Not yet. I was making sure my wiring package was exactly right and just made it's first sound today. I will get my mixer and PC out and do so soon though, maybe this weekend.
Put a white dot on the cone, watch it as you sweep up/down around Fb, it will be at minima at Fb. If to high, refer back to my earlier suggestion in post # 8, not too late for an interior change.
One thing to consider when setting your HP filters: a slapped bass can put out to nearly DC, set your HP only a few Hz below Fb, unless you'd like the ports to fan your ankles and the voice coils to char ;^).
One thing to consider when setting your HP filters: a slapped bass can put out to nearly DC, set your HP only a few Hz below Fb, unless you'd like the ports to fan your ankles and the voice coils to char ;^).
Is this the preferred method? I thought we could measure impedance or something...
Is it important to nail my Fs exactly? I'm guessing it will be within a few Hz, but as long as it's pretty close we should be good, right?
Boy don't I know that. I blew up my first speaker doing that in my 20's, and it took me a few more expensive little mistakes to get that through my head.
For this particular box I believe I have the amp set with a Highpass starting at about 28-30 Hz or so.
I never did understand what you were getting at. My port ends are flared a bit, but did you mean like an 'L' shape? I don't understand what 'Top Hat' meant, and the illustration didn't get it across.
Well, the cabinet won't unload on your 40 Hz low E, but the cone will flap on the Low B with a fraction of the power you have available. You could extend the port with an "L" shape on the inside ends to lower tuning a bit below the "B", 31 Hz. The "L"end shape will both lower the tuning and increase the symmetry of the port response.
Alternatively, you can use a BW 24 HP filter at about 35 Hz for the gigs you need the extra output on, and cover one port (hard foam jammed in works well) for the lower tuning when you don't need quite as much volume, with a HP just below Fb . That said, the lesser port area will chuff more, if you want 30 Hz response without "port compression" the ports need to be extended.
Have Fun,
Good Luck!
Art
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Yes, you can literally see it begin to uncouple at about 35 Hz.
I have quite a bit of room behind the ports, Does it have to be an 'L'? Could I just extend the ports? This would be way simpler than the geometry necessary for an L-shaped trapezoid.
I have it set now with a BW HP at 35. It does roll off sharply, but it's very smooth, I can hear 30-32 Hz before the roll-off becomes audible. At 28-29 though, it's dropped a great deal. I think it'd be better to extend port length if I feel I need that extra 5 Hz. I know myself - I'm too lazy to take grills off and stuff ports. The box is already plenty loud enough, Extending the ports may be what I do in the future. I want to hear it in real world a few times first.
Thanks, this has been a really fun and educational project!
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1) It does not have to be an "L". You seem to want the real shiz, but don't want to do the little bit extra to bring it to "11" so do whatever..
2) Yes, below tuning (Fb) a ported box of reasonable size (like yours) drops at 24 Db per octave, and your hearing becomes less sensitive down low too- if you play an instrument with a low "B", and actually want to hear the fundamental with "authority", the tuning must be at least that low. That said, you trade output for extension. As I mentioned to you on PSW, and you agreed, you don't want to compete in the low mids- but "getting er done" from E down to the B is a big hit.
3) Efn hell, just do it then, don't wait for the future, or we'll see you in the pasture, and pick mushrooms from your droppings ;^).
Cheers,
Art
Oh - okay cool, I mistook that making an 'L' was your suggestion. Extending it is as easy as, well, extending it. I'm going to listen and play through it a while before doing that, but it won't be difficult if I do.
I do play a 5, but most often I play a 4, and even when I do play the 5, there are only 3 notes which won't be heard. Again, I still want to play through it. If I have volume to spare at 40 Hz, I will definitely extend those ports.
Right 😉
Aww heck. Okay, I'm doing it. I've heard it now, the box is already plenty loud, I can sacrifice a few (non-audible) dB for a flatter curve down to 31-32 Hz.
Doing so requires extending my ports by 8 inches. I'll still have about 5 1/2 inches of clearance to the back. The clearance will still have a larger area than the cross-section of the port by a good margin, so I don't think I'll run into any chuffing issues that don't already exist.
So, I did it, and RAISED the Fb to about 43 Hz????
