TAT troubleshooting

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Devin Cameron
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Location: Medford, Oregon

TAT troubleshooting

#1 Post by Devin Cameron » Wed Feb 07, 2018 9:42 pm

I just finished a TAT build and it seems to have a problem. It falls on its face around 9-10 volts. It sounds very distorted like it hit max excursion. The cab is 18 in wide with an MCM 55-2421. Here's the funny part...this is the second one I've built and both have the same problem. I thought the first cab might have had an internal leak at a joint. When I built the second one and it did the same thing, I'm wondering if it's an MCM thing. If it was a typical sealed box direct radiator, I would suspect that the driver chamber was too large. I've tested it in my truck, on the workbench, in my living room in place of my THT and get the same result. Frequency doesn't seem to matter either. Feed it around 10 volts and it's done playing nice. It sounds perfect below that, maybe up to 8 volts or so. But doing the math, that's less than 25 watts before it's unusable. That's barely loud enough to overcome road noise, lol. Am I missing something here? What's the voltage limit on a TAT? I'm definitely spoiled with the THT, am I expecting too much from the TAT? I appreciate any and all help and suggestions.

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Bill Fitzmaurice
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Re: TAT troubleshooting

#2 Post by Bill Fitzmaurice » Wed Feb 07, 2018 9:56 pm

It's not the MCM. It shouldn't hit xmax at less than 20v, xlim at less than 30v unless you're feeding it with content below 25Hz. Even in a room with 10v in it should be hitting well over 100dB. I suspect the surround is hitting the baffle.

Devin Cameron
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Joined: Tue Jun 24, 2014 1:05 pm
Location: Medford, Oregon

Re: TAT troubleshooting

#3 Post by Devin Cameron » Wed Feb 07, 2018 10:17 pm

Thanks, Bill. I checked it attached to the baffle before I installed it. It seemed fine, at that point. What are the odds something changed during the build that would cause that? This is the second build to do the same thing. Kinda hard to check it when the cab is closed up. I was pretty critical after the first one had problems. This build, i went as far as to rabbet the driver side of the baffle to make sure the driver would be centered. Could that be the cause?

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Bill Fitzmaurice
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Re: TAT troubleshooting

#4 Post by Bill Fitzmaurice » Wed Feb 07, 2018 10:41 pm

All I can say for sure is that whatever the problem is you did it to both of them. If it was a design issue we'd have had reports of it fourteen years ago. I'd pull the driver, put blue carpenter's chalk on the surround, install, fire it up, then pull it looking for chalk marks on the baffle.

Devin Cameron
Posts: 5
Joined: Tue Jun 24, 2014 1:05 pm
Location: Medford, Oregon

Re: TAT troubleshooting

#5 Post by Devin Cameron » Wed Feb 07, 2018 11:00 pm

I'm sure it's not a design issue, it's a builder issue. Ok, I'll pull it and check for clearance issues. Thanks again, Bill.

Devin Cameron
Posts: 5
Joined: Tue Jun 24, 2014 1:05 pm
Location: Medford, Oregon

Re: TAT troubleshooting

#6 Post by Devin Cameron » Thu Feb 08, 2018 10:35 pm

Ok, so I checked surround to baffle clearance. No chalk on the baffle. I was honestly hoping that was the problem. So I swapped the driver with another MCM I had, just for fun. Still the same problem, something isn't playing nice together past 9-10 volts. It doesn't matter if it's music or a test tone, I used 50Hz.

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Bill Fitzmaurice
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Re: TAT troubleshooting

#7 Post by Bill Fitzmaurice » Thu Feb 08, 2018 10:53 pm

10v at 50Hz should be knocking pictures off the walls. See what happens with the driver in free air. At 50Hz with 10v excursion should be 4mm or less. I assume you're measuring volts AC.

CoronaOperator
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Location: Medicine Hat, Alberta, Canada

Re: TAT troubleshooting

#8 Post by CoronaOperator » Thu Feb 08, 2018 10:59 pm

Maybe its a signal/amp issue?
Built:
17" width 10" driver Autotuba
2 x 29" width dual Lab12 Tuba60
6 x DR250 2510/asd1001
In progress:
2 x DR250 2510/asd1001
For best results, point the loud end of the array towards the audience

Devin Cameron
Posts: 5
Joined: Tue Jun 24, 2014 1:05 pm
Location: Medford, Oregon

Re: TAT troubleshooting

#9 Post by Devin Cameron » Thu Feb 08, 2018 11:34 pm

Guess I'll check free air tomorrow. Yes, I'm measuring volts AC.

Corona Operator, I was thinking the same thing, but I've actually tested it on three different systems with the same results. I swapped the TAT for my THT and still the same. The THT tears the house down with less than 10v. The amp in my truck will output about 30v before the clipping indicators start to light. Hmmm...guess I'll test head unit and xover output voltages.

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