Theile/TL806 question

[Cboss]

A question for those of you that have built the Theile 1x12/ tl806.. what is your preference, and what are the sound/tone differences with the insulation installed versus not?

I'm just finishing one up and I haven't gotten the insulation yet, but I've heard it sounds amazing without

[django49]

AI may be your friend. See below. As best I recall, I did not use insulation when I built mine.....It has been a while. But the following makes sense.....Insulation would seem to defeat the purpose of this type cabinet.....

AI Overview

 

 

+1

 

No, a Thiele cabinet typically does not need insulation. While insulation can be added to increase the effective volume of a cabinet and alter its sound, it's generally not a standard feature in Thiele designs, which are built for maximum projection and minimal size. Adding insulation can dampen the sound and affect the projection, which is a key characteristic of a Thiele cabinet. 

Here's why:

• Thiele design focuses on projection:

  Thiele cabinets, often used for guitar speakers, are designed to project sound outwards, towards the audience. Insulation, by absorbing sound, can reduce this projection. 
• Insulation alters the sound:

  Adding insulation can change the way the speaker interacts with the cabinet, potentially improving bass response or reducing reflections, but this can also make the sound less desirable for those who value the typical Thiele sound. 
• Not a standard feature:

  While some builders might experiment with insulation, it's not a common practice in Thiele cabinets. 
• Ported cabs:

  If your Thiele cabinet is ported, insulation can affect the airflow and potentially reduce efficiency. It's generally recommended to avoid insulating the port area. 

In short: If you're building a Thiele cabinet, it's generally best to build it without insulation and see if you are happy with the sound. If you do want to experiment, you can always add it later, but be aware that it may change the intended sound characteristics of the cabinet. 

 

[Dave Scepter]

They normally don't have insulation However, you can fine-tune them depending on the speaker type, if you find them a little bit too bassy "boomy" or...

[Cboss]

12 hours ago, Dave Scepter said:

They normally don't have insulation However, you can fine-tune them depending on the speaker type, if you find them a little bit too bassy "boomy" or...

I built the cab from the electrovoice plans, which specify 3-in fiberglass on the sides top and back, I will probably just end up trying that; there's no fiberglass in it now and it sounds very defined in a good way, maybe a little bit Sharp.. really a fun easy project

[Dave Scepter]

1 hour ago, Cboss said:

I built the cab from the electrovoice plans, which specify 3-in fiberglass on the sides top and back, I will probably just end up trying that; there's no fiberglass in it now and it sounds very defined in a good way, maybe a little bit Sharp.. really a fun easy project

Yup, I've had about 3 of them with different speakers... I had 1 with EVM12 that sounded great at all volumes but had another with a Celestion 12 "can't remember the model" that sounded great at lower volume but became booming at higher volumes... that's the one I experimented with...🤘

[Cboss]

I'd like to make the Forte 1x12 and maybe 2x12 next, but I can't seem to find the plans.. if anyone has a link for these please post

[django49]

14 hours ago, Cboss said:

I'd like to make the Forte 1x12 and maybe 2x12 next, but I can't seem to find the plans.. if anyone has a link for these please post

This might help you get started. Finished dimensions are 22 x 16 x 14. Which should let you sort out the pieces......Internal reflecting panels on the sides and optionally on the back can be sorted our later. 

While I build 2 x 12s in both vertical and horizontal configurations, I think it is better to build two 1 x 12s and stack them. The 2 x 12 gets heavy real fast, esp if you use my preferred combo (Alnico Cream up, EVM down). And it is not exactly small. But it looks great!

But when I did build the 2 x 12, I essentially used a single center divider, making the two speakers individual/independent. And that helps if you want to do such as a Plug and Play panel to enable mono or stereo. 

[django49]

[Cboss]

That shop looks amazing!

[Cboss]

Update, I installed the fiberglass per the plans, and it definitely sounds better, more rounded, more punchy, less internal reflectivity, I could hear it before.. definitely recommended

[Dutchman]

Many years ago I built theile 18" speaker cabinets. A whole bunch for bottom end for a touring road show. 

We did use some Owen's Corning 703 in those cabs to dampen them which tightened up the Thump. 

I have also had the 806 12" with no insulation and EVM speakers. Gloriously loud!!!

