MLTL for Tannoy DU386? GM?

[DeonC]

Hi GM

You are the forum MLTL guru, so I wonder, is it possible or even worth it to put the Tannoy DU386 in a MLTL? At the moment I have them in Berkley reflex cabinets, as I was wondering if a damped MLTL would not be a better option. Here are the specs:

Vas: 483 l
Fs: ˙22 Hz
Qts: ˙0.18
Qa: 2.4
Qe: 0.2
Mmd: 68g
Mma: 22g
Sd: 770c m2
BL: 18.7 N/A
Re: 5.7 Ohm

Thanks,
Deon

 

[Bare]

Stuff them into Whatever you desire
But Tannoy 15's have a MASSIVE Bass output. These have proven to sound 'better than most' even when stuck into Half Barrels.
Not a lot of real world need to try and extract the last erg of Bass energy via a convoluted Enclosure. Unless you like cutting bits of wood and cobbling up a DIY enclosure.
Many clearly thrive on this exercise.. they keep doing it, year after year, after year

 

[DeonC]

Hi Bare

The bass on these is good, but definately not massive. Due to the low Q, they have a downward slope from just above 100Hz in a sort of extended bass shelf type of response, and roll away completely below about circa mid 30Hz. It is good bass, very tight and defined, just what proponents of low Q drivers talk about, but it ain't very deep or that powerful. That is why I'm curious about the possibility of a MLTL. I can't do it myself currently, as I don't have a mathcad program. I used to have a freeware mathcad program, but a hard-drive crash ended that. But even so, I trust GM's ability and knowledge on this subject far more than my own limited ability to sim.

Enjoy,
Deon

 

[Bare]

OK.. in fairness, the Berkley Boxes are likely the worst performing enclosures ever sold on by Tannoy. Understandable that you want better.
There are 'many' Box plans and suggestions available.. you are not the first in this desire.
Not overlooking that those Large/heavy LF cones DO work to their best with a decent amplifier of 20+ Amp current capability.. read Amp specs carefully and No, Price is Not the primary determinant in this.
Split the inputs to the Crossover IF you love your tubes and use those on the HF section.. Passive Bi Amping.
Start Here: TANNOY Monitor Gold dual concentric speakers
Follow links and even Google. G'luck

 

[sreten]

Hi,

The Berkeley cabinets are probably bigger than you need to go, my sims
indicate around 35 to 50L sealed and 70 to 100L vented, they are 98L.

Vent tuning I reckon is best around 28Hz and low bass boost would be good, passive
line level (6dB/octave) or active peaking 2nd order high pass, Q=1.5, f= 28Hz (+4dB).

rgds, sreten.

 

[GM]

Hi GM

You are the forum MLTL guru, so I wonder, is it possible or even worth it to put the Tannoy DU386 in a MLTL?

Greets!

Just one of many around here these days. MJK’s and others contributions have generated a plethora of [ML] TL and horn design gurus, some with far more comprehensive experience [at least measurement wise] than me.

Anyway, unless you plan to EQ them or just want to go lower, either of which requires a large net Vb, there’s no advantage to using a MLTL to damp such an already over-damped [low Qts] driver, though some folks will [critically] damp the vent as required to ensure there’s no audible/perceived vent pipe harmonic ‘ringing’.

You can still get the MC 8 demo at MJK's site.

So, what’s the game plan?

GM

 

[DeonC]

Hi guys

There are 'many' Box plans and suggestions available.. you are not the first in this desire.

I have many different box plans from Tannoy, including the corner and rectangular GRFs and Westminster horns (all of which are beyond my skills and available tools/workshop), various vented boxes, etc, but as Sreten stated, the Berkleys are the biggest reasonable vented boxes for these units. The DU386 is the lesser version of the HPD units, and the specs show it. Where the HPDs like a box as big as you can make it, these as not so good.

Start Here: TANNOY Monitor Gold dual concentric speakers

Thanks. I actually know this site well, but all the boxes are for the better versions of the 15“ DC. That is why I was hoping GM could help me with a MLTL. I was (vainly, maybe) hoping a MLTL would give me more than a standard vented.

The Berkeley cabinets are probably bigger than you need to go, my sims indicate around 35 to 50L sealed and 70 to 100L vented, they are 98L.

