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PostPosted: Thu Mar 02, 2017 1:02 am 
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Hello, this is my first post, I might've even been here before years ago (known about this place for awhile) but hard times sorta postponed all speaker upgrades.


My original plan for the moment was to build 5x Table Tuba long profile models (probably just with the MCM 8 - is there any point to a 10 on 100w?) for a home theater stacked up against the wall. I was probably going to build them slightly narrower than ideal sensitivity, but where 5 together was about the width of 4 ideal/widest ones.

Why 5? Wanting to use an older 5 channel home receiver amp as the sub amp which is equal power 100 watts per channel. Also planning to periodically pull 1 or 2 or 3 of the subs off the stack for use in vehicles. They might stay there a bit then when it's show off the home theater night all go back against the wall.


I was considering what an upgrade might look like and was thinking of 2 Tuba Home Theater again long profile, but then I was wondering... with how 4 subs (the TT stack is really like 5 drivers in a stack optimally efficient at 4 which is I thought how they were designed) boost sensitivity, would the THT's even outdo it with more power?


So that's my comparison - 500 watts into 5x Table Tuba, vs 1000 watts into 2x Tuba HT's. Which is going to have more total sensitivity, more total volume, and how does the low end vary? To me it seemed a 30hz 'knee' wasn't that dramatically different than a 25hz 'knee' for sub tuning but maybe it's a bigger difference in room than I think.


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PostPosted: Thu Mar 02, 2017 9:09 am 
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infrasound wrote:
My original plan for the moment was to build 5x Table Tuba long profile models (probably just with the MCM 8 - is there any point to a 10 on 100w?) for a home theater stacked up against the wall.
In a HT that's usually the worst possible placement. Two TT or THT are sufficient for most any room, and should be spread as far as possible for the best room response.


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PostPosted: Thu Mar 02, 2017 4:41 pm 
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Bill Fitzmaurice wrote:
infrasound wrote:
My original plan for the moment was to build 5x Table Tuba long profile models (probably just with the MCM 8 - is there any point to a 10 on 100w?) for a home theater stacked up against the wall.
In a HT that's usually the worst possible placement. Two TT or THT are sufficient for most any room, and should be spread as far as possible for the best room response.


I may not have freedom of placement - stacked up against the wall, with the mouths facing the corner and exciting all room modes equally, is what I thought I read was best anyways (corner first, against wall second, free air worst). I can't move it away from the wall I mean there isn't room to put subs anywhere. Although the home theater area is small, the room is large, it's one of those combined living room dining room kitchen bilevel layouts, the three powered 12's I have now just cannot give me anywhere near the levels I want. It's fine for mid level listening but THX would require about 17-20db hotter at least at frequencies I recognize, it runs out of gas on the bottom octave in addition, and I like my bass level better than THX if I can get it. Ideal is "just short of breaking my house" actually.


Irregardless of positioning in room, how does the output and low end response compare between the two options of two HT's on 1kw or 4-5 TT's on 500w? Would the two HT's even count as an upgrade? I've got PA mains fairly near field - clearly I like it pretty loud.


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PostPosted: Thu Mar 02, 2017 5:42 pm 
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The TT is a 30Hz horn, the THT is a 22Hz horn.


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PostPosted: Thu Mar 02, 2017 5:46 pm 
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infrasound wrote:
I may not have freedom of placement - stacked up against the wall, with the mouths facing the corner and exciting all room modes equally, is what I thought I read was best anyways (corner first, against wall second, free air worst).


Placement and loading is simply about maximising output.
If you corner load that adds +12db for free. Or, to put it another way, you don't have to build 4 cabs for the middle of the room, you build one and corner load it to get the same output as the 4 cabs.
So, decreased driver costs, less power, less build time.

That has nothing to do at all with room nodes.
If, regardless of where you place your sub, you end up with a null in various parts of any room, that is due to room modes. Adding another sub in another part of the room more often than not addresses room modes, it is not about increasing overall volume.

The best way to work out best sub positioning is to place a sub in the LP, and crawl around the room to find where the bass sounds loudest. That's where you place your sub. If that placement exhibits nulls with one cab, then, more often than not, another cab on the opposite wall will address those modes.
If that doesn't work out in real life about where your plan to place cabs, then you need to go back to the drawing board and make another plan...

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PostPosted: Fri Mar 03, 2017 2:07 am 
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Bill Fitzmaurice wrote:
The TT is a 30Hz horn, the THT is a 22Hz horn.



