Dipole 18 – Anyone used them?

Posted In: Lambda Drivers


  • Member
    sveinungm on #945

    Hello,

    Have anyone here used the (quite) new dipole 18 yet? And maybe also compared it to other drivers in OB? I cannot find much about this driver on the web. OB bass is tempting, but not sure what drivers to choose. Want to have the best driver possible. The td18h+ is also interesting for OB. It need some EQ in the low end, but have a strong magnet/motor and may be “faster” than the dipole18?


    Member
    simon5 on #9315

    AFAIK it’s the same magnet and motor assembly, but the coil is different.

    If you want OB, Dipole18 is the better choice.


    Member
    sveinungm on #9316

    Okay, but are you sure the magnet and motor assembly the same? On the pictures, the magnet of the td18h+ looks larger. It also have a lot higher SPL and around 1/3 of the Le of the dipole18. I am also wondering about the high Le of the dipole18. Is it correct? In the text about the dipole18 AE state that it has extremely low inductans, but in the specs it is 1,4mh? The dipole15 have only 0,15mh. Is the high Le on the dipole18 correct?


    Member
    simon5 on #9317

    Well the coil is much longer because instead of an overhung design like the TD18H+, this is an underhung design. That mean Le is higher.

    The Fs is quite lower and it has a stiffer suspension, which means lower SPL versus TD18H+.

    You can’t compare with Dipole15, which has a 2″ coil instead of the 2.5″ of the 18″ line.

    It’s also possible that by design John made the magnet stack a bit weaker on the Dipole18 to achieve better results once on a baffle, as you said.

    TD18H+ is a very good woofer but it will need much more electronic compensation in the bass range to equal what a Dipole18 can do naturally, once in an OB role.


    Member
    sveinungm on #9318

    Yes, I know the underhung/overhung differneces and 2″ vs 2,5″ from 15 to 18 inch. But, still I think the Le is very high on the dipole18 compared to the other AE drivers.

    TD15M(overhung): 0,2mh
    TD15S/X: 0,3mh
    Dipole15(underhung): 0,15mh
    TD18H+: 0,41mh
    Dipole18: 1,4mh

    As we see on the 15 inch drivers the Le is lower at the dipole/underhung driver than on the normal TD line. It is the same on the 10 and 12 inch drivers also. On the 18 inch drivers the Le is about 3 times higher on the underhung design(dipole18) than on the overhung design(TD18H+). I cannot see why it is like this. I also cannot understand how AE can write “extremely low inductance” when the inductance is 1,4mh(if it is correct?).


    Member
    simon5 on #9319

    I will try to ask John about this, I’ll try to reach him, he will be able to answer better or to correct the value if it’s not the right one. 8)


    Member
    simon5 on #9320

    I just briefly talked to John.

    He told me he believe he wired the coils in series when he took his Le measurement, in series instead of in parallel.

    So, 1.4 mH in series for 32 ohms, or 0.7 mH per coil for 16 ohms, or in parallel like it should have been, 0.35 mH.

    That would fall in line with your theory, since 0.35 mH is lower Le than a TD18H+ at the same impedance level… 8)


    Member
    sveinungm on #9321

    That makes more sense! 😛 Thank you for checking it out.


    Member
    sveinungm on #9322

    But isn’t it anyone here who have used the dipole18 yet? Some impressions of it had been very appreciated 🙂


    Member
    tuyen on #9323

    The dipole18 / ob18 driver not very popular it seems?

    Is the price the main reason for this? Or are the fact that the 15″ variant is just a better (ie. faster/detailed/cleaner/etc.) driver for most home DIY systems?

    I am after really fast and resolute OB bass that will play upto 300hz for my home DIY horn setup. I have a deal from a friend who has 2 pairs do AE 18 OB drivers that he purchased recently, but due to change in direction, is offering me at a substantially lowered price. But that price is still more than double I can buy 2pairs of the 15″ models…

    Which one should I get?!


    Member
    tuyen on #9324

    Can I also ask why the Dipole 18 or OB 18 models are not shown on the website anymore? Yet, they are still being produced upon request?

    Cheers,
    Tuyen


    Participant
    stryke on #9325

    We have actually been selling quite a few of the Dipole18’s. I have a lot of them in production that are going over to China soon in an order I have been trying to finish forever it seems. There are a couple sets just finished up this week that are shipping out hopefully next week to others in the US as well.

    The main reason for not selling even more is they aren’t on the website. Our online store is down due to an “upgrade” from Bluehost. They hadn’t made it to the main website for lack of time. We have’t had an OB18 at all. We just developed an IB18 but have only sold a few of them to this point.

    Here are a couple designs using the Dipole18..

    http://www.diyaudio.com/forums/full-range/185777-ok-so-i-want-build-my-first-open-baffle-full-range-7.html#post2525818

    http://www.tubebbs.com/viewthread.php?tid=165721&extra=&page=29

    Up to 300hz, it is mostly about displacement. The Dipole18’s are clean up to 2KHz, so 300hz is no problem.

    best regards,
    John


    Member
    tuyen on #9326

    Thanks John!

    Guess I will go ahead with the deal for the 2 pairs of Dipole 18s then.

    Now I’m trying to understand this issue with ‘baffle rolloff’ and how to compensate. What baffle size I should be looking at. Here was I, thinking it was as simple as just mounting the 2 drivers in a baffle and use an inductor to roll off at 300hz and I will get an awesome bass solution for my system. As I read more into it, I’m finding out I may need to use DSP of some sort to fix the baffle roll off?! Not possible to do with passive components? I plan to bi-amp my setup, big power amp for the Dipole 18s and a small valve amp (with attenuator to lower the gain to match the bass) for the upper horn channels.

    Any advice?

    With thanks,
    Tuyen


    Participant
    stryke on #9327

    Yes you will want DSP to correct for this or you bring down efficiency of the whole system. Response will be very dependent on the baffle size and placement of drivers. On an 18″ wide baffle you will see about a 15dB drop from 200hz to 30hz. To account for this passively will mean your whole system is very inefficient. Doing it actively with DSP retains the higher sensitivity of the drivers and power isn’t wasted in the passive xover.

    http://aespeakers.com/pics/OB15_vs_Augie15-dipole_baffle_effect.png

    The best option is to build and measure the response on the actual baffle. You can get a good general idea using Tolvan’s The Edge Baffle Simulator. This can also calculate components to make an active circuit to compensate for the baffle rolloff.

    http://www.tolvan.com/index.php?page=/edge/edge.php


    Member
    tuyen on #9328

    Hi John,

    Thanks for your reply. My requirements have changed now. I am only needing <200hz from the dipole18s. Will have a 8" field coil driver above hanging from the roof above on a 160hz azurahorn. I prefer not to loose efficiency from the dipoles, so maybe something like the H-frame baffle is my best option? Do you have any suitable baffle designs that you have modelled up that I can follow and build? Basically I am looking to find whatever baffle is most suit for a pair of dipole18 drivers for each channel that is to play a flat as possible 200hz and under.

    On DIYA forums, some guy recommended to run one of the dipoles upto 200(or 300hz) and the other one to run from 80hz and under?

    Cheers,
    Tuyen

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