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Multi-Way Conventional loudspeakers with crossovers

First attempt at designing a speaker and crossover. I'm sure that I've done it wrong.
First attempt at designing a speaker and crossover. I'm sure that I've done it wrong.
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Old 15th May 2018, 11:37 PM   #41
Tweet is offline Tweet  Australia
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Justin, wall mounting loudspeakers can be problematic, the 'boundary effect' can add up to 9 db of bass boost to frequencies below 100c/s which can acoustically be out of balance unless you design your loudspeaker to take that effect into account. Also, wall resonances and rattles can also add nuisances that distract from the enjoyment of your sound system, generally it is better to step your loudspeakers away from the walls for a better balanced sound.
There are many pitfalls and compromises to a good sound system and one generally learns the hard way, not to worry we have all done it. ....Click the image to open in full size.

C.M
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Old 16th May 2018, 01:35 AM   #42
jplesset is offline jplesset  United States
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Also, looking at your sketch, it looks like your speakers are laid out horizontally. Typically, we stack the drivers vertically, because that gives better horizontal dispersion of your sound...
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Old 16th May 2018, 02:11 AM   #43
horst303 is offline horst303  Australia
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Quote:
Originally Posted by Scottmoose View Post
3rd order filters don't do crazy things to the signal if they're properly designed
There's the rub, for a novice that is not impossible, unless through sheer luck. I guess if you want to be a gun filter designer then knock yourself out, but my experience has been that 1st order even with its substantial compromises sound more pleasing than wacking 6+ components in the signal chain which can sound like a fog over the music, sure somtimes 1st order will just not work, but to me thats a sign that the drivers are not compatible, and then going higher order may not make things better anyway.
And I'm not saying 1st order or nothing, just that its not that easy, as will all those people who have abandoned passive crossovers and went active or full range, will attest.
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Old 16th May 2018, 12:07 PM   #44
TMM is offline TMM  Australia
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Your first crossover attempt looked really good to me. I would not say that it had an excessive number of components or needed simplifying. I only bother eliminating components from a crossover when they are excessively large values which result in large and/or expensive components. All your values were quite reasonable IMO.

As others have said, all it really needed is the tweeter bumped up a couple dB. The resistors don't need to handle the amount of power seen in the sim which assumes full power regardless of frequency. In an actual passage of music there is not much power in the higher frequencies. A 5Watt resistor in the tweeter section should be plenty.

I would stick with around a 2kHz crossover for the tweeter. An XT25 should handle that fine with a 4th order slope. A 2nd order slope @ 2kHz is too aggressive for the XT25 - it'll suffer distortion at loud listening levels.

While dividing the box into individual air spaces for each woofer isn't necessary it does have the advantage that it eliminates long standing waves as now a very tall box becomes two shorter ones. Shorter standing waves are higher in frequency and more easily dealt with by partially filling the box with polyfill etc.

I would generally advise against trying to make a 3-way as your first speaker (even though you do seem to have a pretty good grasp of crossover design from what I can see). I would recommend buying a measurement mic and building a 2-way at first to confirm that what you have simmed matches reality, especially with regards to phase alignment. Once you have accomplished this you are ready for 3-way imo. An XT25 and many of the woofers discussed here (Dayton RS, SB Acoustics) would be suitable for both 2-way and 3-way so you could build it as a 2-way first, then modify it into a 3-way later.

Quote:
Originally Posted by horst303 View Post
3rd order crossovers use a lot of components that can do crazy things to the signal, as a sanity check get a cap and coil so you can run the drivers in first order, and compare to that.
Only if you bang some nominal impedance into a filter calculator and don't sim it. It looks to me like the OP is on the right track because the filter Q looks good and the impedance doesn't show any craziness. The XT25 will need to be crossed at 3.5kHz or something excessively high to handle a 1st order electrical filter and that will totally destroy the polar response of the system, especially since the OP wants to make an MTM.

Last edited by TMM; 16th May 2018 at 12:15 PM.
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Old 16th May 2018, 10:30 PM   #45
jReave is offline jReave  Canada
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Hey Justin, here's a follow-up to my post #38 taking a closer look at some driver combinations and the xo costs. I'll respond to other stuff later.

