Old Audax 3 way

[pablo7]

Hello folks I’m new here and from Bonny Scotland. I have been reading your forum and it is an amazing source of info. When I was a kid (I’m now 37) I bought am old set of Goodmans havant XL’s from a junk shop with my pocket money all the units were destroyed so I replaced them over the course of a year with Audax drivers, for me at the time they were really expensive. Since I was so young I didn’t bother looking at response frequencies or anything and at the time I felt they sounded good. I’ve hung onto these speakers for sentimental reasons and now want to make them work properly. The units are

Audax tweeter TW025M1 1 inch dome
Audax full range HT210A2 8 inch
Audax Mid/bass HT170F0 6 ½ inch

I’m stuck with the Goodman’s enclosures but I have put a new front baffle on as you can see in the picture. I’m planning on putting together crossovers for these but before I do that what do you think of these units. I have been using the Full range as a mid which needs attenuated, however I’m now thinking or replacing the full range with proper woofer and using the HT170F0 as the mid.
Any insight would be much appreciated
Thanks
Paul

 

[Lojzek]

Hi Pablo, I'd remove the full range unit for a separate full range project and proceed with the rest of the drivers to make a 2 way. Vented 20 litres looks promising in regard to your Goodmans enclosure.

 

[pablo7]

Hi Lojzek,

Many thanks for your reply. That is probably what I'll do - I have often wondered though if the Mid/bass HT170F0's get down low enough for decent low frequency response? Do you think in your experience they are passable or is it worth swapping them for a dedicated woofer?
Thanks again though 🙂
Paul

 

[Lojzek]

I would certainly think yes, it is decent enough of a midwoofer for that. 50 Hz is 50 Hz. Once you start swapping units for better ones, there is no stopping until you swap the whole thing and then you're in trouble. Keep the enclosure, simulate vented response with TS parameters as defined by Audax and deal with the hardest part of the equation (XO filter) the best you can in the way it suits you most.

 

[pablo7]

Thanks a million Lojzek for your help. I'll be back when I'm ready to built the XO. Have a good day 🙂

 

[6thplanet]

I think you'll be quite happy with a two way containing the 6.5" and tweeter as a two way. The spec sheet gives enclosure volumes for different roll offs. If your box has the volume required for Vb1 solid line, you'll be half way there. The other half is working out a proper crossover to make the drivers play nice with each other. Good luck!

 

[pablo7]

Thanks 6th planet. The box is closer to 20 litres will that still be OK in terms of the woofer roll off? Also with the given tweeter the million dollar question, what frequency would you crossover at?

Thanks again
Paul

 

[Lojzek]

A Qts of 0,4 is suited well to the cabinet volume equal to Vas parameter. When the time is right, I'll simulate the response and XO based on the papers you provided and the measures of a baffle and driver position ( that you will supply when you decide how your new baffle comes out). Will be good for starters.

 

[pablo7]

Thanks Lojzek - much appreciated. In terms of the new baffle any recommendations. I was thinking keep it simple driver in the middle tweeter at the top and port at the bottom.

 

[Lojzek]

No problem, whatever you find appealing.

 

[pablo7]

Hi Lojzek, I've managed to replace the baffle - not fixed in completely as you can see by the pictures. I've not made a Port hole yet as I was wondering if that would affect your simulation, but it will be under the woofer. I was thinking of a 3 inch ID Port, (too Big?).

Current enclosure internal dimensions - 447mm (hight) x 227mm (width) x 202mm (depth)

Woofer (170mm diameter) - 120mm from bottom and 160mm from top. 30mm from the sides.

Tweeter (100mm diameter) - 24mm from top 327 from bottom. 65mm from each side.

big thanks again
Paul

http://www.diyaudio.com/forums/members/lojzek.html

 

[LightBit]

3 inch diameter port would probably be too long to fit in enclosure.

I would remove the edge (baffle diffraction).

 

[6thplanet]

According to the Audax literature, the port will be 5cm (~2") x 6.3cm (~2.5")

 

[pablo7]

Thanks LightBit - Yea I just noticed the the length would be too long for 50hz tuning frequency. Interesting point about baffle diffraction - you mean the raised edge round the front of the speaker?
Thanks
Paul

 

[pablo7]

Hi 6th Planet - I take it bigger the better so 2.5 inches would be ideal. i was looking at an adjustable port.
https://willys-hifi.com/collections/reflex-ports/products/bass-reflex-tube-adjustable-large-size
Just over 2.5 inches at 2.59. so would be Just over 6 inches in length,

 

[Lojzek]

I've not made a Port hole yet as I was wondering if that would affect your simulation, but it will be under the woofer.

Port location is not a problem, I'll have a look what figures I get from a simulator but 2" of port diameter is plenty.

 

[pablo7]

Great Thanks Lojzek

 

[Lojzek]

It bothers me that at the bottom of the specification sheet of the units it says that the measurement conditions are defined on pages 15-19. It also says that the driver was in the Vb ref volume of 15 litres with the response probably spliced to the infinite baffle response. The main woofer FR curve looks as if the baffle step response is already recorded within but the SPL level does not reflect that for it is set at reference sensitivity value. So I'm kind of reckoning that the main response by Audax should only be lowered down to about 85 dB and use that as a simulation curve. Does anyone have any opinion on this issue? I would rather not simulate anything without being 100% sure that I am not missing anything important.

 

[Lojzek]

I figured this one might be a good starting point considering. If you decide to proceed, see if you can reduce or increase (6R8, 8R2, 12R) the padding resistor to your liking. Simulation says port is 2" by 3".

 

[GDO]

TW025 has an axial rising response which is more a feature than a flaw and i would certainly not try to correct this by eq at xover level...

All tastes are in nature though...😎