Recommendation for high efficiency midrange for open baffle

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i am starting a new open baffle  project and am looking for an open baffle midrange with high efficiency that can cover
500-2000hz . i am considering running them naked AKA no baffle, possibly in a MTM configuration, so two midrange drivers would be used.

candidates i have researched so far are :

Audax PR170MO
great reputation , amazing efficiency , but ridiculous 0.5mm driver exursion (???)

looks good , 96db efficiency, 2mm xmax

B&C 6MD38, 96db , 2mm xmax

18sound 6ND430  92.5db , 2mm xmax

Acoustic Elegance TD6 Dipole 91db , 3mm xmax .

these are all 6.5" drivers as i think that size would suit the OB best , considring 1st dipole peak .
smaller driver is also possible .

below i will fill in with two Acoustic Elegance TD15LO which play from 80 to 500hz but could go higher .the low bottom is covered by a boxed sub.
tweeter is Beyma TPL150 , at this time just with the open back , but i plan to either build a dipole horn/waveguide for it, or to purchase one that will shortly be available.

crossovers and correction will be done by a DEQX so high slopes and EQ is not a problem.

any experience and/or comparison and opinion about the mentioned drivers or others that fit the requirement is much appreciated .



  • Full Member
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  • The elephant normally IS the room
How about Lowthers?  Once you shed the bass/treble loads from them, you'll find an exceptional extended midrange driver.  And with your EQ, any 1100 Hz "forwardness" can be tamed.


any particular lowther you would recommend ?
would you cut the whizzer ? not that i feel comfortable doing it but it seems to be the thing to do if its " in the way " and not useful in the approached application.


  • Jr. Member
  • Posts: 145
you needn't care about xmax of a high efficiency midrange for domestic use.


I'd opt for the TD6M's myself (not the dipoles as I don't think that is really needed here, but I could be wrong). 

Lowthers could work, but would be terribly expensive, especially for only two octaves that the OP wishes to cover.  I am not convinced that they would do any better for this range than other solutions.

I might also push the lower xo point for the mid down to 250-300hz for a variety of reasons but you have a decent overlap to play around with.  But then again due to no baffle the mids will likely roll off fast, so you might need to use the 15s up higher.


yeah, the Lowthers would be terribly expensive , i agree.

Josh , could you elaborate why you would opt for the AE TD6M instead of the Dipole ?

the TD6M is 3db more efficient compared to the Dipole version, but oterwise i would think the Dipole is more suited for OB application (?)


well I don't have the data all in front of me, but sensitivity is nice here.  But there is more going on, so in the end, it might not matter, but my guess still would be to try (model first before by). 

The thing is, as I understand it, the dipole mid has a higher Q so that it rolls off slower, boosting the lower end its bandwidth, but you are not calling on the mid to do much low end, so it might not be very helpful.  That was my basic thinking.  But without a baffle and depending on how low you end up going, there can be other factors that may weigh back in favor of the dipole mid.  Tough to say without modeling.


I'm using the B&C 6PEV13. For crossing at 500 Hz you don't really need a lot of Xmax, 0.6mm at 500 Hz is a nominal 114dB@1m. The issues (I think) are more to do with dispersion (rear as well as front). I'll have some measurements on mine in a couple of weeks hopefully. Less of an issue with a 2k LPF than the 4k I am using though.


here are the specs of the TD6 and TD6 Dipole:

TD6M-8 :

T/S Parameters

Fs: 83hz
Qms: 3.1
Vas: 10.3L
Cms: .45mm/N
Mms: 8.2 g
Rms: 1.38kg/s
Xmax: 3.3mm
xmech: 7mm
Sd: 127 sqcm
Qes: .46
Re: 6.1ohm
Le: .044mH
Z: 8ohm
Bl: 7.5 Tm
Pe: 100W
Qts: .4
qW SPL: 93.5dB
2.83V: 94.5dB


Fs: 79hz
Qms: 11.7
Vas: 10.3L
Cms: .45mm/N
Mms: 9g
Rms: .38
Xmax: 3mm(one way)
Xmech: 8mm
Sd: 127sqcm
Qes: .78
Re: 6ohm
Le: .086mH
Z: 8ohm
Bl: 5.9Tm
Pe: 50w
Qts: .72
1WSPL: 90.2dB
2.83V: 91.4dB

« Last Edit: 12 Jan 2011, 12:00 am by hum4god »

Danny Richie

  • Industry Contributor
  • Posts: 11985
Whatever you do try to find a driver (or drivers) that will allow you to play as low as 200Hz in the open baffle. 300Hz to 500Hz is the heart of the mid-range and crossing in that range to dissimilar drivers and adding possible phase shifts in that area will really cause problems that are easy to avoid with the lower crossover point.


Re: Recommendation for high efficiency midrange for open baffle
« Reply #10 on: 11 Jan 2011, 11:51 pm »
He's using a DEQX, so "phase shifts in that area" are not an issue.