EV TL806 Thiele

[stelligan]

Btw, I'd love to try one of these ported boxes....

Scott,

PM me, I'll ship you one to noodle with. It's just sitting here empty. I have another in heavy use with an EV - port cover removed.

[Bob-I]

Thanks Bob. Multi-tasking and looked at the drawing and not the notes. I have it now, thanks again.

Pretty cool how the extend the bass response by cutting it back, and eq'ing it in.

[BobW]

Any comments on the TL606 vs. the TL806 for a 100W ODS? I looked at the specs, and just want to know if anyone has performed an actual A / B test.

Presently, I'm using a Bassman 2 - 12" enclosure and want to try something new.

[blinddog]

Bob-I,

Yeah I saw that and thought the same thing, kind of WTF. I am reading it that blocking the port extendes the frequency range ( the "one half octave extension), but doesn't give flat response so that is why you eq.

But the other cute thing is on the graph the closed port with eq doesn't seem to have as extended low end as the non eq-ed at low db. Seems to me like blocking the port isn't worth the trouble, which might explain why I didn't see it blocked in the photos previously.

I see mine not having the port blocked, then when I have time to play with it maybe experimenting with blocking it.

[glasman]

potentially dumb question here but...

Am I reading the EV plans right? I am seeing a covering(air tight) over the middle port of the cabinet. The reason I'm asking the the photos of the cabinet don't seem to have that port covered. Not trying to be a critic, just trying clarify. I got the impression it would make a difference in sound and performance, if the port is to be covered, and wasn't.

You are correct, the plans include a small cover plate to close off the center section of the port. This lowers the box tuning frequency, but technically requires a 6db electronic boost circuit to compensate for the roll off in response.

As the low E fundamental for a guitar is about 80hZ, the cover is not really necessary.

Gary

[stelligan]

You are correct, the plans include a small cover plate to close off the center section of the port. This lowers the box tuning frequency, but technically requires a 6db electronic boost circuit to compensate for the roll off in response.

As the low E fundamental for a guitar is about 80hZ, the cover is not really necessary.

Gary

FWIW - I like port covers off. For me, an audible difference for the better. The pics in my post were from when I got the boxes out of storage. They had funky rheostats mounted in the cover plates.

[odourboy]

FWIW - I like port covers off. For me, an audible difference for the better.

Ditto!

[muchxs]

But FWIW, I have reversed uncle howies dimensions based on measurements of out buddies cabinet and based on plugging them into the theile equations he was pretty close to maximally flat. But I would not have used cardboard ports due to thier lack of rigidity. Also 3.5" ports are TOO small for the volume of the cabinet and the throw of a 12L. There is where howie was wrong.

There is where howie was wrong.

"Incorrect" might be a nicer way to put it.

"Incorrect" on the basis of several assumptions:

"Flat" frequency response is desirable.

Low frequency extension below the range of the guitar is desirable.

The difference in tone between a conventional closed back speaker cabinet and a ported cabinet is due to a number of factors not the least of which is speaker damping. A closed back makes the enclosed volume in the cabinet act as an air spring which damps speaker movement. A Thiele or a ported cabinet taking Thiele-Small parameters into consideration acts more like an open back cabinet in regard to damping.

A speaker mounted in an open back cabinet is relatively undamped although phase cancellation comes into play.

Port dimensions that appear incorrect are only incorrect outside their intended frequency range.

[moj067]

I used to sort of tune tranmission line speakers with foam in those ports, playing w/ thickness and density of material FWIW.

[BobW]

Here' a few pics of my Thiele cab (TL806) in progress. It will be loaded with an EVM 12L classic.

[billyz]

Man, that is one Hercules built cabinet. How much does it weight ? would love to hear it when it's done.

[muchxs]

It seems Dumble's original preferred material for cabinets was lumber core plywood. I got a big stack of the stuff as surplus when a commercial cabinet shop (kitchen cabinets) moved to their new location. I cut up my windfall and made it into roughly TL806s sized cabinets (non-ported) then sold them for bargain price.

Anyone ever look inside a classical guitar? The good ones have a lot of carefully shaped and sculpted braces inside. The difference is that a classical guitar is supposed to vibrate while a TL806 is supposed to be as dead as it can possibly be. It's possible however to shave off a good deal of weight with minimal tradeoffs in strength by sculpting the internal braces.

[glasman]

If weight is not an issue a concoction of roofing asphalt and sand makes a dandy dampling compond for speaker cabinet walls.

A simple approach is to use a sinple cross bar to couple the sides of the cabinet and one or two top to bottom to provide stiffness. My sub woofers for my PA are built in that style. Light weight and dead as a donut. Thoe cabinets are 24x24x30" high.

Gary

[heisthl]

Any comments on the TL606 vs. the TL806 for a 100W ODS? I looked at the specs, and just want to know if anyone has performed an actual A / B test.

Presently, I'm using a Bassman 2 - 12" enclosure and want to try something new.

Try this on your bassman:

[Todd Hepler]

A Thiele or a ported cabinet taking Thiele-Small parameters into consideration acts more like an open back cabinet in regard to damping.

I have to take issue with this quote, as it is not entirely correct -
A ported enclosure actually exerts greater control on the speaker's cone at and above the resonant frequency of the driver/enclosure.
The disadvantage of the ported enclosure is that at frequencies below resonance the driver becomes unloaded and produces very little output compared to the sealed enclosure, emulating the scenario outlined in your quote above.
The question that we should ask is "what is the tuning freq of an EVM 12L in a properly designed ported enclosure, and does it even come into play at the lowest frequency on a guitar?"
The plans attached to an earlier post list the tuning frequency (Fb) and the Rolloff frequency (F3) of the TL806 enclosure, both with and without the port cover:

Stepdown (Port cover installed) F3:130 Fb: 53
Normal (No Port Cover) F3:83 Fb: 75

As you can see, the tuning frequency of the 'normal' alignment has an F3 point at exactly the guitar's lowest fundamental frequency; 83HZ.
The Fb of the 'normal' alignment, at 75HZ, should be low enough to not be an issue with a normally tuned guitar.
For a guitarist using lowered tunings the 'stepdown' alignment may be desirable, or even a sealed enclosure which exhibits a much more forgiving low frequency rolloff.

-Todd