Sitting Room Build: Jack 12 Lite

[HugoMack]

I've reset the freq for he EVMs to their resonant freq - 55Hz. Seems sensible.... and they're a full-range-ish speaker so should be fine...?

[Bill Fitzmaurice]

I've reset the freq for he EVMs to their resonant freq - 55Hz. Seems sensible....

Excursion at Fs is minimal, so that's the last frequency you'd want to use. The cone will hardly move at all.

[HugoMack]

So your suggestion would be...?

[Bill Fitzmaurice]

So your suggestion would be...?

30Hz. That gives you maximum excursion with minimum voltage.

[HugoMack]

Sorry Bill. I would have been really appreciative if you'd simply told me what I should be doing here. Have I annoyed you? No, forget that last, and never mind. I've reverted back to 30 Hz sine wave as with my Jack Lite 12's. I'm sure Dr Bunter will help once Australia wakes up.

We crossed over. A great minds think alike!

[Grant Bunter]

Tis no problem mate,
Bill's responses are often brief, and very to the point.
Don't read into it what isn't there!

The only thing you need to worry about is thermal limit/Xmax, and if 8-10V might be shoving a bit hard...

[HugoMack]

Thanks Grant. I backed it off to around 5 volts which seemed about right.

Maybe Bill thought I was trying to be clever with his very clear instructions over breaking in for the Jack Lite. I'd spent several hours waiting for omething more specific from him - hoping for wisdom, then my frustrated message and his crossed over...

But next job is fitting the woofers, then..... testing time!

[HugoMack]

Well.... I've cranked them up, with a little messing around with crossovers and piezo connections.

I set them on poles as below, with me in the middle about 2 metres from each ear. And it was like very loud headphones! I have Ultrsasone Pro 550's so that's quite something..., Quite amazing actually.

I haven't yet taken off the backs and grilles again to leak test, but as the backs are seriously sealed up with wetsuit-type draft excluder tape I can't think they will leak, and the rear chamber is vented through to the front anyway, so I don't suppose there's a pressure problem as with subs? I can't hear anything untoward, but I will do the checks.

I haven't got any good pics yet, but here's a couple. I'll be adding the missing piezos soon, as I think they will come into their own when hooked up with subs!


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I'm going to make the subs next. Will the Jacks benefit from a Driverack or similar rack unit processor - or do these only really come into their own when using subs? I've not used anything like that with my current JBL systems.

Plus I'd like to thank you all for all the hugely helpful advice and encouragement. Particularly Jools for those vital polystyrene balls! And Leland Crooks for being so helpful. If anyone is interested in the details of importing from the USA, give me a PM. In UK, Blue Arran have the speakers you need.

[HugoMack]

PS: am getting some padded covers made. will post pics and URLs when they come.

[Tom Smit]

Very good!



Run a 30hz tone through the Jacks, at about 10 volts. Grab a length of hose, one end to an ear; the other end moving slowly along the joints/cover. Any air noise is a leak.

[Grant Bunter]

Yay! Looking great

I'm going to make the subs next. Will the Jacks benefit from a Driverack or similar rack unit processor - or do these only really come into their own when using subs?

There is a couple of benefits to using something like a Driverack on full range cabs such as the Jack series.

The first is that you can limit voltage to them. Protection.
The other is that, if you don't need the absolute lowest possible bass out of them, you can set a HP. For example, instead of say 40Hz without processing, you could set a HP of 50Hz with processing. Again, protection.

A number of commercially available self powered cabs now have internal processing and limiting to achieve the same goals, so, why not?

Since your plan is to build subs anyway, the real mileage is in having it early to start learning how to use it, so that when your subs are built, programming is a breeze.

I've not used anything like that with my current JBL systems.

You're not alone.
It hasn't been said for quite some time, but used to be said often enough when I first got to the forum:
Those who use direct radiators should also be limiting/setting HP/LP's. I know a few people who do, and a lot of people who don't.
It's the ones that don't that blow their drivers...

[HugoMack]

Does anyone have preferences over the Behringer and Driverack PA2 - and are there any other reasonably-priced options?

I like the idea of the mike measuring room response, and being able to adjust using an iPhone. (The Behringer X32 rack is similarly attractive.). Is the reality as good?

[HugoMack]

Many thanks Grant. I'm going to take your excellent advice. These cabs sound so good that it's mad not to upgrade everything else in the system.

But the DriveRack PA2 (the new model), seems to be very expensive here in UK - best part of £500 - more including the condenser mike.

BTW I really like your "ute". Specially the West Coast highway Kenworth-style exhaust? DO you have living quarters in there too?

[Grant Bunter]

But the DriveRack PA2 (the new model), seems to be very expensive here in UK - best part of £500 - more including the condenser mike.

Yes, I know, none of it is cheap for the rest of us in the the rest of the world.

There are at least a dozen different variants/brand names of the DSP that you require in the marketplace, in multiple price brackets. Do your research and keep an eye out for possible bargains.

BTW I really like your "ute". Specially the West Coast highway Kenworth-style exhaust? DO you have living quarters in there too?

I have carpet through 3/4 of the tray. Add some packing blankets and some bedding and it's suddenly a crash pad as needs be. The exhaust is standard lol, chunky piece of pipe though.
I've only had my "ute" for a couple of years, but it's already done 20 000K with me and heaps of gigs, both PA and band. Tha bank still owns it...

[HugoMack]

I just received some covers I'd had made. Not for the subs - when I make them, but the Jacks deserve protection I think.

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PS: someone asked if I was going to use these with the AXE FX2. I've now tried them with it, and they really do make it sound amazing with cab sims. I'm tempted to stop using backline even in small venues...