Fostex studio monitors

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rab1991

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So starting this thread mainly to see if any one has any experience with vintage fostex drivers, and guessing the diy section is the best place as I'm guessing these are home built to some degree.

On holiday in France I had the great idea of opening up Facebook Marketplace only to be greeted by a short advert saying fostex studio monitors and they were asking for offers and some blurr, dusty photos .After liberal use of google translate I got an address and a time.

Upon arriving I didn’t realise quite how big they were in person and with some help they just about fit into the car. After throwing away some of the non essentials, somehow managed to package all the luggage around them to get back. How I didn’t get stopped by the border force on the way back into the UK I have no idea. Whilst waiting for the ferry in calais I got talking to a guy who said i should get on the wam so here I am.

So they use a full set of fostex drivers,

T825
D252 with k100
F205
Fw400

From a bit of research most fostex monitors seem to be mainly a 3 way set up, omitting the f205 and either using the fw400s or the l475 which both have greater sensitivity, closer to that of the t825 and d252. These have a level control each for the f205, t825 and d252 which I’m guessing help to match the sensitivity issues though.

When i get a bit more time i will try and look at the crossovers but i’m not too clued up on crossover designs etc.

Both midrange and bass drivers need refoaming so will have a think on where to go with these speakers once they have been done.

Either use as is or build some sort of rwo fostex studio monitor replicas.

Here are some rough photos for now.

PXL_20220705_142808374.jpg
PXL_20220706_211109216.jpg

PXL_20220706_214329215.jpg

PXL_20220707_134838914.PORTRAIT.jpg
 

MF 1000

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Looks like the start of an epic rebuild etc. Could be well worth the effort with refoaming of the drivers and refinishing of the external surface of the cabs etc.

Keep us posted 👍
 

rab1991

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Nothing more to report yet, ordered foam surrounds for them so just waiting on delivery of those before i can start working on with them. whilst waiting i've also found a Fostex Laboratory Series 600 power amplifier up for sale, which although unknown sonically would be the "right match" for these but finding it hard to justify buying it at the moment.
 

rab1991

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New surrounds turned up yesterday, managed to clean up all the old foam yesterday and fit surrounds to one bass driver and one midrange. So only two drivers left today. Hopefully have first listening impressions tonight or tomorrow.


PXL_20220802_154926283.jpg

PXL_20220803_105155063.jpg
 

rab1991

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So not had much chance to listen, 2 hours at most and I'm not great in putting things into words so here goes nothing. They either sound incredible, or absolutely terrible. Either superbly natural, detailed and dynamic and completly effortless or completely coloured in the mid and sound all harsh and shouty. I'm guessing they're just doing what they do in being brutally honest, kind of in the same way yamaha ns1000m are.

There are some marks on the l pads i guess from the previous owner and ive ended up being about 2db to 3db down to where the marks are which is roughly where the dials get set from normal on my ns1000m, but i think a lot more tweaking is required and some more work on there positon.

With the langauge barrier it was hard to understand but I'm sure the person I bought them from said they hadn't been used in about 20 years, so with that in mind and the fresh surrounds, which could also change the sound signature. They might just need some more use to settle down.

View attachment PXL_20220803_193841849.TS.mp4
 

Jazid

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These will definitely take 50+ hours to break in the foam, and for the sound to get "easier" (in my limited experience of other re-foamed speakers).

I'd also do a couple of (quiet) frequency sweeps to see if there are any obvious anomalies that might point to rubbing coils, dried caps or burnt/ drifted components in the crossover. There's plenty here can advise on condition, methods of investigation, etc.
 

ff1d1l

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Some years ago I landed a pair of Urei 811s, which use a big Altec driver, 804 8k IIRC.
Like you I thought them promising rather than actually arrived.
I silver soldered all the push fit connectors, and bypassed the driver connections and soldered those and the crossover connections too. Bypassed the L pads with resistors of the value for the settings I liked.
Sound excellent now, on as I type this. Took them to Scalford a couple of times.

A lot of those studio monitors from the 70s and 80s used push connectors and benefit from similar...I've done it on L40s and 4411s too, to substantial effect.
 

rab1991

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Some couple of good pointer there, I've not refoamed anything before so good to know they might take some time to run in.

