SB Audience 12MW200 Back loaded horn?

Hi everyone

This is my first post.
I have done a couple of speakers designed by others.
Now i decided to build my own 2way from scratch.
Drivers:
https://www.sbaudience.com/index.php/products/woofers/bianco-12mw200/

https://www.sbaudience.com/index.php/products/compression-drivers/rosso-65cdn-t/

The CD is to be mounted on a Yuichi 480 (ø35)
Crossover point is not decided yet, but around 600-1000hz

And here is my question:
Will it make sense to build a backloaded horn cabinet for the woofer, and is it even suitable for backloading?
I hope the woofer Will hit 35hz at F8 in vented cab, so thats fine for me.

Maybe the BLH could bring the woofer closer to the CD in sensitivity.

Thanks in advance!

Thomas
 
Yes, assuming there's no high output impedance to significantly raise effective Qts since the box only loads the driver to its upper mass corner (Fhm) where T/S theory peters out:

upper: Fhm = 2*Fs/Qts'

lower: Flc = Fs*Qts'/2 (AFAIK normally only used for reactance annulled BLHs)

Qts': 2*Fs/Fhm

Fs: Fhm*Qts'/2

(Qts'): (Qts) + any added series resistance (Rs): https://web.archive.org/web/20220707003028/http://www.mh-audio.nl/Calculators/newqts.html
 
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You might check papers 7 & 8 of Martin's theory section.

IMO, you should not just blindly use the web calculators w/o also doing sims because these topologies are a continuum from shorter ducted reflex boxes to enormous serpentine ducts (and people call them all backhorns).
 
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Ditto MLK's as his design theories are so technically correct that they take all the 'fat' out of TLs in general and especially BLH designs, though a plus for those folks with (very) limited space, stringent design limitations.

Because they technically are if there's any positive taper to its terminus. 😉
 
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Thank you everyone for your inputs! I know nothing is simple, but i guess your answer opened my mind to a more theoretical world. Im still a novice in speaker building, and this maybe to advanced for me for now 😄 And my wife isn’t happy with 200litre speakers in the livingroom, yet!
 
The CD is to be mounted on a Yuichi 480 (ø35)
Crossover point is not decided yet, but around 600-1000hz
Will it make sense to build a backloaded horn cabinet for the woofer, and is it even suitable for backloading?
I hope the woofer Will hit 35hz at F8 in vented cab, so thats fine for me.
With the BIANCO-12MW200 mid-woofer's Fs of 51 Hz, 35Hz will be more than 8dB down in a vented cabinet.
It could work in a back loaded horn, but would need to be huge to reach 35Hz.
Maybe the BLH could bring the woofer closer to the CD in sensitivity.
A back (rear) loaded horn won't increase the upper sensitivity of the woofer, which averages around 98dB from 100-1000Hz, while the HF is ~110 dB or more.
Back loaded horns also have a low mid path-length cancellation that reduces sensitivity below that of a direct radiator, as seen in the -5dB response dip from ~150-200Hz in the JBL 4530 "Scoop", which drops off at 24dB per octave below 60Hz.
The 4530 is 1213mm tall x 603mm wide x 603mm deep (47" x 23"x 23"), around 407 liters (14.4 cubic feet).
And my wife isn’t happy with 200litre speakers in the livingroom, yet!
Forget rear loaded horns...

Back:rear loaded horn.png

Consider looking for 15" with an Fs around the frequency of the low extension you'd like to reach in a vented box.

Art
 
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With the BIANCO-12MW200 mid-woofer's Fs of 51 Hz, 35Hz will be more than 8dB down in a vented cabinet.
It could work in a back loaded horn, but would need to be huge to reach 35Hz.
Maybe thats right. But Hi-fi-Selbstbau made this comparrison. I looks like the low is closer to 40 than 35hz.
But they also mention that inroom amplifikation could give lower hz.
IMG_0627.png
 
I looks like the low is closer to 40 than 35hz.
Room effects could increase or decrease level at various frequencies compared to the simulation.

The simulation of the BIANCO-12MW200 (Vas 62.9L) in an oversize 100liter with a 40Hz Fb (box tuning) appears to show 90dB at 40 Hz, 9 dB down from it's 99dB sensitivity at 500Hz.
The low end would sound less than half as loud as the mid range.
Lower the Fb to 35Hz, and the low end would would drop another 3-5dB.
 
The low end would sound less than half as loud as the mid range.
Lower the Fb to 35Hz, and the low end would would drop another 3-5dB.
Thank you Art.
I see what you mean.
It also depends what your reference sounds is like, and how much deep bass you need, this is for Music only, not movies 😄
Well, i already bougt the driver rediculous cheap, and the compression driver as well. (New) So
Im going do measurements before deciding what to do.
The response is lilely going to chance when put in a box.
But is’nt this always the price to pay for High sensitivity?
I Got a MiniDSP, so i could anytime do some test listening before buying crossover komponents.
 
GM ... I wonder if you can clarify the calculation mass rolloff frequency Fhm? You stated Fhm = 2*Fs/Qts' whereas Edgar used Fhm = 2*Fs/Qes. Obviously there's a relationship between Qes and Qts (and Qts') but those two calculations produce different results. I'm not challenging you as, using that old line, you've forgotten more than I'll ever know. ( Or, if a little knowledge is dangerous, then I'm lethal 😁)
 
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The pioneers designed for matching impedance for max efficiency since power was (prohibitively) expensive, so only interested in effective motor strength of the driver's field coil, which was adjustable and later, permanent magnet motors.

