Soffit mounted 15" Tannoy Dual concentric project

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Hello DIY community.

I am undertaking my first speaker building project, and it's a doozy. My grandfather passed away in the spring and he was an avid audiophile. He was also a hoarder, and it took us many months to comb through his belongings and pick out what was worth saving. One item that did not need thinking about was his 15" Tannoy silver from 1959. It was his prized possession, and he requested that I have it. Well, I got that thing out of there as soon as I could (wasn't easy), and after many months, and after consulting with my brother I have decided to sell it in order to build a set of mains for my recording studio. He wanted my brother and I to make a record together, and I can't think of a better way to honor him than to build a stereo Tannoy Dual Concentric system.

I am selling his driver currently, and I already purchased a new set of drivers. I have 2 Lockwood re-coned, and re-coiled hard edge 15" HPD drivers sans dust caps. I'm looking to build 2 300L cabinets and have them soffit mounted (yes I have the room). The soffit mounting will be tricky considering how large a 300L cabinet is, but it affords not just sonic benefits, but cabinet design flexibility.

As of now I am planning on using a MiniHD4x10 as an active digital crossover. This will allow me much flexibility in the setup of the system. I know many of you are gasping in horror, but since my Pro Tools audio interface and monitor controller is digital to begin with, going into that unit via AES makes a lot of sense.

The system will be bi-amped with a Bryston 4B, and a Bryston 3B amp. They are from the same era, approx 1985.

I will probably use a sub woofer with a HP filter to relieve the low driver the stress of frequencies below approx 50hz. This will also make the system a little safer to run loud (which is not my thing, I listen at 85, or at the most 90db on a daily basis).

The advice I'm looking for: general cabinet building advice. I'm planning on using Baltic Birch with a veneer on the front baffle. I need advice on the ports, damping, bracing, box size ratio, etc.

I also need advice on the interface between the amps and the speakers. Do I need to worry about using a zobel, or do I need anything pre driver to protect them since I will not have passive crossovers?

Thanks in advance, and I'm hoping this project will get updated regularly, and with some great pictures.

-Mike
 
Nice drivers. I had both 10" & the 15" HPD's.

I'm not 100% on what you mean by soffits. Over here is means the underside of the roof overhang so I'm guessing its lost in translation :D

As for the box, this thread is about a 360l box for another 15" fullrange. Although its a standard box, it covers most of the bases like bracing etc - http://www.diyaudio.com/forums/full-range/217893-bigun-audio-nirvana-super-15-a.html
 
Thanks for that link. That looks like good reading.

Soffit mounting refers to having the speakers built into the wall of your listening environment so the front plane is flush with, but not actually touching the wall. Many, many studio control rooms have soffit mounted monitors, and many of those have large dual concentric designs as well. Here is a great thread that gets into it.

John Sayers' Recording Studio Design Forum • View topic - Soffit mounting?
 
Ah ok!

It was lost in translation. We get so much spam about double glazing companies about windows, facias, soffits & guttering the other meanings have been washed away.

I was hoping you were going for in wall. Just seemed plain weird to put your nice Tannoys under here :D
 

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With regards to speakers soffit mounting means the same in the UK as in the US btw.

Personally I would use two woofers and make the Tannoys into 3ways like FSM or DMT215s. (tannoy & tannoydmt)
I did something similar with my 12" Tannoys which I cross in at about 175Hz.
This improved midrange clarity quite a bit and also dramatically decreases the cabinet size need for them. Usually the 12"s need 200L cabs but relieved of their bass duty they are quite happy in sealed 46L cabs.
As woofers I use 12" Volt radials. These are truly excellent drivers and on that basis I would recommend 15" Volt RV3863. They reach 29Hz in a 200L cab so you'd still get away with 300L for both Tannoy and Volts.

Having had your Tannoys reconed means that the power capacity will have gone up dramatically to something like 300W as opposed to the 60W they could safely cope with originally. The power limiting factor with the originals was the combination of former and glue rather than the voice coil itself. Contact Lockwood Audio for more details on this.

You will of course need an extra amp and here I suggest MC2 Audio which are very, very good indeed. Personally I very much prefer them to Brystons in every respect.
 
