Enhancing Tannoy HPD15's
Hi All
This is my first post so please be kind. I admit that I know little to nothing of the theory of audio but I do like good sound.
I have a thirty year old pair of Tannoy HPD15, bought new for 99 pounds, housed in 85 litre flat topped pyramid boxes. Recently I renewed the foam rubber surrounds and that improved the sound radically; it was a little muddy.
What can I do to further improve the sound?
Larger boxes are not an option - WAF.
I have variously been advised to:
*** Add a supertweeter to each box,
*** Add a single subwoofer,
*** Improve the existing passive crossover, or
*** Buy two stereo valve amplifiers and use them as active crossovers.
Any ideas. What will give me the best return for effort, or should I just lay back and enjoy the music?
Cheers
Graeme
Hi All
This is my first post so please be kind. I admit that I know little to nothing of the theory of audio but I do like good sound.
I have a thirty year old pair of Tannoy HPD15, bought new for 99 pounds, housed in 85 litre flat topped pyramid boxes. Recently I renewed the foam rubber surrounds and that improved the sound radically; it was a little muddy.
What can I do to further improve the sound?
Larger boxes are not an option - WAF.
I have variously been advised to:
*** Add a supertweeter to each box,
*** Add a single subwoofer,
*** Improve the existing passive crossover, or
*** Buy two stereo valve amplifiers and use them as active crossovers.
Any ideas. What will give me the best return for effort, or should I just lay back and enjoy the music?
Cheers
Graeme
Hi Graeme, and welcome to diyAudio!
So you're not happy. Fair enough. But by the sound of things, you don't know why you're not happy, as all those tweaks will have different effects. So my suggestion: Download Arta, Speaker Workshop, or one of the other measurement suites out there, and measure your speakers, both frequency response in the box, and Theile Small parameters. Then you will have a sound, (pun intended!), base on which to work. Good luck!
So you're not happy. Fair enough. But by the sound of things, you don't know why you're not happy, as all those tweaks will have different effects. So my suggestion: Download Arta, Speaker Workshop, or one of the other measurement suites out there, and measure your speakers, both frequency response in the box, and Theile Small parameters. Then you will have a sound, (pun intended!), base on which to work. Good luck!
mmmm apart from a bigger box ( much bigger and deeper bass), I would mount them flush into your walls.
The finest tannoy 15 inch duel concentric, I have heard was mounted into the former window frames of a house that had been enlarged, infinite baffle style, They sounded well perfect.
They were first installed in the 1950's, and are still enjoyed today.
I wish I had some
The finest tannoy 15 inch duel concentric, I have heard was mounted into the former window frames of a house that had been enlarged, infinite baffle style, They sounded well perfect.
They were first installed in the 1950's, and are still enjoyed today.
I wish I had some
Did you get the original labels? It would be interesting to know if I tested them (though they sound a bit young for that)
One of the chief problems at that epoch was that rather strange crossover, using the auto-tapped choke as a step-up transformer, to match the impedances of the HF diaphragm to the bass cone, with the series resistor with parallel capacitor boosting the ultra highs (or rather attenuating the mid highs), leaving the diaphragm with no damping factor in the critical voice region. In '71, with the aid of the lab boys, I biamped my pair of 12" concentrics, bodging together the crossover by ear, calculation and measurement (it was good to have an anecoic chamber and the B&K gear to confirm one's feelings) and they sounded a whole lot better than before, particularly in transient clarity. I remember the HF roll off as a mixture of a third order and a first order coming in much higher, and the lowpass being a straight first order, but there's no way I could remember the values, and those speakers stopped travelling with me more than twenty years ago.
One of the chief problems at that epoch was that rather strange crossover, using the auto-tapped choke as a step-up transformer, to match the impedances of the HF diaphragm to the bass cone, with the series resistor with parallel capacitor boosting the ultra highs (or rather attenuating the mid highs), leaving the diaphragm with no damping factor in the critical voice region. In '71, with the aid of the lab boys, I biamped my pair of 12" concentrics, bodging together the crossover by ear, calculation and measurement (it was good to have an anecoic chamber and the B&K gear to confirm one's feelings) and they sounded a whole lot better than before, particularly in transient clarity. I remember the HF roll off as a mixture of a third order and a first order coming in much higher, and the lowpass being a straight first order, but there's no way I could remember the values, and those speakers stopped travelling with me more than twenty years ago.
