BillFitzmaurice.info

Thank you both very much for your suggestions. I will definitely tinker with the settings tomorrow and report back. The hole is not in the chamber, it is at the opposite end of the mouth. Tomorrow I will go around the complete cab and fill any screw holes I see, regardless of whether or not I can feel air coming out.

Since this is the first AT I built, as well as using crappy wood, it did not come out as clean or neat as I would have liked. Next I will build another but use baltic birch instead and maybe try the TAT in a wider version and possibly a ten inch driver, we'll see what my trunk can accomodate

On a second note, would I see a bigger improvement in the low end and or SPL going with a 8 inch driver and a wider cab or a ten inch driver in a cab at it's minimum recommended width?

For HP filters what are you guys using? Most amps I have seen just have a subsonic filter on them but don't have the ability to do HP and LP on the same crossover.

To be honest, I don't have a HPF for my car audio, never thought it would be a problem. Could I be wrong?

digital_chris wrote:Could I be wrong?

Probably not. You'd only need it if you're pushing excessive low frequency content at stupid loud levels. OTOH if you're a typical 17 year old that's what you do.

Nah, but I do like my dubstep music and it does have some low content. How low, I'm not sure.

While your tinkering with the amp controls, also try reversing the phase of the sub (switch the + and - speaker wires around). Try it both ways, one way should sound louder than the other. I also agree with removing all bass boost, by looking at the size of your car, you'll already have around a 8db peak around 48-55 hz, you don't need another one at 40hz. Just use the gain to adjust your levels. Also play with the lp setting on your amp, because of the rising response of the autotuba, a lower setting (around 50hz) may sound better. Also what is the rest of the system ? HU, speakers, etc? Are you using a rca out to your amp, or using the high level inputs from your speakers? Do you have a way of highpassing your other speakers? Did you check for leaks with a 30hz tone? Something must be amiss, not clean on the kicks is the last thing I would ever say about my autotuba. I was listening to some tragically hip yesterday and the kicks literally feels like someone is sitting behind me kicking my seat. Even hurts my ams if they are resting on the armrests. Hopefully you can get it dialed in right.

CoronaOperator wrote:While your tinkering with the amp controls, also try reversing the phase of the sub (switch the + and - speaker wires around). Try it both ways, one way should sound louder than the other. I also agree with removing all bass boost, by looking at the size of your car, you'll already have around a 8db peak around 48-55 hz, you don't need another one at 40hz. Just use the gain to adjust your levels. Also play with the lp setting on your amp, because of the rising response of the autotuba, a lower setting (around 50hz) may sound better. Also what is the rest of the system ? HU, speakers, etc? Are you using a rca out to your amp, or using the high level inputs from your speakers? Do you have a way of highpassing your other speakers? Did you check for leaks with a 30hz tone? Something must be amiss, not clean on the kicks is the last thing I would ever say about my autotuba. I was listening to some tragically hip yesterday and the kicks literally feels like someone is sitting behind me kicking my seat. Even hurts my ams if they are resting on the armrests. Hopefully you can get it dialed in right.

I do have a phase control on the HU and if I swap it, it's not as loud so I kept it where it was. Bass EQ Gain on the amp is now all the way off and the filter is set around 75 right now, but I can try lowering it a bit. When I put hy head next to the mouth, it really sounds like some higher freq notes are sneaking through, hopefully it's just my settings and or music and not the cab...

The rest of the system is an Eclipse CD3100 for a head unit, I think alpine type S front and rears and I have RCA's coming out of my Non-Fade / Low output on the HU going to the amp. I don't have a way to high pass the speakers for now, I really think I should though because it sounds like they can't keep up even though I thought they sounded fine without a sub in the system, idk.

I didn't check for leaks yet besides that one I already found (screw hole on the panel opposite the mouth). Speaking of test tones though, a 35-40hz tone at 16 volts is SUPER loud inside the car, but 20 volts with music doesn't really touch it

One last thought. The sub is in the trunk and the rear speakers are in the rear deck with the bottom of them open to the trunk. If the sub is in phase with the mains, there should be no audio interference when the sub forcing air pressure against the bottom of the mains, correct? Sorry if I worded that wrong.

digital_chris wrote: One last thought. The sub is in the trunk and the rear speakers are in the rear deck with the bottom of them open to the trunk. If the sub is in phase with the mains, there should be no audio interference when the sub forcing air pressure against the bottom of the mains, correct? Sorry if I worded that wrong.

