Thanks Jenson, I have not yet measured them that's why. I may measure after 2 weeks not to change anything, but only to check why I am enjoying so much music on them. There are nothing actually to modify as both the 8 inches are connected directly to the monoblocks with no filters or any compensation. The Ahujas gets an active LPF crossed at 250 Hz @ 24dB/ octave fed by my Denon AVR. As simple as it can get. I left all my crossover building skill away from this project.
Goodbye Permanent Magnet Speakers
- Thread starter Hari Iyer
- Start date
Could finally complete the OB speakers after padding at the rear side for reducing panel resonance. Also did a quick measurement as below.
The measured FR at listening position - The minimum phase is quite zero phase till 10KHz.
The below FR displays the roll-off of the individual drivers - I have bi-amped the Ahuja woofers with my Denon AVR.
Red - Only Full Rangers. There is no cross-over componentsThe roll-off is acoustic.
Green - Ahuja + Full Rangers. The Ahuja is bi-amped and level matched.
Blue - Ahuja + Full Rangers + Bolton H-frame subwoofer - Again level matched.
The measured FR at listening position - The minimum phase is quite zero phase till 10KHz.
The below FR displays the roll-off of the individual drivers - I have bi-amped the Ahuja woofers with my Denon AVR.
Red - Only Full Rangers. There is no cross-over componentsThe roll-off is acoustic.
Green - Ahuja + Full Rangers. The Ahuja is bi-amped and level matched.
Blue - Ahuja + Full Rangers + Bolton H-frame subwoofer - Again level matched.
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keith_correa
Well-Known Member
Hari, aren't you getting comb filtering given the responses of those drivers? See ~100Hz - ~320Hz.
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Keith, That's normal imo as the response below 320Hz is dominated by the room and unless you do serious room treatment you may not succeed. It could hamper with mid and high frequency by compression of response. This being a OB speaker, the loading to the room is minimal compared to other loading types. Even at the listening position the low and high Q point is within 15dB which is quite ok for a small room of around 180sqft. Moreover the distortion at these frequency which is of greater concern is below 5%. Atleast not audible to my ears.
keith_correa
Well-Known Member
If you have done a post filter and pre filter compare and there is no difference then it's fine, but if you have not then I suggest that you do a compare.
It's only a seed of doubt that I'm planting, I hope you take it further to bear fruit - whether that fruit tastes bland, sweet or bitter remains to be seen.
It's only a seed of doubt that I'm planting, I hope you take it further to bear fruit - whether that fruit tastes bland, sweet or bitter remains to be seen.
TBH, I don't understand what you mean by post filter and pre filter. The Ahuja is having a low pass filter at 250 Hz @24dB/ octave active. The H-frame subwoofer is crossed at 80 Hz again @ 24dB/ octave with a plate Amplifier. There is no aciive or passive filter on the full ranger and they are directly connected to the tube amplifier.If you have done a post filter and pre filter compare and there is no difference then it's fine, but if you have not then I suggest that you do a compare.
It's only a seed of doubt that I'm planting, I hope you take it further to bear fruit - whether that fruit tastes bland, sweet or bitter remains to be seen.
The roll-off image above is taken as below,
- measure first only the Full Range by keeping Ahuja and subwoofer amplifiers off.
- Turn on my AVR on and measure full ranger and Ahuja
- Turn on the plate amplifier and measure all fullrange + Ahuja + Subwoofer.
Individual measurements of all drivers independently though possible would be difficult and am not keen on doing this.
keith_correa
Well-Known Member
Ah! I understand now. I misunderstood before.
Hi Hari, can you please help with the model number of the Ahuja woofer? Is it this model L12-mb200? https://www.ahujaradios.com/speakers/professional-pa-speakers/l12-mb200.htmlLast week, i had purchased the Ahuja 12" woofer and assembled them on the existing OB baffle. I removed the H-frame subwoofer and mated the Ahuja with my 2004 Denon AVR using a low pass filter card purchased from Amazon. I am using a temproary wings on them as i have yet to complete my OB design as the woofers were undergoing break-in. This how they look now,
View attachment 52478
After using them for around 4 days, my wife asked me if these wings on both sides are going to be permanent and i said it would be integrated with the baffle. Needless to say these were poor WAF and they haijack the already cramped space in my living room. It appeared as if they were better off with the sub-woofer than these wings. I tried all possible tricks to convince them about the wings but she was not getting covinced. My daughter who was listening through the argument told me to put a folding wing and use them only when required and fold them in when not in use. I thought for 10 sec and thought it was a brilliant idea and i looked at my better half and she nodded her head in agreement.
