Planning a new open baffle design with All Ahuja components

[jaudere]

Hi folks,

I am planning a new open baffle design using wide range drivers.

Can someone please comment how the following drivers will perform on 20"-24" baffle?

Ahuja Sound Solutions

Ahuja Sound Solutions

I am planning to cross them with tweeter at 4KHz. Will decide about adding woofer after initial listening tests.

Can anyone suggest a good matching tweeter for it?

Can someone please tell me if I can get L-pad ay 8 ohm in india? I may choose this as tweeter

Ahuja Sound Solutions

Its sensitivity is 10 dB is higher than the above mentioned wide range drivers. I will need L pad to attenuate the HF driver significantly.

In addition, can someone mention anything about Piezo tweeters?
This could be a choice for me

Ahuja Sound Solutions

Ahuja Sound Solutions


Thanks.

 

[jaudere]

Re: about tweeter

I read some interesting and important information.


1)most of us know that due to ageing there is high frequency hearing loss but how much???: yesterday I read that at 8khz, average loss is about 10db at age of 35yrs. The study involved frequencies from 2.5k to 8khz. The investigators expected similar outcome for frequencies above 8khz.
In fact they said that music testers who are above 35 yrs may actually call a bright speaker as 'neutral' because of this issue.

My age is 34 now. So it should be ok if I choose a tweeter which is 8-10 db more sensitive that the woofer without using L pad to attenuate tweeter.

2) I went through frequency ranges of various musical instruments and human voice.
The highest was cymbal ,just touching 16khz. Everything else was well within 15k.

Secondly, the treble knob on most of the amplifier including good ones like the marantz pm 6002 that I have, pushes up the band at 10khz and not 16khz or so. It seems to work well for home use.
So it should be ok if i use compression driver with frequ response 3k to 15khz.

The issue is cost. The compression horn 20w rms reaches 15khz while the new one is 80w rms and reaches 18khz. The 20w costs 1100 while 80w costs 4300
However the articles that I read yesterday were kind of soothing for me.

 

[Thad E Ginathom]

It is an interesting experiment to sit, with your headphones and a computer and, using something like Audacity (or maybe there is a simpler tone generator) and play tones to yourself. There are sample files that can be downloaded that sweep over the audible range, and you can note just exactly where yours cuts out. Please note, of course, that this is meant to be an interesting experiment in sound, not a diagnostic of our hearing.

I have suffered from high-frequency hearing loss for as long as I can remember. Not that I was aware of that at the time, but once having learnt about it, I can see that, even at 20, I was unable to focus one voice in a crowd, and just a decade or so later I was suffering confusion with p,b,d,t sounds. Now, at nearly 60, it can be hard work having a conversation with me if there is any background noise at all.

What's the point of this waffle about my ears? Just that, going back to where I started, when I test myself, I'm amazed how far up the scale I can hear something! So don't give up on those higher frequencies yet, especially not on the simply-theoretical basis of your age.

 

[jaudere]

The loss in not complete loss but reduced sensitivity. So if you play the higher frequencies bit loud, you can hear them at advanced age also.


By the way, here are the links to what I was talking about:

Interactive Frequency Chart - Independent Recording Network

The Frequencies of Music - PSB Speakers

As first step in my experiement, i have bought the 12" full ranger by Ahuja. As expected , it is a wide band speaker and not full ranger.

1) I tried it as full ranger: not going to be good. Will need support at higher and lower end.

2) Crossed to a Philips silk dome tweeter at 4 khz. The tweeter seems to have significantly lower sensitivity as compared to the Ahuja full ranger. So the combination was better than the full range driver alone but still the mids were overpowering. This improved drastically when I turned up the Treble knob on the amp to 3 o'clock position (this pushes the things up at 10khz)

So I need to buy compression driver as planned.

The sound was great. The bookshelves that I was using for last few months with very good results(or so I thought) appear lifeless in comparison to open baffle even though the open baffles are weaker in bass. The open baffles are too good for vocals and makes the song alive. This is what even my wife felt.

3) Just out of curiosity, the full raner was fed through 250hz low pass filter. It was very good for bass as well (not thumping bass though but don't listen to that kind of music. I tested it today with Rahat fateh ali Khan and Kailash kher).

So the plan is
2.5 way design.

1) Full-ranger crossed to horn loaded compression driver at 4 khz making it a 2 way design

2) Supplementing the full ranger with bass driver below 250Hz. The bass driver will again be full ranger(same model). So the integration with the mid will be better due to similar sonic characteristics.

3) baffle size 20" X 40". The bass of the full ranger should roll off at 200Hz with baffle width of 20"

I plan to have flat baffle for mid driver and folded baffle for bass driver with wings of 8" each, giving a total baffle width of 36" for bass driver: Will go lower upto 80 Hz, which should be adequate for me.