Option 1: ~ $550

1 x SB 26STCN
2 x Peerless HDS 4" 830992
1 x Peerless HDS 8" Nomex 830869

The sims below immediately showed me 3 things. First that the drivers were indeed amenable to a fairly simplistic 3-way xo (2nd order on the woofer and mid, 3rd order on the tweeter). 2nd that you gain a little bit of sensitivity on the woofer due to the interaction of the main coil and the impedance peak and 3rd, that you lose a little bit of SPL on the tweeter due to the cap values such that it only just meets the SPL target. Personally I would prefer to have a little cushion on both the mid and the tweeter in order to raise their level, just in case. However, given that these are for use with an AVR, you can actually get the receiver to make those eq adjustments for you. I didn't check out all the details of that Pioneer, but it does look pretty capable. Up to you really.

Things to note: xo points are about 400Hz and 2300Hz and phase is tracking very well as shown by the reverse nulls. Sensitivity ends up at about 92dB and impedance minimum is typical for a 4ohm speaker, about 3ohm which is fine for your amp. 13 xo parts in total which isn't too bad, especially when 4 of them are cheap resistors.

Driver costs =~ $325 (but that's dependent on no extra hidden costs when ordering from Solen)
Xo costs =~ $220 using the lowest priced decent quality components mostly from PE. I made 1 concession to cost savings by going with a much cheaper non-polarized electrolytic for the larger cap value in the woofer filter. (Values are just a ballpark btw and will be at least a little different probably with real world measurements. The basic topology should be the same though.)
Attached Images
File Type: jpg 3-way xo.jpg (21.0 KB, 66 views)
File Type: jpg 3-way FR.jpg (117.7 KB, 67 views)
File Type: jpg 3-way Z.jpg (89.2 KB, 65 views)
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Old 16th May 2018, 10:42 PM   #46
jReave is offline jReave  Canada
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Option 2: ~$620

1 x SB 29RDCN $57
2 x Peerless HDS 4" 830992
1 x Peerless HDS 8" Nomex 830869

Same design as before but this time with a tweeter that has a sensitivity of 94dB. (A lower resonance frequency too and very nice low distortion but it is $24 more than the 1st one.) Now it needs a some series resistance and so you now have a little room to play with both the mid and tweeter levels if desired. I prefer that there are options available especially when I am making recommendations for other people.

Driver costs =~ 400
Xo costs =~ 220

Everything else stays pretty much the same.
Attached Images
File Type: jpg 3-way xo.jpg (21.8 KB, 62 views)
File Type: jpg 3-way FR.jpg (118.9 KB, 20 views)
File Type: jpg 3-way Z.jpg (88.6 KB, 17 views)
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Old 16th May 2018, 11:17 PM   #47
jReave is offline jReave  Canada
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Option #3: ~$475 MTM

1 x SB 29RDCN $57
2 x SB 15NAC $46 Cnd ( yikes, only 13 left in stock!)

Talk about an easy xo - only 5 components in total. That's what happens when you start with good drivers. Xo is at about 1800Hz, any cone breakup is well below the fundamental, the reverse null looks excellent again and impedance is again about 4ohm nominal. Sensitivity is pretty much the same as the 3-ways, 92dB 2.83V at 1m.

Driver costs =~ $385 (again with the Solen caveat)
Xo costs =~ 90

I kind of think this speaker is going to sound very good. Max SPL is right up there with the 3-way at about 110dB at 1m again with the use of the AVR's 60Hz or 80Hz HP filter. If you are wondering about the quality of these drivers, look closely at these speakers by Revel, drivers are just in a different color (ok maybe they have been modified a little too, I'm not sure but you may be surprised how many speaker manufacturers just use off the shelf drivers the same as we do). I can't really say which I theoretically prefer (not having heard them of course), the 2-way or the 3-way, so I won't.

These are just some suggestions anyways - other driver combinations are still possible. Either 3-way might just be a little cheaper as just a TMW with perhaps a single RS150-4 as the mid, or ....

