my first 3way Peerless loudspeaker....

[tcpip]

People, especially the majority of Indian DIY-community doesn't go my measurements....

I would hesitate to make this comment about the majority of Indian DIYers. After all, almost everything I have learned about DIY audio has been from other Indian DIYers more experienced than me, who are as scientific and thorough as they come.

I think the problem we are seeing with some Indian DIYers is with beginners. They do not have measurement setups, they do not know the fundamentals enough, and they embark on projects too ambitious for their knowledge. At the end of such projects, they have no choice but to say they love the sound. In their place, I would have done the same.

Let me make a confession here. When I was at that stage myself, sometime in 2002, I was so petrified of crossover design and MLS measurements that I actually bought one of the most expensive full-range drivers, hoping that I could just get a box built and get myself a usable pair of speakers without any of the complex stuff. I built it, and the drivers were outstanding (they were the Jordan JX92S) in the mid, but unsatisfactory in the highs and lows. I soon realised that I have to bite the bullet.

I am sure mpbraj is petrified of all these technical things today. I am just hoping that my critical comments of the approach he is is following will help him make a few less mistakes. After all, it's his money. I am sure that after a couple of speaker projects, he too will move from "sonics" and "subjective evaluation" towards a mix of measurements and listening, like we all have done.

 

[kanwar]

Well, I must admit that i haven't seen people here on HFV[with huge cluster of Indian Diyers] building projects by doing proper measurements, yes few exceptions are there where people do consider measurement part. What usually they do is they go by ears and ignore the measurement part and rest follows the herd mentality. My previous comment was in context with the Diyers over HFV.

If someone wants to shed some light or show measurement part and its necessity inthe project , he/she will be asked to get out of the typical "AES mentality" of measurement part and should better consider what the ears are listening. Without paying attention to the fact that sensory perceptions are plagued by variation of many individual factors itself.

I would love to see people evolving in better manner if they go by proper basic approach and consider measurements as a key to success. But that will never happen.

 

[kanwar]

I think the problem we are seeing with some Indian DIYers is with beginners. They do not have measurement setups, they do not know the fundamentals enough, and they embark on projects too ambitious for their knowledge. At the end of such projects, they have no choice but to say they love the sound. In their place, I would have done the same.

Some don't even want to learn.

Let me make a confession here. When I was at that stage myself, sometime in 2002, I was so petrified of crossover design and MLS measurements that I actually bought one of the most expensive full-range drivers, hoping that I could just get a box built and get myself a usable pair of speakers without any of the complex stuff. I built it, and the drivers were outstanding (they were the Jordan JX92S) in the mid, but unsatisfactory in the highs and lows. I soon realised that I have to bite the bullet.

It happened with me also, i think that is how we all evolved, but after i got my CLIO-10, the learning and experimenting became much more fun.

I am sure mpbraj is petrified of all these technical things today. I am just hoping that my critical comments of the approach he is is following will help him make a few less mistakes. After all, it's his money. I am sure that after a couple of speaker projects, he too will move from "sonics" and "subjective evaluation" towards a mix of measurements and listening, like we all have done.

Atleast in this thread, we are seeing the simulation part happening. The learning curve is steep but not impossible.

 

[kapvin]

Relative to other challenges you are facing and will face, I suggest that the port air speed worries are minor. Ignore it. See why your sim is not matching Kapvin's -- that is a bigger issue.

exactly.

@mpbraj;

we can size the port later. port velocity is, ceterus paribus, excursion dependent ; I do not see these woofer being very high xmax .. so basically, right now don't worry.

in the meantime, if you can post a snap ofthe first part of unibox where you have entered the specs, maybe I can see what is happening differently.

have fun

 

[keith_correa]

In my sims, I get Vb = 64.5 L tuned to 39.6 Hz. Port I.D. = 10.1 cm and length = 16.6 cm. This is using WinISD and Unibox is supposed to be more accurate. I agree with kapvin and tcpip - you are doing something differently.

 

[tcpip]

In my sims, I get Vb = 64.5 L tuned to 39.6 Hz. Port I.D. = 10.1 cm and length = 16.6 cm. This is using WinISD and Unibox is supposed to be more accurate. I agree with kapvin and tcpip - you are doing something differently.

@mpbraj, just attach the entire Unibox spreadsheet here -- people will quickly do your debugging for you. Online forums are so much fun -- people actually fix your mistakes for you if you give them the opportunity.

 

[tcpip]

Well, I must admit that i haven't seen people here on HFV[with huge cluster of Indian Diyers]....