Let us see how the things develop.

 

[goldyrathore]

1) Full-ranger crossed to horn loaded compression driver at 4 khz making it a 2 way design

IMHO at 4k, the tweeter is crossed too high for the CTC between the 12" mid and tweeter. The lowest the tweeter can be crossed as per the specs is 2.5k 3rd order. This too is very high for the CTC. The following seems to be better suited than the one you plan to use Ahuja Sound Solutions

2) Supplementing the full ranger with bass driver below 250Hz. The bass driver will again be full ranger(same model). So the integration with the mid will be better due to similar sonic characteristics.

In OB/dipole the 12" driver may be a good midbass but has a very low xmax for bass duty, I would suggest a 15" instead. Though I dont know whether you still can have a 2.5way then.

In addition, can someone mention anything about Piezo tweeters?

And forget those piezos. They are very good VFM but cant be crossed that low that this application demands.

Hope it helps.
Regards,
Goldy

 

[t.antony]

For 2 or 2.5 way, you will need baffle step correction. Without it midrange gain from 200Hz to the tweeter crossover point would be hard to control. Here is an easy to implement circuit - Baffle Step Compensation

For 2.5 way the LF driver can be crossed below 100hz - I crossed my Ahuja LF15 drivers at 60Hz with a fullrange driver.

The ideal crossover point for the 12" driver would be around 1KHz, crossing it above will make the transition between woofer and tweeter difficult. Also keep in mind that in the 2KHz - to 4KHz region ears are very sensitive and you would not need a 12 driver to radiate that part of the spectrum for a home setup.

Tweeters that can be crossed near 1.5KHz are pretty expensive. I would like to suggest something simple. Try to get a 3 or 4 inch full-range speaker(the types that's used in television sets). Use it for the spectrum between 1Khz to 5Khz. And above that you can use the compression driver or the Phillips dome you have indicated. This will make the system a 3.5 way though...

 

[Hari Iyer]

It is an interesting experiment to sit, with your headphones and a computer and, using something like Audacity (or maybe there is a simpler tone generator) and play tones to yourself. There are sample files that can be downloaded that sweep over the audible range, and you can note just exactly where yours cuts out. Please note, of course, that this is meant to be an interesting experiment in sound, not a diagnostic of our hearing.

I have suffered from high-frequency hearing loss for as long as I can remember. Not that I was aware of that at the time, but once having learnt about it, I can see that, even at 20, I was unable to focus one voice in a crowd, and just a decade or so later I was suffering confusion with p,b,d,t sounds. Now, at nearly 60, it can be hard work having a conversation with me if there is any background noise at all.

What's the point of this waffle about my ears? Just that, going back to where I started, when I test myself, I'm amazed how far up the scale I can hear something! So don't give up on those higher frequencies yet, especially not on the simply-theoretical basis of your age.

If you suffer from hearing loss due to constant exposure to noise or even listening to music at high SPL, then i can suggest you one exerise which you should do every day twice (morning and evenings)for 2 minutes on each ear.

Put your index finger inside your ear and rotate your index finger inside your ear to give exercise to the minute fibers situated in the inside of your ears. This will also help increase blodd circulation for your ears. The idea is to keep the cells of your ears intact so as to prevent high frequency loss over age.
Do this exercise for couple of weeks and PM me the response after 3 months. I will be eager to know.

 

[Thad E Ginathom]

Thanks for the idea, but the tiny hairs that you actually hear with are way inside your inner [middle?] ear. It's these that suffer, and, like the ones on our head, once gone, never grow again.

Here's a bit of old UK folklore, aimed at stopping children damaging their ears: never put anything in your ear, except your elbow.

By the way, here are the links to what I was talking about:

Interactive Frequency Chart - Independent Recording Network

The Frequencies of Music - PSB Speakers

Useful stuff. I found the former when investigating this stuff a couple of weeks back. It is amazing how low on the scale most of the stuff that is nominally useful to us actually is. And those very high tones? something more of a hiss than a whistle! Would music suffer without them? Probably not ... but I suppose every harmonic is part of the picture.

 

[jaudere]

Thanks a lot for your inputs guys.
I think after reading your posts and some more information, i have understood the beaming,comb filter effect and the high cross over point issue associated with my planned design.

So I need to consider some changes. I have 2 options.

1)Cross the ahuja full ranger with tweeter at 1khz. 2 problems. First, I have a cross over at 4khz. I would like to utilize it as far as possible. Secondly, where can I get cross over at 1 khz. I dont want to put efforts into making one.
In this approach, can i use a 3" full range driver used in multimedia speakers in place of tweeter. So this full ranger will play everything above 1khz and ahuja plays everythin below it.

