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Post by chrisbee on Nov 21, 2006 5:53:54 GMT -7
Thomas has mentioned a number of times that the AE1B15 drivers have very stiff suspension which takes months to break in. Is the deliberate use of continuous high level very low frequency sinewaves worthwhile? Even now my drivers hardly ever get moving even at thunderous levels and using a +16dB @ 20Hz filter on the BFD! Which suggests they may never break in!  Obviously one wouldn't want to do any damage like overheating the voicecoil. Any thoughts on the subject? |
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Post by Darren on Nov 21, 2006 7:24:31 GMT -7
I was kinda wondering how long until my RL-P 15's were broken in as well as they are stiff also.
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Post by ThomasW on Nov 21, 2006 9:55:52 GMT -7
AFAIK no other drivers are built like the AE-IB15"s. And I didn't know this until the exchange that took place when the published accuracy of the AE-IB15 T/S parameters were challanged by someone making their own measurements.
Without rehashing that entire unpleasant incident, suffice to say the AE spiders are coated in a particular manner as to make them exceedingly stiff.
IMO it's folly to 'break in/burn-in' any driver. That occurs within a week of so of normal operation. The AE15 being the exception to this one week rule. Double spider drivers like the RL-p15" take slightly longer to 'relax' as well.
If one is attentive to the performance of their drivers they will notice a slight increase in output and them playing a bit lower as compared to the out of box performance. This is the indication that the suspension and the adhesives used to assemble the driver have relaxed from their 'new' condition.
If one is concerned as to the potential overheating of the drivers, all one needs to do is place their hand on a motor after a period of use. If it's hot then the driver is being overworked. This is a highly unlikely in any IB where people have followed the recommendations, and have the workload shared by multiple drive units.
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Post by chrisbee on Nov 22, 2006 9:14:59 GMT -7
Thankyou, Thomas. I am still trying to equate the claimed 16Hz Fs with my IB's response curve. Since I am at home with a cold I have some more response curves this time from my new soft-look RS SPL meter. I suppose I should post these in my project thread but they may also have some general interest which you may wish to comment on. All are with speakers muted & the IB calibrated for a target level of 80Hz in REW. Active 24dB/octave crossover at 60Hz. Ist: Nearfield @ 2" NO BFD.  2nd: Nearfield @ 2" + BFD +16dB @20! 3rd: Listening position NO BFD. 4th:Listening position + BFD 5th: Listening position + 1 foot forward + BFD.  6th: Listening position + 2 ft forward + BFD. Once I had finished playing with response curves I delved into the depths with REW's "frequency follows cursor". I wanted to see how much effort was required to "exercise my drivers". ;D A silent 90dB at the listening position 9 feet from the IB @ 10Hz is easily achievable with less than 1/4 inch (6mm) cone movement. Only doors and walls rattling and thickening of the air suggested anything was happening. I didn't dare go any louder in case of damage to the house or its contents. 15Hz and the air thickened even more and I had found the resonance of my french windows. (glazed double doors closing off the IB enclosure). Cone movement now very small. The doors refused to remain still despite leaning all my weight on them. I tried opening one of the doors and the other continued to shake. The enclosure felt pressurised when I stuck my head in. This is supposed to be the "Irene" frequency in Blackhawk Down. Certainly nothing @ 15Hz in the LFE of my own copy or I would know about it. 20Hz and the pressure was gone but things went quiet except for surfaces vibrating madly. 25Hz found my glass & steel computer desk vibrating heavily and the sound was now clearly audible. I may try raising the overall level via the IB's amp and then reduce the upper frequencies instead of boosting so much at 20Hz. Or perhaps a combination of both methods. |
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Post by ThomasW on Nov 22, 2006 10:05:34 GMT -7
Thankyou, Thomas. I am still trying to equate the claimed 16Hz Fs with my IB's response curve. Trying to do that is a zero sum game due to the design of the AE spider, and it appears some of the drivers were out of spec.. There was a thread here I locked, with a parallel thread on the AE forum where the T/S parameters of the AE15 were challanged. I'm not going to rehash that topic since these driver are no longer sold. People have what they have, and there's no recourse as far as I can tell, since John and AE seems to have fallen of the face of the planet. Also it's erronous to think one will see a big difference of the in-room plots of a driver with Fs of 16Hz vs one with an Fs of 26Hz. That's not the way these things work. This is the reason I tell people not to fixate on the Fs, if it's within reason for a sub. However..... Specific to your installation. Read the last paragraph in the post in the link below, then look at the attachment in that post www.avsforum.com/avs-vb/showthread.php?p=8909964&&#post8909964Now understand what they're talking about with regard to small box loss, is exactly what's happening with your IB in your room. Regarding the 'Irene' scene's subsonic content, that has been documented multiple times by different people.   People need to understand that despite correction curves and claims to the contrary, RS meters aren't accurate in the subsonic range. The only in-room measurement tools accurate in the subsonic range are $5000 a pop. |
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Post by cameron on Nov 22, 2006 10:54:46 GMT -7
Thomas,
Wow! Just so I make sure I am reading this correctly, does that spectral display show that the Irene scene has an ~8Hz fundamental at ~ -10dbFS at 23:21.200?
