Tannoy Chatsworth - Damp the cabinet or damp the drivers?

[eastone]

On the weekend my First Watt M2 developed a little fault. No big deal and its sorted now.

But in the interim I swopped in an Onkyo AV receiver. 85W with a damping factor of 60 compared to 25W / damping factor 20 of the M2.

My first thought - where's the bass? Second thought - oh, this amp is controlling the bass better than my First Watt.

No it didn't sound as good, but as I am now in possession of some bitumen panels and was about to start trying to damp my lightweight Chatsworth cabinets, a couple of questions arise:

What sort of damping factor is appropriate for Monitor Gold 12" drivers (I've heard 24 mentioned as the magic number)?

If my amp isn't damping the drivers' bass response adequately can damping the cabs make a difference, or is this closing the door after the horse has bolted?

 

[Tony L]

Personally I’d not try to fix an amp mismatch by altering the cabs! Tannoy Monitor Golds date from the transition period from tubes to solid state and the solid state amps available at that time such as the Quad 303, Sugden A21, Leak Stereo 30 etc were a world away from modern highly damped amps. In the UK at least I’m prepared to bet about 80% of Chatsworths sold in the UK would have been partnered with a 33/303. The 303 works very well indeed with Monitor Golds and was the default studio monitoring pairing at the time her in the UK, which is one reason I use one to drive my MG15s.

 

[eastone]

The thing is I'm not 100% convinced that there is an amp mismatch.

The M2 is an attempt to replicate some of the tonal qualities of a SET amp without their limitations vis-a-vis bass damping, ability to handle complex dynamics etc, and should be well within it's comfort zone driving the Golds. It replaced a 405-2 which had been sensitively fettled by Keith Snook, which in turn had replaced a properly serviced 306. I like it a lot and I'm not in a rush to move it on.

I haven't had a 303 here, though it's on my list to try at some point partly on the basis of things I've read here. I understood that bass damping was one of its weakness though?

I don't want to over-damp the speakers. One of the qualities of the M2 is way it achieves a sense of drive without sounding like it has the music is in its grip. I'm just trying to 'tune' the bass response a little. I had figured this could be done by getting the stands right / making small improvements to the cabinet / tweaking the room, but the experience with the Onkyo does have me questioning the amp a little. Maybe my 'holistic' approach to the bass is wrong?

I'll spend the morning looking into the specs of the amps you mention. The M2 is worth reading about I think. Nelson Pass writes in a very lucid style too:

http://www.firstwatt.com/pdf/prod_m2_man.pdf

 

[cooky1257]

Didn't you mention that a previous owner had modified your Chatsworths by porting them?
I'd block the ports and have a listen-not knowing what the cab tuning freq is but bass will drop quickly below that.

 

[Tony L]

The 303 is underdamped in the bass, but 1960s Tannoys (and all similar vintage speakers) were voiced for that kind of amp which is why modern solid state often sounds so wrong (dry, forward and over-tight) with them. ESLs and Klipsch being very similar. The damping needs to be appropriate for the sound to breathe, to have natural ambience etc. If you only listen to loud rock or whatever this may not matter, but you need the right amp to get a natural jazz or classical presentation IME. It is why so many if not most Tannoy users run tube amps. The 303 is a pretty good tube amp impersonator!

 

[eastone]

Didn't you mention that a previous owner had modified your Chatsworths by porting them?
I'd block the ports and have a listen-not knowing what the cab tuning freq is but bass will drop quickly below that.

Yes that's right. It's not a tuned port but a rectangular cutout on the front baffle, with a good deal of BAF wadding providing resistance.

I found the sound a bit closed in when I tried blocking it last time, but I'll definitely revisit this when my new stands arrive.

 

[eastone]

The 303 is underdamped in the bass, but 1960s Tannoys (and all similar vintage speakers) were voiced for that kind of amp which is why modern solid state often sounds so wrong (dry, forward and over-tight) with them. ESLs and Klipsch being very similar. The damping needs to be appropriate for the sound to breathe, to have natural ambience etc. If you only listen to loud rock or whatever this may not matter, but you need the right amp to get a natural jazz or classical presentation IME. It is why so many if not most Tannoy users run tube amps. The 303 is a pretty good tube amp impersonator!

The variety of music being listened to has always been the source of grief with my system. I want clean, extended bass to handle electronic music. But I also want refinement and a live quality for jazz.

The Golds are doing this better than any other speaker I've had to date. I've yet to hear HPDs, but I'm wary of the trade-off between bass extension and sensitivity - presumably the extended bass requires more effort to control?

Still can't find a damping figure for the 303. Did pick up this though on a thread on cap-coupled outputs, from Robert:

"The downside of cap coupled amps is that the damping factor goes to horrible in the low bass, which is bad news with some speakers. With others, it just gives some extra heft and warmth; The same applies to the vast majority of valve amps and for the same reason.

With cap coupled SS today there should be far less of a problem as large value caps are much smaller, better and cheaper than in the 60s and 70s.
I think that the Quad 303 has 2200uf in the speaker line - for the same size you could use 15000uf today and a high enough voltage rating which will maintain the the output impedance to far lower frequencies."

