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Designing Open Baffle speakers...

Audiolab 6000A Amplifier

sureshkn

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Hi,
I am not sure how to put this correctly. But anyhow I will try to explain. :lol:
I had purchased a pair of Alpair 10M Gold (Gen 3) drivers. The original plan was to build Pensil enclosure for it. But when I showed the plan to my known carpenter, he was clueless and I did not have any confidence in him. So, the drivers are lying idle.

Then, recently one of my friend relocated to US and he gave me the following drivers in pair.,
Dayton Audio DC28F-8 1-1/8" Silk Dome Tweeter
SB Acoustics SB17NRXC35-8, 6.5" Woofer

I have no idea what to do with them. After some research in the net, I found about Open Baffle speakers. I feel that with pre laminated MDFs, the carpenter should be able to make it easily. Now the questions are.,

- How to find the enclosure plan for the Alpairs ? (I hope it does not require any crossover)
- How to find the passive crossover and enclosure plan for the DA & SB acoustics 2 way ?

Is there any software or any website that can help in the above ? Please guide me.

Best Regards,
Suresh.
 

mikehcm

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Bassbox pro will help you build enclosure for DA drivers, its better to buy premade crossovers online.
 

Sumanta

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I have realized (from experience) DIY needs lot of reading, then trial and errors too.
In return you may get benefit in expenses but surely get knowledge, understanding of how things work and insight to what you really want.

I suggest you define your requirement and define why you want OB speakers.
then you also list down your present setup and listening space. Decide whether that can support OB speaker basic requirement.

OBs are good way to get wonderful sound with minimal expenses and efforts. And if you combine OB with active cross over with computer through foobar and a supporting DSP (like creative sound blast) you will have the best value for money product (IMO).

We can talk more once you list down above mentioned requirements.

All the best.
 

saikatbiswas82

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Hi,
I am not sure how to put this correctly. But anyhow I will try to explain. :lol:
I had purchased a pair of Alpair 10M Gold (Gen 3) drivers. The original plan was to build Pensil enclosure for it. But when I showed the plan to my known carpenter, he was clueless and I did not have any confidence in him. So, the drivers are lying idle.

Then, recently one of my friend relocated to US and he gave me the following drivers in pair.,
Dayton Audio DC28F-8 1-1/8" Silk Dome Tweeter
SB Acoustics SB17NRXC35-8, 6.5" Woofer

I have no idea what to do with them. After some research in the net, I found about Open Baffle speakers. I feel that with pre laminated MDFs, the carpenter should be able to make it easily. Now the questions are.,

- How to find the enclosure plan for the Alpairs ? (I hope it does not require any crossover)
- How to find the passive crossover and enclosure plan for the DA & SB acoustics 2 way ?

Is there any software or any website that can help in the above ? Please guide me.

Best Regards,
Suresh.

I thought Pencil design was pretty easy one.
Dave & Scott's Pensil 10.2 design

I believe, any professional carpenter should be able to build this.

For a full range like Alpair 10, Frugal horn or Pencil should be good IMHO.

I think OB requires a larger woofer (like 12 inch or more) to get the bass extension. For a small woofer like "SB Acoustics SB17NRXC35-8, 6.5" Woofer" it might not make much sense to put it in OB. You might miss out the bass part entirely.

For the Dayton, SB Acoustics combo, the only design I could think of a Bass reflex Vented or a TL design. This is purely IMO.

One more thing. If you want to use the Alpairs in OB, You can use it with a 15/18 inch woofer (e.g. Ahuja PA drivers or something like that). :)
 

sureshkn

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Hi Sumanta,
Though I posted in DIY section, I am not a DIYer at all. If I make these OB speakers then these will be my first DIY projects.

Why I want to make OB is tricky. I feel OB should be easier to build compared to other enclosures. That is my first reason. Second reason is., I fitted the Alpairs in a card board box with back open for burning in the speakers. Right from the beginning I felt the audio quality was better than my current speakers (BA-A26).

My present setup is.,
Source : Pioneer TT & Fiio X3.
Amps : Nakamichi IA2 & Jean Hiraga 8W (made by Sachin, Om & Raghu)
Preamp : B1+CNC Phono (made by Sachin, Om & Raghu)
Speakers : Boston Acoustics A26.
Listening space : I have two options. Hall = 18x15 feet. Room = 14x10 feet.

