AMT sub - using dynamic woofer

[Mike Mount]

Tymphany / LAT700 arrived

I just received my LAT700 woofer, .NOT. exactly sure
how or what I am actually going to use it for...
For 200.00 and change, What the heck???
Very well made device to be sure...
looks promising.

(not sure if I should buy another one...?)
scary hobby... *obsession* this is...

Any thoughts on a N Ripol approximating
ideal cabinet dimensions with this funky
shape. I am going to experiment.

The other matter is horizontal or
vertical positioning of driver?
What would seem best.

 

[sendler]

Ripole advantage

The "mass loading" saga of Ripols is mainly just that.

What looks as to be a down-shift in low cut is *mainly* a illusion caused by the SPL suck out towards higher frequencies.
Or in other words - we sadly do not gain anything - SPL wise. Maybe 1-2 dB at around 20Hz at best.

Ripole might be interesting for all-passive guys though, as it needs less EQing - despite the peak.

For optimization of SPL versus volume sadly its the wrong direction.

Michael

The big advantage of RiPol over H frame is you can cram two drivers into the space that one driver and H frame would take up while also maintaining the biggest dipole distance per cabinet volume of room space used up. The full N frame seems to be your favorite but needs to have the vicious artifact at 160Hz cleaned up. The deep RiPol goes the lowest with the least cut at the top but is also not very flat in it's intended passband. The small RiPol is beautifully flat to 170Hz but won't play as low due to the shorter dipole distance. Maybe something in between the three in terms of pipe length and taper.

 

[mige0]

A single LAT might not be large enough to make too much of difference in directivity either way, assumed, you use it as sub - meaning - whether you use it vertically or horizontally does not matter.
For ideas on how to use it you may get inspiration of Transar speakers - or just cut a biiiig baffle and set it into the middle.

Michael

I just received my LAT700 woofer, .NOT. exactly sure
how or what I am actually going to use it for...
For 200.00 and change, What the heck???
Very well made device to be sure...
looks promising.

(not sure if I should buy another one...?)
scary hobby... *obsession* this is...

Any thoughts on a N Ripol approximating
ideal cabinet dimensions with this funky
shape. I am going to experiment.

The other matter is horizontal or
vertical positioning of driver?
What would seem best.

 

[mige0]

DFD / Deep Frame Dipole sub-woofer

Yes, for any "active guy", the N-shape Deep Frame Dipole offers the best bang for the buck when it comes to SPL capability at (relatively) limited volume.

Listening to this for a few days now, either fullrange / no-EQing solo or with a Beyma 18G40 (also fullrange / no-EQing) in parallel, does not reveal any nastiness - quite in contrary - big instrumentation classical music is already great to listen to.

The wide "space" in the lower - and especially in the bottom end - department is rendered veeeery nicely in my small listening room.


Michael

The big advantage of RiPol over H frame is you can cram two drivers into the space that one driver and H frame would take up while also maintaining the biggest dipole distance per cabinet volume of room space used up. The full N frame seems to be your favorite but needs to have the vicious artifact at 160Hz cleaned up. The deep RiPol goes the lowest with the least cut at the top but is also not very flat in it's intended passband. The small RiPol is beautifully flat to 170Hz but won't play as low due to the shorter dipole distance. Maybe something in between the three in terms of pipe length and taper.

 

[Mike Mount]

Thanks Michael, (and others here)

I am studying/researching all of the possibilities, I want to be clear, that I am not being lazy and trying to have you and others do the foot work for me. More in that there is a wealth of knowledge (here) on a subject that I have only begun to scratch the surface on... I want to draw from the greater body of knowledge, so that as I proceed, I am not stumbling and bumbling about in a relatively new sub concept (to me).

What I think that I beginning to see here, is that multiple small(ish) drivers for speed and finesse and *need* to build a push-pull to have a more linear impedance load to amplifier, due to greater cone excursions, is growing mute with this inherent design.

In other words *properly loaded* BIG A$$ driver(s), 12-15" is better from an air movement and acoustic coupling or mechanical loading standpoint?? Push - Pull becomes less a factor, less important with larger drivers with inherently lower overall excursion.

 

[tb46]

DFD and DFR(?)

Hi mige0,

Interesting subject, a while back I started out designing a Ripole around the Peavey 1801-8 (as I happen to have some), and then decided that this may be something for the MCM 55-2421 if used in multiples. You are adding a whole new twist to the subject.

Where do I find the design details for what you have been listening to: "...Listening to this for a few days...", and what would you think about something along the lines of the attached sketch.

Also, do you have any suggestions on modelling this type of enclosure in Hornresp?

Regards,

 

[mige0]

DFD / Deep Frame Dipole sub-woofer

Push - Pull becomes less a factor, less important with larger drivers with inherently lower overall excursion.

Push pull - at least in theory - lowers even order distortion, which, by some, is seen as a benefit.
In praxis this may be of no big relevance, especially as IMO distortion with Deep Frame Dipoles is *first* not any easy to measure and plots are very questionable, and *second* because the mechanism of distributed drivers along a pipe have special properties - not that well researched yet, and *third* no one (to my knowledge) has done any research in correlating harmonic distortion to perception with pronounced CMP systems.

