JBL 4344 Clones

[fencki]

hi.
thanks a lot for those measurements and test.
very interesting for me, because i am still not sure about my decision which crossover to use.

because my englisch is not the best i have one or two questions.

does that mean, that you tried the 4344 mk2 schematic with the mentioned drivers (with no change of any values or routing)? (= green line)
does that mean, that you tried the giskard schematic (with taking the 2123h section from MK2 for MF) and all other values from giskard? (violett line)

if i understood that right, then the original 4344mk2 schematic resullt (=green) looks better for me (maybe not the "hole" at 10kHz.)


thx a lot for your expertiese...

best regards from vienna
slavko

[fencki]

and YES, i am very interested in reading your future post regarding to this topic.

[Ian Mackenzie]

They are independent measurement of actual component values where people have used the mid filter of the MK11 crossover and then used the Giskard filter for the horn and slot. I refer to this as hyprid filter (violet)

The MK11 filter uses if all values in the MK11 schematic for the mid, horn and slot (green)

The reason for people using a hyprid filter alludes me.

But someone essentially complained about the outcome after being given advice to use the hyprid filter so l investigated the reason.

Of course it is entirely up to the individual what they decide do with their own project.

I have posted this information as a heads up.

If you want or need individual "advice" pm me.

I'm am usually available with donations of fine red wine for my amazing wife!

[fencki]

i like your explainations.
they help me a lot and i am thinking more about the aspects of all sides of the topic.
please keep up with that. it is very interesting for me.
i am a newbie for crossovers and their effects and thankful for everything i can learn.

and this graph was very helpful for my project.

thx

[fencki]

They are independent measurement of actual component values where people have used the mid filter of the MK11 crossover and then used the Giskard filter for the horn and slot. I refer to this as hyprid filter (violet)

The MK11 filter uses if all values in the MK11 schematic for the mid, horn and slot (green)

The reason for people using a hyprid filter alludes me.

But someone essentially complained about the outcome after being given advice to use the hyprid filter so l investigated the reason.

Of course it is entirely up to the individual what they decide do with their own project.

I have posted this information as a heads up.

If you want or need individual "advice" pm me.

I'm am usually available with donations of fine red wine for my amazing wife!

in austria we do have VERY good wines!
;-))

[Ian Mackenzie]

I will do a near field and ground plane measurement of the 2123H impedance and acoustic amplitude response on the baffle and of the 2245H with LMS for analysis in LEAP5.

Other than the original JBL technical data sheets l don't think this had been published recently so it will be quite interesting.

[Ian Mackenzie]

Attached is a voltage drive charting the Giskard and MK11 filters

Refer to the legend for the horn and slot voltage drives.

I have also attached the individual response curves of the native 2122H and 2123H drivers for comparison

Note this NOT the acoustic response of the individual drivers with the filters.

As can be seen the 2123H is somewhat more extended in the midrange and more sensitive than the 2122H.

The MK11 mid filter is more complex as it must attenuate the additional sensitivity while equalising the native driver to form a flat response and provide the crossover slope.

In this respect the 2123H and the horn have a somewhat more gentle overlap before attenuation slope.

My subjective view of this is closer voicing or blending of both the 2123H and the horn which was always obvious in the prior 4343-4344.

Likewise the horn is allowed to extend with a gentle roll off slope in a systematic and controlled manner into the upper octaves. The acquaplas dusted diaphragm provides more depth meaning blacker backgrounds improved resolution.

The 2405 lights up in the upper octaves and provides remarkable speed, air and spatial clarity.

[fencki]

very very good job! very interesting post!

[Ian Mackenzie]

I have done some initial work.

At this point l would say the voltage drives for biamping like the earlier 4343 are not simply 24 db LR 340hz or 12 or 18 db slopes.

The woofer is not straight forward either.

I need to do more measurements before proceeding .

[fencki]

awaiting your research. very interested in such things...

[Ian Mackenzie]

Okay

If the weather is okay today l will do some external measurement using the 2245H.

The question or what might be term the issue is how will the 2235H and 2245H work with the MK11 passive filter and what is the active filter requirement?

The reason for external measurement if you are not familiar is that a measurement in a room and particularly a smaller rooms are problematic to be of any use at 500 Hz and below. Reflecting surfaces and room mode come into play.