Is there a huge collection of DIYers here? I see just one forum for DIY, out of so many. The rest are for people buying ready-made products.

Frankly, people who buy ready-made products and have never done DIY will almost always find it hard to understand technical aspects of "quality" of the things they buy. (Only someone who has messed around repairing his own car will know something about automobile technology quality, only someone who has cooked will know the superiority of one chef's work from the next, etc, etc...) Therefore, such people will tend to go by subjective listening judgments and may be ignorant about double-blind tests, etc. They will be vulnerable to snake oil stuff like mats on CDs to improve the sound and pine cones under the amplifier chassis to make the treble smoother, etc. They frankly "do not have the apparatus to know better", is how I would put it.

So, I would expect most people at HFV to have this subjective approach. Can't blame them. I would only hold DIYers up to higher standards, not the rest of the HFV crowd.

 

[kanwar]

Therefore, such people will tend to go by subjective listening judgments and may be ignorant about double-blind tests, etc. They will be vulnerable to snake oil stuff like mats on CDs to improve the sound and pine cones under the amplifier chassis to make the treble smoother, etc. They frankly "do not have the apparatus to know better", is how I would put it.
So, I would expect most people at HFV to have this subjective approach. Can't blame them. I would only hold DIYers up to higher standards, not the rest of the HFV crowd.

You said it all........ no offence to anyone but its the sad state to see here on HFV the people, who are after subjective approach without even knowing the technicalities behind the thing they are building.

 

[mpbraj]

Dear All, Thankyou very much for the responses....TCPIP/Kapvin, here is my unibox attachement....

regards...

 

[tcpip]

Dear All, Thankyou very much for the responses....TCPIP/Kapvin, here is my unibox attachement....

Now that we have the screenshots, what is your question? And does the forum allow you to attach the actual XLS file instead of these screenshots? That might speed things up.

 

[kapvin]

Dear All, Thankyou very much for the responses....TCPIP/Kapvin, here is my unibox attachement....

regards...

I cannot read anything. Rather pointless sending an entire worksheet screen shot which is not readable. What i asked for I asked for was the first part. You could have sent that or a link as tcpip suggested.

 

[mpbraj]

Kapvin/TCPIP, Sorry for that, here is my 2 unibox simulation screenshots...

h t t p://imagizer.imageshack.us/v2/1024x768q90/543/xg0n.jpg
h t t p://imagizer.imageshack.us/v2/1024x768q90/31/k2c4.jpg

thanks...

 

[keith_correa]

I would do this:

1. Set the linear cone drive to be 1.15. You can safely model with a 15% overdrive.
2. Model with Max SPL = 100dB
3. Set Qa = 40. UniBox's Heavy Fill sets Qa=5 which IMO is fully stuffed and is typical for stuffing in sealed boxes. Walls covered sets Qa=20 which IMO is a box thickly lined with dense lining. Lined with foam [which is usually the case] is typically set to Qa=40

With the above set appropriately, if Vb=~64 and port [single] dia.=10.1 you get a ~2dB peaking at the knee which IMO is fine. Setting Qa=5 [Heavy fill] gets rid of this peak but I doubt you will stuff this large a box.

Edit: I used 2 mm as the XMAX

 

[kapvin]

I would do this:

1. Set the linear cone drive to be 1.15. You can safely model with a 15% overdrive.
2. Model with Max SPL = 100dB
3. Set Qa = 40. UniBox's Heavy Fill sets Qa=5 which IMO is fully stuffed and is typical for stuffing in sealed boxes. Walls covered sets Qa=20 which IMO is a box thickly lined with dense lining. Lined with foam [which is usually the case] is typically set to Qa=40

With the above set appropriately, if Vb=~64 and port [single] dia.=10.1 you get a ~2dB peaking at the knee which IMO is fine. Setting Qa=5 [Heavy fill] gets rid of this peak but I doubt you will stuff this large a box.

Edit: I used 2 mm as the XMAX

I'd charitably take 3mm x-max-- after all, it's an 8"woofer

I'd also set the Qa between 40 and 80. you really don't want to stuff the box.

the peak is coming due to the added series resistance, which is pushing up effective qts. have you already sized the inductance required? or is that your buffer?

over the weekend (or over the week, if I have free time, I'll try to model this as an MLTL (but you should be sure of the woofer specs) and see how to best get rid of that peak. if you are going passive and you the DCR of the series inductance, in your crossover do let me know, it makes a big difference to the model.

cheers.

edit also let me know, for a 60 litres box, what were the box dimensions you were looking at?

