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What don't you like about the sound of the new version? Glad to hear you're not discouraged! :T
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That's too bad they didn't work out. I love the look. Properly finished they could have a cool modern art/ scifi thing going on. Maybe a modern art gallery would buy them from you?
So what exactly didn't you like? Do you believe it was the waveguides that caused the problem? Do you think they could be reshaped or have the layout changed? I think there are some good lessons here if you know WHY it failed.Comment
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Hi Joe,Originally posted by joecarrow
Looking forward to it!
I had Paul Kittinger model the Tline. He's done a lot of them and knows what he is doing, so I'm pretty confindent in it. I'll post his graphs when I start the new thread. F3 of 29-30hz and F10 under 20 in a 1.1 ft3 enclosre sounds pretty inviting to me. Actually, here is the modeled TL FR graph, attached.
As I recall, the sealed F3 was in the mid 40's. For a qtc of .7, with a heavily filled box, the size was a little under 16L, in Unobox, IIRC.
Dan N.Comment
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It's interesting. I suspect it is a number of things. It actually sounded great at the Indiana DIY meet and that was with a crossover version that was not very good yet. The bass was deep and strong in that room. When I listen to it by itself, it sounds quite good. However, when I A/B it with one of the Mentor omni's, it just does not compare. The bass seems lacking for one thing. However, the Mentors have build in 12" subs with active crossovers and LT circuits, so they are naturally much stronger here. The thing that bothers me most is the midrange. It is just not as open or real sounding and sometimes sounds more strained, particularly at higher volumes.Originally posted by Paul W
There are so many places to look for the problems. It might be just a bad crossover design, since it's my first 3way. It might be that a larger dia. wave guide and/or larger diffuser would help on the mid would help.
In moving up and down, the sweet spot is definitely on the planned listening axis vertically, so that is not the problem. Moving left to right in the room the sound is remarkably consistant at all positions horizontally. It might be that it is fussier about room and placement.
I think I just need to step back for awhile and pick it back up later this year.Dan N.Comment
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Hi Brandon,Originally posted by augerpro
See my post above on what I don't like about them.
I may be coming off wrong here. I don't really think of it as a failure. It just does not stand up well to the Mentor omni's. For a single speaker playing mono, it held up very well against the other pairs at the Indiana DIY. However, if it's not as good as what I've already created, it's hard to be motivated to build another one and finish them both. This is a pretty time consuming construction. My main goal was to better the first omni, which, so far, I have not done.
It may very well be simply room related. My room is about 15'x19', but bleeds off into a dining room, a kitchen, then foyer and even to the family room upstairs (open two story entry).Dan N.Comment
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I knew when I wrote "failure" that probably wasn't the best choice of words. I meant it relative to your expectations. In more of a Thomas Edison sort of way, ya know?Last edited by augerpro; 12 May 2007, 08:14 Saturday.Comment
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Dan I was looking at some pics you had at another site adn realized the mid and tweeter were both in WGs. Wouldn't this be kind of counter to the idea of the omni? I would think mounting a dome mid and tweeter normally to advantage of their wide dispersion at the lower end of their passband would be desirable in an omni. Then offcourse use those groovy cones to disperse the higher frequencies. I dunno...just a random observation...Comment
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HI Brandon,Originally posted by augerpro
I started my testing with a diffuser only. I'd have to review my notes and post to be sure, but IIRC, I found that the waveguide/diffuser combo tended to do several things that seemed positive at the time. They extended the flatter section of the FR both at low and high end of each driver. It may be that the two parts contributed separately to each end? For example, the WG might boost the low end of a drivers FR, whereas the diffuser might bo0st the high end. They generally flattened out the natural roll off so that the breakup peaks and dips appeared less signficant. They provided almost the same FR on over 360 degrees.
On the other hand, I'm sure the round difffusers introduced some diffraction and is part of why the mearured FR looks like it does.
I think what it is, in effect, is a 360 degree "horn". Perhaps it is horn related issues is what I'm struggling with in the sound?
I'm not following what you suggest in termos of mounting the tweeter and mid. Can you elaborate?Dan N.Comment
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This was a bit of shocker for me. I moved the single waveguide based omni speaker upstairs into the family room. It is about 12'x15' and fully enclosed on 3 sides, with about 1/2 of the third side open to a two story entry and stairs.
I connected it up to my HK AVR320 (recent $125 get at a local Pawn shop!) and played a cd on it. Wow, it sounds great up in that room! :E :T
I may get back to finishing this project for the upstairs sooner than I anticipated. The bass is much stronger, the midrange more relaxed, etc., etc. It sounds fuller, more like it did at the Indiana DIY, without the bass bloat. Interstingly, there is not much furniture in this room as we jsut moved a couch and loveseat out and only the carpeted floor to reduce reflections.
