JBL 2226 in a 145 litre sealed box - no kick even after eq

[Texas]

So the ply box is built, braced and damped and looking good.

I have eq'd to make up for the roll off starting at a 100 Hz.

The result is boring and has lost all the slam and dynamics that I know to be the capacity of the JBL 2226.

I knew this was a risk going sealed but still thought it was worth a try prior to going ported.

So ported it will be but where?

As the 42 kg boxes are on lockable wheels I am thinking of placing the ports facing the floor?

There is about 5 cm gap to the floor is that enough?

Also do I really need to tune the ports? Looking at some of the JBL designs it looks like more airflow is better then less.

These elements are so stiff and when I had them in a horn system prior they rocked!

The mid range will be an JBL e100 http://www.jblproser...s/e110-8-16.pdf and a Heil ESS as the tweeter.

There are also two subs.

Edited May 28, 2012 by Texas

[Paul Spencer]

2226 in a 145L sealed is about 11 db down at 40 Hz with about 86 db @ 1w.

Your box is probably too large. 2226 is optimised for sensitivity over extension, and also for a small box. So it wants a smaller box tuned higher than you might have in mind. For example, 65L tuned to 50 Hz gets you to 60 Hz. Or 82L tuned to 51 Hz is -3 db down at 55 Hz. Now if you trade some sensitivity you could tune your 145L box to 40 Hz. You give up 2 db sensitivity and get an extended bass shelf, which is 3db down at 43 Hz.

There is about 5 cm gap to the floor is that enough?

Not really. It will extend the port length and also potentially add turbulence if you have high enough velocity in the vent.

Also do I really need to tune the ports?

You really need to have your design figured out before you build! Emphatic YES to tuning it!

Better to have no port than one tuned inappropriately. There is a strong connection between box volume and port tuning, both depend on each other. Fortunately you can make this work if you tune low, I'd suggest 43 Hz.

Looking at some of the JBL designs it looks like more airflow is better then less.

Yes - this reduces velocity in the vent and keeps port compression and turbulence down. An unflared vent can chuff audibly at around 7 m/s. In your box that means 4 x 10cm PVC vents, each 33cm long. 60w input yields 7m/s in the port and 111 db @ 40 Hz. Given that is what you would do if it were a sub, but given that it's a woofer rather than a sub, this is probably less critical. But you are right, port area matters.

[LogicprObe]

I'm confused.

Is it a sealed box or not?

[A J]

It was - now it isn't

[Texas]

Clarification - the box is built to be 5 cubic feet as per JBL specs for a ported box. Prior to making any ports I am testing it as a sealed enclosure. Thank you Paul. So I am looking for flared ones placed either on the front or on the back as the 5 cm floor gap will not be enough in height. Will 7 cm do the job in conjunction with flared ports?

Edited May 28, 2012 by Texas

[coppinger]

How do you intend to tune the ports?

Have you got a signal Generator and a good multi-meter ?

[Texas]

I was going to try to find ports that can be adjusted (flared) and start close to what JBL use in there boxes.

If the frequency becomes 43 or 50Hz does not matter so much as the subs will do the rest.

Looking at the JBL ones it looks like they just make sure that there is enough airflow and then cut off the sub frequencies to avoid overextension.

Will that work?

[Paul Spencer]

Your box is quite large for that driver, so you should be tuning it at 40 Hz. If you tune higher, you will get a peaky bottom end because the big box makes a higher tuned port be too efficient. With a sub running below I'd tend to either run it sealed with just a little EQ to perhaps get to 80 Hz, or go for a smaller vented box and settle for 55 - 60 Hz extension.

If you are measuring your final outcome, then you could use an adjustable port and try a few options. However, if you are doing it by ear I would simply tune to 40 Hz which looks like a pretty safe bet.

[audible1]

Is this speaker for stage use or home hifi?

Interesting use of pro drivers.

I'd like to have a listen sometime.

Greg

[Paul Spencer]

It's becoming much more common in DIY. Some of the better pro drivers are very well designed and offer great bang for buck. I use a B&C 8" mid. It costs about $100 and has similar distortion performance to a Scan Speak Revelator, one of the best hifi drivers out there, which costs about $350. The B&C is about 6 db more sensitive, so you need four of the Revelator to keep up. $1.4k + shiping! Outch! Pro drivers are effortless at high levels whilst in some cases being also cheaper.

[Texas]

Home hifi : )

[Texas]

Your box is quite large for that driver, so you should be tuning it at 40 Hz. If you tune higher, you will get a peaky bottom end because the big box makes a higher tuned port be too efficient. With a sub running below I'd tend to either run it sealed with just a little EQ to perhaps get to 80 Hz, or go for a smaller vented box and settle for 55 - 60 Hz extension.

If you are measuring your final outcome, then you could use an adjustable port and try a few options. However, if you are doing it by ear I would simply tune to 40 Hz which looks like a pretty safe bet.

