TDA MT121 - HR Plots
Printed From: Speakerplans.com
Category: Plans
Forum Name: MT122
Forum Description: Discussion / Questions about the MT122
URL: https://forum.speakerplans.com/forum_posts.asp?TID=77536
Printed Date: 26 March 2026 at 11:31pm
Software Version: Web Wiz Forums 12.08 - https://www.webwizforums.com
Topic: TDA MT121 - HR Plots
Posted By: levyte357-
Subject: TDA MT121 - HR Plots
Date Posted: 28 March 2013 at 11:40am
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http://forum.speakerplans.com/simplified-mt121-plans_topic16270.html" rel="nofollow - http://forum.speakerplans.com/simplified-mt121-plans_topic16270.html
Attempted plot from TDA MT121 plan,  Comments? ------------- Global Depopulation - Alive and Killing. |
levyte357 wrote:
Replies:
Posted By: Dref
Date Posted: 28 March 2013 at 12:51pm
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Hi Lev There will be a front chamber (Vtc) because of the shape of the cone. Making the rear chamber smaller will improve the response. Try and play around with the directivity function. (Ctrl+R) ------------- A proper build subwoofer will be the only thing in a room that is not shaking. |
Posted By: levyte357-
Date Posted: 28 March 2013 at 3:16pm
Cheers for that. Really trying to sim TDA MT121 as is, to get realistic plot of how cab performs with various drivers. So, what would suggested refinements to above input values be, for existing design? ------------- Global Depopulation - Alive and Killing. |
Posted By: DiscernAudio
Date Posted: 28 March 2013 at 3:27pm
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Is not hornresp only accurate up to a certain freq? If so what is that "cutoff"? |
Posted By: boots-hifi
Date Posted: 28 March 2013 at 10:05pm
| I've just loaded mine with BMS 12N610's and 4550's on RCF HF64 horns if you fancy toying with that combo. Gonna try and get some smaart plots over this weekend incase your interested. |
Posted By: Dref
Date Posted: 29 March 2013 at 12:22pm
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I think the rear chamber volume should be less than 20 L. As far as I can calculate from the dimensions, the rear chamber is 15.7 L in its empty state. So try with 8-10 L.
Also the constant directivity option is very unfair for such a narrow dispersion horn. Try to make an on-axis(0 degree) plot with an 8 L rear chamber and lets see how that looks. ------------- A proper build subwoofer will be the only thing in a room that is not shaking. |
Posted By: levyte357-
Date Posted: 29 March 2013 at 12:45pm
Will be interesting to see real plot vs HR sim, to identify the inaccuracy. Trying to identify best drivers for cab, then where eq will be needed to flatten response. Some of us need exceptionally flat 200-500hz response. ------------- Global Depopulation - Alive and Killing. |
Posted By: levyte357-
Date Posted: 03 April 2013 at 11:47am
Done  Does this seem a little too optimistic ? ------------- Global Depopulation - Alive and Killing. |
Posted By: MarjanM
Date Posted: 03 April 2013 at 2:36pm
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Yes it does. ------------- Marjan Milosevic MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
Posted By: levyte357-
Date Posted: 03 April 2013 at 2:40pm
Hmmm.. Trying to find well suited driver, simming with parameters first.. But if sims not accurate, what then.. Some of us can't afford testing with conveyor belt of driver purchases. ------------- Global Depopulation - Alive and Killing. |
Posted By: DiscernAudio
Date Posted: 03 April 2013 at 2:45pm
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Possible to purchase test and return? I know Parts Express here lets us do that |
Posted By: Dref
Date Posted: 03 April 2013 at 3:05pm
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Something went wrong with your sim? Here is my sim:  Try to find a driver with a lighter cone. If it has to be a Kappa then go for the non Pro version. ------------- A proper build subwoofer will be the only thing in a room that is not shaking. |
Posted By: levyte357-
Date Posted: 03 April 2013 at 3:14pm
Indeed.. Somehow I had "incorrect" Driver Sd in T/S parms...  Cheers Dref. EDIT:But please explain Lrc value? ------------- Global Depopulation - Alive and Killing. |
Posted By: MarjanM
Date Posted: 03 April 2013 at 3:34pm
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Lev, the TDA version will not be much different then the original. Difference will be in order of 1 db here and there. So whatever suits the MT will also suit the TDA version. People have used lot of different 12 inches with various results but none was actually too bad. The main question is what will the HF driver be and how low it can go. Using a bit eq on the top part of the 12 inch response will not be too bad thing. ------------- Marjan Milosevic MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
Posted By: levyte357-
Date Posted: 03 April 2013 at 3:44pm
Have used quite a few drivers in TDA/Standard MT121, with good results. Trying to identify drivers, with better low mid response. ------------- Global Depopulation - Alive and Killing. |
