The POOR man's Tannoy DMT - AKA "The PM-DMT"

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It all began some 2 years ago when I finally got hold of 2 Tannoy Coaxials (K3149) in perfect shape, BUT without the cabinets. Starting to think of a cabinet for these drivers, all kind of ideas popped up, from completely original, a TL version, to including adding a second 12" to make up for the, per generic opinion, "lack" of bass of the SRM12X. :confused:

Tannoy Super Red Monitor Project

This thread is supposed to result in an VERY affordable Studio Control Room Main speaker, close enough to the Tannoys, being the 215 DMT version. MOST likely will go for 12" drivers, commercially available everywhere at low cost. So nothing to do with the K3149, which is a one off, but trying to design a DIY Studio speaker based on Coaxials, with products of the shelf.

To keep it close to my rules of thumb (WAE style);

- Cheap, as in affordable for almost anyone (or better not that ridiculously expensive as currently on the market),
- As easy to handle as possible (the DMT weighs around 100 kg!!),
- Small in size (yet to be seen...... BUT smaller compared to the DMT),
- Sonically close to the real deals of this world,
- Passive AND Active versions,
- Loud enough to rock the boat in a Studio Control room (or your living room if you really want some domestic arguments... :redhot: (partner) :D (us)

THIS Post will be a kind of summary / content page. I will sum up all design decisions and point to the post where the conclusion is.

Attached an image of the Tannoy real deal.
 

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HF drivers

Did some homework and made an overview of 1" HF drivers to fit the Eminence Beta Coaxials (first choice in affordable Coaxial drivers). They come with a 1 ⅜" screw facility to mount the HF.

Selection criteria:

1 - Low Cross-over freq.
2 - Low price

All "type" made green are drivers with a almost flat response. One of these will be the first test driver. Most likely the B&C DE250 or the Faital HF104.

Dayton DT250T is also an option.

IDEA's??
 

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I like the intention / overall plan.

the Eminence Beta Coaxials [...] come with a 1 ⅜" screw facility to mount the HF.

Selection criteria:

1 - Low Cross-over freq.
2 - Low price

[...] Most likely the B&C DE250 or the Faital HF104.

Those two are bolt-on drivers. Wouldn't it be easier to start with screw-on drivers?

I've measured the Dayton screwed onto a small (I think Eminence) horn. The HF was a bit spiky compared to what I've seen measured for the B&C DE250. Part of the problem might be that the join between horn and driver wasn't great.

It seems like this is a fairly common problem - and not just for budget gear*. Maybe the quality of the physical connection needs to be your 3rd criterion.

* "One odd thing with the XT1464 waveguides – despite the claims of super hiogh tech the tolerance on the holes for bolting them to the waveguides seemed a bit off, I ended up having to file them a bit to get them to fit. Other than that they appear very well made and strong plastic though."

a new waveguide to try: 18Sound XT1464 | MiniRIG
 
Sigh.. Find and Buy a pair of Tannoy DC's.. seriously. The quality/sound of the Tannoys is pretty well exclusive the silly box they are fitted to. Some have fitted them to half Barrels others to elaborate Horns Nelson Pass has fitted his to Jensen Imperial boxes.. ALL sound Very good. Trying to mickey mouse up an facsimile is too much like trying to cobble together an Aston Martin.. in the basement from KIA bits.
But Hey! if you have absolutely nothing better to do with your time.. fill yer boots.
 
wae has got a pair of Tannoy DCs but this is a project which may eventually end up in a cheap, commercially available co-axial monitor if good enough and viable.
Suggesting to buy Tannoys is therefore of not much use to the OP I guess.

That being said I'd still look at 3 P-Audio drivers since they are cheap, screw-on to fit the Eminence CX and go low enough:
PA-D4155, 1.2k recommended xover, 20W, 100dB/1W;
PA-DE34S, 1.2k, 30W, 105dB;
BM-D440S Mk2, 1.5k, 108dB.

The first two retail at £29.70, the latter £47.33.
All from Blue Arran.

The frequency curve does depend on the horn a driver is used in so some experimentation may be necessary.

The Eminence itself has a Qts of 0.48 so should be suitable for a sealed enclosure which would simplify things quite a bit.
 
Sigh.. Find and Buy a pair of Tannoy DC's.. seriously. The quality/sound of the Tannoys is pretty well exclusive the silly box they are fitted to. Some have fitted them to half Barrels others to elaborate Horns Nelson Pass has fitted his to Jensen Imperial boxes.. ALL sound Very good. Trying to mickey mouse up an facsimile is too much like trying to cobble together an Aston Martin.. in the basement from KIA bits.
But Hey! if you have absolutely nothing better to do with your time.. fill yer boots.

That's OK Bare, but buying them will set me of 4000 euro's and still be a one off. Even if I would be able to get hold of 2 sets of drivers, it would only take a set of filters (design known at the Hilberink site), bang a pair of cabinets, done. So much for DIY...

Its not so much that I want to do an exact copy, but use the DMT / FSM concepts and, by carefully choosing very affordable drivers, make a commercially available product. Presenting it here on DIY audio, everyone could build it if desired.

About the KIA bits trying to cobble together an Aston Martin, you'd be supprised. Of course bits of KIA isn't an Aston Martin. But they can be just as good a car technically speaking, will never have the market value, but that's not what we aim for.

Give you 3 examples;
- On this site, loads of time, research and discussion has been going on around the Synergy horn. Some of the much brighter than me guy's finally made Top notch versions, using the B&C DE250 and 4 VERY cheap Pyle (I believe they where) drivers for the mid-range, like Danley Soundlabs also did in there versions of the Synergy horn and Eminence Kappa drivers for the low end (Danley used B&C BMS and FaitalPro (which I also use in some of my products). So it's cheap and mid-priced components for a top class product.