Being ~ 'trained' by the pioneers thanks to having access via Atlanta's S.E. Altec, RCA, et al distributor's engineering team, never actually payed much attention to what others were doing, i.e. only subscribed to Popular Electronics, etc., so can only assume that he too was well versed in the 'art' of sound reproduction, designing matching impedance tube systems.

Fast forward to T/S and electronics' conversion to very low impedance amps and one has to use Qts' to ~ compensate or the horn is too 'lean'/'dry'/over damped in comparison.
 
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Scott and i (drawings) have done quiter a few horns.

What you usually see in most horns is horn loading tome certain point and then, unlkess well done, a poorish TL. All because of the mouth size. It needs to be big to go low. For 32 Hz the first approximation would be a mouth perimeter of 424 in/10.8m , square mouth of 21” /.54m or. circular mouth radius (ideal in theory), of 12”/0 .31m. (GM is the math correct seems small to me). And as i see on review you only want 35 Hz F8. I’mmnot going to recalculate that all, but it will be smaller.I use as an excusenstill a bit groggy from surgery.

This is for a horn radiating into free space/4∏ steriradians, put it on the floor/2∏ steriradians and it can be halved, load into a floor+wall (rear mouth now)/1∏ steriradians and it can be quartered, load it into a corner and it can be an 1/8th. If the aspect ratio too large thingsget a bit weird, but Ron Clarke came up with a clever trick to make a higher aspect horn mouth work like a circle (someone with more ancient lore than i could well show us :rediscover — butmitis one of the few novel things i have seen nin loudspeaker design in modern times.

illustrated by Ron’s Austin A126, and then A166: https://frugal-horn.com/ronhorns.html

This is Layertone’s CNC/translamA166 build which illustrates the curved mouth, but it has been shown that the smooth bends are all to often counter productive. Also translam is not a great building technique for lots of reasons.

layertoneA166.jpg


The trick has been incorporated into many of Scott’s designs.

twin-FH3-Maeshowe.jpg


Maeshowe, Twin Frugel-Horn Mk3 (loaded with a CSS MTM), and a regular FH3.


Maybe the BLH could bring the woofer closer to the CD in sensitivity.

A BLH only increases gain at the frequency that are hornloaded, typically less than 250-300 Hz, so sensitivity is whatever the driver’s direct radiating part does, 99 dB. But if you consider where you will be using it (Yuchi* comes in about 600 Hz), Probably 3 dB less, and ifyou decide some baffle step is needed it will be less.

*(i understand tehse are very sensitive to driver exit vrs horn thoat)

I suspect that with your limited extension requirements, a well done reflex will probably suit best. The one you show is not one of those. Q is a bit high you may want to add a bit of aperiodicity (is that a word?) to tame that. And a loemooutput impedance power amplifier.

I can’t get at my modeller ATM, but i’m guessing somethng like this could work. They are to be used with the Yuchi.For TAD 16”.

Tad-Ken-visual.png


dave
 
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I suspect that with your limited extension requirements, a well done reflex will probably suit best. The one you show is not one of those. Q is a bit high you may want to add a bit of aperiodicity (is that a word?) to tame that. And a loemooutput impedance power amplifier.
Thank you so much for your input. I Think your answer is what i was looking for.

I already have a 115L vented cabinet for testing. The comparison i posted was done with 100L enclosure, so hopefully it Will go lower a few hz.

I’m on a steep learning curve, and a couple of days in this Forum already gave me a lot.
I build these last vinter, a Joseph Crowe No.2037. Really pleasant sounding and so detailed with the oak horn, but 90db (4ohms) So not a good match with my 12w kt88 SE amp.
IMG_0265.jpeg


IMG_0225.jpeg
 
The thing droops so much down low that, unless you can go big-big (closer to 400L than 200L), I think you just either keep a "normal" (~125L) reflex box with a wide baffle by a wall or you commit to a corner placement and just put it in an Aristocrat as the best compromise.

If you just take an IEC baffle off of it, it's about thus-ish:

divAB_scr.png


Obviously, everybody will have a different take on the direction.

I'd just commit to a corner and put it in an Aristocrat (pinched a little more at the pinch) with the horn stuff outboarded on top. That'll be a solid bang/volume trade and jack-up the "punchy" area to compensate for some of this droop...at about 83L internal. If you can sell it domestically & if you have walls that are more solid than just gypsum/sheetrock, the corner will help a bunch. Otherwise, you might be able to build part of a faux corner "shell" too, but that's not gonna get enough. Looking at this curve, ideally you want 10dB up on the bottom from the cabinet+room or you'll end-up having to pad the compression driver maybe 12dB.
 
I think you just either keep a "normal" (~125L) reflex box with a wide baffle by a wall or you commit to a corner placement and just put it in an Aristocrat as the best compromise.
This was my original plan.
But i dont have enough experience to tell how the response could look like in a box. The Yuichi horn is loading approx 6-700hz, so my plan was to cross it beginning around the drop at 500hz, so the response was flatter. The compression driver goes easily down 600hz.

Thomas