 

[Arkless Electronics]

Forget damping factor. It has nothing to do with the issue. Once DF is up to around 20 there is very little to gain by going higher due to the impedance of the speaker itself being in circuit. Increasing the DF from 20 to 200 would produce only around 5% extra electrical damping!

I like to have at least 50 or so in my own SS designs but for a valve amp even 20 would be a very good DF. AS A HUGE GENERALISATION high DF tends to go with low distortion and wide bandwidth as high negative feedback is mainly responsible for good figures in all these areas.

 

[eastone]

Thought I'd report back with an update on my MG12/First Watt setup.

Last weekend I spent a couple of hours lining the rear and side panels with adhesive bitumen from Wilmslow, underneath the egg-box foam that's there already. I used heavy duty 3.5mm sheet on the rear panels and 1.5mm stuff on the sides. I was concerned about the sound becoming shut-in or muddy, but it had quite the opposite effect. The overall clarity of the image improved dramatically and the bass was starting to have more impact.

This weekend I got the bitumen out again and lined the top and bottom panels, but because I'd run out of the thinner sheet I used the heavy-duty stuff. This turned out to be overkill. The sound became distant and washed-out and the lower bass, while more controlled, felt restricted, as if it had run out of room to breathe.

I then planned to remove the bitumen from the bottom panel, to see if I could work backwards to a happy compromise. But then I remembered the discussion with Tony on the speaker stand thread about unscrewing the back panel a little.

I tried several of variations on this before I had the speakers on proper stands but it hadn't really worked. This time, I removed all the screws in the top half of the panel, then added a little blu-tac strategically to stop any rattling. I'd expected to be fiddling all afternoon but somehow I'd hit it right straight off the bat. Where the bass was stilted it now had a lovely bloom. It seems to flow quite naturally, without sacrificing impact or detail. It's extended and has a lovely 'purring' quality to it, without spilling over or exciting the room.

Overall, the in-room balance seems to be broadly correct as I'm mostly using the crossover controls at level or sometimes with 'treble energy' at minus 1, which chimes with how most people here seem to use theirs. So for now I'm going to sit on my hands and just enjoy what I have. I may in the new year think about refreshing the electrolytics in the crossover but until then, no more fiddling. Oh, except to fit some nice new oatmeal grill cloth.

** Incidentally, I went to Spiritland this weekend and heard their Definitive Audio horns being driven by some huge Canary Audio 300B Monoblocks. This was actually the first time I've heard 300Bs and it's great to have a mental reference for the sort of sound Nelson Pass was thinking about when he developed the M2, and from which to evaluate the quality of bass in my system.

 

[Tony L]

I remain convinced the reason I like vintage screwed baffle & back panel speakers is that they don’t behave like drums the way normal glued boxes do. The panels need to be tight enough not to rattle, but not tight enough to hold a pitch/note. I am certain this is the reason I like BBC speakers, vintage Tannoys etc so much as the cabinets are nice and low mass but without obvious resonance. The only way to get resnance out of modern glued MDF cabs seems to be excess mass, or excess bracing, and that tends to sound dead/awful to my ears. I can think of very few if any really heavy speakers I like.

PS I have the back doors of my Lockwoods done up finger-tight, no more. Tapping them just gives a dead thud, no note.

PPS Pay attention to how tight the driver is attached to the front baffle too. Hint: tight is bad!

 

[lexi]

I remain convinced the reason I like vintage screwed baffle & back panel speakers is that they don’t behave like drums the way normal glued boxes do. The panels need to be tight enough not to rattle, but not tight enough to hold a pitch/note. I am certain this is the reason I like BBC speakers, vintage Tannoys etc so much as the cabinets are nice and low mass but without obvious resonance. The only way to get resnance out of modern glued MDF cabs seems to be excess mass, or excess bracing, and that tends to sound dead/awful to my ears. I can think of very few if any really heavy speakers I like.

PS I have the back doors of my Lockwoods done up finger-tight, no more. Tapping them just gives a dead thud, no note.

PPS Pay attention to how tight the driver is attached to the front baffle too. Hint: tight is bad!

Years ago many reviewers and listeners seemed to regard Tannoy as "coloured". Was it cabinet colouration they meant, as you kind of describe your cabs as "live".
Lots of the Kef/Spendor/ ESL type guys never gave Tannoy a look at that time. I am sure some will remember that. In fact Tannoy cabs were not great at the start.

 

[JensenHealey]

On the weekend my First Watt M2 developed a little fault. No big deal and its sorted now.

But in the interim I swopped in an Onkyo AV receiver. 85W with a damping factor of 60 compared to 25W / damping factor 20 of the M2.

My first thought - where's the bass? Second thought - oh, this amp is controlling the bass better than my First Watt.

No it didn't sound as good, but as I am now in possession of some bitumen panels and was about to start trying to damp my lightweight Chatsworth cabinets, a couple of questions arise:

What sort of damping factor is appropriate for Monitor Gold 12" drivers (I've heard 24 mentioned as the magic number)?

