Uh-oh -- the prospect of using a TL Series cabinet with a speaker not designed for it is going to lead me into a long Sunday rant. I apologize in advance, this post will be long.
TLDR: Swapping speakers into T/S cabinets that don't match their T/S parameters is a bad idea. Blown speakers may result.
GAStan wrote: ↑Sun Apr 13, 2025 12:30 pm
I cannot give you a comparative opinion as I do not have a Mojotone cabinet but I do have two Thiele TS806 1x12 cabinets, one with EVM12L and one with the WGS equivalent.
I heartily agree with all of the comments in your post -- the EVM-12L/TL-806 is compact, loud, clean and bassy without being boomy in an almost enigmatic sort of way. For people who are used to a 4x12 it seems odd that such incredible bass response could come out of such a small enclosure. I'd have no reservations about getting rid of large cab like a 4x12 and replacing it with an EVM driver in a properly matched T/S cabinet design. That's exactly what I did when I was renting apartments.
I'd be cautious, though, about speaker substitutions in a TL-806, which is why I quoted part of your post. Driver substitution in a T/S cab is a very BAD idea. Back in the day ('70s-'80s) everyone in pro audio knew that you couldn't take a T/S array and drop in an unmatched driver that the enclosure wasn't specifically designed to support, as that typically resulted in either poor performance or destruction of the driver. The idea of speaker swaps became popular among those musicians without an audio engineering background because someone at Mesa decided that it was a good idea to put Celestions in the TL Series cabinets (whose design came from EV) after EV had exited the musical instrument speaker market and left Mesa without speakers to put in their EV-designed cabinets.
IMO this decision for the Mesa speaker swap was made, not because the Celestion drivers were a good match for the EV cabinets, but because Mesa had EV-designed cabinets with no EV drivers to put in them and an ample supply of Celestions. So Mesa just stuffed the EV designed cabs with Celestions and pulled the wool over everyone's eyes by calling the new speaker used in the T/S cabinet a "Celestion Black Shadow" instead of an "EV Black Shadow," thereby implying that there was some degree of equivalence between the Celestion and EV speakers. (!) IMO that bad idea has become so widely accepted now that there is a cottage industry of enclosure builders who will gladly sell you a cab that's built to TL-806 plans without having any clue that the design is ill-advised for use with non-EV speakers, or that the cabinet design should be changed to suit the T/S parameters of the speaker to be installed in it. Today the guitar cabinet market proceeds with speaker swaps in a willy-nilly fashion, with the result that nobody understands what actually happened when they blow up speakers.
I blame Mesa for the propagation of this nonsense belief that it's safe to swap speakers willy-nilly into T/S ported cabinets. Mesa had relied upon EV engineers to design their T/S speaker/cabinets and didn't know what to do after EV decided to exit the industry. From an engineering standpoint it looked like Mesa had no clue as to what a bad decision they had made. [I'll leave it to the reader to determine whether Mesa was ignorant of the problem or whether Mesa purposefully used it as a means of selling replacement V30 on their web site.]
Why is this a big deal? In the T/S cabinets the box volume (air compliance) and the port dimensions are precisely tuned to the T/S parameters of the driver. The system will not function properly if a driver is used whose T/S parameters don't precisely match the design of the cabinet. When improper substitution takes place one of two things is likely to happen: the speaker will not develop the proper bass response due to misalignment of the driver and the cabinet, or the speaker will self-destruct when large signals are applied due to that same misalignment.
IMO Mesa did a great disservice to their customers by obfuscating the difference beween the EV and Celestion speakers by giving both the name "Black Shadow" and by placing Celestions into a T/S cabinet that was specifically desgined for EV speakers. At the time that Mesa did this Celestion refused to even publish T/S parameters for their speakers. In other words, it just wasn't possible to do the math to confirm that the speaker swap was safe because the new driver's characteristics were not published. Apparently, nobody at Mesa was worried about Thiele-Small math, or more importantly, Margolis-Small math. The result of this was good for Mesa, as they were spared the expense of redesigning a new T/S cabinet, and they ended selling a lot of replacement V30 speakers as the drivers blew-up.
