JPW P1 rebuild/mods

Hi,

I just got my hands on a set of JPW P1 speakers. Got them for next to nothing because the woofers are missing and the state of the tweeters are unknown. So basically I got a set of cabinets in ok shape. :)

I'm a huge Vifa fan, I have a lot of different Vifa based speakers. But I have never had a set of the small sealed 8 inch types before. And now that I have a small dedicated listening room I thought this would be a cool project.

I see that the Vifa (Scanspeak) M21WG has an unusual frequency response compared to other Vifa woofers I have came across, with a sharp rising response from 1khz.
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Is this a similar response to the original woofers?

I have several sets of Vifa D19TD tweeters. I have 1 set that I took out of an old pair of Qln Qubic 222 which has a textile diphragm. This one sounds much better than the other plastic looking ones I have.

But I am also a little tempted to try out these Monacor cone tweeters. I see System7 on this forum has done a lot of experiments with.

So anyone with a recomended recipe for a crossover for the new Scanspeak M21WG 09 08 and Vifa D19TD or Monacor HT22/8?

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These are the ones tested by Dibirama in the first picture.

SCAN SPEAK - VIFA M21WG-09-08 (Woofer 8", 8 Ohm, 70 Wmax)

These are not NOS, they were made by Scanspeak 2015/2016. I'm just a bit sceptical if they measure the same as the original ones used by Snell, JPW, Heybrook and Audio Note. The spec sheet also shows this "hump". I cannot find any old spec sheet for the original Vifa M21WG.

Edit: Found a german site with spec sheet from 1982: https://www.lautsprechershop.de/pdf/scanspeak/ase_m21wg09_08.pdf
 
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A quick google search for Heybrook HB1 mk 1,2 or 3 crossover diagram should get you some relevant info.

In a similar vein a search for JPW P1 may throw something up. The original design was crossed over quite high in the 3-4 Khz band. A classic loudspeaker of its day, its was agile and had a sensible impedance that allowed its use with low powered valve amps.

If you cannot find anything in the next day or so send me a message and I will dig further for a basic Heybrook crossover. I did have a lot of stuff related to the driver used with a scanspeak 2010, 19mm, but that was a hard disk crash or so ago.

I think somebody in Northern Europe was making a clone for some years, and even today Wilmslow Audio in UK can still provide a kit based on the Heybrook HB1 cabinet dimensions and original drivers as a new batch of VIFA bass drivers was produced only two or three years ago on the original tooling by scan speak. If you contact Wilmslow audio they may give you the relevant crossover details or at least sell you the components.

I think if you purchase new Vifa MGW 21-09-08 drivers you will have an enjoyable speaker, most tweeters should be able to work with it due to a highish crossover frequency and the original bass units 87-88db sensitivity.

If you don't like the idea of buying the original driver a more modern scan speak discovery 8" will probably fit the original cut out, you will need to research this. However, in this sized enclosure it may not give the same bass Q factor as it is not an optimum box volume for this driver, but you will get a fast low q bass..To get more bass you may need to get it against the rear wall, or even towards a corner.
Alternatively a Visaton 8" or seas 8" will probably fit the original driver cut-out, ideally if you can find a driver with Q values that match the original vifa drivers you will have the same bass quality, but you will have to go through the full design process to mate with one of your preferred vifa tweeters.
 
Modeled woofers I found on Dibirama's site. Monacor SPH 220HQ, Peerless 830869, Scanspeak Vifa M21WG 09 08 and my modified Vifa M21WO 28 08.

These 3 other woofers will measure more or less dead flat up 3khz before they start a natural rolloff, so they will be much easier on crossover implementation.

All will work in the small JPW P1 cabinet, but the M21WG has 2-3db higher output (due to a Q of 1,25) in the 80-150hz range than the others.
 

