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To add to what Jared already stated, I would recommend getting three additional pillows.
Here’s the close mic of Jared’s (now your) two cabs, along with mine loaded with two vertical pillows.

The vertical pillows seem to completely remove the rear chamber resonance at 110hz.
The port resonance at 140hz is unaffected, of course.

Here’s a (bad) pic of my pillow placement:

Chris
Thanks for the info. I'll look in to getting some more pillows. I was just planning on dropping them in like Jared did in post 427. Looks like his results with just one pillow match yours so hopefully just adding another pillow on top will smooth that right out.
 

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Thanks for the info. I'll look in to getting some more pillows. I was just planning on dropping them in like Jared did in post 427. Looks like his results with just one pillow match yours so hopefully just adding another pillow on top will smooth that right out.

Those are his results. I never tested mine without pillows.

I would suggest securing them at mid chamber vertically though. From my quad dev testing, that was most effective at reducing resonance without hurting the bottom end.

Chris
 

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Those are his results. I never tested mine without pillows.

I would suggest securing them at mid chamber vertically though. From my quad dev testing, that was most effective at reducing resonance without hurting the bottom end.

Chris
I need to start working on the tuning on my BMD Alphas. I got one fired up, and some basic MiniDSP work and love what I've heard so far; but need to get some pillows so I can start playing with things a bit more. Is there a certain size pillow you recommend?
 

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I need to start working on the tuning on my BMD Alphas. I got one fired up, and some basic MiniDSP work and love what I've heard so far; but need to get some pillows so I can start playing with things a bit more. Is there a certain size pillow you recommend?

Just the standard size.
I found the cheapest ones at wally world, and got the softest version.

Chris
 

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Just the standard size.
I found the cheapest ones at wally world, and got the softest version.

Chris
Aw man, I got the firm ones. Now it won't sound right! Lol
They did fit nice and tight so I didn't bother attaching them.


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Aw man, I got the firm ones. Now it won't sound right! Lol
They did fit nice and tight so I didn't bother attaching them.


Sent from my SM-G950U using Tapatalk

Firm pillows? Everything is ruined!

If you have a mic, you should take a close-mic sweep. I’m curious if they work as well like that as secured at half-height.

Chris
 

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Firm pillows? Everything is ruined!

If you have a mic, you should take a close-mic sweep. I’m curious if they work as well like that as secured at half-height.

Chris
I hope they do. I dont really want to open them back up. I'll try get a sweep soon.

Sent from my SM-G950U using Tapatalk
 

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Discussion Starter #551
Isn’t that resonance above crossover enough to not make or break the sub? Just askin...
 

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Isn’t that resonance above crossover enough to not make or break the sub? Just askin...

Yes and no. You have to remember that crossovers are not hard limits. Ideally you keep all nasty behavior a full octave above crossover frequency.

However, low tuned subwoofer boxes are very hard to achieve this due to port resonances. I consider a half octave to be worst case, and try to do better. That resonance at 110hz isn’t even a half octave above an 80hz crossover.

How noticeable it will be depends on the particular build, and the user.

Chris
 

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should be fine. Just needs to knock down standing waves.

My testing on the quad showed that placement does make a significant difference. I was surprised.

That said, I expect the current placement to be a major improvement. I’m just curious if it will still show the resonance or not.

Chris
 

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Discussion Starter #554
Yes and no. You have to remember that crossovers are not hard limits. Ideally you keep all nasty behavior a full octave above crossover frequency.

However, low tuned subwoofer boxes are very hard to achieve this due to port resonances. I consider a half octave to be worst case, and try to do better. That resonance at 110hz isn’t even a half octave above an 80hz crossover.

How noticeable it will be depends on the particular build, and the user.

Chris

Got cha. Yeah I’m just sayin I never heard anything nasty sounding coming from either Alpha. Hence the reason I even forgot I only had one pillow in one of them.
 

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Got cha. Yeah I’m just sayin I never heard anything nasty sounding coming from either Alpha. Hence the reason I even forgot I only had one pillow in one of them.

You may have had a bit of other sound happening as well. Your house was likely making worse “distortion”.

Chris
 

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See the attached picture for where I put my WalMart pillows in the Quad Dev. They are down lower, secured to the lower 2x4 braces, and the misplaced 2" tall port board on the top of the port board (OOPS).

