audio-talk

Thanks chaps, yes looks like there's a myriad of tweakery trials ahead.
Steve, interestingly my inductors are currently decoupled from the cabinets by err suspending them with string. It did occur to me that a steel screw in the mounting hole in the middle of the inductor might affect it, I guess I'd be alright using a brass one? Actually I'll fix it to veroboard when I'm happy I have the right value. I'll bear in mind lining the cabinets.
A sneaky borrow of your inductors would have been great Simon, thanks for the offer but as you say distance rules that out really.

As a first step today I have ordered .....some LPADs!

Small steps......

thomas wrote: ↑Sat Jan 27, 2018 10:42 pm That's an aweful pic of me, Dave!

..... I'm psyching myself up to acquiring a pair of something like a 7.5mH air core, at some stage....

Why does the inductor have to be a air core? These in my opinion are best suited to HF filters and ferrite core best for bass filters.
The air core must be baked to fusion bond all the windings. Not all air cores are. Some rely on tape to hold all the windings together and heat can make adhesive tape debond and so the whole inductor windings will come loose and affect performance.

Why not try a transformer core coil such as the likes as these: http://www.monacor.co.uk/categories/tra ... nr/125480/.
They are 8.2mH with a low DCR of only 0.17 ohms. Wire dia is 1.4mm and rrp = £25.57 + VAT each. Amazon online price = £29.10 including free UK postage.

Here is a Jantzen air core equivalent https://www.hificollective.co.uk/catalo ... -coil.html. However the DCR = 1.1 ohms, and the price is retail £33.59 + VAT + postage from HFC.

Note the difference in the DCR. To get this anywhere near the transformer core inductor DCR you would have to go for 2mm dia wire and that is going to be big and expensive. Jantzen do a fine range of air core baked inductors that I rate highly and use myself now in all builds. But the Monacor transformer core inductors are also highly regarded and I have these on my own OB project to good effect.

I think the reason James used air-core for this is that in the series crossover, the choke is more 'in the circuit' at Mid and HF than in a parallel crossover. I expect he tried it with a cored choke first. You are definitely correct about the wire size for DCR though , I think they are 2.5mm^2 wire.
However I definitely think ( and said before ) you're right that Thomas should try a transformer-core choke, there's probably only a small difference between that and an air-core.

I use Amorphous core from AE for my OB's

Hmmm interesting....

I did briefly try a pair of Hammond 10mH 5A chokes I had to hand, probably not the last word in finesse... I didn't like the quality of the bass- rather 'overhangy'.However maybe I'll have another try....

What cap sizes did you try ?
If the cap is more than about 20% away from optimum for the choke & drivers it'll sound poor & sluggish. Something around 150uF will be required , maybe more - the cap size goes up as the choke size goes up. In fact given it's an 8R mid driver it might be nearer 200uF .

I've whacked the 10mH Hammond choke back in and funnily enough I've just upped the cap to around 130uF (from 90uF), which thanks Mark did seem to make bass and treble 'gel' a lot better.
The Lowther needed some serious 'padding down' (5R ish) and although I'm a little dubious about the Lowther's sub 150R abilities it's a pretty good sound all round, prob better than the best of yesterday's (sorry DTB!) and a sound I think I'd be happy to take to Owston.
Thanks for the info on those Monacor inductors Colin, they look pretty tempting, I'm wondering about the 8.2 or even a 5.6 to raise the crossover a bit, the latter crossover point might add some colouration (heresy!) and disguise the Lowther shout....
It's all good fun...

Mark, just noticed your recommendation for a 150uF+ size.... I'll have another play....

thomas wrote: ↑Sun Jan 28, 2018 7:43 pm ....s it's a pretty good sound all round, prob better than the best of yesterday's (sorry DTB!) ....

Right! Thats it, I'm sending in the next sound consultant

thomas wrote: ↑Sun Jan 28, 2018 4:07 pm Hmmm interesting....

I did briefly try a pair of Hammond 10mH 5A chokes I had to hand, probably not the last word in finesse... I didn't like the quality of the bass- rather 'overhangy'.However maybe I'll have another try....

Could've been additional DCR meaning the amplifier is no longer damping the LF movement (much).

With your ear close, tap a speaker cone. You'll hear it ring at a low frequency. Connect the terminals together and tap again - most if not all of that ringing will be gone.

Chris