I am sure the Bose 301 would have some female team member inputs in their design. The Bose 301 sub-woofers might be designed by his male team members and the satellite by his female team members. If you have completely male team designing your speakers then you have something like @prem JBL 4343
In your experience can this driver be used as a bass driver which can effectively reproduce bass for metal and techno music?
Yes, that's the model number. Don't go by the published specs, it's horriblely wrong. It has a peak of around +10 dB at around 1.5 kHz which is mentioned as 97dB SPL. Its actual low end response at around 400 Hz would be around 88 dB. You will need to know what you are doing when you are going to use them as woofer. Definitely will require measurements and simulations. Not plug and play.
I am using them for mid- bass between 100hz to 400 Hz. Below 100 Hz my subwoofer takes over, so this woofer works for me. I needed to use a 12 dB/ octave filter to tame the peak at 1.5 kHz. Not recommended for beginners.
I am not happy with the Ahuja 12" woofer because even though it is high SPL (97dB published) my 3 watts tube amplifier is just not able to drive them to get reasonable SPL to match the full range drivers. Not because the Ahuja themselves are bad but they are not suitable for my tube amplifier. Reason is it has a high moving mass of 70gms (composite paper cone + Kapton former copper voice coil) and is a high wattage 200 watts RMS (thicker coil used) PA speaker a perfect mis-match for my full-range driver. I tried everything possible to marry the both but could not succeed connecting everything to my tube amplifier.
What i am planning to do is change the paper cone and the voice coil with something very light weight and may be a paper former copper clad aluminium voice coil to reduce the MMS. I will also look for very thin voice coil as i am not looking for anything more than 15 watts of power handling. Also i shall be looking for a low compliance suspension as my box loading is OB. Tomorrow i am planning to visit couple of shops at Thane who do reconing of speakers but with my portable weighing machine to actually weigh both the paper cone + voice coil before finalizing them. I did some searching online and found only Altec 12" woofer to be around 30-35gms MMS. So my target will be around 30gms when finalizing the recone. I will need also to consider the weight of the glue and the spider to arrive at the final MMS. Hoping to get them around 35gms. Will update progress later.
Thanks for looking.
What i am planning to do is change the paper cone and the voice coil with something very light weight and may be a paper former copper clad aluminium voice coil to reduce the MMS. I will also look for very thin voice coil as i am not looking for anything more than 15 watts of power handling. Also i shall be looking for a low compliance suspension as my box loading is OB. Tomorrow i am planning to visit couple of shops at Thane who do reconing of speakers but with my portable weighing machine to actually weigh both the paper cone + voice coil before finalizing them. I did some searching online and found only Altec 12" woofer to be around 30-35gms MMS. So my target will be around 30gms when finalizing the recone. I will need also to consider the weight of the glue and the spider to arrive at the final MMS. Hoping to get them around 35gms. Will update progress later.
Thanks for looking.
I have most of the time driven the Ahuja's from my 3 + 3 watts tube amplifier. Also when new i had not breakin this woofer for more than 1 hour with my Denon AVR. So i thought why not try a breakin of this woofer with my subwoofer amplifier before going for a recone. I hooked only the Ahuja's to my subwoofer amplifier and with the sub volume almost at center position breakin started with freq as low as 10Hz sine wave. This for the first time helped move the cone to its full xmax. This cone is a very low compliance type (CMS 0.23 mm/Newton) and would not be happy even with this high volume at subsonic frequency. As i had nothing to loose as i had planned a recone, i tried using pink noise at subwoofer levels and then Tone Burst at 6Hz. This continued for almost 9+ hours over a span of 2 days/nights. The voice coil barely became warm even after two hours of continous pounding. This gave me an indication that this woofer is truly high wattage of 200 watts (published) unlike cheap Chinese literature. I did not give up and continued the pounding and only after 4+ hours i could slowly smell the enamel in the voice coil melting with heat. I immediately turned off the subwoofer amplifier and allowed the woofer to settle down for the next day pounding. I tried to physically see if there was any displacement of the cone by moving by hand and to my surprise i could now move the paper cone suspension assembly by hand which was dead stiff earlier. Next day morning, i repeated this process for another 5+ hours and finally allowed the cone to settle down. I am not sure how long this process should have been repeated and for how many days for loosening the suspension. I then connected them as usually with the crossover network to my 3 watts tube amplifier and did my measurements.