[Cboss]

I'm really looking forward to cranking it with a hundred watt amp, I haven't really turned it up yet..LOVE the evm12l:)

[tbonesullivan]

On 7/16/2025 at 11:48 AM, django49 said:

This might help you get started. Finished dimensions are 22 x 16 x 14. Which should let you sort out the pieces......Internal reflecting panels on the sides and optionally on the back can be sorted our later. 

While I build 2 x 12s in both vertical and horizontal configurations, I think it is better to build two 1 x 12s and stack them. The 2 x 12 gets heavy real fast, esp if you use my preferred combo (Alnico Cream up, EVM down). And it is not exactly small. But it looks great!

But when I did build the 2 x 12, I essentially used a single center divider, making the two speakers individual/independent. And that helps if you want to do such as a Plug and Play panel to enable mono or stereo. 

The Vertical 2x12 Forte style cabinets I'm familiar with have two speaker compartments, with side vents on the top and a sealed bottom. I keep meaning to get one from Avatar but I actually kinda don't have many heads to plug into it, just lots of combos because I hate my back.

[Cboss]

11 hours ago, tbonesullivan said:

The Vertical 2x12 Forte style cabinets I'm familiar with have two speaker compartments, with side vents on the top and a sealed bottom. I keep meaning to get one from Avatar but I actually kinda don't have many heads to plug into it, just lots of combos because I hate my back.

The 1x12 I just finished is a back buster too..I guess the solution is roadies

[django49]

22 hours ago, tbonesullivan said:

The Vertical 2x12 Forte style cabinets I'm familiar with have two speaker compartments, with side vents on the top and a sealed bottom. I keep meaning to get one from Avatar but I actually kinda don't have many heads to plug into it, just lots of combos because I hate my back.

Yes, re Avatar. Having the flexibility to "design my own", I built it as two vented compartments. FWIW, I have also built a 2 x with a Thiele-style down and Forte up. Makes for a nice tone combination. Better than 2 Forte compartments using the same speakers? Jury is out on that.

Forte on the bottom and semi-open top (Fuchs/Vumble style) is also good for getting a big and varied tone. I clearly had too much time on my hands to build so many variations......Should anyone happen upon this neighborhood, you are welcome to check them out.

 

[tbonesullivan]

4 hours ago, django49 said:

Yes, re Avatar. Having the flexibility to "design my own", I built it as two vented compartments. FWIW, I have also built a 2 x with a Thiele-style down and Forte up. Makes for a nice tone combination. Better than 2 Forte compartments using the same speakers? Jury is out on that.

Forte on the bottom and semi-open top (Fuchs/Vumble style) is also good for getting a big and varied tone. I clearly had too much time on my hands to build so many variations......Should anyone happen upon this neighborhood, you are welcome to check them out.

 

Throw into this the fact that Mesa reissued their "Half back" style cabinets, with the front ported lower and open back upper. Would go perfect if I ever get around to picking up a Mark IV head...

[django49]

1 hour ago, tbonesullivan said:

Throw into this the fact that Mesa reissued their "Half back" style cabinets, with the front ported lower and open back upper. Would go perfect if I ever get around to picking up a Mark IV head...

Ah, timing.....I recently sold a pair of my old "half backs", EVM/Thiele lower, V30 uppers. And both for way less than the cost of a single new one. Of course shipping them way cross country would have been pricey. 😉

One of these days I will get around to selling my original Mesa rack gear.......

[Jimbilly]

On 7/19/2025 at 11:03 PM, django49 said:

Ah, timing.....I recently sold a pair of my old "half backs", EVM/Thiele lower, V30 uppers. And both for way less than the cost of a single new one. Of course shipping them way cross country would have been pricey. 😉

One of these days I will get around to selling my original Mesa rack gear.......

have you ever tried vintage low-wattage lightweight speakers in one of your 1x12s? Like Jensen or CTS along with a low watt head?

[django49]

4 hours ago, Jimbilly said:

have you ever tried vintage low-wattage lightweight speakers in one of your 1x12s? Like Jensen or CTS along with a low watt head?

Yes.....A variation or two of Mojotones (25-30 watts). An Alnico Blue works great (15  watts). I have also used a couple different Weber alnicos in 1 x 10 cabinets---about 30 watts IIRC). Light weight is relative though.