TMM 2.5 way with digital crossover

[sqlkev]

I'm using this project by Tony Gee as a reference/guide

http://www.humblehomemadehifi.com/Auriga.html

But, instead of the passive crossover, I'm going digital.
As I understand it, Tony used 2 separate chambers for the woofers, one up top being closed, and the bottom being bass reflex.
What would be the disadvantage if I went with common chamber? (Already made the cabinets, can't change now)
Do I design the box tuned to 2 woofers?

As far as crossover goes, should I treat a 2.5 as full 3 way with my digital crossover? (I can't see there's any alternative)
the tweeter will be highpassed at around 3k up to 3.5khz
the midwoofer will be bandpassed at tuned frequency - 3khz

for the bottom woofer and the midwoofer integration, this is where I have trouble with. Tony decided to use 1st order filter to integrate with the midwoofer, but where is the best spot? I guess this is where I have to experiment?

I have the dcx and the deq to do the processing, also have the mic to do measurements.


Edit:

one more question,
how should I do the center spacing between the two woofers?

[sqlkev]

after a night of tuning, the TMM 2.5 project turns out to be decent

the drivers being used are the vifa xt19 crossed at 3.0khz and still tweaking
the midwoofers are the dayton da175 with the xover points of 400hz and 3.0khz
the enclosure is 2.5cube tuned to 27hz

so far, I like the depth of the soundstage compare to my MTM dipole (dayton reference and seas), sometimes the width also surprises me. Another thing I like about it is: the wider sweet spot, probably due to the excellent off axis reponse of the xt19 tweeter and the inherent TMM design.

things I don't like so far, the midrange on the da715 is nowhere near its reference brother. With the same setup, time alignment and auto phase alignment, the TMM setup somehow isn't as pinpoint as the MTM setup.


Another question if anyone is reading,
my DEQ and DCX goes crazy with clipping with certain discs, what can I do to lower the input level? (my dvd optical --> deq optical in ---> dcx aes/ebu in --> amps)
I've looked at almost every menu on the deq and couldn't find anything. HELP!!!

[sreten]

Hi,

there is no fundamental disadvantage with using a single chamber.

However the internal volume needs to be somewhat larger than the dual chamber.

Firstly it needs to be 25% larger because it needs to be 2 x reflex chamber volume.

Secondly it needs to be larger still because the combination of sealed and reflex allows
the reflex alignment to be somewhat lively, which may be too much for both reflexed.

As you've already built the cabinets, whats the internal volume ?

The first order on the lower unit is used for BSC, the c/o point is determined
by the baffle width. Digitally you can use a very overdamped higher order filter.
That is a filter that looks first order up to say 1kHz, but higher eventual slope.


/sreten.

[agrobler]

One often doesn't hear floor and ceiling bounce in the uppermid from MTM due to directivity, which helps pinpoint imaging, due to the less interference... Try damping the first reflection points, if only temporarily, to see if that's it, the loss of midrange detail also plays a part.

On the other hand the soundstage would probably tend to be larger with the TMM's

[sqlkev]

Originally posted by sreten
Hi,

there is no fundamental disadvantage with using a single chamber.

However the internal volume needs to be somewhat larger than the dual chamber.

Firstly it needs to be 25% larger because it needs to be 2 x reflex chamber volume.

Secondly it needs to be larger still because the combination of sealed and reflex allows
the reflex alignment to be somewhat lively, which may be too much for both reflexed.

As you've already built the cabinets, whats the internal volume ?

The first order on the lower unit is used for BSC, the c/o point is determined
by the baffle width. Digitally you can use a very overdamped higher order filter.
That is a filter that looks first order up to say 1kHz, but higher eventual slope.


/sreten.

My baffle width is about 11", but the edges are beveld 45 degrees, so it's about 10.25" right now.

The total internal volume is about 2.5cube. As I model up the drivers in Bassbox Pro, the fb is around 27hz and f3 of about 20hz.

The xo points right now are:
400hz 1st order for the lower woofer down to 27hz
2.51khz 4th order down to 27hz for the mid woofer
2.51khz and up for the tweeter

With time alignment and auto phase alignment on each channel, the stage is not as accurate as I want it to be. I'm not sure what else is there for me to do.

The bass is a bit shy as well, it's so difficult to blend the two woofers together, maybe another xo point on the lower woofer?

I've tried the auto eq with the deq and it still somehow doesn't sound right compared to the dipole setup.

I guess I'm gonna go back to the dipole setup after a week or so if i cant get this right.

[sqlkev]

After some more tuning, I disabled the phase/polarity auto adjustments and the bass comes alive,
I also changed the steeper xover slopes on the tweeter to second order now it's at 3.25khz, it's much smoother now. The tweeter and the midwoofer blends in nicely.

I'll need to order some cabinet feet to see if it helps with the imaging a bit. Will post some pics later on tonight.

[Cal Weldon]

Good news

[jleaman]

These were going to be something i was going to build, but i didn't..