2) Using the present crossover of 4 khz. I can use 3 or 4" fullranger and cross it with tweeter at 4 khz. So this full ranger player from bottom to 4k.
The Ahuja will still assist the full ranger below 250hz.
In this approach, i fear that the smallish full ranger may be damaged by frequencies below 80-100hz.
So how do i protect this small full ranger? Is it as simple as putting appropriate capacitor in series between the crossover out and the speaker? Or putting a cap here will change the crossover point itself?

If i want to avoid this complication, which is a 4" full ranger with robust build which will not get damaged
by lower frequencies?

 

[jaudere]

here is a separate post post for separate confusion.

For a baffle of 20" is putting a 12" speaker same as 4" speaker for lower frequencies?

I mean in this situation, if i put 12" speaker then 4" of baffle is left on either side. If i put a 4" speaker, 8" baffle width is left on either side. So won't a 4" speaker give better bass production(albeit at lower volume) as compared to 12" one?

This proposition is wrong if all the sound waves originate from centre of the speaker(which is likely because the voice coil is in centre). Gurus,please enlighten me.

 

[Hari Iyer]

Thanks for the idea, but the tiny hairs that you actually hear with are way inside your inner [middle?] ear. It's these that suffer, and, like the ones on our head, once gone, never grow again.

Here's a bit of old UK folklore, aimed at stopping children damaging their ears: never put anything in your ear, except your elbow.
Useful stuff. I found the former when investigating this stuff a couple of weeks back. It is amazing how low on the scale most of the stuff that is nominally useful to us actually is. And those very high tones? something more of a hiss than a whistle! Would music suffer without them? Probably not ... but I suppose every harmonic is part of the picture.

I do agree that the tiny hairs are inside the middle ear. I have read the above excersie in the web where putting the index finger in the outer ear and rotating the index finger helps to solve all hearing problems. Its a Yogic excersise prescribed for hearing ailment. Care should be taken not to put the finger inside the inner ear but only on the outer ear.

Cheers, Hari.

 

[Hari Iyer]

Hi folks,

I am planning a new open baffle design using wide range drivers.

Can someone please comment how the following drivers will perform on 20"-24" baffle?

Ahuja Sound Solutions

Ahuja Sound Solutions

I am planning to cross them with tweeter at 4KHz. Will decide about adding woofer after initial listening tests.

Can anyone suggest a good matching tweeter for it?

Can someone please tell me if I can get L-pad ay 8 ohm in india? I may choose this as tweeter

Ahuja Sound Solutions

Its sensitivity is 10 dB is higher than the above mentioned wide range drivers. I will need L pad to attenuate the HF driver significantly.

In addition, can someone mention anything about Piezo tweeters?
This could be a choice for me

Ahuja Sound Solutions

Ahuja Sound Solutions


Thanks.

By looking at the TS specification and the Frequency domain chart, i would rather go in for a TL type enclsoure or a Aperiodic box so that the mid-range response of these drivers can be used till 4 KHz. The TL enclsoure is also a close approximation to the open baffle design in a way. I would prefer the 12" driver over the 15" driver due to the lower resonating frequency. The cross-over will have to be compensated for high-low Q points with a parallel Notch filter in the frequency ranges else could sound harsh.
Try using a exo-linear design for the TL with proper damping which should be more suitable for this driver.

 

[jaudere]

By looking at the TS specification and the Frequency domain chart, i would rather go in for a TL type enclsoure or a Aperiodic box so that the mid-range response of these drivers can be used till 4 KHz. The TL enclsoure is also a close approximation to the open baffle design in a way. I would prefer the 12" driver over the 15" driver due to the lower resonating frequency. The cross-over will have to be compensated for high-low Q points with a parallel Notch filter in the frequency ranges else could sound harsh.
Try using a exo-linear design for the TL with proper damping which should be more suitable for this driver.

Wow!
That becomes very complicated for me. I don't think i can put so much time and effort in doing this.

By the way the tiny hair that you and Thad are talking about are situated in something called Cochlea, which is part of internal ear along with the vestibule(which controls our balance along with the cerebellum)
Middle ear is just an air filled cavity that contains the ossicles or the tiny bones of the ear. I am a doctor so I know these things a bit more. But don't ask me further. I am not ENT specialist

 

[jaudere]

polarity issue

I had a query. Suppose that I am running a full ranger supplemented by a woofer below 250hz. The woofer is fed through a low pass filter with a slope of 12 db/octave.
Should I reverse the polarity of woofer terminals(connect negative of low pass filter to positive of woofer and vice versa)? Is this step necessay to maintain full ranger and woofer in phase?

