[THROWBACK]

I am considering building an OB vertical line array of 6-8 8" woofers to supplement the bottom end of my Sound Lab M1s. Great speakers, but they lack low and mid-bass "punch."

Why a line array? To mimic the dipole pattern presented by my ESLs.
Why 8"? Real estate and speed. (I could probably go with 10" if I had to.)

I have done some research into Dayton, Peerless, VIFA, AE, etc., but I'm just getting more confused. I believe I have found that for OB design xmax and Qts should be as high as possible, with a low Fs. But how high/low is enough?

Any driver (or other) suggestions out there?

Thanks,
Chuck

[FullRangeMan]

I am considering building an OB vertical line array of 6-8 8" woofers to supplement the bottom end of my Sound Lab M1s. Great speakers, but they lack low and mid-bass "punch."

Why a line array? To mimic the dipole pattern presented by my ESLs.
Why 8"? Real estate and speed. (I could probably go with 10" if I had to.)

I have done some research into Dayton, Peerless, VIFA, AE, etc., but I'm just getting more confused. I believe I have found that for OB design xmax and Qts should be as high as possible, with a low Fs. But how high/low is enough?

Any driver (or other) suggestions out there?

Thanks,
Chuck

HI,
Iam a OB and LA fan too, unfortunately I had to give-up when I realize hi quality music need crossoverless and parallel connections of the various LA drivers, so for 8woofers I will need a 64ohms impedance woofers to parallel then to obtain a final impedance of 8ohms(64/8=8).
As 64ohms woofers do not exist, you will need a crossover that correct this low impedance issue (8 ohms/8drivers=1 ohm), also there is the Comb Effect that various non small drivers may have.

As below 120Hz the music spread in all directions I could suggest you my personal preference: you may try only one 18inches woofer, as the Goldwood 1808(low price) or the new Acoustic Elegance Dipole18, this last seems will be released in a few weeks and it is specially made for OB use, and right now there are avaliable the Dipole15 inches.
http://www.aespeakers.com/drivers.php?driver_id=32 price around 309dollars for one driver.
Regards, Gustavo

[JohnR]

HI,
Iam a OB and LA fan too, unfortunately I had to give-up when I realize hi quality music need crossoverless and parallel connections of the various LA drivers, so for 8woofers I will need a 64ohms impedance woofers to parallel then to obtain a final impedance of 8ohms(64/8=8).
As 64ohms woofers do not exist, you will need a crossover that correct this low impedance issue (8 ohms/8drivers=1 ohm), also there is the Comb Effect that various non small drivers may have.

Hi, on this one, with 8 x 8 ohm drivers you would connect them 2x in series, then 4 lots in parallel, to get a total 4 ohm load. Comb filtering would not be an issue as these will be low-passed.

[FullRangeMan]

Hi, on this one, with 8 x 8 ohm drivers you would connect them 2x in series, then 4 lots in parallel, to get a total 4 ohm load. Comb filtering would not be an issue as these will be low-passed.

Electrically works well, but I afraid of suggest serie-parallel drivers connections as I had used it in a 4 x 10inches and not good sound(image below), but this drivers are fullranges, with low pass woofers THROWBAC may have more luck.

[lowtech]

My advise is to basically ignore the TS specs of the drivers.  IMO the only way you will achieve good results is to use an electronoic crossover and apply a modest amount of boot to offset dipole cancellation.  The only driver specs that will concern you is Xmax and Sd (the larger the better).  You can use SL's spreadsheet to determine the size and number of drivers required (swept area) to achieve your desired SPL Vs. frequency.  As others have mentioned you can use a series/parallel connection configuration to achieve your target impedance.  Peerless XLS/XXLS are excellent drivers that have a low amount of wind chuffing.

[THROWBACK]

Thanks for the inputs.

I would like to stick with the 8-inch woofers and equalize to bring up the bottom end. I have a Hartley 24" that I could mount in a wall backed by my furnace room (infinite baffle, essentially) but I would like to try the OB array solution.

Anyone recommend a good OB-ready 8" woofer? (At a reasonable price, of course.)

[lowtech]

I would like to stick with the 8-inch woofers and equalize to bring up the bottom end.

I think you may be disappointed with even a large number of 8" drivers.  They simply don't have high enough Sd to work below 100Hz and the very high excursions will produce too much noise.  That said, the highest Xmax 8" driver I'm aware of is  this one.  Good luck.

[panomaniac]

4x8" drivers will have 15-20% more surface area than one 15" driver.  FWIW.

[lowtech]

4x8" drivers will have 15-20% more surface area than one 15" driver.  FWIW.

True... everything else being equal.  The Exodus drivers that I cited above have a Fs of 45.8Hz and aren't going to work as well as, say a single 15" TC-Sounds.  I do have some first-hand experience using small woofers in a dipole arrangement and am just sharing my experience.  That said, the OP (or anyone else) is free to do as he sees fit.   

[mcgsxr]

I agree that although swept area matters for OB, there are other factors to consider also, including FS, and XMAX.

The Peerless are well respected 12's.

I use some 12 inch Mach 5 Audio's that I bought 3 years ago.

Car audio may hold the key - using dual VC drivers, and only using one of the VC effectively doubles the QTS - useful when considering used gear etc.

Could you build an OB with wings in a Z shape, and angle it - thus using an Eminence 15 as an example, but only "seeing" around an 8-10 inch width?

[lowtech]

Could you build an OB with wings in a Z shape, and angle it - thus using an Eminence 15 as an example, but only "seeing" around an 8-10 inch width?

That would certainly work, although I was under the impression that the OP wanted to create a line-source of drivers to mate with his large planars.  I think that is a good approach, especially if the bass drivers will be crossed high (into the mid-bass region).  Since the OP hasn't stated where he want's to cross the woofer array, a single 15" driver would work well provided it's crossed low - less than 60Hz or so.  However, once you decide to cross that low you should consider using a monopole instead of a dipole...

[mcgsxr]

Good point - perhaps the Z baffle can be leveraged to create an effective baffle width to drive useful bass for a line of 8's, but meet the need for a slimmer presentation visually.

I Xover my 12's at 100Hz or so, to my OB b200 Visatons.

[panomaniac]

The Exodus drivers that I cited above have a Fs of 45.8Hz and aren't going to work as well as, say a single 15" TC-Sounds.

Yeah, OK. But I thought we were talking line array here.  A single 15 isn't a line array, tho it may well work better.