Tannoy Enclosure

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izzy wizzy
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#1 Tannoy Enclosure

Post by izzy wizzy »

What started as a Tannoy R-GRF enclosure has met a dead end in another thread.

So let me start again. I have Tannoy !5" golds I like a lot and want them in a vented box no more than 600mm wide.

What became apparent is this stuff can be modelled and accurately enough so I don't need to build for test and then rebuild for final which is a relief. Is there some sim software I can play with? I have an IMP Analyser I've yet to setup which may or may not be handy in this pursuit. Hoping handy with not too much frustration.

That will lead me, with hopefully some help of speaker builders round here, to a point where I can build some boxes that are domestically acceptable. Domestically acceptable means about 1m or so high and about 400 to 500mm deep. I can be flexible on any of this but the 600mm wide thing otherwise can't fit it along the wall I have with everything else.

So far I've gathered narrow vent tuning, flat anechoic tuning , ignoring room gain etc are out. These guys, for the most part, will up against a back wall but hopefully on casters so I can move them out and around if necessary. I'm used to at the moment moving me round to avoid boomy nodes but then, my current speaks are not on casters and sit out in to the room.

What should my next move be?
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#2 Re: Tannoy Enclosure

Post by Ant »

Personally I'd shove them in a sealed box and see what comes out.
My big 15" fanes are in a 120l sealed box and are a little smaller than the proposed maximum dimensions if your tannoy boxes
My room helps below 40 hz, hinders abit between 60 and 80hz because of a mode, but i think they are pretty reasonably balanced.
Chris can suggest a decent bit of Sim software, winisd?
I'm not sure where you are, but if you are anywhere near me you are more than welcome to have a listen to these if you think the concept is something you might want to look at.
I suppose the 15" fanes are similar in size and concept to the big tannoy so fairly close
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#3 Re: Tannoy Enclosure

Post by chris661 »

For the basics, WinISD Pro is where I'd start for sure. Hornresp is more flexible, but has limited advantage if you're only simulating bass reflex boxes.

IMO, a sealed box isn't a bad place to start. The advantages go like this:
- They have output down to very low frequencies
- They can be nice and small
- Easy to build
- Gradual rolloff might play better with your room

The primary advantage of a ported box is that you can have more output from a given amount of speaker. Since you have a pair of 15" cones, I don't think that'll be a huge issue.


A lot does depend on how your room is, though. Brick houses tend to give you quite a lot of extra bass since you're effectively in a pressure vessel.
To illustrate this, here's the simulated curve of my current HiFi speakers:
Image
The -3dB point is around 50Hz, which is what you'd expect for a decent 8" midbass in a big-ish sealed box.

Here's what happens when I put them in my room, mic at the listening position:
Image

It's quite a difference.

If I'd used a "textbook" ported alignment, the speakers would've been flat to 30Hz (give or take) and then fall off very quickly. The result would've been an even bigger bump in the 40Hz range (since the speakers are now flat through that range), and losing the very-low-frequency output.

Since I didn't need the output of a ported box, a sealed box has been a better move all-round. It still needs some EQ to knock the low end into shape, but not as much as a flat ported box would have.


So, I design my HiFi around using EQ to get speaker & room working nicely together. Is that an option here?


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#4 Re: Tannoy Enclosure

Post by Cressy Snr »

Bring back tone controls I say. :wink:
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#5 Re: Tannoy Enclosure

Post by Scottmoose »

Well, as noted this rather depends on the output impedance of the amplifier being used with them. However, for the sake of a baseline, if we use the published data for the Gold 15in on the Tannoy Monitor enthusiast site (which assumes a pure voltage source, & no series R in circuit), then I'm not sure I'd be using a sealed box.

For reference, under those conditions & assuming a well built box lagged with roughly 1in acoustic fibreglass or the equivalent:
Qtc = 0.707 (Butterworth). Maximally flat. Vb = 25.4 litres, Fb = 97Hz (nearly), F6 = 74Hz (nearly).
Qtc = 0.577 (Bessel). Lowest group delay. Vb = 41 litres (nearly), Fb = 78Hz (nearly), F6 = 68Hz (nearly).
Qtc = 0.5 (Critically damped). Fastest settling. Vb = 57 litres, Fb = 67Hz (nearly), F6 = 65Hz.