-- Cameron
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Post by ThomasW on Nov 22, 2006 11:12:19 GMT -7
Thomas, Wow! Just so I make sure I am reading this correctly, does that spectral display show that the Irene scene has an ~8Hz fundamental at ~ -10dbFS at 23:21.200? -- Cameron Yes!..... |
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Post by chrisbee on Nov 22, 2006 12:21:53 GMT -7
Are you suggesting that my double doors are acting as a huge ABR? ;D
This had occured to me but I was uncertain if it would be in phase or out and at which frequency it mattered.
I may have to put my copy of Blackhawk Down through Spectrum Lab. It may be a region problem. I've played "Irene" lots of times. Even with my fingertips on the drivers at very high levels there's nothing particularly low that I can detect. My drivers are hardly moving during this scene. Judging from my experiments today the cones should move noticeably to 15Hz signals.
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Post by ThomasW on Nov 22, 2006 13:13:23 GMT -7
Are you suggesting that my double doors are acting as a huge ABR? ;D Yep and the flex in the entire wall section the IB is mounted on. Yes I know the wife won't allow an I-beam running to the middle of the room to stiffen everything up. Although a creative person could add paint and other decorative elements to effectively integrate it into a post-modern decor theme ....  I'm sure with enough power and a really expensive EQ you could force the drivers to play much lower. But the room itself is so inherently 'lossy' you're fighting an uphill battle. There maybe different region editions of BH Down, but seems odd if that's the case. I don't own a copy so it not something I can test. |
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Post by chrisbee on Nov 22, 2006 13:52:09 GMT -7
And what's the bad news? ;D
Post modernism? In a timber-framed, agricultural cottage? There's no solid structure within reach which I could tie into.
I've just run BHD "Irene" through Spectrum Lab and there's nothing much below 20Hz.
Then I remembered something about Spectrum Lab not reading the LFE channel from the DVD drive.
Back to the drawing board.
I could feed the LFE track into my external soundcard from the DVDP or surround processor and monitor that.
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Post by ThomasW on Nov 22, 2006 15:22:32 GMT -7
And what's the bad news? ;D Post modernism? In a timber-framed, agricultural cottage? There's no solid structure within reach which I could tie into. Well I guess there's a big drilling rig and MASSIVE concrete caissons in your future..  Don't know, the other DVD's I've measured show subsonics and that was just the internal signals of the soundcard. |
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Post by rodny on Nov 22, 2006 17:04:40 GMT -7
Hey guys, I played the Irene scene and my subs move like crazy , the wall doesn't move!!, it feels weird when that's going on  , maybe you're wall flexes so much the you are actually losing the bass at the low frequencies, you said the you're wall moves at low frequencies so instead of the subs moving the wall is the one moving, taking away from the subs.  Its like having a sub box the flexes, you loose bass. Chrisbee is your wall moves when you played the 10Hz or 15Hz @ 90db? |
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Post by titch on Nov 22, 2006 19:47:24 GMT -7
Thats kind of funny that you guys are talking about Irene. I just played abunch of movie clips for a friend this last weekend and you could really tell the difference when Irene cut into the scene. We even went around to the back of the subs and played the scene again and you could just see the subs as they changed hz.
Good stuff I tell yeah.
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Post by chrisbee on Nov 23, 2006 2:18:18 GMT -7
;D
My copy of BHD is region 2. (Scandinavian subtitles)
I'll have to ask on the European forums if they have the same VLF LFE content that you guys are getting.
As to wall flexing I don't disagree that the baffle wall vibrates. As do the double doors.
My exercises at 10-20Hz yesterday were to prove that my IB can produce high levels of VLF without problems. I think I proved that, at least to my own satisfaction. I didn't push the 10Hz above an indicated 90dB (uncorrected) but there is obviously far more in reserve with only a 1/4" of total cone movement.
If "my" Irene had serious VLF content then my IB would certainly reproduce it at levels that were detectable.
I'm still wondering if there would be any point in building a manifold to replace the array. The vibrations may be acoustically excited rather than physical reaction to the movement of the cones. The only way top find out is to build an opposed driver manifold and see if it helps.
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Post by ThomasW on Nov 23, 2006 8:33:41 GMT -7
My exercises at 10-20Hz yesterday were to prove that my IB can produce high levels of VLF without problems. I think I proved that, at least to my own satisfaction. I didn't push the 10Hz above an indicated 90dB (uncorrected) but there is obviously far more in reserve with only a 1/4" of total cone movement. The lower excursion is a function of the design of the spider. The AE15"s are from the inventory purchased when Nick of Lambda left the speaker business. John took the drivers Nick designed for open baffle operation and sold them for IB use (a good thing IMO) Interesting question. It would lower the wall shake, but wouldn't impact the inherently lossy characteristics of the room Yep |
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Post by chrisbee on Nov 23, 2006 16:25:51 GMT -7
Hmm. Now I'm struggling to come to terms with the extension and output of my humble 12" 16-46PCI in this same "lossy" room. That was running on high level connections from a downmixed stereo signal straight off the DVDP without any bass redirection and miles from the nearest corner. ;D I'll have to run some curves on the SVS placed right in front of the IB. If that proves to be even better than its previous position in the middle of the room I'll just have to accept defeat gracefully and build a manifold! |
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