Hi All
This is my first post so please be kind. My audio theory is quite limited although I am reasonably handy with tools.
In 1975 I bought a pair of Tannoy HPD15s in London for £99 and then made a pair of MDF boxes for them. The enclosures are flat topped pyramid shape and about 85 liters net capacity and were not vented.
Six months ago I noticed the sound had got a bit muddy – the speakers are 30 years old! – and I noted that the foam surrounds had deteriorated. I decided to replace the drivers and discovered that Tannoy no longer sell components, that their stuff was now exorbitantly expensive and that it was possible to replace the surrounds. I bought a kit and refoamed my speakers.
During this investigation process I discovered that after I built my enclosures Thiel and Small had quantified much of the physics of audio design. A big improvement on the old rules of thumb. I ran my speaker and driver specifications thru WinISD and learned that I would get better bass if I ported the enclosures. So I added two vents to the bottom of the boxes. They now sound quite good provided that I keep then about 3 ft from the corners of the room. If they are against the walls the bass goes thin.
Now I am enthusiastic about further improving the sound quality and am looking for considered suggestions.
Replica autograph or westminster compound horns would be great but unfortunately are too big for my living room – about 3,000 cubic feet (or 85 m3). The current boxes are about as large as acceptable.
Other suggestions are to add supertweeters, a subwoofer, enhance the crossovers, or to biamp each speaker. What should give me the best return for my effort??
My other equipment is a Yamaha CR1000 receiver/amplifier, Yamaha CD player and Loewe DVD player.
I look forward to all constructive suggestions.
Graeme
This is my first post so please be kind. My audio theory is quite limited although I am reasonably handy with tools.
In 1975 I bought a pair of Tannoy HPD15s in London for £99 and then made a pair of MDF boxes for them. The enclosures are flat topped pyramid shape and about 85 liters net capacity and were not vented.
Six months ago I noticed the sound had got a bit muddy – the speakers are 30 years old! – and I noted that the foam surrounds had deteriorated. I decided to replace the drivers and discovered that Tannoy no longer sell components, that their stuff was now exorbitantly expensive and that it was possible to replace the surrounds. I bought a kit and refoamed my speakers.
During this investigation process I discovered that after I built my enclosures Thiel and Small had quantified much of the physics of audio design. A big improvement on the old rules of thumb. I ran my speaker and driver specifications thru WinISD and learned that I would get better bass if I ported the enclosures. So I added two vents to the bottom of the boxes. They now sound quite good provided that I keep then about 3 ft from the corners of the room. If they are against the walls the bass goes thin.
Now I am enthusiastic about further improving the sound quality and am looking for considered suggestions.
Replica autograph or westminster compound horns would be great but unfortunately are too big for my living room – about 3,000 cubic feet (or 85 m3). The current boxes are about as large as acceptable.
Other suggestions are to add supertweeters, a subwoofer, enhance the crossovers, or to biamp each speaker. What should give me the best return for my effort??
My other equipment is a Yamaha CR1000 receiver/amplifier, Yamaha CD player and Loewe DVD player.
I look forward to all constructive suggestions.
Graeme
I'm not sure if this link relates to your speakers, but it might be worth a try.
http://members.aol.com/emigrant/tannoy_waf_15.htm
If you have the Thiele-Small parameters, then your half way to a great sounding speaker.
http://members.aol.com/emigrant/tannoy_waf_15.htm
If you have the Thiele-Small parameters, then your half way to a great sounding speaker.
Hmm, HPD15s. Much under-rated drivers IMO. Problem with Tannoys though, as you've discovered, is that they are a case where bigger is better! I'll get my thinking cap on and see if I can come up with anything. BTW -you're existing cabinets sound like huge Metronomes to me -see the thread here if you're interested. Good plan. I'm surprised they go bass light when placed near a wall though -normally that has the opposite effect due to increased room-gain.
