Eminence Beta 12LTA on Open Baffle

Eminence Beta 12LTA on open baffle

This is my favorite ‘full range’ speaker even tho it’s not really full range. It gets nearly everything right – but you must modify it in order to smooth out its roughness and add a super tweeter to extend its high frequencies. It can be used in sealed, ported or open baffle type cabinets. I’ve even read about a monster sized BIB back horn that lives somewhere. I use the 12LTA on an open baffle. In addition, a helper woofer in the form of a powered H-frame, provides bass.

The Eminence Beta 12LTA frequency response extends high enough into the treble that adding a super tweeter seamlessly is easy. I’ve tried the old Radio Shack pod super tweeters with good results. I’ve also tried the Eminence ASD 1001 with better results.

Modifying the 12LTA is easy. Just remove the dustcap. Once removed the sonic character of the driver smoothes out noticeably. Further smoothing results when fitting the driver with a phase plug. A pair of phase plugs was donated to me by JRKO. Thanks, they are awesome! The sonic difference between adding the phase plug and not was minimal to my ears even tho the charts below indicate improved performance. Simply removing the dusctap is all that’s required to eliminate a slight cupped quality.


Eminence Beta 12LTA measurements with and without dustcap.

Link to original thread at diyaudio.com:


Immediately, I was smitten by this driver. I’m a full range driver fanatic. I love the coherence a speaker without a crossover can provide, but the 12LTA also has dynamic power none of the drivers in my collection exhibit. This dynamic power is expressed as an easy confidence. From the most delicate violin to the most complex orchestral swings, the 12LTA handles everything with aplomb. Even Rock & Roll sounds great, something most full rangers can’t claim.

Having experimented with several full range drivers on open baffle it was just a matter of time before trying the 12LTA. Interestingly, in my system, any driver from 3″ all the way up to 12″ uses the same form factor – a simple 19″ x 19″ baffle sitting on top of an H-frame.

The tweeter simply utilizes a 1.33uf capacitor as its crossover, nothing else is needed. Treble is only as good as the supporting tweeter – but it must be efficient! Pro Sound compression tweeters are a good match for the 12LTA and since this application uses just the tippy top octaves of what the tweeter produces the harshness is eliminated. I was pleasantly surprised to hear how nice Pro Sound tweeters sounded when implemented this way. It’s a tricky thing finding the right capacitor to use with a tweeter in any application. Even tho I settled on 1.33 for the ADS 1001 tweaking the treble up a notch on the Spotify EQ brightened things up nicely without introducing any additional sibilance or other unwanted artifacts. In other words, I liked how the speaker sounded when I raised the treble.

The Eminence Beta 12LTA is rated at 97db per watt. This is the most efficient driver I have. It’s clearly more efficient than the Fostex 168z and Tangband 1808 which are rated at 94db and 93db respectively. The 12LTA bristles to life with just a few watts and sings beautifully with low powered tube or digital amps. It even rocks with solid state! If you’re seeking high efficiency, this driver is tough to beat – and that includes Lowther, among other pricy full rangers.

The driver’s balance is warm and full thru the midrange. Critically, I’d say male vocals are nearly perfectly reproduced while female vocals are slightly less realistically rendered. This is where blending the tweeter is critical or Norah Jones and Diana Krall will sound slightly cupped. But this is an easy fix given some patience integrating the tweeter. I’d recommend experimenting with capacitor values between .47uf and 2uf. I started with 2uf (which was too bright) and worked my way down to .47uf (which was too dull). The tweeter you select will determine the best capacitor values.

Once you have dialed in your tweeter to taste the 12LTA is incredibly musical. On open baffle, imaging is superb. Instruments pop like nothing I’ve heard before. Musicians occupy their own space and the image produced is very broad and deep. I understand this is contrary to typical audiophile theory that smaller drivers and slimmer cabinets have superior imaging but this is not what I hear. A handful of better drivers produce ghostlike imaging some of the time but none as consistent as the 12LTA. Additionally, crescendos swell like nothing I’ve heard before. In my home, there seems to be more than sufficient headroom – these speakers play very loud!

The superior imaging can also be attributed to the driver being on an open baffle. Personally, I feel open baffle produces the most realistic imaging. But this is a preference not everyone shares.

I love music and can enjoy long listening sessions with many full range drivers I own. Having recently been thru an enjoyable experiment where 3″ drivers were the norm, I’ve gone much larger with the 12LTA and feel I’ve lost none of the excellent qualities of the smaller drivers (as long as I can include a helper tweeter). In fact, perhaps the addition of a tweeter improves treble further. If you are looking to ‘go big’ and can get your head around the idea that a large diameter woofer can perform as well – or better – than smaller drivers then I can’t recommend the Eminence Beta 12LTA enough. With some elbow grease (removing dustcap and integrating a tweeter), I believe you come out on top of nearly all full range drivers on the market today. What you end up with is a speaker that does it all without compromise. Whether it’s Classical, Rock, Folk, Girl & Guitar or Techno Synth, this speaker provides sound with incredible ease of presentation, scale and realism.