Posted By: MarjanM
Date Posted: 03 April 2013 at 4:00pm
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You can not go wrong with 4550 man. ------------- Marjan Milosevic MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
Posted By: levyte357-
Date Posted: 03 April 2013 at 4:13pm
HF already sorted mate.. I only use 2" in MT121s. Need 12" driver that is flatter in response 200hz-400hz. ------------- Global Depopulation - Alive and Killing. |
Posted By: MarjanM
Date Posted: 03 April 2013 at 4:16pm
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There will be a peak at about 400Hz no mater which driver you use. ------------- Marjan Milosevic MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
Posted By: levyte357-
Date Posted: 03 April 2013 at 4:30pm
Assuming Dref plots are realistic, flattening peaks around 200/400 are not a problem. Problem is hornloaded kicks are mostly no good for low mid, so it's either get low mid from MT, or reflex kick cab. (For use on Scoop systems). ------------- Global Depopulation - Alive and Killing. |
Posted By: boots-hifi
Date Posted: 03 April 2013 at 4:37pm
 BMS 4550 and BMS 610N are the best combo for an MT. Thats what I loaded the MTs I bought from you with Lev and they play almost flat with no eq apart from that little dip at 500hz. Ill load up some plots from Smaart a bit later if you like? |
Posted By: levyte357-
Date Posted: 03 April 2013 at 4:45pm
Would be great... Cheers. ------------- Global Depopulation - Alive and Killing. |
Posted By: DiscernAudio
Date Posted: 03 April 2013 at 4:54pm
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When in constant directivity mode, is hornresp aaveraging the response within the angle of the horn? |
Posted By: DiscernAudio
Date Posted: 03 April 2013 at 5:06pm
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Or is it averaging from 0 - 90deg off axis? |
Posted By: levyte357-
Date Posted: 03 April 2013 at 5:10pm
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Just modeled the B&C 12PE32, that many rage about, and it doesn't seem so hot 200-400hz. ------------- Global Depopulation - Alive and Killing. |
Posted By: boots-hifi
Date Posted: 03 April 2013 at 10:21pm
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Lev little test myself and Bee ran yesterday in the sun! TDA MT loaded with... BMS 12N610 and BMS 4550. HPF 150 - BW 24 LPF BW - 12 HPF - 1K BW 24 No eq, Pink noise simed. This may or may not be of any interest to you. 
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Posted By: bee
Date Posted: 03 April 2013 at 10:34pm
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best sounding hf i have heard in an mt by a long way.... the 12 is on par with the b&c 12ndl76, which is my fav, Boot's combo defo sounds sweet....... on axis there is not alot of differance in the standard mt to the tda one, off axis the original is better..... The dip at 500hz is not the driver or cab but something in the way we set up the rta stuff..... very strange..... plotts where taken at 5m mic was leval with 12"..... pink noise was used..... a wall was within 2m of the right of the stack and my workshop was 15m infront of stack, so not ideal testing area, but good enougth for what we was doing..... next time we will do a full sweep signal of cab, and calibrate (spl) on mic..... there is a topic on hear where i posted up actual sweep test's on both mt121 and tda mt121, both loaded with same drivers.... ill see if i can find plotts, these where taken at 2m, sweep, calibrated mic, input 2,83v...... so the plotts are spot on......
------------- https://www.elements-audio.com |
Posted By: MarjanM
Date Posted: 03 April 2013 at 10:54pm
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Bee which horn is that? ------------- Marjan Milosevic MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
Posted By: levyte357-
Date Posted: 03 April 2013 at 11:15pm
This is actual Smaart plot with 12" run downto 150hz !? And BMS 4550 without Eq? With which 1" horn mate ? Have you tried running MT with approx 400W power input down-to 150hz? Cheers for info, Lev ------------- Global Depopulation - Alive and Killing. |
Posted By: bee
Date Posted: 03 April 2013 at 11:47pm
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this is the mt121 half of the roger mogule mt122 design Marjam, not sure on make of the hf horn not a plott Lev an rta reading of cab... i.e. played pink noise through cab and recorded info in to pc via a rta mircophone via smaart..... no eq just xover only...... blue is the 12" section red is the 1" on horn.... both 12" and 1" was tra'd on it own and combined.... the dip at 500hz is a cause of reflection from a wall less than 2m to the right of the cab ignor spl readings, these are not correct........ the reading with a 10 second average looks alot smoother..... the signal being picked up below 60hz was to do with the mixer output or sound card not sure, need to re check all settings and outboard gear 1 piece at a time..... to find where it was coming from.....