Best Regards,
Suresh.
 

bibin3210

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Suresh,

The drivers with you are not suited for an OB design, may be you can use Alpair 10 along with some big LF drivers (15 inch or above). You need to look for drivers with Qts above 1 and sensitivity greater than your full range driver.

I do agree with Saikat's recommendations. You can try Frugel-Horn XL with your alpair 10. You can find more details here:
The Frugel-Horn

Frugel-Horn XL for Alpair 10.3/10p - diyAudio

BTW I am currently building an OB using two 15" drivers (Eminence ALPHA-15A) and a 8" full range (Tang Band W8-1808). IMO the driver selection is very important for an OB design. Also there are different type of frame configuration like H, U,W, Flat etc. for Open Baffle (Dipole) and based on this sizing and compensation network design varies. Attaching here the drawing for you to get an idea.



Thanks,
Bibin
 

Fantastic

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Hi Sumanta,
......I feel OB should be easier to build compared to other enclosures.........

The simple part ends there ! :)
Then you need to equalise it to make it really sound good. It does sound attractive even without much equalisation but then there is a lot that you will find not OK in the long run. But they do have some inherent qualities that are quite desirable.
It's engineering. Nothing comes for free and there are lots of compromises on the way ! :)
Enjoy your build ! It would be worth the time and trouble you take over it. ;)
 

Sumanta

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Easy road = make existing design.

Tough and risky road = read, understand, choose, compromise, try, fail and enjoy the whole process of DIY.
If you LF driver is atleast 6 SPL higher in efficiency than the full ranger, you can make one. Going passive will incur even more read/research and all those trials.
 

Sumanta

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What are the T/S parameters of your drivers?
Will you be able to put fnished OB 3 feet away from your front wall while listening music?

OBs sound charmingly fresh, so it always catches fancy of inquisitive ears. getting right bass is difficult but achievable. And once you hear bass from OB, it will be tough to go back to even TL type of bass.
 

Sumanta

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In one sentence, I am very happy with Ahuja drivers. Most are of opinion that PA drivers are not audiophile grade (I feel from their writing and discussion, that they have not heard them playing in OB).
Some of us use all Ahuja or low frequency (LF) drivers only of Ahuja.
I use their cheapest LF drivers like As 15 200 for LF.
You need to know their technical (design) limitations to use them for the best return.

I suggest you read posts of Dr Jaufere on his journey of making a OB speaker set.
There are many other posts too in this forum.

You are always welcome to contact me for any information, writing here for me is more time consuming, delayed from my side and sometime less informative.

On the other hand if you want to go the way I had been, then read my OB journey and then we can start with your drivers and (probably) mixing Ahuja LF drivers there in.
 

Hari Iyer

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IMO Ahuja 12" FR driver will also make an excellent advance TL loading.
 

sureshkn

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This weekend I talk to another carpenter and showed the drawings of Frugal Horn & Pensil. He said the can make it and looked confident too. :)

But I want to fully explore OB, before deciding.

Sumanta,
Here is the TS params for the Alpairs.

Alpair 10 Gen.3
T/S date LMS V4 Anechoic:
Revc= 7.200 Ohm
Fo= 38.266 Hz
Sd= 8.825K mm2
Vas= 26.320 Ltr
Cms= 2.380m M/N
Mmd= 6.792 g
Mms= 7.269 g
BL= 5.772 TM
Qms= 1.930
Qes= 0.378
Qts= 0.316
Levc= 71.379u H
No= 0.378 %
SPLo= 87.988 dB
Xmax = 7.5mm (1 way with Arrestor)
Power = 30 watts nom.

Regards,
Suresh.
 

Sumanta

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This driver has quite low Qts and Spl for so called perceptional behaviour of any OB. But I think you can give it a try by an easy way.

1) Tell someone to hold it with bunch of news papers or any hard board folded like a cylinder on the back of the driver. Use one only. Listen to 3 major frequency ranges like 50 to 150, 500 to 2500 and 8000 to 18000 by playing some instrument or other sources (computer with internet comes handy). Then play some good vocal sources that you are very familiar with (in terms of your expectations).
I do not expect you be able to have a cylinder any longer than 1 foot.
If it sounds even 30% to your expected liking, you IMO should be happy with a OB design. If that driver is good at highs, fine, or else you can add a simple tweeter with a capacitor.
I think you can follow Jaudere's design by having non-parallel sides of your baffle to support LFs as a final design. Or else you can simply add LF drivers of Ahuja, Considering small size of your driver, it will give a good look to the LF cabinet by having a Ripole shape. We can talk about that later.

