2-way crossovers

[89-300ce]

I'm thinking of building my own crossovers. I'd like to run the 511b horn/BMS 4550 driver out of phase with the 2235 or ME150H and use a baffle step on the woofer to time align both drivers at 800Hz. I kinow I should use as steep a slope as possible when trying to time align this way, but too steep a slope will show the crossover more. I'm thinking of a second order Bessel.

Will Zilch's HF attenuation for the 811b/BMS 4550/N-800F (1200Hz) but adjusted for 8 ohm drivers work?

Is this a steep enough slope to not get out of phase cancellations as I move away from the 800hz crossover point?

Is the Bessel an appropriate curve to integrate the horn and cone?

Jorg

[Zilch]

http://audioheritage.org/vbulletin/showthread.php?p=163687#post163687

I believe you'll find its asymmetry, highpass being 1200 Hz, lowpass 800 Hz, performs part of the compensation, which is completed by the final parallel trap.

The serial notch knocks down a 19 khz spike characteristic of BMS drivers on these horns.

Compensation portion constructed and retested here:

http://audioheritage.org/vbulletin/showthread.php?p=165377&#post165377

Some JBL ~800 Hz LF filters:

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L200B%20ts.pdf

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/S3100%20ts.pdf

http://www.jblproservice.com/pdf/Network%20Schematics/3110%20Network.pdf

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L300A%20Summit%20ts.pdf

[89-300ce]

Thanks Zilch,

I'm trying to work my way through this.
Is there a freeware calculator that you can enter component values and get frequency? I can only go from frequency to components and it's a pain to work it backwards.

Jorg

[Mr. Widget]

Is there a freeware calculator that you can enter component values and get frequency?Here is a calculator that does your basic textbook filters... easy to use and it works pretty well. It isn't exactly what you are looking for, but you can probably make it work for you.

http://ccs.exl.info/calc_cr.html


Widget

[89-300ce]

Here is a calculator that does your basic textbook filters... easy to use and it works pretty well. It isn't exactly what you are looking for, but you can probably make it work for you.

http://ccs.exl.info/calc_cr.html


Widget


Yes, thanks, I can make it work. It's just a pain. My numbers never seem to come out exact to the schematics. The coil and cap values never seem to match the network schematics. For the HF driver for instance. The cap determines the Hz and the coil the slope? So if the cap is 1200Hz and the coil number doesn't match the calculators it means they used other than a standard 16db slope?

Jorg

[Zilch]

The slope is fixed by the topology.

The Q is variable, and chosen in combination with frequency for the specific design.

The "textbook" transforms are rarely optimum for any given system.

They are merely points on continua, by this perspective....

[speakerdave]

I'm thinking of building my own crossovers. . . .

To begin to get a sense of what's involved from an informed perspective, read this:
http://sound.westhost.com/lr-passive.htm

David

[89-300ce]

The slope is fixed by the topology.

The Q is variable, and chosen in combination with frequency for the specific design.

The "textbook" transforms are rarely optimum for any given system.

They are merely points on continua, by this perspective....

So I should use tested values like in the JBL 800Hz LF crossovers in the links provided.

Won't the 800Hz lowpass and 1200Hz highpass create a dip at crossover ?

Jorg

[Zilch]

Won't the 800Hz lowpass and 1200Hz highpass create a dip at crossover?It depends upon the response characteristics of the drivers, horns, and cabinets used. What ultimately matters is the acoustic response, as provided by the elements in combination.

Run the numbers on the 846A and 846B crossovers. What frequencies do you come up with, LF vs. HF? How can that work?

Read up the link Dave just posted.

Referring back to earlier discussions, you need measurement gear to do this, and experience using it, unless you're willing to live with replicating previously proven designs by others, which you've now discovered are not textbook.

You can't just throw drivers and crossovers in boxes and expect an optimal outcome without doing the requisite design engineering, which may involve multiple iterations.

What's my approach to this? Remember that I'm the Quick and Dirty DIY guy, and others do it differently. Make your best educated guess at what will work, based upon what has worked for others. At some point, you have to put down the books and calculator, recognizing that you may have to pick them up again, many times. Build it, measure it, listen to it, refine it as you learn more, trying other options. It's never actually done, but you may enjoy it all the while.... :thmbsup:

[89-300ce]

So the journey is the reward?

