An LLT with two AE IB15s? - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #21 of 58 Old 04-11-07, 02:51 AM Thread Starter
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Re: An LLT with two AE IB15s?

Hi

I have a somewhere around 60cu ft or 17000 liters.

I make that roughly 9 x total VAS for 4 drivers.

Thanks for your efforts.
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post #22 of 58 Old 04-11-07, 06:04 AM
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Re: An LLT with two AE IB15s?

Hi Chris, l remember thomas saying the spiders were incredibly stiff on those drivers and there was doubt to the stated specs as well.........so your drivers fs might be much higher than as stated ? they might be rolling off at who knows? maybe 30hz or somthing?? just throwing some thoughts around here......is your ep2500 clipping at all at full gain?, mine will on wotw if l'm not careful and my gain settings are around 2 o'clockish ( thats with -6 master volume at the time ) .
those drivers must need a ton of power to get them really moving
lf you drivers were fully streessing out then l'd say you dont have much choice for more output other than better/bigger drivers or a ported alignment if using the same drivers..but your drivers arent at their limits yet by the sound of it so more power and maybe better isolation of the rear wave should do it

Hope you get it working to it's full output soon mate ..... cheers ken
post #23 of 58 Old 04-11-07, 06:37 AM Thread Starter
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Re: An LLT with two AE IB15s?

Hi ken

I'm awfully tempted to go out and buy 4 Cerwin Vega Xmax 15 drivers and do a straight swap with the AEs.

If they prove to be no better then I'll just have to defy my wife and build a manifold in the ceiling for the extra drivers.

Or build an eight driver opposed manifold with a much lower VAS ratio than I have now in the same place as the present array. I'd have to run each quad on a separate channel of the EP2500 to avoid driver imbalances.

I'm getting better results from the doubled identical 20Hz boost filters but it seems material sensitive. Muddy on one CD and thin on the next.

Nothing I've tried so far comes close to the brute power, clarity and detail that bypassing the BFD provides.
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post #24 of 58 Old 04-11-07, 08:48 AM
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Re: An LLT with two AE IB15s?

Chris,

60 cubic feet is more like 1700 liters

17000 liters would be 600 cubic feet.

And I don't trust the BFD. I use a Rane PE17.
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post #25 of 58 Old 04-11-07, 09:39 AM
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Re: An LLT with two AE IB15s?

Quote:
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
Yeah, I played around with that driver and came up with about the same low power of 110watts required to hit Xmax. He does have 4 drivers though and so it would be about 440watts before exceeding Xmax. Xmax is only a linearity spec. We don't know the Xmech. Most of the simulations I've seen here always exceed Xmax somewhat.

If you put those 4 drivers in a vented enclosure of 45cu.ft tuned to 11Hz with a 8"port at ~19in. and input 1000watts, the excursion compared to the same IB at 1000watts is more acceptable. Here's the comparison (with the Xmax line shown) along with the SPL comparison between IB and LLT. They both have 1st order filter at 10hz to account for electronics rolloff.

EXCURSION
An LLT with two AE IB15s?-vented-vs-ib-excursion.jpg

SPL
An LLT with two AE IB15s?-vented-vs-ib-spl.jpg

I don't know if much is gained there with the vented enclosure. I would think the gain used before with the BFD would have pulled the IB up to the Vented. The experts here would know more about this....
Either way, Chrisbees plots sure don't look like the simulations. (Certainly everything below 10Hz is just noise)

brucek
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post #26 of 58 Old 04-11-07, 12:17 PM
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Re: An LLT with two AE IB15s?

That is the same sort of thing I see when I model 4 of the new Mach 5 IXLs in an IB or in a Big Box with port. A whole lot more heat for a very small amount of acoustical energy. And when you consider the in room variables ????

Chris, I think I remember you saying you wired your drivers to present an 8 ohm load to the amp. Is that correct. You may not be getting enough power to those drivers. I am now a firm believer in wiring my drivers to present a 2 ohm load to my amp on one of the channels. That way I am sure to get some current flowing. Amp turns is what makes a driver function. And you sure cannot change the turns easily.
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post #27 of 58 Old 04-11-07, 01:54 PM Thread Starter
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Re: An LLT with two AE IB15s?

It gets more interesting with each new post.

Thanks for all the ideas.

Sorry. I confused the IB with the proposed LLT box behind the speakers when I posted earlier.

I have just remeasured my IB enclosure.

18 cu meters = 18,000 liters.

Total VAS is 469 x 4 so I have an enclosure to driver VAS ratio of roughly 9.5:1.

My EP2500 sees 8 Ohms per channel. 2 x 4 Ohm drivers in series.

450 Watts per channel = 225 Watts per driver.

Last edited by Chrisbee; 04-11-07 at 02:01 PM.
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post #28 of 58 Old 04-11-07, 02:14 PM
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Re: An LLT with two AE IB15s?

Quote:
18 cu meters = 18,000 liters
Considered infinite.

Quote:
2 x 4 Ohm drivers in series
The specs you gave on the drivers says different. It says they have an Re of 5.6 ohms. That's a Znom of 8 ohms per driver.

Quote:
450 Watts per channel
The EP2500 amp spec is 450 watts into 8 ohms.

If you have 2 drivers in series, then you are presenting a 16 ohm load to the amplifier (since they are 8 ohm loads a piece). Little wonder you can't produce any power.

brucek
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post #29 of 58 Old 04-11-07, 03:15 PM
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Re: An LLT with two AE IB15s?

Have you confirmed the phase wiring of all 4 drivers? That measured response really looks like cancellation of some sort is happening below 40hz or so. Maybe try running a measurement sweep with one driver at a time, or at least only one channel/pair.

How about showing us an REQ sweep of the IB with and without EQ as well?

-Brent
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post #30 of 58 Old 04-11-07, 06:05 PM
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Re: An LLT with two AE IB15s?

Chris,

Try getting more current flowing to those drivers. Parallel versus series wiring. And use both sides of the amp, don't bridge. You have a much better chance of driving without clipping with those pro amps if your speakers have a low impedance dip somewhere along the line. I run one of my Tapco amps with two ohms on one side only. Just leave the other side off.

If they are really 8 ohm drivers then parallel all of them and hook to one side of the Behringer and see what happens. If it opens up you know what the problem has been. You may need that big inrush of current to give you the "impact" that you are looking for. (Not to mention what your lovely wife needs to hear her ROCK music as she likes it.) I am a real fan of what I call Sh!t kicking rock and roll. ZZ top style stuff. Steppenwolf.
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