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post #151 of 752 Old 09-09-2011, 07:59 PM
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Originally Posted by Eternal Velocity View Post

Um.. what?

Good question. Who knows what I was thinking.

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What advantage would there be to not using any shorting rings?

None. See final (I hope!) edits.

Not my day, I guess.

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post #152 of 752 Old 09-09-2011, 10:15 PM
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I'm not much of a subwoofer guy. Why is inductance so important? Don't most people XO their subs before inductance would influence the impedance that much?
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post #153 of 752 Old 09-09-2011, 11:03 PM
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Originally Posted by tuxedocivic View Post

I'm not much of a subwoofer guy. Why is inductance so important? Don't most people XO their subs before inductance would influence the impedance that much?

This is my limited understanding.

The inductance has effect on how quickly the cone can change direction. While this applies to the higher frequencies, it can also apply to playing the lower frequencies "cleaner".

I hope I am not too far off base.
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post #154 of 752 Old 09-10-2011, 01:27 AM
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Scott I think Mark did say he could do the subs in 8 ohm. I was always asking questions about the 21" so I could be wrong. Maybe I should just get four 8ohm subs to run in four ohm stereo on the Fp14000. IDK
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post #155 of 752 Old 09-10-2011, 01:48 AM
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That's kind of what I'm thinking of doing for my quad RLp18's. They are all dual 4ohm so two pair in dual opposed would be perfect with a single FP14k. I'd really like to do the same with these. I've also looked at using four of these in a single cab for the end 4ohm load but that would require a huge amp such as the 14k and used bridged which Bosso says is not recommended. Though I am to believe that it would not be a good idea with high levels sines and all that. In normal home use and especially used in a system with other high output subwoofer, I doubt it would be an issue to run the 14k bridged but umm... I really don't know for sure. Just speculating.

If I could get them single 8 or dual 4, ah, that would be perfect for me. I'd rather get the two 14k's and run them in a way that they are stable. 2200w per driver is quite a healthy amount. My model sims of these show that they can mechanically take 5kw in a small, sealed enclosure of ~2cuft. That's a bit much though. I think it's pretty cool that I could make a balls to the wall 20kw subwoofer system and take up very little floorspace and easily produce reference levels down to the single digits. Incredible.

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post #156 of 752 Old 09-10-2011, 02:25 AM
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Quote:
Originally Posted by tuxedocivic View Post

I'm not much of a subwoofer guy. Why is inductance so important? Don't most people XO their subs before inductance would influence the impedance that much?

I think what we're probably interested in, isn't `Voice Coil Inductance - inductance in terms of its effect on "stored energy/driver rolloff/frequency response transfer function". That just tends to be a bit of an "indicator" of motor optimization...

I think what we're truly looking for, is Le(x) - inductance linearity as a function of cone travel.. kind of like how a BL (motor strength) changes as excursion rises (and less so for underhung / XBL^2 type motors), so too does inductance (and less so for inductance optimized motors).

Correctly placed shorting rings / sleeves / etc can really reduce motor distortion.

Now I'm not John Janowitz/Kevin Haskins/Mark Rogowski/Thilo Stompler so I couldn't tell you a thing about driver design. Here's a link to some of John Krutke's Le(x) measurements though, and his explanation which is better than what I can do:

http://www.zaphaudio.com/Le%28x%29/
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post #157 of 752 Old 09-10-2011, 02:35 AM
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Well said, EV.

It's not all about the absolute number but the linearity of the inductance. Though I believe, in general, that all things being equal the lower the inductance the better.

As for the effects on a subwoofer system. I'd say it has a lot to do with how well said subwoofer can blend with other speakers. It will be easier to cross a low inductance woofer @ 120hz than a high inductance woofer.

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post #158 of 752 Old 09-10-2011, 05:06 AM
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Quote:
Originally Posted by Scott Simonian View Post

That's kind of what I'm thinking of doing for my quad RLp18's. They are all dual 4ohm so two pair in dual opposed would be perfect with a single FP14k. I'd really like to do the same with these. I've also looked at using four of these in a single cab for the end 4ohm load but that would require a huge amp such as the 14k and used bridged which Bosso says is not recommended. Though I am to believe that it would not be a good idea with high levels sines and all that. In normal home use and especially used in a system with other high output subwoofer, I doubt it would be an issue to run the 14k bridged but umm... I really don't know for sure. Just speculating.

If I could get them single 8 or dual 4, ah, that would be perfect for me. I'd rather get the two 14k's and run them in a way that they are stable. 2200w per driver is quite a healthy amount. My model sims of these show that they can mechanically take 5kw in a small, sealed enclosure of ~2cuft. That's a bit much though. I think it's pretty cool that I could make a balls to the wall 20kw subwoofer system and take up very little floorspace and easily produce reference levels down to the single digits. Incredible.