Would the combination of L200 LF filter ( if I go 2235 ) with the N800-8k HF filter and your compensation be a good start point for this project?

If I found I needed to cross the HF lower I would have to modify the notch filter to extend the attenuation down?

I would keep the zobels as they are?

What would you recommend as a starting place for hardware and software test equipment for this DIY journey?

I have a 200w Sumo and a 50w Musical Fidelity. Might it make more sense to spend the test equipment money on a bi-amp setup? This bi-amp would be flexible enough to accomodate other two way's I might try to mess up down the road? Rod Elliott's article sure makes that seem attractive.

Jorg

[speakerdave]

Active crossovers (low-level or line level) do avoid some of the problems passive crossovers (post-amp, or high-level) have interacting with the electrical characteristics of the drivers, but off-the-shelf they are generic or textbook in the sense that they do not take into account the true acoustic performance of the real world drivers in question, because they assume flat response in the pass band and at least an octave into the stop band. That is almost never true, especially in a two-way.

Please understand that I am not presenting myself as an expert on this, but rather someone who is one-half step, perhaps, ahead of you in this learning process.

You could do everything Rod Elliot suggests and it would still only be an educated guess unless you have some acoustic test equipment (like CLIO and a suitable room to use it in) to provide yourself with a feedback loop on the acoustic side of the transducers.

No one can really answer questions about the interaction of specific drivers and existing crossovers unless they have examples on hand (that perform the same as yours) and are willing to do the testing, a very time consuming process. But generally, for example, the low pass filter for the woofer is designed in relation to the acoustic performance of the driver in the high pass section, so it will not work to take the low pass from one system that used your woofer and the high pass from another system that used your tweeter and splice them together, even if they were designed around the same crossover frequency. That would at best be a starting point that would need to be evaluated with acoustic testing of the driver combination you are using.

Generally speaking it is better to copy an already engineered system.

For me the only way all this is worthwhile is if you are trying to DIY a very expensive SOTA system. Of course there the risks are even greater because of the cost for drivers. But, nothing ventured . . . .

That is, at least for now, the state of my apprentice understanding on this.

As for using standard electronic crossovers--can it be done? Of course; it has been done many times, and people have often found them satisfactory.

You might find it informative to read the manual for the 5235 JBL electronic crossover.

http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/JBL-5235%20manual.pdf

David

[4313B]

Thank you for the post David! Very nice! :yes:

[Zilch]

So the journey is the reward?Indeed.


Would the combination of L200 LF filter ( if I go 2235 ) with the N800-8k HF filter and your compensation be a good start point for this project?It's L200B, actually, an important distinction.

I posted several 800 Hz crossovers so that you could see they were all different in detail. You'll have to start with your own "best guess." I have the L200B LF filter running a system using 2235H here, yes. Is it optimal? I don't know. Everything is "developmental" here. I'm not there yet.


If I found I needed to cross the HF lower I would have to modify the notch filter to extend the attenuation down?Not likely. Look at the BMS factory curves. They're down at 1 kHz already. The only way to know is to measure.


I would keep the zobels as they are?The zobels are often not textbook, either, as they are sometimes used to fine-tune the filters. That's also an empirical determination.


What would you recommend as a starting place for hardware and software test equipment for this DIY journey?You need a high-resolution RTA, at least. I started with a Behringer DEQ2496 ($300,) and still use it. I found its built-in EQ with AutoEQ function convenient for development work, telling me how much to correct, and where. There's also computer-based ones like TrueRTA.

You also need Woofer Tester 2 or Pro.


I have a 200w Sumo and a 50w Musical Fidelity. Might it make more sense to spend the test equipment money on a bi-amp setup? This bi-amp would be flexible enough to accomodate other two way's I might try to mess up down the road? Rod Elliott's article sure makes that seem attractive.Yes. I'm using a Behringer CX3400 ($130) right now. Measurement HF amp is Sonic Impact Super T-Amp, LF a pair of 40-watt JBL 6210. For listening, it's different setups.

[4313B]

So the journey is the reward?

Indeed.Sometimes I wonder if some of you guys are using crack pipes that are long past their expiration dates.

Try listening to some finished product sometime...

