DIY Speakers for the Room of size: - Page 2

Something about that MTM setup you missed? I'm surprised you didn't raise the issue of the woofer-mid, it's actually potentially more troublesome.

ah... mtm. So, in addition to the horizontal off-axis issues of a 4" mid crossed at 5600, we've introduced massive vertical lobing due to center to center spacing of the mids being considerably longer than the wavelength of the crossover point, (unless somehow you've managed the neat trick of placing 2 4" drivers less than 2 1/2 inches apart center to center with a tweeter in the middle )

Regretfully, I'm not aware of the woofer-mid issue that you speak of... what am I missing?

I think Mayhem posted the link to all the plans for those drivers....

http://zaphaudio.com/BAMTM.html


Btw, have you heard MTMs before? Mid range above and below tweeter, Some people have issues with them. I do not at all and a good design is a good design!

for inductors, make sure you match the DCR as closely as possible (resistance). So whichever part has .47 ohms or close to it, that's what you are looking for.


my mistake - that is an air core... http://www.madisound.com/catalog/pro...roducts_id=985


http://www.madisound.com/catalog/pro...roducts_id=120
is the cap

uf and MFD are interchangable

the 18ga .30mH Jantzen is a closer match, .26 ohm vs .36 for the 20 ga since the original calls for .2 ohms.

probably splitting hairs at that point, but still...

No, you don't get to assume that. You're asserting it, so now you need to prove your assertion. Let me help you out, now, what is the radiating diameter of a 4" driver of this sort. That, of course, for starters.

It's quite interesting to watch the intellectual games you try to play here. First you presume that the size of the 4" speaker radiating area is 4", and then here you play with the idea that the 4" speaker is a point source.

One reading your words is forced to assume that you use whatever kind of assumption you need in order to justify your ill-considered objections, I guess.

Hint: The drivers are not point sources.

And, no, you may not assume lobing. You were objecting to the idea of a crossover a while ago, remember? Did you forget the effects that has in terms of radiating pattern and lobing?

Is there some reason you forgot the contributions of the thing you objected to first? Is it possible you're leaving a few minor technical details out?

Finally, let's consider what really happens at the crossover point, shall we? We have two radiators about 2.75" in diameter, spaced about 1.6" from a vertically oriented line source in the tweeter.

Oh, hey, you forgot, that looks a lot more like a line radiator even with some delay to the outer elements! Holy cow, it reads almost like somebody designed it that way. Could you ever IMAGINE? :gasp:

Whoops, I guess you missed that part.

Quite a bit, I guess. What do you think the effective radiating area and position of the 10" woofer is at 600Hz?

Finally, for extra credit, what do you think the horizontal pattern of this thing looks like above 300Hz?

I must point out that some of the biggest problems arise from first floor and first ceiling reflections, and MTM, and to a greater extent WMTMW configurations do a splendid job of avoiding them.

If you have a low ceiling, for instance, this is key to good sounding speakers.

There are some caveats, you must be careful to know what phase response you're going to get with your crossover and drivers (i.e. measure it, and then design your front panel, for instance), and go to some effort to integrate it with the crossover and allover design of the front panel.

My opinion is that they are very much better when they are designed carefully, at least for home use. With the right drivers and right design you can get a nice, tight vertical pattern quite deliberately, but have a very wide horizontal patter, such that, for instance, you can aim one speaker "toed in" to face the listener, the other "toed out" to be pointing 30 degrees away from the listener, and still get a nice solid center image on a mono signal.

Such is, in fact, a fairly critical test, and one that perhaps some of the other individuals in this thread ought to consider trying. :0

You're right - could be a magic driver where the laws of physics don't apply. Or it could be the huge peaks in the upper frequency range that you're not taming helping the off axis. In any case, you can look at off axis measurements of people who use this driver in a full range system and see that its about 12db down at 6000 from its level at 1000.



Intellectual games? Ah, here's the scientist trying to intimidate the layman... sorry, I'm just stating basic speaker building ideas. If we go by what the creator of the mtm configurations suggests, the CENTER to CENTER spacing of adjacent drivers should be kept close to one wavelength of the crossover frequency. I don't really care that you think your driver is 2.75" in diameter, every other w4-1337 out there is 4 15/16". So you're going to tell me your mtm with a crossover of 5600 does not have any vertical lobing? Guess you're powering that with FM (not frequency modulation)

And you think I objected to a crossover? Really? Uh... no...



A line radiator? Really? Ok then. Sounds like you're getting awful defensive about your speaker there doc...

You can build something like the HT3 for $2,000 with the AudioPulse 10", Seas W18EX, and Aurum Cantus G2. The AudioPulse woofer has low sensitivity and really needs a large amp to drive it. With the equipment you have I would consider the higher sensitivity Seas 10" sub driver. That would lower your cost a few hundred and give you a speaker as good or better than the HT3 for about $1725. These prices are based on what we would charge for a kit.

Since you haven't been able to answer a single question, or deal with the simplest parts of array mechanics, I really don't see any reason to continue this discussion. Your concurrent insistance on both an area radiator and a point source, simultaneously, for the midrange driver, by itself, is enough to show the error of your ways.

