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Old 20th December 2006, 12:18 AM   #1
taloyd is offline taloyd  United States
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Default design help needed: monopole 15" / 8" MTM open baffle with Manger

Hello,

I'm trying to conceive a design involving the following:

A sealed monopole subwoofer, composed of an isobaric pair of AV15 drivers down-firing in a sonotube dimensioned to get a system Q of around 0.5.

A open-baffle with two Dayton RS225 8" aluminum woofers.

A Manger (sealed) in between the Daytons in a MTM configuration.

Crossover is variable, as it is a Rane AC23B unit, which provides LR4 slopes and electronic time alignment. EQ is via a Behringer DEQ2496. Source is a Squeezebox.

I was hoping for crossover points of 70/190. This will keep the subwoofer operating at a low range, away from male vocals, keep the midbass dipole (cardioid perhaps), and keep all excursion away from the Manger. I was thinking of U-frame, heavily braced, with the wings splayed out around 20 degrees, and about 10" in length.

(One of the many) other alternatives is to change the configuration to a 2-way TMM or MTM (perhaps similar to Andre Perrault's grand system, two way with 15" TAD and TAD horn, running through a DEQX) style with two Aurasound NS12-513 subwoofers, crossed at 190 Hz to the Manger driver. A U-frame would be nice if it could be short enough to keep the resonance from the 190 Hz crossover point, but deep enough to allow the subwoofers to still provide response flat to 30 Hz. The advantage of the Dayton MTM configuration is a little better pattern control in the vertical axis, which should somewhat alleviate floor/ceiling reflections. Also I wouldn't need to get rid of 4 AV15 and 4 RS225 drivers and then purchase 4 more other drivers...

Another possibility is to drop the two RS225 8" drivers for one Aurasound 12" used instead. That should keep the excursion down, and could perhaps even use a flat baffle, eliminating the visual heft of a U-baffle with splayed wings.

Conceivably, I can also use the AV15 drivers instead of the Aurasound, but I don't have much faith in them reproducing cleanly up to 190 Hz. If open-baffle TMM, it could be something like Bert Doppenbergs Quasar system (pic attached).

In case you're wondering why I'm stuck on 190 Hz, is that it's simply the lowest point available on my crossover for a 2-way. As 3-way, the lowest points are 70 Hz and 190 Hz. I can go the DCX2496 route, but that would mean eliminating most of my system (DA converter, crossover, existing Alps volume control, etc.) which I'd rather avoid... DEQX would be wonderful, but I don't have the funds for that. I would also like to avoid sealed boxes for all but a subwoofer in a <70 Hz setup...


Thoughts?


much thanks in advance,

-Tal Allweil
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Old 20th December 2006, 06:34 AM   #2
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Though I use the MSW as well - I don't have any experience with using it in an OB (apart from casual listening to the bare driver when it was brand new).

But I would definitely NOT use it in a thick baffle like the one shown because you would spoil its temporal behaviour (which is actually the main reason for using a Manger in the first place !).
Form the visual point-of-view it is definitely damn cool though I have to admit.

Regards

Charles
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Old 20th December 2006, 01:55 PM   #3
jirka is offline jirka  Czech Republic
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The Manger MSW driver is excellent as a monopole from 150Hz up.

The dipole configuration is not recommended because there are some reflections from the motor structure on the back side. Therefore you will always hear some problems in the 1-4 kHz band until the open baffle is really wide.

I used 200Hz tractrix front horns and this suppresed this ringing.

Small open baffle is definitely not good with Manger driver.
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Old 20th December 2006, 02:09 PM   #4
taloyd is offline taloyd  United States
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Default to clarify

Hello again,

Manger will be mounted SEALED in an open-baffle with the 8" woofers. I have no intention of running the Manger OB, as it is specifically recommended against by both Manger and Andre Perrault.

OB is for the midwoofers, and possibly the subwoofer...

thanks,

-tal
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Old 20th December 2006, 02:17 PM   #5
tinitus is offline tinitus  Europe
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I take it you mean sealed box with wide baffle

I would stick to 2-way

I think a 3-way, with all C/O below 190hz will cause problems

You know, Greg Ball Guru has a little simple EQ kit


I wonder how it would work with double Manger in dipole setup, now that you plan to do dipole bass

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Old 20th December 2006, 02:53 PM   #6
taloyd is offline taloyd  United States
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Default more clarification

The configuration I'm envisioning is as follows:

an MTM baffle with the Manger SEALED in the middle, and Dayton RS225 8" drivers above and below. The baffle would be minimum-width, around 9", and the wings would be angled out, like th extremely crude drawing attached.

The subwoofer would be for below the midbass content, around 70 Hz if at all possible. At those frequencies (<190 Hz) the wavelengths are long enough that the driver spacing is more than adequate, as the 8" drivers are going to have no more than a 20" C-T-C spacing, and will be within 10" of the Manger's acoustic center.

This is all hope at the moment, as don't have the facilities to make test boxes... I need to comission a carpenter for each iteration/prototype. So the purpose of this thread is to at least finalize the first prototype, so I can have it built, and test it...

thanks again,

-Tal
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Old 20th December 2006, 06:47 PM   #7
Tenson is offline Tenson  United Kingdom
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Hi,

Actually the Manger is not bad in an open baffle! As long as you use it above about 200Hz where it starts to need the loading of the box.

I have used it in an open baffle with a diffusor behind the speaker and like it more than with the back closed in. I can understand why people say the Manger is a bit dull sounding and when in an open baffle with a diffusor it helps to liven it up and open it out. I think a big part of that is having a more even power response from the diffuse rear reflections, otherwise it is quite directional in the HF.

Taloyed, I have sent you an email. Although I have got pretty decent results from the Manger I think I am ready to move on and try other things now so I could sell mine to you if you are interested. They are in excellent condition. If you were not here talking about it I would probably hang on to them but since this has popped up I may as well move on I think.
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Old 20th December 2006, 07:25 PM   #8
Paul W is offline Paul W  United States
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Tal,
No experience with the drivers you are using, but I will comment on the baffle.

A few years ago, I built a test baffle with hinged wings to listen for any sonic signature with various wing angles. With any included angle of less than 90 degrees between the wings (each wing at 45 degrees) an audible resonance developed to the rear of the speaker. The resonance can be handled, but it is worthy of consideration.

For test baffles, hinges can be an easy and worthwhile addition. As well as changing angle, hinges make it very easy to change wing size by simply mounting different boards.
Paul
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Old 21st December 2006, 01:02 AM   #9
AJinFLA is offline AJinFLA  United States
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I don't see any reason the Manger couldn't be used OB.
Crossing in the "critical" range is only "bad" when you are "bad" at crossover design .
I'd only run the Manger down to 250-300hz to limit excursion as much as possible. Boxless - of course.
I'd use larger than 8" below 300hz, 10"-15" preferably, on a flat baffle, to get better matched, more constant directivity over as wide a range as possible.
The monopoles below 70hz should be ok. You'll be cardioid there anyhow. I would suggest bipole configuration if possible, if your main panels are sitting on top of them.

cheers,

AJ
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Old 21st December 2006, 01:50 AM   #10
Tenson is offline Tenson  United Kingdom
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Sorry but i just realised that when I sent my email to you Taloyd, I had not updated my address here in DIY-Audio. So, if you simply hit 'reply' I may never receive your message! You should be able to find my updated email in my profile.

Ta
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