Is this how a Subwoofer Crossover is supposed to work?

kenjit, I sincerely hope to meet you one day.

Hello Pinwa,

Imo the close-miced curve of the Starke provides a lot of useful information. Now you can tell what was room interaction and what was native to the subwoofer, and it is much easier to tell what the crossover is doing. Good job!!

I think the close-miced curve on the Klipsh is giving you an incomplete and therefore misleading picture. From that curve I’d assume it has a port or passive radiator tuned to about 26 Hz.

If so, getting a representative frequency response curve becomes vastly more complicated. You ALSO need to close-mic the port or passive radiator and SPLICE that curve with the woofer’s curve, adjusting for the relative RADIATING AREAS of the woofer cone and the port or passive radiator. You also have to take into account the relative phase rotation between the two and I don’t know how to do that math - I’d have to use a computer program.

In other words, close-micing ONLY the woofer of a vented box DOES NOT give a complete and accurate representation of what the system is doing.

I suggest simply assuming that the Klipsch is competently designed, rather than doing more measurements plus a ton of math.

Also, pay attention to what geared4life is telling you. If his analysis is correct (and I think it is), your system configuration is not allowing you to adjust the level of the subwoofers with the same volume control that you are using for your main speakers.

Duke

The volume control that turns the sound to your speakers up and down must also be the one turning the sound to your subs up and down.

Bingo! And I already provided the simple $2 solution to getting exactly that from his existing amp.
https://www.epanorama.net/circuits/speaker_to_line.html

" Bingo! And I already provided the simple $2 solution to getting exactly that from his existing amp.

https://www.epanorama.net/circuits/speaker_to_line.html "   

Good call!!

Duke

1) So I’m not an idiot. Of course I’m setting the volume of the amplifier at a fixed level that approximates my 75 dB listening level and fine tuning volumes with the DAC that then controls what both the amp and the subs see.

2) If I wanted to spend $2-4K on subwoofers I would have, so all the suggestions about buying "audiophile" quality subs will be respectfully ignored.

3) The bass response on the Moabs is great which is absolutely not the same thing as saying the system wouldn’t benefit from well integrated subs. Here is a chart of the Moabs with and without a very old Velodyne CHT10 subwoofer with a speaker level input. As you can see that sub improves the measurements of the system as well as improving how it sounds. I wanted to see if the Starke’s improved things further although so far I’m not sure that is true.

https://www.dropbox.com/s/bf83tvl57i9l0qw/Moab%20with%20and%20without%20Subwoofer%2050Hz%20Crossover...

That REW graph of the Moabs shows a lot of weird stuff in the response above 200 Hz and that was because the Moabs weren't well positioned in the room when that measurement was taken. Where I have the Moabs now the frequency response is +- 5 dB from 100 Hz to 10 KHz except for a little bump around 325 Hz that might be the crossover.
   
All comments about how subwoofers don’t belong in my system will be respectfully ignored.

4) I didn’t think about the fact that the Klipsch was ported so I guess I’ll reserve judgement. Not planning on using that sub with the Moabs anyhow so I will do no further investigation there. And I’m not going to mess around with the Moab’s ports.

5) I need to do some further investigation about the pros and cons of a) leaving things as they are with the tube amp connected to the DAC’s RCA output and the Subs connected by XLR cables. b) using an RCA Y Splitter to connect subs and amp to the same RCA input. c) Millercarbon’s suggestion to adapt subs to a speaker level input. d) when I bought the subs Starke said you could connect one sub to RCA and use the subs balanced out to connect the second sub with an XLR cable. That sounds weird but I may give it a try rather than having multiple Y splitters.

I will note that there doesn’t seem to be any difference in the curve in the subs response when you switch from RCA to Balanced inputs so it isn’t clear to me why so many of you seem to think it is imperative the subs and the amp use the same input as long as volume is controlled further upstream, i.e. at the DAC level.

6) miniDSP looks interesting and perhaps I’ll get one later but not something I want to play around with right now.

Thanks to all of you who are providing detailed constructive comments.