My ported subwoofer

[vivek.saikia]

A pic of the enclosure: unfinished but good for some early listening tests.

Is it laminated MDF board?

 

[kapvin]

Thanks Kapvin, I have replied your PM.

This sub is designed with Martin's MLTL worksheet, so in theory it is a mass loaded transmission line. But due to the relatively small size, the effect of quarter wave loading will be minimal and I think it will behave more like a ported enclosure.

I collected the enclosure from the carpenter this morning, will post a pic soon.

i have sent you a .pdf on a mass loaded TL myself!

but I see you have progressed on your enclosure!!

fast work! hope to hear it when I am in bangalore around diwali

 

[t.antony]

Is it laminated MDF board?

It's more like a print on the MDF, there is no lamination.

 

[t.antony]

fast work! hope to hear it when I am in bangalore around diwali

You are welcome to come by; however there is lot to be done before I could commission this enclosure

• Build a 200w amplifier, I need to do some research in that area as I am looking for good gain from 16hz up
• Build an active crossover for the sub - design is in the protean stage.

Both the above tasks require making separate PCB's. Never done that before so the progress may be slow. Installed Eagle PCB and playing around with it now.

• Fiberglass coating/bracing and finishing of the sub enclosure. I thought will not try with fiberglass after my MTM project. But the versatility of the material keeps me going back at it

 

[Audiodoc]

Can you please post the designs of the amplifier and active crossover circuits.

 

[Beast_of_burden]

Hi Anthony,

Hats off to your motivation! I have a Behringer DCX2496 which is a digital active xover along with a whole bunch of cables. I had bought it a while ago during my Lowthers in OB days, let me know if you would like to borrow it for simulating whatever cross-over points you are considering.

 

[t.antony]

Hi Anthony,

Hats off to your motivation! I have a Behringer DCX2496 which is a digital active xover along with a whole bunch of cables. I had bought it a while ago during my Lowthers in OB days, let me know if you would like to borrow it for simulating whatever cross-over points you are considering.

Thanks, and again thanks for the offer.

I am currently testing with PC and basic xover testing is possible with a Foobar plugin.
It would be interesting to see what the Behringer can do, I will send you a PM once my subwoofer amp is ready.

Are you still using the OB Lowthers?

 

[t.antony]

Hooked up the sub for some early listening tests. My netbook + Creative x-fi USB sound card combo used as source with Foobar & foo_dsp_xover for crossing the sub and the MTMs. Integrating the sub was harder than I thought, had to try with many combinations of filter order, crossover frequency and sub positioning to finally get things sound right. At this stage the sub was crossed at 40Hz 2nd order(low pass) and MTMs at 50Hz 4th order(high pass).

IMO the sub improved the listening experience of songs with good bass tracks: rock and especially heavy metal tracks reveled more "body" with the bass guitar and drums. Bass Drums started to sound more tight and well defined with better attack. There was notable difference in listening experience with Iron Maiden, Ozzy and some old recordings like Hendrix. Pinkfloyd revealed a bit of low frequency content, tracks like Sorrow had plenty of creamy low bass, the low bass sort of passes through the body and gives a "being there feeling" to the track. Also, if the room gain is not handled sufficiently, bass will get muddied easily.

@Sonicbliss: From what I have noticed a shallow slope for the sub was good in integrating with the mains, it was not the case with the MTM as a steeper xover slope seemed better. There was some issues with room gain which disappeared when I placed the sub at 90 degree with the MTM. There is more to be tested but the lower xover slope seems to be working fine for the sub even with the ported MTMs.

Pics..

 

[grubyhalo]

Looking good there!

 

[sonicbliss]

@Sonicbliss: From what I have noticed a shallow slope for the sub was good in integrating with the mains, it was not the case with the MTM as a steeper xover slope seemed better. There was some issues with room gain which disappeared when I placed the sub at 90 degree with the MTM. There is more to be tested but the lower xover slope seems to be working fine for the sub even with the ported MTMs.

Good to know that even with ported MTMs an asymmetric slope gives better integration of the MTM-sub-room system.

For the Earl setup, the mains NEED to be run as sealed (and crossoverless) to get a shallow acoustic slope.
Ported MTM has extension but the slope is steep, probably thats why they didnt blend with a shallow slope on them.

You will then need to Eq the sub (never Eq the mains) for which measurement is needed at the lisening position to do it Try phase switch too on the sub.

Now, Earl actually recommends 3 subs so you may not be able to get the same success with a single sub, but his method will work better than any other approach is what I am assuming.

It is worth experimenting IMHO. You never know, the MTM-sub marriage may achieve higher sonic bliss in the room with his method.

Sonicbliss

 

[t.antony]

Good to know that even with ported MTMs an asymmetric slope gives better integration of the MTM-sub-room system.

For the Earl setup, the mains NEED to be run as sealed (and crossoverless) to get a shallow acoustic slope.
Ported MTM has extension but the slope is steep, probably thats why they didnt blend with a shallow slope on them.

The asymmetric slope between my MTMs and sub was an experimental step to bring the room gain under control and to smoothen out the overall response.

In the case of speakers fitted in a baffle, if we cross the lows and mids at different frequencies, the baffle will act as a pole in the xover to provide a smother acoustic rollover. Martin uses this method in some of his designs. I have followed the same rationale and considered the room gain as a pole to smooth out the gap between the xover points. Tried with symmetrical/asymmetrical slopes with xover frequencies up to 80Hz and then found my current combination to be the overall best as it did a good job with the room gain. The remaining room artifacts diminished further when I made a phase alteration by rotating the sub towards the side wall, phase switching was not that beneficial.

