HELP - Crossover Designing

[jmascreen]

Greetings

I am designing a crossover for my New DIY TQWT with dayton drivers. However I am feeling that the crossover is not that perfect.

I do see a drop from low to high and wants to achieve somewhat near to the yellow line. Can you guys please help me on achieving it.

Drivers
Woofer -DayTon DA175-8
Tweeter - DayTon DC28F-8

Crossover details are - 2nd order Linkwitz-Riley with Lpad for tweeter and Impedance EQ for Woofer.

 

[jmascreen]

72 Views no reply...
Seems my projects is heading as per Murphy's Law

 

[tcpip]

72 Views no reply...
Seems my projects is heading as per Murphy's Law

Your crossover design must start with measured SPL data of the drivers fitted to your enclosure. Where is that data?

 

[kapvin]

72 Views no reply...
Seems my projects is heading as per Murphy's Law

Justin,

first my apologies for not working on the TL model. I have been a bit unwell and we never completed the conversation on whatsapp.

second, as far as the crossover is concerned. any crossover calculator that does not take the impedance curve of the speaker driver into account is not worth it's salt (i.e is actually close to useless). you should measure the impedance of your speakers, but if not possible you can find .zma files on the net for those drivers. I would recommend PCD for crossover design. that's what I use and it is pretty awesome if you have 32bit MS Excel. you also need the measured frequency response of the speakers in the enclosure. if cannot measure, you can model the response using one of many diffraction calculators. (and you can also get the frd files from the internet) Please remember that when doing a crossover design, you will need to look at acoustic slope and not electrical slope. with malice to none, anyone who is not doing all of this while designing speakers is actually either shooting arrows in the dark or has "borrowed" someone else's design.

lastly, while looking at your slopes, i'd think you tried to do BSC as well as the crossover. if so you need to "cool" the tweeter, reducing it's output either with a series resistance before the tweeter crossover elements, or an L-pad.

remember the objective of BSC is to get a flat acoustic response to compensate for the loss of bass due to diffraction.

best wishes.

 

[keith_correa]

I think the Indignia uses the same drivers. Check here for the x-over. Maybe it will help.

 

[jmascreen]

Justin,

first my apologies for not working on the TL model. I have been a bit unwell and we never completed the conversation on whatsapp.

second, as far as the crossover is concerned. any crossover calculator that does not take the impedance curve of the speaker driver into account is not worth it's salt (i.e is actually close to useless). you should measure the impedance of your speakers, but if not possible you can find .zma files on the net for those drivers. I would recommend PCD for crossover design. that's what I use and it is pretty awesome if you have 32bit MS Excel. you also need the measured frequency response of the speakers in the enclosure. if cannot measure, you can model the response using one of many diffraction calculators. (and you can also get the frd files from the internet) Please remember that when doing a crossover design, you will need to look at acoustic slope and not electrical slope. with malice to none, anyone who is not doing all of this while designing speakers is actually either shooting arrows in the dark or has "borrowed" someone else's design.

lastly, while looking at your slopes, i'd think you tried to do BSC as well as the crossover. if so you need to "cool" the tweeter, reducing it's output either with a series resistance before the tweeter crossover elements, or an L-pad.

remember the objective of BSC is to get a flat acoustic response to compensate for the loss of bass due to diffraction.

best wishes.

Thanks Kapil for your reply. I already have the frd & zma files with me also downloaded ARTA to measure the drivers. Currently I made a makeshift enclosure using some unused mdf/particle boards. I have used L-PAD in tweeter as the it has 4db more than woofer also used impedance eq in woofer. Once I reach home I will update the Xover design. I am using Xover pro for designing, also have jeff Baby's crossover design sheet as suggested by MJK. Will try PCD

 

[jmascreen]

I think the Indignia uses the same drivers. Check here for the x-over. Maybe it will help.

Thanks for the info.
I am not sure whether a BS crossover design can be used for FS/TL. because of the baffle difference etc.

 

[kapvin]

PCD is by Jeff Bagby.

If you keep the baffle width, and distance of tweeter and woofer same from the top and sides, (and their relative offsets) you are okay if you increase the length (bottom)

 

[keith_correa]

If you are going to be taking in-box measurements, why are you designing the x-over now? What purpose would it serve? Wouldn't it be better to use the data that you get after you measure to design the circuit?

 

[tcpip]

Thanks Kapil for your reply. I already have the frd & zma files with me also downloaded ARTA to measure the drivers. Currently I made a makeshift enclosure using some unused mdf/particle boards. I have used L-PAD in tweeter as the it has 4db more than woofer also used impedance eq in woofer. Once I reach home I will update the Xover design. I am using Xover pro for designing, also have jeff Baby's crossover design sheet as suggested by MJK. Will try PCD

I am not sure there is anything to be gained by building a makeshift enclosure first. You need T/S parameters to design the enclosure, and T/S parameters can be measured without requiring a makeshift enclosure. Therefore, the sequence which makes sense to me is

• Measure the T/S parameters
• Build a small box if needed, to measure Vas using the delta compliance method. Fit the driver in the box and do the Vas measurement. No need to make this box anything like your final enclosure, and no need to mount any driver other than the DUT.
• Using the T/S parameters, design and model the enclosure
• Build the final enclosure. No need to make a makeshift enclosure anywhere.
• Fit the drivers in the final enclosure.
• Take SPL and impedance measurements of each driver in the final enclosure (free air measurements or "theoretical" measurements, or measurements on IEC baffle, are of much less or no use).
• Use these FRD and ZMA files to design and model the crossover

This is the sequence which makes sense to me. You say you have the FRD and ZMA files, but you haven't made your final enclosure. In that case, how will you use these FRD and ZMA files for crossover design? These FRD and ZMA files are unrelated to the driver behaviour in your final enclosure.