I guess i'll try without other distracting text, would two Tuba Home Theaters with 1000 watts play substantially louder and deeper than four-to-five Table Tubas on 500 watts (loaded with 8" MCM) along a wall firing into the same corner?


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PostPosted: Fri Mar 03, 2017 7:52 am 
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It doesn't matter if you have five or fifty 30Hz horns, they still won't go as low as one 22Hz horn.


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PostPosted: Sat Mar 04, 2017 5:19 am 
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Bill Fitzmaurice wrote:
It doesn't matter if you have five or fifty 30Hz horns, they still won't go as low as one 22Hz horn.


I feel like i'm a bit of a broken record and sorry if i'm sounding burdensome so let me explain my problem solving process. I'm looking at the charts here: viewtopic.php?f=12&t=953 I look at the map for the Table Tuba and i'm adding 6db - because I read somewhere else that when you doubled the speakers instead of getting 3db more, you get 6db more because the coupling of the larger horn mouths further improves sensitivity and low end extension. From notes I took from the past (possibly incorrect) the TT and THT couple horn mouths ideally in sets of four similar to LABhorns.

Twice the Table Tuba's looks to pretty closely match a single Tuba HT at 20hz. So four Table Tuba's should about equal two Tuba HT's for sensitivity and response at 20hz. Higher frequencies perhaps even more sensitivie for the Table Tubas. Obviously a single vs single is different but that wasn't what I was trying to compare.

Likewise for maximum output I wasn't sure either. Maximum output at 20hz with 1kw likely more for the two Tuba HT but at any higher frequency I was guessing the four Table Tuba at 500w because of greater efficiency coupling four horn mouths (a fully coupled stack of four) instead of just two (half the ideal stack/thought these were all designed to couple in sets of four). I'm saying four and five interchangeably because it's going to be five drivers in the ideal/widest figure for four cabs is all. Each cab approx 80% of the ideal max sensitivity width because that's about what lets me fit two in any of my cars. (full width ones wouldn't)


The reason i'm asking is because i'm trying to decide if dual THT's is that much of an upgrade from 5xTT. The 5xTT will be built anyways. Just varying how much time a few are spending time in vehicles vs all at home. Except at 20hz i'm guessing both will have pretty similar output at 30hz and above despite the power difference. Thus I was assuming I might need to literally plan for four Tuba HT's to have a noticible upgrade. (for content 30hz and up)


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PostPosted: Sat Mar 04, 2017 3:54 pm 
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infrasound, you are completely missing the point Bill and Grant are trying to explain to you. Unless your listening area is more than 56' by 56', it will not matter what sub you put in there, there will be room modes to overcome. You want to stick hard and fast about the loading, but in small rooms, the reflections wreak havoc on the sound, especially below 80Hz.

Take Grant's advice, and do the "subwoofer crawl" using your current sub(s). Find the 2 loudest spots, and put a sub in each spot, no matter where it might be. This will give you instant improvement. However, I would still recommend you build a pair of THT. Proper placement will get you most of the way there, volume-wise, and the THT will give you the response you're after.

We can only advise you on how to fix your sound. You must be willing to accept the recommendations and open your mind to change.

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I know money often seals the deal, but seriously, quality is an investment, not an expense... Grant Bunter
Accept the fact that airtight and well-braced are more important than pretty on the inside. Bill Fitzmaurice


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PostPosted: Sat Mar 04, 2017 5:52 pm 
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infrasound wrote:
Bill Fitzmaurice wrote:
It doesn't matter if you have five or fifty 30Hz horns, they still won't go as low as one 22Hz horn.


I feel like i'm a bit of a broken record and sorry if i'm sounding burdensome so let me explain my problem solving process. I'm looking at the charts here: viewtopic.php?f=12&t=953 I look at the map for the Table Tuba and i'm adding 6db - because I read somewhere else that when you doubled the speakers instead of getting 3db more, you get 6db more because the coupling of the larger horn mouths further improves sensitivity and low end extension. From notes I took from the past (possibly incorrect) the TT and THT couple horn mouths ideally in sets of four similar to LABhorns.

Twice the Table Tuba's looks to pretty closely match a single Tuba HT at 20hz. So four Table Tuba's should about equal two Tuba HT's for sensitivity and response at 20hz. Higher frequencies perhaps even more sensitivie for the Table Tubas. Obviously a single vs single is different but that wasn't what I was trying to compare.

