M2 diy passive crossover thread ---- from down under

Reading on from post ................

This is a new thread dedicated to a DIY Passive Crossover for the M2 DIY clone

Its a lead in starter for anyone planning an M2 clone or those wishing to simplify from an active to a passive set up.
This is not a completing alternative to the DSP crossover specified by JBL.

I will continue to post some measurement as a means of zeroing in on the passive crossover network.

Today I measured the 2430 driver on the M2 horn withe the voice coils wired in parallel.
The acoustic response is compared to the 2216dn in a grouped screen shot.

The test conditions are identical to my previous measurements:

The DBFS reference test level for the REW Analyster was set at 75db.
Distance = D = 1 metre


Notes:

The purpose of today’s measurements was to ascertain the difference in sensitivity of the parallel wiring of the 2430 driver voice coils.

Based the the curves below the 2430 driver with its voice coils wired in parallel is between 10-12 db more sensitive than the 2216nd.

Back in post 859 of the M2 diy thread l noted with the 2430 driver voice coils wired in series (32 ohms ac impedance) the 2216nd woofer was about 5 db less sensitive.

So what’s the deal?

There are advantages and disadvantages with wiring the voice coils either way. In a dsp scenario there will be 6 db less noise due to the lower driver sensitivity.

In a passive crossover the additional sensitivity of the 2430 can be used to an advantage in the passive network for matching the sensitivity to the 2216nd woofer after normalising the 2430 response.

For example when using dual 2216nd woofers.

The down size is that the lower driver impedance can present a lower load impedance to the power amp at high frequencies unless care is taken.

To repeat from the M2 diy thread these are the steps l am following.

I hope to have the test and measure series below sorted by mid next week.

I have received a REW file a the 2451 with SL diaphragm from Scott and compared it with my REW measurements of the 2430 driver. While the are similar the emphasis for EQ normalisation below the mass roll off point is different. I also need to compare and assess the sensitivity differences.
I will discuss this in more detail once l have collected the data from steps B to E.

My next steps are :

A. To assess parallel connection of the 2430 driver voice coils and some measurements. Done
B. Test and measure a 2447 driver on the M2 horn.
C. Build and tests the 2216nd 6th order passive filter.
D. Validate 2447- versus 2430 measurements and HF filter design.
E. Build and test HP filter& EQ or any revisions for different drivers.
F. Test and measure passive system voltage drivers and frequency response curves.
G. Subjective assessment. Yes/No Pass. Fail revert to E.

I hope to have cut panels for the M2 enclosures soon.

Update

Some promising news. I have been able to adapt different driver impedances from 32 ohm to 5.7 ohms using the 2340 in either series or parallel voice coil connection.

No RCL elements in the crossover need changing.

The Tilt Adjustments work beautifully after l optimised the network impedances. See last image. The red line is the overall flat optimisation including crossover slope @ 36 db per octave.

Range of the Presence Tilt Control is just over 1db in the 1.4khertz to 2.5 hertz region. The effect is most noticeable on brass instruments.
Range of the Brilliance Tilt Control is 3.3db at 10,000 hertz. The rate is about 1 db per octave referenced to 2Khertz. The effect is to arrive at a comfortable HF tonal balanced when using CD horns.

The network has yet to be fully tested. Simplified High Pass section shown only.

I am happy with the network at this stage. My wife always said l was very clever…Bom Bom…Lol

Hi Robert H. If you can please email me an export file of your 476 impedance and FR files from Leap for comparison. l can then check the results of a JBL conventional driver with a 12 ohm working impedance. The email address is in my signature.

The Doctor

Hello Ian

Sure working now send them latter on.

Rob :)

Hi Ian,

Thanks for posting the 1m measurements on the 2216nd's. I don't recall these posted anywhere here. What was the cabinet volume?

Thanks,
Scott

Hi Scott,

The test enclosure is 5 cu ft3 was built from the plans in the JBL enclosure kit in the late 1970’s.