Hooray! The mid-bass is back as i wanted them, the OB roll-off which was at 400Hz got lower and now the -3dB roll-off is at around 100Hz. I did the rest of the setup and adjustments and gave them a listen for around 15 minutes before finalizing the design. I moved the subwoofer crossover now from earlier 280Hz to around 80Hz with improved low-end performance.
Shall post measurement results when time permits.
Thanks for looking.
Hooray! The mid-bass is back as i wanted them, the OB roll-off which was at 400Hz got lower and now the -3dB roll-off is at around 100Hz. I did the rest of the setup and adjustments and gave them a listen for around 15 minutes before finalizing the design. I moved the subwoofer crossover now from earlier 280Hz to around 80Hz with improved low-end performance.
Shall post measurement results when time permits.
Thanks for looking.
After a gap of almost 2 months, i finally concluded (hopefully -) my speaker tweaks. It took close to an year to arrive at the current avatar with many simulations, measurements and listening. The major challenge was at the top-end which gave me a sibilant sound no matter what i did. This took me close to 2 months to arrive at a solution. I am now using 32awg x 3 solid core brass wire for the full range drivers which helped me to tame the sibilant sound. If you look at the conductivity chart brass has a conductivity of around 28 compared to 100 of copper and 105 of silver. I have used these numbers to my advantage as this help me to time-align the high frequency with the lows and mids. Now the sibilant sound has vanished as they arrive in time with the mids and lows without compromise on the frequency response. Below are some measurements taken on the weekend.
-) my speaker tweaks. It took close to an year to arrive at the current avatar with many simulations, measurements and listening. The major challenge was at the top-end which gave me a sibilant sound no matter what i did. This took me close to 2 months to arrive at a solution. I am now using 32awg x 3 solid core brass wire for the full range drivers which helped me to tame the sibilant sound. If you look at the conductivity chart brass has a conductivity of around 28 compared to 100 of copper and 105 of silver. I have used these numbers to my advantage as this help me to time-align the high frequency with the lows and mids. Now the sibilant sound has vanished as they arrive in time with the mids and lows without compromise on the frequency response. Below are some measurements taken on the weekend.Will be trying an addressing the weak link in my OB speakers by replacing the Ahuja woofers. The Ahuja still dont have the drive from my tube amplifier and they need a high power amplifier atleast 20 watts+ to drive them - though they are quite good otherwise. There are plenty of 12" woofers to consider and all within my budget of 10K to 20K for a pair, but then again will face the same issue of drive even though they have a high SPL level on TS parameters. This could be because of the suspension and the Mms which for a 12" woofer will be above 55gms. A 3 watt tube amplifer cant drive such heavy cones at low power. So only option is to go vintage and this is what i did. Ordered a 12" Alnico paper cone woofer around 10 watts rated power typically used in an electric organ. The Mms for this driver will not be more than 20gms. I am not looking for a low bass with this 12" but something from 100Hz to around 600Hz with good drive. Expecting the shipment after 2.5 months around March end.
I received these 1@12" Alnico woofers 2 weeks ago but got busy for the past onne month with other very important priorities. I connected these woofers 10 days ago in place of the Ahuja but could not get them playing much. Last week got them Playing. I measured the SPL and got them to design table.
I done a series crossover cum compensation and the impedance is around 6 ohms.. previous was 2 ohms parallel. I have measured only the impedance yet. Listen for around 3+ hours. I am liking it very very much. The Alnico tone can get you mesmerizing. The Alnico play from 80 to 500, the fieldcoil from 400Hz to 3 kHz and the Russian from 2khz too 7 kHz and Telefunken Alnico above 7khz. The response below 80 Hz is handled by my H- framme OB sub. These speakers are very neutral, dynamic, mellow, accurate and have a huge soundstage. Image depth is spot-on and tonal balance perfect. It will be interesting to check if they also measure well as per simulated values. Let me see when this can be possible this week.
Thanks for looking.
