pushing a 15" driver higher for crossover

charlie2

Member
2012-10-27 8:45 am
Uk
trying to work with this cabinet at present JBL 4638 twin 15" JBL_4675C_503cd5f489b62.png

now I have a couple of previous posts regards this. (jbl 4435 knock off)

But what i am looking into is, as i have the cabinet vertically unlike horizontally (jbl 4435)

lower driver crossed around from 20---300hz

next driver 20---1500hhz plus

there is a 600hz null with this cabinet center-center spacing.

the waveguides I have are the jbl/pyle 612 econowave now previous advice was that waveguide could not go low enough.

so i had a brainfart:rolleyes:

the KEF concord back in its day 1401335577588165204.jpg

the nexo to this day $_57.JPG

also this post on diyaudio that went dead https://www.google.co.uk/url?sa=t&r...d.html&usg=AFQjCNH7OkEBLUoPxkL1Ai52FoFbucultA

with good input from bjorno a member on here who provided this tech spec (could someone put his results/findings into plain text please)[IMGDEAD]http://i66.tinypic.com/2egff40.jpg[/IMGDEAD]


here is some drawings of what i was thinking (DSP INVOLVED REGARDS DELAY XOVER)

[IMGDEAD]http://i66.tinypic.com/2lxw3r7.jpg[/IMGDEAD]


[IMGDEAD]http://i64.tinypic.com/ous1tv.jpg[/IMGDEAD]

basicly having the compression driver and waveguide mounted on the driver but protuding quite a bit forward from the baffle.


if i have not put it into words right please say
 
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charlie2

Member
2012-10-27 8:45 am
Uk
jbl 2035hpl

the two 15" DRIVERS ARE jbl2035hpl

I can't find any frequency response graphs for these online, sent a request to JBL but no response from them.

a poster on audio heritage said they are good up to 1200hz

DJK on here mentioned this JBL eon aperature anyone tried these eon615_hero_nogrill_r.jpg
 
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charlie2

Member
2012-10-27 8:45 am
Uk
well after a few measurements here is where i am at

made a nexo directivity guide

IMG_1487.jpg

all measurents raw no eq or crossover

measured on axis then 20/30/40/50/60/70 degrees without guide

test 4638 no guide.jpg


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and here with the guide


jbl 15 with wavegude.jpg


will have to measure verticaly next (cabinet laid)





jbl  4638 with and without guide.jpg













But I could here a distinct difference verticaly between top driver and CD waveguide mounted on top of cabinet
 
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charlie2

Member
2012-10-27 8:45 am
Uk
Raw measurements line up with impedance, so need to find out what's causing all the HF 'ripple': Home Theater Overhaul: JBL Pro L/C/R Build

Reflections off the frame, cone breakup or........? Otherwise not sure how well a simple phase plug will help.

GM

realy appreciate the input GM

here is a photo of the cabinet, drivers are not flush mounted, but are 15mm from baffle proud

sides protude about 8mm infront of baffle

IMG_1488.jpg

I can router the sides flush and recess the drivers into the baffle?????

could you please explain further the high frequency ripple you refer to (at what point do you call HF)

cheers


ps center to center is 18"
 
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Greets!

The ones in the link I posted.

'HF' in the sense that it's the upper BW of the woofer and in particular, the BW above the driver's upper mass corner where the cab's impact on the driver's performance has faded away [Fhm = ~2*Fs/Qts], so only the driver's forward radiation.

GM
 
With a [very] little help from me [I was 10], that's the article my neighbor built his Karlson from and gave me my long lasting, mostly negative opinions of them. Thanks for the 'walk down memory lane'! :up:

ROTFLMAO reading the tongue-in-cheek 'Variable-Height Fidelity' [pg.57]. It's a really sad 'state of affairs' that it's still relevant today.

GM