Scott
Scott
Crossover
Sounds like you may be the man to speak to Chris.....
I have the crossover specs but have not got the feintest idea how to swap out the component that has multiple outputs (you called it an autotransformer).
The cabs you have Graeme sound like they could be fairly sturdy but you could stick them in a reproduction Berkerly or Arden box.
Try http://www.hilberink.nl/speaker.htm for loads of alternative cab ideas.
And most importantly listen to the guys here. If you take the collective knowledge, experience, expertise and love of HiFi from the members here we rule the audio world...
Sounds like you may be the man to speak to Chris.....
I have the crossover specs but have not got the feintest idea how to swap out the component that has multiple outputs (you called it an autotransformer).
The cabs you have Graeme sound like they could be fairly sturdy but you could stick them in a reproduction Berkerly or Arden box.
Try http://www.hilberink.nl/speaker.htm for loads of alternative cab ideas.
And most importantly listen to the guys here. If you take the collective knowledge, experience, expertise and love of HiFi from the members here we rule the audio world...
Careful with that link in post6.
The newer speaker looks like it has the tulip waveguide rather than the pepper pot that is part of the HPD series and all before them.
The crossover has no autoformer and there is no notch, nor slope built into the treble section of the crossover. All these omisssions make the installation unsuitable for an HPD.
The newer speaker looks like it has the tulip waveguide rather than the pepper pot that is part of the HPD series and all before them.
The crossover has no autoformer and there is no notch, nor slope built into the treble section of the crossover. All these omisssions make the installation unsuitable for an HPD.
Thanks everyone for your considered responses.
First I would like to apologise for posting twice. I am new to this and after my first post I got what I thought was an error message and I believed that that post had disappeared into the ether. So I erroneously posted again.
Pinkmouse. Six months ago I was walking past an audio store and noticed their demonstrator was producing much more detail than my stereo was then producing. I just assumed that the drivers were worn out after thirty years and decided to replace them, and so my web searching started.
I discovered Thiele and Small, diyaudio, WinISD and others. I bought a foam surround replacement kit – the old surrounds were tacky and fell to pieces in my hand and replaced one surround only and listened to the results. That speaker was much better than the other. Thiele and Small parameters were downloaded from thielesmall.com and plugged into WinISD, adjusted for the size of my enclosures, and this indicated that I would get better bass with two 85mm vents. So I replaced the second foam surround and simultaneously put in the two vents and listened to the results. The vented speaker sounded better than the unvented one, IMHO. So I vented the other.
Its going a little too far to say that I am unhappy with my set up. They sound good, and are better than any of my friends. However, I was surprised by the improvement from refoaming and venting, and am exploring the issue as to whether I can get further worthwhile enhancements. The answer might be to leave well alone.
I downloaded Arta and feel overwhelmed by the physics in the first six pages of the manual. Will try and wade through it.
Cameron. My house walls, both external and interior, are double brick and my house is heritage classified. If I start cutting holes in the walls I will have issues with the Heritage Commission, National Trust, local council and the busy-body lady two doors down…. I’d like to hear the infinite baffles tho’.
Chrispenycate. My speakers are very neatly signed on the connector panels “Inspected by D R Andrew”. Rick Norrish in Adelaide recommends improving the crossover hardware, which seems consistent with your view. How would you rate this approach versus biamping?
BobHayes. Thanks for the link; I do have the TS parameters.
Scottmoose. Will look forward to your considerations. My living room has bay windows in an alcove and the speakers sound best, IMHO, when placed on the 270° corners near the windows rater than back in the 90° corners, if this makes sense.
They are more like very squat Metronomes – only 2’ high.
JRKO. My cabinets were developed from the Berkely drawings that came with the speakers. Someone told me that I would avoid/minimise standing waves (I think) by having non-parallel walls so I changed the shape to the flat topped pyramids. Berkeleys are 98 liter and I think mine are around 85 litres. MDF comes in 8x4 foot (1200x2400mm) sheets; I cut it down the middle so each side is 2’ high; used all the MDF and they finished up around 85 l – but they didn’t teach flat topped pyramids in high school trigonometry so the volume estimate is very approximate.
