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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 13th May 2018, 10:16 PM   #21
jReave is offline jReave  Canada
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Quote:
Originally Posted by JustinRT View Post
Thanks for the suggestions. Would there be any drawbacks to going with a slightly larger midwoofer? I was looking at the Dayton Audio RS150-4 6".
Yup, the RS150-8 looks like it would work fine. About 20L ported for a pair of them. Only drawback I can see is that a larger driver may be deeper in depth - 73.5mm for the RS150.
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Old 14th May 2018, 04:43 PM   #22
jReave is offline jReave  Canada
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Another occasion where I have to correct myself.

By going in-wall, you don't lose 6dB to baffle step loss, and when you put two 8ohm drivers in parallel, you gain 6dB in sensitivity, so with one RS150-8 at almost 89dB in sensitivity, 2 of them in parallel are going to give you about 95dB, which your tweeter selection (which is a good one by the way) won't be able to keep up with.

If you run two 4ohm drivers in series, there is no net gain in sensitivity. So you should be looking for 8ohm drivers with a max sensitivity of about 86dB or 4ohm drivers with a max of 92dB. In this case, the RS150-4 will work for you.

I have 2 more thoughts though. For home theater and better blending with a sub, the more gradual, 2nd order rolloff that you get with a sealed design for L/C/R generally does a better job. Sealed gives you better transients too. Plus you don't have to mess around with port tuning. And if you are trying to stay close to the cabinet dimensions you used in your 1st post, it looks like a Vb of 10L might be a better goal to shoot for. Or not - maybe you have some flexibility there, I'm not sure.

Given all of that, here's what I would go with:

SB 15NAC30-8

Sensitivity = 85.5dB
F3 = 79Hz in 8L sealed and heavily stuffed with Q=.692, perfect for handing off to a sub.
$46 (Cnd on sale at 50% off)

Here's a build with the driver's bigger 6.5" brother just to give you some idea of the quality of these drivers - SBAcoustics-61-NAC

The 1 negative (is it?) - you have to order from Canada, but unlike when I order from the States, I don't believe there's any extra tax or duties for you to pay (I could be wrong there - maybe someone in the States can confirm that?). And you do get the advantage of the low Canadian dollar.
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Old 14th May 2018, 05:28 PM   #23
JustinRT is offline JustinRT  United States
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Regarding cabinet dimensions: I think I can probably get away with an internal depth of 6", a width of 13", and they can be as tall as I need them to be.

It's a complete departure from my initial design (which I'm not at all married to), but what are your thoughts on going with:

Dayton Audio RS225-4
B&C DE10-8
SEOS-8 Waveguide

(I've read that the Denovo DNA-205 is a clone of the B&C DE10 -- and I'm assuming it's cheaper -- but I can't find it for sale anywhere other than in kits.)

I would use a single RS225 in a sealed enclosure. The tweeter is far more sensitive than the woofer, but am I correct in thinking that I can just attenuate it?
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Old 14th May 2018, 06:42 PM   #24
jReave is offline jReave  Canada
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An 8" + 1" can work but you need a tweeter that can cross over pretty low, like below 2kHz, which this one doesn't look like it can do comfortably. It could work with the right tweeter or make it a 3-way and add in a mid that can be crossed higher.

Also yes, the tweeter would just need to be padded down but that's a whole lot of dB that needs to disappear, like about 16dB. I'd try to go for a different tweeter that matches SPL a little better.
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Old 14th May 2018, 07:23 PM   #25
montana1 is online now montana1  United States
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Hi JustinRT,
I agree that an 8" + 1" can be a very nice performer. Other then jReave's point on tweeter selection another consideration is the severity of the woofer breakup. In the case of Dayton RS225-4, it is quite severe. IMHO, a better woofer choice for a 2way like this would be Peerless 830869 Nomex cone or one of the Sb Acoustics offerings like the SB23NRX45-4. I can speak to the Peerless 830869. I'm using it in a two way crossed at 1.7K to a waveguide loaded tweeter and say it is a sweet woofer! Matter of fact, I like it so much that I'm going to order (2) more from Solen Canada and build a 2.5 way using these Peerless woofers wired in parallel.

Best Regards,
Rich
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Old 14th May 2018, 08:35 PM   #26
JustinRT is offline JustinRT  United States
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Hey Rich,
Thanks for the recommendations; those Peerless woofers look interesting, and look to currently be on sale at Solen.

jReave,
Is the implication that in an MTM configuration, I can set the crossover point higher? Do you think that I would be able to use two of the Peerless 830869 in Parallel (which would give me 96 dB sensitivity) with the B&C compression tweeter? From what I've read in another forum, the Denovo DNA-205 can be crossed over lower than the B&C DE10. I'm going to try to figure out if it's possible to purchase separate from a kit.
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Old 14th May 2018, 11:16 PM   #27
jReave is offline jReave  Canada
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Ok, here's the way I look at home theater speakers:

1 - L/C/R should be as close to the same as possible. (Perfect with what you are doing.)
2 - Perhaps more than anything else (besides the subs) what I want is dialogue clarity. And at least 1 of the ways to get that is by relieving the mid driver from having to pull double duty, of having to also work like crazy on the bass at the same time. So, either limit the satellites to >80Hz or go with a 3-way, the latter in my mind being the better of the 2.

As to the larger woofers, besides looking out for cone breakup as montana mentioned, you also want to watch out for directivity, or the off-axis response. Not recommended is crossing over to the tweeter above the point where the woofer's off-axis response starts to diminish, the strict rule of thumb being cross below the woofer's -3dB point at 45 degrees off-axis.

