Need advice on my open baffle build

[gadut]

my open baffle panel dimension is 50cm x 110cm with 18mm plywood. I have used Alpair 10p with additional $7 cheap car tweeter but they dont integrate well. Today I receive my package for tweeter JBL gto 19T, using 2nd order XO @10.5kHz (1.5uF & 0.15mH) plus 1ohm series resistor, now they blend nicely. I think that i have settled on HF driver.

Now I'm still not sure which driver for bass, my previous plan was to use Eminence Beta 15A 2pcs per side which seems commonly used. But when I read on SBAcoustic article that they also produced PA driver (ACR brand but only for Indonesia market), I find 15" driver with T/S parameter which seems 'better' than Beta 15A.

15″ 38H156SCF ACR SPECIAL NEW | ACR Speaker

I have compared both T/S value and most significant differences are Qts, Xmax, and for sure their price. from the graph also shows that ACR reach 95dB on 30Hz, while Beta 15A reach it on 110Hz.

I get a feeling that this is too good to be true, but i have limited knowledge and experience on speaker driver. can anyone give me advice whether should I use this ACR driver for my OB bass instead of Beta 15A?

Regards

 

[adason]

Nice work so far...
I spent quite a lot of time optimizing crossovers between fullrage and tweeter, and its not always easy and straightforward. In my humble opinion you have to use low pass on fullrange, once you decide on tweeter. See, fullrange will try its best to reproduce some heights, which will interfere with tweeters output an results in rugged response and poor integration. If you use well behaved midrange with no breakups, you could get away without low pass, but with fullrage I always end up 4th order LR, and 2nd LR on tweeter. I measure and listen, and swap parts...till all is good and sound is seamless, sweet and coherent. Bass is another story.
Good luck.

 

[gadut]

@adason
I find that playing with FR & tweeter seems easier, only need to combine capacitor value ( I use multiple 0.5uF to get the treble that sounds good to my ears)

finally bought 2 pairs of ACR driver @ $28 each and started to make 15" holes. "it's stupid but it works" is all I can say about making 4 holes of 15" by using hand drill, hole saw, and hand saw.

to stabilize the panel, i order metal triangle from nearest workshop. it's strong and look nice too. I should put my 3way to living room since no more space with this huge OB (my wife and twin boys are happy now to have this 3way to watch TV and movie )

the drivers are connected in parallel, use 2nd order PLLXO @80Hz after dcb1 and powered by FirstWatt M2 clone. I have set the volume in maximum position to get strong bass but the vocal is still dominant, maybe 24dB is required for this 15" which is listed as FullRange.

another try is playing with my old laptop + mauropenasa gainclone with Eq, set on V-shape Eq and surprisingly this 15" has good treble, even no need to connect A10p or jbl tweeter. with only left speaker connected (another one is still on progress), I'm blown away with what I hear now, compared to the 3way, this OB create HUGE sound and fills my 3x4m living room.

Size does matter, the bass which come from 2x15" seems like effortless compared to 7" in BR. Increasing the volume does not show any compressed sound, I dont dare to test on maximum volume yet in order not to get my neighbor complaint. Vocal and treble is more enjoyable than 3way, my memory says that Alpair 10P is good on low volume but not stable on high volume. seems that this PA driver is so much fun for DIY.

This 15" OB is the best $150 that I have spent on DIYaudio, never regret to choose this route

 

[mordikai]

Wow! Nicely done,enjoy. I Love big open baffle bass!

 

[bitinhvi]

Hi Gadut,

I am building a open baffle, 02 x 15" bass drivers with 01 full range driver. But it when bass driver play, the baffle vibration is quite a lot, it make the full range vibration also.

Have you experience that issue?

 

[gadut]

finished another set with rounded top corners. it's time to build LP/HP filter + bass boost

Hi Gadut,

I am building a open baffle, 02 x 15" bass drivers with 01 full range driver. But it when bass driver play, the baffle vibration is quite a lot, it make the full range vibration also.

Have you experience that issue?

No, my OB does not vibrate at all eventhough with massive low freq Eq.

my consideration during this build:
- use strongest plywood that you can find, mdf is a big no
- what kind of supporting side panel that you use? my panel is supported by 30x30x3mm reinforced steel and additional decoration from solid rectangular steel
- additional carpet at the bottom will give better grip to the floor

I have tried to push the panel as strong as I can but it barely moved, maybe only 1-2mm and for sure my hands are not weak. hopefully it can give some insight

 

[ashok]

Hi Gadut,

I am building a open baffle, 02 x 15" bass drivers with 01 full range driver. But it when bass driver play, the baffle vibration is quite a lot, it make the full range vibration also.

Have you experience that issue?

Yes the baffle vibrates a lot. You need to have a very stiff baffle. The old style double layer baffle with sand filled in between the two sheets would be a good method to reduce this. I have a plan on my mind but haven't yet got to trying it out. The single layer ply used for an initial test visibly vibrates on bass notes. I have used sand filled baffles earlier . They are quite stable and 'dead' ! My speaker stands for my bookshelf speakers are all sand filled ! Makes them very heavy too.

