Hope everyone is staying well during this horrible pandemic situation. I need your guidance to upgrade my newly acquired Tannoy Cheviot. I bought it in a quite good condition. the drivers are in perfect condition and surrounds are changed. The cabinet is in good condition. It performs very well, specially with the instrumental music or jazz or blues, but I am not happy with the performance once I play a rocks for heavy metal. It seems the sound is little dry and the lower end is kind of shy; like the nodes of kick drum or bass guitar are not satisfactory also the top end is little harsh in my ear. I am using a DIY tube preamp and DIY First watt m2 power amp. My DAC is Soekris DAM 1021. I also have DIY finalist speaker (jim holtz) that is powered by Parasound Halo A21 and P6 power and pre. It is a fantastic combination.
I want to upgrade the xo of Cheviot. I have opened the Cheviot to get the value of the capacitors, but failed as the writing on the capacitors are not readable. Can someone please help me with the crossover schematic of the Cheviot or tell me the value of the capacitors that I need to change. I tried to find it on the web but could not get except a circuit diagram of xo of hpd315 driver. I need circuit diagram of Cheviot in particular. I know that Cheviot has hpd315A driver in it.
I want to upgrade the xo of Cheviot. I have opened the Cheviot to get the value of the capacitors, but failed as the writing on the capacitors are not readable. Can someone please help me with the crossover schematic of the Cheviot or tell me the value of the capacitors that I need to change. I tried to find it on the web but could not get except a circuit diagram of xo of hpd315 driver. I need circuit diagram of Cheviot in particular. I know that Cheviot has hpd315A driver in it.
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Maybe you should first check the suspension of the LF driver and maybe (don’t know whether Tannoy used it here) the ferrofluid on the tweeter. Thin low end could be a suspension of the cone gone stiff. With change of surrounds you would normally check the tuning of the enclosure too.
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Thank you. I think suspension is okay, it is easy moving when I press the cone and also visually the spider looks alright. I have not checked the fluid, I don't want to disassemble that untill it is absolutely necessary, in that case, I need to take that the workshop. Can you please tell me how to check the tuning of the cabinet.
What I do is measure the impedance curve of the speaker. Two times: once mounted in the enclosure, once open air. One needs a sound card with two line inputs for that though, some basic electronics (resistors and some wires) and some knowledge about using LIMP or other apps.
The only simple thing I can think of is using a computer app that can generate pink noise. Connect it to the amp, be careful with the volume settings and measure the speakers with an appropriate (free) app on your phone (Etani RTA, AudioTools RTA. Measure at close range (say a foot) in the biggest space you have available (outdoors?). That should give a bit of a clue about the low end reproduction, be it with some wide margins.
The only simple thing I can think of is using a computer app that can generate pink noise. Connect it to the amp, be careful with the volume settings and measure the speakers with an appropriate (free) app on your phone (Etani RTA, AudioTools RTA. Measure at close range (say a foot) in the biggest space you have available (outdoors?). That should give a bit of a clue about the low end reproduction, be it with some wide margins.
Tannoy didn't make crossovers specific to cabinets, the crossover for a given driver like the HPD315 was used in all cabinet variations.
The bass extension and apparent leanness or otherwise of a system is a function of the box design, not the crossover. To my eyes, the Cheviot has too small a port. The same tuning with a larger diameter ports would probably help, 100 or 110mm with flairs both ends, and length adjusted to get the same Fb. This is a common modification.
Also a lower loss inductor (lower series R) will help the solidarity of bass. I believer the WC3120 is 1.2mH, so without spending a lot of money you could use a Jantzen 000-5004 1.2mH 0.11Ω iron core inductor. (Edit: the original inductor is probably 2.3mH / 0.25Ω if I recall correctly. but if you do the crossover changes shown in the link a couple of paragraphs down you'll need 1.2.) I've managed to fit these in the crossover in place of the original inductor. Jantzen Audio 1.2mH 15 AWG P-Core Inductor Crossover Coil
I've also used various air-core and custom cored inductors in various Tannoy rebuilds I've done for other people. Depends how deep your pockets are; mine have a custom coil wound on a proprietary Krix core with Rdc 0.1Ω and Q=48 @ 1kHz.
I just found a page where someone else has done what I have done, namely compensate the driver inductance properly and implement an (electrical) first order crossover. Great minds think alike? (Note mine are 15" Arden MkIIs, his are 15" Monitor Golds, but the drivers are all from the same mould, even the 12s, when it comes to the crossover.) Have a look here: MG15-problem
The LCR shunt network across the horn takes some squawk out of the horn ~1.8kHz. I've added a second LCR network that compensates for the resonant frequency of the HF driver ~550Hz and gets it to behave a bit better when terminating the crossover. That cleans the mids a little and smooths the transition behaviour between cone and horn.
The bass extension and apparent leanness or otherwise of a system is a function of the box design, not the crossover. To my eyes, the Cheviot has too small a port. The same tuning with a larger diameter ports would probably help, 100 or 110mm with flairs both ends, and length adjusted to get the same Fb. This is a common modification.