 

[mpbraj]

Kapvin/Keith, Seriously, I can tell you, I am learning from the discussions you guys are having...I have never even thought of having the Xmax parameter, I was wondering where the Red line is on the "Peak cone Excursion" graph

regards...

 

[keith_correa]

I'd charitably take 3mm x-max-- after all, it's an 8"woofer

You're right. I missed the part where it was mentioned that it is a 8" driver. Had I known, I would have been more "charitable"

the peak is coming due to the added series resistance, which is pushing up effective qts. have you already sized the inductance required? or is that your buffer?

if you are going passive and you the DCR of the series inductance, in your crossover do let me know, it makes a big difference to the model.

IMO, 0.7 - 0.8 as a value for SR is fine. After all it has to take into account more than just the resistance of the x-over components. From Curt Campbell: It also needs to take into account the impedance of the amp output, resistance of the speaker cable, and increase in resistance due to the voice coil heating.

 

[Hari Iyer]

Joining in late in the discussion. Have stopped building a vented enclosure after moving to TL 5 years ago. TL usually are critically damps the driver by maximizing the acoustic output at the terminus.

For cross-over building the following points are important as per my experience,
1 Buying a good LCR meter which can accurately measure the inductance, capacitance and Resistance of the components. A tolerance of around 1% in the components should be aimed for as anything more than that would cause filter phase issues in the cross-overs.

2. Never use the nominal impedance of the drivers to calculate the filter values as they are just nominal and not actual impedance of the drivers. You will need to measure the actual impedance of the drivers either in a simulated response or ascertain it from the impedance curve of the data-sheet. The challenge here again is there would be tolerance in the datasheet and the actual impedance of the drivers.

3. Passive components adds phase shift to the filters and should be accounted for in the calculations.

4. Depending upon the order of the filters the filter phase shift between the woofer and tweeter should be relatively constant in the frequency range.

5. Flat SPL speaker system response seldom sounds good in a living room and will need to be accounted for diffraction, dispersion and reflection in the filters. BSC needs to be implemented for both mid and high-frequencies for fatigue free sound stage. Room contours and furniture also should be considered in the design as its DIY.

6. System impedance curve should be more or less flat for the woofer and should increase slightly for the tweeter for more control of the sound stage.

7. Depending upon the order of the filters the drivers should be selected. For instance for a first order filter the mid-woofer should have a response at least 2.5 octaves beyond the cross-over frequency. The acoustic roll-off of the woofer should also be considered and cone-breakup is very important for mid-woofers to prevent overall harshness of the sound stage. When designing the tweeter cross-over point the acoustic roll-off the tweeter needs to be considered while designing.
8. Tweeters should be crossed at least 3 octaves beyond the resonance frequency to prevent tweeter damage and fatigue.
9. Level matching between woofer and tweeter is most important to prevent masking of frequencies and have a proper transition between the two drivers.
10.The resistance of the woofer coil should also be considered while designing the L-pad to calculate the overall attenuation for the tweeter.
11.Zobel network also causes phase-shift in the cross-over frequencies and should be considered in the calculation.
12. BSC network causes phase-shift in the filter network and should be considered in the calculation.
13.Room contours should be considered for calculating the step required in the overall compensation. In a DIY its easy to do this as this is not a standard product.
14. Dispersion of the drivers and wave front are important for the overall sound stage.

Cheers and will add to the list later.

 

[Prasad Karpe]

Thank you Hari Sir, for this exhaustive information. It is you people who are giving us the much needed inspiration

 

[Prasad Karpe]

Hi Tarunji,
Thank you very much for sharing your insights regarding the speaker design. This thread is proving to be a good learning experience.
regards
Prasad

 

[kapvin]

Kapvin/Keith, Seriously, I can tell you, I am learning from the discussions you guys are having...I have never even thought of having the Xmax parameter, I was wondering where the Red line is on the "Peak cone Excursion" graph

regards...

So as promised I took a bash at doing a TL enclosure with your specs.

here is the modelled response.

[/URL]

Uploaded with ImageShack.us[/IMG]

it is a 65" line with a 11.667:1 taper (from 3.5 sd to 0.3 sd)

it is a biggish box but

.. no hump.
f6 is in the mid 20s
the rolloff will fill in nicely with room gain in a biggish room..so you should get essentially flat response in your room from 20hz.

this is modelled at 10w, and woofer excursion is at xmax or below all the way down to 20hz.

see if this works for you..