I put the first pair of port boards on the wrong way, fortunately they didn't get in the way and I was able to flip the port board over and put another pair of boards the correct way on the other side.

I will say I searched Amazon for pillows and wasn't able to find anything for less than $10 that met the requirements. Ended up convincing my wife to pick up the pair of them during a food shopping trip she was making.

I have also attached the closemic I did with those pillows in those locations. My eyes see the lower location as being pretty good, but there are actual experts here.
 

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Discussion Starter #557
@Jedi940 feel free to give us constant updates in this thread! Lol
For real though, I’m dying to know what you think of the Alphas in your system.
 

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@Jedi940 feel free to give us constant updates in this thread! Lol
For real though, I’m dying to know what you think of the Alphas in your system.
I will definitely update this thread. Unfortunately, I don't have much to say right now. I got the alphas primed, painted, and moved in behind the screen but that's about it. I did some initial testing with the inuke that was previously hooked up to my B&C's but that's about it. It definitely worked well and despite me taking it easy as I didn't have an HPF set, I still managed to knock a picture off the wall upstairs so I have high hopes for this with the clone. Additionally, I am considering plugging one of the ports and trying to drop the tune. My B&Cs are around 18.5 hz so I'm thinking of I plug one of the 3 ports on that as well, both may end up around 16hz which would help me dig deeper and possible negate my need for the 4 SI HT18s sealed for the low end. Although I probably don't see me getting rid of them :D When plugging the ports on the alphas, do you just plug the rear chamber?

I have been struggling to figure out what to do with the clone. I do not have a dedicated space for my theater. It is currently occupying a wall in the basement. As such, there are no good options for running a 30 amp outlet. I thought about just moving that amp to the unfinished side and running some longer wires, however the MiniDSP would have to move too and running RCA cables that distance didn't seem like a good idea. I also thought about converting it to 220 and using a somewhat nearby outlet but that would put the amp on the floor off to the side and require moving it everytime I wanted to use it. Additionally, it would still be audible while watching a movie.

The final solution was to make use of the rack I have had for quite some time in anticipation of using it in a dedicated theater some day. This required doing some cleaning and organizing all weekend in order to move the rack into position. That part is now done. Next comes moving all the equipment and re-wiring the entire 7.8.4 system as well as installing the new 30 amp outlet :(

On a side note, anyone need some reading material?
 

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Discussion Starter #559
I will definitely update this thread. Unfortunately, I don't have much to say right now. I got the alphas primed, painted, and moved in behind the screen but that's about it. I did some initial testing with the inuke that was previously hooked up to my B&C's but that's about it. It definitely worked well and despite me taking it easy as I didn't have an HPF set, I still managed to knock a picture off the wall upstairs so I have high hopes for this with the clone. Additionally, I am considering plugging one of the ports and trying to drop the tune. My B&Cs are around 18.5 hz so I'm thinking of I plug one of the 3 ports on that as well, both may end up around 16hz which would help me dig deeper and possible negate my need for the 4 SI HT18s sealed for the low end. Although I probably don't see me getting rid of them :D When plugging the ports on the alphas, do you just plug the rear chamber?

I have been struggling to figure out what to do with the clone. I do not have a dedicated space for my theater. It is currently occupying a wall in the basement. As such, there are no good options for running a 30 amp outlet. I thought about just moving that amp to the unfinished side and running some longer wires, however the MiniDSP would have to move too and running RCA cables that distance didn't seem like a good idea. I also thought about converting it to 220 and using a somewhat nearby outlet but that would put the amp on the floor off to the side and require moving it everytime I wanted to use it. Additionally, it would still be audible while watching a movie.

The final solution was to make use of the rack I have had for quite some time in anticipation of using it in a dedicated theater some day. This required doing some cleaning and organizing all weekend in order to move the rack into position. That part is now done. Next comes moving all the equipment and re-wiring the entire 7.8.4 system as well as installing the new 30 amp outlet :(

On a side note, anyone need some reading material?

Lol that picture that fell off the wall had it coming! Wait till you really unleash them!
Yes only plug a rear chamber port. There are measurements out there with one port plugged. It looked good to me. You won’t miss any output and the lower tune will rock. Man you gotta port those nearfield subs! Or turn them into a boss platform. Just two of them ported will kill the 4 sealed. From tune up. You know all this. I’m just trying to get you to do it. Lol
 
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