which driver for subwoofer

Posted In: Subwoofers 101

  • Member
    PeteS on #1005

    I’m new to this forum and have just discovered Lambda drivers.
    I have an active system and am looking for 15 inch drivers for stereo subs in 160 litre sealed boxes. The ones I have been looking at are the td15’s, but I don’t know which one so I can’t seem to work out which of these drivers would suit best.
    I would like it to reach down to <20hz if possible.
    I would guess that using these drivers I would be able to comfortably cross at about 400hz?
    Any help would be appreciated.

    simon5 on #10049

    You could go with the TD15 line, either the S or the X, you can also take a look at the SBP15.

    It depends what Q you are after… will you use polyfill ? Will you use EQ ?

    PeteS on #10050

    thanks for the response.
    I have been offered a pair of TD15m Apollo but I can’t get any details. I believe these ones are a variation meant for a 200 litre sealed active enclosure.
    I run an active system and use a DEQX to EQ.
    The boxes are lined with car deadening sheet and I can put polyfil in if required.
    I am a little out of my depth with all this, so any help would be appreciated.
    I have just found your IB15 in your site but can’t seem to find out anything about them, or their price.
    They seem to be just the ticket.
    Regards and thanks,

    moody on #10051

    This is something John wrote on avs-forum some time ago which I find very informative:

    The TD15M’s are the midrange-midbass models. Four layer flatwire aluminum coil, high efficiency, accordion cloth surround. Bl^2/Re of 43.78 with mms of only 70g. As a result the efficiency is quite high at 97.8dB 1w/1m. Any time you can have less power input to reach the same SPL is ideal. Lower power means less thermal issues, less flux modulation, etc. Again, efficiency is GOOD. If you’re using a separate subwoofer chances are the TDM is going to be your best bet.

    The TD15S uses a 2 layer roundwire copper coil and the foam surround. Bl^2/Re of 37.5, mms of 108g and 1w/1m of 93.4dB. This has the least mass and the lowest motor strength gives it the highest Q. The higher Q makes it the typical choice in a sealed enclosure to get the highest F3 point.

    The TD15X uses a 4 layer flatwire aluminum coil and the foam surround. Bl^2/Re of 49.6, mms of 105g and 1w/1m of 94.8dB. It is essentially the higher excursion option to the TD15M for midbass use.

    The TD15H uses a 4 layer flatwire copper coil and the foam surround. Bl^2/Re of 62.2, mms of 129g and 1w/1m 94dB. The most mass and most motor strength makes it the best option for ported/PR woofer/subwoofer use. The more mass and motor strength can also be a good option for sealed subwoofer use with added EQ. The higher the mass and motor strength, typically the smaller the cabinet requirements.

    Between the S, X, and H the cone/surround/spider assembly is all the same. As a result any physical characteristics such as surround resonance, etc are quite similar. The idea is just to give different options for the amount of mass and motor strength to best fit the application. They feature the same motor with the low and linear inductance. Info on the motor design is here:


    I hope that helps enough and doesn’t further confuse people on the differences.


    PeteS on #10052

    Thanks for your reply Moody.
    Does that mean that the TD15M is unsuitable for sub use?
    I normally run my subs under 100Hz but thought that if these drivers are as good as they seem, I could go higher.
    I take it that the main reason that the TD15H is more suitable is that it has a heavier cone?
    The only confusion for me is that the drivers I have been offered have apparently been made to have a 90db efficiency and meant for a 200 litre box:?
    Would this mean that they have heavier cones or would something else have to have been changed?

    moody on #10053

    Hi Pete,

    the TD15M has cloth surround and only 6mm Xmax so it would be the least suited for subwoofer duty
    in the TD lineup. I would agree with John that the TD15H is the best driver for a subwoofer, but then
    again there is better drivers for the job. AE’s AV15X is the most suited driver for the job, but currently
    unavailable. I have no chance of modeling it right now, but I guess the SBP15 could work really good too.

    simon5 on #10054

    @petes wrote:

    I have been offered a pair of TD15m Apollo but I can’t get any details. I believe these ones are a variation meant for a 200 litre sealed active enclosure.

    As moody said, you will need to double check that. Those are not TD15M specs.

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