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You can still buy the woofers and tweeters. I have a pair of JPW AP2 in my system hooked up to a Quad 306 and modified Dacmagic, and I think they sound awesome! Never harsh but definitely not dull, tight bass, lovely open midrange with plenty of detail from those little tweeters (the tweeters have a slight rise at the highest frequencies that add a touch of air).
The exact same driver compliment are used in the very highly regarded Snell k.
 
I think cbarth has revealed their secret.

The Q of 1.25.

May I add, also a some paper cone colouration, and a bit of beaming. Still a cult loudspeaker and still very enjoyable if you are not susceptible to these small foibles.

Maybe that's it. :) If you were to implement such a boost with a ported box and a low Q woofer I think you would have "one note", boomy bass. I guess closed boxes are a bit more forgiving.

When it comes to the midrange, I think there lies much of the "magic" of these Vifa's. The curvilinear shape of the cone and the foam surround.

I have these old Vifa M21WO 28 08 woofers from some vintage Dali speakers. I have them in my Impulse H5 inspired speakers. I replaced the rubber surround with new foam surrounds, and this gave a noticable improvement on the midrange. I don't know why.
 
You can still buy the woofers and tweeters. I have a pair of JPW AP2 in my system hooked up to a Quad 306 and modified Dacmagic, and I think they sound awesome! Never harsh but definitely not dull, tight bass, lovely open midrange with plenty of detail from those little tweeters (the tweeters have a slight rise at the highest frequencies that add a touch of air).
The exact same driver compliment are used in the very highly regarded Snell k.

I will test them out with just popping in my Vifa M21WO's, and if the tweeter's are toasted I have probably 4 or 5 pairs of D19TD lying around.
I also ordered a pair of Monacor HT22/8 and some crossover parts so that I can try out System7 recipie as well.
We'll see, it's just for fun... :D
 
I did a internet search for some crossover details. They used to be easy to find, but I didn't have much success. I probably did have the data on my crashed hard disk, but that will take time.

I did find the following for something that I played around with a few years ago which could be a starting point for you. Do you have a 19mm tweeter that is anyway like a scan 2010B as that is what I used at the time?

Bass input 0.75mH, I guess 1mm wire gauge, followed by a Zobel of 15uF and 8 ohms or thereabouts in parallel with the bass unit.
scan 2010B unit for the tweeter.
This had a 3 ohm input resistor, 2.4uF, 240uH coil for the parallel branch and 11uF for the final series capacitor. This put the crossover at approx. 3.6Khz, with an easy impedance and gentle phase changes. A SE 300B amp will drive it.

It should give you some food for thought. Depending on taste you may want to tune the 0.75mh. I doubt you will get past 1.8mH as it will be loosing some of its magic by then.
When you get it dialled in you will enjoy it. As to driver polarities I cannot see as the print doesn't quite fit the page, and the tweeter connections are not shown. Sorry.

I would love to have a modern equivalent, using the latest knowledge on cone, suspension, magnet and pole, plus shorting rings. Whilst maintaining the Q values of the original so it can be used in a sealed box. How many would we have to buy as a group buy to get one of the big companies to do a few prototypes and a production run. if the modern implementation can keep the magic, and improve in a few areas, I guess it would be an amazing driver to revive that style of speaker design.
 
Thank's Raymondj!

What a great idea! I'm not sure how many we would have to be, but I know for a fact that norwegian Seas is pretty flexible of doing custum production runs of drivers. The question would be how many would be interested in such a thing, and how far would you want to go? The sky is really the limit. :D

Like Troels Gravesen's JA8008 HMQ, Audio Note woofers or Joachim Gerhard's woofer used in the Sonics Arcadia.

What I would like for a custom driver for this project: Curvilinear paper cone, foam surround, alnico magnet, copper shorting rings, QMS of minimum 5,0, VAS, QTS and FS as close to the original Vifa M21WG 09 08 as possible and as smooth top end as possible.

Pair that woofer with something like a Hiquphon tweeter and team up with Troels Gravesen or Joachim Gerhard and make a killer version of a speaker Peter Snell would have made if he was still around. :D

I would have jumped on this project in a heartbeat! :D
 
As a kindness to our hosts I think we should do the design here.