The downstairs is a pretty open play for a total area of about 30' x 30', with partial valuted ceilings and also bleads into the upstairs. Maybe the room was too much for this speaker, or a single one anyway.
I think I will change the name to the ND1 (for "new direction 1") since it is such a departure from the original Mentor design.Dan N.Comment
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Hi Dan. I meant just mount them on the baffle in the standard way, not in waveguides. But still use those diffusers.
I think the kinks can be worked out. It's such a cool (and cool looking) project I'd hate to see you abandon it.Comment
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I have a suspicion that one contriubuter might be that the diffusers are too small, especially the midrange, since it has the longer wavelengths.Originally posted by augerpro
I'm trying to figure out a way to add a couple inches back to the diameter to see what the does to the sound. As we talked before, I might be losing too much sound upward, due to the smaller dia. diffusers.Dan N.Comment
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omni diffuser
Hi all,
I'm interested in omnispeakers like you guys, I actually made a experimental loudspeaker with conical diffuser, but found it upset the frequency response (sounded boxy) - though maybe experimenting with the distance between the speaker and diffuser would overcome that? I was wondering what you guys think..
Here is a pic of my diffuser;
Here is my speaker, the diffuser would sit on top (the drivers are 5" peerless 850488 and PL27tg);
I'm also considering not using the diffuser and instead tilting the speaker forward on a stand so that the two mid woofers are the same angle off axis to the listener.
The use of an eq like the behringer ultra curve pro is an option with or without diffuser.Comment
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Hi,
I'm not sure how your diffuser fits with the speaker you posted, but it is clear that size of the diffuser relative to the driver and distance from the driver can make a huge difference in the frequency response.
IMO, it is impossible to do an omni project unless you have full measurement capability. It is just too hard to figure out what is going on with a diffuser and the FR without being able to take measurements to determine optimum size, placement, etc. Do you have measurement capability?
I have done two other omni project that are posted here you can take a look at if interested. They might give you some other ideas to explore.
https:/www./htguide.com/forum/showth...mnidirectionalDan N.Comment
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Hi Dan,
thank for reply, I do not have measuring capability but I'm interested in getting it, what needs to be purchased to set it up? though I'm a bit niave when it comes to measuring (I have used 'Speaker Workshop' a little). Could I buy say a flat response Behringer Mic and preamp, and some kind of computer software, I currenty have cool edit pro II, don't know if it can be used. I'd want to keep it as simple as possible, and some advice on measuring techniquies would be helpful ie mic placement.
In your opinion do you think the diffuser on my speaker could work? The diffuser sits on the top of the cabinet by three legs, sitting above the upfiring midwoofer on the top of the cabinet. Its abit like the Duevel Jupiter, except I use a front firing tweeter instead of mounting the tweeter on the top half of the diffuser (originally I experimented with the tweeter mounted downfiring above the diffuser).
Heres a pic of how I'm roughly looking at mounting the diffuser above the midwoofer.
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Another option if I don't use the diffuser; I'm thinking about tilting the whole box forward so that the top firing midwoofer and front firing midwoofer are the same angle of axis to the listener. I think their off axis responses would still be adequate, if I cross them over at about 1.8khz @ 24db/oct. The tweeter would be at about ear height.Comment
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For measurements you need a mic like the Behringer ECM8000 and mic-preamp with phantom power supply like the Behringer Xenyx 802, an appropriate sound card and usually an amp of some sort, as well as MLS software. There are some products that combine an external soundcard with a mic-preamp. Speaker Workshop and Arta have free versions available that you can take measurements with. Here is a link to a sticky with measurement software, etc. links:
If you do some searches here on the forum, you should find numerous threads about measurement options. This subject comes up every few weeks.
My project in this thread uses diffusers much like yours. It will work depending on what frequency range you use it for. In other words, it will redirect the sections of the frequency range that has wavelengths that are short enough for it to effect. For example, using it compared to the up firing driver alone will likely extend the upper frequency response a bit before the natural driver roll off and may make the roll off smoother and also effect the level of the cones break up modes. It is very hard to predict exactly what it will do and what height it will be most effective. You will want to test it at various heights in order to determine where you get the best response.
The more significant problem that you have to deal with in your speaker is the horizontal offset between the drivers. The front firing drivers and the up firing driver are at significantly different distances from the listener and the sound from each speaker reaches the listeners ear at different time. This means that you will potentially have serious phase issues between the up firing woofer and the front firing woofer as well as the tweeter. If it was a 3way and the up firing woofer was crossing over under say 500-600hz or less, you may be able to deal with it in the crossover (I'm assuming a passive crossover here). As you go up in frequency the offset distance between these drivers becomes more and more significant. If you are doing an active or digital crossover, you might be able to introduce some delay into the signal to the front two drivers in order to get a phase match with the up firing woofer. You can also do a ladder delay network passively, but I know nothing about them and understand they are complex and costly.