------------- https://www.elements-audio.com |
Posted By: MarjanM
Date Posted: 04 April 2013 at 12:42am
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The HF shows a very strange graph for the 4550. So i guess the horn is quite small. It start going down at like 1.5Khz and it has too much of the very high frequencies. This later not bad at all actually. ------------- Marjan Milosevic MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
Posted By: MarjanM
Date Posted: 04 April 2013 at 12:42am
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Any picture of the box? ------------- Marjan Milosevic MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
Posted By: bee
Date Posted: 04 April 2013 at 12:44am
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sure give us a sec and ill find one..... ------------- https://www.elements-audio.com |
Posted By: bee
Date Posted: 04 April 2013 at 12:47am
  top cab is the mt bottom left is a turbo sound bhp115 bottom right is my new prototype bhp115 ------------- https://www.elements-audio.com |
Posted By: bee
Date Posted: 04 April 2013 at 12:52am
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the plot may be due to xover position, the 12" was crossing out a bit above where the 1" was crossing in. this where it sounded best, not where the driver could be xover at.... ------------- https://www.elements-audio.com |
Posted By: MarjanM
Date Posted: 04 April 2013 at 12:54am
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That is fine, i am a bit puzzled by the response 6Khz and above. That is the RCF H64 horn and i have measured that one with 4550 and my results were not even close to what you have there. What kind of mic you are using? Is it calibrated? ------------- Marjan Milosevic MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
Posted By: bee
Date Posted: 04 April 2013 at 12:54am
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ill ring boots in the morning and see if he had a combined reading, im sure i saved a snapshot.... ------------- https://www.elements-audio.com |
Posted By: bee
Date Posted: 04 April 2013 at 12:59am
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yes but, was not calibrated for spl.... soundcard and mic calibrated, but there was a small issue somewhere as it was picking up a signal below 60hz which was due to something in the signal chain post mic but this noise was not effecting the higher frequancys..... but in saying this there was alot of top end shine from this driver above 6k infact it is one of the best combo's ive heard yet in the mt... there may of been a bit of reflection going on, due to a wall 2m to the right of the cabs, but not that would aid the hf.... my ears say the plott is correct....
------------- https://www.elements-audio.com |
Posted By: bee
Date Posted: 04 April 2013 at 1:12am
this is another plott taken at the same time of a turbo bhp115 and my new prototype bhp 115, this shows no added noise in the hf region just a small amount of background noise..... hope this helps....
------------- https://www.elements-audio.com |
Posted By: MarjanM
Date Posted: 04 April 2013 at 1:35am
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What i was asking is the mic calibrated? Calibrated as factory calibrated to be flat. ------------- Marjan Milosevic MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
Posted By: boots-hifi
Date Posted: 04 April 2013 at 7:04am
Berry ECM mic Marjan, RCF horn and no the mic hasnt been calibrated since it came out of the shop. These were just readings all done just out of intrest as Id just loaded the drivers into the cab. At the time we were A/B Bee's new kicks against my Turbo's and as I had the MTs in the van we thought why not have a play with them too. Lev all settings were just a rough guess, where would you cross the 12" at? Bearing in mind ill be running 2 a side from a PL 4.0 so there be getting more than 400w. I think the plots came out quite well, although there is an increase above 6k this sounded good and isnt a bad thing as Majan mentioned. Im quite happy to bring a loaded cab out for more testing if your imtrested lev?r |
Posted By: levyte357-
Date Posted: 04 April 2013 at 9:47am
If the 12" is happy playing down to 150hz at gig levels, will give vocals serious bit of warmth, not many 12s in MT121 would be happy doing that. Was told MT122 is good down to about 140hz. I Usually bring MT121 12" section in, about 180hz. Also natural increase above 6K from Horn & comp, would also be a plus in my book. ------------- Global Depopulation - Alive and Killing. |
Posted By: bee
Date Posted: 04 April 2013 at 10:52am
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Lev ive allways run my mt's down to 150hz a gig volume, never been an issue, driver in my old mt's was the 12ndl76, i cant say other drivers sound good down at 150hz but boots's combo sounds sweet. The sound card was calibrated via smaart, the ecm mic is not the best but is not that far out to the £300 pluss mics, there may of been somthing going on to get it that good above 6k, but it was not eq... im sure boots would be happy to re run test when we get a good weather day again, ill bring my laptop next time and do measurments using both laptops, to see what variance there is from both measurment setups...... ill try and do the tests in a more open area too.....