If you factor in 0.5ohms series R for typical speaker wiring, connections &c. while assuming the same voltage source (v. low output impedance) amplifier, those become:
Qtc 0.707. Vb = 30 litres, Fb = 90Hz, F6 = 70Hz (nearly)
Qtc 0.577. Vb = 49 litres, Fb = 73Hz, F6 = 65Hz
Qtc = 0.5. Vb = 69 litres, Fb = 62Hz (nearly), F6 = 62Hz (nearly).

So still a bit small. However, if we assume about 2.5ohms, which is in the region of a lot of SET amplifiers, it gets a bit more realistic:
Qtc = 0.707. Vb = 54 litres, Fb = 70Hz, F6 = 53Hz (nearly)
Qtc = 0.577.Vb = 90 litres, Fb = 56Hz, F6 = 50Hz (nearly)
Qtc = 0.5. Vb = 134 litres, Fb = 48Hz, F6 = 48Hz (nearly)

There is no advantage to a larger box volume & lower Q than 0.5.

As far as vented boxes are concerned, in practice for a voltage source amplifier, about 80 litres tuned to c. 42Hz should work. If we're talking a SET amplifier, I'd look toward about 110 litres tuned to around 33Hz - 34Hz for use near boundaries.

Told you the box sizes weren't huge. ;) OK, if we kick output impedance up to about 4ohms, then that will go to about 200 litres, and roughly 28Hz tuning.
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#6 Re: Tannoy Enclosure

Post by izzy wizzy »

Thanks guys. That's a lot of info for me to absorb which I'll do later. I'll have to understand what these tuning frequencies mean and how they relate to frequency response. On my limited understanding, I thought that reponse drops off more rapidly in a ported box than a sealed one so tuning for 60 to 70Hz doesn't sound great so maybe that's where my knowledge is missing.

I've downloaded winisd for a play later.

I'm driving these with my GM70 PP amp. Quite what it's O/P Z is I have no idea. I'll try and see if I can work that out.

Although my current house is brick, most of our future houses these will end up in will have a lot of windows and probably be stud walls.

The current York enclosure is a vented 230L box, with 350cm2 from 2 ports if that means anything. Given the figures being talked about, those are nothing like what I'm using now. So stupid question is, why would that be? Is that something to do with the Yorks being from an earlier era with relatively speaking high amplifier output impedances? Or has the series inductor in the woof got something to do with this? Or is this something like what was mentioned in the other thread about having a very big box tuned low?

EQ is not really an option Chris as I have one amplifier driving the speaker through a crossover and no DSP thank you. I can see the advantage in EQ but it's not for me. I'll live with bumpiness in the LF if I have to which I guess I always have. Obviously if we can do better without EQ, then bring it on.
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#7 Re: Tannoy Enclosure

Post by Scottmoose »

izzy wizzy wrote: Sat Feb 22, 2020 4:39 pm Thanks guys. That's a lot of info for me to absorb which I'll do later. I'll have to understand what these tuning frequencies mean and how they relate to frequency response. On my limited understanding, I thought that reponse drops off more rapidly in a ported box than a sealed one so tuning for 60 to 70Hz doesn't sound great so maybe that's where my knowledge is missing.
Below tuning, a vented box ultimately unloads at 24dB/octave. Some variation depending on specifics however, but it will always finally transition to that; in effect the driver becomes unbaffled with no real resistive load. So if you hit a vented box with a signal below Fb (box / system tuning), you'll see the driver flap around at [relatively] high excursions, for little audible output. A sealed box ultimately rolls off 2nd order, with a Q factor (Qtc) that determines the frequency at which it starts to roll off & the sharpness of that transition: the higher the Q, the sharper it becomes. Anything over 0.707 is peaking at tuning. Not automatically a bad thing but generally best avoided unless you know exactly what you're doing and why. The driver never unloads as such as there is always the air spring of the enclosure present. So in general, a sealed box doesn't necessarily have as much LF output as a vented, and the lower Q types start a shallow roll off at a higher frequency, but they can often get as low or lower, and they keep a tighter grip at the bottom end on the driver.

