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post #31 of 244 Old 12-10-2011, 11:31 AM
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"While I am at it I am going to do a test with the drivers push / pull to see if it lowers distortion compared to push / push."

that will only help with second order distortion, right? if so, that would seem to be pretty far down the priority list.

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post #32 of 244 Old 12-10-2011, 12:22 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

"While I am at it I am going to do a test with the drivers push / pull to see if it lowers distortion compared to push / push."

that will only help with second order distortion, right? if so, that would seem to be pretty far down the priority list.

Shouldn't be much more than flipping a driver, rewiring and a couple of extra measurements. There's really no reason not to try it. I'd rather see for myself what happens than just make assumptions.
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post #33 of 244 Old 12-10-2011, 01:02 PM
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"I'd rather see for myself what happens than just make assumptions."

i'm with you and won't disagree with kicking in additional empirical data. that is always good.

i thought my comment was just straightforward physics. by front-back mounting the drivers, you will be minimizing the linear distortion (even order) products--averaging the weak leg of driver 1 with the strong leg of driver 2, you get the same response as the weak leg of driver 2 and the strong leg of driver 1. the "in stroke" vs. "out stroke" differential in bl, kms, etc. is what creates even order distortion. all the non-linear distortions (odd order harmonics) will remain. the odd order harmonics are the worst and need to be dealt with inside the motor. they can't be tamed outside the motor, except by adding lots of drivers which of course reduces lots of problems inside the motors...but that is not a mounting issue, rather a number of drivers issue.

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post #34 of 244 Old 12-10-2011, 03:31 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

"I'd rather see for myself what happens than just make assumptions."

i'm with you and won't disagree with kicking in additional empirical data. that is always good.

i thought my comment was just straightforward physics. by front-back mounting the drivers, you will be minimizing the linear distortion (even order) products--averaging the weak leg of driver 1 with the strong leg of driver 2, you get the same response as the weak leg of driver 2 and the strong leg of driver 1. the "in stroke" vs. "out stroke" differential in bl, kms, etc. is what creates even order distortion. all the non-linear distortions (odd order harmonics) will remain. the odd order harmonics are the worst and need to be dealt with inside the motor. they can't be tamed outside the motor, except by adding lots of drivers which of course reduces lots of problems inside the motors...but that is not a mounting issue, rather a number of drivers issue.

I still don't understand what your point is John?... Is what my point was! The above description has been known for a long time sure. You seem to be saying don't waste your time or something to that effect. We know how airplane wings achieve lift, but at some point you still need to put them into a wind tunnel right? Can you tell me how much the even order distortion will be reduced, or over what range with the particular drivers and cab shape used? Maybe there is a huge difference, or maybe it is not much at all. There seems to be a limited number of good quality public measurements of the difference. It will be relatively quick and easy so why not.
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post #35 of 244 Old 12-10-2011, 04:30 PM
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"I still don't understand what your point is John?"

odd order harmonics are the offensive aspect in subs.

changing push/push to push/pull doesn't address odd order harmonics.

that's all i was saying.

i was just trying to put some color around what that means for the peanut gallery who may be following along.

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post #36 of 244 Old 12-10-2011, 05:42 PM
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Ricci will you get a chance to put the Othorn on there?

Oh and do you think you will ever get a chance to test any more of the Danley stuff?(TH50, TH212, TH412)
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post #37 of 244 Old 12-10-2011, 08:48 PM
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Quote:
Originally Posted by Ricci View Post

I still don't understand what your point is John?... Is what my point was! The above description has been known for a long time sure. You seem to be saying don't waste your time or something to that effect. We know how airplane wings achieve lift, but at some point you still need to put them into a wind tunnel right? Can you tell me how much the even order distortion will be reduced, or over what range with the particular drivers and cab shape used? Maybe there is a huge difference, or maybe it is not much at all. There seems to be a limited number of good quality public measurements of the difference. It will be relatively quick and easy so why not.

Yes, if looking at a single frequency sine tone with harmonics on a graph, I could probably venture a pretty close guess at the reduction in 2HD and 4HD.

What I found in messing with the 1 driver inverted tests is that a)it takes a very special driver so that driver self-noise isn't worse than the benefit in even order harmonics, b) when even order harmonics are reduced, the balance of harmonics is grossly tilted toward odd order harmonics, and most people I asked preferred the even order balance vs the tilted-to-odd-order presentation and c) the difference is audible only when seriously driving the subs, which is not the preferred method of operation in actual use, making the whole thing a moot point in the end.

IOW, if you do the test, LMK how it sounded to your ears because self noise will most likely be out of band of your graph and resulting data.

