Eminence Beta 12LTA Enclosure

[ebag4]

I am looking for an enclosure for the Eminence Beta 12LTA that will offer bass into the low 40s or better. I have a width limitation and would prefer it to be less than 24" deep, however it can be tall but must easily fit into a room with 8' ceilings.

I have looked at the EmKen, but without major redesign will be too wide. The BIBBB is intriguing but considerably too large. I have read that it should work nicely in a TQWP but can't find any real info on this driver in this alignment. That leaves me with BR or Sealed. I believe I would go with the BR in this case for the additional bass. I am considering a 5 cuft BR with internal dimensions of 10"x18"x48", I would likely build some type of pod for the driver to actually mount to allowing the driver a bit more room to breath. I don't know what size the vent would be as of yet.

I am open to recommendations, the width is the most critical value and needs to be no more than 13" wide.

Any recommendations for freeware to develop the box and vent sizes would be appreciated as well.

Thanks,
Ed

[GM]

Hmm, you left out the 'kids' part which normally calls for a prosound alignment like is typical for live venues where bass reproduction is more perceived than real and to get even more acoustical protection, make it a relatively tall MLTL. You'll need a TL/horn designer for these. Basically, you use an acoustically small cab tuned too low to increasingly damp the driver with increasing SPL down low. Think sealed except with more usable gain BW.

For a BR version, these can be simmed in any vented program once you know what values to use. For sure, 5 ft^3 is much too large as this type of alignment can’t exceed Vas and normally needs to be somewhat less, though by how much has apparently been open to debate since 1930 when A.L. Thuras applied for the first ‘bass reflex’ patent [at least here in the USA].

I haven't done a program comparison per se, but for single vents, MJK's TL/horn MathCad software is the most accurate I've used and only $25 IIRC.

WinISD Pro is often used, though like most of these programs it assumes a true Helmholtz situation, so tend to make the vent too long [lower tuned], which in the scheme of things is normally better than too short and rarely changes tuning enough to be obviously audible higher up in the mid-bass.

Unibox was popular at one time, but haven’t noticed any references in quite some time now. Ditto Jeff Bagby’s software.

Lately, some folks have been using HornResp, though it has no ability to sim any added damping, so one needs a bit of experience to decipher what it’s likely to be once damped, especially with [ML] TLs.

GM

[ebag4]

Thanks for the response GM.

I mentioned 5 cuft because in my reading I found where Godzilla had mentioned that that was the volume where the bass started to kick in for this driver. I have now downloaded WinISD and the smallest vented box it came up with was ~5.5 cuft and some of the recommended boxes were in excess of 11cuft and were outputting down into the 20s.

I did some more searching for a TQWP/T and was not able to find much more info.

Best,
Ed

[GM]

You’re welcome!

Yes, I normally recommend the largest practical cab in the hope that folks will at least make the largest they can accommodate to allow some extra bass/in room tuning flexibility. After all ‘BIB’ rules when it comes to making effortless bass, but you said earlier that it would be for kids along with the need for a small cab, hence my suggestion.

I’m surprised, I’ve posted enough to fill a small book and there’s others that’s done likewise, with MJK having a whole website with custom design software devoted to them: Quarter Wavelength Loudspeaker Design

WRT a minimum cab net Vb, the original ‘ideal’ was whatever raised the driver’s Fs 1.56x in a sealed cab [~3.34 ft^3 using published specs], then tuned to Fs if vented. The vent would then be critically damped to remove any obvious ‘ringing’ and/or ‘boom’. This tuning is desirable for a high output impedance system to maximize bass gain BW, but with today’s vanishingly low output impedance amps, tuning it to whatever a T/S max flat alignment calculates is normally a better choice overall [~36 Hz using published specs].

GM

[ebag4]

Originally Posted by GM

You’re welcome!
I’m surprised, I’ve posted enough to fill a small book and there’s others that’s done likewise, with MJK having a whole website with custom design software devoted to them: Quarter Wavelength Loudspeaker Design

What I should have said was that I haven't found any info regarding the use of the Beta 12LTA in a TQWT, I found quite a bit of info on the alignment itself.

Regarding the size of the cabinet, I can go fairly large from a volume standpoint because I can go vertical, the width is the primary measurement that is limited, the depth can be up to 2' but I would prefer it to stay somewhat under that.

Best,
Ed

[wintermute]

I still use Unibox!! I have always much preferred it over winisd. It does require you to have microsoft excell though.

If you really want to get your teeth into something (simulation wise) you could have a look at AkAbak but be warned it has a very steep learning curve!

Tony.

[ebag4]

Originally Posted by wintermute

I still use Unibox!! I have always much preferred it over winisd. It does require you to have microsoft excell though.

Playing with UniBox now, thanks for the heads up!

Best,
Ed

[JRKO]

Have a look at this page Test Tones 40Hz is very low - you may even be suprised what it sounds like.

To be honest you'll probably want it so start to drop off around 80-100hz as the room will more than likely boost the lower end. http://www.bobgolds.com/Mode/RoomModes.htm

Also the 12lta is efficient and large. Are you sure you want your kid to have something that could shake everything in the house with 5W?

[jagtek]

If I were you ,I'd stick with the Hammer super 12 cabinet. its 14.5x14.5x48
(3/4"MDF or plywood),port size 3.5" to 4.0" (depending on who you ask) and can do a solid 40-45 htz.
at least mine do (my port is 4.0") and it clicks all your boxes. I dont have software but have a test disk and have done alot of homework. It's about 4cu.ft and sounds full range with a supertweeter added.
JMHO, David