Mark K's er18dxt

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#43
I am wondering... is the design baffle step corrected or not?

Yes it has full bsc, total efficiency is ~84dB. Output at 35hZ is ok but naturally the max bass output form a single 6.5" driver is limited. This speaker is practically "full range" at reasonable levels, most people will be amazed of the quality of bass when placed on stands and more than 2 feet from walls! My listening room is 4x6m (24m2 ~ 258ft2) with 2 open sides and Im quite happy even without a sub.

Her is Mark's page of his design
The Seas ER18DXT ported two way

Recommended!
Juhazi
 
#44
Thanks for the reply. I plan to "modify" the design to a CC, slim wall-mounted speaker to be used with a subwoofer. I suspect, from preliminary simulation with simulated driver and enclosure data that simply changing the ER18 inductor to 1.5mH will flatten out the BSC by about 2-3dB and the rest should be fine?!? What do you think?

Best
Leif
 
#47
Hi guys,

The bafflestep is somewhere around 3-4dB.
An ML TL would be a very nice variation. However, there would be some error without an xover mod. I don't have one of though MAD floorstanding cabinets or I'd be temped to try it.
It could be used 3 across as an HT setup. However, it's not quite right for that. For what it's worth I use what I consider a lesser design, my Usher 2 way 3 across and it's solid. But I'm not that critical about my HT system.

If you're doing a 2ch stereo optimized system that does double duty as an HT, it would work very well. It would not be a reference level system given it just has a single 7"
 
#48
leifislive said:
Thanks for the reply. I plan to "modify" the design to a CC, slim wall-mounted speaker to be used with a subwoofer. I suspect, from preliminary simulation with simulated driver and enclosure data that simply changing the ER18 inductor to 1.5mH will flatten out the BSC by about 2-3dB and the rest should be fine?!? What do you think?

Best
Leif
Click to expand...

Sorry I can't answer to that. Please email Mark himself, he is really helpful. You can find his email address at the bottom of his pages.
Juha

(Bsc might be 4dB (full is around 6dB), Mark doesn't tell it straight, but these are meant to be stand-mounted. Stuffing the box has a point!)
 
#51
marchel said:
Wouldn't it be better to place the drivers closer together to get better vertical response? Sorry I didn't read all the post and the project page.
Click to expand...


Well, this is always a tradeoff. The vertical lobing is slightly less desireable with a larger y-axis separation between drivers, but the diffraction signature of the woofer is a little less pronounced. Also, the tweeter is horizontally offset, so moving the tweeter closer to the woofer worsens the effective rotational offset, i.e. for the same horizontal offset, the tweeter is "rotated" over a bit more. (perhaps that isn't a good explanation, but you'll figure it out if you think about the tradeoff between the positive effect on baffle diffraction of a horizontal offset vs a worsening of the polar response). You could make the difference between drivers closer and decrease the horizontal offset, but then the diffraction is more pronounced. I'm not a big believer that this diffraction is audible. But, minimizing diffraction makes the design easier and the target more easy to achieve...

Add to that the xover frequency is lowish, 1.9k and, well, it's fine. I mean, it's all about tradeoffs, right...
 
#52
Thanks,

I now understand that this is about the trade-off between vertical response and the diffraction imposed by the mid-woofer when p[laced nearer the tweeter.

But how about making it into a reference level speaker by making it into a MTM to making it go louder, Aside from making the vertical response worst, What will be the the trade off involved ? Can I just adjust the XO component ( halving the inductor value, doubling the caps value and decreasing the resistor value). Will the tweeter handle the extra power and 6db increase in sensitivity?
 
#53
Mark thanks again for this great design. I have just started building a set and found a discrepancy on your parts list.

For the woofer crossover you show a 5.00uF capacitor on your schematic, but your Parts Express list it shows 5.1uF caps (those are the ones I purchased). Was there a design change?

Cheers, Joe
 
#60
RockLeeEV said:
:drool::drool::drool:
I wish there was an MTM TL tower of this... I want to build it so badly.
Click to expand...
I would prefer a TMM for the advantage in floor bounce cancellation that a low woofer could give. If I had another pair of the woofers, I'd probably do this.
azimut said:
I would be interested to make a center version of this project. I think that DXT looks promising for this use (and for a ht in general).
...what modification would be needed?
Click to expand...
Turn the speaker sideways.

🙂
 
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