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Discussion Starter #1
Steve et al

I need more bass down low and can't squeeze any more out of my 4 x 15" IB without playing it loud or boosting to silly levels at 20Hz with the BFD.

Bypassing the BFD gives me back my bass but it's humped high at 40Hz and I lose most of the bottom end.

My classical organ music is stretching my wife's tolerance levels. She hates it when I crank it just to get more bass.

When she wants to play her rock music she sneers at the IB as completely gutless compared with "her" 16-46PCI! :crying:

Would you like to run some numbers past me please?

No promises it will get built but there's a 9' feet long x 4' high triangular space under the sloping ceiling behind my TV and speakers.

This space is just used for bookshelves and boxed storage at the moment.

8' x 4' is a whole sheet of 3/4" plywood or MDF!

We might be looking at ~60 cu.ft or ~1700 liters! :T

It's probably much too small for 4 x 15" drivers but is it big enough for 2? :dumbcrazy:

Thanks

Chrisbee
 

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Discussion Starter #3
Rodny

A 10" PVC pipe is so NOT 21st century! :devil:

How many cu feet did you need in each of your dog kennels? :)
 

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Discussion Starter #5
Rodny

I've just been re-reading your "makeover" thread.

But it was mostly about some supermodel guy posing in a kennel! :eek:

Steve wanted me to build a 150 cu.ft. box for my 4 x 15" drivers. :dumbcrazy:

No way! It would become the tallest structure in Denmark! :dizzy:

I might just squeeze in two drivers in the space I have available. :coocoo:

I could have a hybrid of 2 x 15" IB and a 2 x 15" LLT in the same room.:devil:

That way I could still belong to The Cult and The Shack. :cunning:
 

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Something is definitely wrong with your IB. Mine will chase you out of the house playing Metallica, Judas Priest etc... I assume you must have a huge null. Are you sure she isn't just used to bloated bass? I'm ubmmed that you can't get the IB to behave to her liking. :(
 

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Discussion Starter #7
Something is definitely wrong with your IB. Mine will chase you out of the house playing Metallica, Judas Priest etc... I assume you must have a huge null. Are you sure she isn't just used to bloated bass? I'm ubmmed that you can't get the IB to behave to her liking. :(
Hi Darren

When I put the 16-46 in the same place as the IB the bass was totally overkill with almost zero gain on the Bash. So I have always had the SVS about 7 or 8 feet from that corner. Where it is still very powerful (~108dB RS uncorrected) on the deep stuff and climbs naturally all the way to 15hz without any eq before falling away rapidly.

I can get loud bass from the IB without the BFD but when I add any boost @ 20 Hz to try and drag the sub 30Hz response up I lose lots of bass output on programme material. The bass detail is tremendous but I just can't shake the floor like the SVS does so easily on films.

The IB will go very loud indeed using REW with "frequency follows cursor" but not on films unless I turn the master volume well up. I can't run the IB hot because it is already at max on the EP2500 and +6dB on the CX2310.

I ought to do a sweep with the SVS right in front of the IB using the Galaxy SPL meter to check the response.

Then do a sweep of the IB with the BFD bypassed for comparison.
 

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That just doesn't seem like it is working well Chris. My measly 2 15 inch drivers in the IB will shake the house so hard that I truly am afraid of structural damage.
 

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Discussion Starter #11
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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Discussion Starter #12
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. :crying:

 

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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?

brucek
 

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Discussion Starter #15
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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Discussion Starter #16
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 :nerd:
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. :dumbcrazy:
 

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Discussion Starter #18
Is this ThomasW's IB or Chrisbee's IB... :scratch:
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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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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