Lambda driver-based sub build.

[Brett a]

And what if the room is asymmetrical?

The speakers on the right near the door to the foyer have a very different environment than the left. It'll be interesting to get both subs and see how asymmetrical their positioning ends up being.

(the 11' 6" is the distance from my head to the plane of the speakers. The room's dimentions are in the right margin.)

 

[dumptruck]

Gosh, I'm not sure. That's not asymmetrical enough to make much difference for the bass, but there aren't a lot of options available and you're sitting pretty close to the back. I'd still try the side wall centers unless the window and/or CD rack nixes that. I'd try nearfield behind the couch corners if they can cram in there.. maybe one on the left side of the chair and one by the right speaker with the polarity reversed on one...

 

[dnewma04]

I think all of the positioning are just general guidelines. The more subs you add, the less critical the positioning becomes.

I think I'd be tempted to corner load one in the front right corner and have it handle the deepest bass. Then run the other at a reduced level next to the chair on the left as a starting point.

 

[ofajen]

Q would be 0.9+, but with heavy fill (which seems to be included automatically by Brett's sim program) it should get close to 0.7. You gonna put the amp in one of the sub boxes or its own box?

I concur that Q would nominally be about 0.93 at 91 liters. How do you figure heavy fill gets to 0.7? My references say the practical "effective volume" increase of heavy fill is at most 20% which gets to about 0.88 at 109 liters.

Cheers,

Otto

 

[dumptruck]

I concur that Q would nominally be about 0.93 at 91 liters. How do you figure heavy fill gets to 0.7? My references say the practical "effective volume" increase of heavy fill is at most 20% which gets to about 0.88 at 109 liters.

Well, I said "close to", and I only figure it the lazy sim way. In my experience, setting the WinISD Qa parameter (absorption loss) to 5 matches well with measured results for heavily filled boxes. In this case, it spits out 0.765.

 

[dumptruck]

Maybe part of the confusion is that the Q drops relatively quickly to match that of much larger enclosures as you add stuffing, while bass extension only increases a little bit, if at all. I think the 20% rule of thumb may be referring to bass extension.

 

[dnewma04]

20% is the effective increase in size. And it's not really constant. In smaller enclosures it tends to be less effective than in large enclosures. I've had effective increases in 5-6 cu ft enclosures of 30-35%. In small enclosures, I haven't seen nearly the impact.

 

[dumptruck]

But how are you judging "effective increase"? Q? F3? F10? Impedance? I don't think it's possible to get everything to match a larger enclosure, ever.

 

[dnewma04]

Impedance peak measurement. I'm not sure if it's the right way but I've seen it done this way and it's how I handled it in the past.

 

[RayW]

That would be an indirect measure of Q. Seems as reasonable as any other measure to me.

 

[dumptruck]

To rephrase what I was trying to say in impedance terms, I think if the center of the impedance peak matches what you'd see in a larger enclosure, the magnitude of the peak will be lower than in the larger enclosure.

 

[nexus]

first time i used a sub i thought it was not working. especially in the days of vinyl and especially pop/rock records there is no bass really at subsonic frequencies. back in those days the cutting engineer would throw a fit if you delivered a master with sub bass. the order of the day was for the cutting engineer to roll off everything below 50hz. i know, i worked in (and hung-out too!) studios in the 70's.

so i was thinking there was no action from my sub until i listened to a RtoR dub from a friend's master tape of electronic music and the sub sprang to life!

i would take all the advice here and reserve judgment until you get both subs in the room. then look into EQ. most all commercial subs sealed or not employ some eq. some of them A LOT.

back in the day i heard a demo of the NLA with some eq for the low bass and it was quite a difference.

Allison made an eq box called "the electronic subwoofer" for AS speakers. there are others too.

 

[budgetaudio6]

Considering your sub is 500 plus watts, try dialling it at around 7 % of gain. My velodyne gets over powering at anything close to 10 %. Even when using cerwin Vegas. You hear it but cant tell its coming from the sub. The M&K are an extra icing on the cake as they play to around 20 hz and are sealed.

With such small speakers you may be using too much gain. Another good way to adjust the gain of the sub is to add an inline eq. They dont affect the lowest frequencies like tehy do the upper frequencies.

