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Multi-Way Conventional loudspeakers with crossovers

Mini towers for home theater & crossover phasing
Mini towers for home theater & crossover phasing
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Old 14th August 2019, 02:22 AM   #1
BIGlep is offline BIGlep
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Default Mini towers for home theater & crossover phasing

Hello, I am moving into a relatively small apartment and have decided that my 12" Econowaves that I love are just a bit ridiculous. I was thinking of building a pair of floor standing, or wall mountable speakers that could be used for 80hz+.

Does anybody have any recommendation on 3 - 4" drivers that can be crossed over around 80 hz on the low end when used in a sealed enclosure, and have a fairly smooth high end up to between 3 to 5 kHz.

Drivers I have seen so far
-Dayton ND105
-Dayton ND91
-Aurasound NS3-193-8A
-HiVi M4N

Also, what would people recommend for a system -3db point if I want to cross around 80hz. I'm thinking if I design for Q=.707 and then use another 2nd order highpass of the same Q and frequency you end up with an effective LR4 response, but that's pretty high order for HiFi and I am worried about the reduction in punch that would result from that after reading Tom Danley's notes on his experimentation with linear phase crossovers.

Thanks ahead of time
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Old 14th August 2019, 07:21 PM   #2
system7 is offline system7  United Kingdom
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I don't know quite where we are going on this, or what your technical level is, but decent 4" speaker tend to be 4th order reflex boxes to get any reasonable bass performance. Of course you can use a subwoofer to help out smallish speakers.

At the cheapish end, the Overnight Sensations by Paul Carmody:
Overnight Sensations - undefinition

At the higher end, Eekel's Minis by Troels Gravesen:
Eekels' Mini

Some interesting recent thoughts on the near-perfect mid, which relate to Eeekel's Minis and the W12CY003, because Troels had to work quite hard with it to get it tonally neutral:
W12CY003

The fact is that a 4" midbass won't go very loud without distortion creeping in at high displacement. Nor will the bass be deep. But in a small room or kitchen or bedroom, works OK. Anyway, big bass is usually a bit of a boomy disaster in a small room. But you don't know till you try it.

Hope that helps.
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Old 14th August 2019, 08:39 PM   #3
BIGlep is offline BIGlep
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The plan I have in my head right now is a pair of Dayton ND91-8 MTM speakers, each one having a volume of 2.5L per driver sealed. This gives me a Q of around .66 and a Fs of 90hz, which isn't a bad frequency to cross to a sealed 10" sub. Since a sealed speaker is a 2nd order system I am planning on using a 2nd order butterworth filer, which in series with the woofers natural drop off should mimic a 4th order Linkwitz pretty close, and then I can use another LR4 lowpass on the subwoofer to get phase and amplitude flat response.

Some hornresp modelling shows 2 of the ND91s reaching 103db on 30 watts each while staying within xmax with filtering, which at a listening position of 2 meters should be around 97, or -8db from "reference" for HT. Loud enough for an apartment as far as I can figure.

Since they're going to be up against a wall, and not very deep enclosures I am assuming I won't need very much BSC, maybe 1-2db max.

The ND91s also show pretty smooth response up to around 4-5 khz so a 2nd order crossover to the tweeter at 2-3 kHz should be no problem as far as I can tell.

This is my first time designing a speaker entirely from scratch but I am hoping this is a good foundation to build off of.

Sorry this is long winded but I am trying to make something that I can use for relatively critical listening.

Last edited by BIGlep; 14th August 2019 at 09:00 PM.
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Old 15th August 2019, 02:15 AM   #4
GM is offline GM  United States
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Hmm, small room, but very wide horizontal response, so sitting real close?

GM
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Old 15th August 2019, 04:39 AM   #5
BIGlep is offline BIGlep
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Quote:
Originally Posted by GM View Post
Hmm, small room, but very wide horizontal response, so sitting real close?

GM
Most likely no more than 2-2.5 meters away at a height variable from sitting to standing. The room is pretty wide but not very deep in the orientation of facing the TV.

I'm hoping the horizontal dispersion gets some sound over towards the side of the room where the kitchen is.

I did a sim and with 5mm between the woofers and the tweeter I am looking at (Peerless BC25SC08) and the -3db vertical response at crossover (2500hz) looks to be about 50 degrees (+-25).

I modeled up a Dayton UM10 sealed on 500 watts and it looks like it would make a nice pairing.
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Old 15th August 2019, 08:42 AM   #6
GM is offline GM  United States
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Sounds like you've got it worked out; me, I can't get used to these tiny drivers for use in a room app. I mean I was taught to size drivers by the mean of the power distribution over its intended BW, so your alignment equates to a dual 8" MTM/channel.

GM
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Old 15th August 2019, 03:21 PM   #7
Juhazi is offline Juhazi  Finland
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The topic says minitower... How about making it 3-way, with several 4" drivers as woofers and one as midrange? some of bass drivers could be on the backside.

Right now I don't remember diy-projects like this...
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Old 15th August 2019, 07:38 PM   #8
system7 is offline system7  United Kingdom
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We could go into the whole 3-way thing. Like this:
SEAS-3-Way-Classic

A very fine design. But not for a small room.

This sort of thing ought to do in a more compromised and smaller acoustic environment.:

Click the image to open in full size.
Vifa PL14WJ-

I think small MTM has a lot going for it in the small room.
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Old 15th August 2019, 09:04 PM   #9
BIGlep is offline BIGlep
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Quote:
Originally Posted by system7 View Post
We could go into the whole 3-way thing. Like this:
SEAS-3-Way-Classic

A very fine design. But not for a small room.

This sort of thing ought to do in a more compromised and smaller acoustic environment.:

Click the image to open in full size.
Vifa PL14WJ-

I think small MTM has a lot going for it in the small room.
System7, my main worry right now is how low I need to cross the drivers. I read that it is optimal to have a crossover with a wavelength of about the center to center distance between the two midranges. In my case that is 16cm or 2140 hz.

I'm having a hard time finding tweeters suitable for this low of a crossover. The XT25SC90 looks amazing but I have read that distortion increases below 2500 hz. The Dayton ND25FA doesn't look too bad either but I've read it also likes 2500+ hz. The OC25SC65 also looks good, but I don't know how to go about mounting a faceplate-less tweeter.

Although in the design you linked, the center to center distance is quite a bite larger and they are using a 3200 hz crossover.

Would 2500hz be okay with a LR2 crossover in this type of design with any of these tweeters? Particulatily the XT25 or ND25? They both have very smooth response out to 20 khz.

Any given tweeter will have an Lpad applied to bring the 2.83V sensitivity down to 88 Db, which should tame the resonance peak in impedance, though it needs to keep up to 102 dB 1m of max output.

Last edited by BIGlep; 15th August 2019 at 09:13 PM.
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Old 15th August 2019, 09:08 PM   #10
BIGlep is offline BIGlep
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Quote:
Originally Posted by GM View Post
Sounds like you've got it worked out; me, I can't get used to these tiny drivers for use in a room app. I mean I was taught to size drivers by the mean of the power distribution over its intended BW, so your alignment equates to a dual 8" MTM/channel.

GM
The room is quite small and it would be irresponsible to play music or movies in the apartment at reference (105db per channel). I believe the modeled 98 I can get from this should be plenty, and they can be re purposed as bedroom listening speakers when I get a larger place.
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