In post 42 Allen.
And i think i know from where the confusion come from: the tilt observed in TM or MT for the on axis behaviour.
With MTM there is no tilt, the 0* axis is the tweeter axis.
With TM/MT there is a tilt upward or downward and as such is not directly on axis ( as clearly shown in your sketch). I understood this is why you were bothered by the 3D rendering too as it display the correct overall shape but without the tilt 'clearly' figured ( i suppose the front/face of the MT loudspeaker could have been angled backward in order to compensate for it, but i will never know as this rendering are from the internet and i have no more info on them).
In the Biro article the vertical plot ( of TM) shows it much more clearly imo.
Am i on right track?
And i think i know from where the confusion come from: the tilt observed in TM or MT for the on axis behaviour.
With MTM there is no tilt, the 0* axis is the tweeter axis.
With TM/MT there is a tilt upward or downward and as such is not directly on axis ( as clearly shown in your sketch). I understood this is why you were bothered by the 3D rendering too as it display the correct overall shape but without the tilt 'clearly' figured ( i suppose the front/face of the MT loudspeaker could have been angled backward in order to compensate for it, but i will never know as this rendering are from the internet and i have no more info on them).
In the Biro article the vertical plot ( of TM) shows it much more clearly imo.
Am i on right track?
Post #42 buddy.
You said "Since the Butterworths are not symmetrical......"
I said "Butterworths are not symmetrical???"
But then you started turning yourself into a pretzel trying to elucidate.
And to make things worse you've made at least three further posts which you subsequently deleted and/or edited into something completely different.
Clearly it is symmetrical, as is LR, as is everything else........with an MTM configuration.
I wouldn't have even bothered responding if the mistake hadn't caught my eye.
Please tell me what you're confused about here and I will gladly edify you on the topic.
Dave.
Ah, thank you krivium.
That was the Butterworth version. This is the LR version... (it's oversimplified, but that's what makes the point)
Now you have posted a sketch that IS incorrect. This topic does seem to confuse you. 🙂
I think maybe you have an inherent misunderstanding of the radiation characteristics and/or your understanding of the terms is incorrect.
The lobing characteristics of MT versus MTM configurations have been understood for many decades. I don't know why this should be confusing at this point in time.
Anyways, I thought the topic of this thread was an MTM configuration????????? (That's the context that I'm viewing the posts in.)
Dave.
I think maybe you have an inherent misunderstanding of the radiation characteristics and/or your understanding of the terms is incorrect.
The lobing characteristics of MT versus MTM configurations have been understood for many decades. I don't know why this should be confusing at this point in time.
Anyways, I thought the topic of this thread was an MTM configuration????????? (That's the context that I'm viewing the posts in.)
Dave.
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Yes, standard MTM is always symmetrical.
I wrote..
I should have said..
"normal TM lobing" (Perhaps I assumed it was obvious in context..)
I'm willing to stand corrected.
I've used Vituixcad to show that the nulls are present and are at the same angles for both the MTM and non MTM versions.
Hi all,
daily thoughts: thinking about symmetry/asymmetry, vertical asymmetry in speaker acoustic output in regards to listening axis could be there if acoustic centers are not on same vertical axis, or there is time delay between the two like with asymmetric filters or something. Also fact that tweeter would be one end of a baffle and woofer on the other the box would have bit different acoustical effect on both and we get some asymmetry. Also big and smaller transducer would have different directivity at some overlapping bandwidth giving some asymmetry to output. Considering difference in symmetry of TM or MTM is only on relatively small bandwidth, around the crossover, so why not use point source instead if symmetry was important?
Well, question is then whether any of it matters and answer is it depends on how our perception notices any of it, being visually symmetric doesn't matter much if hearing system doesn't detect much difference? Thinking our listening setups, which usually are asymmetric as we and speakers are usually closer to floor than ceiling it all seems pointless debate whether speaker has symmetric acoustic output as long as there is still asymmetry in sound due to strong early reflections as any asymmetry is heard through the reflections assuming ears are at designed listening axis. Asymmetry of speaker could be weapon to combat listening situation asymmetry.
Collecting it up, use what ever sounds better in given application, and the better one knows the application the further the system can be tweaked. This could be TM or MTM or something else depending on a lot of things, just make sure the system works together (speakers with the room) so that the system works nicely for the brain to enjoy.
Have fun!🙂
daily thoughts: thinking about symmetry/asymmetry, vertical asymmetry in speaker acoustic output in regards to listening axis could be there if acoustic centers are not on same vertical axis, or there is time delay between the two like with asymmetric filters or something. Also fact that tweeter would be one end of a baffle and woofer on the other the box would have bit different acoustical effect on both and we get some asymmetry. Also big and smaller transducer would have different directivity at some overlapping bandwidth giving some asymmetry to output. Considering difference in symmetry of TM or MTM is only on relatively small bandwidth, around the crossover, so why not use point source instead if symmetry was important?
Well, question is then whether any of it matters and answer is it depends on how our perception notices any of it, being visually symmetric doesn't matter much if hearing system doesn't detect much difference? Thinking our listening setups, which usually are asymmetric as we and speakers are usually closer to floor than ceiling it all seems pointless debate whether speaker has symmetric acoustic output as long as there is still asymmetry in sound due to strong early reflections as any asymmetry is heard through the reflections assuming ears are at designed listening axis. Asymmetry of speaker could be weapon to combat listening situation asymmetry.