There is interference. At higher volumes especially (20volts) thats gonna be a problem. They might be in phase but the higher midrange freq will distort with the bass kicks, maybe thats what you described? They need to be sealed off airtight and highpassed, the shared bass reproduction will also muddy it up. You sure your head unit doesn't have a highpass?

Your HU has x-overs for your front/rear speakers, and for the non-fader out. It also has a parametric eq. You should check out your manual to learn how to set these.

http://www.eclipse-web.com/us/manuals/m ... 30360).pdf

Start by making sure your HU x-overs are set properly. make sure the X-over NF is set to upper - on, lower - pass and pick an appropriate frequency. Around 80-100hz should be fine. You can then set your x-over on your amp to the same (low pass) and same frequency. This should give you a 24db/octave slope, much higher slope than just using one x-over at 12 db/octave. That should eleminate the highs comming out of the mouth of the sub you mentioned. While your at it, set your x-over FR to upper - pass, lower - on at the same freqency you set for your non-fader out. That should clean things up tremendously and give you MUCH more clean volume on your speakers. For now, make sure your parametric eq is defeated and all tone controls are flat. You can play with these later to take out that peak I mentioned earlier. Don't be afraid to turn up your gain on your sub amp as far as you need too as long as the clip lights don't come on for more than a breif moment on the peaks. A slight touch of red barely noticable won't hurt anything, just stay under 33 volts. If you need too, your HU non-fader out has a level adjustment you can increase to give you a stronger signal.

I wouldn't worry too much about the speakers in the rear deck, free passive radiators What i would do however is remove the factory sound deadener between the rear seats and the trunk as this can and is designed to block low frequency pass though. The foam on your seat backs is invisible to freqencies below 80hz give or take.

Im still going to mention leaks again. Check around the driver, the entire driver chamber (no such thing as too much PL), as far as you can reach in the mouth, and ESPECIALLY the access panels!

As far as positioning your sub, make sure you have a good 6 inches clearance in front of the mouth and that the mouth is as close to a rear corner as possible. Sounds counter-intuative but having the mouth 6" away from and pointing towards the tail lights is louder than the mouth right up against the seat backs due to cancellations.

Thats all I can think of right now. Let us know your progress.

Well there you are, seems you have alot of control after all..

CoronaOperator wrote:I wouldn't worry too much about the speakers in the rear deck, free passive radiators

..no. There's alot of pressure in there and even powered, will still be modulated by the subbass and will distort the midrange accordingly, even more so without power. Get some of these http://www.parts-express.com/pe/showdet ... er=260-788 and seal them up with sanding sealer spray or resin. Highpass.

CoronaOperator wrote:Your HU has x-overs for your front/rear speakers, and for the non-fader out. It also has a parametric eq. You should check out your manual to learn how to set these.

http://www.eclipse-web.com/us/manuals/m ... 30360).pdf

Start by making sure your HU x-overs are set properly. make sure the X-over NF is set to upper - on, lower - pass and pick an appropriate frequency. Around 80-100hz should be fine. You can then set your x-over on your amp to the same (low pass) and same frequency. This should give you a 24db/octave slope, much higher slope than just using one x-over at 12 db/octave. That should eleminate the highs comming out of the mouth of the sub you mentioned. While your at it, set your x-over FR to upper - pass, lower - on at the same freqency you set for your non-fader out. That should clean things up tremendously and give you MUCH more clean volume on your speakers. For now, make sure your parametric eq is defeated and all tone controls are flat. You can play with these later to take out that peak I mentioned earlier. Don't be afraid to turn up your gain on your sub amp as far as you need too as long as the clip lights don't come on for more than a breif moment on the peaks. A slight touch of red barely noticable won't hurt anything, just stay under 33 volts. If you need too, your HU non-fader out has a level adjustment you can increase to give you a stronger signal.

I wouldn't worry too much about the speakers in the rear deck, free passive radiators What i would do however is remove the factory sound deadener between the rear seats and the trunk as this can and is designed to block low frequency pass though. The foam on your seat backs is invisible to freqencies below 80hz give or take.

Im still going to mention leaks again. Check around the driver, the entire driver chamber (no such thing as too much PL), as far as you can reach in the mouth, and ESPECIALLY the access panels!

As far as positioning your sub, make sure you have a good 6 inches clearance in front of the mouth and that the mouth is as close to a rear corner as possible. Sounds counter-intuative but having the mouth 6" away from and pointing towards the tail lights is louder than the mouth right up against the seat backs due to cancellations.

Thats all I can think of right now. Let us know your progress.