Here are the T/S parameters for HPDs:

tannoy

From what I hear the Lockwood hard-edge conversion is not supposed to change them.
Although I suspect in the case of the measured ones in the link the suspension may have softened over a few decades of use. After the recone they are probably closer to the ones provided by Tannoy. Again I'd contact Lockwood to clear this up.

Oh and a zobel should not be necessary but the tweeter will need some eq to get it flat.
It'll need a notch filter somewhere between 2.5 and 3.5kHz and a 6db/oct boost from around 5 to 6kHz.
Here is a link to the xover schematic so you can work out at which frequency to notch:
http://www.hilberink.nl/codehans/tannoy35.htm
No need to bother working out how deep the notch is as it provides two functions in the passive xover. On the one hand it does the notch on the other it modifies the 6dB slope created by that tiny cap in the hi pass to provide a shelf-like response below 5k down to the xover point.
A few dB is all that is needed. Without the notch you'll get that dreaded horn honk.

I run my 12" analogue active and I get away with a -3dB notch or so. I use a parametric eq to achieve this.
 
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Do you have a set of (reasonable) T/S data for these drivers?

dave

They exist for these drivers on the Tannoy site; I can get them. I've read however that I need to make those measurements of my particular ones. Do you have an opinion on that? Sounds like I should probably start breaking them in since they have new cones/coils. I would imagine that Thiele/Small measurements change once a speaker is broken in? These drivers were in one of the Charisma records studios, so I imagine they saw some use!
 
Charles:

Thanks for the great info. I really appreciate your input. I've thought exactly about doing what you are suggesting with the bass driver. I do own a sub woofer, and know people who run 2 sub woofers, but a bass driver is an interesting concept. 175 is much higher than I had contemplated, but I'm open to suggestions. The beauty of the digital crossover is that I can change my mind at a later date.

I'll send an email to the people at Lockwood on your suggestion. I guess it would be good to let them know where those things ended up.

After reading through the soffit mount threads again over at the Sayers site, I realized that these speakers will have to be up high, and pointed down. Since they are permanent installs this should not be a problem, but it does point to the possibility of building these things in place. It also brings up the possibility of having the box be a non rectangular shape. I'll see if I can post a pic of the wall they would be going into tonight. I was thinking, what's the difference between soffit mounting a speaker to simulate a late baffle, and a speaker mounted to the wall that has a very large baffle. For instance, with the standard 300L cabinet you see posted on the web that people have put these things into, whats the reason the instead of having a 4 ft tall cabinet, why can't you have a 4ft wide cabinet. Just a thought.

One thing is clear, I need to rebuild the front wall of my studio. Better stock up on sawz-all blades.


I hope that guy in the link did NOT soffit mount his Mackies!
If they are the ones I'm thinking about (HR824) they have a large oval passive radiator mounted in the back.

Man I agree. About 15 years ago I used to use those dreaded speakers. They were awful because they just had too much low end that wasn't accurate. Soffit mounting them would be terrible for that reason alone. I don't remember them having a passive radiator. I still have the sub they made for that speaker sitting here idle. It's actually a good piece, and it has a passive radiator in the front, and the 15" bas driver firing into the floor (which I don't love).

I've contemplated using it as the sub for these, or finding a second one and going with a dual sub system.
 
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I've read however that I need to make those measurements of my particular ones. Do you have an opinion on that?

Oh i do... those comments are typically from people who do not yet understand that T/S parameters are not scalars but curves. What numbers you get depend on where you are measuring them. Typical home measurement kit does not very often measure in the same place the industry standard kit does (LMS or LEAP) and the latter typical produce numbers that translate better into the real world results one gets when a box is actually made based on the data.

I am always leary of the numbers, but more often than not start with the factory numbers over anything i measure.

The recones were official factory units?

I would imagine that Thiele/Small measurements change once a speaker is broken in? These drivers were in one of the Charisma records studios, so I imagine they saw some use!

