I built a small(ish) MTM with 2x 4 inch drivers, and want to add a bass bin using 2X RS180 woofers in a TL. I'm getting a lot (too much) variation at Fb using Unibox, HornResp vented sim, and HornResp OD TL response.
I've used Unibox a lot, and it shows 2X RS180 in 46 liters with a 3" ID port that is 6.75 inch long (Fb/F3 35 HZ) with a flat response. Modeling the same (or very similar) in HornResp using a Vented wizard shows a very similar response, but modeling the same in a classic OD TL design with a port shows a large droop prior to Fb.
Obviously, I'm stumped. The sims use the same drivers, in similar boxes, with similar tuning, but a large difference in bass output.
I've used Unibox a lot, and it shows 2X RS180 in 46 liters with a 3" ID port that is 6.75 inch long (Fb/F3 35 HZ) with a flat response. Modeling the same (or very similar) in HornResp using a Vented wizard shows a very similar response, but modeling the same in a classic OD TL design with a port shows a large droop prior to Fb.
Obviously, I'm stumped. The sims use the same drivers, in similar boxes, with similar tuning, but a large difference in bass output.
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A quick look at WinISD and I come up with a question.... RS180-4 or RS180-8?
They sim as very different beasts. The -4 seems more capable as a sub.
They sim as very different beasts. The -4 seems more capable as a sub.
Unibox or similar can't sim a TL or vented variant [MLTL], so ignore it. End loaded Vs offset driver has different 1/4 WL vent damping maximum capabilty with end loading being the most, so normally would be used for a woofer and ideally folded to put both driver and vent at floor level for max boundary loading.
GM
GM
Thanks guys!
In order these are the (older) RS180S-8 shielded.
I understand what Unibox can and can't do. I used it to find the overall tuning for a vented box with a port, then simmed a MLTL with that volume and tuning. If anything, the TL should provide a bit better bass (30-80HZ) performance. I'm not looking for a sub, I'm looking to build the bottom end for a small MTM, and provide support from 30-100. The problem was (is) the droop in power output in the HornResp MLTL sim versus the HornResp vented sim.
The HornResp vented sim agrees with the Unibox sim.
The offset driver will affect TL harmonics (100-400Hz) , not so much 30-60Hz range.
In order these are the (older) RS180S-8 shielded.
I understand what Unibox can and can't do. I used it to find the overall tuning for a vented box with a port, then simmed a MLTL with that volume and tuning. If anything, the TL should provide a bit better bass (30-80HZ) performance. I'm not looking for a sub, I'm looking to build the bottom end for a small MTM, and provide support from 30-100. The problem was (is) the droop in power output in the HornResp MLTL sim versus the HornResp vented sim.
The HornResp vented sim agrees with the Unibox sim.
The offset driver will affect TL harmonics (100-400Hz) , not so much 30-60Hz range.
You're welcome!
Comparing a BR to a MLTL is an apples 'n oranges comparison and due to this if a BR is converted into a MLTL without allowing for the fundamental differences it will be misaligned. Also, if going from an end loaded to OD and it doesn't impact the lows [tuning] the most, then something's wrong, i.e. not acoustically a [ML]TL.
Regardless, just responded to what you wrote and now looking at the sims, the MLTL is inputted incorrectly and why it looks radically different from the others, so use the Input Wizard in HELP to try again.
GM
Comparing a BR to a MLTL is an apples 'n oranges comparison and due to this if a BR is converted into a MLTL without allowing for the fundamental differences it will be misaligned. Also, if going from an end loaded to OD and it doesn't impact the lows [tuning] the most, then something's wrong, i.e. not acoustically a [ML]TL.
Regardless, just responded to what you wrote and now looking at the sims, the MLTL is inputted incorrectly and why it looks radically different from the others, so use the Input Wizard in HELP to try again.
GM
You're welcome!
Indeed, though after creating the sim realized that while you inputted it incorrectly and didn't show the vent inputs, the only difference it made to the sim was some minor changes in the HF 'hash' due to it not including the vent's internal pipe end correction.
In short need to completely rethink the MLTL design from scratch.
Note that to see it's high power capability one needs to input the voltage [Eg] and a minimum series resistance [Rg] correctly for the speaker, then use the max power feature, which will factor in its Xmax limitations.
Eg = dual 8 ohm in parallel = 4 ohms = 2 V
Rg minimum is normally 0.5 ohms
Note your driver power rating = 60 W, Vs 100 W and Xmax = 6 mm Vs 5 mm: https://www.parts-express.com/pedoc...s-8-reference-woofer-8-ohm-specifications.pdf
GM
Indeed, though after creating the sim realized that while you inputted it incorrectly and didn't show the vent inputs, the only difference it made to the sim was some minor changes in the HF 'hash' due to it not including the vent's internal pipe end correction.
In short need to completely rethink the MLTL design from scratch.
Note that to see it's high power capability one needs to input the voltage [Eg] and a minimum series resistance [Rg] correctly for the speaker, then use the max power feature, which will factor in its Xmax limitations.
Eg = dual 8 ohm in parallel = 4 ohms = 2 V
Rg minimum is normally 0.5 ohms
Note your driver power rating = 60 W, Vs 100 W and Xmax = 6 mm Vs 5 mm: https://www.parts-express.com/pedoc...s-8-reference-woofer-8-ohm-specifications.pdf
GM
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