An LLT with two AE IB15s? - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 58 Old 04-10-07, 03:14 AM Thread Starter
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Re: An LLT with two AE IB15s?

Quote:
SteveCallas wrote: View Post
If you want to go LLT and do it right, I'd sell those drivers and get a couple higher excursion ones better suited to the task at hand. I know TC Sounds ships to your neck of the woods - one or two TC 2000 15" SVCs in a LLT would probably be all you could handle.
Okay. Thanks, Steve.

I presume the Xmax is just too small to make the exercise worthwhile? New drivers are out of the question particularly if I have to build a huge box to house them.

This means I'm really going to have to do something serious about my IB.

The BFD isn't the whole answer because I've tried hundreds of different filter combinations, both boost and cut. I need so much cut at 40Hz (-12dB) that I lose overall output.

If I went crazy with the ganged filter boosting (2 x + 10dB @ 20Hz) I could actually make the sub sound hot. Normally I can't make the sub hot which means the dialogue is too loud on films to get the same effect as the SVS.

It's as if I have a high pass fixed filter at 40Hz. Nobody else complains of lack of output low down from a 4 x 15" IB so it must be something about my particular setup.

I have a couple of new ideas to try before I start changing the array into a manifold (or splitting into two widely spaced manifolds).

I can check for a high pass filter somewhere in my system using the SVS in place of the IB array.

I can test the SVS right in front of the array to check for a null situation relative to the listening position.

Those contemplating an IB for themselves shouldn't worry. If you use long throw drivers of proven quality you should be delighted. All those happy IB owners here and in The IB Cult can't be wrong.

I still have my doubts about my AE IB15s. Getting the cones moving is still proving difficult even on sinewaves at 10Hz.

Just thinking aloud as usual...
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post #12 of 58 Old 04-10-07, 07:48 AM Thread Starter
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Re: An LLT with two AE IB15s?

Just to kill stone dead any doubts about the IB being in a null here's the straight comparison between the SVS and IB measured at the listening position.

The 16-46 was almost touching the IB drivers for this response test. Then moved back to its normal position for the IB sweep. Finally the SVS was swept in its normal position 7-8 feet from the corner.

NO EQ. Calibrated @ 75dB target level with Galaxy 140 meter untouched between sweeps. C-Slow. C-weighting unchecked in REW.

I'll leave you to guess which is which.

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post #13 of 58 Old 04-10-07, 10:28 AM
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Re: An LLT with two AE IB15s?

Well, since you've established that the location of the IB drivers isn't in a null, then I think the answer is that your infinite baffle isn't "infinite".

As long as those drivers can operate at the frequency range below 30Hz, then the problem is that you must be allowing the out of phase pressure from the rear of the drivers to cancel the pressure from the business end of the drivers. You don't have the system sealed enough such that the cancellation doesn't occur.

You would need to provide a lesser path from front to back or put a ported enclosure around them. Do you have the specs of the drivers to do a simulation?

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post #14 of 58 Old 04-10-07, 10:54 AM
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Re: An LLT with two AE IB15s?

Is enclosing the space behind the IB and porting it still out of the question? If not....and the SVS provides enough headroom and sounds fine, I'd probably use the SVS


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post #15 of 58 Old 04-10-07, 11:10 AM Thread Starter
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Re: An LLT with two AE IB15s?

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brucek wrote: View Post

As long as those drivers can operate at the frequency range below 30Hz, then the problem is that you must be allowing the out of phase pressure from the rear of the drivers to cancel the pressure from the business end of the drivers. You don't have the system sealed enough such that the cancellation doesn't occur.

You would need to provide a lesser path from front to back or put a ported enclosure around them.

Do you have the specs of the drivers to do a simulation?

brucek
ThomasW has never worried much about small leakages.

Here are the TS parameters for my drivers.

When I tried to enter them in WinISD Pro I get error notices.

AE IB15 (discontinued)

Fs________16Hz

Qms______4.9

Qes_______.48

Qts_______.44

VAS______467

Zn_________8

Re________5.6

Le________1.25

Mms._____218

Cms______.45

Bl________16

Sd_______855

SPL______89.5

Pe Cont___500

Xmax_____15.5

VC dia____54

VC l______38

Gap Ht____.385
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post #16 of 58 Old 04-10-07, 11:12 AM Thread Starter
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Re: An LLT with two AE IB15s?

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SteveCallas wrote: View Post
Is enclosing the space behind the IB and porting it still out of the question? If not....and the SVS provides enough headroom and sounds fine, I'd probably use the SVS
Despite it's shortcomings the IB can still leave the 16-46 for dead on detail and effortless power. I just need more bottom end power to match the SVS.
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post #17 of 58 Old 04-10-07, 12:03 PM
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Re: An LLT with two AE IB15s?

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ThomasW has never worried much about small leakages.
Is this ThomasW's IB or Chrisbee's IB...
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post #18 of 58 Old 04-10-07, 12:36 PM Thread Starter
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Re: An LLT with two AE IB15s?

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Sonnie wrote: View Post
Is this ThomasW's IB or Chrisbee's IB...
ThomasW is the expert in this matter.
He does not consider minor leakages a serious problem.
I tried sealing my IB enclosure doors between two REW sweeps and found no visible difference.
Having the doors open slightly (1") reduced the bottom end.
Widening the gap reduced it still further.
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post #19 of 58 Old 04-10-07, 09:30 PM
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Re: An LLT with two AE IB15s?

What is the back volume of the IB. I am modelling it in a different program. I wouldn't hit a dead dog in the *** with Win ISD. Just me. I will model it against my Cerwin Vegas.
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post #20 of 58 Old 04-10-07, 09:40 PM
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Re: An LLT with two AE IB15s?

This is for one driver as if it were mounted in my IB.

Both driven to Xmax at 20 hz. AE 110 watts, Cerwin Vega 300 watts.

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