The large, wide range, Eminence Beta 12LTA is a purpose built Pro Sound driver. It was designed by engineers and contains no black magic or pixie dust. It looks big and perhaps is a bit ugly. But what it may lack in looks it gains in performance. It’s large 12″ paper cone opens a window into the venue transferring the sound from your amp into music unlike most drivers you’ve already heard. It’s not picky about amplifiers either – which is uncommon since most full range drivers are. For me it achieves among the best sound I have heard in over three decades of DIY speaker building. As long as I can incorporate a helper woofer and tweeter, this would be my desert island driver.



26 thoughts on “Eminence Beta 12LTA on Open Baffle

  1. Hi Zilla – I’ve tried to source the ASD 1001 and am just coming up with a compression driver and not a driver/horn combo. What would you suggest using? Thanks!


  2. Hi, Zilla, having trouble finding a 1.33 UF capacitor. Would you recommend a 1.0 and a .33 or can you recommend a source for a 1.33? I am planning on using the Pyramid TW44 bullet tweeters, but will eventually go with the Eminence 1001 and the Dayton wave guide. Any suggestions would be greatly appreciate. Thanks. pbruney@bellsouth.net


    • Yes, a 1uf plus .33uf will do the trick. I have not heard the Pyramid bullet tweeters but wonder how they sound? Let me know if you feel the need to try the Eminence 1001 and Dayton waveguide. I’m not suggesting you must. Good luck and enjoy!


    • I removed the dust cap with an Xacto knife. I put the 12LTA on a table that allowed it to spin on its magnet. I carefully placed the knife in position and slowly spun the driver. It’s a slow process that takes about 5 to 10 minutes. Make sure the knife is sharp and don’t forget to turn the driver upside down once the dust cap is removed so debris doesn’t get into the inside of the driver.


  3. I I’m thinking of building an open baffle speaker system using the Eminence 12Lta and the ASd1001 tweeter, is the woofer running through a crossover from Eminence 12Lta, or powered separately. the amp I will be using is a leak stereo 20 via a quad 33 Pre,


    • Hi Tony! The Eminence 12LTA is running full without a crossover. Some like to use a crossover to reduce bass going to the driver. I do not think this is necessary in my room (approximately 12×25 feet) because things get pretty loud and I do not think I am taxing the driver at all. The tweeter IS connected to a crossover – simply a capacitor. Try values ranging from .5uf thru 2uf. I think mine is 1.5uf. Try different values to find what sound you like best. In addition, I think the 12LTA needs bass support to sound its best. I do not think an H-frame is the only way to make bass, sealed and ported subwoofers will also work… but I do prefer open baffle bass.


      • Jefffeith thanks for your reply, My System at present comprises STD 305 turntable, Triplanner MKv11 tonearm and coral MC81 cartridge, amps are Quad 33 with mods from net audio + a leak stereo 20 refurbished, speakers are Quad 57’s refurbished by one thing audio, Cd player Marantz 52se MK11. listening room is 25ft x 14ft. The reason for building an open baffle is quiet simple my wife hates the sight of the quad 57’s. I’m willing to sacrifice a small amount of bass, as the 57’s bass is limited but midrange and treble detail from the 57’s is expansive and very detailed, would the eminence beta 12lta and ASD 100, give a comparable sound to the Quad’s. Blues, jazz and light rock are my musical preferences. I would add a helper woofer at a later date.


      • Gillingham57, I have not compared them directly but imagine they sound very different. Having said that they both sound very good. The problem of using the 12lta alone without bass support is that it won’t reach much below 200Hz on open baffle. In my opinion the 12lta on OB requires bass support to sound enjoyable. Sorry your wife doesn’t like the Quads. Your system must sound nice.


  4. What about using the Eminence Beta CX 12 with the ASD1001S or APT50 HF driver? This is supposed to be a full range coaxial driver. I am very interested to use this instead, what do you think?


    • I have always been intrigued by the Eminence Beta CX12 coax. I’m sure it will work fine BUT I prefer the ability to select a waveguide based on listening impressions. I like being able to swap different options. With the Beta CX12 you are limited to the shape of its cone and stuck with its sound. Of course you can still shape the sound of the compression driver to taste with crossover components and work to tailor the sound – so you still have options. Personally, I am not sure the use of the drivers ‘waveguide’ will allow a tweeter to cross low enough (around 1600kHz) to the main 12” driver. You may be looking at a less than ideal crossover point of 2kHz or higher. Maybe it sounds great that way. Please let me know what you decide to do.


