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double 18 reflex

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MARTYNJONHALL View Drop Down
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    Posted: 15 November 2007 at 10:22pm

I know the pro's around here will laugh at me,

but has any one got the plans for a cab like this??
im no good at working oout volumes & things but great at the practical side
please help me
thanks to you all in advance
 
i think this cab is a citronic cab?
 
Image%20of%20ULTIMA%20PROFESSIONAL%20SERIES%20SUBWOOFER
its got the external dimensions but its the ports and inner ones that are missing
 
 
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CLsystems View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CLsystems Quote  Post ReplyReply Direct Link To This Post Posted: 15 November 2007 at 10:31pm
have you heard one of these cabs?
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TONY.A.S.S. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TONY.A.S.S. Quote  Post ReplyReply Direct Link To This Post Posted: 15 November 2007 at 11:33pm
When you realize that the sound emitted from the rear of a speaker is the same as the front, I wonder why they bothered to turn one speaker round. Answers on a postcard please.
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CLsystems View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CLsystems Quote  Post ReplyReply Direct Link To This Post Posted: 15 November 2007 at 11:37pm
my guess is they saw a push pull cab once, and in the morning after they got over there hangover they drew the design on a fag packet.
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Mark James View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mark James Quote  Post ReplyReply Direct Link To This Post Posted: 16 November 2007 at 12:04am
http://www.speakerstore.nl/index.php?l=nl&pg=11&c=60
me so horny me love you long throw
horn loaded for her pleasure
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Mark James View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mark James Quote  Post ReplyReply Direct Link To This Post Posted: 16 November 2007 at 12:13am
@tony as guess would be that because the other baffle is behind the front one [if that made sense ie one baffle is further back in the cab] the chamber may be slightly smaller [unless its a single chamber] or the magnet would not fit without hitting the back wall of the cab? just a brief guese
me so horny me love you long throw
horn loaded for her pleasure
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MARTYNJONHALL View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MARTYNJONHALL Quote  Post ReplyReply Direct Link To This Post Posted: 16 November 2007 at 6:43am
so guys, best just build a g sub then??
 
anybody tryed other drivers in them?
 
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heinrich View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote heinrich Quote  Post ReplyReply Direct Link To This Post Posted: 16 November 2007 at 6:53am
looks like Beta3 drivers in there...............
.....power is nothing without control....
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HansA View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote HansA Quote  Post ReplyReply Direct Link To This Post Posted: 16 November 2007 at 7:31am
Originally posted by TONY.A.S.S. TONY.A.S.S. wrote:

When you realize that the sound emitted from the rear of a speaker is the same as the front, I wonder why they bothered to turn one speaker round. Answers on a postcard please.


I don't have your address.

Does not this setup help to cancel out some nonlinearities from the drivers. When coupled in parallel? Thats what I've been thought.
Besides from that its just a narrow reflex cab. Probably for tight "stackabillity". Don't need no plans to do that.
�*�o�O�o�*�*: HansA, The FUBAR sound technician :*�*�o�O�o�*�
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_djk_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 16 November 2007 at 9:08am
If you run them at an angle, they work better this way:
djk
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 16 November 2007 at 9:57am
A quick thumbnail sketch of what I use (no photo available):
Why do push-pull slot-loaded?
The reductions in 2nd harmonic distortion from PP mounting on a flat baffle are well known, the non-linearities are equal and opposite and thus the 2nd harmonic is canceled. Because of the driver spacing it only happens in the bottom octaves. The cheaper the driver, the bigger the improvement. I have measured as much as a 20dB change.

By mounting in a plenum several things change. The spacing becomes much tighter so the cancellation will work at higher frequencies, and a cavity is formed.

The cavity does several things, in no particular order:

The size, especially the depth, acts like a low pass filter. This can reduce 3rd harmonic distortion products near the top end of the passband, the effect is small, but audible. The cavity sizes I use have to be crossed in the 150hz~250hz region. It gives a slope of roughly 12dB/oct that must be taken into consideration in the design of the crossover. There is a small peak about two octaves above this point, ~800hz on many that I have done. By varying the Q of the 12dB/oct lowpass filter a LR4 I can get a LR4 transfer function. This filter also reduces the out-of-band peak to -30dB or better. There is also a big reduction in FMD, on the order of 6dB. The air mass at the exit of the plenum seems to act like a point source with no doppler, the cones are moving back-and-forth sideways rather than towards-and-away from you. At first glance this would seem to eliminate the FMD, in practice the reduction is on the order of 4dB~10dB depending on the frequencies.

I mounted a pair of drivers in another cabinet in a face-to-face, push-push mode. The box became very 'thick' sounding and had a broad peak centered at 160hz, just like the EV MTL4. In room the response of the push-pull was 6dB smoother in the 100hz~200hz octave.