You will then need to Eq the sub...

Can you explain the rationale behind this suggestion. Why should I eq the sub and how will it help in better integration with my MTM's?

Now, Earl actually recommends 3 subs so you may not be able to get the same success with a single sub, but his method will work better than any other approach is what I am assuming.

It is worth experimenting IMHO. You never know, the MTM-sub marriage may achieve higher sonic bliss in the room with his method.

I have already tried with lower order xover and it did not fair well in my case. While I agree the merits of the Geddes method, the 3 sub setup you are suggesting is a bit out of scope for me

It might help if you could explain a bit about your current setup. What do you use as your mains and have you tried out any of the setups that Geddes recommends? I know someone in Hyd who will be interested in the type of setup you are suggesting.

 

[GeorgeO]

Antony

I'm a firm believer in the value of a powered sub with monitors, I've been using subs for the past decade, and if anyone tells me that to listen to 2 channel audio a sub is not needed, my answer is simple-I prefer it that way, period!

Having a good sub definitely enhances the listening experience IMHO.

 

[t.antony]

Antony

I'm a firm believer in the value of a powered sub with monitors, I've been using subs for the past decade, and if anyone tells me that to listen to 2 channel audio a sub is not needed, my answer is simple-I prefer it that way, period!

Having a good sub definitely enhances the listening experience IMHO.

Now I am a believer as well . May be those purists need to get an intimate experience with the lower octaves to understand what is being missed out.

 

[anilva]

Hooked up the sub for some early listening tests. My netbook + Creative x-fi USB sound card combo used as source with Foobar & foo_dsp_xover for crossing the sub and the MTMs. Integrating the sub was harder than I thought, had to try with many combinations of filter order, crossover frequency and sub positioning to finally get things sound right. At this stage the sub was crossed at 40Hz 2nd order(low pass) and MTMs at 50Hz 4th order(high pass).

IMO the sub improved the listening experience of songs with good bass tracks: rock and especially heavy metal tracks reveled more "body" with the bass guitar and drums. Bass Drums started to sound more tight and well defined with better attack. There was notable difference in listening experience with Iron Maiden, Ozzy and some old recordings like Hendrix. Pinkfloyd revealed a bit of low frequency content, tracks like Sorrow had plenty of creamy low bass, the low bass sort of passes through the body and gives a "being there feeling" to the track. Also, if the room gain is not handled sufficiently, bass will get muddied easily.

@Sonicbliss: From what I have noticed a shallow slope for the sub was good in integrating with the mains, it was not the case with the MTM as a steeper xover slope seemed better. There was some issues with room gain which disappeared when I placed the sub at 90 degree with the MTM. There is more to be tested but the lower xover slope seems to be working fine for the sub even with the ported MTMs.

Pics..

Antony,

Great and fast work. Very good looking sub. Did you do vinly laminate on MDF for the grain? My suggestion is to go for a ready made high efficiency plate amp for the sub, instead of building. My view is that you cannot add substantial quality to a sub amp by going the DIY route.

Cheers.

 

[gvenu]

Antony,

Great and fast work. Very good looking sub. Did you do vinly laminate on MDF for the grain? My suggestion is to go for a ready made high efficiency plate amp for the sub, instead of building. My view is that you cannot add substantial quality to a sub amp by going the DIY route.

Cheers.

Hello TAA,

Great Job. I missed this thread eralier and realized only after we talked a few days back!

I agree to Anilva. Instead of designing and building own amp, go for readymade solution and put that additional efforts in designing the active cross over. Integrating a Sub with mains for pure audio is not going to be that easy. The 2 channels with sub which I have listened at different places had/have timing issues. This may be another reason why there are not many 3way speakers around....From my limited knowledge

I know you will come out of all these technical glitches with all these efforts.

Wish you all the best

Venu

 

[GeorgeO]

I third Anil's suggestion. I went through the DIy route myself many eyars ago, getting a 200 wpc amp and a crossover kit from Marchand Electronics, but found the whole exercise quite a pain. I have since got a couple of plate amps and find that they work very well. I will only use plate amps in future.

 

[t.antony]

Antony,
Did you do vinly laminate on MDF for the grain?
Cheers.

The MDF board had the wood gain pattern printed on one side, it could have gone well with a clear coat. Now I might have to use some other finish since the carpenter was a bit careless and shaved off the prints on the edges thinking I am going to coat it with fiberglass similar to my MTMs :sad:

 

[t.antony]

Thanks Anilva, Venu & GeorgeO for the suggestion about getting a ready made amp. At the beginning of the project my thoughts were in the same lines - to get a good amp and if the inbuilt xover does not suit my purpose, try my hand at making the xover. Thought of going for Keiga KG5150 or KG5230.

As the project progressed, I came across some interesting information regarding bridged and bridged parallel gainclone amps and the diy bug again bit me . Found some useful schematics on the web using these chips and finally thought about giving it a try. There were some useful urls and inputs from the fellow member Goldy regarding the usage of these chips and tailoring them to suit my needs. I will post details about the amp later along with the planned schematics.

I suppose the DIY route for the amp be difficult than GeorgeO mentioned, as this is going to be a custom design and not a kit, procuring components and the other required stuff is not going to be easy for sure.

If things doesn't work as expected, there is always the option to buy a ready made unit . But if it does, the cost advantage on parts could be substantial.

 

[cmsajith]

You can try the Hypex UcD modules from ebay.com and an xover if you prefer class D amps.

 

[GeorgeO]

Like Antony, I'm also interested in knowing more about Sonicbliss' set up.