- I'm also looking into the concept of the transmission line, and am in the process of copy cat the PMC DB1. Guess what they use as drivers? 40 euro's worth LF and HF, you can buy them in any shop.

- Last one, I play bass guitar and always wanted a fretless bass. Owned various (not very cheap to expensive) versions and brands, never really liked them. UNTILL I walked in a local music store and saw a second hand (or maybe third hand) VERY Cheap 150 euro fretted bass, which sounded OK, unknown brand. I pulled out all the frets, filled the neck, produced some sawdust, replaced the pick-up's (175 euro's) and MY GOD, it's a jewel I will NEVER sell.

So Cheap is not the problem, cheap (or expensive) junk is.

Now I want to pick the best for the lowest price, understand and solve all issues and end up with a sonically very good product. We'll see how cheap cheap will be.

Shure can use some help, advise and alternative ideas. Take you pick

kind regards.
 
wae has got a pair of Tannoy DCs but this is a project which may eventually end up in a cheap, commercially available co-axial monitor if good enough and viable.
Suggesting to buy Tannoys is therefore of not much use to the OP I guess.


That being said I'd still look at 3 P-Audio drivers since they are cheap, screw-on to fit the Eminence CX and go low enough:
PA-D4155, 1.2k recommended xover, 20W, 100dB/1W;
PA-DE34S, 1.2k, 30W, 105dB;
BM-D440S Mk2, 1.5k, 108dB.

The first two retail at £29.70, the latter £47.33.
All from Blue Arran.

You right Charles, NO Tannoys this time.;)

Any idea what they sound like? (ANYONE?), they go low, affordable, screw-on.

kind regards.
 
If I had good Tannoy substitutes I would make something like this:

YouTube

Wait! I have some :D

I imagine older used coaxials are better (?).

I use Beyma KX15 coaxials with 3 hands of Dammar varnish on the woofer and new improved DIY XO (a mess) and they sound good now on my Autograph (the only way to go :cool:) enclosures.

I bought from desperation :( a pair of used P Audio big coaxials (the guy from commonsenseaudio said they bettered Tannoy), the P.AUDIO BM15CX38, after 10 years of hopeless anxious expectation: I didn't even have them tested yet :D
I guess anticipation anxiety ends when the item arrives...

If you can find a pair and your HF hearing is not what it used to be, they probably be very satisfying...

Cheers,
M.
 
I imagine older used coaxials are better (?).

I use Beyma KX15 coaxials with 3 hands of Dammar varnish on the woofer and new improved DIY XO (a mess) and they sound good now on my Autograph (the only way to go :cool:) enclosures.



If you can find a pair and your HF hearing is not what it used to be, they probably be very satisfying...

Cheers,
M.

Older = better, hmmm depends. We will go for NEW here :)

3 hands of Dammar varnish..... on a loudspeaker cone...:eek: Would you do THAT again?

Well my HF hearing is slightly but surely degrading, can't even remember during my whole life (64 now ) being capable of hearing a 20 kHz "tone". :confused:

Are the Autograph's hand build by yourself ? Look good, what's the horn shape bottom part of the enclosure ?

kind regards.
 
DMT 215 cross-over and Where to cross what

This appears to be the cross-over for DMT 215 setup.

It will be an interesting issue, placing the drivers (distance) and since we will be using 2x 15" (or 2x 12") of which one is the Coaxial we need to think of how to use the 3 drivers (2x LF and 1 HF). ALSO, I want to have the LF's to be identical, so NOT using one Coaxial and some "other" LF to fit in. Looking at the DMT's and FSM's, they always use LF with identical characteristics. I did read an article by Tannoy stating that they started the FSM and DMT by experimenting with 2 coaxials, of which one had the HF disconnected. This way you would use 2 identical LF drivers, sound the same, behave the same, parameters and electrical behaviour to the amp the same.

In our case, using 2 coaxials and add 1 HF to one of them, we could use a 1 ⅜" bold (long enough to fill the hole) to close the screw-in gap for the HF of the other coaxial. :p

The coaxial is a point source by default, crossing to the HF should be related to the LF's capability on producing "HF" (more like Mid Freq. / anyway as low as possible) and the ability of the HF to play low enough. Lets call this LF the coax-LF.

Blending in the other LF (Lets call this the sub-LF) with the coax-LF is an issue (acoustical interference). My view on this: The distance between the acoustic centres of both drivers (32 cm for the 12" / 38 cm for the 15" when placed tight against each other) makes for the ¼ wavelength giving the max frequency to cross the LF's. That would be some 250 Hz point (give or take).

Am I right here? (I would expect this to be the case).

If we would go 3-way (Charles advice) this freq. will be the Low Pass of the sub-LF and the high pass of the coax-LF. Adding a low pass to the coax-LF which is the high-pass of the HF would make the principle of the filter complete.

If we would go semi 2-way (my first thought) then the coax-LF would not get a high-pass filter. The ¼ wave distance between both LF would determine the low-pass of the sub-LF to avoid the acoustical interference. So both LF's would play the low notes up until the low-pass point of the sub-LF. Gives a more solid LF, which is what we need.

Looks like the filter opts for Charles way.. (I am not a cross-over expert, learning here:D) but shure looks like it.

3-way summary;

sub-LF < 250Hz
coax-LF 250 - 1500 Hz
FH - > 1500 Hz

semi 2-way summary;

sub-LF < 250 HZ
coax-LF < 1500 Hz
HF > 1500 Hz

that is IF the HF would be able to go not lower than 1500, we have some that can go to 1200 Hz.

:nod: or NOT? Comments?

kind regards.
 

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