  5. Hi Jeff,
    Try using a 4″ mini foam paint roller as a phase plug and let me know what you think. You have to pull the little roller out of the end first, but that’s a piece of cake. I used this setup on a different FR driver , and used a socket head cap screw (allen key) inside the end of the paint roller. If you used a washer and a socket head cap screw it would hold it in place magnetically and center it in the pole piece vent.

    I used to talk to you on the FullRange Driver Forum before it went the way of the dinosaur. I was Admin after James lost interest.




    • Hi Blake, great to hear from you! I still enjoy full range drivers and love the old style Fostex 168s with whizzer in a big ported box. It’s not my main speaker anymore but it certainly did put me on a path to even better sound. Truth is, I can live with this simple setup but experimenting with different drivers keeps me out of trouble.


    • Hi Qi! The 12lta sounds better to me with the dustcaps cut out but that doesn’t mean they sound bad leaving them on. If you are uncomfortable removing them I suggest leaving the driver as is and enjoying them that way.


  6. I’m thinking of making an ob and h-frame based in your design using the beta 12lta and asd1001. How did you wire up your speakers? Did you use an Eminince 15a in your H-frame? Thanks for your reply!!



    • I use the Alpha 15 in the H-frames running off a subwoofer amp. This way I can vary the crossover and volume. The 12LTA runs without any filters. The crossover on the tweeter is simply a cap.


  7. Hi Jeff:

    Finally – at age 64 I have my own dedicated listening room, and can build a large speaker system to my liking – no WAF to be concerned with! I’m planning to make an bi-amped OB/H-frame combo like you have done. I’ve got a pair of Visaton B200’s – but hesitate to use them because of the infamous, sizzling hot top end that I’ve read so much about.

    Then I saw this 12lta setup! I really like the fact that I can adjust the tweeter level to my liking, AND…the super high efficiency will allow me to finally get some slam out of my 2.5W, 2A3 SE amps!

    Three questions:

    1) How would you compare the sound of the B200 vs the 12lta? It seems you prefer the latter?

    2) What kind of low end extension were you getting from the 12″ Eminence Alpha in MJK’s H-frame? Is it solid down to 30 Hz or so?

    3) What did you use for a phase plug in the 12LTA? Does Planet 10 (or others) supply them, or do you have a great and cheap DIY method to make them?

    Many thanks for sharing your designs and experiences with all of us!

    Papi Chulo
    Prescott, Arizona


    • Papi, that’s so great about your dedicated listening room! Enjoy! Unfortunately I never had the pleasure of hearing the B200 (I never bought it because of the comments you described – sizzling top end). But at my age, just shy of 53, a bit of extra top end isn’t objectionable. Perhaps you feel the same? The H-frame measures down to about 35Hz but I’m using a 15” Alpha 15, not a 12” woofer (unless you made a typo). As for the phase plugs, someone generously gave them to me as a gift. I’d imagine Planet 10 has them for sale. Personally, simply (and carefully) removing the dust cap from the 12LTA improves the sound by minimizing the slight cupping quality on vocals. The phase plug smooths things out further.

      Having said all this I’d recommend you build the H-frame (if you are set on it) and separate baffles for the B200 first and listen for a while. If over time you feel the B200 is not performing as you hope then begin the process of building new baffles for the 12LTA. it should have no trouble playing loudly with your low powered tube amp – which is why I built this speaker to begin with.

      And another driver option to consider at 98db per watt is the Eminence Lil’ Buddy – but it requires a horn tweeter, waveguide and crossover at 1.6kHz. No alteration to the driver is necessary and you can use it with the H-frames. If interested, I’d be happy to discuss this with you offline.


      • Thanks, Jeff!

        Yes, it was a typo on the 12″ Alpha, I meant 15″. Does your Alpha bass measure solid at 35, or is it already a6 or 10 dB down by that point?

        My dedicated room is rather small (11′ x 12′ x 10′ ceiling), so getting the speakers out of the corners is a bit of a challenge. I noticed you have recently switched over to a U-frame sub, which is only half the depth of the H-frame, and MJK sims show only 3 or 4 Hz less low end extension for the “U.” That might be the ticket for me, which automatically provides an extra 7″ or 8″ of clearance from the back wall…if that matters at all. What do you think?

        I’m actually considering the Goldwood 18″ U-frame, which is just a few inches wider than the 15″ Alpha version, and I know that it will DEFINITELY go so low that I’ll never want for solid organ bass pipes again! Might the 18″ just be too darn much for the room I have? Your opinion, please?

        OB is certainly a new horizon for me. I had Magnepan SMGs as a youth, and I loved that “big” and “open” sound a flat panel gave me. I’m hoping that the OB project gives me a similar big soundstage as the Maggies once did. I’m really tired of the “box” sound, although simple boxes can be rather good with a FR driver.

        I do have a number of FR drivers I can try in the OB in addition to the B200: Fostex 126e, FE103en. Radio Shack 40-1197s, 40-1354’s. Mucho fun ahead!

        Thanks again!


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