tower dimensions

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  • 04-14-2006, 04:30 AM
    hmmmm
    tower dimensions
    Well,
    I actually decided to go with the Modula MTM in a tower version instead of the Eros to save some money in case I wanted to build the center channel later. It uses 2 Dayton RS180's and the Seas 27TDFC Tweeter. As far as the box size...I've read that it should have a 50 liter internal volume with a down firing port. Could I get away with this box size?
    9" x 12" x 45"? It will have a 1 1/2" thick front baffle and a couple 3/4" braces.
    Also, I couldn't find this answer on Htguide either...
    If I have a 3" down firing port- do I need 3" of clearance from the floor? Thanks again.
  • 04-14-2006, 06:53 AM
    kexodusc
    Quote:

    Originally Posted by hmmmm
    Well,
    I actually decided to go with the Modula MTM in a tower version instead of the Eros to save some money in case I wanted to build the center channel later. It uses 2 Dayton RS180's and the Seas 27TDFC Tweeter. As far as the box size...I've read that it should have a 50 liter internal volume with a down firing port. Could I get away with this box size?
    9" x 12" x 45"? It will have a 1 1/2" thick front baffle and a couple 3/4" braces.
    Also, I couldn't find this answer on Htguide either...
    If I have a 3" down firing port- do I need 3" of clearance from the floor? Thanks again.

    If the internal volume is preserved and the front baffle width isn't altered you shouldn't have much issue...as for the downfiring port, I don't see why that is a must.

    Check out Dr K's MTM's on the PE website, he allows for a 49 L box with a rear port if memory serves (though I'm told the Modula MTM is a slightly better crossover for a bit more money).
    FYI - Roman Bednarek's sight has a good write-up on several versions of an MTM with those drivers....
    http://rjbaudio.com/RS180MTM/rs180-rs28-mtm.html

    Worth a read before you order xo parts (if you havent already).
  • 04-14-2006, 07:38 AM
    Feanor
    For what it might be worth
    Quote:

    Originally Posted by hmmmm
    Well,
    I actually decided to go with the Modula MTM in a tower version .... It uses 2 Dayton RS180's and the Seas 27TDFC Tweeter. As far as the box size...I've read that it should have a 50 liter internal volume with a down firing port. Could I get away with this box size?
    9" x 12" x 45"? It will have a 1 1/2" thick front baffle and a couple 3/4" braces.
    Also, I couldn't find this answer on Htguide either...
    If I have a 3" down firing port- do I need 3" of clearance from the floor? Thanks again.

    My BassBox Pro program recommends a 35 litre box for a pair of RS180's when using light damping, (smaller size with more damping). That box would use 3 x 7.75 vent. I don't see why you would want bottom venting.

    35 litres would yield a yield a box of external dimesions about 9 x 12 x 31 inches -- short for a tower.

    But I defer to an expert like Kex, not to mention RJB or Jon Marsh.
  • 04-14-2006, 09:20 AM
    hmmmm
    Bottom venting etc...
    Quote:

    Originally Posted by Feanor
    My BassBox Pro program recommends a 35 litre box for a pair of RS180's when using light damping, (smaller size with more damping). That box would use 3 x 7.75 vent. .

    35 litres would yield a yield a box of external dimesions about 9 x 12 x 31 inches -- short for a tower.
    .

    Well, I'm just going by what they are recommending at HTguide.com for internal volume for a tower. -I guess it helps with a lower bass extension.

    "I don't see why you would want bottom venting"

    I don't want to take quotes from that site, but they say it does make it easier to install a longer port in a narrow cabinent and also has certain advantages (which is above my understanding). Unfortunately, this makes it even taller.
  • 04-14-2006, 09:27 AM
    hmmmm
    Quote:

    Originally Posted by kexodusc
    Check out Dr K's MTM's on the PE website, he allows for a 49 L box with a rear port if memory serves (though I'm told the Modula MTM is a slightly better crossover for a bit more money).
    FYI - Roman Bednarek's sight has a good write-up on several versions of an MTM with those drivers....
    http://rjbaudio.com/RS180MTM/rs180-rs28-mtm.html

    Worth a read before you order xo parts (if you havent already).

    Thanks Kex,
    I'll read those write-ups before I order anything. I've also read the Modula's crossover is better- it's still cheaper than building the Eros! I figured I might want the center channel etc... in the future so I'll save the money and do the Modula.
  • 04-14-2006, 10:23 AM
    Feanor
    Interesting
    Quote:

    Originally Posted by hmmmm
    Well, I'm just going by what they are recommending at HTguide.com for internal volume for a tower. -I guess it helps with a lower bass extension.

    "I don't see why you would want bottom venting"

    I don't want to take quotes from that site, but they say it does make it easier to install a longer port in a narrow cabinent and also has certain advantages (which is above my understanding). Unfortunately, this makes it even taller.

    I had a quick look at HTguide but didn't spot the tower volume reference -- not matter. But I did see that Jon Marsh's original MTM was build in a 1 ft^3 Parts Express cabinet.

    Well, I guess you could put a relatively vent on the top of shallow cabinet. Might want to cover it with a grill of some kind, though. :biggrin5:
  • 04-14-2006, 01:21 PM
    kexodusc
    Quote:

    Originally Posted by Feanor
    But I defer to an expert like Kex, not to mention RJB or Jon Marsh.

    Good, I defer to RJB and Jon Marsh daily...those guys know more about crossover design than I know about myself!!! I can't even spell cauer eliptic let alone desing one :D


    Quote:

    Originally Posted by Feanor
    I had a quick look at HTguide but didn't spot the tower volume reference -- not matter. But I did see that Jon Marsh's original MTM was build in a 1 ft^3 Parts Express cabinet.

    Well, I guess you could put a relatively vent on the top of shallow cabinet. Might want to cover it with a grill of some kind, though. :biggrin5:

    The bottom venting would be minimally easier to install I suppose, but a decent elbow like you'd use for plumbing, provided the internal volume/length is the same would allow for rear or front venting...don't worry about getting the port length exact...try modelling a few different lengths give or take an inch and it won't make 1 lick of audible difference. There'll be more variance in the Fs of the drivers than the tuning frequency from a bit of port length caused by an elbow....I'd just take a string, measure the inside and outside lenghts of the elbowed vent and use the average as an approximate if you really want to get precise...there's probably a better math formula somewhere though.

    I'd worry about bottom venting if they were only a few inches from the floor...ideally you'll want 4 to 6 inches of clearance for any port to limit noise!