------------- https://www.elements-audio.com |
Posted By: Dref
Date Posted: 04 April 2013 at 11:57am
This is what I found in the help file: Also, horn flare directional characteristics are not taken into account when calculating the constant directivity SPL response. This means that the actual upper frequency rolloff for a cone type drive unit coupled to a straight-axis horn can in some cases be more than one octave higher than the predicted value. Lev: Lrc = Rear chamber average length (cm). Don't worry to much about it here. ------------- A proper build subwoofer will be the only thing in a room that is not shaking. |
Posted By: DiscernAudio
Date Posted: 04 April 2013 at 2:39pm
That would lead me to believe that it averages the SPL response from 0 deg to 90 deg (the max deg off axis horn resp will calculate) since the horn angle is not taken into consideration |
Posted By: Dref
Date Posted: 05 April 2013 at 11:00am
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To be honest I am not sure. Best to ask David I would say. But still there is no point in including angles outside the dispersion angle of the horn. ------------- A proper build subwoofer will be the only thing in a room that is not shaking. |
Posted By: levyte357-
Date Posted: 11 July 2013 at 12:13am
Recently tried Paudio SN12Bs, and they started chuffing at 180hz. Strange as they used to be recommended drivers for the cab. ------------- Global Depopulation - Alive and Killing. |
Posted By: RealitySound
Date Posted: 21 August 2013 at 11:21pm
I am trying to teach myself hornresponse............can you please tell me how you got Lrc- 17.00 and Atc- 519.00? ------------- When you gonna send me some $$ mate ? |
Posted By: bee
Date Posted: 21 August 2013 at 11:26pm
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vrc is 17.60 lrc is 14.80 vtc is 1108.00 atc is 615.75 lrc is the length of the rear chamber.... ------------- https://www.elements-audio.com |
Posted By: RealitySound
Date Posted: 21 August 2013 at 11:41pm
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Thanks Bee. I have been using this as a guide- (http://www.freespeakerplans.com/forum/7-general-forum/13045-hornresp-newbie?start=10) Assuming the piece of ply being used behind the driver is 18mm thick, wouldn't lrc be 13.0? (148-18?) http://s150.photobucket.com/user/ob1bda/media/1d6af7a0-abfb-4435-b9fb-a7fa5337cd75_zps2646ae89.jpg.html" rel="nofollow">  ------------- When you gonna send me some $$ mate ? |
Posted By: bee
Date Posted: 21 August 2013 at 11:45pm
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no 14.8 baffle to rear of cab, the plan is miss leading as it shows rear hatch batton... rear baffle to external rear of cab is 16.6 minus of 18 = 14.8 ------------- https://www.elements-audio.com |
Posted By: RealitySound
Date Posted: 21 August 2013 at 11:48pm
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Ahhh, Ok. So it should look like this instead- http://s150.photobucket.com/user/ob1bda/media/0358916c-6d5c-45fc-aea8-6f9ed18c5413_zpse4b8e39b.jpg.html" rel="nofollow">  ------------- When you gonna send me some $$ mate ? |
Posted By: RealitySound
Date Posted: 22 August 2013 at 12:11am
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Now I am trying to figure out how you got vtc - 1108.00..............? ------------- When you gonna send me some $$ mate ? |
Posted By: DiscernAudio
Date Posted: 22 August 2013 at 4:21am
Vtc=Atc*1.8 (for 18mm spacing) |
Posted By: Dref
Date Posted: 22 August 2013 at 12:23pm
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But for a more realistic simulation you should find out the volume of the void arising from the speaker cone as it will be more than the 18 mm transition piece.
Nice that you have started learning Hornresp by the way. I am sure you are gonna love it when you get the hang of it.  And remember the build in help file  .------------- A proper build subwoofer will be the only thing in a room that is not shaking. |
Posted By: RealitySound
Date Posted: 22 August 2013 at 3:03pm
you mean this Dref? http://s150.photobucket.com/user/ob1bda/media/5af43d30-b299-490b-8f04-5bef073fccff_zps572f54e7.jpg.html" rel="nofollow">  ------------- When you gonna send me some $$ mate ? |
Posted By: DiscernAudio
Date Posted: 22 August 2013 at 7:49pm
Yes, and add that to the 1108 (for 18mm tranny) |
Posted By: Teunos
Date Posted: 22 August 2013 at 8:05pm
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Hornresp now has a front chamber volume estimation tool, works perfectly.
