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Tannoy HPD 315 Questions

Discussion in 'classic' started by jonathanmorbin, Oct 15, 2020.

  1. So I've been asked to look at a pair of Tannoy 315's for someone who wants to restore them as best as possible for studio use.

    They have been placed in what looks like unfinished rectangular GRF cabinets from my research, well made by the looks of it but still bare wood. about 120 litres. The complaints i have had are "lacking of low end" and "quite harsh sounding"

    Now im only just learning about the world of Tannoy GPD's so my knowledge is not great.

    What i have found is that there is a fairly big mismatch on the HF which i think is due to the fact that it has one copper tweeter and one aluminium tweeter. The copper being the brighter one especially in the 10k-12k region. But there also seems to be a mismatch in the LF too, the low is fairly well matched but in the mids one seems to be slightly louder. The crossovers seem to be ok and ive re-capped them with new capacitors.

    any advice would be grateful in regards to getting them back to spec. Im presuming two new tweeters from lockwood and maybe one re-cone? is there a second hand market anywhere i am not aware of?

    Im not sure these are the best type of cabinets after reading a few posts around the place, would these be better suited in another cabinet in regards to having a better low end response? And lastly in terms of coupling do these speakers ideally need to be on the floor, they are currently on homemade wooden stands to get them up above the mixing desk so im wandering if that is also a contributor to the weaker low end?
  2. Tony L

    Tony L Administrator

    Very hard to assess anything without seeing what you have. Stick some pictures up (details in the FAQ in the reference area as to how to link). You really have me confused with the different tweeter thing. For a start the aren’t a ‘tweeter’ as such, it’s a compression driver/horn, and unless you know the workings of Tannoys well if you have got as far as seeing them you may even have damaged or misaligned things. Images will help explain a lot. They are an aluminium diaphragm. Likewise with the crossovers, there are all manner of third-party abominations passed off as Tannoy crossovers from the budget to the blingy & boutique, so we should first establish what you have and if it is appropriate for the driver in question. Then we can advise on the condition of the cones/foam surrounds. There are a few here who really know Tannoys well so I’m sure you’ll get some good advice, but we do need to establish exactly what you have first.
  3. calorgas

    calorgas Ratty bumpkin

    Maybe the copper vs aluminium is the colour of the tweeter horn / throat (?) - on some models it was coppery or gold coloured, though never HPD's afaik. I think maybe 3149 have gold coloured ones if I remember rightly.
    Last edited: Oct 15, 2020
  4. Vinny

    Vinny pfm Member

    I have a partially dismantled HPD 315 here and the description is either very poor, or the OP hasn't got an HPD.

    Obviously, at first sight they look like a standard woofer, complete with a very open-weave dust cover in the centre. If well lit you may be able to make out under the dust-cover, the machined tube that is, in effect, the tweeter, and that is aluminium or an aluminium alloy, so matt grey.

    Reminder to self - get the ****ing things sorted and off for reconing....
  5. Sorry for the poor description, i mean the HF diaphragms. One of them the coil is red in colour and the other is a grey colour. I haven't got pictures of them at the moment as they are back in the speakers. Im having issues posting photos at the moment through Flickr, it keeps thinking im spam or that my post has wrong elements in it.
  6. Tony L

    Tony L Administrator

    Ah, sorry about that, that issue will go after a couple more posts (it is an anti-spam tool to stop spam-bots dropping a payload, it goes away after a few posts).
  7. Ah ok no worries i shall make a few more posts and try again.....
  8. Tony L

    Tony L Administrator

    Cool. They look promising. Hopefully Frank (Cooky) and others will turn up as HPDs aren’t really my area, though other than the crossovers having been recapped/altered I’m not seeing anything obviously wrong visually at this stage. I’d personally dismantle the crossovers and check every single value against a schematic and photo evidence of untouched units, don’t assume they have been done right! They do look like the right type for the drivers though, so whatever was done can be fixed if it is not right.
  9. Ok that’s good news! It was myself that recapped them and also new resistors. They match the schematic I found online and I have the original parts still. I’ve tested them with my frequency analyser and they both look like they are outputting correctly.
  10. Tony L

    Tony L Administrator

    Excellent. Try getting an impedance reading of the two drivers with a multi-meter with the crossover disconnected, on the 4 pin socket on the driver basket the two narrowly spaced holes are one driver, the wider the other, though I can’t off the top of my head remember which is which! If HPDs are anything like Golds the compression horn should IIRC be around 10 Ohms, the bass unit around 6 Ohms, though that may be different as they are different speaker designs. Obviously they should be very similar left to right, so it will hopefully help highlight any obvious issue with the voice-coils.
  11. HF is 10ohm (aluminium/grey) and 9.5ohm (copper/red)
    LF is 5.3ohm and 5.3ohm
  12. Tony L