There is another rule of thumb for driver spacing which says the centers of 2 drivers in an MTM should not be spaced larger than 1/2 the wavelength of the xo frequency. 1/4 wavelength is even better but 1 wavelength is often accepted as a compromise when necessary.

Looking at the Peerless FR below, the -3dB point at 45 degrees looks to be just about exactly where montana put his xo, about 1700Hz . However, the corresponding wavelength is about 8", so unless you can get the centers of those 2 woofers closer than 4", it's a less than ideal setup. Even 8" center to center can't be done when there's a tweeter in between them. So 8" drivers are not generally recommended in MTM configurations.

Also those Peerless don't go any lower (ie. F3) sealed than the 5" SB's do. And they need a fairly large Vb for 2 of them ported, upwards of about 50L. You are going to want to double check if you have enough room for that.

Certainly for yourself but also for those of us trying to aid you, it really helps if you establish a set of goals or criteria or parameters to start off with, otherwise it's easy to just start bouncing around between a whole lot of different choices. Establish things like:
- budget
- maximum box size
- minimum F3, so stand alone for music or always with a sub
- max SPL at what distance
- minimum speaker sensitivity
- alignment: sealed or ported or....
- 2-way, 3-way, MTM, TMW, MTMWW, etc.....
- acceptable minimum impedance
- passive or active
- how much power available into how many ohms
- even where you are willing or not willing to buy from
etc....

Once you get these things sorted out, the task of driver selection and speaker design tends to fall into place a little bit more easily.
Attached Images
File Type: jpg Peerless FR.JPG (61.0 KB, 85 views)
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Old 15th May 2018, 12:28 AM   #28
montana1 is online now montana1  United States
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Hi jReave,
I wanted to run a question by you to get your expert opinion. This may even be a design option for the OP. What do you think about a 2.5 way TWW configuration with upper woofer 25L sealed and lower woofer 58L vented? The woofers would be the Peerless 830869 and tweeter may remain the SS D2604/83300 mounted in Monacor WG300 or maybe look to something else that can be crossed around 1.2k or there about. This build we me strictly for music but I'm convinced that it would do well for HT use as well. I have attached a boxy cad drawing to get an idea of cab size, driver spacing, etc.

Also, have you written any books on loudspeaker design and theories? If so, where might I purchase a copy. I really have learned a lot from your posts.

Best Regards,
Rich
Attached Images
File Type: png peerless2.5way.png (413.3 KB, 80 views)
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Old 15th May 2018, 01:26 AM   #29
horst303 is offline horst303  Australia
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Quote:
Originally Posted by JustinRT View Post
H


The crossover:

I am sure that I am completely out of my league in trying to design a crossover, but I gave it a shot anyway. I'm just going to post a bunch of graphs and hope that you guys can tell the ways that I screwed up (and hopefully how to fix it ).

Schematic:

Click the image to open in full size.
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.
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Old 15th May 2018, 02:40 AM   #30
JustinRT is offline JustinRT  United States
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jReave,

I don't know if the product specs on Parts Express are to be trusted, but for the Peerless 830869 it lists an optimum sealed cabinet volume of 0.57 ft^3, with an F3 of 67 Hz. That size of enclosure (or even twice the size if I'm using 2 woofers) is doable.

I'm not entirely opposed to building a 3-way speaker -- in fact, all things being equal, I'd probably prefer it. The reason that I'm hesitant is because I assume the crossover will be more complex. I don't know that I'll be able to properly design a 3-way crossover, and if it requires significantly more components, I'm worried that cost is going to skyrocket (I'd prefer to use polypropylene capacitors rather than electrolytic). That said, if it's not cost prohibitive, and I feel confident that I won't completely screw up the crossover design, I'd definitely be open to going with a 3-way design.

I had read about the ctc spacing, but either what I read was wrong -- or, more likely, I misunderstood -- as I was under the impression that the measurement that mattered was from the center of the woofer to the center of the tweeter.

To answer your questions:
  • I'd like to keep the cost of all the components (including crossover but excluding enclosure materials) to around $500.
  • Maximum box size: internal depth of 6" (15.25cm), width of 13" (33cm), and they can be as tall as I need them to be.
  • They will always be used with a sub.
  • Seating will be ~15ft (4.5m); I don't have a specific number for max SPL in mind, but it would be nice to be able to get quite loud on occasion. Also the subs they will be paired with are four 18" woofers in an infinite baffle.
  • I'm not sure about minimum sensitivity. They will be used mostly for movies, and as I said, ideally they will be capable of playing loud when needed.
  • I would prefer a sealed enclosure if possible, but have no problem going ported if necessary.
  • If it's within my capabilities and budget, I'd love to go 3-way (TMW, probably), otherwise, I'll have to stick with a 2-way design.
  • The speaker can't be lower than 4 ohms. If an 8 ohm design will meet my criteria, all the better.
  • I will almost certainly be going passive. I'd love to go active, but (correct me if I'm wrong) I believe that would require me to have a separate amp for each channel.
  • The speakers will be driven by an AVR. Currently I have a Pioneer SC-1522-k. The power rating is listed as: 130w per channel @ 8 ohms; however, it says it supports 4 ohm speakers. I will be getting a new AVR eventually, but it will be at least as good as my current AVR.

Unless it's an absolutely horrible idea, I do think I'd like to use the compression tweeter with waveguide. I only have one row of seats, and can toe-in the speakers.

If I go with a 3-way design using a compression tweeter with waveguide, will the Peerless be a good choice as the woofer? What should I be looking for in a midrange to pair with it?

I'm truly grateful for all the help you and everyone else who has replied are giving me.
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