Wow, thank you VERY much for all of your suggestions! I'm a little bit familiar with how to set up car audio but not too knowledgeable. I did in fact look up how to adjust settings in the manual the other day, but I still don't understand a few things...

When I go to the X-Over FR / NF screens, all I can seem to do it set them at either PASS or ON, I'm not sure what you mean when you say to set UPPER to ON and LOWER to PASS, etc. Also, you and the manual say I can change the frequency of NF and FR, I can't find a way how

My amp is the Alpine MRP M500, btw. I forgot to mention that in the list.

I actually thought about the sound deadening between the back seat and trunk, the only thing there is a 3/16" thick piece of plastic with some cloth on the trunk side, is that the sound deadening material they installed? I wasn't sure with it being so thin that it would be much of an impact, I'll find a way to remove it in the mean time. Right now, the sub is in the back most part of the trunk with the mouth facing the driver side corner.

Now, for my biggest eye opener...

I decided to bring the AT inside and swap it with my TT in the living room so I can run a 30hz tone to check for leaks. First thing I noticed was that anything above a volt or two, the cab started to sound echoey or just plain crappy, not very clean. I found 2 tiny leaks on the panel opposite the mouth and if I stick my arm in the mouth, I think I can feel leaks, could also just be the air rushing by from the woofer, with all that PL in there it's hard to picture leaks anyway. So I decided to crank it up a few volts, I made it to about 15-16 volts and it just sounded like garbage (this is all at 30hz). I guess I could describe it as VERY distorted bass or gongy (not a real word but hopefully you'll get the idea). Not very happy, so what did I do next? I put the AT on top of the TT so I can swap back and forth and compare spl and sound quality at diff frequencies... HOLY Mother of GOD!! What a difference between them! I mean, I know there is a major size difference between the two but I had no idea that the sound difference would be so dynamic. Maybe my AT is just porly built or it's just that dramatic. The one fact I can give you is that at about 5.5 volts and 30hz, the AT hit 102 db at the mouth while the TT hit 116 db at the mouth. At 2.5 volts and 40hz, just about the same spl (103 and 117), does this data sound right? What a huge difference! And not to mention, so much cleaner coming out of the TT, almost no gongyness ( ) or distortion. What's your take on that?

Anyway, I'm done fiddling with this thing tonight, still in shock... I never realized how loud and clean my TT was until I did a side by side, lol.

Last minute note for Bill, for the TT at it's normal width, what kind of voltage can it be expected to handle? At 30hz and 10 volts it was awesome, a bit scared to turn it up more actually, haha!

I reckon there is something way wrong with you AT I'm sorry to say.

the TT goes a lot lowe. Than the AT but the general sensitivity isn't miles away. And if it actually sounds crap then there is something amiss. I've made the TAT and it was clean and smooth like the other BFM horns I've made. I think it's time to crack that baby open and check the drivers seal.

Yep, something's wrong. At the time I had the AT I had not yet built the TT but I did have my titans and t18. Although the t18 just sounded beefier most likely to the nice hump right at 50hz, the AT did go lower a tad. Volume wise, they both did ok. Actually, I made this thread that I went into panic mode and went on and on and on on how the titans sounded flabby while the AT sounded very tight. However, what happened was that I did have two leaks in the AT and the titan was completely overpowering the crucial 100-200hz range on the tops, thus making the whole thing sound slow, and just not really good. So in my experience I actually liked the sound of the AT more out of everything i've built. Once I got the leaks fixed and I eq'ed the cab, it's actually really close to the t18, and believe it or not, my t18 is pretty close to my AT but just doesn't go as low.

Oh almost forgot, after using the ply from home depot for the AT and getting leaks, I stopped using it for anything else

The TT goes lower, but the general output and response is similar above 50Hz , where most content lies. You should not be comparing the two at 30Hz, as that's below the AT passband. If there's a major difference between them at 50Hz and higher that indicates a problem with the AT.

I don't have any other tubas to compare to, but I tried out my AT today in my basement after closing it all up and was thoroughly impressed. I didn't go above 10v as I was still checking for any leaks/odd sounds but I had some jungle music playing through it, and than some reggae and I must say I almost love this more than my T39

Bass was clean, good extension and lots of output with little wattage - it lives up to its claims.

With 10v I had the microwave rattling in the kitchen above the basement. I had it firing into the corner of my basement, but all I have on the wall is studs and vapour barrier so its not a hard surface and I was still able to have great bass.

Like mentioned above sounds like something is wrong with your cab.