OB doesn't sound like that. Even with very high Qts drivers (bit below 1) that simply doesn't sound like that.
Then your earlier post doesn't make sense.
BECAUSE THE QUESTION WAS WHICH OF 2 INDUCTORS!!!!
NOT "do you approve of my project?" !!!
That is actually helpful! Finally!
I have no idea what this means.
Then what is the point of the ~1.5m if the room has no effect?!?!
Floor reinforcement DEFINITELY works with OB!
No idea what you're talking about but I don't think you understood me..It will only do that if you cross it over at 18dB, which will result in an acoustical slope of ~9-10dB. The serial resistance of the coils will push the Qt additionally. No, it doesn't become a 'high Q' driver because of that.
In an an echoic chamber.
Besides... acording to YOU... a Qts of .42 will increase to .47 (almost .5)
Again.. see the link I provided above.
If you had read the OP carefully, you'd see that its running via an active crossover RIGHT NOW!
Besides... the question had ONLY to do with inductor types (core materials), which would cause a greater Q increase, and whether a 5 hz change would make a difference!!!!!!!!!!!!!!!
Many many posts on many different boards and elsewhere say otherwise!
Maybe it just doesn't sound like that to YOU?!
Ever hear of the Carver (so called) Amazing Loudspeakers????
BONK BONK BONK
No, then it does make sense.
You don't need anyone's approval. But if your neighbour would tell you he'd buy glass wheels for his BMW, wouldn't you tell him it's a bad idea?
If you'd read carefully, there were a lot of other useful things some ppl wrote. You don't seem to be any thankful, rather the opposite. If you don't like my help or me posting here, I'll stop. Do you?
Well, you do understand that you'll get a hump in the response?
You don't want to understand?! On an open baffle the bass becomes stronger with some distance to the back wall. 1,5m is the minimum distance.
Back walls and corners don't. Side walls work, but different, they are part of the room reproduction.
No idea what you're talking about but I don't think you understood me..
*takes deep breath*
6 dB is not nearly steep enough!
*exhales*
Was that clear and simple enough?
It behaves the same on an OB in some regards or pretty close.
You mean this link? Yes, I've read it but you misunderstood or misinterpreted his approach of the bass speaker. He started with a 20cm fullrange and suggested a xo point of 400Hz to start with. And at that frequency the response of the 15" does not rise there much anymore. AND HE USED A 12dB LP! I already told you that you'd be acoustically close to that slope with 18dB because of the rise in the response of the bass! So if you'd honour his concept, my suggestion would be the closest you could get to that. And don't forget, 15" is double the diameter. If you follow his concept you'd xo it at 200Hz. And not with 6dB.
I said you should experiment with it and these active PA crossovers allow to dial in the order of it. If you had already done it, you'd surely had already realized 6dB is completely out of the question because of the big rise of the response. You haven't said anything about your crossover except it being 18dB and 70Hz. If you had tried it out, you'd know already what difference it makes and would not have asked about 70 and 75Hz. These 5 Hz aren't the problem, the 1st order xo is. DON'T YOU UNDERSTAND THAT?!
But I already told you what it doe.. Oh. OH! Oh, I'm sorry I wanted to prevent you from wasting money. I'm really sorry, I won't do that again.
Many different boards say so and measurements do too. Like I said, I doubt you've heard it yourself. I did not suggest a Qts of 1 but the essence of it is, the Qts is a tool on OB. You need to know how to use it. You don't like it and that's fine by me. What's not fine is you claiming things as fact you haven't heard yourself.
Ever hear of the Carver (so called) Amazing Loudspeakers????
BONK BONK BONK
No. And I'm not convinced they are good speakers. And he saved too much at the wrong end.
I too think that a piece of coil could cannot compensate for the low-frequency fall of a low Qts speaker in an open baffle.
Troels G uses first order low pass in his DTQWT, but it's a horn woofer and that doesn't have much to do with open baffle.
In response to the original question, I think it is almost irrelevant which inductor you would choose. Both are of very good quality, but for me the C-Coil is more sympathetic, i think this is the ultimate bass coil.
Troels G uses first order low pass in his DTQWT, but it's a horn woofer and that doesn't have much to do with open baffle.
In response to the original question, I think it is almost irrelevant which inductor you would choose. Both are of very good quality, but for me the C-Coil is more sympathetic, i think this is the ultimate bass coil.
Low Qts or high Qts
Hi
I do not understand the issue that some people have with Low Qts or high Qts.
In the end what counts for a OB woofer is the amount of air it can move.
As far as I remember a Eminence Alpha 15(Sd 800 cm2) has an Xmax of +/- 4 mm. That is very little compared to +/- 11,5 mm for my 12" Wavecor (Sd 520 cm2) woofers.
The bas from a low Qts woofer should be more controlled/tight, or am I wrong?
