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<blockquote data-quote="keep_hope_alive" data-source="post: 7352442" data-attributes="member: 576029">Even though they have an FS of 39Hz, and I had a 25Hz 12db/oct subsonic filter, I measured this in my cabin:<img src="http://i38.photobucket.com/albums/e128/phat_funky_beats/Sound%20Domain/12Hz_AccordTrunk.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />It was a calibrated measurement, that is actual SPL.&nbsp; Not a record or anything, but still quite loud for 12Hz on 10 year old TB subs.WHY?!?&nbsp; We were trying to test for a low frequency phase difference between two microphones using our acquisition gear - for the purpose of looking for phase of low frequency noise in an HVAC system.&nbsp; I figured my car would be able to produce adequate SPL levels at 12Hz (problem frequency for the HVAC system).&nbsp; So I put one mic in the trunk and one in the cabin and measured them at the same time.&nbsp; One downside to this test is that I could hear my vented woofers moving in response to the pressure.&nbsp; Which got me to thinking:&nbsp; does high SPL at low frequencies pressurize the speaker cones in the front of the car, causing distortion?&nbsp; me thinks so...One interesting piece of information is that the harmonics in the cabin had a much lower amplitude than they did in the trunk.&nbsp; I&#039;m not quite sure why that was and want to do further testing...With only 180W RMS per sub as a rating i dont actually get to, from a fully regulated pre-motel xant amp, the output is enough to induce pain while remaining clean and clear.&nbsp; Plenty loud enough for me.</blockquote>

[QUOTE="keep_hope_alive, post: 7352442, member: 576029"] Even though they have an FS of 39Hz, and I had a 25Hz 12db/oct subsonic filter, I measured this in my cabin: [IMG]http://i38.photobucket.com/albums/e128/phat_funky_beats/Sound%20Domain/12Hz_AccordTrunk.jpg[/IMG] It was a calibrated measurement, that is actual SPL. Not a record or anything, but still quite loud for 12Hz on 10 year old TB subs. WHY?!? We were trying to test for a low frequency phase difference between two microphones using our acquisition gear - for the purpose of looking for phase of low frequency noise in an HVAC system. I figured my car would be able to produce adequate SPL levels at 12Hz (problem frequency for the HVAC system). So I put one mic in the trunk and one in the cabin and measured them at the same time. One downside to this test is that I could hear my vented woofers moving in response to the pressure. Which got me to thinking: does high SPL at low frequencies pressurize the speaker cones in the front of the car, causing distortion? me thinks so... One interesting piece of information is that the harmonics in the cabin had a much lower amplitude than they did in the trunk. I'm not quite sure why that was and want to do further testing... With only 180W RMS per sub as a rating i dont actually get to, from a fully regulated pre-motel xant amp, the output is enough to induce pain while remaining clean and clear. Plenty loud enough for me. [/QUOTE]

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