Only thing I can think is that there is about 4 inches clearance from the back. This still gives me about 175 sq.in. of area, I doubt that's the issue. Hmmm.
Only thing I can think is that there is about 4 inches clearance from the back. This still gives me about 175 sq.in. of area, I doubt that's the issue. Hmmm.
There's no chuffing - in fact, it's quieter than before as far as noise. Further, it seems *subjectively* to me to be smoother. Could it be that 30Hz takes a whole lot more excursion than 40 Hz to make the same volume? I'm completely confused...
I am a SUPER genius. Like, Wile E Coyote brilliant.
Be sure both the Hi-Pass portion of the crossover and the Hi-Pass filters are disengaged before running resonance tests. I'm just that smart 🙂
Anyhow, now it works like the Win ISD model predicts. Fb is easy to see right at 29-30 Hz. The cones noticeably un-couple at anything significantly lower. I haven't gotten really loud yet, but there is no port noise at all so far.
So, now the big question. My EQ HP filter was set for 20Hz with a pretty sharp Q. I also had set the HP of the X-Over to BW 48 @ 27 Hz. I tried using both and separately when I was setting them up before. Yet, as I've just seen, these still interfered a lot with the response from my sub.
I know there's a curve above the set frequency, but I tried to minimize this as much as possible, by going a bit lower. Still, it had undesired effects.
I must protect from frequencies below resonance. I do a lot of thumb-popping, which will send a DC square wave at them if I'm not very careful. Even with lots of care, the thumb thing really abuses woofers.
Is it that the EQ and X-Over in the Crown XTi series is less than great? Should I set them lower? I need 31Hz, but need to protect from 20 Hz.
Be sure both the Hi-Pass portion of the crossover and the Hi-Pass filters are disengaged before running resonance tests. I'm just that smart 🙂
Anyhow, now it works like the Win ISD model predicts. Fb is easy to see right at 29-30 Hz. The cones noticeably un-couple at anything significantly lower. I haven't gotten really loud yet, but there is no port noise at all so far.
So, now the big question. My EQ HP filter was set for 20Hz with a pretty sharp Q. I also had set the HP of the X-Over to BW 48 @ 27 Hz. I tried using both and separately when I was setting them up before. Yet, as I've just seen, these still interfered a lot with the response from my sub.
I know there's a curve above the set frequency, but I tried to minimize this as much as possible, by going a bit lower. Still, it had undesired effects.
I must protect from frequencies below resonance. I do a lot of thumb-popping, which will send a DC square wave at them if I'm not very careful. Even with lots of care, the thumb thing really abuses woofers.
Is it that the EQ and X-Over in the Crown XTi series is less than great? Should I set them lower? I need 31Hz, but need to protect from 20 Hz.
What's the question ;^)?
I have not played with the Crown XTi series, but there is a chasm between digital filters, the agreement between what the panel says and what the filters do is not the same between different manufacturers, and even different series of some manufacturers.
Bottom line, just do what works- watch the cone while you pop and slap, adjust the HP as low as you can go without affecting the low B, yet staying under Xmech. Try the BW24 instead of 48 while you are at it, may be the "ringing" of the steeper filter is not to your liking, especially if you are stacking two filters.
On a related "note", I have been going through a similar process with tuning my new Keystone B-Low subs, so can relate to your previous posts you answered yourself, Coyote :^).
After hours of messing around with Smaart, finally got the old measurement system working again on a "new" old laptop, first measurements in over a year.
Was surprised to find the new sub's upper end was dropping off almost like a band pass cabinet, and the low end was also dropping just above 40 Hz. On the second day of testing, realized that the NU4-6000 I was using (one of five) had the crossover switch engaged-three of the units "full range" is the center position, two of the units "full range" is to the left, every other bit of the amps seem to be identical...
Disengage the switch, boom, the missing upper range was there, but unfortunately, no increase in the bottom- the LP, if any, must be very low.
I can lower the Fb on the Keystone "B-Low" to 31 Hz by reducing the mouth exit, but then the upper bass takes a big 3-6 dB hit. I have compromised on a 33 Hz Fb, which keeps the upper range happening, and allows hitting 30 Hz flat with EQ, while still keeping the excursion in an acceptable range using a BW24 at 25 Hz.
Cheers,
Art
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Sounds like a good plan - keep efficiency where most of the bass usually is, and EQ and a low Fb to deal with everything below that.