    Tony L Administrator

    I’m still puzzled by the aluminium vs. copper HF voice coil, hopefully others can shed life on this. All my experience is with Monitor Golds (I’ve owned three pairs of 15”). There are others here with far wider Tannoy experience than me. For reference here is a Monitor Gold HF unit:


    This is an early-style one with the removable back, so different to the bakelite-back type found in HPDs. It has the grey aluminium or whatever voice coil. All Golds I’ve seen have been like this. With Golds aligning the voice coil in the gap, the number of paper spacers and the tension of the four bolts is hugely, hugely critical, you really can make or break the speaker with minuscule differences and it took me hours to get them where I was really happy. HPDs are alleged to be far less critical than Silvers, Reds, or Golds, but as stated I’ve never fiddled with a pair so I’m just not the right person to ask. Even if they are allegedly ‘plug and play’ do pay attention to the bolt tightness, they shouldn’t be tight at all, just gently nudged up and then held with a drop of paint or whatever. Always listen as you do it, you will hear when it sounds its most open, clean and dynamic. Do them too tight and the treble gets pretty horrible fast. FWIW I got this straight from Roger at Lockwood so it isn’t just my experience. I’m certain a lot of DIY Tannoy projects sound as bad as they do due to misaligned or over-tightened compression horns. Over-tightening the driver basket to the cabinet is a bad move sonically too.
  13. Vinny

    Vinny pfm Member

    Somebody fitted the wrong HF voice-coil to one of them?

    If nothing else they are very likely to be different as they stand, and hence wrong.

    FWIW, the grey is unlikely to be aluminium as aluminium corrodes far too easily and quickly, especially as a wire. But never say never.
  14. I was told aluminium and Copper by someone at Lockwood the other day. All I know for sure is they are both different. One looks just like in that picture, the other is red in colour Where that one is white/grey. I’ll take some pictures tomorrow so you can see what I mean. Both have an amount of Paper spacers installed and the bolts are only hand tight. I wouldn’t be surprised if there is some alignment issues, I haven’t yet looked in to that yet.
  15. Vinny

    Vinny pfm Member

    Probably an aluminium alloy???????? Strange choice, but Tannoy knew better than very well what they were doing.
    So, it looks like one voice-coil is wrong, or, if they fitted both to HPD's, you are using grossly unmatched ones, possibly, probably.

    Simple physics - forces on a wire carrying current in a magnetic field - would say that the different wire and half an ohm would make negligible difference, but that is theory and the speakers are real world.

    This needs comment from Mr. Frank Tannoy - @cooky1257

    What are the serial nos.?
  16. cooky1257

    cooky1257 pfm Member

    Looking at those enclosures I'm not surprised there's no bottom end, you cannot scale a horn down and expect the same LF performance I'm not surprised the bass mids are prominent. I suggest Balmoral size/ style bass reflex 120L tuned to 32 hz
    The difference in hf coils is just one of date of issue, I've seen both grey and red lacquer coated versions of the 205 in HPDs. If they both have paper washers they are 205's, someone may have installed a 105 hf diaphragm from the later k- series but without photos I can't be sure, tannoy hf coils are all aluminium.
    Swap the hf diaphragms over to see if the fault follows it, are the voicecoil gaps clean, is the phase plug /pepper pot clean and unobstructed?
    As to harshness, even with correct Dias they can sound rough if you turn the energy up imho
  17. Serial number are

    206354 and 206359

    yes swapping the HF diaphragm moves the problem to the other speaker. I haven’t yet looked at cleaning the voicecoil gaps I will probably look to do this today and have a look at alignment. Do you think it will be possible to get the two different diaphragms to match better with alignment? Two new diaphragms will cost me around £400 so it would be nice to avoid that cost.

    Thanks for the advice about the cabinets I thought they might be my biggest issue regarding the low end.
  18. cooky1257

    cooky1257 pfm Member

    If the diaphragms are from a hpd and a 3128 you'll struggle to get a match. Post pics of both so we can have a look at them, if they are 205's i.e. The correct part then yes you can significantly improve their performance assuming the issue isn't elsewhere.
  19. Here are my two HF diaphragm's


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