When you are ready let me know
When you are ready let me know
Veiled? I didn't hear that at all and in fact, quite the opposite. Ian, the "hybrid" came from a mod to a change of the Giskard version and was based upon the lack of 2122 availability. No mystery there....
The combination, properly implemented, works really well up here in this hemisphere! But then, our drainage water flow runs clockwise!
Now, that certainly doesn't mean other ideas and methodologies don't do well and possibly exceed the intention on paper, at least.
Furthermore, given that there are LF room interactions influencing at the bi amp crossover frequencies, the bi-amp crossover frequency, give or take 50 Hz and accounting for slope, in the real world, are really moot, IMHO. Fourth order LZ at~290 Hz works fine here!
It comes down to specifics and saying something in a post is a loose conversation without controlled conditions where you are in fact comparing one filter set up to another and measurement to look at it objectively.
What l am saying is you may not have done exactly what we are on about here
It would be useful if you posted your actual schematic and some valid measurements
If you want to be a fly in the ointment no problem.
It's interesting that designs despite there apparent simplicity of using two drivers as for example the M2 have taken on a level of precision not seen before as a diy thread
Why?
Because they want it to be authentic and the want get it right.
"Furthermore, given that there are LF room interactions influencing at the bi amp crossover frequencies, the bi-amp crossover frequency, give or take 50 Hz and accounting for slope, in the real world, are really moot, IMHO. Fourth order LZ at~290 Hz works fine here!"
Well l am not sure jbl would agree with you on that statement
Jbl realised that a custom bi filter was required for the 4343 and then 18 Db for the 4344//4345.
Please refer to my comments concerning the 4344mk11 filters.
Ian, I certainly appreciate the work you are doing and always have done. But there is always a slant to DIY that should not be discounted. GT himself commented about the individual subjective appraisal of speakers.
There are no perfect solutions..
ChasOriginally Posted by Chas
If l read your post correctly are you saying you used the 434k11 schematic in its entirety for biamp use with the 2245?
If this is the case that is a different scenario that in post 60 and 62 whe there seems to be the belief that you can splice the filter of an earlier model in the 43xx series with another.
What Giskard did was create a different crossover that could be used with the 2123 or the 2202 so far as the 4344/4345 is concerned.
However, others have just spliced the mid filter of the 434k11 filter into the equivalent 3145 crossover
The acoustic response with the filters of the mid drivers and HF are different in both the 4344mk11 and the equivalent 4344 are not the same by any means.
The slopes and the levels are different and that why l have raised this point and posted graphs.
Then there is the transition of the woofer and 2123.
The 4344mk11 used an ME150H which was more sensitive than the 2235H but similar sensitivity to the 2345H
The 4344mk11 schematic is arranged do allow either bi wiring and bi amping.
In biamp mode the low end of the 2123H is limited by the action of the band Pass filter form by the remaining elements and the driver raw response.
As l mentioned earlier the 4344mk11 is more advanced and incorporated a permanent trap LR across the driver.
When the biamp switch is position to bi amp the effect is the driver low end is rolling off at 6db per octave in the Pass Band.
In passive crossover position the 36uf and series 1.2R resister forms an additional 6db of slope creating the 2nd order filter slope.
Now, to ensure we don't screw up the wonderfull job of the crossover designer it would be useful to evaluate what bi amp filter will work best for the pure 4344mk11 in the case of the 2235H and the 2245H
If a conventional symmetrical active filter is applied the actual acoustic response of the 2123H may not sum flat and may have phase lobes in the vertical plane that impact on the voicing of the system.
Okay you might say what does it matter what l do?
We have no control of that but it's useful to publish valid information about what should work as opposed to what l think l did!
Multi way systems like this are complex and sometimes you only have to change or have one thing out of whack and the whole shabang turns to an annoyance.
This is not the first time bi amp filters have been discussed
Previously when some decided to investigate the Bryson active crossover the question of filter crossover points and slope came up.
Curves
1.Measurement of Passive system crossover curves (near field) (top)
2. 2245 5 Db/ division 1 octave smoothing
Raw driver
With passive low passfilter (3145)
The peak in the bass can be ignored as is an environmental issue.
3. System response 10 Db/division 1 octave smoothing
The gentle rise in the lower end is a function of the ground plane measurement technique.
4. 2123 5 Db/division 1 octave smoothing
Raw driver
With mid filter bi amp mode
5. Simulation of the passive 2245/2123 crossover using the 3145 low pass filter values and the 4344MK11 mid filter .As can be seen this filter sums flat and has the correct phase relationship at the crossover point. The simulation is derived from real data using measurement of the drivers. The data is conditioned and then applied to different scenarios.
This is more efficient than building trial networks.
Ground plane measurement- enclosure inverted - mic distance 1 metre
LMS - precision calibrated mic
I have done some preliminary bi amp simulations
The 3rd order 290 Hz active crossover does not sum flat with an +3 Db hump unlike the passive network. No surprises there.
It is important to understand that these humps are phase errors and cannot be reduced or removed with equalisation without causing more problems than it solves.
The better way is to design the crossover point to sum flat at a reference point on the baffle(at the bottom of the lens) from a given distance to the test mic.
TBC
I have simulated both the 3rd order 290 Hz and the 290 Hz LR bi
In practice the 3rd order filter may prove the best overall option
Why?
It provides sufficient attenuation and may provide better phase coherence in the crossover region.
This may defy the text book attributes of the LR filter but because of the offset of woofer and mid driver voice coil the typical forward Lobe points to the floor and not the listening space.
What this means is the power response in the vertical domain an octave either side of the crossover point is not ideal.
In this respect the LR filter is imperfect and there is no clear in phase/ out of phase relationship when the driver polarity of the woofer is reversed.
The 3rd order filter exhibits a more clearly define in phase/ out of phase relationship when the woofer polarity is reversed.
I plan to do a ground plane measurement later in the week to confirm this.
The diagram below illustrates the ideal LR polar response in the crossover region.(right)
Imagine the lobe skewed downward and the direct sound is the null.
Of course much of the sound is indirect but we ideally don't want the main lobe pointing away from the listening position
On the left
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