1970's TL remake help

[webby]

Hi All,
Due to family life my large Open Baffle speakers have to go.
I am going to try remaking these 1970's Cambridge Audio R50 copies.
They have the usual Kef 3 way drivers. and the cabs are in good shape, except for the front baffle. They need to be remade so i was thinking I would keep the B139 for bass and the use some TC9FD-18-08 for mid, and better tweeter, keeping them a three way.
I have 2x4 Mini DSP and Umik Mic and a few different amps.
The baffle are recessed about 15mm into the cabinet and must have a negative effect on the sound, and against current thinking. I have some 33mm Formica birch ply that would flush mount nicely.
I have been using the Vifa TC9FD-18-08 and am impressed, so would like to continue using them.

Would you put the vifa TC9FD-18-08 in the current Mid enclosure that is within the cabs, or would it be better to locate the mid and tweeter drivers closer together and ear height, any thoughts?
What about removing the Mid enclosure, might be an opportunity to improve the TL?

Any thoughts on using the other mini DSP channel either the TC9FD-18-08 or the tweeter? I will need to used one with a passive crossover.

I have a pair of Vifa D25AG-05-06 on hand, or maybe better to use a smaller tweeter to get close spacing to the TC9FD-18-08.

Here are the design details and photos.
Any help or suggestions, I would be very grateful.
Thanks
Ian

 

[multisync]

I have and still use the same speakers. I took then to a local diy audio event a couple of years ago and the general feeling was they sound pretty da#* good for 40 year old speakers.

 

[webby]

I like how they sounded but they are not very good at imaging / sound staging, and I'm coming from open baffle that are excellent in that regard.
Trying to minimise the step back to boxed speakers.

So, any ideas?

 

[webby]

Can anyone help make a guess if it would be better to put the TC9FD-18-08 in the existing mid enclosue, its about 9.8 litres.
Just not sure if it will sound good in that low down position, I'm used to them being at ear height.

Any suggestions please?
Many thanks
Ian

 

[system7]

webby, I think you have this all wrong. You can't replace a 5" mid with a 3.5" fullrange one and get enough loudness.

Looks like a Celestion HF2000 tweeter, if not KEF T27, and a B110A or B midrange.

I don't think you can go far wrong to get it back to original spec. Bit of a research project, but Falcon Acoustics and Wilmslow Audio offer off-the-shelf crossovers for this model, IIRC.

The old B139 bass is getting a bit long in the tooth, IMO. With a conveniently removeable baffle, you can surely fiddle around a bit on more modern basses.

What I would do, is trace the crossover for your 3-way unit. Maybe consider getting back to 4-way with the still available Coles supertweeter.

Schematics are still available. This will be a labour of love, but I think doable. I wouldn't think it is rocket science to use a more modern mid as well. The Peerless 830860 can't be way different. Peerless HDS PPB 830860

 

[boswald]

If you need more output, or want a closer to drop in shape, Peerless has brought back the alloy frame version of that shape(over here PE has it- look up 5 1/4" Classic).
Easy to use- look at that response graph.

The only way to make a 3.5 work here is to go mtmw, double 'em up to get max spl.

 

[system7]

Boswald, you are a wise old cove. It is, of course possible to replace a big mid with two smaller units.

This was done before in the Celestion 25 and the Wharfedale E70 below.

Both fine speakers. Thing is you gain 6dB loudness from doubled drivers. Which reduces distortion.

IMO, speakers are all about the mids. Voices if you like.

Here's a fun way of doing things. The dispersion of the woofers matches the ribbon tweeter:

It's not all about frequency response. Room acoustics and dispersion comes into it.

 

[drewan]

Falcon acoustics were and could still be selling the B110, celestion and coles drivers, as well as crossover kits

 

[webby]

Thanks for the ideas so far.
When I had them setup as standard they lacked bass in my room, they also didn't do the sound stage / imaging thing very well. The baffles might be to blame not being airtight, the t nuts have chewed the chip board, it may be the crossovers, I'm not sure. Didn't want to spend much cash and wanted to utilise what I have.
So a new baffle / drivers and 2 active channels out of three sounded fun.
Would two tc9's in the mid enclosure work?
Many thanks
Ian

 

[boswald]

Take off the baffle, measure the insides, and give us a photo. Then we'll see what can fit where.