IMO Ahuja 12" FR driver will also make an excellent advance TL loading.

We definitely can make a TL with 12 FRX driver of Ahuja, but its size will be huge. If it is okay with you Hari, please share a preliminary dimension of the cabinet considering 45 Hz and a tapered line. ATL will be even longer and wider if I am not wrong.
 
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jmascreen

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Thanks man, let me first go through all the threads you suggest and I will come back with lots and lots of questions.

This driver has quite low Qts and Spl for so called perceptional behaviour of any OB. But I think you can give it a try by an easy way.

1) Tell someone to hold it with bunch of news papers or any hard board folded like a cylinder on the back of the driver. Use one only. Listen to 3 major frequency ranges like 50 to 150, 500 to 2500 and 8000 to 18000 by playing some instrument or other sources (computer with internet comes handy). Then play some good vocal sources that you are very familiar with (in terms of your expectations).
I do not expect you be able to have a cylinder any longer than 1 foot.
If it sounds even 30% to your expected liking, you IMO should be happy with a OB design. If that driver is good at highs, fine, or else you can add a simple tweeter with a capacitor.
I think you can follow Jaudere's design by having non-parallel sides of your baffle to support LFs as a final design. Or else you can simply add LF drivers of Ahuja, Considering small size of your driver, it will give a good look to the LF cabinet by having a Ripole shape. We can talk about that later.
 

Hari Iyer

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We definitely can make a TL with 12 FRX driver of Ahuja, but its size will be huge. If it is okay with you Hari, please share a preliminary dimension of the cabinet considering 45 Hz and a tapered line. ATL will be even longer and wider if I am not wrong.

@ Sumanta
I do not have the skills to design a tapered TL line and all my designs in TL has been straight line. Also i do not follow the classic TL design approach where the driver is tuned to the resonance freq. I tune it much higher than resonance. This keeps my line shorter but thicker due to increased cross-section area. Also there need not be any off-set required in this design.
If you have the 12 FRX driver, i would suggest you the measure the Fs, Qts and Vas of the drivers before I design and publish as in my experience the published and measured values vary from 5% to 15% depending totally on your luck. I will post one design based on the published parameters for the discussion today for the 12 FRX.

A quick calculation gave me the following dimensions with the published parameters for the 12 FRX

H = 36", W = 21", D = 21". Cross-section area = 390 sq.inches. Terminus preferably at the bottom - hence needs stands for escape of LF. Tuned at 80Hz.
Will need to add 7KG of polyfill stuffing for the odd harmonics with damping coefficient of 1.89 pounds/cubic feet.

Since Vas of this driver is very high (105 Liters) it will give too high, punchy and deep bass which could shake everything in the room. Recommended for outdoor use or may be OB loading.

Cheers,
 
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greenhorn

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Hi, sorry to highjack the thread, but i have a similar requirement.

I'm using a pair of philips HiQ speakers in an open back (not sure if this is the right term - It's a stock Sony Cabinet with a perforated back covered using some sort of felt)

the sound quality is amazing, but there is nothing below 100 Hz. I'm not planning to squeeze anything out of it using any TL or eq, but rather, try to build a woofer that can take care of the lows (<100 hz)

Looking for cheap high sensitivity woofer, I came across the Pioneer TS W304R & the ahuja L12 MB200. What sort of enclosure would be advisable? I was interested in something like an H baffle, but due to space constraints, I would need to keep them pretty close to a wall, plus am not sure how/where to design an H baffle.
a vented box is the backup plan (both drivers have recommended vented box plans) but any advice on choice & design for an open enclosure would be appreciated
Thanks!
 
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soundnovice

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go with FAST speakers. use high qts 15" woofer with alpairs. woofers in u-frame and alpairs on open baffle. crossed at 200-300hz. many have done this on diyaudio.com using eminence alpha 15". at above 200hz, qts of alpairs doesn't matter. high passing woofers at 40hz helps with low distortion.
 
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