Collecting it up, use what ever sounds better in given application, and the better one knows the application the further the system can be tweaked. This could be TM or MTM or something else depending on a lot of things, just make sure the system works together (speakers with the room) so that the system works nicely for the brain to enjoy.
Have fun!🙂
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Whether a MT, or MTM, or coaxial, or whatever, might work better in a particular environment is a higher level discussion.
The fact remains that a MT configuration is inherently asymmetrical in vertical polar response, and an MTM configuration is inherently symmetrical in vertical polar response. This is inherent in their physical configurations......regardless of crossover implementation.
I think we have some fellas here relying on simulation software and not using their (noodles) common sense.
I see this sort of head-in-the-computer mentality on display in many threads here at DIYaudio.com. (At least many more than there used to be.)
Dave.
The fact remains that a MT configuration is inherently asymmetrical in vertical polar response, and an MTM configuration is inherently symmetrical in vertical polar response. This is inherent in their physical configurations......regardless of crossover implementation.
I think we have some fellas here relying on simulation software and not using their (noodles) common sense.
I see this sort of head-in-the-computer mentality on display in many threads here at DIYaudio.com. (At least many more than there used to be.)
Dave.
Yes. Here's 1 wavelength. The crossover lobing is still there but you have to separate it from the directivity caused by the woofer spacing.
Rather than digging yourself in deeper, why not just go back and correct your depiction in Post #83?
Dave.
Dave.
@Davey
Would you think it is doable and good enough hifi to make a MTM with a cut-off around 1 to 1.2 WL spacing at around 1900 hz with two 5.5" midwoofs and a 1" tweeter, please ?
What slope would you choose for the low pass and high pass of this MTM ?
Edit : in the evil case one is choosing the tricky MTM like me needing less exursion and THD of the midwoofers as well as more sensivity to match a 12" PA driver near 200 hz to 300 hz cut-off, I am not sure to understand fro that experts battle if it is better to choose a narroved dispersion when onne is listening only in his chair (the said 90° phase between the high and low pass : beaming patern) or the greater flater vertical patern (symetric slope ?)
Sorry for re asking the basics...
Would you think it is doable and good enough hifi to make a MTM with a cut-off around 1 to 1.2 WL spacing at around 1900 hz with two 5.5" midwoofs and a 1" tweeter, please ?
What slope would you choose for the low pass and high pass of this MTM ?
Edit : in the evil case one is choosing the tricky MTM like me needing less exursion and THD of the midwoofers as well as more sensivity to match a 12" PA driver near 200 hz to 300 hz cut-off, I am not sure to understand fro that experts battle if it is better to choose a narroved dispersion when onne is listening only in his chair (the said 90° phase between the high and low pass : beaming patern) or the greater flater vertical patern (symetric slope ?)
Sorry for re asking the basics...
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@diyiggy I would place the drivers as close together as possible. For that combo it means a c-t-c distance of about 130mm.
A 2khz crossover frequency should be fine if you have a steeper HP on the tweeter. So, LR24 would be mandatory....in my opinion.
That said, for a small speaker like that I would recommend an MT configuration with a slightly larger woofer. The polar response of an MT configuration speaker is superior.
Dave.
A 2khz crossover frequency should be fine if you have a steeper HP on the tweeter. So, LR24 would be mandatory....in my opinion.
That said, for a small speaker like that I would recommend an MT configuration with a slightly larger woofer. The polar response of an MT configuration speaker is superior.
Dave.
Thanks Davey.
Well I chose the drivers in the wrong order : Faital 12PR320 for the bass, which is not optimal for that task (although it is for home listening) then the two 5.5" in // from 200/300 hz to cope to the 12" sensivity in order to stay confortable to rule the baffle step.
I am not skill confortable to developp a WMMT, cause the two coils low pass overlapp and the lobbing with the tweeter according the layout and the filters choice. A WMTM seems easier but I dunno.
Well I chose the drivers in the wrong order : Faital 12PR320 for the bass, which is not optimal for that task (although it is for home listening) then the two 5.5" in // from 200/300 hz to cope to the 12" sensivity in order to stay confortable to rule the baffle step.
I am not skill confortable to developp a WMMT, cause the two coils low pass overlapp and the lobbing with the tweeter according the layout and the filters choice. A WMTM seems easier but I dunno.
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Thanks Davey.
Well I chose the drivers in the wrong order : Faital 12PR320 for the bass, which is not optimal for that task (although it is for home listening) then the two 5.5" in // from 200/300 hz to cope to the 12" sensivity in order to stay confortable to rule the baffle step.
I am not skill confortable to developp a WMMT. A WMTM seems easier but I dunoo.
Well I chose the drivers in the wrong order : Faital 12PR320 for the bass, which is not optimal for that task (although it is for home listening) then the two 5.5" in // from 200/300 hz to cope to the 12" sensivity in order to stay confortable to rule the baffle step.
I am not skill confortable to developp a WMMT. A WMTM seems easier but I dunoo.
The poor sensivity of the 5.5" NE149W is 87 db/2.83V and cone area is a little short for a low 200/300 hz high pass (but doable) as sensivity because of some baffle step loss. (or it's going back to very low sensivity loudspeaker I always listened )
https://loudspeakerdatabase.com/Peerless/NE149W-08
https://loudspeakerdatabase.com/Peerless/NE149W-08