Thanks for link, but several attempts to connect were not successful.
Andrew. Thanks for the warning.
Conclusion. Sorry for such a lengthy post but a lot of interesting issues were raised.
As you can gather from my comments, I am very much a novice in this area and my strategy is to listen to, question, debate and analyse the opinions of enthusiasts who know much more than me.
For domestic harmony reasons I cannot enlarge the boxes much, so I am basically looking for alternative strategies.
Please keep the ideas flowing.
First I would like to apologise for posting twice. I am new to this and after my first post I got what I thought was an error message and I believed that that post had disappeared into the ether. So I erroneously posted again.
Pinkmouse. Six months ago I was walking past an audio store and noticed their demonstrator was producing much more detail than my stereo was then producing. I just assumed that the drivers were worn out after thirty years and decided to replace them, and so my web searching started.
I discovered Thiele and Small, diyaudio, WinISD and others. I bought a foam surround replacement kit – the old surrounds were tacky and fell to pieces in my hand and replaced one surround only and listened to the results. That speaker was much better than the other. Thiele and Small parameters were downloaded from thielesmall.com and plugged into WinISD, adjusted for the size of my enclosures, and this indicated that I would get better bass with two 85mm vents. So I replaced the second foam surround and simultaneously put in the two vents and listened to the results. The vented speaker sounded better than the unvented one, IMHO. So I vented the other.
Its going a little too far to say that I am unhappy with my set up. They sound good, and are better than any of my friends. However, I was surprised by the improvement from refoaming and venting, and am exploring the issue as to whether I can get further worthwhile enhancements. The answer might be to leave well alone.
I downloaded Arta and feel overwhelmed by the physics in the first six pages of the manual. Will try and wade through it.
Cameron. My house walls, both external and interior, are double brick and my house is heritage classified. If I start cutting holes in the walls I will have issues with the Heritage Commission, National Trust, local council and the busy-body lady two doors down…. I’d like to hear the infinite baffles tho’.
Chrispenycate. My speakers are very neatly signed on the connector panels “Inspected by D R Andrew”. Rick Norrish in Adelaide recommends improving the crossover hardware, which seems consistent with your view. How would you rate this approach versus biamping?
BobHayes. Thanks for the link; I do have the TS parameters.
Scottmoose. Will look forward to your considerations. My living room has bay windows in an alcove and the speakers sound best, IMHO, when placed on the 270° corners near the windows rater than back in the 90° corners, if this makes sense.
They are more like very squat Metronomes – only 2’ high.
JRKO. My cabinets were developed from the Berkely drawings that came with the speakers. Someone told me that I would avoid/minimise standing waves (I think) by having non-parallel walls so I changed the shape to the flat topped pyramids. Berkeleys are 98 liter and I think mine are around 85 litres. MDF comes in 8x4 foot (1200x2400mm) sheets; I cut it down the middle so each side is 2’ high; used all the MDF and they finished up around 85 l – but they didn’t teach flat topped pyramids in high school trigonometry so the volume estimate is very approximate.
Thanks for link, but several attempts to connect were not successful.
Andrew. Thanks for the warning.
Conclusion. Sorry for such a lengthy post but a lot of interesting issues were raised.
As you can gather from my comments, I am very much a novice in this area and my strategy is to listen to, question, debate and analyse the opinions of enthusiasts who know much more than me.
For domestic harmony reasons I cannot enlarge the boxes much, so I am basically looking for alternative strategies.
Please keep the ideas flowing.
Do you have the Qts value for your drivers? The problem with the old Tannoys is the relatively high value of this parameter meaning you need a big enclosure. You could use a negative output resistance amplifier to lower the Q value to match it to your enclosures. I have been looking for a pair of Tannoys to try this technique out but they go for silly money on E-bay!
How easy was fitting the new surrounds? This may have effected the other parameters Fs and Vas
How easy was fitting the new surrounds? This may have effected the other parameters Fs and Vas
Hi Consort,
have you got it the right way round?