 

[jmascreen]

Yes tcpip I agree with your points. To answer your question why I made makeshift enclosure. I was not sure about the outcome of TL based enclosure as I have never heard one only read about it in this forum. So before investing for enclosure i used the available mdf's with me.

This is the targeted enclosure design

This is the WIP crossover design

As kapvin suggested I will try with PCD and see how it goes. I am targeting to make enclosure on last week of this month as I have a long weekend.

 

[jmascreen]

Also I have the T/S data measurement downloaded from Zaph audio site.

 

[tcpip]

Yes tcpip I agree with your points. To answer your question why I made makeshift enclosure. I was not sure about the outcome of TL based enclosure as I have never heard one only read about it in this forum. So before investing for enclosure i used the available mdf's with me.

Understood. Good idea.

In that case, my other doubt remains: what about real SPL and impedance data, after fitting drivers to enclosure? Without that, you can't design or model your crossover.

 

[jmascreen]

Understood. Good idea.

In that case, my other doubt remains: what about real SPL and impedance data, after fitting drivers to enclosure? Without that, you can't design or model your crossover.

I am under the impression that there will be no major changes to crossover. Please let me know if I am wrong so that I can reset my approach.

Secondly I am going with the tapered enclosure, will there be a major difference in sound signature if I go with the classic TL's?

 

[tcpip]

For Non TL speaker box design,

1. If the Vas is already mentioned by the manufacturer of a particular driver, can one go ahead and calculate box volume for sealed or ported?

Sure, if the manufacturer has a track record of publishing accurate T/S parameters and consistent manufacturing. I would trust published T/S parameters of any of the Peerless-Scanspeak family of drivers, and would always measure HiVi drivers, for instance.

2. What would be the final steps in performance optimization (apart from BSC), in case your crossovers are active (analog in my case) as there would be no caps and inductors to play with?

In this case, varying active crossover frequencies would do the job? Mine are Linkwitz Riley, 24dB/octave.

Can you please explain what you mean by performance optimisation? Do you mean tweaking of the sound after the first auditions?

If yes, I can suggest only the following general rules:

• At the very least, be prepared to play with tweeter level. All good active xo should have pots to adjust each channel's level, therefore this should be very easy to do.
• Beyond this, you may need to play with xo Q (i.e. 0.6 instead of 0.7) and fc (the crossover frequency).
• In rarer cases, you may need to play with slopes. Switch from a 4th order to a 3rd order, etc. However, this is rarely needed as a dire necessity; it may be attempted as a fine optimisation if you want to experiment.

This assumes that you started with measured SPL and phase data to begin with, and modelled your xo based on this data. By "measured" data, I mean fitting the drivers on the final enclosures and then measuring using a mic.

If such measured data is not your starting point, be prepared to experiment with everything, including crossover topology. Even there, I am not sure what you will play with, because you will not be able to correlated what you hear with what changes you need to make to the xo, in the absence of measured data. Even xo designers with a couple decades of experience work with measured data, AFAIK. No (good) designer designs (good) crossovers without measurements. Lynn Olson (of Ariel fame), who is a very talented and experienced designer, and who places huge importance on listening, does careful measurements, for instance.

 

[tcpip]

I am under the impression that there will be no major changes to crossover. Please let me know if I am wrong so that I can reset my approach.

Major changes compared to which starting point?

Let me explain my question. I do not understand how a crossover can be designed without starting with on-enclosure measured data of the drivers. For passive crossovers, you need SPL and impedance, and for active crossovers, you need SPL.

When you talk about no major changes, I don't even understand how the first crossover design is arrived at, let alone changes to it. Hence my doubt.

Secondly I am going with the tapered enclosure, will there be a major difference in sound signature if I go with the classic TL's?

I have very little experience with TL, so I will probably not be the right person to comment.

 

[jmascreen]

Major changes compared to which starting point?

Let me explain my question. I do not understand how a crossover can be designed without starting with on-enclosure measured data of the drivers. For passive crossovers, you need SPL and impedance, and for active crossovers, you need SPL.

When you talk about no major changes, I don't even understand how the first crossover design is arrived at, let alone changes to it. Hence my doubt.

I have very little experience with TL, so I will probably not be the right person to comment.

Driver + Enclosure SPL data from ARTA for woofer, is this correct or I missed something. I am refering to the is this site ARTA

12.416 -0.0389 -159.2883
12.546 -0.0389 -5.3306
12.678 -0.0389 -30.5625
12.811 -0.0389 -118.1621
12.945 -0.0389 -80.3453
13.081 -0.0389 94.5195

 

[jmascreen]

Guys any suggestions for the enclosure design?

 

[tcpip]

Driver + Enclosure SPL data from ARTA for woofer, is this correct or I missed something.

If you have done this, then this is fantastic.

Can you share with us a screenshot from Arta showing the graph of the SPL curve? The curve you shared at the start of your thread was not real at all -- it was some simulated curve with totally smooth shapes. Such unreal curves are of no use. If you have measured SPL, I'd love to see the graph.

And for crossover design, you will need two separate curves, for woofer and tweeter. Also, they must be measured after being fitted on the final enclosure you are going to use. The dimensions of the front baffle, the positions of the drivers on the baffle, and the edge shapes of the baffle all impact the SPL curves.

 

[jmascreen]

HI tcpip,
Here are the screenshots from REW, I was not able to export the frd back to ARTA somewhere in REW i saw that option. SPL view too was not working.

Captured Data

Downloaded frd from Zaph Audio

Why I had doubt with my captured data was that I got negative data in db field wherein if I use the downloaded or convereted data the db was around 50 to 70.

If the captured data is wrong, could you please let me know what I am doing wrong?