In other words *properly loaded* BIG A$$ driver(s), 12-15" is better from an air movement and acoustic coupling or mechanical loading standpoint?? .

Regarding what better to use: several small or few big chassis, well actually there is no big difference I can see as long as the sum of displacement volume is the same *plus* dipole separation, arrangement and mouth area is also kept the same.

Also, do you have any suggestions on modeling this type of enclosure in Hornresp?

IMO there is no way to really correctly simulate Deep Frame Dipole speakers right know.

Hornresp does not allow for multiple chassis arranged freely and AJHorn (current version 6) I actually bought for the purpose does allow for arranging two „distributed“ chassis along a pipe of variable shape, *but* does not allow to mirror this arrangement for dipole calculation and also has some IMO severe limitations as sound sources are possibly rather been simulated as to be point sources which does not exactly apply to two 15“ in a 80 cm pipe for example (at least measurements and simus are not *that* close).

With AJHorn one can get at least a rough feeling about changes in pipe shape and some other parameter variations of distributed Drivers in a pipe though.
Also AJHorn has a nice feature in modeling Helmholtz resonators that can freely be placed (within limits) and could be used to "notch" the Ripole peak for example.

and what would you think about something along the lines of the attached sketch.

The attached sketch looks nice – but as said above – I do not think there is anything substantial to gain with respect to less chassis stuffed in.

Where do I find the design details for what you have been listening to: "...Listening to this for a few days...", a

I've been listening to all above variants, no one is any bad.
But as said, out of reasons based on my requirements the N-shaped Deep Frame Dipole got the most attention and most extended listening so far (besides the compact Ripole that I have built some time back).

Michael

 

[soho54]

IMO there is no way to really correctly simulate Deep Frame Dipole speakers right know.

Ack, ma back!

 

[darkmatter]

A friend is about to start a project with up to 8 12" units per side, will look forward to see how they perform.
Will look through the rest of this thread later

 

[belovedbrazil]

Hello, after studying Linkwitz basic dipole equations I understand that the best way to improve the SPL without decreasing the lobe peak is to stack the drivers vertically instead of horizontally (as in figure) so keeping the distance D between the front dipole (polarity +) from rear ( polarity -) the same as used in the compound box. Otherwise , if you use small drivers stacked vertically with the same original area of a larger driver, you will decrease D and increase the lobe peak thus improving the useful frequency range at the same time the SPL.

 

[elac310]

I've been listening to all above variants, no one is any bad.
But as said, out of reasons based on my requirements the N-shaped Deep Frame Dipole got the most attention and most extended listening so far (besides the compact Ripole that I have built some time back).

Michael

Hello Michael,

I also came on the idea to "double" a ripole sub since I need as much SPL as possible. Ended up with designing other dipole shapes due to the difficulty of accommodating 2x21". I came on your posts by doing a Web search for H, W and other designs; I'm very much interested in your deep N-frame dipole and I'm now planning bulding two of these (2+2 21" woofers).

My idea is to place the two N dipoles side by side, but laying down (i.e. the mouths would radiate horizontally as opposed to (your picture in post 7) vertically. Since the deep N-frame is the one you've mostly experimented with, have you by any chance done some comparisons between vertical and horizontal placement of these subs?

Finally, the horizontal placement would allow me to use the two subs side by side as a low table (130 cm x 130 cm).

Chris.

 

[mige0]

My idea is to place the two N dipoles side by side, but laying down (i.e. the mouths would radiate horizontally as opposed to (your picture in post 7) vertically.

Can you post a drawing on how you plan to arrange the n-dipoles?
You know - there is a distinct difference in "just" putting two dipoles close to each other versus to arrange it to as "a deep frame dipole"

Since the deep N-frame is the one you've mostly experimented with, have you by any chance done some comparisons between vertical and horizontal placement of these subs?

Finally, the horizontal placement would allow me to use the two subs side by side as a low table (130 cm x 130 cm).

Chris.

I guess that by "horizontal" you mean that the cone would move up/ down ?
No I haven't experimented that much in this direction, simply because the weight of the cone will force the coil to move off center - which will result in increased distortion.
Over a longer period of time the spider will sink in more and more (remember, its just some fabric after all - not a metal spring)

Hope it helps - have fun !
Michael

 

[elac310]

Next is a Dual-Ripol subwoofer with the chassis arranged one behind the other

Chassis is 2x15” with Fs = 40Hz and Qts = 0.4
(Selenium 15PW5)


This Ripole-subwoofer is roughly 30x40x80cm (WxHxD) which is about the volume of the H-frame subwooofer but housing two chassis instead.


