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(Yet Another) FLH Upper Bass Build


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Hi,

 

This is my first post, although I've been a long-time follower and longer-time Klipsch user.  

 

A bit about myself:  I've been listening to horns for awhile. My first "high-end" system was Klipsch Heresy powered by Counterpoint tubes and sourced with vinyl (back in the day).  I took a detour with non-horn loudspeakers for a few years, but returned to horns with Dr. Edgar's Edgarhorns, and now listen to a multi-way horn system of my design.  

 

I'm moving forward on a dual-driver, tractrix FLH upper-bass horn, with these design goals (but I'm still uncertain if all are achievable):

 

1) FLH architecture for a clear upper end

2) BW: 100 - 600 Hz (2.5 octaves)

3) Directivity:  90 degree BW at 500 Hz minimum, and as high as possible

4) SQ focus on transition from upper-bass to midrange, rather than ultimate low-frequency extension due to:

     - Human hearing is more sensitive in the midrange than low-frequency

     - Deliver dynamic, visceral "thwack" over upper-bass extension

5) Tractrix curve - to integrate well with the midrange

6) Crossover ~ 500 Hz to 1) Edgar 350 Hz round tractrix / B&C DCM50, and later to 2) K-402

7) Crossover ~ 90 Hz to stereo Danley SPUDs

😎 Mouth of sufficient size to minimize ripple

9) Length balanced for extension and minimal group delay

 

Assumptions:

 

- Half-space

- Quarter-sized

- Dual drivers to minimize horn length and driver excursion

- Fits through doorways (~ 31" max)

 

One source of inspiration for me has been @jwc bass horn projects.  I find his projects well-considered and clearly articulated.  Also, @setifor documenting so much of interest to horn-lovers like me.  Thanks, @jwc and @seti!

 

First, I selected B&C 10" 10MD26 woofers because I have some familiarity with them from past builds.  They are very sensitive, with lightweight paper cones, and strong motors.  I chose 10" drivers (rather than 12" or 15") to integrate with the midrange.

 

https://www.bcspeakers.com/en/products/lf-driver/10-0/8/10md26

 

Using Edgar's and PWK / Delgado AES papers as a guide, the following parameters are calculated:

 

MASS ROLL-OFF

 

Fhm = 2 * Fs / Qes

 

        = 2 * 76 / 0.22

 

        = 724 Hz

 

THROAT AREA

 

St = ( 2 * Pi * Fs * Qes * Vas ) / c

 

    = ( 2 * Pi * 76 * 0.22 * 0.20 ) / 343

 

    = 58.47 cm^2

 

BACK CHAMBER VOLUME

 

Vb = Vas / [ ( Fc / Fs * QEs ) ] -1

 

     = 20 / [ 90 / ( 76 * 0.22 ) - 1 ]

 

     = 4.3 L

 

REACTANCE ANNULLING CHECK

 

Fc = Qes * Fs * ( 1 + Vas / Vb )

 

     = 0.22 * 76 * ( 1 + 20 / 4.3)

 

    = 90.19 Hz

 

Finally, to the reason for my post....!

 

My experience is mostly running Hornresp.  Since I need data in AutoCAD compatible format for the build (as well as curiosity about cross-checking David's Hornresp with Edgar's / Keele's maths) I chose to model on Volvotreter's excel tool download.  I'm running into an obstacle though, because I haven't figured out how to model a dual driver design on Volvotreter's tractrix calculator.  

 

***Can anyone share guidance on this?

 

Also, Hornresp uses a forcing function to calculate horn length, given inputs of throat area, mouth area, and Fc.  But the result seems to differ from Volvotreter's worksheet.  Usually, Hornresp results in a longer path length.  Naturally, I want to minimize bulk while still attaining my design goals.

 

I think JWC's full-sized horn was 61 cm deep.  So perhaps I'm guilty of operator error because I get a differing path length when I model his horn on Volvotreter's tool.