It’s a semi free field test as the enclosure is on its side about 1.2m off the ground outside.

The M2 horn was carefully positioned above the woofer.

Another empty test enclosure was vertically positioned to supporting the test enclosure.

Here is my previous loudspeaker tester Tilly. I miss her.

Isn’t she beautiful. Okay

There's nothing serious about this thread. Its diy.

Speed Bumps and why they are there?
For those looking at the bumps in the horn response around 1.5Khertz do not be put off.

The divisions are 5 db so it’s a variation of like +-1.5 db and the response at your listening position with have far more artefacts.

Always trust your ears with a familiar recording.

Do not listen with your eyes by interpreting a frequency response and then listening.

The reason for the bumps is the variation in the voltage drop across the Presence tilt resister connected directly to the compression driver via the crossover filter. Further treatments of the response would add complexity and cost. I also prefer not to put EQ close to the crossover region which is phase sensitive. It’s a trade off of having the access and convenience of a variable adjustment in the frequency range. I think the benefits out way any potential disadvantages.

Future permanent modifications
If after a time a user reaches a consensus on the Presence Tilt setting (l can make the range of this control wider) a modification can be used to make a permanent response level with obvious bumps.

In the scheme of things these curves are only 1/6 octave smoothed for clarity. The pitting of an un smoothed response makes a curve unnecessarily noise for public viewing. Why look at every wrinkle of the Mona Lisa when you won’t see it at your listening position some 2.5. to 2.3 metres back.

Listening Window Response
Once the network is finalised l will run some listening window averaged curves over a 60 degree arch.

Hello Ian

Check your email. Sent you the files for both of my 476Mg's on the M2. I also have IMP files for both the 476Mg and the 2453HSL on the PTH1010. Let me know if you want them. It gives 8 vs 16 ohm drivers on the same waveguide to use for comparison if you want them.

Rob :)

Hi Rob,

I received the files thank you. Interesting.


I also need to compare a conventional compression drivers response to the 2430. If you can send a FR file of the 0476 on the M2 that would be great thanks.

There is consistency in the shape of the impedance curves. The magnitude is of course different.

For those viewing this thread the reason for the comparisons is to assess the best approach for implementing a universal passive crossover and passive CD EQ for several different compression drivers on the M2 horn.

I still need to confirm the low end response of the 2451 / or an 0476 in comparison to the 2430 on the M2 horn.

It might end up a modular section of crossover filter and or EQ as a build for different drivers. I am looking for a more universal approach if possible. That will depend on the impedance and response variations.

I have been able to obtain a tighter response within +- 1 db on the horn at a granular level with dedicated EQ. This is best arranged for a specific driver.

Taking loudspeaker measurements always outside always gathers the attention of onlookers.

Hi Rob,

In case you are interested I have looked into installing Leap 5 in a new machine with my XP PC becoming more ancient with the future potential of failure like my AT PC.

A local supplier has offered to install Windows 7 Ultimate with legal XP emulation in a new Mac Pro. So Leap will run in a virtual XP environment. My existing Mac Pro is a 2016 so l will kill two birds with one stone. I prefer the Mac environment and it links to my other Apple devices.

I think they will install Parallels or similar.

The portability of Leap 5 means l can crunch the data on move or while travelling as well as mobility for measurements.
Ian

Quote:

---

Originally Posted by Ian Mackenzie

Hi Rob,

I received the files thank you. Interesting.


I also need to compare a conventional compression drivers response to the 2430. If you can send a FR file of the 0476 on the M2 that would be great thanks.

---

Sure I have several have to figure out the ones I used vs threw out. If I am not mistaken more robust low end on the standard 4" drivers.

Rob :)

So is that lizard as big as it looks??

Hi Rob,

The lizard is about 18-24 inches long.

That Lizzy's a looker!

The spiky bulge on the back of her neck looks like one of your speed bumps measurements.

