The pictured sim above is of an Offset TL mode, I wonder why I can't recreate this response in the Bass Reflex mode of HornResp, maybe I should ask @David McBean in his thread.
Oh, i see…. Yeah, definitely wanna pay attention to that ~48 cm (170 hz) 1/4 wave resonance if looking at the bandwidth up there
hover on LRc and adjust it to match the 4000 cm2 . it still puts the driver at the ‘closed’ end of the box/port though ..
sure would be intersting to know how horn response knows where all those 1/3,1/5,1/7…. Harmonics are and how to show us that placing the driver on one of them doesn’t allow it to get excited. i wonder if there’s software to design musical instruments in this way? Or antenas?
hover on LRc and adjust it to match the 4000 cm2 . it still puts the driver at the ‘closed’ end of the box/port though ..
sure would be intersting to know how horn response knows where all those 1/3,1/5,1/7…. Harmonics are and how to show us that placing the driver on one of them doesn’t allow it to get excited. i wonder if there’s software to design musical instruments in this way? Or antenas?
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The topologies are quite different -
YOUR OFFSET TL DESIGN:
NORMAL BASS REFLEX:
OFFSET BASS REFLEX:
Which topology should I follow? Looks like the closed mouth horn has all the components...
This is a representative rough of what I would be building if I did build a BR. I would stack the 18"s vertically. If you wanted to cross at 200hz you live with Ctc flaw that lives briefly towards the top of the register, maybe above 178hz or so... or you could use a passive XO on the lower woofer. Both scenarios allow you cover sub bass to a 200hz xo, while using one Amp and one DSP channel accept there would be some type of flaw from 178hz-300hz regarding time alignment and directivity, though it may not be a large or noticeable one. I am considering the latter using a passive XO but I have no idea how realistic a high power passive low pass is. This enclosure would be about 37.5 inches tall and I'd have to find a way to place the BR ports out of the way. Tuning to ~22hz It keeps group delay down to 10ms at 30hz. The alternative would be to tune to 25hz for cinema or 30hz for music. Theres no damping in this sim, I feel that getting the best response without damping is important. Adding damping in the actual build will only add to SQ of your already acceptable FR. My take on this build is a box thats 37.5 inches tall, with barely enough room to fit the stacked 18's and 31.5 inches long, 32.5 inches wide.
I look at it as an acoustical center, I would use a slot, not a round port, acoustically centered to mimic the sim. The port seems to not make much of a difference anyway. I am interested to figure out what @b_force was talking about, dealing with cab internal dimensions? Maybe he was suggesting to break up the internal volume to avoid resonance?
It depends on what you are trying to achieve, as the results will be different for each.
As shown in simulations, adding absorbent filling material will dampen any internal standing wave resonances (which, depending upon the dimensions of the enclosure, will typically only occur with low energy at the higher frequencies anyway).
I might as well talk about this idea here, too. My last idea to fulfill the thread title. Bipole... Not new I know, but still worth discussing. With a Bipole configuration one woofer on the front and one on the back, there are some worthy traits to investigate. In particular, my system is destined to go into a corner. A rear woofer of a cab in the corner would have a nice FR to add to the whole.
The questions;
How high would I want to run the rear woofer before I didn't like it. I would think that since the front woofer is crossing to a higher driver at 200hz, just below that point, would make sense.
Can I run a passive crossover to the rear woofer to eliminate the need to use 4 amps to run it. I don't know a lot about passive filters, but 24db slope, could work. I wouldn't know where to get them either, or which ones are desirable.
Depending on the separating distance, front vs rear, limits the bandwidth the 2 drivers work as one. Above 1/4wl you get cancellations on the sides, but I forget what the lobes look like. Either way, the low pass can used to address any issues there, but, what is an easy way to sim this or is vituixcad about it?
The questions;
How high would I want to run the rear woofer before I didn't like it. I would think that since the front woofer is crossing to a higher driver at 200hz, just below that point, would make sense.
Can I run a passive crossover to the rear woofer to eliminate the need to use 4 amps to run it. I don't know a lot about passive filters, but 24db slope, could work. I wouldn't know where to get them either, or which ones are desirable.
Depending on the separating distance, front vs rear, limits the bandwidth the 2 drivers work as one. Above 1/4wl you get cancellations on the sides, but I forget what the lobes look like. Either way, the low pass can used to address any issues there, but, what is an easy way to sim this or is vituixcad about it?