 

[matejsirk]

Hi,

15″ 38H156SCF ACR SPECIAL for 29$ looks very very interesting driver. Could you provide some links where we can buy this driver?

Regards

 

[gadut]

@ashok
if my memory is good, you have used Eminence Beta 15A rite? did you try to give massive Eq low bass? is it good? I choose this ACR since i get advice from my neighbour who has PA business that Eminence is weak, while ACR cone that i boosted is moving like subwoofer because it has 7mm xmax

@matejsirk
this ACR driver is produced by Sinar Baja for PA market and I think it's only available in Indonesia. you can look at below distributor list that they are all located locally

DISTRIBUTORS | ACR Speaker

I dont think those distributor will ship overseas and the cost will be high

SBAcoustics (SB ~ Sinar Baja) product line is for international market but they are for high end audiophile

 

[bitinhvi]

finished another set with rounded top corners. it's time to build LP/HP filter + bass boost

No, my OB does not vibrate at all eventhough with massive low freq Eq.

my consideration during this build:
- use strongest plywood that you can find, mdf is a big no
- what kind of supporting side panel that you use? my panel is supported by 30x30x3mm reinforced steel and additional decoration from solid rectangular steel
- additional carpet at the bottom will give better grip to the floor

I have tried to push the panel as strong as I can but it barely moved, maybe only 1-2mm and for sure my hands are not weak. hopefully it can give some insight

Unfortunately, I using MDF .

Thanks for your advice. I will change to plywood.

Thinking to try as attached cabinet, shared by a forum member (sorry I do not remember), I think it may help to reduce vibration and the size of baffle.

 

[bitinhvi]

Yes the baffle vibrates a lot. You need to have a very stiff baffle. The old style double layer baffle with sand filled in between the two sheets would be a good method to reduce this. I have a plan on my mind but haven't yet got to trying it out. The single layer ply used for an initial test visibly vibrates on bass notes. I have used sand filled baffles earlier . They are quite stable and 'dead' ! My speaker stands for my bookshelf speakers are all sand filled ! Makes them very heavy too.

Thanks Ashok, if my new cabinet in plywood does not help, will try sand filled baffle as your suggestion.

 

[ashok]

@ashok
if my memory is good, you have used Eminence Beta 15A rite? did you try to give massive Eq low bass? is it good? I choose this ACR since i get advice from my neighbour who has PA business that Eminence is weak, while ACR cone that i boosted is moving like subwoofer because it has 7mm xmax

@matejsirk
this ACR driver is produced by Sinar Baja for PA market and I think it's only available in Indonesia. you can look at below distributor list that they are all located locally

DISTRIBUTORS | ACR Speaker

I dont think those distributor will ship overseas and the cost will be high

SBAcoustics (SB ~ Sinar Baja) product line is for international market but they are for high end audiophile

Yes Gadut,
I did use the Eminence Beta 15A. Your memory is quite good !It was equalised and sounded quite good. But you cannot go too low as the cone excursion is limited. I had used a 12 inch Peerless woofer earlier with 9mm Max excursion that went deeper . However even with that there is limit on how low and loud they can go unless Xmax is quite large. My future designs will use a subwoofer in a sealed box to help with frequencies below 60 hz !

 

[gadut]

Unfortunately, I using MDF .

Thanks for your advice. I will change to plywood.

Thinking to try as attached cabinet, shared by a forum member (sorry I do not remember), I think it may help to reduce vibration and the size of baffle.

I assume that M-frame seems better based on physical layout and it also benefits with lower size. I was going to take this layout but it will require better tools to build.

http://www.diyaudio.com/forums/multi-way/95185-dipole-m-frames-_-look-their-benefits.html

LX521 Description

Yes Gadut,
I did use the Eminence Beta 15A. Your memory is quite good !It was equalised and sounded quite good. But you cannot go too low as the cone excursion is limited. I had used a 12 inch Peerless woofer earlier with 9mm Max excursion that went deeper . However even with that there is limit on how low and loud they can go unless Xmax is quite large. My future designs will use a subwoofer in a sealed box to help with frequencies below 60 hz !

If flat baffle did not give me enough bass, I also had a plan to add extra sealed subwoofer using JBL GTO1214D (cheaper than Lab12) on each channel. But now i dont need that extra sub

my crazy idea someday is to build SLOB to copy Papa's work but using this ACR 15" (6pcs per side) instead of 8" driver on original design

 

[perempe20]

can I use this thread?

I have various drivers here. what OB can I build?
Fountek FW168 (pair)
Seas 27TBFC/G (pair)
HiVi S6N (2 pairs)
HiVi SS6N (pair)

what to build? I'm thinkink about an OB with a 6" midrange with separate subs. which 6" midrange shall I use? (the S6N has a smooth sound to 6-7KHz, but a Fountek might be better.) shall I get a cone tweeter or I can use my Seas domes? what subs shall I build? (might go with 2 HiVis per side. closed or ported?)