Ave atque vale.

JJ

I don't claim to know everything about speaker design. This isn't a job for me, hell it's not even a hobby. When you come here touting a 3 way speaker with an off-the-shelf unmodified Dayton crossover, with points far higher than conventional wisdom suggests, your logic needs to be questioned, irregardless of how impressive your signature may be. I've no doubt you're an intelligent man, but I don't think you are a speaker designer. I'm just passing on knowledge that I've gleaned from the experts and from the people who actually design speakers; ones whose designs can be backed up with measurements.
My understanding of a line radiator is of multiple adjacent drivers covering the same frequency range. I guess your definition varies. Well, I'm certainly open to new ideas, so how exactly does that work?
You've lost me on Your concurrent insistance on both an area radiator and a point source, simultaneously, for the midrange driver, can you explain that without being condescending?
And to answer your question regarding the 10 driver radiating area at 600hz I have no idea. 4pi to 2pi transition?

For the pair, crossovers and everything?

Can you post pictures, cut list, box schematics, and the appropriate plots (on and off axis)?

Very nice choice!!

Do not worry about the matching sub, there really is no such thing as "matching"

You want your sub to be the best it can be for a specific $$$ range.

Right now two designs/products are HOT!

Mal-x/EP2500 in a sealed box (maybe 2 but thats over 1K).

-or-

AV15H and 2 PRs in a 2 cuft box

Several threads exist with reasons why these are the current HOT list.

jyqureshi - Check out the rythmik 15" servo subwoofer. Or even a pair of 12" from GR-research.
And good choice on the statements! They are not too expensive, and are supposed to sound very very good. And statements go extremely low! You might actually get away from having to build subwoofer(s)!

Getting past the "rough " posts there... Ouch.
The Usher 8945 is on sale and quite respected, the 8945P is the one I was referring to. Half the price of the SS and almost as good.

MTM is not just two mids and a tweet, this usually refers to the very precise design as presented (developed I think) by Joe D'Appolito where very careful third order crossover and dimensions address the various off-center lobeing effects and it has a somewhat reduced vertical dispersion with the advantages JJ speaks of. On it's side, it uses that advantage for a narrow focused center stage. See ASE journal.
Pay attention to JJ's note that it is a careful SYSTEM of drivers, mechanical design, and the crossover. There could be some sweet spot combination that works much better than the picture would imply. That is why it is called "engineering".

Also note that it's a purely far-field system. You neither measure nor listen 3 feet from the speaker, or you WILL get surprises.

In my case, I used a 2nd order crossover that I could buy, rather than spend a lot of time trying to find inductor and capacitor values that are unlikely to find (in terms of precision and non-standard value), and then did the final work with the driver spacing. I miss the old impedence meter I used to have, I could use it to make coils of any value, and also test caps to get what I needed out of a boxful. I can't even seem to find such tools any more.

To answer someone else's questions, I can give out the information I have to people privately, on a onesie or twosie basis, but I probably can't just publish the plans. I don't even have a cut list, at this point I don't get to do my own woodwork, I just hand the minimal information to a cabinetmaker, and cabinets happen. Sorta sad, but I haven't the time or the space to set up my cabinetry shop here... (I wish I did, there are at least 5 other things that desparately need built in the same line...)

Just rebuilt my lab from e-bay. Pennies on the dollar. BK LCR is good enough, but I did see some old Diga-bridges out there. Still more than I can afford! Bets the heck out of my old way (Heath generator, vtvm and a .1% resistor) I did when I got into the hobby 40 years ago. RealTRA for $99, gad, that would have cost $70,000 from HP back then!

Bother, I have to go to EBAY?

I guess I should... Some of this stuff seems like it's going to be impossible to get in another few years.

I recall the wierd, ugly impedence meter we used at BTL a while ago. 4-terminal, so you could measure down into the milliohms very nicely. It would just "do the right thing" and give you the best second-order parallel solution it could muster. (for coils) Series for caps. It would get kinda confused for complex networks, it wasn't intended to do that. It made cool sounds when hooked up to a speaker driver...

It was wierd, it was ugly, it was slow. It worked. Can't even remember the name, it was made by some company on Long Island that's been out of business for 15 years now.

Worth the bother. HP 209S for $15, Tek 100 M delayed sweep for $70. I get a lot of satisfaction by twitteling knobs after being a bureaucrat all day. Audio is easier on the back than the old British cars I have been doing. Cheaper too.
The bridge we used was by GenRad I think.

Heh, and you don't have to deal with positive grounds, and Lucas, Prince of Darkness, either, nor slide-slide carburetters....

But here, at least, you have to deal with below-freezing temperatures when you need the MDF up above 50 degrees so you can glue in the ports...

Grumble. It's March, its is supposed to be balmy here.

Never sacrifice bass by assuming any main speakers does bass justice

Let the proper peice of equipment handle bass properly, IE....all rooms need a subwoofer because placement is curcial and placement is not always tied to where the main speaker is.