Initially I think we need to get a consensus on the driver spec and find a manufacturer willing to support us in making some samples and providing them for test and measurement.

What I find lets the original driver down, is some paper colouration and it doesnt take too much power, which is to be expected with a small voicecoil and its originally specified operating power. Doesnt the specc sheet talk about 9 watts or so ?

In terms of modern design should we cross it over at about 1.8Khz or less and use a modern tweeter tha can handle such a low crossover, or if we do this will we loose the magic.

Your proposed criteria for a modern re deign seem perfect, but I am not a loudspeaker drive unit designer. Possibly one reading this right now and laughing about what we would like ?

I cannot argue with your criteria, I would like to see what a manufacturers representative would bring to the forum, and tell us plainly that some of the things listed are not simply achievable below XXX Euros. Too high a cost will put it out of reach for lots of people and it wont be taken up widely by the community.

Another point that we should consider is our planets resources, use of energy and plastics where necessary.
We are starting out well by specifying paper. However, the cone skin, suspension and surround are likely to contain some plasticiser, or other undesirable plastic based material.
As to the magnet material. Which one uses the least energy for its production, and is the magnetic material made from a resource that that we are not running out off. Maybe the suggestion of an alnico magnet, is a better idea than a neodymium one, but it will add to the cost. I can see a double blind listening test coming on, to verify the differrence between, a Alnico, a Ferrite, or a neodymium magnet assembly.

The big manufacturers must be wakening up to these facts about overall energy costs, and certainly now in the last year or so the use of plastics. It would be so good to get the balance right on any green credentials as well. Possibly you cannot make a high performing loudspeaker without the use of plastic, for the surround or spider. Who knows ?

I am being naïve here, as we cut down trees to make the majority of the boxes we use to make our loudspeakers.
Twenty years ago I would have said lets go with your specification, but maybe today we should be more careful in using our resources.

As you are up cycling or re cycling some old boxes you already win points for that, and I still use my original 20 year old MDF boxes that I used for my first play with the Vifa drive unit. Screw in baffles are your friend here and allowed them to be used for testing several differrent drivers over the years. A SB Satori 19 8 ohm will be the next speaker to grace the originall boxes, but it wont have a Q of 1.5 in them, it will be much lower.

Looking forward to see how this goes.
 
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raymondj, the Norwegians in Arendal have more trees than they know what to do with! So don't agonize about all this tree-hugging environmental nonsense! As Bill Clinton said, "It's all about the economy, stupid!" :D

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I just love this stuff!

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What to do with an 8" paper woofer and 3/4" plastic tweeter? Well, clearly we don't have to reinvent the wheel!

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This is a favourite speaker of mine, the Wharfedale Shelton XP2:

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I had a close look at the crossover, and it was quite surprisingly good:

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Models roughly like this:

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Electrically it looks like this:

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All I can say, is given an 8" paper woofer, and a 3/4" mylar tweeter, this is a good way to do things. :)
 
I think if one was to proceed with such a project Seas would be the most logical place to start. The price per driver would be greatly affected by the amount of drivers being made. If you look at the Jantzen JA8008 HMQ it has a list price of 222,37GBP at Hifi-collective, so I guess that is in the area we will be talking about.
I'm not so sure about the 1,8khz crossover thing though. In normal high end hifi consensus I would be, but I feel this kind of speakers are more about music and less about hifi kind of way.

Like the Buchardt S400, it's a great speaker. Packed with technology in driver development, measuring and crossover techniques and at a great price (for what you get IMO). When I ask people why it's so good they usually somthing in the lines of great soundstage, great bass, great imaging and so on.
Then ask someone after a successfull demo of a AN-K or Snell-K. Most people find it hard to point out exactly what made the experience so good, but most music lovers just connect to the experience.

