What do you mean by "with the fall off"? Can you explain a bit more how you plan to cross this sub at 300 Hz? I'm not following your reasoning at all.
What i noticed is that without a crossover the drive unit produces very little bass.
With a crossover the drive unit produces more bass, you will have to try this out if you do not believe me
If you have a 2-way speaker and the bass midrange unit crossovers over at 5khz, which is a typical frequency, you get more bass than if there were no crossover on the bass midrange unit.
If you were to lower the crossover frequency down to 1khz, the sensitivity goes up and you get even more bass.
So without a crossover the midrange unit i am planning to use will produce very little bass, with the open baffle arrangement i will get serious cancellation for everything under 300hz
With a crossover the drive unit produces more bass, you will have to try this out if you do not believe me
If you have a 2-way speaker and the bass midrange unit crossovers over at 5khz, which is a typical frequency, you get more bass than if there were no crossover on the bass midrange unit.
If you were to lower the crossover frequency down to 1khz, the sensitivity goes up and you get even more bass.
So without a crossover the midrange unit i am planning to use will produce very little bass, with the open baffle arrangement i will get serious cancellation for everything under 300hz
You don’t want bass going to your midrange at all. You’ll just get excursion and distortion with no benefit.
But in post #20 you said you're thinking of using the mid driver without a high-pass filter. Now you say you want a crossover to boost the low end of the mid. I'm not following your reasoning at all. (You might indeed get some peaking from a high-pass filter, but it will be a pretty small effect compared to other factors affecting the response.)
If you really want to understand what output you might get from a particular driver in a particular baffle, and also the effects of filters on the response, you should try some modelling software. @lousymusician suggested Basta! in an earlier post, and I'd second that.
If you really want to understand what output you might get from a particular driver in a particular baffle, and also the effects of filters on the response, you should try some modelling software. @lousymusician suggested Basta! in an earlier post, and I'd second that.
ianbo : Sorry I am not explaining myself very well, I am not saying that I will be using a crossover, I am only giving a hypothetical situation to answer your question
Good point, but if I use a crossover on the midrange unit, even if it is a simple single capacitor, that will cause crossover losses when compared to a no-crossover situation wherein the signals from the amplifier pass straight through to the driver unit unobstructed
What my own ears have told me is that drive units with no crossover on them produce very little bass, a 5khz crossover makes the drive unit produce more bass, lowering down even further to a 1khz crossover makes the drive unit produce even more bass, I have tried this and this is what I have heard. As the crossover frequency goes down the sensitivity goes up
Good point, but if I use a crossover on the midrange unit, even if it is a simple single capacitor, that will cause crossover losses when compared to a no-crossover situation wherein the signals from the amplifier pass straight through to the driver unit unobstructed
What my own ears have told me is that drive units with no crossover on them produce very little bass, a 5khz crossover makes the drive unit produce more bass, lowering down even further to a 1khz crossover makes the drive unit produce even more bass, I have tried this and this is what I have heard. As the crossover frequency goes down the sensitivity goes up
Incredible, but a lowpass filter introduces resistance ( because a coil is made of copper wire) that causes a sensitivity loss.
Also efficiency goes down, after filtering ( because you limit the bandwidth).
But...but...those are unimportant things as long as you possess a 5W amplifier!
You're contradicting yourself. First you said you can increase bass by inserting a low crossover. Now you're saying you don't want a crossover because you don't want bass losses. (Your second statement is correct, but your first isn't.)
I'm not trying to be difficult - I'd like to help, if I can. But you've said some pretty muddled things about speakers and crossovers. Maybe read some of the standard sources? The Loudspeaker Design Cookbook, for example. Linkwitz Lab on open baffles. Playing with a sim program like Basta! or Vituixcad is a great way of learning too.
To go right back to your original question an 8 inch mid driver used on an open baffle could definitely handle down to 300 Hz. It could probably even go down to 120 Hz. But you don't stand much chance of getting an open baffle mid to blend with a monopole sub at either frequency unless you design it properly. And for that, you'll need to get your head round matters including driver parameters, baffles, and crossovers (active or passive). Trial and error is a lottery with the odds stacked against you.