If my amp isn't damping the drivers' bass response adequately can damping the cabs make a difference, or is this closing the door after the horse has bolted?

Damping factor as mentioned in connection with amplifiers is NOT the same as mechanical damping of a cabinet or drivers - similar names for entirely different things!

 

[cooky1257]

Early Tannoy cabs were pretty shocking really-some like the colouration which is undoubtably part of their charm for some audiophiles. I definitely would never describe Lockwoods as light though-they weigh 80kg each and are really well put together.

 

[Tony L]

Depends which cabs! The better Tannoy cabs (Autographs, GRFs, Canterburys, Yorks) in their corner format are damn good and very sought-after.

I’d argue Lockwoods qualified as ‘thin wall’ as the plywood panels and baffle are pretty thin, though the screwed assembly and Formica finish is exeptionally good at damping them without adding huge amounts of mass the way so many modern MDF cabs are built. They are different to BBC cabs in many ways, but logically seem to be barking up the same tree.

PS Everything I write about anything needs to be read in the light that I have zero interest in ear-splitting rock volume levels; my idea of a great speaker is one that sounds open, natural and real on acoustic/classical instruments at moderate (say 75-80db average) levels. Everything I love may resonate at much higher volume, I have no idea as I’d just not want to be in a room with it! What gives me a natural bloom and heft to the sound may turn to boom, resonance or whatever at crazy levels.

 

[cooky1257]

Tony, I'd argue 3/4 laminated and braced ply isn't 'thin wall' but we've been here before ;-)
Any of the rear loaded horns will be (should be) rigid given the nature of the design and the actual drawings for the early Canterbury and York call for panel bracing that is often missing, the rectangular York for example had a full width shelf, mid panel braces and a sub baffle-again, missing-that's why I used the word shocking. In the Tannoy construction guides for corner York, Lansdowne and Canterbury they say "The cabinets should be glued and screwed at all joints, corner blocks and braces should be included to ensure absolute rigidity, the thickness of timber employed should not be less than 3/4 inch ". Interestingly for the smaller Lancaster the minimum is 1/2 inch. The Lockwoods are 3/4" and are laminated ply- you only have to look inside to see just how substantial they are.

 

[eastone]

Damping factor as mentioned in connection with amplifiers is NOT the same as mechanical damping of a cabinet or drivers - similar names for entirely different things!

Yes, it's become quite clear having improved on the cabinets a little that there are no issues with the amplifier controlling the cones.

This was also underscored by the system at Spititland which had a definite padded quality to the bass, but retained control. (The M2 is designed with reference to the sound of SET amps)

 

[eastone]

Cooky, as you understand the theory behind damping cabinets and I am merely flying by the seat of my pants, are you able to say anything tecnical about the effect of lining with bitumen as I have done?

I took the idea from a blog article by Keith Snook on refurbishing a pair of Eatons, and while I think I understand the physics / acoustics on a basic level the effect of damping on driver performance is beyond my ken.

 

[cooky1257]

I couldn't specifically comment as I have no idea what is going on with your modified Chatsworths re the bass tunings. I didn't 'get' how merely increasing the thickness of the bitumen pads could have such a negative effect as you described-I dont doubt your experience!. Bitumen will tend to lower the amplitude of any resonances in a panel and the extra mass in the thicker bitumen just didn't seem like enough to shift resonance upwards... Stiffening the panel with bracing or increasing panel mass generally will shift those resonances higher in frequency. One school of thought then damps the braced panels-Berkeley and Ardens do this. Whenever I brace an enclosure I use mastic type adhesives that dont ever really set hard and I generally follow the Tannoy DMT method of cab construction-the back of the driver is coupled to the internal bracing with a wedge of mastic putty and the (chip board)bracing to panels features lossy mastic glue. Front and rear panels are 36mm thick mdf, top and sides are laminated 18mm mdf.
There's more than one way to skin this cat!
The important thing in your case is whatever you've done is giving you what you need/better to listen to and you cant argue with that. BTW introducing leaks into a ported enclosure with totally mess up the tuning so by all means loosen the screws if you like the effect but make sure theres still good seal.

 

[eastone]

BTW introducing leaks into a ported enclosure with totally mess up the tuning so by all means loosen the screws if you like the effect but make sure theres still good seal.

Is this still the case with a resistive vent? It's really just a 10"x1.5" slot cut into the front baffle. It's covered internally with a thin black cloth and behind that there's BAF wadding that fills the lower half of the cabinet.

 

[cooky1257]

Is this still the case with a resistive vent? It's really just a 10"x1.5" slot cut into the front baffle. It's covered internally with a thin black cloth and behind that there's BAF wadding that fills the lower half of the cabinet.

Well assuming the resistive vent has been calculated for a given cabinet volume then introducing another ‘leak’ must surely change those calculations ie you are effectively randomly changing the size of the slot/introducing another very long narrow slot.Goodmans made a similar enclosure called the Axiom...http://diyaudioprojects.com/Technic...ize-with-Better-Low-Frequency-Performance.pdf