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post #38 of 244 Old 12-11-2011, 06:47 AM - Thread Starter
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Quote:
Originally Posted by bossobass View Post


What I found in messing with the 1 driver inverted tests is that a)it takes a very special driver so that driver self-noise isn't worse than the benefit in even order harmonics, b) when even order harmonics are reduced, the balance of harmonics is grossly tilted toward odd order harmonics, and most people I asked preferred the even order balance vs the tilted-to-odd-order presentation and c) the difference is audible only when seriously driving the subs, which is not the preferred method of operation in actual use, making the whole thing a moot point in the end.

IOW, if you do the test, LMK how it sounded to your ears because self noise will most likely be out of band of your graph and resulting data.

Bosso

Agreed on all of the above. I don't think the harmonic distortion reduction will outweigh the drawbacks. There are people who believe otherwise though.
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post #39 of 244 Old 12-11-2011, 11:05 AM
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m&k was one of the more famous. attachment.

i don't recall reading about any of the problems that bosso mentioned from folks who used it. it also showed up in a fair number of recording studios for whatever that is worth. it was considered pretty good at the time. maybe it just depends on the design of the driver and we will never know how much having a "cool look" and a different design in the crowded market figured into the decision. may have been more marketing than performance.

ricci, re-reading my posts today it sure sounds like i was saying that giving it a shot isn't worth it. of course, i agree that testing is always good. i look forward to your findings.
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post #40 of 244 Old 12-11-2011, 11:22 AM
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Nice work!

Great site for DIYers!

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post #41 of 244 Old 12-12-2011, 10:32 AM - Thread Starter
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Quote:
Originally Posted by chrapladm View Post

Ricci will you get a chance to put the Othorn on there?

Oh and do you think you will ever get a chance to test any more of the Danley stuff?(TH50, TH212, TH412)

Sure but don't hold your breath, it will probably be 3-4 months.

Probably not unless it is loaned from owners or DSL themselves..
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post #42 of 244 Old 12-12-2011, 11:08 AM - Thread Starter
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BTW does anyone know where I can source a very cheap Bose system or just the bass module?
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post #43 of 244 Old 12-12-2011, 12:31 PM
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post #44 of 244 Old 12-12-2011, 03:40 PM - Thread Starter
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Cheaper would be better...Like getting one on loan or something. I really don't want to pay $150 out of pocket.
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post #45 of 244 Old 12-12-2011, 06:57 PM
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Josh... man, I keep going to DataBass all the time. I find myself looking over all the tests you've done and I make a stop at your XXX18 LLT. Then I look at my subs... both of them. I scratch my head. I set the bar WAY too high. Not sure if quad 18's will keep me happy. Aye aye aye!

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post #46 of 244 Old 12-12-2011, 07:08 PM
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If you don't have room gain you might be disappointed but Ricci's XXX drivers are a whole new ballgame as low end is concerned.
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post #47 of 244 Old 12-13-2011, 03:25 AM
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Fantastic site, thanks for it Ricci. I was checking around the original blog-announced date, after a while wondering if the update would ever come, now it's up! Awesome! Thanks!

I think it's already on your list but I'm interested to see how a Tuba HT of some sort shakes out.

Quote:


BTW does anyone know where I can source a very cheap Bose system or just the bass module?

Maybe just ask around, they are so common I bet friends or coworkers know someone who has one that you can borrow it from. If not then congratulations.
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post #48 of 244 Old 12-13-2011, 04:54 AM
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Just wondering more on the BC 21". How do you break this driver?

I am not trying to but wondering more about what you said on the driver not going past 20mm excursion. And you were saying when playing in free air it would not go past 20mm. SO I wondered.

Especially with Johns TH221 needing a hpas I just wondered if it can play at high voltage with sine waves and not get hurt what would it matter in the TH221 design.

Just curious is all.
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post #49 of 244 Old 12-13-2011, 08:28 AM - Thread Starter
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Quote:
Originally Posted by chrapladm View Post

Just wondering more on the BC 21". How do you break this driver?

I am not trying to but wondering more about what you said on the driver not going past 20mm excursion. And you were saying when playing in free air it would not go past 20mm. SO I wondered.

Especially with Johns TH221 needing a hpas I just wondered if it can play at high voltage with sine waves and not get hurt what would it matter in the TH221 design.

Just curious is all.

Why would you want to break the driver?