Why does this happen? The primary design objective of a T/S cabinet is to extend bass response by tuning the volume of air in the cabinet, it's compliance, the dimensions of the enclosure's port, and the compliance characteristics of the driver to create a resonant system.
To put this into perspective it's important to understand that the TL-806 was never designed to be a guitar enclosure. It was designed for midband PA use, with an intended bandwidth of 83-1600 Hz.
In a T/S design the port (vent) produces the lowest octave of bass response. The tuning of the driver/port/air in the cabinet (and a bit of electronic EQ boost) define the usable lower limit frequency of the cabinet (fLL). They allow the vent to be driven to it's full acoustic output by the air in the enclosure moving through the port, rather than linear displacement of the driver along it's axis of excursion, to move air to produce sound. When reproducing the lowest tuned frequencies for the T/S cabinet, the amount of driver displacement (X) is actually very small -- the driver does not have to move very much to excite a large volume of air in the tuned system. The excursion of the driver at frequencies where the port is active is very small relative to sealed or open-back enclosures. This allows the harmonic distortion of the system to be markedly reduced in the ported cabinet and significantly reduces the chance of speaker bottom-out... that is, until you drive the T/S array with program material that exceeds fLL for the array, or drop in a driver that does not have the T/S parameters required by the cabinet.
The TL Series cabinets were not originally designed for guitar. They were designed for tri-amped or quad-amped PA use with the intent that they would be used in conjunction with the EV XEQ-1/2/3 crossover/equalizer, in order to provide a small degree of bass boost to provide flat bass response down to a defined f3 point AND to provide a high-pass filter with 12-dB-per-octave slope slope below the peak-boost frequency designed for the specific TL Series enclosure, to protect the driver by removing subsonic energy below the lowest usable cab frequency. It is an unfortunate reality that when the TL Series cabs are used for guitar applications the XEQ-1 is not used and the speaker is not afforded the protection against low-frequency over-excursion that the EQ system was designed to provide. In guitar applications, the TL Series cabinets are typically run naked, with no EQ boost to flatten their response and no crossover protection to prevent over-excursion below fLL. That creates a serious problem.
At fLL the driver performs at an operating point where the driver/cab/port/internal air are tuned such that the driver experiences almost insignificant displacement as it is the volume of air in the cabinet and the port that produce sonic output. If/when fLL is exceeded the tuning of the port is exceeded and speaker displacement becomes required to move air to produce sound. The problem is that the necessary driver displacement increases logarithmically the farther the port frequency is exceeded in the low direction, until the driver's maximum permissible displacement (Xmax) is exceeded. For an EVM-12L Xmax is only 0.13". The XEQ was mandated to protect the driver from over-excursion, as over-excursion rapidly kills drivers. Unfortunately nobody uses proper EQ when deploying the TL Series cabs for guitar use,with the result that there is no protection against this failure mode and blown speakers commonly result.
FWIW I have been using EV/TL series cabinets since the 1970s, properly protected by an XEQ-2 in a rack system with obscenely high power amps and I have never blown a speaker. Knock on wood.
If anyone is interested in using the TL Series cabs, I would recommend using them only with drivers that they have confirmed to be compliant with the T/S specs for the specific TL Series cabinet, and preferably with a proper 12dB/oct protection crossover so that Xmax is never exceeded. If those precautions are taken then it is unlikely that the driver will ever fail, short of several hundred watts of thermal abuse.
The TL-806 was designed for two EVM drivers: EVM-12L or -12S. I would use caution in using a TL-806 cabinet with any driver when used with a de-tuned guitar without adequate LF protection. If the frequencies being reproduced by a de-tuned guitar exceed the cabinet's port tuning frequency in the low direction then driver destruction is a likely outcome when subjected to large signals. I only use the EVM-12L + TL-806 combination with a normally-tuned guitar. For any de-tuning (or for 4-string bass), I use the EVM-15L + TL606 combination. I've been using the 12L/806 and 15L/606 combinations since the 1970s and I've never blown a speaker with guitar or bass and amps as large as a 300W SVT and kilowatt PA amps. When deployed properly the EV TL Series cabs are quite robust.