System7; you are absolutely spot on! It is actually becoming a big problem here in Norway with too many trees. We don't have to supply timber for sailing ships, rebuilding of London and the building of Amsterdam anymore. :D

The most green thing we can do in this hobby is to buy and build things that will endure, and not be thrown away when the next fashion shows up around the corner.
 
"All I can say, is given an 8" paper woofer, and a 3/4" mylar tweeter, this is a good way to do things"

I don't disagree, I do like the sound. Wharfedale, Celestion, Kef and B and W was what I grew up with, initially they were of the wide baffle sealed box variety until the odd reflex port appeared on the scene.

Cbarth does care about his trees and herrings and lots of other environmental stuff. He just hasn't told us yet. :)
 
What I find lets the original driver down, is some paper colouration and it doesnt take too much power, which is to be expected with a small voicecoil and its originally specified operating power. Doesnt the specc sheet talk about 9 watts or so ?

.

I don't know the exact power handling but I do know that they go more than loud enough in an average sized room.
 
Just for fun, here is a quick comparison. Vifa M21WG and Monacor SPH220HQ using measurement data from Dibirama. Vifa in 20 litres, Monacor in 10 litres.

Vifa has a Q of 1,25 and Monacor has a Q of 1,15.

Now the Vifa has about 2db higher sensetivity but the Monacor can handle a lot more power, so it can ultimately play considerably louder.

First picture is box simulation, next is sensetivity 2,8V, and third picture is spl at linear xmax. (It occurs at 16W for the Vifa and 100W for the Monacor)
 

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Thanks system 7 for finding a Hb1 Mk1 crossover design. Plus your other useful stuff.

Taking two points from an earlier reply by cbarth, apologies for the editing.

"I feel this kind of speakers are more about music and less about hifi" and also,

"Then ask someone after a successful demo of a AN-K or Snell-K. Most people find it hard to point out exactly what made the experience so good, but most music lovers just connect to the experience"

Definitely, this tells us about what some people hear in the Snell K, JPW and Heybrook speakers we are talking about. There are approximately nine different speakers in total here, using the paper cone vifa. Maybe eight, as the Snell K II had a peerless polypropylene I believe.

I think within the eight choices, we have sealed box sizes between 20-30 litres, crossover points between 2.4Khz - 4Khz, and a bunch of vifa 19-25mm tweeters. Plus a combination of first order second order crossovers for bass, and similar for the tweeter. I stand to be corrected so please do.

So is the linking factor the vifa bass in a sealed box, oh, and a vifa tweeter ?

If we go with a new take on the driver using todays knowledge and better materials will we have the same magic? What about a simpler set of requirements what would a modern voice coil, possibly implementing current thoughts on motor design, if we go with a heavier cone then yes we would need a better magnet, but the sealed box means it doesn't have to be too big etc. Maybe a phase plug would take care of some of the frequency response in the higher regions?

It does seem interesting to me that to recreate the LS3/5A Falcon acoustics have re created the LS3/5a in its entirety to guarantee the same magic.

I think a new driver should have a magic all of its own, but I don't think we can guarantee that it will seem as musical as the original. To do that it seems we simply buy the existing Vifa MG21-09-08 until stocks are exhausted, and build clones of the originals.

Going down the route of a new driver we would be starting afresh, and it would be up to us to optimise the box dimensions, shape, crossover, box stuffing and bracing. Do we have a few months of spare time? I must look at the jantzen driver and see how many of the boxes it ticks

A new design would not happen overnight.

I am guilty of not doing an exhaustive search for paper eight inch drivers, so maybe there is another contender out there already from 18 sound, B & C etc.
 
System7 I have not tried any of your crossovers (yet :D), but I'm wondering about the series inductors in your simulations. By the look of the values it looks a bit high? 1,8mH on a driver that is more or less flat in it's operating range and crosses over at 3khz?

Here is Troels Gravesen's measurement of the SS 18W/8542-10 without any crossover, and with a 1,8mH series inductor.

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