View Full Version : DIY Tannoy MG 15 Crossover - Help Needed
I am planning to build an external crossover for my Tannoy MG 15 based on the attached schematic. I am thinking to wound an air-core inductor with multiple tap of 4mH and 4.5mH to replace the autoformer. I know many AOS members have done this before. Can anyone let me know whether this a right way to do?
:doh:
Wakefield Turntables
28-07-2016, 07:08
Speak to paul at RFC
Erm that's a Messed Crossover.
Don't use it ! The alleged "Tannoy' schematic underlying it is Wrong.
Some twit mislabelled the thing ..years ago. And the error spread like mold.
Read This Tannoy info first :
http://www.troelsgravesen.dk/Diy_Loudspeaker_Projects.htm#Vintage
All 3 parts of it, before going further
I am planning to build an external crossover for my Tannoy MG 15 based on the attached schematic. I am thinking to wound an air-core inductor with multiple tap of 4mH and 4.5mH to replace the autoformer. I know many AOS members have done this before. Can anyone let me know whether this a right way to do?
:doh:
Those are completely the wrong values Alfred, as Danilo suggests, but also, Troels versions use the wrong values for the crossover too, so don't use those either as there is equally some glaring errors in his circuit. I have emailed you with advice. You cannot remove an autoformer and replicate exactly with fixed inductors due to the voltage step and electrical Q differences. What you can to is to provide a more linear response than the originals but you do need to compensate for the electrical Q of the circuit in the HF.
walpurgis
28-07-2016, 09:41
Some good advice here Alfred. Have fun with your Tannoys. They will sound great with good crossovers.
Many thanks for all the valuable advises! Paul has sent me many good recommendations that I need to sit down and digest. For simplicity, I may keep the original autoformer and change the rest of the inductor to air-core. :scratch:
Many thanks for all the valuable advises! Paul has sent me many good recommendations that I need to sit down and digest. For simplicity, I may keep the original autoformer and change the rest of the inductor to air-core. :scratch:
I'd keep the laminated cored inductor for the LF. It wont have the coupling issues of a large air core in the bass position. I do have manufactured purpose designed and wound laminated steel E&I cored inductors for this purpose which are available in uprated spec (ie there's no chance they'll saturate) which are an upgrade over the standard ones, but the standard ones are fit for purpose. The HF and notch filter benefit from being air core. Don't forget when working out the notch coil's DCR to account for the overall impedance required at low frequency (ie DCR equivalent) from the whole LCR filter. Just because the schematics don't show DCR values it doesn't mean they don't exist! Measure your current notch filter inductor (ref WC3121) and ensure that the total DCR for the notch filter = this value plus around 0.5 Ohms. Leaving out this series resistor or using a way lower DCR inductor here will create an effective short to ground in the HF and kill your HF response (as well as not doing the amp any favours).
Many thanks for your explanation! Need to go back to the drawing board and rework. :D
Dunno What? yer expecting from a crossover remake. I've been Foolishy Dicking with Golds' Crossovers since 1980
Tried pretty well ALL permutations, likely preceeding all the bespoke/for a price ;) variants from the 'proliferation' of shed makers of recent years.
The OEM crossover, simply recapped with Moderne Film 'n Foils (ONLY) has Proven to be damned near indistinguishable from ANY bespoke variants.
At least to Human ears :eyebrows:
Once recapped... the BEST Tannoy upgrade possible is a Worth Owning Amplifier... and a music source/.input that isn't Crap.
Have spent time with an Active setup.. Which did/does work to expectations.
But In truth it's a bit of a PITA to implement. Currently it's shelved (but not forgotten) with only minor audible losses resultant.
Do Note that 'active' IS a superior path to an udulterated Crossover... If willing to deal with the complexities/inconveniences of an Active setup.
Tannoys for reasons that likely only GRF knows (if he even did :-) respond spectacularly to upstream Gear Quality improvements.
As small aside; Nelson Pass uses Tannoys in Imperial cabinets.. as his Reference speakers.. which in itself speaks volumes imo.