 

In any case, I suspect I'm making a simple mistake and am here seeking a little oversight and adult hand-holding.

 

Thanks for any clarification.  Cheers!

 

 

Edited by Tetsuo111
Clarity
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My dual 12" woofer tractrix horn is calculated as a full space tractrix 90Hz.  Throat 90 sq in.  (If my memory serves)

 

Measured in more than one room would extended to 70Hz then drop.   There were very little parallel walls....so not much dips in response.   Best soundin horn I ever made.  

 

Jc

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24 minutes ago, seti said:

I wish I knew more to chime in but I just know how to listen and feed horns...

 

 

 

 

Me, too.  I understand the equations and all that, but last I was familiar with "FLH" is a Harley "touring" platform...

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On 4/5/2019 at 3:49 PM, Tetsuo111 said:

Thanks, Moray.  I've communicated with John in the past.  I need to pay him a visit sometime!

IMHO, I would target 80 Hz. as the cutoff for your Straight Axis Midbass. I have been involved in building 7 SPUD Tapped Horns, and the lower the Xover point, the better. Just sayin'. You might want to try JC's horn with a single 12" driver instead of 2 for 1/2 the height.

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With your throat calculation with two 10" woofers, your horn will need to be longer than mine with the same size throat.  However, if you choose to 1/2 space....then things get smaller.

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13 hours ago, jwc said:

My dual 12" woofer tractrix horn is calculated as a full space tractrix 90Hz.  Throat 90 sq in.  (If my memory serves)

 

Measured in more than one room would extended to 70Hz then drop.   There were very little parallel walls....so not much dips in response.   Best soundin horn I ever made.  

 

Jc

 

Everytime I put it back in rotation I am pleased. All it needs is a 1802 or 1502 HLS 8-)

 

 

 

 

 

 

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  • 4 weeks later...

Gents -

 

First, regrets for a long-delayed reply.  It's simply been super-busy around here lately, and there's never enough quiet time to focus on horns after satisfying other time commitments.

 

Second, a HUGE THANK YOU to JWC and Seti for your support.  JWC's dual driver horns were the inspiration for this project, mostly for his results, but even more for a logical, well-documented thought-process.

 

Third, I moved the thread to a different forum, assuming (rightly or wrongly) my DIY project might be a distraction in this Klipsch-centric forum.

 

For those interested in following, here you go:  

 

https://www.diyaudio.com/forums/multi-way/336290-upper-bass-tractrix-flh.html#post5779878

 

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On 4/6/2019 at 7:24 PM, ClaudeJ1 said:

IMHO, I would target 80 Hz. as the cutoff for your Straight Axis Midbass. I have been involved in building 7 SPUD Tapped Horns, and the lower the Xover point, the better. Just sayin'. You might want to try JC's horn with a single 12" driver instead of 2 for 1/2 the height.

Hi @ClaudeJ1, I strongly agree that tapped horns sound better the lower the crossover.  I can hear the nastiness coming from the upper-end.  I don't think it makes TH's a "bad speaker", simply that they need to be implemented intelligently and within their performance envelope.  

 

Sadly, 80 Hz is a difficult target to hit (for me), while also satisfying my physical size limits and upper X-over plans (~ 400 - 500 Hz).

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On 5/3/2019 at 2:49 PM, Tetsuo111 said:

Hi @ClaudeJ1, I strongly agree that tapped horns sound better the lower the crossover.  I can hear the nastiness coming from the upper-end.  I don't think it makes TH's a "bad speaker", simply that they need to be implemented intelligently and within their performance envelope.  

 

Sadly, 80 Hz is a difficult target to hit (for me), while also satisfying my physical size limits and upper X-over plans (~ 400 - 500 Hz).

If needed, You could "cheat" by porting the back chamber like the DJK mod. That should net you a few Hertz if need to mate with a TH.

 

FWIW, despite everyone who raves about this mod, I still am not in love with it, but it could help with integration if the situation / need arise.

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