First Build - A Single JBL 804 16" AutoTuba

[njolliffe]

BOWLINE!

Haha, took me ages to figure out what you meant by this. You'd never have guessed I was a scout once. It's just one of those things you don't forget.

Nice. The gasket looks good

The JBL gasket is fine by itself in my builds

Hmm two contradicting comments. Figure I will leave it for now and check for leaks later. Can easily take it off if needs be.

Cab is going well still, got the last panel on and I'm working on the access cover before fitting the side as there is more room. (sorry for lack of pics)


I have also been looking at amplifiers as mines old and has no variable x-over.
In my quest to be a cheap skate I found this.

http://www.roaduserdirect.co.uk/index.p ... uct_id=142

What do you guys think? I can get it new for £35 delivered.

Seems to have the variable LPF that I need and will put out 200w mono at 4 ohms so I'm guessing around 150-75 ish at 6 ohms under horn loading. (is there a way to work this out more scientifically)

I have been looking for an amp which can band pass as I read somewhere you don't wanna be sending less that 20hz to the AutoTuba but I can't seem to find one. Even £200+ amps seem to be either HPF or LPF not both at once.

Is this something I should worry about (I'm into dubstep, dnb where sub 20hz is more common)
How would I set the HPF to 20 ish hz if neither the amp or HU have a setting to do this?

Thanks in advance for your help

[Ryan A]

Very few car amps have high pass settings, and typically its not required for car audio installations unless you're running close to maximum output.

If you want one with both high and low pass, the JBL gto3501 amplifier has it and it puts out 225w rms at 4 ohms, so probably around 150 @ 6 ohms.

Not sure if its available where you live or if its in your price range but it seems to be a good fit spec wise.

Otherwise the amp you were looking at would probably be just fine too if its much cheaper.

If you need lots of 20hz extension, a 12" sub in a ported, sealed, or bandpass box is going to have more output down there, whereas the AT excels from about 40 on up.

[bassmonster]

If you need lots of 20hz extension, a 12" sub in a ported, sealed, or bandpass box is going to have more output down there, whereas the AT excels from about 40 on up.

Or...a Table Tuba.

[Ryan A]

If you need lots of 20hz extension, a 12" sub in a ported, sealed, or bandpass box is going to have more output down there, whereas the AT excels from about 40 on up.

Or...a Table Tuba.

Right...I was assuming not everyone has an suv to carry one in . Sure would like to hear your TT in car though I bet its epic.

[Zack Brock]

I was a bit annoyed as I found the jigsaw blade tears at the ply causing these chunks to be ripped off.
I found it helps if you score the wood with a knife before cutting.

Putting masking tape on one or both side of the cut helps prevent splintering when cutting with a jigsaw, circular saw or table saw.

[Ryan A]

Nice. The gasket looks good

The JBL gasket is fine by itself in my builds

Hmm two contradicting comments. Figure I will leave it for now and check for leaks later. Can easily take it off if needs be.

The comment I made about the gasket came back to bite me. On my latest build I didn't sand the driver baffle smooth and installed a JBL driver and had slight leaks near 4 of the 8 bolt holes. Attached some rubber weather stripping (stick-on type) on top of the gasket already on it, and now its airtight all around. Passed the hose stethoscope test.

[njolliffe]

Happy Days people, the AT is now finished, well from a functional point of view at least.
I am not sure if this is good or bad, as I don't want to spend time working on it to finish it off when I could be listening to it

The comment I made about the gasket came back to bite me

I'm glad l I left my homemade gasket in place as so far it seems to be OK.

I am still undecided on the finish as its going on the backseats (too big for boot).
Thinking about painting or carpet but I know you guys hate that...
Any suggestions? The dura cab stuff I don't think is suitable as it'll scratch up the leather.

Anyways, here are some photos and after is a little review.

Side shot

Horn Mouth

Side shot

Other side - Note window

Window - 10mm acrylic

Thought I'd add a window as it seemed a shame to hide all the cool innards.
Also its car auto sound, so a clear perspex window makes it louder....


Still undecided on an amp to run it all off. The JBL gto5501 does look good but its also just shy of a hundred pounds. I don't know if having a high pass is worth this much money.
I could buy the cheaper edge amp and another driver (if I do blow the current one) and still have money left over for the price of the JBL amp.
From what I've read you only have to worry about sub 20hz at stupid high volumes anyways?

O yeah, TT is way outta the question, the AT barely fits as it is.

So far using my old 'who knows where it's crossed' amp I have hit peaks of 10v and this is already mental. I think of it as demonstration/play volume, I'm pretty certain my ears would be messed up after an hours journey at that volume.

The thing I have found most impressive is the way the sound is 'sealed' somehow inside the car. You can be blasting music out too loud for comfort inside and outside its barely audible, except the few rattles and things falling off the car.
As soon as you open the door though, those low, clean bass notes hit you and it carries a long way.

I have also used it in the house watching Tron (so far) and for listening to a few songs. It's only being powered off the altec lansing sub amp but its plenty loud enough. Music and low bass scenes in the film were rattling pictures, windows and plates across the room at over 4/5 meters. All that whilst under 3 volts!. In fact my landlord said I had to be careful as the windows are over a hundred years old and he was fearing for their safety!
Obviously the bass was far too overpowering for the piddly little satellites and set up all wrong, I think the X-over in the altec unit is around 150-75hz ish to the mains so that peak in the db curve from around 100+ was pretty evident. Had to move the sub from the corner round the room to 'unload' it to a more balanced level. (there's no bass control on the vs2621)


I also really want to add a video as there are few good ones of the AT but the stupid Samsung S3 mic is terrible.
Any suggestions for a mic? The samson go mic seems to get good reviews and is cheap but I wonder if the bass will destroy it? Recons it can go to 20hz? http://www.samsontech.com/samson/produc ... nes/gomic/


Overall I am very pleased with the AutoTuba so far and looking forward to getting it properly set up. Nice one Bill on an awesome design and thanks to everyone for your advice.

[Ryan A]

Nice build!

The high pass is not a requirement in the plans as far as I'm aware...you'll do fine without it provided you're not listening at crazy loud levels. I'd be more worried about it if you had the mcm driver.

[Tom Smit]

Good job!
But your not finished yet. Get it painted!

10v is half way to 20v, which means only 3 db more.
Record at low volume, and listen to the recording. If it's good, then great...pass it on. If lousy, do it again at a lower volume.

[Gregory East]

The difference between 10V and 20V is more like 6dB output.

[Bill Fitzmaurice]

10v is half way to 20v, which means only 3 db more.

6dB. Doubling voltage quadruples power.

[Tom Smit]

I stand corrected.

[njolliffe]

Hello again,

So I decided to buy the jbl gto 3501 amp that was recommended as it seemed pretty good, especially as it has the hpf.
It has arrived and I'm getting it set up but I had a quick question I was hoping someone can help me with.

My HU has a stereo L+R RCA out and the new jbl amp has a stereo L+R RCA in. I am currently running a stereo to mono rca cable from the HU (stereo out) to my old amp (mono in). I am assuming this is OK to do even though the amp is expecting a stereo input? I am just worried about loss of signal if the mono is summing anything?

Anyways, I guess the answer to the above will help me to decide if its worth buying an rca stereo to stereo cable.

Thanks

[Ryan A]

I would want the amplifier to sum the signals...but the one you have should at least work.

[DJPhatman]

My HU has a stereo L+R RCA out and the new jbl amp has a stereo L+R RCA in.

That is what you should use. It will do a better job than a stereo-to-mono adapter cord.

I would want the amplifier to sum the signals...

+1