 

[gadut]

can I use this thread?

I have various drivers here. what OB can I build?
Fountek FW168 (pair)
Seas 27TBFC/G (pair)
HiVi S6N (2 pairs)
HiVi SS6N (pair)

what to build? I'm thinkink about an OB with a 6" midrange with separate subs. which 6" midrange shall I use? (the S6N has a smooth sound to 6-7KHz, but a Fountek might be better.) shall I get a cone tweeter or I can use my Seas domes? what subs shall I build? (might go with 2 HiVis per side. closed or ported?)

I'm not an expert since this is my first OB build, but maybe i can share what i have read among several builds by others.

6" in OB + plus sub is not a good match which you might lose in the range of 100-300Hz which is critical. that range usually filled by 12"-15" woofer, so it will be better you do not use sub now. but if you dont want to use additional woofer and only use subwoofer, it will be better to put 6" in a box (ported or sealed) where you can refer to FAST thread.

but if you want to use 15" woofer and you need to decide which 6" to use, you can build something like this https://speakerprojects.wordpress.com/2015/12/14/vifa-tc9-plus-helper-tweeter-on-open-baffle

tweeter is an additional option, which you can add later and you might need it or not

happy building

 

[DieterK]

A 6" works in my Baffle very well with two 12" Basses. A little Dip at 300Hz but not dramatic. Here you can see the response in my room. Only low end (20-40Hz) is equalized.

 

[perempe20]

P-17 speaker project
is a similar crossover good? (0.39mH + 80μF for the midrange.) I might try it with closed subs.

or shall I make an open back speaker with two 6" drivers (per side)?
CT269

 

[gadut]

P-17 speaker project
is a similar crossover good? (0.39mH + 80μF for the midrange.) I might try it with closed subs.

or shall I make an open back speaker with two 6" drivers (per side)?
CT269

P17 seems better from layout perspective, but I find that crossover is too high for midrange. maybe you can use attached layout and xo ( i think it was posted by ZM) which I use as my reference

 

[DieterK]

P-17 speaker project
is a similar crossover good? (0.39mH + 80μF for the midrange.) I might try it with closed subs.

or shall I make an open back speaker with two 6" drivers (per side)?
CT269

When Open Baffle then make also the bass open. Its a great advantage...

 

[gadut]

it has been a year since I started my OB project and it has transformed into some variations. I got pm yesterday and I think it's better if i post it here.

hi gadut,

I came across your post at Open baffle gallery and very interested in your speaker design.
"completed my plain OB on 36mm plywood panel 32" x 46" :
- ACR 113212 21" : active xo 24dB filter.
- Fane 12-200LT : lpf 1.9mH
- Fostex FD600 & H500 : hpf 10uF
- Fostex T90a : hpf 1uf"

I'm building a couple of FW amps already Alelph J, F4, F5, BA-3 pre and BA-3amp.

I did not have alot of speaker builiding experience. I've been studying and reading up on speaker type, model, Xover and settle to open baffle.

Would you mind sharing with me how did you come up with your design? Is there any specs, document that you could share with me what type, size of wood panel, what type of Xover, what frequency range to adjust to make this Open baffle speaker sound at its best performance ?

I already had 2 18"in subwoofer from Altec Lansing. I'm on the look out for a good twitter and midrange but not sure what type, kind to look to combine with the 18in subwoofer to create a nice pair of open baffle
Thanks,
Tom

Here are my OB variations history, where above question is related to my 3rd variation.

As you can see, I have used same baffle for 3 variations and I did not have any spesific calculation on baffle size. Just use my imagination to make proportional size in shape.

I'm using 4th variation now, which I posted previously here http://www.diyaudio.com/forums/multi-way/123512-ultimate-baffle-gallery-234.html#post5144045

below my room layout, simple noobs tool using xlsx file it's just a small 2.7x4.7m living room

below my 5th variation OB plan, 21" sub will be on H-frame. I have Altec 416-8a that I will utilise and follow this dimension http://www.diyaudio.com/forums/mult...ico-baffle-lowther-america-2.html#post5273683
I'm not going to buy Lowther yet, I will still use my existing 8" fullrange

I'm not crossover man in variation 2 & 3 where I found it was really difficult to get a good blend on that drivers. I'm going to sell my horn tweeter since it will not fit my future plan. It is easier to experiment with 8" Fullrange + Super Tweeter and then supported by additional bass drivers

Since you are using 18" Altec, you might try to copy PureAudioProject baffle idea (had a plan to build it but did not proceed it). However for bass support, definitely having an amplifier with dsp is a must for me, because you will have to tweak it alot until it blends nicely.

Playing with OB will give you less dissatisfaction related to panel dimension, it is more dominant impacted by the quality of the drivers it self. So i dont have to worry about reading any spesific book to think of my xo design and baffle shape iteration. Just get your saw and cut any plywood that you have, mdf is not OB territory.

Once you started OB, no going back to boxy speaker anymore but 1 OB iteration will never be enough. Trust me