And remember the bas output also depends on fs of the woofer.
best regards
uwe
Hi
I do not understand the issue that some people have with Low Qts or high Qts.
In the end what counts for a OB woofer is the amount of air it can move.
As far as I remember a Eminence Alpha 15(Sd 800 cm2) has an Xmax of +/- 4 mm. That is very little compared to +/- 11,5 mm for my 12" Wavecor (Sd 520 cm2) woofers.
The bas from a low Qts woofer should be more controlled/tight, or am I wrong?
And remember the bas output also depends on fs of the woofer.
best regards
uwe
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Yes, more controlled and tight, but sometimes it's too much from the good and the bass simply not have enough SPL compared to other frequency ranges, this can be a problem especially with passive crossovers. IMHO. But i would glad to see some measurements from the OP, this would clarify more things.
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See, The Qts says essentially how high the response of the driver is at the fs compared to the midrange, a Qt of 1 means it's equally loud. You can check that at any simple model simulation program, create a sealed enclosure with any kind of driver, adjust the enclosure volume so it's Qt 1 and you'll see, the level of the response of the driver at the fb (the resonance will rise with lower enclosure volume) will be exactly the same as in the midrange.
You'll also see, it got a bump above the fb, that's not desired usually and a high Qt got an overswing and takes also longer to get back to stop moving and stop at the resting position. A Qt of 1 means, it's underdamped. A Qt of 0,5 is the best impulse response and decay (and the enclosure will be big) but starts early (relatively high frequency) to drop in level, making it a lot quieter in the bass. A Qt of 0,7 is deemed to be the best compromise of spl, impulse answer, enclosure size and how deep it will go. The Qt can't ever be any lower than the Qts in any enclosure. A Qt below 0,5 is overdamped and does not have an overswing but takes a lot longer to return to the resting position too, just staying in the positive excursion instead of the overswing into the negative (inwards) excursion. As you can see here, it takes even longer to return to the resting position than higher Q factors:
A low Qts means, it's a lot quieter at the fs/fb, even if the input power is the same, or, in other words, it moves less air. If you want it to be linear, you have to do something against that fall off, like BR. For BR i.e. it's good to use a low Qts since the enclosure/port will rise the Qt very much. On a sealed enclosure the size of the enclosure, the volume, increases the Qt. Usually, in most rooms you get resonances at different frequencies, depending on the size of the room (room modes -> wavelength of the frequencies), so a slow slope will get you mostly linear as it compensates for the room gain.
Low Qts drivers are made for bassreflex (and generally, horns too) and they aren't good in a sealed enclosures because they are simply not loud enough for the low frequencies, unless they have a very low fs. On an OB you have a lot less room influence and therefore much less room gain too. And you don't have any Q increase from the enclosure either, because, well, there is none. That means you generally already need a higher Qts on your driver to get to the same response in a sealed or even ported enclosure.
The high spl of the bass driver in the specs does not apply in the deep bass. As already explained, the level of the low Qts driver will be a lot quieter. The drop at the proposed crossover frequency of 70 or 75 Hz will be approximately 5dB lower without the crossover than the level of the Supravox driver above it, and you can't increase the level with a passive crossover - which in turn means, you can hardly hear the difference and you can't fix it (passive) either.
So, for an OB, to use a low Q driver is the most expensive way to prevent deep bass.
To go passive, you need a much higher Qts so it reaches the level of the Supravox. Since you don't want that, there are only two things as solution.
1. Use more 15" drivers in the sub range and push the Qt slightly, likely 18dB crossover. A 2nd 15" would give you +3dB by double the cone area and +3dB because the halved impedance doubles the power drawn from the amplifier. You mentioned a tube amp. I don't know if the amp would be happy about the lower impedance. Also, the coils would get much more expensive since lower (half) impedance means double the inductance and for 18dB you need two per side. The DCR of the coils will rise the Qt but added DCR ofcourse decreases the spl. A lot of compromises and 'IF's.
2. You stay at an active solution, preferable with a dsp. That would solve all your problems and still be cheaper.
A-hem..!
Good catch. Thank you, ofcourse it's the other way around. I was writing about twice as much coils costing ~twice as much than 6dB and was editing while writing and obviously went braindead while doing so.
Sry. 
It is irrelevant, because the level of precision and accuracy that the OP is basing his decision on won't happen in a single-element passive filter operating this close to fs
This is why ICG suggested an active filter in post #19, to test and see if 1st order would be satisfactory before attempting to design a passive implementation.
All IMHO, this is.
Well said, but needs to consider that a 1st order active filter is usually not equal to single element passive filter. Mainly due to the variable impedance of the driver.
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Fixed.
Right. I'm reading this thread as a technical exercise to learn a bit more. I think ICG and OP have a slight misunderstanding. I believe OP wants to level the FR, not cut it after 70/75 Hz.
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