------------- Best regards, Teun. |
Posted By: DiscernAudio
Date Posted: 22 August 2013 at 8:34pm
Ahh yes! forgot about that |
Posted By: RealitySound
Date Posted: 23 August 2013 at 2:00am
18mm Tranny? Orange bit? http://s150.photobucket.com/user/ob1bda/media/f314badd-3d6e-40c5-a283-48cdb590fcfb_zpsf63161f9.jpg.html" rel="nofollow">  http://s150.photobucket.com/user/ob1bda/media/854e98d8-7101-4d63-84bc-feabce72e3b7_zpsc46b2676.jpg.html" rel="nofollow">  ------------- When you gonna send me some $$ mate ? |
Posted By: DiscernAudio
Date Posted: 23 August 2013 at 2:21am
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Except the orange extends the full 280mm |
Posted By: RealitySound
Date Posted: 23 August 2013 at 2:24am
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Right.......of course. http://s150.photobucket.com/user/ob1bda/media/24334cb9-ce72-43ea-8d2a-a7b34ab5f663_zps2e53455e.jpg.html" rel="nofollow">  ------------- When you gonna send me some $$ mate ? |
Posted By: Dref
Date Posted: 23 August 2013 at 3:00pm
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Yep, except the red part is a bit misleading because it doesn't look that conical ;) It sound like there has be quite a few updates since my current version of hornresp. I think its time that I update ------------- A proper build subwoofer will be the only thing in a room that is not shaking. |
Posted By: RealitySound
Date Posted: 23 August 2013 at 3:05pm
Well, its difficult drawing with a mouse LOL  The red bit I was drawing is the area above the cone.That correct? http://s150.photobucket.com/user/ob1bda/media/2c49473a-2324-442b-814f-fae09ba9f83d_zps752753ea.jpg.html" rel="nofollow">  ------------- When you gonna send me some $$ mate ? |
Posted By: Dref
Date Posted: 26 August 2013 at 1:59pm
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Much better. It was just to be sure no one misunderstood. ------------- A proper build subwoofer will be the only thing in a room that is not shaking. |
Posted By: RealitySound
Date Posted: 26 August 2013 at 2:08pm
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So Vtc would be the orange bit plus the red bit? ------------- When you gonna send me some $$ mate ? |
Posted By: DiscernAudio
Date Posted: 26 August 2013 at 2:21pm
Plus the black bit between the red and the orange pits in that last pic |
Posted By: RealitySound
Date Posted: 26 August 2013 at 2:24pm
Of course. The black bit just being the 'basket' outline. What do you guys calculate it to be? You just ball parking the area above the cone? ------------- When you gonna send me some $$ mate ? |
Posted By: DiscernAudio
Date Posted: 26 August 2013 at 4:02pm
get some measurements and Use hornresp cone volume calculator tool add it to 1108 + plus the volume of the space added due to the thickness of the gasket (after compressed) |
Posted By: RealitySound
Date Posted: 16 September 2013 at 1:35am
anybody mind simming this driver for me?
------------- When you gonna send me some $$ mate ? |
Posted By: bee
Date Posted: 16 September 2013 at 7:29pm
  didn't sim too well.....------------- https://www.elements-audio.com |
Posted By: RealitySound
Date Posted: 16 September 2013 at 9:47pm
DAMN IT!  .................thanks though Bee ------------- When you gonna send me some $$ mate ? |
Posted By: hmaudio
Date Posted: 30 December 2013 at 10:06pm
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could eny one sim this driver in a mt121? see if it would work well or not.
------------- Nottingham based cab builder. https://www.facebook.com/HMAudio-154352667920145/?ref=bookmarks This account is used by 2 people. |
Posted By: DiscernAudio
Date Posted: 02 January 2014 at 8:33pm
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Posted By: levyte357-
Date Posted: 02 January 2014 at 9:53pm
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Would be interesting comparing actual measured plots, against HR sims. But then, 'lil eq, will make many compatible drivers, sound decent in MT. ------------- Global Depopulation - Alive and Killing. |
Posted By: DiscernAudio
Date Posted: 03 January 2014 at 5:41am
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Sorry my plot was for orig MT not TDA vers |
Posted By: Avatron
Date Posted: 12 February 2014 at 11:57pm
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On the previous pages, VTC was 1108 for the MT 121. 615,75 (ATC) x 1,8 = 1108 But in the plan the baffle is 12mm, from where do come the 1,8?
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