,

It has been while... I got so busy with work that totally forgot about this forum.

I just wanted to complete this thread and report on the result of this DIY JBL 2213H project.

The end result is an absolute success. The sound is flawless to my ears. Full-range sound, sharp and smooth with very good bass and excellent mid and high frequency extension. The vocals, instruemnts... everything just come out so natual and effortless with good detail.

It took some effort to make the right xo for them.

The cabinet walls are two layered (3/4MDF + 3/4 multi-core birch) plus self-adhesive bitumen pads, and adequately braced.
The front baffle is also threated with 5mm Neoprine sheet (just like the JBL XPL200 cabs).
The internal volume is about 3.5 cubic ft. No port, ie. acoustic suspension.

The drivers are JBL 2213H, Morel TSCM-634, AurumG1 Aluminum Ribbon tweeter.

Please check out the photos also.

Thanks for all the feedback and help.

 

[malden]

Nice work ! They look great and I bet they sound better than any factory JBL with that woofer.

 

[Thomee]

Nice work ! They look great and I bet they sound better than any factory JBL with that woofer.

Thanks. JBL mostly use these 2213H woofers in 40L cabs tuned to 40Hz. The woofers are nice, specially with a good crossovers and on a tall stand. But below 50Hz there is sharp roll off.

My cabs are around 100L and sealed. It goes pretty low and very linear and clean. It gives superb bass. Very clear and full. The built quality of these drivers are superb. The cone, the bracing structure... everything first class.