[JBLRaiser]

Quote:
Originally Posted by 89-300ce http://audioheritage.org/vbulletin/images/buttons/viewpost.gif (http://audioheritage.org/vbulletin/showthread.php?p=173319#post173319)
So the journey is the reward?

Indeed.
Yes Grasshopper.:homer:

[4313B]

:barf:

*****

Oh, I see where that came from...


It's never actually done, but you may enjoy it all the while.... :thmbsup:No, I would imagine most people have an endgame in mind.

[Zilch]

"Open-ended" is apt.

There IS no product, all ongoing upgrade.... :p

[4313B]

"Open-ended" is apt.

There IS no product, all ongoing upgrade.... :pYou're so silly. It's quite tiresome.

[Ian Mackenzie]

Tireless is perhaps more apt.

Jorg,

How are you going?

I looked at your start post and my first clue was what is the native response of the BMS driver on the Altect 511 and the 2235 on the baffle you propose to use?

As pointed out by Dave measuring and working all this out is a bit of an issue unless you have a significant resources at your disposal.

I did a quick yahoo search of the 4550 driver and interestingly found this link to some data and Bill Martinelli's wood horn page

http://www.woodhorn.com/BMS/bms_4550.htm

http://www.woodhorn.com/diy.htm

May I (respectfully) suggest you attempt to use this as a powerful resource for the development of your project. You may also find that using one of Bill's horns will assist in realising the full potential of your compression driver.

http://www.woodhorn.com/completespeakers.htm

[4313B]

Tireless is perhaps more apt.No, not in this particular instance. "Tiresome" is the description I most often hear, usually preceded by "real". I suppose it's too bad really, well, at least given the venue. We've had this discussion with respect to various other much larger forums and there's just not a whole lot to be done about it. :p

Anyway, whatever. :)

[Zilch]

Here's BMS 4550 on 511 (also 811) horns:

http://audioheritage.org/vbulletin/showthread.php?p=159290#post159290

Here's Earl's explanation of those curves:

http://audioheritage.org/vbulletin/showthread.php?p=159367#post159367

Here's the impedance curves:

http://audioheritage.org/vbulletin/showthread.php?p=164554#post164554

Here's the compensation filter w/846B XO, including voltage drive:

http://audioheritage.org/vbulletin/showthread.php?p=163687#post163687

Here's the sim of the 16-Ohm version:

http://audioheritage.org/vbulletin/showthread.php?p=164709#post164709

And here's the filter as-built:

http://audioheritage.org/vbulletin/showthread.php?p=165377&#post165377

Scroll up to #745 for the parts list.

Frankly, I don't understand why I deserve a rash of shit for this.

Whatever.... :dont-know

[Ian Mackenzie]

So the journey is the reward?

Would the combination of L200 LF filter ( if I go 2235 ) with the N800-8k HF filter and your compensation be a good start point for this project?

If I found I needed to cross the HF lower I would have to modify the notch filter to extend the attenuation down?

I would keep the zobels as they are?

What would you recommend as a starting place for hardware and software test equipment for this DIY journey?

I have a 200w Sumo and a 50w Musical Fidelity. Might it make more sense to spend the test equipment money on a bi-amp setup? This bi-amp would be flexible enough to accomodate other two way's I might try to mess up down the road? Rod Elliott's article sure makes that seem attractive.

Jorg


Jorg,

The later might work our best with your potential future plans

Marchland have some reasonable active crossovers. You can arrange custom crossover points with some of their models.

On software there are some RTA software packages on the internet that you can down load and try out like SmartLive. Go buy an Behringer ECM8000 mic and and a small phantom powed mic preamp and you can do some basic measurements via the soundcard in your PC.

If you want to play around with passives there is a firm that sells an experimenters adjustable passive crossver boards..they were at the CES. You can find their advert in AudioExpress magazine. Sorry I don't remember the name.

The intent of my earlier post was that you either have plenty of time to learn, fiddle and hopefully get it right or rely of someone else's hard work and use a pre designed system that already sings.

In that respct Bill's work is very impressive....as can be seen from his web pages. They would appear to have good WAF which is always an issue with diy horn based systems..trust me!

On your earlier comments about time alignment the issue is more about getting an even on and off axis vertical polar response in the crossover region.