Likewise for maximum output I wasn't sure either. Maximum output at 20hz with 1kw likely more for the two Tuba HT but at any higher frequency I was guessing the four Table Tuba at 500w because of greater efficiency coupling four horn mouths (a fully coupled stack of four) instead of just two (half the ideal stack/thought these were all designed to couple in sets of four). I'm saying four and five interchangeably because it's going to be five drivers in the ideal/widest figure for four cabs is all. Each cab approx 80% of the ideal max sensitivity width because that's about what lets me fit two in any of my cars. (full width ones wouldn't)


The reason i'm asking is because i'm trying to decide if dual THT's is that much of an upgrade from 5xTT. The 5xTT will be built anyways. Just varying how much time a few are spending time in vehicles vs all at home. Except at 20hz i'm guessing both will have pretty similar output at 30hz and above despite the power difference. Thus I was assuming I might need to literally plan for four Tuba HT's to have a noticible upgrade. (for content 30hz and up)


If you need to get to 20 Hz build some THT's.
300 watts is plenty of power for each 15" loaded THT.


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PostPosted: Sun Mar 05, 2017 11:51 am 
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DJPhatman wrote:
infrasound, you are completely missing the point Bill and Grant are trying to explain to you. Unless your listening area is more than 56' by 56', it will not matter what sub you put in there, there will be room modes to overcome. You want to stick hard and fast about the loading, but in small rooms, the reflections wreak havoc on the sound, especially below 80Hz.

Take Grant's advice, and do the "subwoofer crawl" using your current sub(s). Find the 2 loudest spots, and put a sub in each spot, no matter where it might be. This will give you instant improvement. However, I would still recommend you build a pair of THT. Proper placement will get you most of the way there, volume-wise, and the THT will give you the response you're after.

We can only advise you on how to fix your sound. You must be willing to accept the recommendations and open your mind to change.


Oh I understand room modes are going to dominate, and I think i'm about 40 feet on the one dimension FWIW/full house width. All i'm saying is that I don't have much subwoofer placement flexibility as it is. Furniture lines the wall entirely except in the corner where the theater is.

Being that as it is, i'm not unhappy with bass response at my couch at all. There are nulls if I walk the room but not where I sit in any obvious fashion at any obvious frequency. I'm pretty happy with placement! I've only wanting substantially more volume and extension.

I remain confused whether 2 THT LP's firing into the corner will be substantially louder than 4 TT LP's firing into the corner. :-/ If the only upgrade above 30hz for 4 TT's is 4 THT's is the question i've been trying to answer since the first post while staring at the sensitivity charts for both horns. Even at 20hz it's not clear when its 4x vs 2x.

Near as I can tell two THT is pretty close to four TT at both 20hz and 30hz, if it's within 3db then my answer is to save the money until I can build four THT properly.


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PostPosted: Sun Mar 05, 2017 2:02 pm 
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This chart is a one-to-one, nearly same width comparison. That steep drop below 30Hz on the Table Tuba will always be there, as it is a 30Hz horn. The wider THT, using a 15" driver, beats them all. The THT will take a LOT more power than the TT, and will give you lower response. The trade-off is the size. On the Low Profile version of each, it's 12" in length, TT is 60" long, THT is 72" long. 1 THT will not quite be as loud as 2 TT, but close. If you are going to do 4 THT, then :twisted: :twisted: :twisted: :twisted: :twisted:
'EFF YEAH, BABY!

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I know money often seals the deal, but seriously, quality is an investment, not an expense... Grant Bunter
Accept the fact that airtight and well-braced are more important than pretty on the inside. Bill Fitzmaurice


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PostPosted: Sun Mar 05, 2017 2:38 pm 
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infrasound wrote:

Why 5? Wanting to use an older 5 channel home receiver amp as the sub amp which is equal power 100 watts per channel. Also planning to periodically pull 1 or 2 or 3 of the subs off the stack for use in vehicles.



How are you planning on low passing the signal to the 5 channel receiver amp? You will only want speaker output from this amp from about 80 Hz down to 20 Hz. Does this older receiver amp even have stable output down to 20 Hz?

I tried using one channel of an older receiver 5 channel amp to put out a 25 Hz signal at 10 volts just for speaker break in . That amp got hot as heck after 10 minutes, then poof, smoke show, just trying to put out a 25 Hz signal at 10 volts.

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PostPosted: Sat Apr 15, 2017 12:44 am 
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Are you aware that most 5 channel amplifiers cannot put out anywhere near rated power at all 5 channels at the same time? And I mean even big names like Yamaha, Denon, or Pioneer? They are usually tested with TWO channels driven to rated power. If you don't believe me, look at the rated wattage on the actual power draw of the receiver, divide by 5, and then remember that even class D amps only get anywhere near 90% of that.


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