Adding an MBM (mid bass module) to your DIY Sound Group speakers - Page 2 - AVS Forum | Home Theater Discussions And Reviews
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post #31 of 259 Old 03-31-2015, 02:54 PM
 
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The 40hz things isn't to cross at 40hz. Notice on the graph 40hz is about 10db down. What if someones room dictates a 60hz XO and the sub were 18db down at 40hz. It's less likely to work well as a 60hz XO. And if running them full range, the larger box will help. I'm offering solutions that are broad and work for anybody. If your room requires a 100hz XO then you probably don't need a 15" MBM, a 10" would be sufficient. Also consider that adding an MBM will help with room acoustics in the dreaded 80 to 100hz region and allow for a lower XO. If a lower sub cross over works, then I would use it if all else equal and if using a capable MBM (lots of "ifs" there).

The JBL 2226 is a great driver, but not MBM friendly. Personally, the way kingpin is using it is IMO the best application for it. 60-600hz, massive output, no concern for size or price. But hey, I solid measurement of yours in your box would be welcome and appreciated.
Yup you are are right. I'm just playing practical, or devil's advocate. But the 2226 specifically like a big ported box, so I agree there. And- I am all for extra capability so I agree there too. But practicality probably says that most MBM don't need to extend to 40hz.
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post #32 of 259 Old 03-31-2015, 03:01 PM - Thread Starter
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But practicality probably says that most MBM don't need to extend to 40hz.
Well I guess we disagree there.
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post #33 of 259 Old 03-31-2015, 11:28 PM
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None that I've used personally. If you really wanted to go that route I could give a recommendation based on simulations and general awareness. Let me know if you do.

Most of my thoughts have leaned towards a cost effective approach and smallish size. If a driver isn't playing above 300hz it doesn't need to be fancy to work well.

Honestly I don't know what is the best way to acquire what I'm after. By that I mean, separate modules or more capable mains. For instance, would the fusion 15 kick out enough to get what I am after or would the 12 inchers you suggested earlier be better?
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post #34 of 259 Old 04-01-2015, 05:19 AM
 
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Honestly I don't know what is the best way to acquire what I'm after. By that I mean, separate modules or more capable mains. For instance, would the fusion 15 kick out enough to get what I am after or would the 12 inchers you suggested earlier be better?
What are you after ?
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post #35 of 259 Old 04-01-2015, 05:34 AM
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What are you after ?

That kick in the chest feel you get when the drum hits and your near enough to the stage to feel it I don't need a lot of it, just want to feel it though.

I have an orbit shifter that does all sorts of loud and vibration all over the room and my clothes and the couch, but it's not that same feeling I'm looking for.

I was told to try my os crossed over at 120 but I just haven't had the time yet.
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post #36 of 259 Old 04-01-2015, 05:47 AM
 
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I would try the higher cross. Have you measured to see what's going on ? Usually it's room related, like you have or are sitting in a null. Goes back to the point I made earlier about crossovers should be based on room, and not just 80hz. A higher crossover might help you, but also you might have a big dip or something from your room going on too. Sometimes adding a new driver and location can fix things so a MBM might help, but it's kind of like going fishing using depth charges. You might only need a hook.
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post #37 of 259 Old 04-01-2015, 06:28 AM
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I think you might have also missed the point about the woofer being close to the floor to eliminate some of the usual suckout we see in the 80-150hz region caused by either floor bounce or rear wall interaction. The MBM might be able to help with this, but in room measurements would help. Yes, the fusion 15 would definitely give you the output you desire, but that doesn't matter if you have destuctive interference in the bass region causing a null.
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post #38 of 259 Old 04-01-2015, 08:31 AM - Thread Starter
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Exactly, you don't need an 18" to give you that, but you do need the frequency response which your room may be robbing from you. That a big part of what these MBMs are about.

What are your LCR speakers?
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post #39 of 259 Old 04-01-2015, 02:35 PM
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Close to the floor? Does the mouth of the horn being close to the floor count?

I haven't had time to re-measure or do much of anything setup-wise for the past few weeks but I'll definitely give it a go as soon as I can.

Are you guys saying that the fusion 15 v2 is very mid-bass capable?