He's the man who had auditorium sized Keigellhorns built/installed in his home at one point
Tannoys.. despite views that these may not be the best speakers possible but rather because these respond/display even the smallest of Nuances in upstream gear quality.
Seriously important to a man who comes up with a fresh Amplifier Design topology every few weeks/months
Sooo. IMO spend up to /no more than ~50$ on decent film 'n foil caps for your oem crossovers... and stop there... saving yourself a couple of decades of "wild goose chasings :-)
THEN save up your $$ for gear Worthy of the rascals. You won't be disapointed.
Dear all,
I know you guys have walked this path before and your valuable recommendations or suggestions are welcome. The more I think, recap might be the only way to go. The reason I want to build a new crossover is to preserve the original crossover if I decide to sell the MG15 later. I hope the air-core inductor can further proivde sonic improvement. I have no intention to fool around with the schematic.
By the way, any of you have taken the recommendation from DIY Louspeakers on using 1.2mH, 6.8Ohm and 30uF for the LH? If yes, any good?
Best regards,
Alfred
Dear all,
I know you guys have walked this path before and your valuable recommendations or suggestions are welcome. The more I think, recap might be the only way to go. The reason I want to build a new crossover is to preserve the original crossover if I decide to sell the MG15 later. I hope the air-core inductor can further proivde sonic improvement. I have no intention to fool around with the schematic.
By the way, any of you have taken the recommendation from DIY Louspeakers on using 1.2mH, 6.8Ohm and 30uF for the LH? If yes, any good?
Best regards,
Alfred
Alfred, a few words to the wise ;).
First off, ignore the naysayers :rolleyes:. Most, if not all have neither the measurement kit nor expertise to understand what is possible, let alone the design expertise. There are those that do and those that don't. Few do. DIY fiddling does not an expert make.
Secondly, you have two basic choices. 1) stick to the standard crossovers and have them refurbished. This means taken apart, switches cleaned and refurbished, all capacitors replaced or upgraded (the cost of the parts isn't that great and as they're apart it makes perfect sense) and better more appropriate quality wiring to the 4 pin connector. The originals are 3 core lighting flex and non-ofc so over the years they suffer corrosion especially at the joints.
It simply isn't worth going down this route though if you don't intend keeping the originals, and for reasons that I have already explained on countless threads on this subject before, there most certainly are benefits to dumping the autoformer and going to high quality external crossovers, or at least PTP internal board mounted ones. It has been proved beyond any doubt that improvements to polar response, step response and linearity are achieved, along with better channel balance and lower distortion. Its simply physics at work, and there's no magic or fairy dust involved. If you intend on keeping your Tannoys as final destination speakers, then those "in the know" will tell you that this is your best option for sound quality. Those that say it doesn't make a difference clearly have no knowledge or experience with the designs that I am talking about, period.
Now, as to the values you've quoted above, don't go there. As I have already explained, those inductor values are WRONG and should not be used. They will run the bass cone WAY too high and raise distortion and mid-forwardness appreciably. I don't know where you get 6.8 Ohms from but that isn't correct either and nor is the capacitance value for the 2nd pole; that should be 16uF and not 30uF. As I've tried explaining, be careful with what you believe when looking at Tannoy from the internet...most of it is wrong, including a lot of info on the Yahoo users group.
Paul, is there a correct circuit diagram that Alfred could consult?
Paul, is there a correct circuit diagram that Alfred could consult?
There are circuits doing the rounds Mark but most are wrong, hence I dont tend to point people in that direction. I have a book of circuits for many different loudspeakers whch I have put together myself, which covers many vintage designs and am happy for people to come to me if looking for advice as I can often thumb through until I have the right circuit and advise on values. Tannoy are a bit different as the design for the circutis I use I have developed using measurement and listening tests. Whilst I aim to stick closely to Tannoy's aims, there are a few fundamental differences and I dont wish to publish my work for obvious reasons. The ones often found online with the Tannoy Logo or Tannoy name in the drawing notes box etc have been doctored as Tannoy never produced these with inductor values, just the inductor reference numbers. I have emailed Alfred with the correct values he needs for the LF.
