zobsky contemplates a variation on the belle klipsch

[zobsky]

For a little while now, I've considered building a variation of the lascala / belle klipsch . This post mostly concerns the bass bin design of the belle.

For your reference, I've attached the standard plans for a belle klipsch .

1. From these plans, I've attempted to simulate the response of a belle klipsch running an eminence kappa 15c with the DJK ported mod on the front baffle (see pic). From the sims, it looks like I don't really need to add a riser (the riser mod adds more deep bass, though at lower SPL - this level can be lifted via an EQ boost). I can live with a solid 50 Hz and implement a sub to take care of the first 1.5 octaves . Regardless. I've added an arbitrary "underbelly" to my rendering that can be increased if needed.

Thoughts on my analysis of the EQ mod (I used the stock rear chamber volume of about 68 liters (65 liters + 3 liters I intend to use by cutting into the dead space enclosed by the 2 V, the rear of the enclosure and the motorboard)?

 

[zobsky]

Also, A few weeks ago, I inquired about the possibility of using multiple drivers in push pull ( see http://www.diyaudio.com/forums/subwoofers/266463-push-pull-vs-single-driver-bass-horn.html ) . That's a possibility for this project, once I'm assured mmy current proposal is feasible.

Another wild thought I've had is to implement a paraline (without a horn extension) with a few suitable midranges and a compression driver on the board with the ports (and completely dispensing with the upper horn section). Thoughts ?

 

[picowallspeaker]

Also, A few weeks ago,

A few centuries ago there were experimentations about the adiabatic theorem and Bernoulli's principle

 

[zobsky]

For reference, here is a comparison of the standard response of the belle (in black) vs the chosen port (in light grey)

 

[zobsky]

Looking at the detail of the motorbikes, the driver fires into a 3" x 13" which is immediately bifurcated into two 3" x 13" throats . Shouldn't the first throat be nominally 6" x 13", or is there something else going on?

Thanks

 

[DrBoar]

The odd constriction is supposed to do with path length differences and such and improves the upper end of the horn.The bass highpass do look early. Have you tried reducing the camber volume by 2/3 or so? I tried several drivers in a horn similar to the La Scala and the bass was deeper with mid Q drivers (0.4 or so) so try running a simulation with a cheaper driver! You should get the horn down to 60 Hz without ports.

 

[zobsky]

Will try so and report back

 

[freddi]

I'm not sure how well the rubber throat works. With the stock Peavey woofer, here's what my FH1 did in ~2pi conditions . FH1 was about the same frontal size as Belle but 2 feet deep. A Belle knockoff could probably come from one 4' x 8' sheet. (that would be cool if XRK971 made one of pink foam board)

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

 

[zobsky]

Here's the response with a somewhat less powerful woofer, the community 110470

Nominal Diameter15"Power Handling (RMS)200 Watts
Power Handling (max)400 WattsImpedance4 ohms
Frequency Response40 to 5,000 HzSensitivity97.91 dB 1W/1m
Voice Coil Diameter2.38"
THIELE-SMALL PARAMETERS
Resonant Frequency (Fs)39.03 HzDC Resistance (Re)2.29 ohms
Voice Coil Inductance (Le)0.83 mHMechanical Q (Qms)4.62
Electromagnetic Q (Qes)0.43Total Q (Qts)0.40
Compliance Equivalent Volume (Vas)10.26 ft.³Mechanical Compliance of Suspension (Cms)0.25 mm/N
Diaphragm Mass Inc. Airload (Mms)65.47gMaximum Linear Excursion (Xmax)2.50 mm

Not too shabby for a sealed rear chamber though I can't speculate how this will sound subjectively compared to woofers with more powerful motors. The FAQ on parts express implied that this cone might not be beefy enough to handle the high throat compression ration.

Increasing / decreasing the rear chamber size does alter the response somewhat in either direction. I'll experiment with some other drivers

 

[zobsky]

Here's my sketchup model in case any one else needs / wants it

 

[zobsky]

I'm not sure how well the rubber throat works. With the stock Peavey woofer, here's what my FH1 did in ~2pi conditions . FH1 was about the same frontal size as Belle but 2 feet deep. A Belle knockoff could probably come from one 4' x 8' sheet. (that would be cool if XRK971 made one of pink foam board)

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

Thanks for the info, Freddy. I'm hoping I can get a pair out of a couple of sheets of ply. Hopefully, the weather next weekend will be pleasant enough to work outdoors. I can't bear to deal with the effort of cleaning out my garage after a major wood working project

 

[tb46]

Hi zobsky,

That looks like a great project. Have you tried using the CH driver arrangement in Hornresp? It gives you additional flexibility as to the throat and reflex port simulation.

Regards,

 

[zobsky]

Hi zobsky,

That looks like a great project. Have you tried using the CH driver arrangement in Hornresp? It gives you additional flexibility as to the throat and reflex port simulation.

Regards,

Hi tb46, At work now on a linux workstation. I'll look at your HornResp sim later when I have access to Windows & HornResp.

In the mean time, what's the CH arrangement ?

 

[tb46]

Hi zobsky,

CH = compound horn

Help file: |

Compound Horn
~~~~~~~~~~~~~~

Select the compound horn option from the Driver Arrangement tool or double-click Nd, OD or TH in edit mode to set the CH flag. Horn 1 is specified using segment 1 plus segments 2 and 3 if required. Horn 2 is specified using segment 4

It's a great way to simulate bass-reflex w/ FLH, e.g.: some of the so-called Onken arrangements.

Regards,

 

[zobsky]

Looking at my initial render, I wonder if using cabinet feet to raise the speaker off the ground iscounter productive to the intended 1/4 space (wall loading) application . OTOH, the wavelengths in question are significantly larger than the height of the feet so I don't know if a few inches makes a difference.

 

[DrBoar]

For various drivers in something similar to the La Scala take a look at
Doctor Boar; DIY loudspeakers and HiFi: 9/1/12
Simulations of changing the chamber size really does minor changes in the high pass knee. That is if the knee is a gradualy increasing slope or a sharp bend or even a small hump. Going down in sensitivity of the drivers also lowers the sensitivity of the horn. But in a domestic setting that hardly matters.

 

[zobsky]

For various drivers in something similar to the La Scala take a look at
Doctor Boar; DIY loudspeakers and HiFi: 9/1/12
Simulations of changing the chamber size really does minor changes in the high pass knee. That is if the knee is a gradualy increasing slope or a sharp bend or even a small hump. Going down in sensitivity of the drivers also lowers the sensitivity of the horn. But in a domestic setting that hardly matters.

Great info. I hadn't thought about adding a driver spacer . I think it's definare ly something worth adding

I'll look at alternate drivers too. I have some Pyle clones of eminence kappa 12 that have Qts of .3xx

 

[zobsky]

Update:
1. Ordered the last two eminence kappa15c restocked/refurb drivers from parts express at $55 each (a very good deal - 50 % off). I don't care what they look like as long as they perform and measure to spec (since they are going to be hidden anyway). Looking at DrBoar's website, I can always experiment with raising the Qts via series resistance / inductance if that helps the response.

2. Looking at my prototype, it would make more sense (and arguably look better) to add (removable) slot ports to the underbelly, closer to the ground place - as opposed to installed into the center board

 

[GM]

Here's the response with a somewhat less powerful woofer, the community 110470

Looks good in an Onken alignment and two look really good if a ~678 L cab is acceptable.

GM

 

[zobsky]

Looks good in an Onken alignment and two look really good if a ~678 L cab is acceptable.

GM

Much obliged, as always, for your insights, GM .