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Old 15th September 2012, 12:38 PM   #101
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Quote:
Originally Posted by Toaster View Post
Oh, and if you are using sealed subs, no real need for two 15"s, I'd've thought.
The reason for dual woofers is not for extended bass response, but for effortless tight clean dynamic sound
You honestly don't get that with a single woofer.

Wait till you hear a drum solo with 2 x 15 in open baffle, you will freak out
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Old 15th September 2012, 01:12 PM   #102
Toaster is offline Toaster  United Kingdom
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Well, I have heard that kind of comparison Melon Head, and my experience is that it is a difference of degree, not kind. Also, it really will depend how low the OB is going as to how much difference there is. How much space needs to be filled and how loud it needs to be are also significant factors. While I have no doubt you've got a lot of experience with this stuff, I would gently note that I've also been at this for a while, building speakers of various kinds for over thirty years now- not that that is any guarantee of competence of course! Not that I disagree with the basic idea that more area/ displacement is generally a good thing, but two 15s does seem like overkill if sealed subs are in the mix too! Again, horses for courses. More drive units and higher sensitivity are usually good, all else being equal, but there are practical, financial and aesthetic costs to be borne! As far as the GRs are concerned Silent, check out GR Research. there's also a GR forum on AudioCircle.com. You could also look out stuff on the web about the GR Research V-1 and Super V speakers, which incorporate the GR OB sub. No connection with the company, and I haven't built mine yet, but it is an option worth investigating.

Last edited by Toaster; 15th September 2012 at 01:16 PM.
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Old 15th September 2012, 01:24 PM   #103
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Screamer ... what sort of xo slopes are you using mid/tweeter? Will your DSP allow asymmetric slopes? Sometimes too sharp a cutoff in the midrange .. on both ends ... takes better FR off the table. ...and a guy might experiment with separating the slopes a little depending on how the strong (in SPL variations) the upper xo point end up being.

Saying this cause I noticed that you're considering adding more drivers into the project and you might not have to. Adding additional drivers brings along other issues that you may not be able to work out ... like lobing problems for one. Walking around the room and having various parts of the FR attenuated and boosted isn't ideal. EQ won't help one bit.
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Old 15th September 2012, 01:37 PM   #104
evanc is offline evanc  United States
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Quote:
Originally Posted by Melon Head View Post
The reason for dual woofers is not for extended bass response, but for effortless tight clean dynamic sound
You honestly don't get that with a single woofer.

Wait till you hear a drum solo with 2 x 15 in open baffle, you will freak out
I have to agree. I tried my OB three way with a single 15 and then moved to double 15s per side. The difference is not subtle. Subs are no longer required for me. My build is on the budget side using eminence drivers and a CSS planer tweeter.
Evan
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Old 15th September 2012, 01:52 PM   #105
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Thanks guys I need to factor in shipping from the US, and sometimes it is cheaper to buy four drivers than it is two... But I don't want to rush into anything, I need to slow down my thinking and evaluate each of the drivers a bit more.

Considering I haven't ruled out using the 15" AT drivers at $1000 each, the price difference between using 2 or 4 of the cheaper 15" is not an issue.

But I am perhaps thinking if I bring the 15" in to play first, that would tell me if I have a hole in the 200-500 range to fill.

Agree really shouldn't add extra drivers without there being a good reason to do so. Its not about the look of running 20 drivers, its about what's best for the sound.

Edit:
puppet X-Over from Tweet - Mids is 24dB LR both ways, same for mid woofer to mids.

Last edited by Silent Screamer; 15th September 2012 at 01:58 PM.
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Old 15th September 2012, 02:18 PM   #106
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My system uses a passive 24db LR xcover from a 12"mid to the tweeter at about 1900 hz. The mid has no low pass. The woofers are crossed to the midrange by a 2x8 mini dsp at 180 hz 18db Bessel. There is a very steep high pass for the woofers at 20 hz and some boost at the lowest end. This is not at all where I started out but what developed over some time playing and listening.
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Old 15th September 2012, 02:46 PM   #107
Toaster is offline Toaster  United Kingdom
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Sure, if additional subs are not being used, two 15s is clearly a good idea.
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Old 15th September 2012, 03:23 PM   #108
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Quote:
Originally Posted by Silent Screamer View Post
Edit:
puppet X-Over from Tweet - Mids is 24dB LR both ways, same for mid woofer to mids.
There's room to experiment here perhaps. A guy would want the individual FR of the drivers (especially the mid) to get an idea of how far the slopes can be stretched out cleanly.

