My take on FAST With TB- 1139SI and PS95-8

[hatemii]

Hi. My plan is to build two way speakers using Tang Band 6.5 inch 1139SI subs and possibly Dayton PS 95-8 as a widebanders. I have started on building the cabinets from 15mm birch plywood. Internal dimension of the cab will be 17cm x 32cm x 37 cm which gives roughly 20 liters of total internal volume.
I have a plan of using a 32cm long 110mm round pvc pipe as a cabinet for the midrange. That would take bit over 3l of the internal volume leaving me with 17 liters of volume.
Front firing and folded slot port of 2cm x 17cm dimensions would also take around 3 liters of the volume.
That would be 14l before the driver is taken in the calculations.

I have few questions tough.
First is about the driver and port placements. Will it matter if the port is at the bottom of the cabinet and drivers are at the top, placed as close together as possible?
Would it be wise to leave the midrange housing open to the outside on the back? Or would that cause some peaks and dips to the reponse because the front and back of the driver are roughly 80 cm apart from eachother?

I will be using Mosconi D2 100.4 amp/dsp.

 

[xrk971]

PS95-8 is a good driver. But for about same price Vifa TG9FD10-8 measures and sounds better. Instead of a round tube for mid make a tall 3 sided pyramid or Dagger - sounds very open as there are no parallel walls. Look in this thread for how I did my fast - similar size as yours but with 8in woofer.

http://www.diyaudio.com/forums/full-range/273524-10f-8424-rs225-8-fast-ref-monitor.html

You can make Dagger open on the tail and stuff to make aperiodic TL. Works well to flatten impedance peak.

Keep full range as close as you can to woofer circa 8in ctc but if you cross at 500Hz or below you will be fine.

Think about transient perfect XO's. They sound better.

I tried many different ones but ended up liking the Harsch XO best.

 

[hatemii]

Thanks for your reply. The reasoning behind the PS95-8 is that I alreay have them. I might change them later on to something better tough. Same goes with the TB. Exellent subs but not that good on the midrange so I will need to use pretty steep slope on the XO. And posibly low XO point.

 

[hatemii]

BTW do you think rockwool sheets would work as damping material inside the cabinet. I can get hard roofing sheets in 20-50mm thincknes and slightly softer sort in 50-200mm thicknes. I can also get softer rockwool in different thicknes.

The intrest in those materials comes from the fact that I can get those for free ;-)

 

[xrk971]

Rickwool is excellent damping material. Better than polyfill or fiberglass.

 

[hatemii]

So which would you use? The dense one that squeezes only few % or the soft one that you can squeeze with your fingers from 50mm to 10mm?

 

[xrk971]

So which would you use? The dense one that squeezes only few % or the soft one that you can squeeze with your fingers from 50mm to 10mm?

Soft. Dense one may act as partial reflector still.

 

[hatemii]

Soft it is then.

I started to consider on making sealed box for the TB. My DSP has a possibility to boost the low end so I could get reasonable low end extension with better group delay compared to vented box. Both sealed and vented have their own ups and downs I suppose.

 

[hatemii]

Ended up with a closed design. It turnedout that the dagger housing for the mid takes so much space, that there is very little room for the port. And I had a small error in my plans so I would have had to cut the front and bottom parts again to make the slot port look half decent.

 

[xrk971]

Ended up with a closed design. It turnedout that the dagger housing for the mid takes so much space, that there is very little room for the port. And I had a small error in my plans so I would have had to cut the front and bottom parts again to make the slot port look half decent.

Sealed is the way to go if you have enough cone xmax. Use Linkwitz transform if you have DSP EQ available. The group delay improvement with LT vs BR is significant.

Now when I listen to bass reflex it doesn't work for me at all. Just to sloppy.

 

[hatemii]

I think 13mm xmax is sufficient for some boost down low.

This is where I got so far. Dagger is made from 6mm plywood and assembled with hot glue and pu-glue. I will cut them bit shorter since they wont fit inside the cabinet. I might also cover them with 4mm bitumen membrane to damp the resonances.
I will also make some cross braces to stiffen the cabinet even further.

 

[xrk971]

Looking great! Thanks for trying the Dagger.

You won't regret it - it is the simplest least material cabinet that has zero coloration. Don't forget to put stuffing in it.

 

[hatemii]

The project continued today. I glued the baffles to the cabinets and started building the amp board.
Daggers are damped with 4mm bitumen and most of thw cabinet walls are covered with rockwool.

 

[xrk971]

Looking good. Don't forget to put stuffing inside the Daggers. What kind of amp is that? Is there DSP xo?

 

[hatemii]

I'm going to put polyfill inside both cabinets.

The amp is Mosconi D2 100.4
4x100w and built in 6 chanel DSP.

http://mosconi-system.it/product/gladen-d2-100-4/

 

[hatemii]

Minor setback. That SMPS makes infernal noise. I will have to change the fan to something quieter to make it tolerable.

Btw noticed that my current tpa amp has terrible background noise when the volume is set high. It does not matter if the mini plug is conneced or not. I guess you can't get all with 14€ amp.

 

[xrk971]

Btw noticed that my current tpa amp has terrible background noise when the volume is set high. It does not matter if the mini plug is conneced or not. I guess you can't get all with 14€ amp.

I have used dozens of TPA3116's and none have that noise. Sounds like you may have a ground loop or bad input shielding issue.

 

[hatemii]

Those daytons sure are bright. Still top heavy even with -5db on them.

XO LPF 300HZ LR 24db and HPF 350HZ LR 24 db. Low shelf boost of 5db at 30HZ.

 

[xrk971]

The Tang Band is 84dB at 1 watt but it's a 4ohm driver, so at 2.83v it will be closer to 87dB. The PS95 is 85.6dB and it is 8ohm. The width of your cabinet is pretty narrow so expect circa -6dB baffle step loss in bass for 81dB rough level of sensitivity at 2.83v. Thus the PS95 will have to be padded down by 5.6dB or circa -6dB if not -7dB to sound balanced with the bass. You might want to try a -5dB low shelf at 900 Hz and Q=0.5 to provide the BSC for the PS95. Then adjust the levels to taste.

Looking good though - listen to it at 30 deg off axis and it will sound very much more balanced than on axis.

 

[Cal Weldon]

The Tang Band is 84dB at 1 watt but it's a 4ohm driver, so at 2.83v it will be closer to 87dB.

I think that's wishful thinking there X. That TB driver is a great little unit but it eats watts for breakfast. I have only been able to use it with it's own amp. A standard 2 way is a tough go. Hatemii might need to consider a plate amp and bi-amp the system.