BillFitzmaurice.info

Is your system truly crossing over at 90 Hz, or is that where the filter is set at the moment.

AT typically requires a lower filter set point ...typically between 50-70 Hz indicated.

As far as the mirrors rattling, throw a meter on the subs and see what they're actually doing voltage-wise. Sounds like they're not getting enough signal.

A fair of tweaking is required as horns aren't plug-and-play....but your rig should have no problem clearing 125 dB SPL (ie. stupid loud) across the board. If you've got RTA, now's the time to use it.

Radian wrote:Is your system truly crossing over at 90 Hz, or is that where the filter is set at the moment.

AT typically requires a lower filter set point ...typically between 50-70 Hz indicated.

As far as the mirrors rattling, throw a meter on the subs and see what they're actually doing voltage-wise. Sounds like they're not getting enough signal.

A fair of tweaking is required as horns aren't plug-and-play....but your rig should have no problem clearing 125 dB SPL (ie. stupid loud) across the board. If you've got RTA, now's the time to use it.

Yes, it should be 90 Hz, the amp manual has a frequency table the panel markings vs actual freq.
Voltage is another matter, the amp sub channel is rated at 240Wrms @ 3 ohms, which is the load two parallel wired AT's should be when loaded with 4 ohm drivers. That means 26.8 Vrms. Which is 37.9 Vpeak. The question is does my cheap digital multimeter measure Vrms or Vpeak ? I don't know, it doesn't say anywhere.

I put a minimum-width, dual-8" TAT (Tall AutoTuba) in my wife's Dodge Nitro, and it gets LOUD.
Every mirror shaking, seat providing a massage, loud.
You must be underpowering them.
Also, flip them over, so the mouth is pointing up. That might get you a little more output as well.

Treo wrote:Yes, it should be 90 Hz, the amp manual has a frequency table the panel markings vs actual freq.

Then try lower. As far as the meter, using sine wave test tones will be OK.

Treo wrote: The question is does my cheap digital multimeter measure Vrms or Vpeak ? I don't know, it doesn't say anywhere.

For a sinewave it will display a calculated RMS voltage based off a peak reading. FWIW If there are weird waveforms and harmonics present then you would need a true RMS voltmeter (fluke) as the cheap meters will display a weird reading but for sinewaves you can read the display as Vrms.

You definitely got something wrong going on. My 13" panel AT with the cheapo MCM driver rattled everything and was painfully loud. And it was in my trunk! I'd check the wiring then work your way to the amp and headunit.

Ok, so i tried a true RMS multimeter, and got the same readings at the cheapo one. Used sine waves from the Bink audio test cd. Voltage to the cabinets is correct. Double checked wiring for same polarity. Ended up lowering the gain on the mains a bit, and set the sub crossover a bit lower, and now I got the balance I was looking for. And don't get me wrong, it is a very loud and clear audio system. Sounds a lot better than many I've heard. Definetly enough to be painful to the ears. It's just not "vibrating eye-sight and hard to breathe" loud. It may be a case of managing expectations as well, the AutoTuba is a very good design, but we're still only talking about two cheap 8" woofers here. It's very impressive for what it is.

Treo wrote: It's just not "vibrating eye-sight and hard to breathe" loud.

IME with car audio, vibrating eyesight doesn't happen until about 134-138 dB's.

CoronaOperator wrote:
IME with car audio, vibrating eyesight doesn't happen until about 134-138 dB's.

That's probably true, and I wouldn't listen to music that loud anyway, it's really just a question of wow-factor. But this little system impresses in many other ways, by being very musical and responsive. Far from that typical "struggling woofer" sound. I might still experiment with placing the subs differently in the back, maybe sideways or forward firing, just to see what happens with the response dip around 75Hz. When I tried them in the garage they were very strong throughout their frequency range. Maybe should have put a bit longer cables in the car though.

Treo wrote: That's probably true, and I wouldn't listen to music that loud anyway, it's really just a question of wow-factor. But this little system impresses in many other ways, by being very musical and responsive. Far from that typical "struggling woofer" sound. I might still experiment with placing the subs differently in the back, maybe sideways or forward firing, just to see what happens with the response dip around 75Hz. When I tried them in the garage they were very strong throughout their frequency range. Maybe should have put a bit longer cables in the car though.

I love my autotuba, very musical with lots of definition. That response dip ~75 hz is most likely a reflection off of the front firewall/windscreen. I usually try to get down to 80hz from the door speakers to eliminate that but you need some really capable 6.5's, lots of power and you have to really beef up the doors for that. Also, try a sweep without the door speakers hooked up to make sure there are no phase issues between them and the sub.

Here is a link to an album of my original build to give you an idea of what I did to the doors:
http://s769.photobucket.com/user/corona ... ibrary/Car

Treo wrote: That's probably true, and I wouldn't listen to music that loud anyway, it's really just a question of wow-factor. But this little system impresses in many other ways, by being very musical and responsive. Far from that typical "struggling woofer" sound. I might still experiment with placing the subs differently in the back, maybe sideways or forward firing, just to see what happens with the response dip around 75Hz. When I tried them in the garage they were very strong throughout their frequency range. Maybe should have put a bit longer cables in the car though.

Try my suggestion first.
When the hatch is open, looking into the cargo area, flip both cabs clockwise 180 degrees. Keep them facing the hatch.

That will allow the airflow from the horn mouth to make a smooth curve along the hatch and into the cabin.

It doesn't seem like it should make that much of a difference, but it does. Around a 2dB difference, in my experience.

Ryan Sober wrote:
It doesn't seem like it should make that much of a difference, but it does. Around a 2dB difference, in my experience.

No you're right, it doesn't. But ok, I'll see if it can be done, however there might be some problems with the speakon connectors i used and the rear backrest. Will report back once i tried it.