Also a lower loss inductor (lower series R) will help the solidarity of bass. I believer the WC3120 is 1.2mH, so without spending a lot of money you could use a Jantzen 000-5004 1.2mH 0.11Ω iron core inductor. (Edit: the original inductor is probably 2.3mH / 0.25Ω if I recall correctly. but if you do the crossover changes shown in the link a couple of paragraphs down you'll need 1.2.) I've managed to fit these in the crossover in place of the original inductor. Jantzen Audio 1.2mH 15 AWG P-Core Inductor Crossover Coil
I've also used various air-core and custom cored inductors in various Tannoy rebuilds I've done for other people. Depends how deep your pockets are; mine have a custom coil wound on a proprietary Krix core with Rdc 0.1Ω and Q=48 @ 1kHz.
I just found a page where someone else has done what I have done, namely compensate the driver inductance properly and implement an (electrical) first order crossover. Great minds think alike? (Note mine are 15" Arden MkIIs, his are 15" Monitor Golds, but the drivers are all from the same mould, even the 12s, when it comes to the crossover.) Have a look here: MG15-problem
The LCR shunt network across the horn takes some squawk out of the horn ~1.8kHz. I've added a second LCR network that compensates for the resonant frequency of the HF driver ~550Hz and gets it to behave a bit better when terminating the crossover. That cleans the mids a little and smooths the transition behaviour between cone and horn.
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Yes worth trying. I heard some DIY Cheviots recently with the ports plugged and they sounded very sweet indeed.
From what I remember Cheviots use HPD315A.
Those are very low Qts drivers, something like 0.2. In a sealed cab they will be VERY bass shy starting to roll off just below 200Hz.
They need large ported cabs tuned to driver Fs to give their best and their best is basically an Extended Bass Shelf alignment which can be fixed either by room gain or a simple bass control as used to be fitted to most (pre-)amps.
Also HPDs were specifically designed for transistor amps and they thrive when driven by large ones capable of supplying a lot of current.
Those are very low Qts drivers, something like 0.2. In a sealed cab they will be VERY bass shy starting to roll off just below 200Hz.
They need large ported cabs tuned to driver Fs to give their best and their best is basically an Extended Bass Shelf alignment which can be fixed either by room gain or a simple bass control as used to be fitted to most (pre-)amps.
Also HPDs were specifically designed for transistor amps and they thrive when driven by large ones capable of supplying a lot of current.
Tannoy did not use ferrofluid for the HPD drivers. Play a 2KHz tone to check the HF coil is not rubbing. The cabinet space is usually not well damped. This creates ripples in the response. Damping the space will reduce the efficiency but improve quality.
Thank you. It's lot of information, I am trying to understand. The TS parameter of MG 12 or 15 is different than HPD 12 or 15. Should it match the inductor value? Did you upgrade your hpd 15 following the link that you have given and how does it sound after mod? Best regards
I also powered it by Parasound A21. I have already changed the internal damping by egg crate acoustic foam.
The low frequency alignment of the box is not related to the inductor directly. The inductor forms the low pass filter for the crossover - that's at the upper end of the bass driver's range. The TS parameters relate to the bass loading of the system, which is at the lower end of the bass driver's range.
I didn't copy the link I posted, but I did the same based on my own measurements and development a few years ago. I was quite surprised and pleased to see someone else has come to the same result and documented the process.
I think my modified Ardens sound very good indeed, in fact better than I ever expected they could be. They are based on the K3828 ceramic magnet drivers that came after the HPDs. There is no harshness whatever in them, and no particular benefit to listening off-axis, or on axis, they just sound great everywhere.
I didn't copy the link I posted, but I did the same based on my own measurements and development a few years ago. I was quite surprised and pleased to see someone else has come to the same result and documented the process.
I think my modified Ardens sound very good indeed, in fact better than I ever expected they could be. They are based on the K3828 ceramic magnet drivers that came after the HPDs. There is no harshness whatever in them, and no particular benefit to listening off-axis, or on axis, they just sound great everywhere.
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Well, I don’t know, but chances are the magnet strength of the old unit has lowered. That, together with the uncertainties about the cone suspension, would urge me to bring out the measurement equipment just to discover if there’s any reason for hope left. This set is more than 40 years old likely…
I would disregard any suggestion that HPD315s are too old. IME the Cheviots were always lean sounding and will respond to updating. Over the past few years I have rebuilt a lot of old (pre-1980s) Tannoys for people who are always delighted with the result. My Tannoy tinkering started several years back when I rebuilt a pair of mid 1970s HPD385 Ardens for a studio and got a bit of attention from audio professionals who thought they sounded just great.
Being AlNiCos unless they experienced a hard knock or similar mechanical trauma the magnets should be almost as good as new.
You can heat AlNiCo to red hot and they will retain their magnetic strength.
Dear daniel4381,
I don't know if I'm late, but the circuit diagram you have in post#1 seems to be the correct one, according to the following document, which is a database of all Tannoy speakers (till date):
https://www.hilberink.nl/tannoy/jpvanson/speakers.pdf
Besides, I happened to find the same circuit diagram from the following webpage (not repeating the picture here) and some more information on the HPD series:
Tannoy Monitor Crossover Circuits
hpd tech manual
hpd series
Don't know if that helps.
I don't know if I'm late, but the circuit diagram you have in post#1 seems to be the correct one, according to the following document, which is a database of all Tannoy speakers (till date):
https://www.hilberink.nl/tannoy/jpvanson/speakers.pdf
Besides, I happened to find the same circuit diagram from the following webpage (not repeating the picture here) and some more information on the HPD series:
Tannoy Monitor Crossover Circuits
hpd tech manual
hpd series
Don't know if that helps.
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