Tannoy Dual Concentrics have a low Q and added resistance from the amp (Zout) or from a series resistor whether as part of the inductor or separate raises the Q.
The effect of the raised Q is that a slightly smaller cabinet can be used for the same turn-over frequency. Alternatively the same cabinet size can be used but the depth of the "low Q shelf" is reduced to make the response nearer to flat.
have you got it the right way round?
Tannoy Dual Concentrics have a low Q and added resistance from the amp (Zout) or from a series resistor whether as part of the inductor or separate raises the Q.
The effect of the raised Q is that a slightly smaller cabinet can be used for the same turn-over frequency. Alternatively the same cabinet size can be used but the depth of the "low Q shelf" is reduced to make the response nearer to flat.
Sorry for the oversight Andrew; I got my inches and metrics confused. They are 15 inch Tannoy HPD385's.
I certainly do not want to start a really big project as I do not have the knowledge base to do that. That's why I am seeking guidance as to my options and likely benefits.
Also I did not know that one could "do both". Perhaps you could explain in a little more detail.
Consort. The TS parameters for the HPD385 obtained from www.thielesmall.com are: Qts = 0.18, Vas = 483 litres, Fs = 22.00 Hz and I have the other parameters if you want them. Naturally I do not know if my drivers vary from these specifications.
It was really easy replacing the foam surrounds. I bought a kit from www.speakerbits.com.au in Melbourne, Australia - instructions are on their website and they include a copy with the kit and are really helpful on the phone. The first one took about an hour, of which 50 minutes was my learning time. The second took less than half an hour, mainly waiting for the glue and 'stiffener solution' to dry between tasks.
JRKO. I will keep posting my activities. Its just fair to let those helping know what's happening from the advice, and if it also helps others then that's great.
Wishing everyone all the best for the festive season,
Cheers
Graeme
I certainly do not want to start a really big project as I do not have the knowledge base to do that. That's why I am seeking guidance as to my options and likely benefits.
Also I did not know that one could "do both". Perhaps you could explain in a little more detail.
Consort. The TS parameters for the HPD385 obtained from www.thielesmall.com are: Qts = 0.18, Vas = 483 litres, Fs = 22.00 Hz and I have the other parameters if you want them. Naturally I do not know if my drivers vary from these specifications.
It was really easy replacing the foam surrounds. I bought a kit from www.speakerbits.com.au in Melbourne, Australia - instructions are on their website and they include a copy with the kit and are really helpful on the phone. The first one took about an hour, of which 50 minutes was my learning time. The second took less than half an hour, mainly waiting for the glue and 'stiffener solution' to dry between tasks.
JRKO. I will keep posting my activities. Its just fair to let those helping know what's happening from the advice, and if it also helps others then that's great.
Wishing everyone all the best for the festive season,
Cheers
Graeme
Andrew- You are right about the Qts value. I have seen Tannoys with relatively high Qts value but they seem to be in the minority so I would have to be careful in my selection to apply the negative resistance idea.
In general though a low Qts value gives a smaller vented enclosure size. I tried a quick run in Unibox which for Graeme's enclosure and specified parameters gave a flat response down to 45Hz with a 14 cm dia port 15cm long for a box tuning freq of 46Hz.
Seasons greetings
In general though a low Qts value gives a smaller vented enclosure size. I tried a quick run in Unibox which for Graeme's enclosure and specified parameters gave a flat response down to 45Hz with a 14 cm dia port 15cm long for a box tuning freq of 46Hz.
Seasons greetings
GraemeC said:
almost says it all.
The HPD crossover has all the treble part at one end and all the bass part at the other end.
The single inputs are (from memory) near the middle. You can intercept the input tracks and cut one of them so that the bass is fed from the standard input cables and solder in a new connection that feeds the treble half of the crossover. The split crossover allows bi-wiring or bi-amplification. A pair of stereo power amps with very short cables can now drive each dual concentric.
Connect a single channel of power amp to each of the treble and bass halves of the split crossover and you have bi-amped the speaker.
This combination transformed my Berkleys for the better. I never went down the road of upgrading the lower quality components. That will probably come soon.
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