Not all vented boxes are equal though; badly designed ones deserve the reputation they have. Well designed ones are perfectly functional. Everything is a compromise; it's about selecting what works best for you.
I'm driving these with my GM70 PP amp. Quite what it's O/P Z is I have no idea. I'll try and see if I can work that out.
I'll take a SWAG at that and suspect it'll be with wire, connection resistance, probably in the order of about 1.5ohms at the crossover.
Although my current house is brick, most of our future houses these will end up in will have a lot of windows and probably be stud walls.


I would suggest a moderately, but not heavily, damped alignment likely to be the order of the day then. Stud walls can leach low frequencies. For vented boxes, a duct with adjustable length is very useful here as it gives some tuning flexibility.
The current York enclosure is a vented 230L box, with 350cm2 from 2 ports if that means anything. Given the figures being talked about, those are nothing like what I'm using now. So stupid question is, why would that be? Is that something to do with the Yorks being from an earlier era with relatively speaking high amplifier output impedances? Or has the series inductor in the woof got something to do with this? Or is this something like what was mentioned in the other thread about having a very big box tuned low?
To a point. The above were done using current design method which was developed by Small, based on previous work by Thiele and Novak. Basically comes out of lumped element electrical filter theory, and is very accurate if you know what it does and doesn't cover. The York predates that work, and is closer to traditional bass reflex design, which partially keyed off driver dimensions & ratios related to these. Tuning will depend on how long the vents are, but the end results using that approach were at the time less predictable as far as system alignment went. Since amplifier output impedances were often high, and a low tuning was often (not invariably, but often) favoured, a big box tuned low was the order of the day. Acoustically efficient design actually -they knew what they were doing. It doesn't always suit current size / alignment requirements though, since sources have changed and objectives have shifted a bit.
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#8 Re: Tannoy Enclosure

Post by chris661 »

izzy wizzy wrote: Sat Feb 22, 2020 4:39 pm
EQ is not really an option Chris as I have one amplifier driving the speaker through a crossover and no DSP thank you. I can see the advantage in EQ but it's not for me. I'll live with bumpiness in the LF if I have to which I guess I always have. Obviously if we can do better without EQ, then bring it on.
Fair enough. It's easy for me - my primary source is a laptop, and so I use an EQ program that sits between the media player(s) and the output.

With stud walls, I'd take Scott's recommendation on a ported box.

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#9 Re: Tannoy Enclosure

Post by izzy wizzy »

Scottmoose wrote: Sat Feb 22, 2020 5:41 pm
I would suggest a moderately, but not heavily, damped alignment likely to be the order of the day then. Stud walls can leach low frequencies. For vented boxes, a duct with adjustable length is very useful here as it gives some tuning flexibility.

Since amplifier output impedances were often high, and a low tuning was often (not invariably, but often) favoured, a big box tuned low was the order of the day. Acoustically efficient design actually -they knew what they were doing. It doesn't always suit current size / alignment requirements though, since sources have changed and objectives have shifted a bit.
I've taken some points from your post that indicates a direction I think. Some tuning flexibility sounds a good idea. I'm assuming by modern standards, I'll be dealing with highish output impedances.

Then there's the part about being acoustically efficient. That sounds a good thing isn't it? But then there's the 'doesn't fit curent size/alignment requirements?' Does that mean we're not used to big boxes anymore? And do our sources being mostly low Z (solid state) and boxes being closed, we have lots of power to make them move loads? Which if this WAG is true, would be the opposite of what I'm trying to do?

So let me make an assumption of some of the above being right, is this indicating I might be heading for a big box tuned low with a variable port length?
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#10 Re: Tannoy Enclosure

Post by IslandPink »

Stephen -to make some of the above information a little easier to understand, 'F6' is the frequency at which the (bass) output has dropped by 6dB from the midrange.
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#11 Re: Tannoy Enclosure

Post by Scottmoose »

Yes. More useful than F3 (which is more or less useless as a practical guide, as Toole and others demonstrate).
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#12 Re: Tannoy Enclosure