The 511 horn has far more resonant and response lobing issues that would benefit considering alternative horn types and large format drivers over any attempt at time alignment.

Again look at Bill's designs, he appears to use BMS drivers so it may pay to email Bill for some feedback on your particular BMS driver.

Ian

[Zilch]

He has the 511 horns, Ian, and wants to work with them.


Advice noted, but too late. I'm now the proud owner of some 511b horns.

Then I am decided.

511b, BMS 4550, 2235, N801-8a

I'm saying, "Fire 'em UP!"

He'll soon know if those are issues for his system.... :thmbsup:

Here's the precedent thread in which the basic design was developed:

http://audioheritage.org/vbulletin/showthread.php?t=16946

[4313B]

Frankly, I don't understand why I deserve a rash of shit for this.... :dont-knowYes, we know that. It's basically a perception problem that we've discussed to death over the last three years.

I've decided to delete the other three paragraphs I took the time to type in this post because I realized that they would take an additional three paragraphs to explain further and I just don't have that kind of time right now.

[Zilch]

Well, PM them to me, then.

[Couldn't hurt.... :) ]

[Ian Mackenzie]

Ah we where posting at the same time.

Zilch, with all your posting can you honestly say you auditioned the 511 and the 2235H woofer?

The 511 was primarily designed for use in particular Altec systems.

On ME150H this a similar exercise with support from Earl

http://www.audioheritage.org/vbulletin/showthread.php?t=10873
http://audioheritage.csdco.com/vbulletin/showthread.php?t=6006

And a response curve of the ME150H which was used in particular JBL systems as we know.
http://www.behringer-electric.de/ls/RareInfosME150H.htm



From Jorg's posts it would appear he wants perfection and he will need to undertake a reaonable amount of time, expense and effort to approach that goal.

No doubt some would say buy a DEQX to make it go.

I am only suggesting a wider perspective on reality before he embarks on his journey.

As you know the 2344 horn was created for a reason.

Yes I saw that link just now. Why was this thread not link in the first instance??

It would appear everything that has been discussed here and already been looked at over there.

Its a mess.

[boputnam]

Try listening to some finished product sometime...I concur with that. Live with it, and really understand it's performance. Subtle "adjustments" can reap remarkable changes in performance - good, or bad...


No doubt some would say buy a DEQX to make it go.Agreed. And that there poses a question: Does one accept an imperfect design because one can EQ the "hell" out of it to make it perform satisfactorily? Sure, the DEQX technology can achieve remarkable end-results, but it does so dealing with symptoms of problems...

:dont-know

[Zilch]

Zilch, with all your posting can you honestly say you auditioned the 511 and the 2235H woofer?Nope, LE14H-3 mostly, over the course of several months. I'll set up to do that (511 & 2235H) here, now that you mention it, tho.

It'll be couple of weeks listening to it for me to give that system a fair audition. I doubt I'll have much to add in the meantime.


Why was this thread not link[ed] in the first instance??Don't look at ME, Ian.

It's certainly not MY style.... :p

[boputnam]

Sure, the DEQX technology can achieve remarkable end-results, but it does so dealing with symptoms of problems...

:dont-knowQuoting myself... :o:

Those of you interested in perspectives on DEQX, can read/participate in an intense discussion on Gunness Focussing (http://srforums.prosoundweb.com/index.php/mv/msg/23687/0/20/4540/) on ProSoundWeb, where the DEQX is, at the least, anecdotally addressed. The discussion there, is very interesting and IMO universally relevant for us all.


Real time convolution of and impulse with the signal is merely the means of output. Systems like the DEQX I would call brute force convolution. Stick a mic up in a room, take an impulse, assume that everything about it is LTI and spatially invariant, invert it, and then convolve with your signal.

All you have achieved then is cleaning up the signal at one point in time and space. Move the microphone a few inches, or increase the level of the system outside of its nicely linear range, and this correction no longer applies.

Dave (Gunness) has systematically disassembled the beast, looking at behavior in the phase plug, horn, woofer modal behavior, etc. He has figured out what is spatially dependent, and what is not, what is LTI, and what is not.

Thus you end up with a product that may not correct "everything" ala DEQX, but is has fixed the problems that show up as LTI and spatially uniform, including several pesky energy storage issues in cones, horn flares, and phase plugs. ... Dave Gunness is due a lot of credit here for his analysis techniques.