I have attached below some driver impedance comparisons below. If time permits and Scott and Rob are able to send frequency response measurements of the 2451 and the 0476 driver I will post those also.

Notes:

The purple plot of the 2430 on the M2 with parallel voice may not be accurate because my LMS analyser PC was not functioning correctly at the time.
I will make another impedance measurement of the weekend.

As can be seen there are three impedance peaks on these curves. What these impedance curves they mean and how they impact on the design of a passive network is complicated.

A key point is that lower impedance curves will result in a higher sensitivity driver than the high impedance curves.

Ian

Quote:

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Originally Posted by Titanium Dome

That Lizzy's a looker!

The spiky bulge on the back of her neck looks like one of your speed bumps measurements.

---

Hi Dome,

We don't do flat around here. Flat is boring. Nothing to listen to and gripe about.

Leads to dementia...Lol.

Flat is the death of Hifi because people stop buying stuff.

Because the Lizzy says its so!

Ultra Simplistic Passive M2 Crossover

There's always room for improvement. This idea was discussed when I was collaborating with Nelson Pass and Greg Timbers for a simple passive CD EQ to be used with active crossovers.

I have taken the approach further to realise a full working network. Attached are simplified schematics comparing the two high pass passive networks for comparison.

This is a very simple passive crossover and it has very few vices. Its relatively immune to driver and network impedance interactions.
Its reasonably inexpensive to make and not a lot to complain about in terms of the response variations. The divisions are 5 db.

It you are running a valve amplifier or what ever this network has very smooth impedance curve .

Best of all the diy user can very easily tweak the network to their liking with REW.


Edit:

Ultra Simplistic Passive Crossover Description

The easiest way to describe how this network functions is to look at the raw 2430 frequency response (top curve).

The first stage to the left is a 4th order LR passive filter which combines with the driver's acoustic slope to form a 6th order high pass slope.

Next there is a passive voltage divider with dual duties. The divider reduces the overall voltage to the driver and level shift the load impedance up the following passive EQ and the driver to deliver an amplifier friendly load.

Looking at the raw driver response there are two main areas that require equalisation. A peak at 850 hertz and a broad hump centred at 3,000 hertz.
There are a couple of approaches to achieving the EQ. The role of the EQ is to pull down the voltage to the driver in the area of interest. The most common method is to shunt a series LCR resonance circuit tuned and defined by the centre frequency, bandwidth and attenuation. At resonance the LCR conducts current which is limited by a resister stopper R. This approach is limited by the minimum acceptable load impedance.

The second approach is a parallel LCR tank circuit. The tank circuit is connected is series with the load to reduce the voltage to the driver in the area of interest. Like the series LCR circuit the parallel LCR tank resonance circuit is tuned and defined by the centre frequency, bandwidth and attenuation. At resonance the LCR reduce the current conducted which is limited by the stopper resister R. This circuit forms a high series impedance and causes a voltage drop in the area of interest. Two tank circuits are used to flatten the raw driver response.

The next stage has the task of equalising the fall in the driver response about the mass rolloff point of 4,000 hertz. The most common approach to is to shunt a capacitor across the preceding voltage divider. The disadvantage of this approach is that it loads the impedance down at high frequencies. The alternative approach is to use an LR shunt circuit which at frequencies below its resonance shunts current to ground limited by the stopper resister. This caused a voltage drop in the area of interest across the previous voltage divider limited by the stopper resister R. By empirical adjustment and optimisation the HF Level and Tilt in the response can be accurately set by adjustment of the L values. The R value acts as a level shifter at frequencies below resonance forming a tilt on the response up or down above the crossover frequency.

The overall circuit is elegant in its simplicity but requires considerable thought in its execution.

Ian

Whoops! The green curve is a 435Be on the M2. That's what happens when you are not careful labeling things as you go!

Rob :)

Hi Rob,

No worries. I will edit and remove.

I received some files from Scott this morning. Thank you.