Sorry, rambling... 🙂
I'm learning that. I'm also learning that the input EQ on this unit is much more accurate than the output EQ. I was using my digital mixer to set EQ points, which is easier and much more precise. Then I set the same on the Crown's EQ and went with that. It seems manufacturers haven't optimized this relatively new ability to tune an amp from within via firmware.
Now that I got the Fb mystery figured out, that's where I'm at. Using a dB meter I'm within about 3-5 dB on my slow sweeps. I had to put a 12dB cut at about 55 Hz to flatten the curve somewhat, but it's darned tolerable now.
I'm now perplexed as to why it has such a hump at 50-60 Hz if WinISD says it should be flat.
Absolutely, I use a 24 on the crossover too, and it's a much smoother result. 48 Hz doesn't sound as natural. I'm using a 48 on the HP, as well as a sharp Q parametric EQ at 20 Hz. That seems to keep the Xmech down. Still, I may set the limiter to about -10dB instead of my current -3dB. There's easily enough power to launch these things with a transient. The XTi6002 was a good decision though, my XTi 4000 gets hot fast with sustained lows.
Ever try Room EQ Wizard? I found it on a home theater forum. It's intuitive and very powerful with a rich feature set. Best of all it's free and regularly updated with feedback from a robust support community. My next step is to put this thing outside and analyze using that.
Below about 29Hz, is where mine gets floppy, but you can see it tighten at what I believe is the Fb. From about 29Hz through 60 or so, the excursion stays about the same.
1) Measuring in a room is only useful if the speaker stays in the same position in the room, and your ears stay in the same position as the mic. Room modes make for huge response differences. Last night it took me an hour of moving my sub and microphone around my studio to get anything that looked remotely like the outdoor response.
2) Yes, unfortunately the REW software does not work on my 2007 MacBook, and I hate breaking down my desk 21" iMac for testing. I do plan to get more familiar with REW after I finish the six subs I'm working on now.
3) Definitely do, your basic EQ choices should be done in an open air environment, you can adjust from there for stage and room problems.
4) In a ported cabinet, excursion increases above Fb to a maximum about 1/3 octave above Fb, then reduces above that frequency. You are probably running at levels where excursion is hard to see other than below Fb, where the speaker "unloads" in a matter of a few Hz. Ideally, the HP filter is set so the excursion maxima is the same at a given input level above and below Fb.
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I knew a room will make an enormous difference over outdoors, but wow - a 14dB cut at 55Hz to be relatively flat? Plus, I'm only measuring about 3 feet in front, do you think the room can be that prevalent when I'm that close? That's amazing if so. I'll be loving it if it's within 3-5dB flat outside with no EQ. Maybe I ought to try measuring inside the port?
I think you'll love it. I've used others which cost money which are geared more toward live sound, and honestly, this easily competes with or beats them all in my book. Lightweight, few bugs, intuitive, very responsive.
Cool, I'm on the right track there.
Ahh, excellent, further confirmation I'm spot on. There's a 'twitch' at what I believe is Fb -about 28-30 Hz where the cones 'hook up.' Then excursion is about the same from 30-40Hz, then drops markedly after 40Hz. So, I think my tune is pretty close to the simulation.
To eliminate the room from the tests I did last night required putting the mic against the cabinet face, which still resulting in as much as 4 dB deviation.
Problem with a ported cabinet when measured that close is the inverse distance law- either the port or the speakers front response is bound to be too high depending on placement.
With the mic a meter away from the speaker, responses looked like 20 dB mountain ranges, small rooms (being small relative to a 38' long 30 Hz wave) are terrible as far as point to point response linearity- move your mic another couple feet and your +14 dB at 55 Hz may turn into a -14 dB hole.
After several minutes with pink noise on at a moderate level during the indoor tests, I started feeling a bit queasy. The sub's actual response is around -10 dB at 30 Hz, but putting the mic where I was seated found it happened to be +10 at 30 Hz in that particular position...
One thing you will find when you start gigging is the reduced stage to ceiling height compared to the rest of the room can make the bass sound completely different on stage than in the house- EQ that works for one position on stage may be horrible in much of the room and vice versa. Get a long cord and walk around playing before you spend much time on EQ!
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