Phill Graham
Doctoral Candidate
Georgia Tech

Grist for the mill...

[Ian Mackenzie]

Agreed. And that there poses a question: Does one accept an imperfect design because one can EQ the "hell" out of it to make it perform satisfactorily? Sure, the DEQX technology can achieve remarkable end-results, but it does so dealing with symptoms of problems...

:dont-know

Exactly my friend.


Nope, LE14H-3 mostly, over the course of several months. I'll set up to do that here, now that you mention it, tho.

It'll be couple of weeks listening to it for me to give that system a fair audition. I doubt I'll have much to add in the meantime.



Okay, I look forward to reading your impressions at some point

Perhaps you can see now why I might have been seen on the face of it to be overtly "anal" in another thread where seemingly a beginner leaps for what he thinks is the easy way out or ultimate route to cleansing a dated but mature design with digital technology.

The passer by then reads this some time later ...and well you know the rest.

Ian

Sorry but I do confess to being something of a disciplinarian with this sort of thing!

[Mr. Widget]

Those of you interested in perspectives on DEQX...As a DEQX user, I'd like to add... used as directed I found the DEQX to be a bit of a disappointment. However once I figured out what it was doing, I was able to make it behave quite admirably... not a one box panacea, but a quite competent and useful tool.


Widget

[boputnam]

...once I figured out what it was doing, I was able to make it behave quite admirably... not a one box panacea, but a quite competent and useful tool.I have heard it, and agree.

My point was merely that as good a device as this is, if there are design issues that should be / could be dealt with, all the better. Any such device will be even more effective the better the cabinet design, construction, transducer compliment and deployment.

[89-300ce]

Sorry about not linking the two threads. I’ll make sure to reference my questions better in the future.

I’m not privy to some of the dynamics between poster in this group so I’m at a bit of a loss in understanding some of “what’s going on?” in parts of this thread.

511B

My wife, no longer practicing as a trained chef, has often told me that “you eat with your eyes”. Not literally of course. I had considered the waveguides and bi-radial horns early on but, to me, the look of the Altec sectoral horns are the hallmark of a vintage 2-way. Reading of Zilch’s work done here with the BMS drivers improving the horns extension seemed like too good a thing to pass up on. I could always discard the BMS drivers and revert back to Altec (288-8K) if they didn’t work out.

The most cohesive plan for me would be to build some model 19 clones and apply the BMS drivers. I do like the look of the large 511b and can fit them and BMS drivers into a slightly modified Model 19 cabinet with the 416-8b and N1201. I would end up with a very attractive cabinet and a workable combination. The down side is that 416-8b’s seem scarce and I have 5” of extra horn length to deal with. At worst I’d build another horn box and put in some 811b’s instead.

The 2235 is a vintage JBL driver that is known for it’s characteristic classic JBL sound and deep extension. Cores that can be re-coned into 2235’s come up for sale regularly.

I find the possibility of integrating these two readily available and reasonably inexpensive iconic Altec and JBL components attractive. The BMS drivers HF extension and low cost seems like icing on the cake.

I’m an absolute novice in this DIY world and I naively assumed I could run a few crossover programs, calculate a box size, bolt in the components and get it right. I now realize that it’s not nearly that simple. But just the process of realizing my own ignorance has been fun. Based on that I believe that this journey can be enjoyable for me but only if I get to look at some nice scenery on the way. I’d hate to spend my time slogging though a wasteland only to be told in the end that I had taken a path with little chance of success to start with.

People with greater experience and more resources than I come here to play. I’m just going to keep pumping you for information to help me make up my mind which path to take. That was the purpose of my first post

“2-ways” linked below.

http://audioheritage.org/vbulletin/showthread.php?t=16946

Jorg

[Ian Mackenzie]

If you are looking at a traditional JBL alternative consider a D130 or a K145 as they are more in keeping with the sensitivity of the Altec 416. The 2235H is a totally different beast and would not necessarily offer the best balance of sensitivity and bandwidth when used with the 511/811

[speakerdave]

The Altec 511b has a 1" throat entry. The Altec 288 requires 1 and 1/2 inches.

I don't think anyone would suggest you use the JBL 2235 up to 1200 Hz.

