Adding woofers to a 2way

[yurgs]

I am looking for DIY suggestions for extending my 2 Way Speaker (Prestigeous2 Monitor, audioexite) with an active woofer each. I would like to stick to the front panel of the 2way to keep the passive x-over between mid/high.
The MT section will be driven with a tube amp (a KT88PP, about 50W) and the woofer with the 300W from chocoholics Liteamp. To explain better what it could look like I drew some pictures.

An externally hosted image should be here but it was not working when we last tested it.

The cabs offer ~ 19l for the mid/high and 56l for the woofer but the size could of course be changed.
With the added flexibility of an active xover or dsp for the woofer section it can compensate phase of the woofer and should be adjustable to different 2-Way combinations, and it leaves me with the option to upgrade to a different 2-way design later on.

How do I select a matching woofer?
Preferably 4r, and max 12” to fit the cabs and I would love to use some European made drivers.

I compared some drivers with WinISD and then I tried to simulate some different drivers with Boxsim and what looked good in a simulation was the Scanspeak 26w-4558t00.

but how do i include the effect of room gain into the design?
what else to look out for?
any help is apreciated!

 

[Lojzek]

Hi, the matching woofer is any woofer of reasonable specs with regard to its TS parameters to achieve a satisfactory response in a certain volume of a vented cabinet at a certain power level.
Get yourself Jeff Bagby's Excel spreadsheets:

1.Response Modeler
2.Diffraction & Boundary Simulator

 

[yurgs]

Thanks for your response Lojzek,
the scanspeak 26W/4558T00 seem to be quite good especialy for the size and the price.
Do you think a 10" woofer is enough to supplement a 6.5" midwoofer?
if i go the next size up, like with the 28W/ the price almost doubles.
i will check out the spreadsheets you mentioned,
cheers!

 

[Lojzek]

26W 4558 T00 surely is up to the task, providing you with very deep vented bass loaded by a rather unstandard port size, Fb=25Hz calculates to a 4"x24" port, F3/F6/F10=25/22/19 Hz.


There is an exceptionally nice offering of Visaton TIW 200 XS at:
Tieftoner VISATON TIW 200 XS, 180 W online kaufen | Pollin.de
which I'd be tempted to use as two units instead of one larger Scan Speak. I imagine a nice dsp amp for these and a mild linkwitz transform for F3=30 Hz.

 

[yurgs]

Thanks for the suggestion,
i checked with the scanspeak spreadsheet and i got max. vent speed (with a 3"port at about 11" length) is 7.5 m/s.
am i messing it up somewhere?

i added the 2 visaton TIW200 to a quick comparison in winisd and boxsim, but i dont know how do add a linkwitz transform
but they dont look as good when i stick to a volume <60l
Visaton is turquoise
26w green
28w red

 

[Lojzek]

Values you get are probably alright for the defined power level. I am using spreadsheet "Woofer Box and Circuit Designer". There you can try out Linkwitz Transform's. TIW 200 XS are meant to be sealed in less than 60 litres box and then equilized, if at all needed. Cone excursion looks better for one Scan Speak vented than for two Visaton's sealed, at 150W.

 

[yurgs]

I spent some time figuring out how to simulate Linkwitz T.
and it is quite interesting.
there are two basic things i am not so sure about:
1: how to choose a driver for a cab with LT: i am not quite sure what parameters to look out for, from my understanding cone excursion and power handling seems important. and do i look at linear excursion or mechanical xmax when checking the sim?
2. how to decide on cabinet volume when using LT ? is there just try an error for determining a size or can it be calculated?

 

[Lojzek]

You ought to try out any enclosure volume and LT setting that lets you achieve frequency response you find most suitable to your needs. At the same time you are evaluating what happens with excursion (Xmax) or any other performance parameter. You don't need a formula to tell you what you need.

 

[yurgs]

here is a sim in Basta! since i can add a LT, and it has the possibility to add room gain to the system.
It shows my mid/tweeter response, i added the woofer and i tried to extend the frq via LT down to 20Hz, Q0.7, and chose a Box volume of 35 l (vs. the 52 l i used for the vented box).i set input level of the mid/tweeter to 60W and the input level of the woofer is set to match the curve (this as at 15V, or 56W?). somehow i thought i need more power for the woofer.

 

[Lojzek]

Your simulation does not seem to take into consideration the LT boost which in my sim calls for +14 dB to get F3=20 Hz in 35 litres sealed. I've used Hobby HiFi measurement of the 30W 4558 T00.

 

[Rob41]

Is this the design you are looking for or are you just wanting to bolster your bottom end?

If the latter is the case, and very much from a performance standpoint, a separate sub to augment the bottom end crossed at 80Hz would be very easy to incorporate into your system.

 

[yurgs]

Hello Rob,
i like the idea of a florstander with an active bass. basically the only difference is that i have two inbuilt woofers instead of one in an external sub.
it should be just as easy to incorporate.
the difficulty for me is to find out which cabinet to build, and i would like to get my head around the simulation of it.
The design process should be the same,
i need to decide on a driver and figure out if its spl (within its capabilities, power handling and cone excursion) matches the rest of my system.

hello Lojzek you are right, somehow the LT doesnt make sense in my sim.
i tried again with unibox.
i added the driver, box parameters and get aFb 43,9 and Qtc 0,96
Adding these in the trueaudio excelsheet i can export the linkwitz response correction .frd and import this back into unibox.
this gives me a graph now for the driver with the LT.
I can also export the driver response and import in basta and i get the overall system response at 1W with room gain.
does this look better?

 

[Lojzek]

Now this looks to be correct like a sim I did in Woofer Box and Circuit Designer.

 

[yurgs]

thanks,
its much more fun to experiment with different drivers when the outcome makes sense.
i just tried a few diffenrent drivers and found an interesting one.
Focal P30F,
nice looking driver with higher excursion and max. power, slightly less eficient though. a bit cheaper than the ss 30w as well.

 

[Lojzek]

I'd rather choose this one over the usual hi-fi overpriced units.
Tieftoner KENFORD PA 380 mm L385050-8B, 8 Ω online kaufen | Pollin.de

 

[TMM]

I would not worry too much about room gain. In real life it is rather chaotic with multiple peaks and nulls, nothing like the 'room gain approximation' in the sim. Having two subs and active crossover puts you in a good place to tune out as many room problems as possible.

 

[yurgs]

Yes,
i know there is a pricetag to everything produced in europe but i think it is hard to find a company that will openly report about their manufacuring conditions in asia and probably for a reason....
there are more PA-speaker brands but they usually dont produce subwoofer drivers with high xmax and low Fs.
some car hifi brands but usually a a crazy price..

@TMM, i agree, its nice to be able to compensate the room problems in the end, but i thought it would make sense to take at least some effect into consideration when playing with different drivers in sim.

 

[yurgs]

I also tried a sim with BMS 12N630 and Faital 12HP1030 and both would be an option. the BMS spl@250W is identical to the Scanspeak@300W but is slightly above it's Xmax in a closed box with LT.
The Faital does well, but the Scanspeak 30W looks still the best i think.