I started out with LR4 slopes when I started my project, too. Safe, easy route for sure with a DSP. ... but if the drivers/equipment allow it, departing from that scheme can yield some nice sonic results.

A for instance ... I'm just working through a 2-way with subs. Fortunately for me the 12" plays nice beyond 1320hz .. my xo point. I'm using a heil for the top end. The LR4 sounded nice but I found that I seemed to rely more on the heil to "anchor" the upper midrange. The response from the 12" driver seemed to lack clarity in the xo region.

I stumbed on a thread by Wayne Parham on his website that inspired some experimentation with xo slopes and points. Resulting in a big difference for sure. Even though we're using DSP for xo generation, we still need to take into account the response of the drivers. It, the acoustic results, are cumulative. The steep slopes worked fine but on closer examination presented nulls in the FR that were not desirable .. hence the flat sound in the upper midrange.

At moderate SPL's my woofer likes a simple 6db roll off. The DSP allows a "thru" setting so it's a real 1st order roll off. ... but at elevated SPL's the combined sources produce too much .. so the compromise for me was a 6db roll off with the DSP resulting in a 12db acoustic response. ( I still prefer the 1st order slope for vocal/jazz though ... rock, not so much.) I did spread the heils slope back (up) a bit, too .. away from the 1320hz roll off of the woofer. This helped me attenuate that region of the xo that was too hot before. The blend is more seamless as a result.
Had I just left the xo points equal, as far as position, I'd have to attenuate the heil to the point of loosing too much top end. Makes for a heavy lower mid section. The heil is still attenuated (analog) but not nearly as much as it would have been with a symmetrical point/slope.

Attention to the lower end of the midrange had similar results in the 200/300hz range. Steep slopes tend to boost this region. Relaxing the slopes here seem to clean things up audibly. You don't have that heavy vocal resonance ... (Edel is famous for ... some RadioHead too.).

I realize that your project is a very different animal. Much more refined than mine. Just thought I'd throw out some of the things I'm finding as DSP xo's go. If they're flexible enough, there's no reason that you can't achieve results much like a well designed passive solution.
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Old 15th September 2012, 03:43 PM   #109
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The GPA 416 is a beautiful sounding driver right up to 1400Hz,

There are other options but I can guarantee this driver is incredibly good.

Last edited by Melon Head; 15th September 2012 at 03:46 PM.
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Old 15th September 2012, 04:14 PM   #110
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Back here to fill your head with more opinions. LOL!

If you want to see my whole build thread, head to Audiocircle, but if you want the quick recap, I started with AE Dipole 15. They played loud and low, but not enough for me. Plus, I felt that no amount of adjustment got the upper range as precise as I wanted. Not sure if it has anything to do with the elevated Q, but once I got the low Q B&C driver, the range between 100-250 was much more to my liking. Not scientific, I know, but what I personally experienced. I would say if you are dead set on NO separate sub, get the AE. If you want the tightest bass, two choices: Lower Q, high quality, high sensitivity woofer AND a good sealed or servo sub, OR get the GR Research servo open baffle kit. I was VERY close to using these. Heard them several times and properly adjusted they are super clean, tight and precise. Here's the issue though with OB bass versus OB subwoofer range. To get good, strong OB 20-40 Hz, you need massive displacement to hang in there at higher SPL levels. Hence Stigs 21" woofer array. Look back at John K's Music and design site. He has a good article why you don't want to try to use OB bass below the lowest room mode, which is calculated based on your room dimensions. In my case, that worked out perfectly to fold the subs in around 50Hz. Something you don't get as much of with OB bass is that visceral impact that you do with bass from cabinets. I wanted that too, since I was like you sparing no expense and having no WAF to worry about, it was no big deal to add a large sealed subwoofer in to the equation.

Greg
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