 

[jaudere]

Here is next question:
I have a full ranger. Assisted in higher frequencies by tweeter above 8khz with a high pass filter. Full ranger is 8 ohm. Tweeter is 4 ohm. Crossover is 2nd order.
Is this going to damage my amp by any chance? My logic says no. The high pass filter being very high i.e. 8khz and 2nd order,and most of the music being below 7khz, I think that the final impedeance of the system should be more than 4 ohm(the high pass filter will cause the impedance of the tweeter to be very high for anything below 7khz).
I would like experts to chip in.

 

[jaudere]

Here is further step in my experiment.
1) I ran full ranger without any cross over. (I have left the combing effect aside as of now ) .
2) I bought a car front speaker:ultimate T2-4021 4ohm 2 way with frequency range 65hz to 22khz. I was interested in 1khz and above only. The horn compression drivers fitting in my requirement were very costly and going out of budget . I could not find any tweeter that can be crossed down at 1khz. So this was a middle way. A pair for 2k.

3) I have a high pass filter at 4khz for 8 ohm. If it is connected to 4 ohm speaker, it automatically works at 8khz. This was I good thing for me because my full ranger behaves well till 10khz.

The result? Weaker in bass as compared to my bookshelf but far far superior as far as overall sound is considered. In fact after hearing this new speaker i understood that I could never hear some percussion instruments in the song 'tere mast mast nain' before. Especially the tabla. All these days I had noticed the dagga part only. So details and separation is much better.
I am running open baffle on 1 side and bookshelf on the other side with my Marantz. I just turn the knob of right and left balance to compare the two speakers. Need some volume adjustment to have equal loudness. Compared this way, the book shelf appears quite muddy and this is the same speaker which i love when not being compared to the open baffle.

 

[sashijoseph]

I had a query. Suppose that I am running a full ranger supplemented by a woofer below 250hz. The woofer is fed through a low pass filter with a slope of 12 db/octave.
Should I reverse the polarity of woofer terminals(connect negative of low pass filter to positive of woofer and vice versa)? Is this step necessay to maintain full ranger and woofer in phase?

The correct way of doing it would be to throw a LP filter for the woofer and a HP filter for the full ranger at 250Hz.
If the LP and HP filters are 2nd order,the individual high pass and low pass sections would be 180 deg out of phase and when summed together would produce a deep null at the xover frequency.
Thus one of the sections is wired in reverse polarity so that the null is avoided and the filters sum to a +3dB hump.

But remember,this characteristic is for the electrical summation.When the drivers sum acoustically they would mimic this electrical summation only if both drivers radiate coincidentally ie with no vertical or horizontal offset.

So how the drivers sum acoustically would depend on the horizontal offset between the drivers(besides some other factors) and for some particular offset the reverse polarity might actually provide a null instead of the normal polarity wiring.

So try both connections and see whether you can make out a null somewhere around the xover point.

 

[quad]

But remember,this characteristic is for the electrical summation.When the drivers sum acoustically they would mimic this electrical summation only if both drivers radiate coincidentally ie with no vertical or horizontal offset.

Sashi, thanks for the explanation. So there is an advantage to
this kind of coincident tweeter mounting...

The pic is from a discussion in the diyaudio full range forum-

Hexagon Pioneer B20FU20 Enclosure - Page 19 - diyAudio

 

[sashijoseph]

Here is next question:
I have a full ranger. Assisted in higher frequencies by tweeter above 8khz with a high pass filter. Full ranger is 8 ohm. Tweeter is 4 ohm. Crossover is 2nd order.
Is this going to damage my amp by any chance? My logic says no. The high pass filter being very high i.e. 8khz and 2nd order,and most of the music being below 7khz, I think that the final impedeance of the system should be more than 4 ohm(the high pass filter will cause the impedance of the tweeter to be very high for anything below 7khz).
I would like experts to chip in.
Reply With Quote

IMHO,since you do not have a LP filter in place for the full ranger,at frequencies above 8kHz(and upto the rolloff point of the full ranger),the amp would see a load of both the drivers in parallel ie ~2.7 ohms.

 

[sashijoseph]

Sashi, thanks for the explanation. So there is an advantage to
this kind of coincident tweeter mounting...

yes Quad,this would definitely present an advantage,but a perfect electrical to acoustic mapping is possible only if, apart from the coincident radiation
1)the individual drivers have a flat impedance magnitude(calls for resonance traps,conjugate filters etc to tame the impedance curves).

2)the individual drivers have enough bandwidth extending ~2 octaves beyond the xover point.

But with computer xover optimizers one can arrive at a near perfect acoustic summation even if drivers do not comply rigidly to the above conditions.

Without response measurements and computer simulations,one would have to grapple with the above conditions in order for the xover to behave as expected.