HiFi Subjectivist ¦ Audio Forum ¦ NVA User Group

The midrange is an audax polypropylene with its own seperate enclosure.

I didn't want it to try and reproduce the lowest frequencies and with an inductor used I may as well use a cap.

Also doping is irreversible and so first things first.

Daniel Quinn wrote: ↑Mon May 04, 2020 8:13 pm ...doping is irreversible and so first things first.

Sounds entirely reasonable.

Also worth noting that doping is far from an exact science and it would be very easy to apply too much.

Sorry to the OP this has gone off topic.

I can see the advantage of filtering the low frequencies from the mid range to improve the mid range purity. Also some dedicated mid range drivers will not but suitable for doping. In my case i use the 5.25" mid bass for mid range (as recommended by RD) which are of course very suitable for doping. They help my isobaric 12 "with baffle step bass losses.

I find te doping a very interesting and rewarding exercise. Add a lttle (measured amount for each driver) at a time and then listening at every step. With up firing drivers you can even listen whilst it is drying . Going too far would require a change to the capacitor (but don't want to lower the tweeterfilter knee too much) and or resistor on the tweeter. If that did not work then the driver would have to be junked. But a lesson learned.

It's all a big trade off. Swings and roundabouts.

No need to apologise for the thread going off topic, it’s been an interesting read!

So I’ve got the Magnum K2 with the doc mod drivers and I’ve got a desire to make something with bigger drivers. I love the idea of an open baffle with 15/18 inch bass drivers, but I doubt I could give them the space they require... but I might have a go anyway! As far as the Magnums go I’ve ordered a pair of closed back midrange drivers because I feel as though the doc mod ones are being affected by the bass drivers. I may top mount the new driver and even look into adding side firing tweeters.

It definitely has been an interesting read. Good stuff.

karatestu wrote: ↑Mon May 04, 2020 7:03 pm

Docfoster wrote: ↑Mon May 04, 2020 5:45 pm

Daniel Quinn wrote: ↑Mon May 04, 2020 5:31 pm Currently I'm using modified wharfedale dovedale. Scans peak tweeter with just a cap. Audax midrange with a 100uf cap and an inductor and the original 12inch bass driver which is doped.

So a bit of both?
Similarly, I've left the woofer running full range on my Magisters. But to my ears it contaminates the midrange. I feel a bit purist about the old gals tho so I leave it open. Could dope the woofers further, but IME whilst doping does seem subjectively to trim down the top end of a driver's active range (which in this case is what I want), it also reduces the overall sensitivity which in this case I don't want, as the bottom end is spot on.

If the bass driver was pointed in a direction other than directly at the listening position (e.g upwards) then maybe you could get away with leaving it running full range.

It's possible. I haven't tried it with larger drivers.

Here's something that will really annoy some people here.
I've spent a lot of time working on and listening to 70s Goodmans and Wharfdales. But I've always wanted to try out some old Tannoys. I've managed to get a pair of vintage Tannoy Eatons (10 inch HPD 295A drivers).
Here they are plonked on top of my DIY 3 ways.



I fitted some new binding posts to the Eatons as their original spring loaded binding posts couldn't accommodate anything with a diameter larger than a human hair.
The Tannoys sound good. The compression driver tweeters deliver more dynamism than I'm used to. So a useful addition to the collection.
Also it occured to me that it would be fun to give the Eatons a bit more grunt down below. So (and here comes the shock) I rigged up a secondary external crossover to send <75Hz to the big 18 inch Goodmans 18P woofers in the speakers below. So the system now has double crossovers! Those inductors are huge. (I can control the level either side of the external 75Hz crossover point with a digital shelf.)



Be assured that this arrangement is more about fun than fidelity. It can deliver some pretty awesome bass though.
And, the soothing news is that I'm planning to build closed cabs with simplified crossovers for the Tannoy HPD 295A drivers.
The HPD 295A drivers are easy to take out (just 4 bolts and an 4 pin connector), so switching the drivers between 2 pairs of cabinets as and when I want a change will be no biggie.

I've been able to make progress with the new sealed cabinets for the Tannoy 295A drivers this week.
25mm MDF all cut to size. Will assemble tomorrow.
Spent today building the (very simple) crossovers. The old style 4 pin connector to the 295A drivers will make it easy peasy to switch them between their original (ported) cabinets and my new DIY sealed ones.

Docfoster, did you consider using 3/4" plywood instead of the MDF? And if so, what made you choose MDF?

Lindsayt wrote: ↑Sat May 23, 2020 10:09 pm Docfoster, did you consider using 3/4" plywood instead of the MDF? And if so, what made you choose MDF?

Good question.
Yes I absolutely did think of using plywood. In fact, that's the ultimate plan.
I want to try a double plywood sandwich. I've read it's a good approach (https://www.pinkfishmedia.net/forum/thr ... rs.237172/) and want to give it a go.
I'm currently doing an FdA Fine Arts course and have access to a really good 3D work shop at college (loads of good wood working tools) that would enable me to to a proper job with the double ply, which I imagine will be tricky without a workshop. BUT college is locked down. So I can't get in.
The MDF cabinet is just a cheap and easy stop gap I can do at home.
But yes, once I'm back at college I will try the double ply.
So I suppose I'll end up with 3 cabinets for these Tannoys!