Being compared side-by-side with the Klipschorn and Cornwall was interesting. At first the push-pull sounded 'funny'. Couldn't put my finger on it. Went back to the push-push cabinet. The push-push cabinet had that 'hi-fi' sound, similar to the Cornwall, but a bit 'thicker'. Klipschorn, much cleaner sounding. Back to the push-pull.

The reason the push-pull sounded 'funny' was the total lack of distortion. Much less than the Klipschorn.

I have not built a basshorn since.

I still use horns, but only above 150hz.

There are some drivers that are not suitble for home hi-fi, mainly those with small magnet vents that can make 'chuffing' sounds when up close.

    Posted by djk ( M ) on May 18, 2003 at 02:38:51

    In Reply to: Re: PPSL posted by bmar on May 16, 2003 at 19:26:45:

"Is the equal and oposite reaction limited to 2nd harmonics, and does it make the system less efficient"

Yes, the equal and opposite reaction only reduces 2nd harmonics, it does not change the system efficency.

"With the drivers close together like this. Just how high can this system be used."

The closer the better seems to be the rule as far as HF response goes. A four 12 box I made could be crossed at 400hz, some dual 18 boxes were able to cross at 250hz. The majority that I have built are dual 15 and crossed far enough below where the plenum rolls off to use an off-the-shelf LR4 crossover.

"What kind of parameters do you use when calculating the rear chamber"

Use normal TS parameters and size like a regular box, I use low Qts drivers with a step-down tuning and equalization. Drivers with Qts=.312 give the deepest bass response from the smallest box size. Alternately one can seal the box and use a Linkwitz transform, or leave the back open like the Linkwitz dipole.

"and can you actually build the box so it would act like a low pass filter down to 80hz if needed."

Yes you can, but now you have a bandpass box. That may better suit your needs, and many modeling programs are available for those.

At the time I was looking at both the EV MTL4 and the KEF 104, both had their strengths and their weaknesses. My design had all their strengths and none of their weaknesses.

djk
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_djk_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 16 November 2007 at 9:59am

Post #82
"My only direct comparison with push/pull and non-push/pull pairs was using cheap 12" drivers."

The cheaper the drivers, the more push-pull will help them.

"Are there any (more or less) exact figures you can talk about when it comes to reducing distortion with push pull? And/or how much of a noticeable difference (to the ear) are we talking about?"

Some old comments cut&pasted from elsewhere(sorry, the link is dead):

Kind of like this:

http://cgi.ebay.com/ws/eBayISAPI.dl...Item&item=73392 75215&category=47094&rd=1

This was a box EV came out with after I talked with one of their engineers at a trade show about 20 years ago.

EV showed me the light in 1974 with the Interface A, an SBB4 alignment with a Q=2 filter ahead of the amplifier, so it became a B6.

All my best vented designs were assisted B6 or C6 after that.

Around 1980 a friend of mine that was a FOH engineer with dB Sound turned me on to the (then) unreleased MTL4 design. I thought it was cool, but didn't like the short x-max 18s (I don't like 18s in general), and didn't want to have to use a fork lift to move it.

I built a half-height design with two 15s facing each other on a narrow slot. On one of the pair I mounted the drivers push-pull (the reversed driver hooked up out-of-phase electrically).

This sounded so different I thought it sounded funny (at first).

It sounded funny because it had no distortion. It made a large 40hz bass horn sound distorted in comparison. I had Eminence custom make me a large x-max 15 that had the same volume displacement as a good 18 (and went lower).

Now, of course, we see push-pull boxes from EAW, TAD, etc, although I have not seen any exactly the same as the ones I made.

I took an engineering type job (doing L-band RF stuff for the military) about seven years ago and haven't really made anything much since then. I've been thinking it may be time for another production run as some of my old used boxes are trading hands for more than I sold them for new.

and:

The EV MTL4 has a 6dB peak at 160hz that they eq
out in the crossover. The djk slot loaded
enclosure exibited the same peak when the woofers were
mounted face to face leaving a good sized
cavity. Mounting the drivers in push-pull fashion
reduced the cavity to virtually zero and the peak went
away. As well as the second harmonic distortion.Third
harmonic distortion is reduced by the low pass action
of the slot. Doppler distortion is reduced by the
drivers being at a right angle to the listener. Box
size is reduced by equalized sixth order techniques. I
find a Qts of .312 to be optimum for this purpose. The
slot for 15's limits the HF response to 200 hz. There
is a peak around 800 hz. This is completely determined
by the depth of the slot. There is no increase in
efficency over a regular box. djk

Posted by Jon Risch ( B ) on August 08, 2002 at 20:00:23
In Reply to: Push-pull woofers - how much real distortion reduction happens? posted by freddyi on August 08, 2002 at 12:21:23:

A lot depends on the quality of the drivers, however, even very linear woofers will usually show a 6 dB reduction. It is also more noticable at high drive levels, where the woofers are nearing the suspension limits, and the non-linearities are greater anyway.

Jon Risch (Peavey)


djk
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