All the drive units have quite nice screw terminals. I could possibly solder the bass and midrange driver connections. And possibly rewire them internally as some of it looked a bit of a mess.

I spent a few more hours listening yesterday, think I have the l pads sort of set but still more tweaking to be done.

still have the same reservations so far of them either sounding stunning, or just horrendously coloured with some vocals sounding like there hands are half over there mouth.

Hopefully have some more time next week to run them in a bit more. But might need a trained set of ears to see if I'm doing anything wrong with them.
 

Fatmarley

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Some couple of good pointer there, I've not refoamed anything before so good to know they might take some time to run in.

All the drive units have quite nice screw terminals. I could possibly solder the bass and midrange driver connections. And possibly rewire them internally as some of it looked a bit of a mess.

I spent a few more hours listening yesterday, think I have the l pads sort of set but still more tweaking to be done.

still have the same reservations so far of them either sounding stunning, or just horrendously coloured with some vocals sounding like there hands are half over there mouth.

Hopefully have some more time next week to run them in a bit more. But might need a trained set of ears to see if I'm doing anything wrong with them.

Are all the drivers wired in the same polarity (left pair, same as right?)

From what you describe ("horrendously coloured"), no amount of running in, is going to fix that. A frequency response measurement should reveal what's going on.
 

rab1991

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Ill have another look but Im sure they all were.
Its about 50/50 on what tracks sound right and what sounds wrong. It could just be them doing what they do pulling apart bad recordings.

It's ultimately why I stopped using my pair of ns1000m.
Are all the drivers wired in the same polarity (left pair, same as right?)

From what you describe ("horrendously coloured"), no amount of running in, is going to fix that. A frequency response measurement should reveal what's going on.
 

Fatmarley

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It could just be them doing what they do pulling apart bad recordings.
If only I had £1 for every time I blamed it on the recordings... What recordings sound bad?

I'd be amazed if it wasn't either a fault, bad crossover design, or drivers that have such a wonky frequency response, that no amount of crossover tweaking can fix it.
 

rab1991

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It'll probably be next week untill I have time to take them apart again to check all is wired ok.
I'd take a guess that the drivers themselves are ok unless the new foam surrounds have altered the spec of them.

I'll keep on with setup and positioning at the moment and try them with some different equipment and see if that helps.

I don't know enough to be able to take a look at the crossover really and know anything about it and I also have no way of measuring to see if a capacitor is out of spec.

The song which probably sounded the worst was a track called elephants by rachael Yamagata. The vocals just didn't sound right at all. Then put on rivulets self titled album and it was great, probably the best I've heard it especially the track called swans.
 

Fatmarley

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I'd check to make sure the wiring is the same in both speakers
It'll probably be next week untill I have time to take them apart again to check all is wired ok.
I'd take a guess that the drivers themselves are ok unless the new foam surrounds have altered the spec of them.

I'll keep on with setup and positioning at the moment and try them with some different equipment and see if that helps.

I don't know enough to be able to take a look at the crossover really and know anything about it and I also have no way of measuring to see if a capacitor is out of spec.

The song which probably sounded the worst was a track called elephants by rachael Yamagata. The vocals just didn't sound right at all. Then put on rivulets self titled album and it was great, probably the best I've heard it especially the track called swans.
Had a listen to elephants on YouTube through my headphones and couldn't detect any problems. When you have one track that sounds great, and another that sounds terrible (when it shouldn't be terrible), that usually means a wonky frequency response.

New foams can change the frequency response if they're not identical to the original ones. Also, old electrolytic capacitors can dry out, so it may be worth replacing them.

It's possible one of the drivers is wired in the wrong polarity. You could listen to just one speaker (only to make it easier), and reverse the polarity of the tweeter, have a listen. If it sounds worse, or the same, put it back to how it was, and then reverse the midrange, and see what that sounds like.
 

MF 1000

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If there is a wammer near you with a umix mic and REW software they could help you sort any issues very quickly. Where are you in the UK ?
 

rab1991

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All good points, I'll check again next weekend unless I find some time during the week. I'll pull them out and listen to each one in mono aswell.

Someone with a mic would be great help and much appreciated. I'm in dy8 Wollaston.

Could you recommend any mic and software also so I can start looking into it.

Cheers