I have had a look at the 2451 measurements.

I think the best way forward is to put it out there and compare with the 2430 with the 2451 based on the data available. I checked several files and the results are consistent. When Robert is able to send his 0476 files we can do more comparisons then.

Notes
This comparison was for a high level look at the response measurements by REW. We don’t want anyone jumping out a window unnecessarily yet…Lol. I understand Scott’s measurements are close or near field. My measurements are at 1 metre.

There are obviously some differences that need further thought and investigation. The 2430 green curve and the 2452 green curve are attached below.

You can see the 2451 curve has more of a bump at 3Khertz while the 2430 has a wider and larger hump. The 2430 extends lower with a peaked output at 800 hertz.

Once l have the data from these curves in Leap 5 with the high pass crossover objective line overlayed l will be able to make more definitive observations.

Hi Ian ( Rob ),

Here's sebackman's comparison of the 2430K ( on an M2 ) vs the 2451SL . The 2451sl is the darker top trace.

Attachment 90734

While sebackman's windowing makes things somewhat blurred below 1500hz, the overall response trend is still very visible >> and that is the 4" diaphragm has quite a bit more output below 2K ( which is consistent with the posted experiences of most others ) .

Here's RobH's 476mg measurement ( raw ) on the M2 horn ( top black trace ).

Attachment 90735

The 2451sl and 476mg measurements are more similar than different ( to these eyes ).

Also, the "Q" of the 3K bump is consistent in all 3 traces ( which makes some sense, since it appears to be an artifact generated by the M2 horn )

I think there's something is wrong with Scott's measurement ( and/or the fitment of his diaphragms ).
- He might want to look at the distortion profile of each individual measurement to try to exclude various user-induced problems.

A rubbing//binding diaphragm usually shows an obvious frequency-dependent spike in the 3rd harmonic trace ( typically getting higher than the 2nd harmonic trace ) while also ( in the worst cases ) hindering the generation of the driver's lower range of frequencies.

:)

PS Ian; within REW, use the little camera icon to generate custom pics for posting ( if you desire a cleaner way to post pics ).
- It's found to the top-left of the main display field.

Hello Earl

Thanks for posting Rob's comparison measurements between the 2 drivers. I forgot that he posted them. I agree that the posted 2451 measurement looks a bit out of family. Even when testing the 476Mg on the PTH1010 there was quite a bit more low end on a much physically smaller 100x100 waveguide. Same thing with the 2453H so we will have to sort it out.

My measurements are typically 1/6 octave smoothed but not windowed so you don't loose resolution on the low end of the drivers response curve. I find it difficult to get the driver to driver transitions right if you don't have the resolution. The windowing tends to smooth and shift the curve.

Odd about that 3K on axis peak??

Sent Ian the text file for the measurement you posted.

Rob :)

Interesting about the possible distortion. I left the slope filters on in the crown on accident and wonder if this is the issue. Here is a real quick measurement with the filters off compared to the original one I sent Ian. I started the sweep at 450Hz

Attachment 90736

Thanks,
Scott

Hello Scott

That looks better! Can you take another measurement from 100Hz to extend the roll off into the mud??


As far as low end on the 4" drivers. Here is a 2453 on a PTH1010 for comparison purposes.

Rob :)

OK, that’s good to know. I wasn’t really sure where I should be starting and didn’t want to ruin the diaphragm. When I originally aligned these I had the hardest time. Since the drivers were new and a diaphragms were new, I wasn’t sure which one it was but I ended up figuring it out by not using a star pattern for torquing but tightening one side and then the other. I’ll try and post some measurements in about five hours.

Thanks,
Scott

Hi Earl,

Thanks for chiming in and posting the comparisons.

In the absence of readily available comparisons l wasn’t sure what to make of Scott’s measurements.

Hi Rob, you raise a good point. I have my Windowing open and use 1/6 octave resolution.