 

[donprice]

A proper subwoofer will hide in the corner silently until called upon to destroy the silly knick-knacks you always hated. You just need the right signal to release the beast...

As hinted at above, find some "modern" rock tracks with significant LF content. I assume you can find the last 3 or 4 Rush albums (or whatever you call them now) so try tack 6 (The Main Monkey Business) from Snakes & Arrows (2007) and track 4 (the Anarchist) from Clockwork Angles (2012?). Turn them up to between 9 & 11 and you should find some signal to make your subwoofers obvious. Of course there are a thousand other tunes with similar LFE content...most of which you may not care to listen to.

 

[Brett a]

Thanks for all the help and guidance so far everyone.

I was able to spend some time in the last 24 hours trying different positions. (I still just have the one cab)

After trying it front-and-center (1.)
I tried it to the left of the sidechair between it and the couch where the Rek-O-Kut usually sits (2.)
I tried in the front right corner (back to the bass trap) (3.)
And I tried over on the right wall, next to the door to the foyer, firing across the room in front of and perpendicular to the mains. (4.)


None of these really worked well; the bass was muddy and disconnected. Where I have had the best luck so far is midway up the left wall on the right side of the chair. (5.)

With this placement, I run the amp setting with the X-over all the way down (40hz) and the gain at about 10 o'clock. I checked the phase setting by reversing polarity on both mains and playing a 40hz tone. I then rotated the phase knob until I heard the least amount of bass. Then returned the speaker connections to their proper polarity. (I learned this trick by reading Robert Harley)

Listening to a Thelonious Monk LP I am very familiar with (THELONIOUS MONK "THE BEST OF" RIVERSIDE RS 3037 which is mostly taken from the Riverside live album Misterioso) , I found the addition of the sub not only provided weight and scale to the string bass and paino, it also surprisingly went a lot further in recreating the room the band was playing in which must have been a club, b/c you can hear people talking, glasses clinking, and at one point, the phone ringing. Adding the sub made all this more real and 3 dimensional. It brought my system one notch further to truly transparent inasmuch as it is able to transport a listener to the original setting to a very pleasing degree.

This was last night. And I did all those placement trials this morning. So I'm going to have to spend some time getting it tuned in again since returning it to that spot.

Thanks again everyone for all your help so far.

:thmbsp:

I think I'd be tempted to corner load one in the front right corner and have it handle the deepest bass. Then run the other at a reduced level next to the chair on the left as a starting point.

(...)there aren't a lot of options available and you're sitting pretty close to the back. I'd still try the side wall centers unless the window and/or CD rack nixes that. I'd try nearfield behind the couch corners if they can cram in there.. maybe one on the left side of the chair and one by the right speaker with the polarity reversed on one...

 

[Brett a]

I hope to finish the second cabinet tonight. I'd like to put a volume pot on it so I can turn it down independent of the other. This would give me some controlability b/c the two cabs are likely to end up in different surroundings.

Does this seem reasonable? And can I get a pot like that at RatShack? I assume I'd have to look for one designed to handle speaker-level voltage, right?

 

[iamdgw]

I can see it now...

"Hey, why is that table cloth vibrating? - and how are getting such good low end from those tiny speakers "

 

[dumptruck]

There is no good way to turn one down without getting a second amp. Series resistance will mess up your response, so you're talking L-pad, not pot, and two 250W resistors will cost nearly as much as a plate amp. I suppose you could use a transformer, but that's equally impractical. I think you can probably get by without that ability, though.

 

[Brett a]

There is no good way to turn one down without getting a second amp. Series resistance will mess up your response, so you're talking L-pad, not pot, and two 250W resistors will cost nearly as much as a plate amp. I suppose you could use a transformer, but that's equally impractical. I think you can probably get by without that ability, though.

Thanks. I can work just with placement then. There's a good chance I may end up with a second plate amp eventually, but right now, I need to let my debit card cool down.

 

[Brett a]

So, I've got them both home and finished. So far, it's not looking hopeful for getting one to blend well on the right hand wall.

What I have come to realize though is that I need to add more bracing. I'm getting a monotonous drone (kind of an undertone of "sameness").

So I'll add more bracing and maybe consider buying some Dynamat or similar.

And I will leave plenty of room around every sentence that I type.

I'm taking this week off from work, so I should have it dialed in before too long.

I'll keep ya'll posted.