Post by Scottmoose »

izzy wizzy wrote: Sat Feb 22, 2020 7:11 pmI've taken some points from your post that indicates a direction I think. Some tuning flexibility sounds a good idea. I'm assuming by modern standards, I'll be dealing with highish output impedances.
Moderately so, but not spectacularly.
Then there's the part about being acoustically efficient. That sounds a good thing isn't it?
Up to a point it is, until box volume swamps compliance & Q. The real point about Small et al's work is that they allow you to hit given alignments, and to 'get the most out of the least'. But people often tend to gravitate toward the smaller options & ignore the possibility of a larger box for a similar[ish] alignment, which is closer to the older methods.
But then there's the 'doesn't fit curent size/alignment requirements?' Does that mean we're not used to big boxes anymore?
See above. The traditional vented boxes were large, but usually the alignment wasn't especially well defined in advance and could be difficult to empirically tune if you had specific objectives. The advantage of filter theory is that you can predictably hit specific alignments, and usually (not always) achieve them in a smaller box size, meaning less wastage. It's not been entirely advantageous; like anything, it's only as good as the person using it & a little bit of knowledge can often be a dangerous thing. But it does make things easier for more people. And with the fashion from the '80s for reduced cabinet sizes, hand in hand with the progressive decline of home audio as a widespread interest / hobby, large speakers died away. It started in the late '60s with the increasing availability of [relatively] cheap power & progressed from there. Over-simplified, but that's about the size of it.
And do our sources being mostly low Z (solid state) and boxes being closed,
Sealed boxes are the minority in commercial hi-fi. 99.99% are some variation of the vented theme.
we have lots of power to make them move loads?
Correct: smaller bass / midbass drivers with increased power-handling were developed as a result. But we're not talking about those, we're talking about an old 15in Tannoy coaxial, so you design accordingly to what it is.

A degree of rationality is required here. All 'modern' T/S filter theory is is a tool designed to make your life easier, analyse what is possible & achieve a desired alignment predictably rather than flailing around in the dark or wasting a lot of time and material unnecessarily. What you do with it though is up to you, and it can't design a quality speaker for you. That's down to the designer. It just shows you what you're doing. The message here is: do not leap on the phrase 'it allows you to achieve a given set of results in the smallest possible box volume' and assume it is fixated upon small boxes. It isn't. It can help you to achieve the smallest practical cabinet size if that happens to be your objective; if that isn't your objective, it can help you analyse what you are doing there also. For example: the old York enclosure is larger than it really needed to be; you can reduce that somewhat and get superior performance in the process, but these things are relative; you balance out one area against the other, and I would generally recommend when the space is available using the largest practical enclosure that gives you an alignment that suits your requirements.
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#13 Re: Tannoy Enclosure

Post by izzy wizzy »

Thanks Scott. That was very helpful. I've been doing a lot of reading and some of it anecdotal as to what sort of cabinets seem to make them work well and that would imply things on the larger side especially for the older 15" monitor golds with the hard edge.

One thing that comes up is some kind of decision relating to choosing an alignment. I've read the various alignments have pros and cons. Is there something somewhere that might help me choose the alignment I could be after?
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#14 Re: Tannoy Enclosure

Post by Max N »

Hi Stephen
I am a complete amateur when it comes to speakers, but one piece of advice I can offer - take the room interaction seriously. Find out what your room mode(s) are and how peaky. I think you are already aware of this, but keep it in mind when deciding which way to go.
My experiments with speakers have had mixed success. Any speaker which has decent output at 40Hz results in boomy, one-note bass. I have built carefully designed vented boxes and then ended up using them sealed.
Hope this helps
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#15 Re: Tannoy Enclosure

Post by izzy wizzy »

Max N wrote: Sun Feb 23, 2020 11:28 am Hi Stephen
I am a complete amateur when it comes to speakers, but one piece of advice I can offer - take the room interaction seriously. Find out what your room mode(s) are and how peaky. I think you are already aware of this, but keep it in mind when deciding which way to go.
My experiments with speakers have had mixed success. Any speaker which has decent output at 40Hz results in boomy, one-note bass. I have built carefully designed vented boxes and then ended up using them sealed.
Hope this helps
Max
That's a story I read about quite often and may go some way towards some of the recomendations I've had - stick it in a box and see what happens.

What I fancy would be some kind of adjustable port or ports. Not only to fine tune but maybe change something a bit more dependent on room as these are primarily aimed at a future room that I don't have experience of. Tannoy do this on one of their models where the 2 ports can be adjusted invidually from fully open to closed. How I'm not sure but if this is possible for this design, is it worth having? And how would be a good way to do it? Shove a sock in the port mightbe one but I'm hoping for something better.
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