The Altec 416B's have been getting bid up pretty high on ebay lately. I would suggest you look for some 416C's or consider the new modern equivalent from Great Plains Audio, inheritors of the Altec Lansing legacy and some of their machinery and technical talent. They have crossovers too.

David

[Ian Mackenzie]

Hi Dave,

A while back (9 yrs) I sold a pair of mint 515's for $500 each to a local audio club member. Supply and demand I guess.

I was looking at Great Plains this afternoon. Their new 604 looks nice.

I guess it depends on whether he wants Altec legacy or a moden day technical similar component. I mean B & C make some nice woofers that would work equally well.

Ian

[89-300ce]

If you are looking at a traditional JBL alternative consider a D130 or a K145 as they are more in keeping with the sensitivity of the Altec 416. The 2235H is a totally different beast and would not necessarily offer the best balance of sensitivity and bandwidth when used with the 511/811

I've heard D130's and K140's and wonder if you could describe how they compare to the 2235H's. I know it's difficult to convey some of this information in writing. As for bandwidth, don't the 511 and 2235H both do 800hz?

Jorg

[89-300ce]

The Altec 511b has a 1" throat entry. The Altec 288 requires 1 and 1/2 inches.

That was in reference to EarlK's suggestion to use a 288-8k on a modified 511 horn. I've often heard this driver praised on the Alted boards.



I don't think anyone would suggest you use the JBL 2235 up to 1200 Hz.


800Hz with the BMS 4550 on 511b's.



The Altec 416B's have been getting bid up pretty high on ebay lately. I would suggest you look for some 416C's or consider the new modern equivalent from Great Plains Audio, inheritors of the Altec Lansing legacy and some of their machinery and technical talent. They have crossovers too.


I would consider the GPA drivers for the 19 clones. There has been some discussion on how close the 416C's and 416Z's are to the B's other than differences in frame dimensions. Are they pretty close?

Jorg

[89-300ce]

Hi Dave,

A while back (9 yrs) I sold a pair of mint 515's for $500 each to a local audio club member. Supply and demand I guess.

I was looking at Great Plains this afternoon. Their new 604 looks nice.

I guess it depends on whether he wants Altec legacy or a moden day technical similar component. I mean B & C make some nice woofers that would work equally well.

Ian

The B & C 15NDL76 ?

Jorg

[speakerdave]

. . . . I would consider the GPA drivers for the 19 clones. There has been some discussion on how close the 416C's and 416Z's are to the B's other than differences in frame dimensions. Are they pretty close? . . . .

I think I'm not keeping up with the conversation and just adding confusion. I got rid of my 416's a while ago, so I don't have any information to offer you there.

Good luck with the project.

David

[Ian Mackenzie]

Jorg,


You will have to make some saw dust to appreciate the more subtle aspect of the discussion.

Have a read of the Geddes design theories and the JBL improvements to monitor desing pdf over in the reference area

There were some old rules of thumb that a system should extend uniformally at either end of its range.

Again you have to audition a real Altec to appreciate this and study original designs elsewhere. For example using the 2235 (an extended bass driver with moderate sensitivity) in a two way arrangement with extension to say at best to 10-12 khertz is going to sound very biased towards the bass. If you add a super tweeter like they did with the 2405 in the 4333 it will sound more balanced overall but that is now a three way which is not what the 511 or the 811 was ever intented for. The Altec drivers of the day never went up high in the real sense either but in fact this overall blend gave the Altec tone. They were large sytems for more sensitivity and extended to around 40 hz .

If you want lower bass extension use an external sub or a big bass horn or to hold hold the sensitivity up you need to starting enhancing the bottom end with an augmentation like the 4435. But again the 511 and a typical driver is not going to ring out with the high end extension to make it balance to the ear.

Then you may as well look at a 4435 clone which is a vastly superior system in that it does not honk like the Altecs

[4313B]

Yes, there comes a point where you guys have to take this stuff offline and hammer it all out and then maybe bring back the learning experience. It gets real old real fast reading about Zilch and a few others stumbling around trying to figure all this out in real time in the public eye. That's why alot of people have their own nice little homepages. Think about times gone by when people collaborated via snail mail and everyone else didn't have to get involuntarily involved.

Thanks and good luck with your project. :)