I was referencing a Brit's test results (the Chas of the Euro-zone) wherein the clone crapped out during the 2 ohm stereo test. Unfortunately, he started the testing with this so no further performance data was available.

Now, that was almost 2 years ago when I was looking into the clones to buy a few and test them for my app, so I don't know if the latest iterations are improved in that respect or not. I've had Chinese engineers tell me that most clones are not recommended to be bridged 4 ohm with 115V-60 Hz operation.

I can tell you that after I had a clone fail spectacularly (not a Lab clone, but a similar platform) and read of the Lab clone test fail I connected 2 of them, each to a 4x15" system, one 4 ohm stereo and the other 4 ohm bridged. I haven't had any problems to report, but then again I always operate my system within its limits. IOW, I don't push hardware to find its destruction point, just its ideal performance limit in my app.

I agree, the FP14000 should be good in 4 ohm bridged mode if the VPL and gain structure are properly set up and the warning lights are observed with common sense.

Just an opinion, YMMV.

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post #159 of 752 Old 09-10-2011, 08:32 AM
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Thanks guys. Yes, Le(x) makes a lot of sense considering these subs are high excursion.
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post #160 of 752 Old 09-10-2011, 02:36 PM
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What about the tall rubber surround? Is that option available?

It is, but mark says the tall surround will bump the Fs up to +/- 30Hz. In turn the Mms, Cms, and Qms will also be altered. I am heavily considering the option, but need a) a little more time to think about it and b) T&S specs from the finished driver with the tall surround.

But with that said, I think the "standard" Pi-18 looks pretty damn incredible as is
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post #161 of 752 Old 09-10-2011, 07:02 PM
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If they are 4 ohm you could with two have them four ohm stereo. Then if the you have four of them you could have the them four and us the amp in bridged if it will allow.

I think I would only need 8ohm bridged power for me. 8800 watts seems like it might be enough. But just as Bosso said use these with in reason and you should be fine.

I would figure that anyone who has one of these amps and four 18's wouldn't be able to hurt the amp before seriously hurting themselves or walls.

I dont know much about amp abuse but if running sine waves wouldn't the sub blow before the amp?

I know the most subs are not going to take 10hz at full power. But either way I will be on 240Vac so hopefully that will be good for me.

I just hope the VPL always works and I set everything up so I wont have to worry. If they only come in 4 ohm I will just have to use the amp in stereo mode. Which is roughly what Mark suggested with a few db of headroom.
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post #162 of 752 Old 09-11-2011, 06:49 AM
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I've been playing around with Hornresp and the Pi18... I got some very interesting models, but unfortunately, 25-30cf is a bit too big enough for my basement.
OTOH, it does reach some disgustingly sweet numbers down low (I entered 2kw power input and 30mm Xmax and got over 130db @ ~18hz :O)

I'm still quite a n00b at Hornresp but for the infrasonic stuff, it may just be better to go ported... thoughts?
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post #163 of 752 Old 09-11-2011, 06:51 AM
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Are these babies available yet?

21"ers? Link?

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post #164 of 752 Old 09-11-2011, 07:04 AM
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I'm still quite a n00b at Hornresp but for the infrasonic stuff, it may just be better to go ported... thoughts?

It's a good tapped horn driver with the current specs, but it likes to be at an Fc I consider too low to play with in a horn. Box just gets too big to be practical.
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post #165 of 752 Old 09-11-2011, 05:36 PM
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Quote:
Originally Posted by Viperoni View Post

I've been playing around with Hornresp and the Pi18... I got some very interesting models, but unfortunately, 25-30cf is a bit too big enough for my basement.
OTOH, it does reach some disgustingly sweet numbers down low (I entered 2kw power input and 30mm Xmax and got over 130db @ ~18hz :O)

I'm still quite a n00b at Hornresp but for the infrasonic stuff, it may just be better to go ported... thoughts?

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It's a good tapped horn driver with the current specs, but it likes to be at an Fc I consider too low to play with in a horn. Box just gets too big to be practical.

ooh ooh!
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post #166 of 752 Old 09-11-2011, 05:44 PM
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practical.

Hi, sorry, what does this word mean?

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post #167 of 752 Old 09-11-2011, 05:50 PM
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I want solid output to 3Hz at reference, but if I can get down to 30Hz with a shoebox instead we'll just call it good enough.
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post #168 of 752 Old 09-11-2011, 05:54 PM
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Hi, sorry, what does this word mean?

