Issue with parallel resistors in LTSpice

I'm trying to build a reactive load box, so I can run a guitar amplifier without a speaker. It's basically a device that simulates the impedance/frequency curve of a relatively high power speaker.

I need 4Ω nominal impedance, but my local electronics store does not sell 4Ω 100W resistors, so I though of getting four 16Ω resistors and put them in parallel. On the right it's the correct impedance curve using a single 4Ω resistor, and on the left, the same circuit but using four parallel 16Ω resistors.

Why are the simulation results different? I thought these circuits were supposed to be equivalent.

Edit by Steve G.: The following circuit gives the same results as the 4 x 16Ω resistor circuit (note the floating wire): • what are the parameters for the resistors you use ? Ideal resistors ? – Marla Jan 18 '17 at 14:39
• @Marla, I'm sorry but I'm not sure I can understand your question. I just grabbed resistors from LTSpice menu and set the resistance values. I'm guessing that since this is a this simulation they are "ideal"? – Telmo Marques Jan 18 '17 at 14:43
• Likely the resistors you chose are ideal (standard resistor). But the question had to be asked (never know what others do in spice). . Also, don't assume that spice models are ideal models. – Marla Jan 18 '17 at 14:54
• Not believing it, I tried to replicate, and I have the same behavior. Strange. I wonder what the explanation is. Have an upvote, at least you'll have that going for you. – dim Jan 18 '17 at 14:57
• There is clearly something going wrong with Ltspice here. Using the single 4 Ohm circuit, if I add a connection to the left of R1, going upwards and to the right (as if you were about to place another resistor) but leaving the connection floating then Ltspice gives the single peak at 70Hz without the upward sweep at 1kHz. – Steve G Jan 18 '17 at 15:23