In the case of the 2245H as mentioned earlier it is best used with an active 18 db 3rd order or a 24 db LR filter.

A 12 db filter would not be suitable in this application.

The 2235H can be used with a 12 db filter slope but l would tend to standardise on a defacto active filter for both drivers in this application.

Arriving at what could be described as good best practice for using either the 2245H or the 2235H in passive mode is a challenge.

The convenience of less equipment a consideration.

Will either of these drivers work in the stock MK11 filter requires some further investigation.

We firstly need to understand the function of the MK11 passive filter.

Looking at the MK11 passive filter schematic in detail the slope of the 2123H with L3 and R8 with the switch in bi amp position is approximately 6 db per octave.

The inclusion of the capacitors C1, C3 R1 and R5 is approximately a 12 db per octave acoustic high pass acoustic slope where these components for the additional pole.

So in theory at least to arrive at an 18 db per octave 3rd order high pass filter for the 2123H the active filter would be 12 db 2nd order 2 Pole filter.

However the asymmetric nature of such an active filter 18/12 db per octave may not be convenient in practice.

JBL may have considered a custom card for their DX1 active crossover when they were available. This unit is NLA.

The other option is a 24 db LR active crossover with a degree of adjustment like the Ashly.

This crossover has an an adjustment at the crossover point to arrive at a flat summed response. The actual crossover point is a matter of adjustment but in the region of 300 hertz.

http://ashly.com/wp-content/uploads/...sovers-r01.pdf

You can score this crossover on EBay at quite a reasonable price.

The question of whether the Ashly is deemed a hifi qualify active crossover is questionable but it's a good starting point before you decide to spend US$1250 on a First Watt B4 crossover which l use. The B4 model has a range of custom filter adjustment that make it entirely suitable.

The importance of utter transparency in the active crossover cannot be overstated if your quest is to maximise the performance of the MK11 system.

I have used a LR 24 db filter with the 4345 in the past.

The traditional well executed LR24 filter is industry standard but may require careful adjustment as the driver overlap is narrow.

Note too that an asymmetric filter function will apply (24/36 db per octave) with the MK11 if a non adjustable 24db LR filter is used. The impact of this is unknown at this stage.

I will investigate measurement of the passive and active mode as time permits.

The attached curve below is near field for illustrative purposes of the discussion using the 2345H.

The smooth black curve is the high pass 12 db 2nd order slope "objective".

The 2123H tracks the objective reasonably well.

Because the near field measurement was on the 2123H axis the result of the 2245H is not accurate.

[bldozier]

😶

[BMWCCA]

The question of whether the Ashly is deemed a hifi qualify active crossover is questionable but it's a good starting point before you decide to spend US$1250 on a First Watt B4 crossover which l use. The B4 model has a range of custom filter adjustment that make it entirely suitable.

Not that I would know anything about a $1250 crossover, but I did consider the Marchand prior to purchasing my first (used) Ashly XR1001. It's worked great for me for over eight years. I had a bit of a problem with dropouts from one section at some point which I traced to a pot on the Ashly that had a dead-spot. I contacted Ashly and they quoted me a very reasonable fee to repair it but also offered to send me a new potentiometer free-of-charge, which I took them up on. I'm still using it without repair just bumping the setting slightly and I've since purchased another excellent condition used Ashly to put in the system while I effect the repair on the original. Then I'll either have a replacement, should I need it, or use the spare to try bi-amped L7s!

[Ian Mackenzie]

Thanks for chiming in.

Like any piece of audio equipment the final choice depends on your own situation and the considerations associated with that such as your technical understanding of how to set these crossover up. Some manufacturers offer assistance.

But otherwise the user adopts a Monet approach to passive/active crossover execution with insights obtained from various forum posts. The key is in collecting quality data.

As l said the Ashly works, it does get you going and they are accessible .

I started with the JBL 5232 off eBay.

http://www.jblproservice.com/pdf/Vin...-5231_5232.pdf

Other forum members have moved on and purchased the Bryson active crossover, DEQX , .Passlabs and reported audible improvements.

There is nothing exclusive about diy or vintage audio.

Do what you.

[fencki]

i have a tannoy xover and will get an JBL 5235 with teh right cards for 4345...
will have to do a lot of test.


but first the JBL has to be finished.