That is what my sims also indicated, going bigger brings no real benefits.

low bass boost would be good, passive line level (6dB/octave) or active peaking 2nd order high pass, Q=1.5, f= 28Hz (+4dB).

Thanks for the suggestion, but I think I'll pass. I am worried that I'll hurt them when I turn the wick up for some serious rocking.

Just one of many around here these days. MJK’s and others contributions have generated a plethora of [ML] TL and horn design gurus, some with far more comprehensive experience [at least measurement wise] than me.

My friend, you're being way too modest.

though some folks will [critically] damp the vent as required to ensure there’s no audible/perceived vent pipe harmonic ‘ringing’.

I was thinking experimenting with putting some foam or carpet underfelt in the port to see the effect. Less bass, but I would like to see what the effect will be.

You can still get the MC 8 demo at MJK's site.

Thanks, I will look into that.

Anyway, unless you plan to EQ them or just want to go lower, either of which requires a large net Vb, there’s no advantage to using a MLTL to damp such an already over-damped [low Qts] driver.

I actually was just hoping for a more extended and stronger bass than I am getting with the reflex. This has set me wondering, if a MLTL is not really going to give me what I want, how about a TQWP. Here is my idea:

I thought (and I know I'm crazy) of a 20Hz TQWP. Now that is one LONG pipe. I works out to 4.3m long by my calcs. But if I fold it into three parts, then the total height of the unit will be only about 1.6m eek:, only he says). Then to put the driver in the middle of the pipe, I just put it in the middle of the central fold, and listening height will be at about 0.8m, which is perfect for me. Then add a Karlson style cut to the end of the line (an idea stolen from the WBAL Betsy TQWP elsewhere on this forum- I have a pic that I'll try to upload), and the response could be more what I'm looking for. What do you think?

Thanks,
Deon

 

[DeonC]

Ok, guys, here is something I've been wondering about for a while. What will be the effect of cutting a Karlson-like slot into a port? Take a driver like the Tannoy DU386 mentioned above, and the Berkeley enclosure. The Berkeley has a large rectangular port, tuned lowish. So what would the effect be if I made the port longer, but cut a Karlson-style slot in it? As I understand it, the Karlson slot widens the range of frequencies that the port/pipe resonates at (see 1st pic below). I suspect the range of frequencies at which the port will resonate will have an upper limit set by the opening size of the port and the internal box volume. What do you think? So, to my thinking, the Karlson slot will either have one of two main effects:

1. The spread of frequencies which will be reinforced will be much wider than for the standard port, but the energy will be less. IOW, a greater spread, but weaker bass, or

2. The spread of frequencies which will be reinforced will be much wider, and with more power, but the load on the driver will be much more, therefore requiring more power. So in this scenario there will be more bass throughout the spectrum, at the expense of power handling (no free lunches).

So what do you think? I am personally hoping that option 2 is the correct one. What do you think?

Deon

PS. I added a pic to show what I meant with the double-folded 20Hz TQWP (NOT to scale, just a concept drawing).

 

[DeonC]

Here is a question for the horn guys- I've been looking at the plans for the rectangular GRF horns. They don't seem to difficult to build (unlike the corner GRF or the Autograph, etc). Only problem is that the GRF horns where developed for the Monitor Gold drivers, and they have different specs to my units. Will the DU386 work in these horns?

Thanks,
Deon

 

[ark]

i'm contemplating something similar with a 12" full range field coil driver.
i thought this was an interesting design by planet10 that could be scaled up.

http://p10hifi.net/tlinespeakers/FAL/images/demetri3D800.gif

 

[DeonC]

That does look interesting, but do they give the build plans at all (IOW dimensions)?

 

[GM]

I was thinking experimenting with putting some foam or carpet underfelt in the port to see the effect.

I actually was just hoping for a more extended and stronger bass than I am getting with the reflex. This has set me wondering, if a MLTL is not really going to give me what I want, how about a TQWP. Here is my idea:

This may be overkill, what I meant was using Harry Olson’s battery/switch ‘click’ or impulse response ‘ping’ test, i.e. tightly stretching one or more layers of cloth over the vent as required [or not] to damp ‘hangover’ ringing/‘boom’.