I done a series crossover cum compensation and the impedance is around 6 ohms.. previous was 2 ohms parallel. I have measured only the impedance yet. Listen for around 3+ hours. I am liking it very very much. The Alnico tone can get you mesmerizing. The Alnico play from 80 to 500, the fieldcoil from 400Hz to 3 kHz and the Russian from 2khz too 7 kHz and Telefunken Alnico above 7khz. The response below 80 Hz is handled by my H- framme OB sub. These speakers are very neutral, dynamic, mellow, accurate and have a huge soundstage. Image depth is spot-on and tonal balance perfect. It will be interesting to check if they also measure well as per simulated values. Let me see when this can be possible this week.
Thanks for looking.
grindstone
Active Member
Appreciate the report and glad you are finding success, Hari. I think there are too many things happening at once for your experience to be understandably-transferrable for others to adopt. I think we could post many words about causality/testing, etc. but it would make for a lot of inefficient discussion. Everything is different, but I wish I could hear it, too (actually, I wish Everyone could). I'm still new here, but something tells me you are not done
Grindstone, thanks for your opinion. I listened for sometime yesterday and today and am fully liking what I heard. I am not able to get time to measure them - maybe will do this weekend. I am a measurement freak and for me FR, step response, overall impedance is very important parameters. Also getting a minimum phase response close to 0 deg till atleast 10 khz is top of my list. My listening area is quite small around 180 sqft so it will be difficult to get a clean impulse response due to reflections from room. Other parameters like RT60 around 300mSec and clarity above 90% are difficult in a smaller room.Appreciate the report and glad you are finding success, Hari. I think there are too many things happening at once for your experience to be understandably-transferrable for others to adopt. I think we could post many words about causality/testing, etc. but it would make for a lot of inefficient discussion. Everything is different, but I wish I could hear it, too (actually, I wish Everyone could). I'm still new here, but something tells me you are not done
If you happen to be in Mumbai area you can drop-in for a listen.
Took around 2 months to measure, design, assemble and fine tune the speakers. I re-designed a 3-way speakers from these drivers. It's a -12dB/ octave design. The topology is Hybrid crossover. Don't know if anyone building these design. The 2 x8" driver and 12" Alnico are in series crossover configuration and the 3" Telefunken Alnico's are in parallel to them. Impedance wise they are ok for this topology.. The crossover points are 300Hz and 3450Hz. The OB delivers till 60 Hz -3dB where the subwoofer adds one more octave below. I at times don't turn the sub on depending upon the gener of music that I am listening as I am not a bass head and shall prefer overall coherence and transparency over more bottom end.
Shall post images as time permits.
Shall post images as time permits.
Posting some simulated and measured images for the benefit of DIY community
The below are the simulated results from the original design last month,
From the above simulation, below is the measured results,
There was an increased energy in the mid-range in subjective listening from 700Hz till 3KHz region as confirmed by the measured results. I needed to fine-tune to reduce this shout in the mid-range. Interestingly the simulated response displayed flat response though.
Modified cross-over after fine-tune:
The simulated response show a deep null from 300Hz till 2KHz but the below measured response is somewhat flatter at the mid-range.
The subjective listening also gives a more mellow response with a smooth presentation of the midrange without any masking of any frequency.
All the above measurements are without my sub-woofer engaged and mic at the top driver at a distance of around 1 meter.
I have yet to measure at my sweet listening spot with both speakers on.
Thanks for looking.
The below are the simulated results from the original design last month,
From the above simulation, below is the measured results,
There was an increased energy in the mid-range in subjective listening from 700Hz till 3KHz region as confirmed by the measured results. I needed to fine-tune to reduce this shout in the mid-range. Interestingly the simulated response displayed flat response though.
Modified cross-over after fine-tune:
The simulated response show a deep null from 300Hz till 2KHz but the below measured response is somewhat flatter at the mid-range.
The subjective listening also gives a more mellow response with a smooth presentation of the midrange without any masking of any frequency.
All the above measurements are without my sub-woofer engaged and mic at the top driver at a distance of around 1 meter.
I have yet to measure at my sweet listening spot with both speakers on.
Thanks for looking.
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After a long time modified my speaker cross-over a bit and adjusted level of lows and highs vis-a-vis mids at 1W/1M to get a slightly downard slope. My listening position will have a roll-off around -6dB/ octave at 20KHz with this setup. Here are the curves,
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