 

[phivates]

Maybe some diffraction treatment will help with the boxy sound, but the bass is an old school end loaded TL which will have peaks and nulls unless so heavily stuffed that you get no output from the vent. Still, I would have them. A classic for old school TL guys like me.

 

[TMM]

webby, I think you have this all wrong. You can't replace a 5" mid with a 3.5" fullrange one and get enough loudness.

If running active the difference in sensitivity shouldn't matter. What does matter is how low you want to cross it and what listening level you want to achieve from the system. The TC9 and TG9 are some of the better 3.5" drivers in that respect; 350-400Hz LR4 should be no problem at elevated listening levels.

Even if running passive there are 3.5" drivers which are quite sensitive (~85-87dB/2.83V/1meter). The Vifa NE95W and the metal cone Tang band W3s are a good 3-5dB more sensitive than TC9/TG9s. Timothy Feleppa's Pages

 

[webby]

Take off the baffle, measure the insides, and give us a photo. Then we'll see what can fit where.

Hi All,
Removed the baffle and rear panel so you can see how it relates to the article drawings, looks well made, very much better then I could manage.

Any ideas then?
Many thanks
Ian

 

[webby]

If running active the difference in sensitivity shouldn't matter. What does matter is how low you want to cross it and what listening level you want to achieve from the system. The TC9 and TG9 are some of the better 3.5" drivers in that respect; 350-400Hz LR4 should be no problem at elevated listening levels.

Thanks for the info, I don't really get much of a chance to play loud these days, small people asleep upstairs, so not really worried about party levels.

Is the Mid enclosure position a problem, seem very low down?

 

[phivates]

You could make a new front baffle and fit it to the back, making a tighter mid-tweet spacing possible. Would need a potted midrange or two. Yeah, that's the ticket: 2 TC9s and a Morel MDT12.A new tweeter would make the extra hf driver unnecessary. One of the forum modelers could sim the lf behavior.

 

[chrisb]

Unless the crossovers or any of the drivers are trashed, I'd be inclined to keep as close to stock as possible, and if you want to flush the baffle, simply add additional batten /spacers, refurbish the baffle with a skim coat of bondo filler and re-paint, and maybe a new grille?
Cutting an all new front baffle by hand will be rather a lot of work - particularly for the B139.

 

[phivates]

Sometimes I forget that my toolkit is a bit beyond that of the average non-carpenter/woodworker.

 

[suzyj]

TG9's are lower distortion than TC9, drop into the same cutout, and not much more dough.

 

[LineSource]

If both KEF B139 woofers are in good condition...

You could save your DSP for a future no-compromise new set of speakers.

Build a passive crossover for a modern 5"-6" midrange and your D25AG-05-06 tweeter which blends with the KEF B139 TL with their current crossover. Keep-It-Simple 3-way speakers. You want the tweeter at seated ear level with the new midrange butted below... so you will need to patch baffle holes and re-route for the new drivers. On a flat baffle the phase shift difference between BW3 for the tweeter and LR2 for the midrange helps compensate for the time alignment difference. Give consideration to a wide bandwidth poly-plastic cone midrange on this large baffle.

 

[chrisb]

Sometimes I forget that my toolkit is a bit beyond that of the average non-carpenter/woodworker.

Soon to be retiring from over 25yrs in a commercial millwork shop with some pretty damned fancy toys and over 500sq ft of personal work area, that's a very easy factor to overlook.

Not to put a damper on the project, I'll repeat that if none of the drivers are damaged, I'd be inclined to consider maybe upgrading any EL crossover caps, refurbish the baffle and add spacer cleats to remove the recess and enjoy. Much more than that would require complete re-engineering of the system and possibly some painful reconstruction of the cabinets themselves. Some folks might well consider these a vintage classic worthy of restoration rather than renovation.