Again, MLTL will give more extended bass, but not more efficient bass except by tuning it ~ the same as a [Berkeley] reflex, though in your case where you want the driver up higher, then the MLTL is preferred.

To get some serious bass gain, it will require a huge TL limiting it to around two octaves, i.e. ~20-80 Hz, ~30-90 Hz, etc..

A BIB might be your best option for a wider usable BW if it can be corner loaded, though at the expense of ultimate SQ.

A compromise performance between these two would be your folded TQWT tuned to around Fs, i.e. ML-Voigt in today’s parlance.

GM

 

[planet10]

i thought this was an interesting design by planet10 that could be scaled up....demetri

A folded ML-Voigt. To fold nicely needs to have driver off-set at 50%.

dave

 

[DeonC]

Thanks Dave and GM. It seems the ML-Voigt is possible the solution I'm looking for. In my drawing, with the pipe being folded twice, it just so happens that the most convenient place to site the driver is at the mid-point of the pipe. This had me worried up to now as I had read that it should be at the 1/3-way point. Thanks for the good info. It is really appreciated.

Enjoy,
Deon

 

[GM]

Only problem is that the GRF horns where developed for the Monitor Gold drivers, and they have different specs to my units. Will the DU386 work in these horns?

Dunno, what are the Gold's specs?

GM

 

[DeonC]

Hi GM

Here are what I can find for the Monitor Golds:
Vas: 350l
Fs: 26Hz
Qm: 2
Qe: .22
Qt: .2
Mmd: 90g
Sd: 770 cm^2

The specs for the DU386 again (saves you from having to scroll up)
Vas: 483 l
Fs: 22 Hz
Qts: 0.18
Qa: 2.4
Qe: 0.2
Mmd: 68g
Mma: 22g
Sd: 770 m2
BL: 18.7 N/A
Re: 5.7 Ohm

The biggest difference seems to be the Fs and Vas, and the lower Qe/Qt. My knowledge of horns is very limited, but I hope they'll work. They'll definitely take up a lot less space than my TQWP idea. They rated down to mid 30Hz, and that will be more than good enough.

Thanks,
Deon

 

[DeonC]

GM, from your experience, do you think these GRF horns will be placement sensitive? I know the corner GRF is, but that I can understand considering the design and placement needs (sited in a corner with bare wall inbetween). I have an awkward listening room/space, so if they need a lot of breathing room around them (they'll be close to a big LP-shelf/bookcase on the one side), then this excersize unfortunately becomes academic. Well, for now anyhow. Later on I might move into a more suitable space, but that is in the future. Sorry for the many questions.

Deon

 

[GM]

My knowledge of horns is very limited, but I hope they'll work. They'll definitely take up a lot less space than my TQWP idea. They rated down to mid 30Hz, and that will be more than good enough.

Thanks,
Deon

Greets!

Without doing any sims, my SWAG is that it should work OK, though some series resistance may be required to better 'fit' the driver to the alignment.

Any response plots available? I don’t see how a ~6 ft^3 BLH is going to have any strong output to the 30s even backed up against a rigid/massive wall.

GM

 

[GM]

GM, from your experience, do you think these GRF horns will be placement sensitive?

BLHs typically need all the room help they can get and this one is no different, so up against a wall and preferably in a corner, ergo next to an LP rack will help it load to a lower F3, etc., though any gaps will act as resonant cavities.

GM

 

[DeonC]

Hi GM

Any response plots available? I don’t see how a ~6 ft^3 BLH is going to have any strong output to the 30s even backed up against a rigid/massive wall.

None available that I know of, but that is according to the Tannoy blurb. They were designed to be used in stereo pairs as a replacement for the GRF corner horn. The corner horns are some of those ridiculously complicated folded horns that were designed to stand in a corner and use the walls as extension of the horn. These I can see going down to the 30s, maybe. I agree the rectangular horns are optimistic, but I hope to hit about 40Hz. I just hope they'll be better than the Berkeleys below 100Hz to about 50Hz. Speaking of 50Hz, maybe I should try a Karlson. Only problem with the Karlson is the lower midrange irregularities that scare me. A SNKBY pipe maybe?

Enjoy,
Deon