Thanks Paul - So for 40 Hz I need approximately 4 adjustable ports about 10 cm wide and 33 cm deep. Any chance I can make it two wider ports?

[Paul Spencer]

100mm PVC is cheap and easy to get. You could put four down or rear firing and cut a little roundover flare with a router. It doesn't have to be as pretty that way, velocity stays down so you can get away with less flare, and they aren't too long.

Yes, you can have less area and that means shorter ports, but the velocity goes up and aerodynamics are more important in that case.

Circular ports are a pest. I tend to do rectangular slot ports, no need to cut a circle with the port fitting accurately.

[georgepapa]

I would suggest doing everything strictly by manufacturers reccomendation and that throwing a driver into any nominally large box will only reap floppy weak bass from even the most robust drivers.

Bass kick is not a quality derived from the driver. it is a symbiotic effect achieved by combing optimal parameters of box volume, stuffing and port tuning. Also you cannot induce kick into that weak floppy bass by the use of eq.

The low qts and high fs of this driver make it totally unsuitable for sealed or acoustic suspension.

If you have a look at the parameters for a vented enclosure. What you have is a way over sized box event for vented design.

Have a look at the applet calculations for a bass reflex attached below. You should really be looking at an enclosure of around 96 litres with precise port dimensions.

Then you will get your kick.

mh-audio.pdf

[Texas]

I would suggest doing everything strictly by manufacturers reccomendation and that throwing a driver into any nominally large box will only reap floppy weak bass from even the most robust drivers.

Bass kick is not a quality derived from the driver. it is a symbiotic effect achieved by combing optimal parameters of box volume, stuffing and port tuning. Also you cannot induce kick into that weak floppy bass by the use of eq.

The low qts and high fs of this driver make it totally unsuitable for sealed or acoustic suspension.

If you have a look at the parameters for a vented enclosure. What you have is a way over sized box event for vented design.

Have a look at the applet calculations for a bass reflex attached below. You should really be looking at an enclosure of around 96 litres with precise port dimensions.

Then you will get your kick.

The box is built in size to JBLs specs for maximum low frequency tuning. At 96 liters where will they drop off?

[georgepapa]

Okay you can try as suggested to vent the enclosure to 40hz . But with this loading you're gonna get a lot of ripple in the upper parts of the bass and it wont sound as fat and tight as an optimum enclosure though you will get more very deep bass.

In such a design you're probably better off crossing over to the satellites as low as possible, even as low as 60hz. I would say that the application for JBL's recommended enclosure volume is a PA sub bass where full range line arrays or two ways monitors are already providing the bulk of the audio spectrum and much of the bass .

You could always just build in a partition to reduce the enclosure. From the frequency response these drivers look to have good response up to 1000hz and could easily be used in a three way. For them to integrate properly with your mids you would have to aim for a more conventional loading in the region between 80 and 96 litres.

[georgepapa]

The box is built in size to JBLs specs for maximum low frequency tuning. At 96 liters where will they drop off?

With this volume you should get about -3db at 50hz

[Paul Spencer]

On my blog you will find a couple of articles on WinISD (you can search from within the blog), which is a free program, easy to use, for simulating a box like this. You will see what we are talking about.

[Ando]

If the JBL volume/tuning isnt working out for you you could ask Wayne Parham of Pi Speakers for some advice: http://audioroundtable.com/forum/index.php?t=thread&frm_id=33. He has a lot of experience with this woofer and always seems happy to help out DIYers.

Cheers Mike

[Paul Spencer]

Of course, let's not forget that the lack of kick could have multiple causes - might not be the actual speaker itself, but the way it is integrated, or some room issues. When you talk about "kick" most people think of the speaker itself, but I have found that dealing with room modes can actually help you get that kick. Where do you experience kick the most? I would say it's probably at a live gig with an outdoor setup - no room at all, no studio compression on the music, bass dialed up with active pro subs and no room decay issues. When I first added bass traps and started damping the bass in my room seriously, my first thought was that I was getting that type of outdoors bass with kick sound. The bass was stopping faster, better decay. I found I could turn it up and get it clean without bloat or boom, the end result being more kick. Kick might also refer to getting good transient response, although in so many situations the room and integration may well be a bigger factor. Unfortunately there is no one definite answer.

BTW, I see you have Rythmik subs. Up to about 80 Hz, it's not easy to beat them, they are very clean and dry, but you won't realise how good they are until you hear them in a treated room and very well integrated. For quite some time I thought I could hear some upper bass boom from them, but it was the room.

[Texas]

Oh yes the subs move this house as much as you want them to.

Had to change to 6 mm laminated glass in my old shop front windows.

I am mac based so I found this calculator;

http://www.lineartea...=ventcalculator and tuned to 50 hz it looks like this:

Thinking of use these....http://www.jaycar.com.au/productView.asp?ID=CX2684

Now it is just placement left to decide.

Two at the front and one towards the back?

All three pointing downwards?

Want to spread the bass evenly in the room...

Edited June 1, 2012 by Texas