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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 12th May 2018, 11:39 PM   #11
JustinRT is offline JustinRT  United States
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Originally Posted by eriksquires View Post
One other thing. The woofers and tweeter are far to wide apart. You do not need to build a separate enclosure for the tweeter.

The two woofers may share an acoustic space so long as the signal to them is identical.

Best,

E
I actually initially had them all in a single space, but then thought that the golden ratio enclosure dimensions that were listed might be important. Putting them all in a single space, should I double the optimum enclosure volume listed for a single woofer, and use two 1" x 4" ports instead of one?

This was my original baffle:

Click the image to open in full size.
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Old 13th May 2018, 01:34 AM   #12
eriksquires is offline eriksquires  United States
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Well, I woudln't leave zero space either. That's hard to route.



You don't have to use 2 ports, but you can. Many prefer the simplicity of using 1 port for both. I use WinISD for this.



Otherwise, pretend they are separate, and use the same port for both.



Best,


Erik
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Old 13th May 2018, 01:46 AM   #13
wintermute is offline wintermute  Australia
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First attempt at designing a speaker and crossover. I'm sure that I've done it wrong.
Another very cheap option (provided you have a sound card with line out and line in) is to make up your own impedance cable as here Cables and use REW to do the impedance measurements. I used to use speaker workshop but found that it's accuracy with some drivers was great and with other drivers was way off. REW seems to be consistent regardless of driver.

Some people find that they need a bigger reference resistor (I'm using 10 ohms without problem, but I often see 100 ohms recommended, I guess it depends a bit on the sound card).

Tony.
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Last edited by wintermute; 13th May 2018 at 01:47 AM. Reason: comment on speaker workshop
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Old 13th May 2018, 04:10 PM   #14
jReave is offline jReave  Canada
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Yes, if you intend to keep building speakers as a hobby, then investing in a good measurement mic and something like DATS is the way to go. But if these speakers are likely to be a one-off kind of thing, building an impedance measuring jig and just using the measurement mic that comes with most AVR's these days along with REW and your computer's sound card can work just fine.

Keeping in the same money range as the DS135, I think you can do better for your midwoofer.

Dayton RS100-8 - $28
SB 12NRXF25-4 - $29 (on sale @ almost 50%) Run these in series.
Silverflute W14RC25-8 -$21 (spec sheet here)

Ported in small boxes, all 3 give you LF responses well below 80Hz and good high SPL for home theater, especially mounted in-wall without baffle step loss.
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Old 13th May 2018, 05:27 PM   #15
system7 is offline system7  United Kingdom
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I'm surprised that no-one has remarked on your low crossover point on that Vifa XT25-60 tweeter. Usually you go a lot higher, say 3kHz, with ring radiators:
Vifa PL14WJ-

I notice you started with near textbook values here, which is OK with wallmounting, since there is no bafflestep. 2-Way Crossover Calculator / Designer

But those sort of calculators usually need flattish drivers and impedance correction to work. Impedance correction is easy enough to estimate from the driver impedance curve. I usually just look at the impedance at 10 kHz and the DCR resistance. MTM is a good way to do home cinema, IMO. Avoids all that unnecessary loudness.
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Old 13th May 2018, 05:28 PM   #16
JustinRT is offline JustinRT  United States
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Originally Posted by wintermute View Post
Another very cheap option (provided you have a sound card with line out and line in) is to make up your own impedance cable as here Cables and use REW to do the impedance measurements. I used to use speaker workshop but found that it's accuracy with some drivers was great and with other drivers was way off. REW seems to be consistent regardless of driver.

Some people find that they need a bigger reference resistor (I'm using 10 ohms without problem, but I often see 100 ohms recommended, I guess it depends a bit on the sound card).

Tony.
Thank you so much for this info. I'm sure DATS or something similar is invaluable for those who build many speakers (and know what they're doing); however, I think that it's probably more than I need at this time.

I do have a sound card, and it looks like an easy cable to make. Is there a specific type of resistor that works best?
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Old 13th May 2018, 05:40 PM   #17
JustinRT is offline JustinRT  United States
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Originally Posted by jReave View Post
Yes, if you intend to keep building speakers as a hobby, then investing in a good measurement mic and something like DATS is the way to go. But if these speakers are likely to be a one-off kind of thing, building an impedance measuring jig and just using the measurement mic that comes with most AVR's these days along with REW and your computer's sound card can work just fine.

Keeping in the same money range as the DS135, I think you can do better for your midwoofer.

Dayton RS100-8 - $28
SB 12NRXF25-4 - $29 (on sale @ almost 50%) Run these in series.
Silverflute W14RC25-8 -$21 (spec sheet here)

Ported in small boxes, all 3 give you LF responses well below 80Hz and good high SPL for home theater, especially mounted in-wall without baffle step loss.
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".
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Old 13th May 2018, 05:52 PM   #18
JustinRT is offline JustinRT  United States
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Originally Posted by system7 View Post
I'm surprised that no-one has remarked on your low crossover point on that Vifa XT25-60 tweeter. Usually you go a lot higher, say 3kHz, with ring radiators:
Vifa PL14WJ-

I notice you started with near textbook values here, which is OK with wallmounting, since there is no bafflestep. 2-Way Crossover Calculator / Designer

But those sort of calculators usually need flattish drivers and impedance correction to work. Impedance correction is easy enough to estimate from the driver impedance curve. I usually just look at the impedance at 10 kHz and the DCR resistance. MTM is a good way to do home cinema, IMO. Avoids all that unnecessary loudness.
My plan now is to measure the frequency response of the drivers in my room, and design the crossover from there.

Thanks for the warning that my crossover point was too low for the tweeter I chose; I had no idea. I'll definitely make sure to set a higher crossover point.
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Old 13th May 2018, 08:23 PM   #19
system7 is offline system7  United Kingdom
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I've heard a couple of wallmounted MTM + Subwoofer setups, and liked them. Never built one, but how hard can it be?

I ran this Visaton Couplet Light projekte file up the flagpole in Boxsim (Visaton Downloads): Couplet Light – Boxsim Projektdatenbank

Not much margin on tweeter output level (here a 91dB unit) with two 86dB 5" woofers and no bafflestep. Impedance is predictably low. But 3.5kHz crossover looked OK with a butterworth 90 degree phase.

If it was me, I'd use two 4 ohm 5" low-inductance (like SB Acoustics) woofers in series in a common enclosure, and I think it would all be easier. Most woofers are really designed for boxes and bafflestep.

Concept results below. I used 15L closed box per driver, because the W130S happens to be made that way with a highish Qts near 0.5. A reflex would dig an octave deeper, of course.
Attached Images
File Type: png JustinRT Concept Circuit.PNG (8.1 KB, 121 views)
File Type: png JustinRT Concept FR.PNG (26.6 KB, 123 views)
File Type: png JustinRT Concept Phase.PNG (28.9 KB, 124 views)
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Old 13th May 2018, 09:27 PM   #20
wintermute is offline wintermute  Australia
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First attempt at designing a speaker and crossover. I'm sure that I've done it wrong.
Quote:
Originally Posted by JustinRT View Post
I do have a sound card, and it looks like an easy cable to make. Is there a specific type of resistor that works best?
I think that in the Walin Jig II that I made uses a 20W type. Though it is also used for other types of measurements. At the low levels that you are doing impedance measurements at I think that you should be able to use a normal metal film resistor, maybe a 2W to be on the safe side.

regards,

Tony.
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