Hi Scott, thank you for sending the measurements. As it turns out we now have an understanding on the data with Earl and Robert’s input. Incidentally l run all my compression driver tests down to 300 hertz and l’ve never had a problem with small level tests. I use 0.07 volts and scale up up the measurement 32 db. If you run your DATS3 impedance tests directly into the driver from 300 hertz with the horn mounted from 300 hertz it will be fine.
Great link for scaling your measurements
http://www.sengpielaudio.com/calculator-gainloss.htm

Rob S is away from the forums at the moment and has kindly given me access to his measurements.

I have a pair of 2451 driver coming towards the end of June.

It’s early am here. I’m out paddle boarding on the Maroochy River. I will have a look at the files this afternoon. I’m fairly relaxed about this project. Obtaining consistency with measurements of drivers remotely is always a challenge.

Talk soon.

Thanks Ian, unfortunately I only have the capability of running frequency sweeps in REW at this time. Luckily we have the impedance from Rob S which would be more reliable anyway. I still haven’t had time to figure out impedance measurements in REW.

Enjoy the water!

Thanks,
Scott

I have nothing to add, but it is nice to see all of this DIY action in the forum!


Widget

Quote:

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Originally Posted by srm51555

Thanks Ian, unfortunately I only have the capability of running frequency sweeps in REW at this time. Luckily we have the impedance from Rob S which would be more reliable anyway. I still haven’t had time to figure out impedance measurements in REW.

Enjoy the water!

Thanks,
Scott

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Hi Scott,

It was my first go at it. I fell off a lot and got lots of inspiration from everyone watching from the shoreline. Eventually l was standing on the board and paddling for about 2 minutes before l fell off in DEEP water. It was a scream 😱. Each entry into the water was a belly whacker. I then got more innovative and started falling off the board backwards.

This is the Land of beautiful tanned Aussie blondes btw so there is a possibility l was distracted..Bom Bom.

The river inlet is a bit like the beach side setting of the movie Jaws with a peninsula in the middle of Maroochy river inlet. On the turn of the tide the currents flow and can take you up the river or out to sea. There are apparently bull sharks and stingrays in the shallows. Fortunately there are no crocodiles in the Maroochy river.

Given the heads up from Earl l figure it would be a good idea to think about setting the stage for some common ground with our measurements before the project starts to get busy with numerous measurements.

DIY Measurement Work arounds - sharing and comparing curves with our diy tools ( Surviver Guide.)
DATS3
REW

Hi Scott, Do you have Dayton DATS3 ? I was trying to remember if the impedance file was yours?

Sharing Measurements
Anyway, the good news is l can import a DATS 3 impedance file into my DATS3 and export the file as Clio txt file. So this is a growse (Aussie expression meaning very good ) work around for sharing and comparing impedance curves, importing impedance data or exporting impedance data as txt file into a simulator such as Leap 5.

An impedance data txt file has three data columns and is typically 200 to 400 data points long.

Frequency Magnitude units (ohms or spl db) Phase

Similarly an REW FR response files can be shared with another REW user. So l was able to open your REW file you sent me and look the individual measurements you made perfectly. Using the file export menu data files can be exported as a txt file for import into a simulator such as Leap 5. But the data points should be limited to around 400. Make sure the text editor does not word wrap the data.

See the format above.

A few tips we can all contribute to as the project progresses.
The Curve Junkies Survival Guide - so we don’t go crazy.

When sharing a frequency response measurement :
Please advise in the email what you are sending?
Is it raw driver measurement? If any crossover filters are EQ was used in the measurement?

Test conditions:
In the email or in the notes section advise the distance of the mic to the DUT (device under test) and the level? In REW this can be expressed in several data measures such as DFS. Or the spl or the voltage. Then the user you are sharing with can interpret your data correctly or if the magnitude of the curve needs shifting.

The link l posted earlier is great for calculating db from voltage.

This is just a mention so we don’t go crazy with measurements flying in all directions…Lol

Once l warm up l will have a look at the files.