Right now my lcr's are just plain old polk monitor 70s. I can't seem to commit to what LCR I want to go with. I definitely would love to keep it simple by getting mains capable of lots of mid-bass output, but if that's not possible I wouldn't have any problems with smaller mains and adding mbm's to the mix.
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post #40 of 259 Old 04-01-2015, 02:46 PM
 
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Close to the floor? Does the mouth of the horn being close to the floor count?

I haven't had time to re-measure or do much of anything setup-wise for the past few weeks but I'll definitely give it a go as soon as I can.

Are you guys saying that the fusion 15 v2 is very mid-bass capable?

Right now my lcr's are just plain old polk monitor 70s. I can't seem to commit to what LCR I want to go with. I definitely would love to keep it simple by getting mains capable of lots of mid-bass output, but if that's not possible I wouldn't have any problems with smaller mains and adding mbm's to the mix.
FUSION 15 is a 15" woofer and ported so yeah it's plenty capable. Even at loud levels. If you prefer a heavy midbass flavor you can probably get away with a little EQ. Orbit SHifter is a proper sub too- you should have plenty. My guess is it's a room thing. Bass in the midbass bands is almost always a room thing. One step forward it's loud. One step back it's gone. Is it a wizard? No it's the room.
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post #41 of 259 Old 04-01-2015, 03:18 PM
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FUSION 15 is a 15" woofer and ported so yeah it's plenty capable. Even at loud levels. If you prefer a heavy midbass flavor you can probably get away with a little EQ. Orbit SHifter is a proper sub too- you should have plenty. My guess is it's a room thing. Bass in the midbass bands is almost always a room thing. One step forward it's loud. One step back it's gone. Is it a wizard? No it's the room.

Yea it sucks cause I can't find it anywhere in my room by null, you guys aren't referring to the dip I get at the xo point right? That dip seems to move with the xo point I select, but it seems to get better when I choose higher xo points.
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post #42 of 259 Old 04-01-2015, 03:38 PM - Thread Starter
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If you have a dip at the XO that changes with the XO point you likely need to reverse the polarity of either your sub or mains. Usually it's done on the sub or by using the distance setting in your AVR. I bet you could get a lot of mid bass back just from a simple phase alignment tweak like that.
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post #43 of 259 Old 04-01-2015, 03:48 PM
 
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Yea it sucks cause I can't find it anywhere in my room by null, you guys aren't referring to the dip I get at the xo point right? That dip seems to move with the xo point I select, but it seems to get better when I choose higher xo points.
null is actually usually caused by room. Every room has them. The bass waves are larger than your room, and depending on the length and size of your walls, floor and ceiling you should have corresponding room effects. The midbass region is where these room interactions are most easily seen and usually most troublesome. Very low bass, and highs and mids are much less effected. So a lot of people who lack midbass lack it because of where they sit, or the set up. Try moving around the room and listening see if the bass gets weaker or stronger...
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post #44 of 259 Old 04-01-2015, 07:01 PM - Thread Starter
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Mfusick, he said it's everywhere in his room and follows the XO. This is a text book phase problem, not a room problem.
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post #45 of 259 Old 04-02-2015, 12:01 AM
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Originally Posted by tuxedocivic View Post
If you have a dip at the XO that changes with the XO point you likely need to reverse the polarity of either your sub or mains. Usually it's done on the sub or by using the distance setting in your AVR. I bet you could get a lot of mid bass back just from a simple phase alignment tweak like that.

Awesome thanks! So just tweak distance setting on my sub via minidsp? I think I tried doing just a little of that one time and I did see that the dip started to go away. Unfortunately I ran out of tweaking time and haven't done anything with it since.
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post #46 of 259 Old 04-02-2015, 06:30 AM - Thread Starter
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Yup. You can also use the polarity flip to get more 'distance'. Distance is phase/delay basically.
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post #47 of 259 Old 04-02-2015, 06:58 AM
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I also used the Sub Distance setting to bring up the dip at XO, and it worked like a charm.
Got that info from an old Mark Seaton post, tried it, and it worked.