Not sure, but I've heard it come up in a few conversations, and figured it would be a good one to use to make myself sound smarter

Seriously though, you're looking at a thousand liters before materials with this driver for anything decent in a TH. It's a lot like the old IXL 18" in that way, though it will work in slightly less space than that driver would.
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post #169 of 752 Old 09-11-2011, 06:12 PM
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I want solid output to 3Hz at reference, but if I can get down to 30Hz with a shoebox instead we'll just call it good enough.

Hardy har har.

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post #170 of 752 Old 09-11-2011, 07:24 PM
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Are these babies available yet?

21"ers? Link?

??

Never mind, I found it in another thread.

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post #171 of 752 Old 09-11-2011, 07:28 PM
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Hardy har har.

what I say!

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post #172 of 752 Old 09-11-2011, 07:29 PM
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Where is any info available on he 21's? I have heard them mentioned several times in posts around here but have not seen anything as far as pricing or specs.

War Eagle!
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post #173 of 752 Old 09-11-2011, 07:32 PM
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I dont believe pricing and specs are available yet. 1 at a time, 18s just came out, 21's will follow.
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post #174 of 752 Old 09-11-2011, 07:36 PM
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Understood, but from what I read there was a run already and they were presold? Is that not correct?

War Eagle!
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post #175 of 752 Old 09-11-2011, 07:37 PM
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I dont believe pricing and specs are available yet. 1 at a time, 18s just came out, 21's will follow.

21s are where it's at!

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post #176 of 752 Old 09-11-2011, 08:19 PM
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Are the 15"-ers on the way as well?

In terms of LFE, size does matter!
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post #177 of 752 Old 09-11-2011, 08:35 PM - Thread Starter
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Understood, but from what I read there was a run already and they were presold? Is that not correct?
No it was just to see how much interest there was. Some people put money down so then he knew he had enough interest to start the process of building and designing them.

Blasting brown notes for 10 years and counting!

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post #178 of 752 Old 09-11-2011, 08:45 PM
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21s are where it's at!
That's what I'm lookin at!
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post #179 of 752 Old 09-12-2011, 12:12 AM
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Wiring options. You must not have multiple subs or an IB. It can make you life much easier.
Slowly adding more, but I use individual amp channels/driver, or in some of the new2x12 units 2 drivers parallel/channel. Choose the right amp and it's no issue.
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Using test tones or in peaks in movies or music, you can EASILY go over the power rating for the sub. Does it happen all the time? probably not but if you run you system hot, then yuppers.
Dual coils are typically half the rating of a single for the same driver, so this makes no sense to me. There is only a limited area in the gap and former length to place the coils.

There is no need to run test tones at high levels for long periods to test, and the peak to average ratio of most soundtrack material leaves plenty of time for even hard used coils to cool. Splitting them will make no difference here.
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post #180 of 752 Old 09-12-2011, 12:25 AM
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Quote:
Originally Posted by Eternal Velocity View Post
I think what we're truly looking for, is Le(x) - inductance linearity as a function of cone travel.. kind of like how a BL (motor strength) changes as excursion rises (and less so for underhung / XBL^2 type motors), so too does inductance (and less so for inductance optimized motors).

Correctly placed shorting rings / sleeves / etc can really reduce motor distortion.

Now I'm not John Janowitz/Kevin Haskins/Mark Rogowski/Thilo Stompler so I couldn't tell you a thing about driver design. Here's a link to some of John Krutke's Le(x) measurements though, and his explanation which is better than what I can do:

http://www.zaphaudio.com/Le%28x%29/
As the linked discussion is about widerange drivers, not dedicated LF drivers, typically steeply rolled off at <100hz, it is not compelling evience to me that shorting rings make any difference at LF.

If you have some objective evidence to make for the sub case, especially for dedicated sub drivers, then I'd love to read it. Just on rings at LF, not different motor geometries.

edit: found in my bookmarks; here are some FEA sims of the magnetic structure of some different layouts at 1khz and 100Hz using shorting rings, but in a JBL style differential drive motor.
http://www.diyaudio.com/forums/multi...tml#post706194
http://www.diyaudio.com/forums/multi...tml#post706701

I also have a paper stored somewhere on my system that I can't find currently that also found the same. I'll post it when I did it up.

Edit 2: from Wayne Parnham:
Eminence found that they were unable to get significant distortion reduction below 150Hz from a shorting ring. The reason is pretty simple - The shorting ring works like a transformer winding, and it has to inductively couple enough energy to create a magnetic field large enough to offset the difference in force caused by flux modulation. As frequency goes down, this becomes harder and harder to do and the size of the ring becomes prohibitively large. The volume displaced by the ring makes magnet size smaller so more magnet has to be added to compensate and the requirements become a vicious cycle. So there just isn't enough "meat" to make a good flux stabilized subwoofer.
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