Reconing should well have negated any break-in they ever had.

dave
 
I think the reason people build 4ft tall cabs is because they do not soffit mount them and that way they get the driver to ear height. There is no reason why you couldn't make them wider than tall.
Personally I prefer my speakers above ear height as in most studios.
Oh and Tannoy recommends listening about 15degrees off the central axis and this is how they measured them. I agree as the treble can be somewhat strident directly on axis.
Crossing them at around 175Hz removes a lot of cone movement and thus reduces intermodulation which I think is the reason for the increased midrange clarity.
It is still low enough to not reduce the point-sourciness of my Tannoys.

The Mackies passive radiator is kinda hidden behind the plate amp. It fires through narrow gaps if I remember correctly.
But you're right their bass is too much and quite mushy.
 
Planet,
those hard-edge recones are a Lockwood Audio specialty but then again that is as near as factory as you can get as Lockwood has worked closely with Tannoy for about 50 years now. In my experience they know more about classic and vintage Tannoys than Tannoy themselves these days.
 
They use the Hard edges cuz the earlier ones are NLA and those are cadged from still in production units :)
Dustcap removal/deletion serves No proven purpose.. except to reduce Mfg costs.
WHY? would you even think that these need OR benefit from crossing them at 175 hz? That's is Really Strange.. Mate. First time I've ever heard that one.. After 40 years of owning Tannoys. You invent it all by yourself?
Erm what cone movement ?? Those cones are difficult to see any movement in at all actually
Note ~15 lbs of Alnico does a Fine job of controlling those cones.
Far better than some cheap Sub driver.IMO.
You would have to place a Door slab in front of the typ Tannoys to reduce their single point source 'sound'
 
The Lockwood Audio "Hard Edge"

Hi, Mike!

I'm very intrigued by your refurbished HPDs as described. I also have corresponded with Lockwood Audio regarding replacement of the dreaded rotting foam surrounds with something more durable. Other than their claim that the TS parameters are unchanged, I was able to glean nothing useful (to a DIYer!) from their reply. I'd be very grateful if you could share some details - possibly even a close-up picture or two - about those "Hard Edge" surrounds. (If I'm not mistaken, the previous generation "Gold" had a narrower, pleated fabric surround, while versions prior to that had pleated paper surrounds.) I have been deliberating replacing mine with fabric, but the choice of half-roll (similar to the present foam type) or a pleated style is yet to be made. I suspect the intended enclosure design would play a role in this decision.

As for your plans to soffit mount your speakers, I can give you a big thumbs up on that idea. My primary house speakers (not the Tannoys) are built-in flush just above main-floor ceiling height, projecting into a 2-storey open area, and deliver a very nice sound throughout a large part of the living space on both levels. (Yeah - I'm not a "sweet spot" fan myself - music must be enjoyed while moving/doing!)

- Wilf
 
Hi Bare,
I merely took inspiration from what Tannoy did with their top-of-the-range monitors ie FSM, Buckingham, Dreadnought and 215DMT.
Assuming that you are the same Bare as on the Tannoy Yahoo group I suppose you haven't been reading anything I posted there (albeit under a different name) over the last ten years or so but then that does not particularly surprise me.
Tannoy DCs can quite easily be improved upon by a) running them active and b) removing low bass from their duties.

The magnet size or material does not really do anything to control spurious cone movement. Amplifiers do that as you yourself keep pointing out regularly when you talk about your 20 amp current capabilities and removing the passive xover from between in between makes their job a lot easier in that regard.
And while Tannoy drivers are quite decent when it comes to bass they are not even in the same league as Volts. Describing them as 'cheap subdrivers' is an almost grotesque misrepresentation. And since you seem to have a hang up on magnet size Volt motors make Tannoys offerings look puny in comparison.
Btw the 175Hz came about because that way the drivers are easily still within 1/4 wavelength and so work a single source and it quite fairly shares the load so each part roughly covers roughly 3 octaves.

I love my Tannoys dearly and wouldn't want to be without them but that does not mean that I have to turn into an uncritical fanboy. There is ALWAYS room for improvement as nothing is perfect.
 
They use the Hard edges cuz the earlier ones are NLA and those are cadged from still in production units :)
Dustcap removal/deletion serves No proven purpose.. except to reduce Mfg costs.

I also prefer how they look with no dust cap, and since they serve no purpose, why put one on when you do a re-cone.