Talk soon.

Hi Scott, Rob and Earl,

This afternoon I put all the available curves together in three graphic files for a baseline view of what we have here.
There are two FR files. One with the data as is and one I normalised. I am not worrying about the exact levels at the moment. The 2430 with a nominal 32 ohm VC is the least sensitive of the group and its useable. I had to re format the REW exported txt files so Leap 5 would read it and my brain hurts. (beer o'clock here)

I felt it appropriate to use the file Scott sent me has its has relevant information on the M2 with the 2451 in the pass band for presentation at this time. Once I have Rob S files I will include them moving forward.

I'm reading between the lines here but I don't see any insurmountable problems setting up a common passive crossover to manage any driver for a "simple DIY M2 passive crossover.
The 2430 is a departure from the 0476 and the 2451 in its EQ requirements. That can be dealt with using a "Plug in" EQ circuit. The level matching can be dealt with using a table of resister values.

I'm open to ideas and suggestions on any approach to the crossover as there could be more than one flavour depending on individual circumstances.

For example someone might want just the passive EQ or a straight 24 DB LR network with passive EQ. Or basic but diy friendly variable tonal level shifting like I posted in the simple diy passive crossover aka 3134 - 4430 approach. The thing is its already been called out that some diy tweaking in the tonal balance could be required. I'm mindful of that while ensuring the basic crossover transfer function is as good as it can be made.

Edit: I have upscaled the Jpeg images, transferred and processed these measurements so they can be viewed and used in LinearX Leap. These raw driver response measurements have the response magnitude normalised for comparison of the JBL 2430, 2451 and 476 compression drivers. All measurement are of the drivers mounted on the M2 horn. Note. the 2451 measurement has a Crown DSP crossover filter in use.

Hi Scott,

Please find below a result I obtained tonight with the Ultra Simplistic M2 Passive High Pass Network.

Attached are the FR, voltage drive and impedance. Once I obtain the full 2451 response from Rob S I will then complete the HP filter. The HF tail is a measurement problem I think. It can be resolved if not.

I am confident I can set you up for success with a network for your 2451 driver including a range adjustment for you to consider in your subjective appraisal. The attached FR curve is within 1.5db from 1296 hertz up to 6.696khertz and then a planned reduction of 2 db on the HF response per hints from GT. There is latitude for adjustment to suit the individual.

Edit: I have re scaled the Jpeg images and updated the files notes for clarity. Note this images are for illustration only of the passive EQ functionality of the M2 Diy Ultrasimplistic passive network.

Network Modifications:
The network can be modified for virtually any scenario and / or adjusted out in the field by using REW to make measurements with detailed instructions provided by myself. I can also modify the network using measurements from the user on site and provide technical support. This will a game changer for those interested in diy updating or amending passive crossovers for any JBL loudspeaker system

https://tapeop.com/interviews/btg/10...-manley-bonus/

Quote:

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Originally Posted by Mr. Widget

I have nothing to add, but it is nice to see all of this DIY action in the forum!


Widget

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H Widget,

Yes its really cool.

I've also been looking the measurements "Space " and how this information can be shared. I have posted how this can be done.

With portability of the data at a diy cost via DATS3 and REW this type of activity can be embraced by anyone here. Whether you are a bystander, an on looker, thinking about or considering taking the next steps. Just hanging out. There is little bit of a learning curve but its not hard work. Its fun.

My focus here is on the JBL stuff we love so much. Its about being enabled & engaged in something you enjoy.

Those tapped transformers are fairly straight forward to model btw.

Ian

Hi Robert,

Please find attached the result of using the 476 files you sent with the Ultra Simplistic 36db LR passive high pass crossover.

The principle is the same as Scott's 2451 file application. In addition I have added a tuned VHF LP filter to trim the top end. Not that you would hear it. More for the cats and bats in the neighbourhood. This is more just to illustrate to the guys what can be done.

