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    Can anyone offer info on TM112 venting?

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    bordonbert

    Posts : 767
    Join date : 2015-01-28
    Age : 97
    Location : Southern England

    Can anyone offer info on TM112 venting?

    Post by bordonbert on Thu May 14, 2015 9:47 am

    Wow, first post ever in this forum. I'm humbled!

    Is there anyone out there with a TM112 who can give me a description of the venting employed by H&K? It could be a properly designed reflex port tuned to the cabinet volume and driver resonance, or it could just be " 's a vent mate, 's an 'ole in the box", (or the equivalent in German cockney!) It uses a Celestion Vintage 30 but this driver is usually not considered best suited to port loading, it usually performs best in a plain sealed or open back cab. So is the "vent" just an opening to the outside air, or is it a properly loaded reflex port which bolsters and extends bass response? And can you estimate the approximate dimensions of either the port or the 'ole?

    The TM212 is described the same way, as vented. I'll post a query there too in the hope of catching a few more users.
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    ricksteruk

    Posts : 13
    Join date : 2015-04-13
    Location : Morecambe, England

    Re: Can anyone offer info on TM112 venting?

    Post by ricksteruk on Fri May 15, 2015 4:47 am

    I've been trying to look for some info on that cab too - but can't seem to find any internal pics.

    I'm pretty sure that H&K would not just cut a random hole in the cab. They will surely know the internal dimensions of the cab and make the port the right size in order to boost the bass a little.

    I think the V30 speaker is a bad choice for the 1x12 - it is very mid heavy. A speaker with less pronounced top and a deeper bass - like some of the new Celestions - Cream Alnico, CreambackH75, A type, V type seem to have a LOT more bass.
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    bordonbert

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    Re: Can anyone offer info on TM112 venting?

    Post by bordonbert on Fri May 15, 2015 10:41 am

    Thanks for the backup Rick. I'm finding just the same as you. I'm using a TM36 with 2 1x12 Harley Bentons, (Thomann's own brand). They're cheap as chips but, apart from the soft outer Tolex type covering, are not bad at all. They share the Celestion Vintage 30 with the H&K TM112. It has taken me a while to come to terms with the sound and get the best out of them. I had to take off the top and bottom back panels, (they're open back by design), and seal the cabinets. When I did that I got an improvement in the bass response but I'm still finding that it is only just adequate. It would be nice to feel I have a little in reserve.

    The mids are great and I can set them raspy, honky, or smooth as I want. The top end is clear and never gets harsh at all. It's just the lack of the option of a deep bottom end that I have to solve. Sealed box cabinets of the same volume for a specific driver don't have very much influence on the bass they output, (maybe that's against "common knowledge" but it's true). All they are doing is enclosing a volume of air which gives a particular springiness to the cone suspension which imparts a resistance to its movement. This is the same for any box (within reason) of the same volume. Panel resonances due to the design and materials and the like will affect the mid range balance a heck of a lot more than the bottom end. These cabs sound great in that way, I am happy with the mids.

    Like you I am sure that H&K will have a specific design to the venting, I just wondered why they specifically used the term 'venting' instead of 'porting' or 'reflex loading', and why they bothered in the first place! My only guess was that they may not have used the standard cylindrical port. That said, the V30 is not a good candidate for reflex loading with the generic port setup. Celestion do not publish Thiele Small design parameters for their guitar drivers as they do not go far enough down in frequency and are not working in small signal mode where the parameters are measured.

    I had thought to try out a new back with a port in it roughly based on the H&K, (after some calculations to trim it), to see if things improved. With only the back altered it meant I had not changed the cabinet beyond recovery. It certainly is an oddity. Maybe I will just swap out one of the V30s for a more bassy driver and get the bass while keeping what I currently like.
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    Raf0419

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    Join date : 2015-12-25
    Location : Usually bw a rock and a hard place...in NC

    Re: Can anyone offer info on TM112 venting?

    Post by Raf0419 on Sun Jan 31, 2016 8:27 am

    I know these posts are nearly a year old, but I recently did a speaker swap and took a few images. The TM-112 cabinet has two vents as you can see below. Cabinet sides are dovetailed and glued.  They're not the prettiest dovetails, but effective no doubt. Sorry I didn't take any closeup images of the jointery. Here's a look inside of the TM112 Cabinet: " />

    By the way, the ET-65 from Warehouse Guitar Speakers is a Creamback alternative. To my ears it has more mids and lows than a V30. I originally purchased one ET-65 to compare against my other V30 loaded TM112. I thought I might end up purchasing another, but the V30 + ET-65 mini-stack of TM-112s has a mix I rather enjoy.

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