Why waste $ on more cheap stuff, it's like challenging a dragon with a pocket knife.
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post #48 of 259 Old 04-14-2015, 10:13 PM
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Tux can you explain a little more how this helps work around issues with the room? If you recall from the 1099 thread, I seem to have a room issue with my 1099s in which the AVR tries to cross them at 250Hz for the L/R and 150Hz for the C. So far I don't have a definitive root cause, but it looks like it is caused because the room is not treated. I have been looking into DIY panels, but if this is an alternative to consider in addition I would like to understand better how adding some MBMs might help.

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post #49 of 259 Old 04-15-2015, 01:23 PM - Thread Starter
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Your best bet would be to get some measurements. Something is causing those speakers to seem weak for the audessay microphone. But that's not your question.

A lot of room issues occur due to the floor and ceiling. Both of which are hard to treat AND hard to change distance. If the rear wall causes and issue you can move the speaker back and forth to get a good result. But moving a speaker up and down is not applicable. Neither is a giant diffuser or absorption panel on the floor. By placing a woofer near to the floor we can keep all affected frequencies in the woofer where it'll couple to the floor rather than cause an issue. The as the frequencies increase we can cross over to the main speaker. At this point the frequencies are in the 250hz range and are less and less affected by the floor or ceiling.

The 1099 is already fairly good at this because it has two wide MTM woofers. But not perfect. I'd encourage you to check everything out before spending big bucks on MBMs. It's hard to screw up the low frequencies in the 1099 XO, but still can be. I think you did the battery test, so that's not it. Do you have a multimeter to check resistance? If it's not the speaker then your room must have a big suck out between 100 and 200 hz to make it appear small to the AVR.

Hope the explains things ok and you get through this.
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post #50 of 259 Old 04-18-2015, 03:54 PM
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Looks like the celestion is sold out.

Any others that work well in a sealed box?
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post #51 of 259 Old 04-18-2015, 09:51 PM - Thread Starter
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What size range are you hoping for? I'm almost done texting the PA255-8 and it works good sealed. But it's a 10"
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post #52 of 259 Old 04-19-2015, 06:10 AM
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I'm open to a 10... Look forward to your post
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post #53 of 259 Old 04-19-2015, 07:19 AM
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Tux, I could make up some midbass modules with that monster 12" woofer that is getting used in the Maximus-12. At one point you mentioned they would do very well, but we haven't talked about them very much.

What enclosure shape do you guys want to see?

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post #54 of 259 Old 04-19-2015, 07:37 AM
 
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Tux, I could make up some midbass modules with that monster 12" woofer that is getting used in the Maximus-12. At one point you mentioned they would do very well, but we haven't talked about them very much.

What enclosure shape do you guys want to see?
Golden Ratio ?
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post #55 of 259 Old 04-19-2015, 08:17 AM - Thread Starter
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Ya that one is on my list to add here. I played with the TS when you first got it and to be honest, it's the most MBM suited woofer I've ever modeled. Quite stellar. Depending on your driver price it could basically make any other choice senseless.
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post #56 of 259 Old 04-19-2015, 08:19 AM - Thread Starter
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Golden ratio is the best, but might not be of a benefit in the MB range, and it can make for an awkward size. I'd suggest a width that matches some of the existing diysg designs. The height and location of the woofer I'd want to dictate because it affects how to integrate the mains. Then the depth would be the final dimension to get the required Vb.
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post #57 of 259 Old 04-19-2015, 08:34 AM
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Quote:
Originally Posted by tuxedocivic View Post
Ya that one is on my list to add here. I played with the TS when you first got it and to be honest, it's the most MBM suited woofer I've ever modeled. Quite stellar. Depending on your driver price it could basically make any other choice senseless.
Well it was specifically designed to be used as a midbass monster in a 3-way speaker, so that's good to hear.

I'm ready to roll them out, but would like to have a good design. Maybe a slot port versus Precision Port for now.

What do you think about using Baltic birch on these?

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post #58 of 259 Old 04-19-2015, 09:12 AM - Thread Starter
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Whether BB or MDF doesn't matter to me, more what other people would want.

Slot port is always best IMO.
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post #59 of 259 Old 04-19-2015, 09:35 AM
 
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You'd probably want to consider port compression on a MBM design.
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post #60 of 259 Old 04-19-2015, 09:39 AM
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Why are the mbms being made ported?

Aren't sealed just as good in these frequencies?
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