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building tannoys...beginners help please

I’ve never seen the ‘brace of bizarreness’ in any Lancaster cab, though I have seen a couple of Yorks with it. In that version of the York it goes right across the centre of the driver and I always assumed it was an ill-thought-out attempt at a treble diffuser or something to stop beaming rather than a brace, but to be honest it made no sense to me. I’ve never heard a pair with it, only seen pics.
 
I concur as per FM's post;

Gold 12R in 120L/28hz and 220L/28hz(note the bass hump).

48635219722_229cfafb9c_o.jpg


48634724148_8a244ef2be_o.jpg
 
OK...120-220 is a huge leap. I imagine the gentle roll off of the smaller enclosure would sound more natural than the 3Db odd hump of the larger, with its subsequent sharp drop away from there?

The biggest change seems to be in 'Port air speed'. Can anyone explain the effect of this and it's significance please?

More imagining suggests that adding 10L to 120 isn't going to make that much difference, but if 120L sounds (is well known to sound) as good as it gets then why mess with it? I'll just need a taller plinth :) It also resolves the port size question since it's a known factor. Good.
I still can't find any clear drawings of that Lancaster cabinet and the damping required therein so that's my next quest I think. My own link above is clear in all but one or two dimensions. All links most welcomed.
 
@cooky1257 , do you have a link to the T/S parameters for the MG12-HE? I've looked on HH's site but can't find them, I'm sure he had a spreadsheet with all Tannoy DC driver specs on it?
 
Forgot about this one.

Sealed is a lot more forgiving than ported. The main thing to worry about is xmax as the box gets bigger, but that's less of a worry with a large driver like a Tannoy (Depending on the xmax (anyone know 15" MG xmax?) - I'd be very surprised if your ears didn't give up well before the driver hits the end stops).

This is the Tannoy Monitor Gold 15 modelled in a 75ltr (grey line) and 200ltr (black line) sealed enclosure. The red line is just a rough guess at what I think the crossover does to the frequency response.

C83qbrA.jpg
If you look at post 81 and compare the sensitivity of the K Series LF raw driver plot vs post xover plot you'll see it doesn't change, the HF half of the plot shows the expected curve of a compression driver without any eq/CD compensation and the significant padding down of the HF output. For what you suggest to be happening the bass driver raw sensitivity in a MG would need to be around 100dB/w to get us to the stock 94dB/w.
 
No but what happens to imaging, soundstage and so on if the two cabinets are not symmetrical?

Here's the thing, the Tannoy driver is a horn with 60 degree conical dispersion, Tannoy usually place the driver pretty much equidistant from the sides and I'd assume it's so as to maintain a symmetrical horizontal dispersion/response.
 
If you want to learn I’d advise getting a copy of Vance dickasons loudspeaker design cookbook. Volume 7 is the latest iirc. It will have plenty of info and examples on ported enclosures and tuning. And fill in a lot of the basics that are missing/useful to understand when starting

If you want to do some basic enclosure modelling, download winisd, the drivers you’re using might already be on the database, haven’t looked for tannoys so not sure. If not you can add the ts specs in and see what happens to responses when volume is changed, and do some port tuning there too. Could save a lot of trial and error

Basically, air velocity needs to be kept down on ports so it isn’t audible, which requires it to be wide enough, but widening a port increases tuning frequency, which then in turn needs to be lengthened to lower it back down again to where you want it. Around the fs of the driver is good if possible. 17m/s tends to be the golden number but if you go higher than that at moderate volumes without exceeding it a long way you’ll be fine
 
Only point in 'going' large ie 220L is some+3dB output below 40hz over the curves for 75L , otherwise they look almost identical. Depends on your circumstances/space WAF etc, I suppose if you want to get the last drop of bottom end out of them using sealed. Very similar to FB's post upthread.

220L

49454747691_9ed4f318e3_o.jpg


75L

49454278748_70a294b4a6_o.jpg
 
No but what happens to imaging, soundstage and so on if the two cabinets are not symmetrical?
My mistake as I didn’t read your post properly. I thought you were going to mount the driver centrally top to bottom and that’s why you needed an 8” plinth to get the tweeter at the correct height but you did clearly state even distance from top and sides of 3.5”.

Apologies, carry on, great thread.
 
If you want to learn I’d advise getting a copy of Vance dickasons loudspeaker design cookbook. Volume 7 is the latest iirc. It will have plenty of info and examples on ported enclosures and tuning. And fill in a lot of the basics that are missing/useful to understand when starting

If you want to do some basic enclosure modelling, download winisd, the drivers you’re using might already be on the database, haven’t looked for tannoys so not sure. If not you can add the ts specs in and see what happens to responses when volume is changed, and do some port tuning there too. Could save a lot of trial and error

Basically, air velocity needs to be kept down on ports so it isn’t audible, which requires it to be wide enough, but widening a port increases tuning frequency, which then in turn needs to be lengthened to lower it back down again to where you want it. Around the fs of the driver is good if possible. 17m/s tends to be the golden number but if you go higher than that at moderate volumes without exceeding it a long way you’ll be fine

winisd not for Mac.
Thanks Paul but I'm not technically able enough to understand this stuff. I guess there is somewhere I can just ask what port size I need in a 130 litre box with monitir gold 12" R's and someone clever will provide the measurements. :)
Not even got the speakers yet so, no rush.
 
Ah ok, don’t use a Mac so...

None of us are to start with, but have to start somewhere :) if you can find a windows device to use winisd is very easy to do some basics on, and shows everything in graph forms so easy to compare volumes etc

If not, then post up some t/s parameters of the drivers if you can get them online or from whatever supplier you used, can have a look
 
If you look at post 81 and compare the sensitivity of the K Series LF raw driver plot vs post xover plot you'll see it doesn't change, the HF half of the plot shows the expected curve of a compression driver without any eq/CD compensation and the significant padding down of the HF output. For what you suggest to be happening the bass driver raw sensitivity in a MG would need to be around 100dB/w to get us to the stock 94dB/w.

I can't read anything in those plots, the writing is too small. Do you know how low in frequency their anechoic chamber is accurate too?

According to my simulations the raw Monitor Gold 15 is 97.57db at 2.8v 1mtr. Troels Graveson seems to think they are 90/92db with the crossover in a 100ltr sealed box, and measure flat down to 50hz with a nearfield measurement, which I find hard to believe as that would imply even more correction than my guess!. Simulations of the raw driver show them starting to roll-off at 300hz, so the crossover must be correcting for that, but without reverse engineering the crossover, we can only guess at how much.
 
I can't read anything in those plots, the writing is too small. Do you know how low in frequency their anechoic chamber is accurate too?

According to my simulations the raw Monitor Gold 15 is 97.57db at 2.8v 1mtr. Troels Graveson seems to think they are 90/92db with the crossover in a 100ltr sealed box, and measure flat down to 50hz with a nearfield measurement, which I find hard to believe as that would imply even more correction than my guess!. Simulations of the raw driver show them starting to roll-off at 300hz, so the crossover must be correcting for that, but without reverse engineering the crossover, we can only guess at how much.
I was under the impression that the MG15 was more or less flat to 100Hz in the sealed Lancaster enclosure and has a sensitivity of 95dB/1w/1m?
 
I bet someone could take one of those B&C 12" co-ax prosound drivers, design a box and crossover for it, and have something pretty decent. You could even try to mimic the transfer function of a classic Tannoy.
 


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