Reduce MT-130 horn
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=89614
Printed Date: 27 March 2026 at 11:02am
Software Version: Web Wiz Forums 12.08 - https://www.webwizforums.com
Topic: Reduce MT-130 horn
Posted By: vicenturi
Subject: Reduce MT-130 horn
Date Posted: 25 November 2014 at 10:48am
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Hi! I´m planing to build some MT-130 with limmer 042 over it. The question is that I´ll like to reduce the lenght of the horn in 10cm to make the speaker thinner to fit better the limmer horn. How will this afect to the speaker response?  Regards! |
Replies:
Posted By: DMorison
Date Posted: 25 November 2014 at 12:12pm
| It won't provide its acoustic loading down to as low a frequency, and will exhibit a wider coverage pattern towards the bottom of its range, therefore will need crossed over higher than the original. |
Posted By: vicenturi
Date Posted: 25 November 2014 at 12:21pm
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Thanks DMorison. And you think it will get low enough to meet the ES18BPH under it? |
Posted By: nickyburnell
Date Posted: 25 November 2014 at 5:53pm
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I forgot I built these once! Long distance cab, used them on a farm, up close seemed like they wern't on, but at a distance were mad loud. ------------- It's everything, not everythink! |
Posted By: DMorison
Date Posted: 26 November 2014 at 1:52pm
Wouldn't know without modelling it, sorry. Also haven't used that bass bin so I wouldn't know what upper cutoff it can use and still sound good. If it's really OK up to 250 per the plan then you might be OK. HTH, David. Edit - corrected typos, added reference to nominal cutoff of ES18.
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vicenturi wrote:Posted By: vicenturi
Date Posted: 28 November 2014 at 1:34pm
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Someone can help me to sim this modified mt-130? I´m planning to build one model to test it with measuremen equipment but will like to see what hornresp or similar program tells. The possible drivers that I will mount are the pd121 or the rcf 12 p110k. I´ll like it to work between 200-550 Hz. |
Posted By: vicenturi
Date Posted: 01 December 2014 at 11:54am
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I´m trying to sim my mod. mt130 in hornresp but I´m new in this and don´t know if I´m doing it good. Someone can show me a screen capture of the input parameters of a normal mt130? Thanks! |
Posted By: vicenturi
Date Posted: 04 December 2014 at 11:31am
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Trying to sim the speaker in hornresp, in the schematic diagram window i see that apears a conical flare adaptor that I think that is not suposted to be there in this speaker. Anyone can help me with the input parameters? There is a screenshot of what I´ve introduced, and the diagram with the conical flare marked.   |
Posted By: vicenturi
Date Posted: 05 December 2014 at 10:15am
| Anyone? |
Posted By: DMorison
Date Posted: 05 December 2014 at 12:56pm
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Am not a Hornresp expert but as far as I can see I'd model it a bit differently: 1: Rear chamber calculates out to 15l max so will be about 12-13l net by the time you account for the driver in it. 2: Front chamber includes the space in the cone of the driver plus the 28cm disc in the first, 10mm baffle - that disc alone is over 600cm^3 so I've estimated 2l total. 3: S1 & S2 are the 27.3*6.8cm aperture in the second, 18mm baffle. 4: I put a very short section (S2 - S3) to account for the change in height from that second baffle to the full horn height. 5: As all the sections are straight sided I used conical rather than exponential flares. 6: Your two sections (with corrected areas) then become sections 3 and 4. 7: There's no port from the chamber to the horn, so I used standard driver alignment (I think you used "Compound") and didn't put anything in Ap(1) and Lp(t). 8: Midranges should be modelled in 4Pi (full space) rather than 2Pi.  Black is your shortened version, grey is as close as I can get to the original. You should still get down to around 200Hz if this is accurate, but you also may have more dips further up in the midrange (600Hz) which I didn't expect. I know Hornresp always shows more rolloff at the upper end of a horn's response than people report in real life, so I don't know how much of an effect that will have. Cheers, David.
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Posted By: vicenturi
Date Posted: 05 December 2014 at 9:57pm
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Thanks for your help DMorison, very usefull! The diferences in the area sections are because I´ve modeled the speaker in CAD program with small diferences in pieces (for easyer build) and the dimensions are directly measured in the model. This are my revised input parameters and the results.   How does this look to you? I get this message in the calculation proces, is it normal?  Kind regards! |
Posted By: DMorison
Date Posted: 06 December 2014 at 9:47am
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That looks pretty realistic to me now, that popup warning comes form having the very short section in to account for the step from the baffle to the full height of the horn - you could try modelling without that to see if it makes any difference, but I prefer to be as accurate as possible in case there is some unexpected effect I'd otherwise overlooked. Your curve looks very similar to mine, the dip in the mids is pushed up to a slightly higher frequency which may even be a good thing. Edit - just tried modelling a smoothed out version without accounting for the step and the difference is so small as not to be worth it.
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Posted By: vicenturi
Date Posted: 12 December 2014 at 10:32am
| A model coming soon. I'll upload some measurements when finished. |
Posted By: Mattias Andersson
Date Posted: 28 February 2015 at 9:35am
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Hey! Your light version of the mt130 is an interesting project. Did you do any measurements? I am thinking of building some mt130 too, but the full length version, dual 12's and a 2" hf driver. |
Posted By: PavelP
Date Posted: 28 February 2015 at 11:52am
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I think there's no need to shorten mt-130 -- it's short enough.I'll tell you more, it's not long enough to work with es18. First of all replace 2xPi with 4xPi because top is sitting on subs, so it is a free space. Real response will be about 300-350Hz 0db or 250Hz -3db. Second, if you're planning to listen to music, sub shouldn't be used up to 200Hz. 150-180Hz is the limit for such a construction. Try mt121 without limmer 042, because it's a horn for semi professional very compromised use with small subs. You need at least 1xmt121 with 1xes18 to reach a normal pressure level and match each other. |