Is this going to work well? 2.5 way with dual woofers?

[edinm]

Hello friends,

Please can someone with more experience check is this going to work well and what result I can except:

I have 6 pcs of Faital Pro 8FE200 drivers:
https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=401030100

Also have this compression driver:

SB Audience BIANCO-34CD-PK​

Plan is to build tower speakers. Each will have compression driver from 2.4-2.5k
As a mid it will be 8FE200 with attenuation.
Dual woofers of the same type will be in 0.5 configuration.
All 3 woofers will share same box space with port.

Crossover will be 2nd order with 0.5 addition of only inductor for 2 woofers in parallel connection.
Box will be around 55 liters.

Is it too realistic to expect F3 at 40-45Hz?
Is it going to be nice speaker for hi-fi?
I have already these speakers and would like to use them in some way, don't plan to buy new speakers.

Thanks for any help!
Best regards

 

[AllenB]

So three woofers in the same box, one crossed to another and a third doing 0.5?

For starters, the mid is going to get pushed around by the other two.

 

[edinm]

No, one woofer is mid and other two are 0.5 but as parallel to raise output of lower end.

Compression 1" is for highs above 2.4khz.

Mu worry is these are mid woofers and I would like to make them play low enough for hifi.

 

[AllenB]

Where does each of the three cross?

 

[Sonce]

Context is missing - is this for professional sound reinforcing (PA), or for domestic hi-fi?
Essentially, all three midwoofers will be in parallel below 500 Hz (depending on the inductor value for 0.5), so the impedance of the whole system around 300 Hz will be about 2-ohm. You need a very good amplifier capable of continuously driving 2-ohm load. In that case, better solution is to have two midwoofers in parallel for fullrange duties and only one woofer for low frequencies ("0.5"), so midrange will not be subdued.
My recommendation: use only two woofers in parallel, ordinary 2-way loudspeaker. Vertical lobbing from woofers is not a big issue in PA. Or, make 2.5 system with only two midwoofers.

 

[edinm]

Speakers should be for hifi usage or HT. Thanks for your advices 😀

 

[Davor D]

If all three 8FE200 are working together at low freq. impedance will probably drop too low. Some modeling should be done to investigate this.
I strongly recommend you 3-way system. One 8FE200 as midrange-only in a closed chamber, and other two as woofers in a bass-reflex.

If you follow max. flat response alignment, it gives 70 liter volume for each 8FE200, tuned around 50Hz.
So, for good bass extension, 50 liters per 8FE200 tuned to 55Hz would be the minimum in my opinion.

 

[Sonce]

Speakers should be for hifi usage or HT.

Then, 2.5 system with only two midwoofers 8FE200. Closed box, approx. 50 liters total volume, well stuffed. Subwoofer is mandatory.

 

[edinm]

Yes, that was logical and probably beat option. BUT I don't have a sub and I was wandering if I can use aditional pair of these woofers to make litle more bass.

Option if also full 3way with dual woofers of same type. In that case one 8fe200 would be mid.

 

[Sonce]

It's about time to buy a subwoofer. Sell two of yours 8FE200, add some money and buy a subwoofer.
Even with three 8FE200 in parallel, you will not get the required low frequency extension.

 

[GM]

All 3 woofers will share same box space with port.

Crossover will be 2nd order with 0.5 addition of only inductor for 2 woofers in parallel connection.
Box will be around 55 liters.

Is it too realistic to expect F3 at 40-45Hz?

Hmm, 80 Hz Fs, Qes* = 0.66, Vas = ~16.147 L x 3 = ~48.441 L

Max flat vented alignment

Vb = 20*48.441*0.66^3.3 = ~245.89 L net

Fb = 0.42*80*0.66^-0.96 = ~50.1 Hz

F3 (Hz) = Fs*0.28*Qts'^-1.4 = ~40.1 Hz, so factor in +3 dB/stereo, some room gain and might get into the low 30s, high 20s, but at 55 L that's not enough for even a single woofer that needs Vb = 20*16.147*0.66^3.3 = ~87 L net.

*Qes is used as an approximation for Qts + series resistance:

https://web.archive.org/web/20220707003028/http://www.mh-audio.nl/Calculators/newqts.html

 

[planet10]

Is it too realistic to expect F3 at 40-45Hz?

On first blush 40 Hz is going to be difficult. F_s is more in line with a 3.5” woofer.

dave

 

[PeteMcK]

I suspect from 2x.5 woofers, you'll have too much output. I find that 3-4 dB is all that is required to deal with baffle step, so a single woofer is ideal (YMMV).
Given the high Fs, I'd look for a pair of more suitable drivers

 

[WhiteDragon]

Basically
Fs is 80 Hz
Once in a box that will rise.

So dont expect much below that
first impedance peak.

little speakers are good for mids
they dont do much below.....
well 80 Hz in this case.

Reflex alignment dont have much options.
be basically tuned around 80 Hz
So no interest in hearing that.

 

[chris661]

Some passing notes:

• I'm aim to cross lower between HF and MF. Compression drivers can run pretty low in home HiFi situations. The 8" woofers have very light cones, which mean lots of small resonances in the kHz range (look for bumps in the impedance chart), so rolling those off would be wise.
• An option which might be worth considering is something similar to the KEF 104.2: dual 8" 4th order bandpass covering <150Hz. The high Qts of the woofers, as GM has noted, will mean a very large ported box, but BP4 can probably help us here: it can tolerate higher Qts.
• These drivers are, overall, intended for high efficiency and relatively low cost. Good results can still be had, but they will be tricky to work with.
• Low-impedance concerns are valid. A 3-way design like the KEF I mentioned above would alleviate that, only dropping to 4ohm-nominal in the LF.
• If a sealed box is used, room gain might help to prop up the LF response. As always, I recommend EQ for dealing with room stuff.
• Don't be tempted by a Linkwitz Transform circuit, with the idea that you might gain LF extension that way. These drivers aren't intended to receive high-power LF inputs, and will likely produce more harmonic distortion than fundamental, when used in a small sealed box.

Chris