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Old 19th December 2006, 08:57 AM   #1
GraemeC is offline GraemeC  Australia
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Default 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
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Old 19th December 2006, 09:05 AM   #2
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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!
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Old 19th December 2006, 09:19 AM   #3
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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
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Old 19th December 2006, 10:23 AM   #4
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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.
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Old 20th December 2006, 07:31 AM   #5
GraemeC is offline GraemeC  Australia
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Question Improving Tannoy HPD15's

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
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Old 20th December 2006, 08:51 AM   #6
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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.
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Old 20th December 2006, 08:53 AM   #7
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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
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Old 20th December 2006, 09:00 AM   #8
AndrewT is online now AndrewT  Scotland
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Hi,
what size are your HPDs?

10inch, 12inch, or 15inch?
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Old 20th December 2006, 12:28 PM   #9
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Default 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...
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Old 20th December 2006, 12:31 PM   #10
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This thread seems to have appeared twice
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