Hi Paul,
Please excuse me for asking all these stupid questions! :doh: I just try to gather all the information that I can get from the net.
I enjoy my Arden MKII for many years and I brought the MG15 in a sealed Lancaster cabinet a few years ago to hope this will be an upgrade for my system. However, it turned out to be not the case. I left the MG15 at the corner until I have time to spend on it a year ago.
I find the MG15 has good personality but Lancater for sure is not the right place for it (Even Open and ported). I am planning to build a modified York cabinet (~270 Liter) and go with an external crossover. For the crossover, I will use the original crossover at the beginning, upgrade the cap afterward and finally go with air-core. At this point, my MG15 is still a virgin (untouched). :D Here is a recent pic of my gears.
17628
There's no such thing as a stupid question Alfred, so ask away.;)
You are right in that the Lancasters are not the best speakers for the MG 15 (in fact they're one of the worst) as they are undersize and very resonant. Cabinets weren't done that well by Tannoy with a few exceptions (Westminsters and Autographs). The magic doesn't really happen until you are north of 180 litres net volume for the 15 inch MG, and preferable 200 to 220 litres which is optimal for vented or aperiodic tuned cabinets. The Ardens imho are a better speaker but they require some cabinet work and tweaking of the tuning to sound at their best too.
I have plans for a cabinet of ideal volume for the 15" MG called the "RFC Warwick". Andy ("Rexton" on here) had a pair made from plans and he might be happy to offer you a direct comparison between his Lancasters and RFC Warwick cabinets. I'm sure that we can do something for you around provision of some plans if you can find someone locally to you who can build them and fancy going down this route :cool:
montesquieu
30-07-2016, 23:20
Dunno What? yer expecting from a crossover remake. I've been Foolishy Dicking with Golds' Crossovers since 1980
Tried pretty well ALL permutations, likely preceeding all the bespoke/for a price ;) variants from the 'proliferation' of shed makers of recent years.
The OEM crossover, simply recapped with Moderne Film 'n Foils (ONLY) has Proven to be damned near indistinguishable from ANY bespoke variants.
At least to Human ears :eyebrows:
Once recapped... the BEST Tannoy upgrade possible is a Worth Owning Amplifier... and a music source/.input that isn't Crap.
Have spent time with an Active setup.. Which did/does work to expectations.
But In truth it's a bit of a PITA to implement. Currently it's shelved (but not forgotten) with only minor audible losses resultant.
Do Note that 'active' IS a superior path to an udulterated Crossover... If willing to deal with the complexities/inconveniences of an Active setup.
Tannoys for reasons that likely only GRF knows (if he even did :-) respond spectacularly to upstream Gear Quality improvements.
As small aside; Nelson Pass uses Tannoys in Imperial cabinets.. as his Reference speakers.. which in itself speaks volumes imo.
He's the man who had auditorium sized Keigellhorns built/installed in his home at one point
Tannoys.. despite views that these may not be the best speakers possible but rather because these respond/display even the smallest of Nuances in upstream gear quality.
Seriously important to a man who comes up with a fresh Amplifier Design topology every few weeks/months
Sooo. IMO spend up to /no more than ~50$ on decent film 'n foil caps for your oem crossovers... and stop there... saving yourself a couple of decades of "wild goose chasings :-)
THEN save up your $$ for gear Worthy of the rascals. You won't be disapointed.
Danilo we went through this last time you posted about Tannoys. You are talking from a DIY/amateur perspective here when Paul is a professional. You are just embarrasing yourself.
Hi Paul,
Yes, the Arden MK II is very balanced and able to provide me a 3 dimensional sound stage. However the base seems to be muffled and that's why I upgrade to MG15. My Lancaster originally with port hole sealed, after the modification it give me some base but the cabinets want to dance along with the music when I crank up the volume.:carrot:
Actually, I am better in wood working as compare to tweaking in electronic circuit. :eyebrows: My current plan is a 100cm x 60cm x 45cm (~270 Litre) with a square port tuned at 30Hz. I have not seen a "RFC Warwick" before. It will be great if I can find a plan for a proven cab. :please:
Powered by vBulletin® Version 4.2.3 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.