This is how it roughly looks like (top opened):

This is how it measures:
RED Trace: close mouth
BLUE Trace: close mouth measurement “dipole inverse-EQed”
GEEN Trace: dipole comb filter

Michael

I completed my project a couple of days ago and built two subwoofer enclosures.
I have finally opted for this S-shape design, and I'd like to thank Michael for his excellent and inspiring drawings and measurements. I introduced a couple of variations: the two speakers are mounted not 69 but 66-wise (the front faces of the cones see the same tunnel). I have retained from the ripol principle a different load for the back and for the front and finally the two subwoofer enclosures lie "on the side", so that the speakers radiate up-down.

Each sub hosts two PDW21250 (a low cost 21" speaker from Pyle audio) and I built them as compact as possible, i.e. 124,8 cm (length) x 62 cm (width) x 50 cm (higth), using 31mm plywood. On one side the mouth is thus 56x25 cm (loading the back of the woofers), and on the other it is 56x16 cm. The bottom panel can be removed to access the speakers (which "look" at the floor).

I just added these subs to my current system, using active filtering and an additional amplifier. I'm pleased with the preliminary results and the clean bass but it's too early to be too affirmative for the rest. I also need to solve a slight buzz generated by the crossover or wiring.

For the time being, the subwoofers lie side by side in front of the sofa of the main listening position (thus looking like a low square table). In the first setting, the larger mouths were aiming at the sofa then I turned the "table" 90° so that the mouths point to the left and the right. I'll try in due course other positions in the room.

More in due course.

Chris.

 

[elac310]

Subwoofers with dual 21" in ripole mode

Here are a few pics, finally:

[/url] Photo0028 par elac310, sur Flickr[/IMG]

[/url] Photo0030 par elac310, sur Flickr[/IMG]


Photo0031 par elac310, sur Flickr

and a schematic (sorry, comments are in French but you get the "picture" of the structure):

[/url] Numériser 1 par elac310, sur Flickr[/IMG]

 

[siruis815]

Those frames and magnets look much like the MCM 21" Cast Frame drivers that I'm using in my OB setup. The build looks absolutely huge! I'll be following for your listening impressions.

 

[elac310]

Those frames and magnets look much like the MCM 21" Cast Frame drivers that I'm using in my OB setup. The build looks absolutely huge! I'll be following for your listening impressions.

Ca you post a link to this MCM brand/woofer ? never heard of them.
Probably some other OEM production by the same manufacturer.

Don't be fooled by the pictures: yes the double magnets are quite large but the basket is stamped steel (no molded massive aluminium) even for those apparently large basked branches. Nonetheless, bulding was OK on this batch, no inverted connections, no decentered / rattling voice coil, clean gluing of surrounding and dustcap etc. On one woofer, the double magnets are not 100% perfectly aligned but we're talking of something like half a milimeter here.

The ripoles hold their promises. Extremely tight bass, nothing comparable with most bass reflex or closed boxes I've heard so far. Maybe I would dare a comparison with a (good) bass horn... But to go that far down with horns, they'd need to be extra-large size, I guess. There is also some inertia with those heavy cones and they need a few volts to become alive. Not too much of an issue in multiamping mode, of course.

Sensitivity is on the low side, compared to the rest of my system, at least.

Overall, very pleased with the "experiment". My conclusion: there isn't much below 50Hz on the majority of commercial records, but several well recorded ones do have life at those depths too, though.

 

[siruis815]

Here's the MCM: MCM Audio Select 21'' Die Cast Professional Woofer - 800W RMS | 55-2985 (552985) | MCM Audio Select
vs
the Pyle: Pyle Performance Optimized 21'' Pro Audio Die Cast Woofer | PDW21250 | Pyle

My sensitivity is low as well - but then again we are doing OB woofers. I'm currently using a 50Hz Lowpass as my "EQ", yielding pretty good results.

 

[elac310]

Here's the MCM: MCM Audio Select 21'' Die Cast Professional Woofer - 800W RMS | 55-2985 (552985) | MCM Audio Select

Thanks ! Another nice baby !
Have you done your own T/S measurements or have you heard anything about the trustworthyness of those published by the manufacturer?

My subs are managed for the time being (until I find a suitable equivalent pro-tool) via a little cheap thingy called Reckhorn S1. Xover ist at 45-50Hz (the pots are not very precise), no subsonic limit applied and I give some extra boost/equ at around 25 Hz or so.

 

[siruis815]

I have not done T/S measurements - but I have heard that the ones posted are not very accurate. Being that I went with the OB route (24x48" panel) the specs didn't quite matter as much - especially just applying a line level filter. Future investments in things such as the minidsp are planned. I'm not running subsonic filters either unless I want to go deaf - then I'll apply a 40Hz xover to the 2 12" subwoofers ported to ~20Hz.

 

[weltersys]

Overall, very pleased with the "experiment". My conclusion: there isn't much below 50Hz on the majority of commercial records, but several well recorded ones do have life at those depths too, though.

Most pop stuff is aimed at making maximum boom, pretty easy to do 50-100Hz.

Try "Raising Sand" by Robert Plant & Alison Krauss.
Many of the cuts have as much peak level at 25 Hz as at 50 Hz.
Sounds really big even at moderate level with speakers flat to 20 Hz.