Mini towers for home theater & crossover phasing

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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
 
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. :)
 
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.
 
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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.
 

GM

Member
Joined 2003
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
 
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.:

623059d1498522989-new-3-way-project-vifa-pl14wj-dappolito-mtm.jpg

Vifa PL14WJ-

I think small MTM has a lot going for it in the small room. :)
 
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.:

623059d1498522989-new-3-way-project-vifa-pl14wj-dappolito-mtm.jpg

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.
 
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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

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.
 
Understood and counter intuitively, larger drivers work better in smaller environments due to having increasing directivity to reduce/eliminate early reflections among other things. As for power handling, the 8"ers would barely move in your app Vs the little drivers pumping at much higher distortion.

Regardless, not trying to convert you per se, mainly just using you to further DIYer's education. ;)

GM
 
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.
Sounds like you have a very good technical level. Let's talk mini towers since that is the topic.

Here's one by one of this forum's brighter lights, Mr. Joachim Gerhard:

694495d1533023707t-sonics-joachim-gerhard-cabinets-kits-136c1fa5-67d9-4b60-bf5f-65718b0c03cd-jpg


Sonics by Joachim Gerhard cabinets and kits.

I would imagine that is a TMM rather than a 2.5 way.

My own view is an MTM is really not far different except on lobing. MTM has symetrical lobing, but really I don't think it matters much.

Crossover point is often a matter of taste. Cross low, and the tweeter struggles, cross high and you hear midbass breakup. All made worse by shallow filters. I happen to be in the high order (LR4) crossover and highish 3kHz XO camp, because I like complex and spectrally dense classical music alongside almost any other music you might mention.

Another fine MTM design is by our own learned member, Mr. Lynn Olson:
The Ariel, Part I

There's bags of interesting articles at Lynn's site. An experienced builder. The miracle of MTM or TMM is that it produces the same sound levels at the listening spot, with half the power to the room, which keeps the neighbours happier.

For your small room, this Peerless 830860 looks like the modern equivalent of Lynn's Vifa unit:
Peerless HDS PPB 830860

It's almost trivial on the crossover to convert an MT to a series MTM. Double the coil and resistor values along with the box and vents, and halve the capacitor values in the bass section. The tweeter section is unaffected. It all works out and gives you an amp friendly higher impedance. I call that WIN-WIN!

I am quite interested in this dome mid design by Mr. Troels Gravesen:

SP38/13

I can think of cheaper alternatives to those Scan drivers. It's the idea that counts. You are giving the midbass and tweeter an easier life by letting the dome mid deal with the area where they struggle.

Choice of drivers is all about finding good and flat ones in the first place, since every crossover adjustment tends to worsen impedance, which matters with feedback amps. TBH, I don't like LR2. It's OK for jazz and acoustic music, but plain distorts my favourite Mozart and Debussy and Chopin. There's a reason the low order crossover people always play the lovely jazzy Miss Diana Krall at HiFi demos!
 
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I have always had misgivings about MTM myself, so you could say I agree with you. :D

It's actually a Mr. Joe D'Appolito BW3 solution in reality. But we tend to implement it as LR4.

The real LR4 mathematical solution is MTTM. It looks like this, if you accept that a long ribbon has much the same dispersion as two dome tweeters:

733281d1549059344-speakers-parallel-serial-wagner-net-au-kit-260-5-inch-mtm-jpg


I have to be careful what I say here, but I have heard this sort of cost-no-object system, but I honestly think that given enough money and some serious subwoofering in an acoustically treated room, this is about as good as it gets. :D

Not many people know this, but with every symmetry comes a conservation law. Emmy Noether (the best female Mathematician, ever, respected by no less than David Hilbert and inevitably hated by the Oafs of the Third Reich...) proved that principle. Mostly applied to Quantum Mechanics these days, but works for speakers too. FWIW, we still use the Hilbert Transform to relate frequency response to Phase and Time Delay in speakers. It's how Simulators work.

Myself, I'm a real Socialist. I want good speakers for everyone. Preferably under £200 for the whole lot. I can dream. :eek:
 
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