You don't break this one. It is very robust and you would have to do something incredibly harsh to mechanically break it if even that would work. You are more likely to smoke the coil. That is going to take some effort with a 6" vc too. At about 20mm excursion (which is just my estimate BTW) it starts to make a tapping noise and the distortion goes up dramatically. The spiders seem to be stretched and the motor force has dropped off dramatically by then. You would not want to be bouncing it or any driver off of it's mechanical limits either from a perspective of sound quality or driver longevity. Sure they make take a lot of power without damage in the TH221 or another TH, but way below cutoff it will be highly distorted and have little output, so there is no point in it. What you will mostly get is distorted output and driver flapping sounds. There is no reason to push the driver extra hard for that.
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post #50 of 244 Old 12-13-2011, 01:10 PM
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BTW does anyone know where I can source a very cheap Bose system or just the bass module?

Haha, I would love to see tests of these

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post #51 of 244 Old 12-13-2011, 01:45 PM
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Haha, I would love to see tests of these

As would I. Watch out for roving gangs of Bose lawyers though
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post #52 of 244 Old 12-13-2011, 11:58 PM
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Quote:
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At about 20mm excursion (which is just my estimate BTW) it starts to make a tapping noise and the distortion goes up dramatically. .

20mm one way or p-p?

Thanks
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post #53 of 244 Old 12-14-2011, 01:01 AM
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20mm one way.

I was not trying to break the driver just learning more about it. And as you put it I can see why I would just have to design the woofer to not go past about 20mm and be fine.

Did you ever get a chance to test out one of the RCF 21's?

Still amazed at what the Gjallerhorn does in comparison to the DTS10.

And just as Scott does I keep going back to look at the different designs and tests. Awesome again.
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post #54 of 244 Old 12-14-2011, 01:02 AM
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With my sim. the excursion don't exceed 12mm one way with double 21" loaded in 140lt and 4000w (2000w per driver, 52A).
Ok, my sim. was done with Beyma woofer, but I think they are not too different.
To reach excursion above 20mm the drivers must be loaded in 300lt at least.

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post #55 of 244 Old 12-14-2011, 03:08 AM
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Quote:
Originally Posted by aackthpt View Post

Fantastic site, thanks for it Ricci. I was checking around the original blog-announced date, after a while wondering if the update would ever come, now it's up! Awesome! Thanks!

I think it's already on your list but I'm interested to see how a Tuba HT of some sort shakes out.



Maybe just ask around, they are so common I bet friends or coworkers know someone who has one that you can borrow it from. If not then congratulations.

Before mine gets finished, I will haul it outside and test it.

JSS
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post #56 of 244 Old 12-14-2011, 03:13 AM
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Maxmercy are you building another THT or something else?

I only asked because I thought you had two already.
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post #57 of 244 Old 12-14-2011, 07:44 AM - Thread Starter
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Scorned99,

I will have 12,000w on tap from a 240v line so I should be able to get to the limits on the dual 21 opposed sealed sub this time.



Quote:
Originally Posted by chrapladm View Post

20mm one way.

Correct.

Quote:
Originally Posted by chrapladm View Post

I was not trying to break the driver just learning more about it. And as you put it I can see why I would just have to design the woofer to not go past about 20mm and be fine.

That's what I did with my vented cabs and with the Othorn was simulate with about the most power anyone would strap to one by itself (4000w / 120V) and tried to keep the excursion no greater than 20mm peak in the pass band.

The woofer simply will not go past about 20mm which is great. It does not sound great at that excursion level though. You actually need to keep it a little lower than that to maintain clean sound. For example look at the THD test for the ported 21sw152. On the 125dB sweep the THD is still very good in the passband, but once the level is brought up to the 128dB sweep level () the woofer is getting driven to it's excursion limit near 40Hz and the distortion takes a big jump.


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Did you ever get a chance to test out one of the RCF 21's?

Not yet. Too much on the docket currently.
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post #58 of 244 Old 12-14-2011, 08:01 AM
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Quote:
Originally Posted by chrapladm View Post

Maxmercy are you building another THT or something else?

I only asked because I thought you had two already.

The second one is complete but unfinished. When i move that behemoth to the shop to stain and lacquer, it'll stop at the driveway 50+ ft from all boundaries and get a proper workout...

JSS
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post #59 of 244 Old 12-14-2011, 09:49 AM
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Quote:
Originally Posted by chrapladm View Post

And just as Scott does I keep going back to look at the different designs and tests. Awesome again.

LOL!!!

I know... I'm terrible but I've got nothing but time so I like to go back and perfect whatever it is I'm working on. I'm sure this has absolutely nothing to do with why my latest project is taking so long. Yyyeaahhh...

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post #60 of 244 Old 12-14-2011, 10:48 AM
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Quote:
Originally Posted by maxmercy View Post

Before mine gets finished, I will haul it outside and test it.

JSS

It will be nice to get some actual measurements of the Tubas as the lack of from the designer is a strange oversight. Or not.
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