This is why I have generally taken great care with my omni designs to ensure they are time aligned fro the listener to the voice coils of each driver. However, I am contemplating a center channel speaker with two side by side up firing woofers and a front mounted mid and tweeter, though I would try to make the crossover to the mid as low in frequency as is practical.Dan N.Comment
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thanks for info, much appreciated, it might be a great idea for me to make it into a 3 way using a passive crossover between the top mid woofer and front mid woofer. And I'll keep using active crossover between the mids and tweeter.
I suspect that using the diffuser only for lower frequencies as you mentioned under 500-600Hz is likely to work without major probs, would I still need to measure with mic? I think the MBL 111 uses a similar diffused midwoofer?
Do you think there is much to gain from only having frequencies omnidirectional below 500-600Hz?
I could probly still just tilt the speaker forward (without diffuser) so that both midwoofers are similar distance and angle from the listener.
thanksComment
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I think you may have misunderstood what I was trying to say.
There are two issues. The first one is that due to the wavelengths of frequencies, you will get virtually no benefit from the diffuser until you reach frequencies that have wavelengths less than the size of the diffuser. In my experience, that practically means in the range of 1500hz or above. I don't believe it will do anything noticeable below that. Below that point, the wavelenghts get significantly longer than the diffuser and the driver ends up playing in 4pi space, so it is essentially omnidirectional already. the diffuser simply keeps the driver from transitioning to playing in 2pi space as it does in a typical front firing speaker due to wavelenghts shorter than the baffle width. I believe the diffuse forces the driver to continue to play in 4pi space, hence omnidirectionally.
One way to make it work for lower frequencies, of course would be to make the diffuser bigger, which is probably not practical. For example, the wavelength at 1500hz is 9" long and at 500hz is 27" long.
The second issue you have is that fact the one of your woofers and your tweeter sits significantly in front of the back woofer. So the sound from that rear woofer reaches the listener at a different time, causing phase mismatches, smearing of the sound and possible cancellations. If you are using a digital crossover, you may be able to add delay to the signal going to the front two drivers so that they match up with the back driver. If this was a passive 3way and the back woofer was crossed over at 400-600hz, you might be able to deal horizontal offset in the crossover, but with a 2way crossover, crossing at 1.5-2.5khz, I don't think it would work without something like a ladder delay network.
Actually, you could possibly have a little better results if you did what you suggested, tipping the speaker forward so that the woofers come closer to alignment vertically. However, then your tweeter sits significantly out in front of the woofers.
One other option might be to try a 2.5way passive crossover, using the back driver as the .5 woofer acting as a baffle step filler below 600hz or so.Dan N.Comment
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I get you now, thanks,
well it might be the best option to tilt the box forward, and use some sort of delay on the tweeter. I'm using an active Xover between the midwoofer and tweeter, so I assume some sort of active delay circuit could be made in a seperate box (the crossover is a Behringer unit - I doubt I want to open it up and modify it).
have you seen the MBL111, I had a quick look, do they use a diffuser on the woofer for frequencies below about 600Hz?Comment
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I'm also thinking of taking the up-firing driver out and just using it as a more conventional speaker. :cry:
Maybe I could make another new set of speakers (maybe for rears) and use the diffuser I already made to create new omni directional speakers? Have you got any suggestions on how to use the diffuser to create a new set of speakers?Comment
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Perhaps just as important as the distance between the woofer and mid is "floor bounce" ~ having the woofer low like that and running past 200Hz will help prevent a deep null as the bounce off the floor cancels with the wave coming directly from the mid.Originally posted by joecarrowComment
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I haven't read this thread but looking at the mock-up, aren't your woofers oriented in the wrong direction to be considered an omni? An omni speaker would have to have the magnet side facing outward right? Something like the Scanspeak Illuminator woofer reverse-mounted crossed at 1kHz would be a candidate. At least for my own omni.Comment
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Hi cotdt,Originally posted by cotdt
You could mount them either way and still have an omni effect. The way I'm doing it does not have the problem of basket geometery, magnet frame, etc. causing unusual response anomolies at shorter wavelengths. Also, the magnets coupling are not an issue and the wofers can perhaps be closer together than if mounted with the magnet out. You have to experiment with spacing between the woofers, but once you get that right, the frequency response is smooth and natural. I don't believe that would be the case with the drivers reversed, do to all the structural members, etc. in the path of the sound. FWIW, those were my thoughts when approaching this design.
That said, I did not experiment with the basket out concept, so I can't do a data based comparison. It may work just as well and probably has strengths all its own.Dan N.Comment
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