Hi, Mike!
I'm very intrigued by your refurbished HPDs as described. I also have corresponded with Lockwood Audio regarding replacement of the dreaded rotting foam surrounds with something more durable. Other than their claim that the TS parameters are unchanged, I was able to glean nothing useful (to a DIYer!) from their reply. I'd be very grateful if you could share some details - possibly even a close-up picture or two - about those "Hard Edge" surrounds. (If I'm not mistaken, the previous generation "Gold" had a narrower, pleated fabric surround, while versions prior to that had pleated paper surrounds.) I have been deliberating replacing mine with fabric, but the choice of half-roll (similar to the present foam type) or a pleated style is yet to be made. I suspect the intended enclosure design would play a role in this decision.

The decision was sort of made for me on these, but the gentleman who sold them to me recommended it. I also like it because it looks a little more like my grand-pop's silver. The durability factor was big since I want my grand kid to get these. I'll post some close up pics of the 2 side by side today.

Hi Bare,
I merely took inspiration from what Tannoy did with their top-of-the-range monitors ie FSM, Buckingham, Dreadnought and 215DMT.

I love my Tannoys dearly and wouldn't want to be without them but that does not mean that I have to turn into an uncritical fanboy. There is ALWAYS room for improvement as nothing is perfect.

I worked at a place that had 215DMTs. I loved them. I actually tried to buy a pair from Germany in the early days of ebay and got ripped off. They never showed up. I can't believe I brought that up, now I feel ill....

Anyway, I'm very much warming to idea of a bass driver built into the cabinet, and not going with a sub-woofer. The engineer who I work with, Bill Ryan, who used to work at Sony in NYC and is now the tech for the band Boston, told me the same thing you have about wanting to relieve the tannoys of having to perform low end duties. He was also the tech at Longview Farms (where I have also worked), and has serviced lot's of main systems running with Golds. I assumed he was talking about frequencies below 80hz, but like I said, with a digital active crossover these are decisions that can be made at a later date.

Boy am I excited. This project is going to up the coolness level of my room exponentially. If I wasn't working on mixes these next 2 weeks I'd get out the sledge hammer and skill saw today.
 
Boy am I excited. This project is going to up the coolness level of my room exponentially. If I wasn't working on mixes these next 2 weeks I'd get out the sledge hammer and skill saw today.

Keep working on those mixes!
You'll have to pay for those woofers somehow and Volt RV3863s cost $550 a pop at Solen. I'd recommend this amp to drive them:
http://www.mc2-audio.co.uk/images/stories/datasheets/sseries/s1400_datasheet.pdf

In fact I would not be surprised if you'd swap your Brystons for the Tannoys as well, finances allowing. They are really, really good!!!

If you want to go really low stick those Volts into a transmission line like PMC XB3s. I've built XB2 copies for my 12" Volts and they are sweet.


PS: Longview Farm looks like a well sexy studio indeed! I couldn't go there because I'd drool over everything (especially the Studer A800) and would thus get booted out in no time!
 
Keep working on those mixes!
You'll have to pay for those woofers somehow and Volt RV3863s cost $550 a pop at Solen. I'd recommend this amp to drive them:
http://www.mc2-audio.co.uk/images/stories/datasheets/sseries/s1400_datasheet.pdf

In fact I would not be surprised if you'd swap your Brystons for the Tannoys as well, finances allowing. They are really, really good!!!

If you want to go really low stick those Volts into a transmission line like PMC XB3s. I've built XB2 copies for my 12" Volts and they are sweet.


PS: Longview Farm looks like a well sexy studio indeed! I couldn't go there because I'd drool over everything (especially the Studer A800) and would thus get booted out in no time!

My budget for the project is 6K, and I really can't go over that. I'm about half way there already with the new drivers, the MiniHD, and a used Bryston 3B I picked up. Rebuilding the front wall will be at least another grand. So, I have a little wiggle room, but not a lot.

Longview was a storied place, and I worked there as a PT editor with Living Colour, Mos Def (for about a day), and then another independent artist I brought in. I didn't spend nearly enough time there. It was a magic place, and I'm very sad it is gone.

I notice those amps have fans, would I need to stick them in a machine room?
 
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