semi-Infinite baffle for Lowther DX45?

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I recently bought a pair of Lowther Dx45's and want to build a low spl system for a small room.
The listening room is about 16'x20', ~8' ceiling. I normally listen at around 60~70dB (apartment, so....), so the 100w power handling of DX45 is probably over-kill. I want the Lowther to handle down to around 120~150Hz, anything lower will be done/augmented by a sealed woofer.

Here is my question: instead of doing a more common BLH or Voigt pipe which are capable of doing high SPL and lower bass (I need neither of these two), can I just use a relatively large sealed enclosure as a semi-infinite-baffle? Say, 4 times Vas which is about 18 liters.

again, the listening volume is only 60~70db.

If it is a go, what will the bass roll-off look like? still 12db/oct ? starting at what point?

I don't want to do an open-baffle at this point.

Thanks for any input.
 
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Great idea. Could you build it into your wall or do inwalls?

The roll off will be shallower than 12db/oct. I'm not exactly sure what the final Q would be as that depends on how big you actually make the box. But could be more like 9db/oct. Normally I'd warn you about excursion going way up, but if you're not listening loud... I'd still recommend a high pass if using subs, then the midrange and treble will not compete with the bass output.

Sounds great!
 
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A very good semi IB is the Nautaloss sealed spiral TL. It has zero coloration due to back reflections as it acts like an acoustic black hole. Size it so that the total internal volume is at least equal to the optimal sealed alignment is based on Vas. Make the channel about 3 ft long and the width about 2 inches wider than the bezel. The curved channels can be made from foam core for easy bending and exterior out of plywood.

http://www.diyaudio.com/forums/full-range/247598-nautaloss-ref-monitor.html
 
I plugged in the parameters to a sealed box calculator and got something like 33L and 175hz...
Yes. That is with crossover frequency close to 200Hz.
You will have to bring up your crossover frequency as I said.
Then you will have to match the 2 woofers (output, phase and all) with the mains one for each channel/"satellite"/Lowther DX45. :D

I don't understand what you are using for your set-up for LFs. :confused:

Maybe you will explain, but in this case, I don't know what's up with the reflex?! Is it bad? You might have some aversion to it. I want to see how you are going to solve this problem. You have something (resolution?) up your sleeve. :cool:
 
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what I want is easy construction (so spiral tunnels are out) and less coloration (reflex design more or less has that).

Maybe I should just do a folded voigt pipe and call it good....

The coiled foam core actually is easy to construct. 4 hrs per box no power tools.

Anyhow, if it lying ooks hard, and you don't mind a 3 ft long dagger like speaker protruding out the back make a simple triangular tapered sealed TL. Same concept just un-coiled. 5 pieces of wood glued together to look a pyramidal dagger with the driver mounted at the base.
 
Hi,

A simple sealed box will do the job. 18L is way too much.

Why you think this is a good use of such a driver is beyond
me, I can think of many drivers that will do the job better.

Model the driver roll off in a box program. Qts of 0.3,
Vas of 4L and Fs of 80Hz points to a very small box.

2L is a Qbox of around 0.5, -3dB at 200Hz.

Nothing looks good to me for a low SPL system.

rgds, sreten.

FWIW I think Lowthers are overpriced, overrated tat.
 
It must be the "HALF-RANGE". :D :D
(OP) Do you have the drivers already or are you shopping still?!

When you are such a smouch to give it a try with a FR with range 200Hz and up. If the OP wants a FR for sealed enclosures he has other options (he didn't ask). But I have no idea of what he is doing or the drivers he is going to use. 2-Ways, subs, woofers, FRs, Half-Ranges, Horns, TL, sealed, extra volume sealed enclosures (why?), other, what...? If/in choosing a driver you need to know what that driver is capable of , and then to treat the back wave, to damp the enclosure and give it your best treatment.
 
I bought the lowthers mainly for more resolution and speed. I am mainly a headphone guy, more specifically a planar headphone guy (orthodynamic, electrostatics), so detail reproduction is critical, especially for low volume listening.

so DX45 it is... already have the drivers at hand.
 
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DX45 sealed sims.

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dave
 

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Thanks for the sim.

I suppose one way to do is level off at 100hz, bring the higher frequencies down by 16db (like a super baffle-step-comp). Instead of 93db/w sensitivity I will end up with something like 77db/w, which is not a problem for my situation.

But the whole point of using Lowther is fine detail reproduction, adding that much a filter will likely kill a lot of micro-details.
 
I bought the lowthers mainly for more resolution and speed. I am mainly a headphone guy, more specifically a planar headphone guy (orthodynamic, electrostatics), so detail reproduction is critical, especially for low volume listening.

so DX45 it is... already have the drivers at hand.

Hi,

The so called "resolution" and "speed" comes from the
quite appallingly inaccurate coloration of Lowther drivers.

Yes they are different to everything else. Fans think they
offer things no other drivers can, and they do. The simple
ability to convince yourself something that is wrong is right.

http://www.troelsgravesen.dk/Lowther.htm

The current Seas 8" full ranges are near the best
currently available, if you have to have an 8" FR,
and will work well in about 1cuft/28L sealed.

rgds, sreten.
 
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