No low impedance problems and smooth voltage drives as can seen from the attachments. I think its pretty smooth and subject to the original measurement.
A subtle EQ slope shelving at 2db was applied above 5 hertz to illustrate what can be done for a particular circumstance.

Edit : To everyone
These images for for illustration only to show the functionality of the M2 Diy Ultra-simplistic passive network. The network can be modified out in the in the field by using REW to make measurements and with detailed instructions provided by myself. I can also make modifications remotely with the measurements made on site by the user. This might also include validating your stock or diy network or the system response for particular circumstances. This is a game changer for anyone considering or thinking about updating or wishing to modify their JBL system network. The REW measurement software is free and I found it relatively easy to use. The results are far better then I expected. REW is fully supported with a Q & A and help on the REW www website. All you need is the Minidsp microphone which can be ordered online if you are a Mac User. Details for Windows ussr are provided on the REW www site. All you need to do is send your GF or spouse out shopping with your credit card for the arvo..LOL. Have a Saturday arvo audio met with friends while your communicating with Down Under.

Ian

Just a heads up I will edit and make these images larger later today. I have to update some settings in the software. If you would like pdf attachments for hi resolution download images I can also do this if required.

Hi Ian,

Everything is looking real good. Thanks for posting the progress. For future learning I will still be trying to replicate what you receive from Rob S in REW.

The best part of being on the other side of the globe are the fresh measurements to look at here when I get up. Better than coffee.

Thanks,
Scott

Hi Scott,


I hear you. It can be addictive. Sometimes l just keep going and the time just flys. It’s fun connecting with people who are interested in this type of thing.

Once l have my new laptop l will be able to do this thing more in the moment rather than late in the day. I may post the odd image of Noosa Heads beach and other interesting places like Fraser Island which is a really cool place to camp, take a beach drive and off road 4wd tracks to various lakes. One of the lakes is really nice. Audio measurements in the Outback.

https://www.visitfrasercoast.com/product/lake-mckenzie/

Up north we have the barrier reef and other cool stuff like the Outback Savannah which l visit. Beautiful gorge’s with water to cool off and relax.

PS. I still need my large cappuccino.

Quote:

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Originally Posted by srm51555

Interesting about the possible distortion. I left the slope filters on in the crown on accident and wonder if this is the issue. Here is a real quick measurement with the filters off compared to the original one I sent Ian. I started the sweep at 450Hz

Attachment 90736

Thanks,
Scott

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Hi Scott,

Thank you for posting this measurement.

If you have time email me this REW file. I will have a squiz at the file once I have eaten my prawns. Then add the passive high pass filter in Leap 5 for you.

Ian

Block diagram of network attached.

My 2451 drivers arrived today.

I will check them out over the next couple of days and see how they go on my M2 horns.

Those look real nice!

Getting the 2451 compression driver ready for testing tomorrow. Robert S kindly provided these flanges.

Unfortunately the studs on this particular driver where slightly bent because the idiot who used it last forced the horn off instead of lifting the horn flange carefully of the studs. He was not the sharpest tool in the shed obviously. This meant l had to carefully straighten the studs before l could fit the flange.

Just for grins l have started a passive of the JBL DSP EQ settings of the 2430 fitted to the M2 horn.

I have not finished yet. I am up to about 7000 hertz. The response is starting to look as smooth as a polished mirror. The downside it’s requires a number individual of passive EQ filters.

Quote:

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Originally Posted by Ian Mackenzie

My 2451 drivers arrived today.

I will check them out over the next couple of days and see how they go on my M2 horns.

---

Really cool work you're doing here Ian - thank you! I'm following with great interest, as I'm considering a 2216nd + 2451 build, so lots of useful info here even for fence-sitters like myself who aren't 100% committed (yet!?) to building an M2 clone.

