Is it really needed ?

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   Hey Guys

This is my first post. But i been lurking here for almost 3yrs. Thx for all the info. 

my problem is that im considering building 2 MT122. But i have some 12"
horn speakers, just single instead of double. And im actually really
happy about em. 

The main diffrence in the to speakers are that mine do not use the
baffle A, just Baffle B as listed in the drawings here
http://www.speakerplans.com/index.php?id=mt122

And its about 10cm shorter in depth due to our floor design. Nothing
radical. Iwe been running this system since 1992 with Das AL-20 units
in em. And have newer reconed or replaced the speakers. They been
running mobile and stationary on and off and it have not been a problem
that the Al-20`s was mounted directly on Baffle B, no mis sounds or
anything. 

But now its time for some new Unit`s in my speakers. So iwe ordered 4
MB1000 from Eighteensound. They looked to be the perfect replacements
for Al-20(These arn`t made anymore as far as i know) and B-20 are about
$100 more expensive than MB1000 here locally. 

They have a smaller Xmax and are a big more powerfull. 

But should i just add Baffle A in my speakers as they are ? will that work ? 

build 2 new MT122 ?  or just replace the Al-20`s with the MB1000 without any changes ?

The Little man inside my head is saying. 14 years without Baffle A,
then its proberly not needed. Why is it in every drawing i find online
then ?

thx 4 ya time guys. LMK what u think.

KBmaster

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KBmasterr Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 16 January 2006 Location: Sweden Status: Offline Points: 10	Post Options Post Reply Quote KBmasterr Report Post Thanks(0) Quote Reply Topic: Is it really needed ? Posted: 16 January 2006 at 4:46pm
	Hey Guys This is my first post. But i been lurking here for almost 3yrs. Thx for all the info. my problem is that im considering building 2 MT122. But i have some 12" horn speakers, just single instead of double. And im actually really happy about em. The main diffrence in the to speakers are that mine do not use the baffle A, just Baffle B as listed in the drawings here http://www.speakerplans.com/index.php?id=mt122 And its about 10cm shorter in depth due to our floor design. Nothing radical. Iwe been running this system since 1992 with Das AL-20 units in em. And have newer reconed or replaced the speakers. They been running mobile and stationary on and off and it have not been a problem that the Al-20`s was mounted directly on Baffle B, no mis sounds or anything. But now its time for some new Unit`s in my speakers. So iwe ordered 4 MB1000 from Eighteensound. They looked to be the perfect replacements for Al-20(These arn`t made anymore as far as i know) and B-20 are about $100 more expensive than MB1000 here locally. They have a smaller Xmax and are a big more powerfull. But should i just add Baffle A in my speakers as they are ? will that work ? build 2 new MT122 ? or just replace the Al-20`s with the MB1000 without any changes ? The Little man inside my head is saying. 14 years without Baffle A, then its proberly not needed. Why is it in every drawing i find online then ? thx 4 ya time guys. LMK what u think. KBmaster

zALTEC Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 18 May 2005 Status: Offline Points: 122	Post Options Post Reply Quote zALTEC Report Post Thanks(0) Quote Reply Posted: 16 January 2006 at 5:15pm
	If you're not using Baffle A, you have about 0.7L less in front chamber. That should rise response of about 1dB after 1KHz and you should have -0.5dB from 200Hz to 1KHz. Apart that i think sound quality could suffer because the speaker don't have a "pillow" of air in front of it which usually helps to correct the non-linearity of speaker and making it perform more like a true piston. If i said something wrong please correct me. Edited by zALTEC - 16 January 2006 at 5:16pm

KBmasterr Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 16 January 2006 Location: Sweden Status: Offline Points: 10	Post Options Post Reply Quote KBmasterr Report Post Thanks(0) Quote Reply Posted: 17 January 2006 at 1:30am
	"That should rise response of about 1dB after 1KHz and you should have -0.5dB from 200Hz to 1KHz." That sounds perfect for me. I have 2 15" per side to play from 80hz to 400hz. The Mb1000 only reech there full potential after 400hz and this means i proberly can pull a extra 100w`s out of em. "Apart that i think sound quality could suffer because the speaker don't have a "pillow" of air in front of it which usually helps to correct the non-linearity of speaker and making it perform more like a true piston." That sound very likely. But as i said iwe been running this system for a long time and knows it doesn`t hurt the units to do this. But then again i havn`t tryed with Baffle A mounted. have anyone tryed to take some readings with Baffle A out and With it in to see the diffrence ? Thx alot zALTEC for the reply. KBmaster

Timber_MG Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 27 March 2004 Location: South Africa Status: Offline Points: 1454	Post Options Post Reply Quote Timber_MG Report Post Thanks(0) Quote Reply Posted: 17 January 2006 at 11:28am
	The 12MB1000 is a very fine horn driver though you will note the weight on these units. The first bit of the horn is the most critical and by reducing the effective front volume you can get significant gains at HF. Simulate up your horn in hornresp (it is NOT accurate towards the top end, AJ horn is much better in this regard) to see whether your speaker is in any danger of hitting the horn throat. Also have a look at the effect of a smaller rear chamber. Roborg has had good results by letting the pole vent terminate to the outside air (I am not sure whether the 12MB1000 has one) Keele's rule about HF roll-off goes something like 2fs/Qes iirc and low Le also helps in maximising output in that band. Ciare also do a really nice 12" Horn-driver (12.75MrNd or similar)