Again, let me know if you have any questions.
Attached Images
File Type: jpg 2-way xo.jpg (16.1 KB, 15 views)
File Type: jpg 2-way FR.jpg (105.8 KB, 18 views)
File Type: jpg 2-way Z.jpg (89.9 KB, 16 views)
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Old 17th May 2018, 03:34 AM   #48
JustinRT is offline JustinRT  United States
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I only priced the crossover components at Parts Express (using the closest spec component when the exact wasn't available), so I'm guessing that I could get the cost down if I shopped around; however, with that caveat, here's what options #2 & #3 will cost in total:

Option #2:

6 x Peerless 830992 and 3 x Peerless 830869 from Solen -- $292 shipped (It looks like the import duty is just 4.9%, so that's negligible.)
3 x SB29RDCN from Madisound -- $172 free shipping
Crossover components from Parts Express -- $389 free shipping

Total cost for 3 speakers: $853

I can save about $55 by going with the non-polarized electrolytic capacitors in the woofer filter, but it's still quite a bit more than I planned to spend.

Option #3:

6 x SB15NAC30-8 from Solen -- $283 shipped
3 x SB29RDCN from Madisound -- $172 free shipping
Crossover components from Parts Express -- $129 free shipping

Total cost for 3 speakers: $584

I can probably convince myself to spend the ~$100 more than I originally planned and go with this design. The one thing that I'm not a huge fan of is the silver cone on the SB woofer; since they will be behind an acoustically transparent screen, I worry about light reflections. I wish that the black cone version were on sale. I'll just have to make a speaker grill, I guess.

With only 13 of the SB15NAC30-8 in stock, I'm going to have to decide by tomorrow if this is the route that I'm going to take.

I forgot to thank you earlier for the white paper that you posted; that's going to help me immensely when I'm ready to take measurements.

Speaking of... Since these speakers will be in a baffle wall, do I need to wait until the wall is built and measure them in place, or can I set them up in my garage and take the measurements as soon as they're built? (It could be awhile -- possibly as long as six months or so -- before the room gets remodeled.)

I can't tell you how much I appreciate the help you are giving me; It's so much more than I could have hoped for.
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Old 17th May 2018, 03:43 AM   #49
JustinRT is offline JustinRT  United States
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Quote:
Originally Posted by Tweet View Post
Justin, wall mounting loudspeakers can be problematic, the 'boundary effect' can add up to 9 db of bass boost to frequencies below 100c/s which can acoustically be out of balance unless you design your loudspeaker to take that effect into account. Also, wall resonances and rattles can also add nuisances that distract from the enjoyment of your sound system, generally it is better to step your loudspeakers away from the walls for a better balanced sound.
There are many pitfalls and compromises to a good sound system and one generally learns the hard way, not to worry we have all done it. ....Click the image to open in full size.

C.M
Unfortunately, I don't have a choice but to wall mount the speakers; they are going behind an acoustically transparent projection screen.

Quote:
Originally Posted by jplesset View Post
Also, looking at your sketch, it looks like your speakers are laid out horizontally. Typically, we stack the drivers vertically, because that gives better horizontal dispersion of your sound...
Perhaps it just looks that way because of the angle that I had the view when taking the screenshots, but all the drivers have been aligned vertically in my designs.
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Old 17th May 2018, 04:31 PM   #50
jReave is offline jReave  Canada
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Ok, so it looks like shipping costs from Solen are about the same as the exchange rate savings, which means that the drivers are only a good deal if they are on sale. Not as good a deal as before but still a deal. I had to go back and look at the shipping costs from past PE orders from the States just to double check and about $60 for a decently heavy load looks about right for international shipping.

It looks like you have priced slightly better quality xo components than I did. There are certain places in the filters for savings like iron core inductors for large values and NPE's for very large caps in a woofer's parallel leg for eg. If you happen to order from Solen, I've found their resistors and their Silver Metalized Polyester Caps for large values in parallel legs can save you some money.

But even with some cheaper xo parts, it does look like the 3-way options will be outside your budget. Bummer. But I guess it makes the MTM option the obvious choice.

Having said that, I was thinking about the MTM xo last night and I think I may have done it too fast. I'm worried that I may have asked too much from the tweeter at max SPL. I'm thinking I need to move the tweeter xo a little higher or use a steeper acoustic rolloff or perhaps both. Either will take a few more components (4 more I think) than my 1st sim. So, a little bit more money again. Sorry about that. I have to give it a closer look but I won't be able to do that until later this evening. I'll get back to you.

Cheers
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