Part of the reason I'm interested in going 2216nd + large format jbl (I'm leaning toward crossing slightly lower than the M2 using a Yuichi or Tad derived horn), is because I haven't seen any hi-fi specific projects documented using 2216nd in place of the 15" Altecs I'm accustomed to working with, and very little info comparing their preformance, even if only subjectively. There are the M2 clones of course and some documented home theatre projects, but I'm aimimg for strictly passive and will be using 6 cu/ft Altec 612 Iconic cabs + horn on top.

All to say, thanks for your efforts and looking forward to seeing more!

No worries.

Over on Diyaudio Lyn Olsen did a very long thread on an Altec 416 with an Oblate wave guide. The Altec woofer trades efficiency and a larger enclosures for Xmax low in a smaller box.

In other words you need 4 x the power to run a 2226nd. I’ve never used or build a Yuichi horn But l did correspond with Yuichi. Unfortunately l never got around to making a Yuichi horn. I would probably build a Joseph Crowe horn which is an improvement on the Tad TH4001 horn,

Let me know when your read and l can do a 36 db 650 hertz crossover for just like Tad used.

Ian

I posted over on Diyaudio.com in one of Patrick Bateman threads proliferating the virtues of the M2 style horn. It will be interesting to see if Patrick posts here.


https://www.diyaudio.com/community/t...3#post-7055711

Quote:

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Originally Posted by Baaronj

....projects documented using 2216nd in place of the 15" Altecs I'm accustomed to working with, and very little info comparing their preformance, even if only subjectively.

---

Welcome to the forum. Not sure if you have seen this post yet, some good comparison in it.

http://www.audioheritage.org/vbullet...l=1#post364835

Thanks,
Scott

Quote:

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Originally Posted by Ian Mackenzie

.... Unfortunately l never got around to making a Yuichi horn.

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I will also join this club. Beautiful stuff though.

Hi all those viewing this thread.

Before l can start the 2451 measurements l need to fit the 2451 driver to the flange.

But there’s a problem Houston. The studs are too long and won’t allow the horn to sit on the flange.

Always plan your space station repairs before you do your space walk.

So l had to figure out how to solve the problem. After attempting the dry fit the flange and the driver the immediate problem was removing the studs. They are way too long. About two inches. It wasn’t easy to remove the studs and my guess is seller couldn’t remove them. But l got them out without damage to the threads with some controlled force using strong grips.

Dry fitting the flange to the horn throat again with the 2451 driver l firstly lined up the horn mounting holes with the metal flange holes. However, it’s easy to confuse the flange horn mounting holes with the driver mounting holes. So l used a black marker and tape on the drive to locate the driver. Before l can proceed l need to obtain some shorter one one inch length studs to mount the driver from my hardware outlet.

The flange should also be set off from the plastic mounting posts with some shims or washers as there’s a fine gap when the flange centre hole is flush with the horn throat. Otherwise you may damage the horn throat when tightening the flange bolts.

It’s fiddly so sketchy your time if you plan to try different drivers on the M2 horn.

Edit:

I’ve ordered some shorter 1/4 UNC set screws which l think will be much better. I hope they will arrive later this week.

1/4" x 20 TPI UNC Coarse Plain Black Grade 14.9 Cup Point Socket (1/8" Key) Set Screws Grub ANSI B 18.3

https://www.boltandnut.com.au/1-4-x-...iABEgJl0fD_BwE


Ian

I received the stainless steel 1/4 inch unc set screws (one inch) with 1/8 inch hex Allen key wrench size. This solution seems a more satisfactory than the studs with a slotted end. The slotted end wasn’t strong enough to cope with the torque necessary to remove the studs and failed. I might put some anti cease lubricant in them in case they need removal at some stage.

Hopefully if the rain eases over the weekend l will post some measurements.

Unfortunately it’s going to be raining here till next Thursday so l will post some indoor measurements over the weekend. It’s not deal but will give an indication of the 2430, 0476 and 2451 characteristics on the M2 horn.

We actually have the same rain schedule as of last night. Thanks for the update.

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