Why are most speakers rear ported instead of front ported ?

[Decadent_Spectre]

Many years back, I was building a multiway speaker and mulling over cabinet volumes and the woofer cabinet port size left me little choices. I remember reading a lot on port placements back then, Rear ported, Front ported, downward firing and upward firing (Yes, I did a dual port upwards firing subwoofer cabinet in high school for push pull two 12" driver size design, from an article from a famous American Audio magazine, back in 1990s, with a sizable low end down to 16Hz ! You read right, the DIYer mentioned that his socks would slip down gradually.... though paucity of funds back in school never saw an amp to drive the sub)

A front ported if mated well with the bass driver, is most desirable, else rear ported is designed so that it does not garble the midrange.... This is what I remember reading... learning.

Regarding PA drivers, the India scene is mostly silly and all about loudness at the expense of distortion, however I have had maximum fun using some nice PA brands, Fane, PRV, Faital Pro and Beyma. I would prefer them over pricey home audio drivers any day......

The specs and response curves are accurate and honest.... I consider them high VFM.... And for low wattage home usage compared to high wattage brutality they are designed to take, the distortion figures are just very fine... (Try playing them form flea power tube amps and see the magic they bring)

Just sharing my experience.... Looks like specializing in 'Nuclear Science" could be easier than mastering vagaries of "acoustics" and "sound reproduction". I have, may be learnt just 1% so far.......

While I agree about Fane, Faital and Beyma, are you sure PRV deserves to be on that list? PRV tends to be popular for OB speakers on a budget if I am not mistaken. In my humble opinion if one wants a pro woofer today (don't know about the future) the best options are Faital,PD,Beyma and RCF. Of course the suitability of these brands for OB are questionable as I have never investigated it, perhaps PRV and/or Eminence are more suitable here. There is also Acoustic Elegance.

Unfortunately, I don't know of anyone except @Decadent_Spectre, who uses a well tuned (to his tastes) pro audio-based speaker set up at home. I too am looking for some one nearby who has a good pro audio driver-based set up to experience it live. But I haven't found any one yet.
My interest in the pro audio driver-based setups was piqued by many experts on diyaudio forum moving towards such systems from regular hifi driver-based setups. Hence I started learning more about them.
It is also hard to get reasonably good quality drivers in small numbers in India.
Recently I had asked a Faital pro distributer in india about availability of some drivers and most of the good ones I wanted are not available at the moment.

However when an opportunity presented itself, I grabbed a pair of 15inch Faital pro 15PR400 drivers (the same drivers used in the calpamos speaker build by tony gee in one of the above videos) for a future DIY build.
My current thought is to pair the above driver with a 1inch or 1.4 inch compression driver loaded on a CE360 or CE460 waveguide by Mabat (after asking him which one suits this woofer better) in a free standing configuration like shown in attached pic 2 (a study about which was done by FM fluid on diyaudio forum). This will be a DSP crossover based active system.

So maybe in time, i will have atleast an experimental pro audio based set up ay my home.

Hi Vineeth, it is so good to hear you bought the Faitals! I am sure you will be very happy with them. Which driver was unavailable at the local distributor? Have you bought the CD yet?

Just a humble reminder, please do experiment with foam, ala Geddes! Also in speakers with a ported midrange/woofer, plugging the ports will drastically change the sound, you could try this too to see if it is to your liking. IME it becomes too lean for my tastes but the clarity and detail increases are off the charts and may suit some.

 

[aeroash]

You might find this difficult as most users in India do not use pro speakers at home. I assume you wanted to listen to pro speakers in a home setup as you have heard them in an outdoor setup.

Yup. PA speakers. I mentioned PA setup because I assumed they would be driven by PA amps, probably with a DSP in the chain.

 

[Decadent_Spectre]

Yup. PA speakers. I mentioned PA setup because I assumed they would be driven by PA amps, even in a home setting.

Professional setups should be driven by professional amps in my view. What is the point of all that output capacity if you limit it to a 1-2W tube? You are throwing away so much capacity by doing this, though for some the allure of pro style systems can be their sensitivity allowing them to gain reasonable volume with low power tubes.

 

[Vineethkumar01]

Vineeth, it is so good to hear you bought the Faitals! I am sure you will be very happy with them. Which driver was unavailable at the local distributor? Have you bought the CD yet?

Just a humble reminder, please do experiment with foam, ala Geddes! Also in speakers with a ported midrange/woofer, plugging the ports will drastically change the sound, you could try this too to see if it is to your liking. IME it becomes too lean for my tastes but the clarity and detail increases are off the charts and may suit some.

Hi @Decadent_Spectre

I wanted to buy 12 PR320 and 15HP1020. 15 inch one is too pricey But the 15PR400 was the one in stock and available at a justifiable price. I asked soundland.in
Not yet finalized in CDs. I want a pair of faital HF1440, but not able to get one. Then tried HF108, which is not available now. What is available is HF107 and HF146. Also looking around for BMS and Celestion CDs.

I will definitely try the foam method by Geddes but on Mabat's waveguides it may not be necessary if the CD is good, as Earl Geddes himslef seems to have remarked in that thread, I think. Anyway, we'll see..

 

[Decadent_Spectre]

Not just reasonable, very very loud with just a watt or two…. (With so many other good things audible)

I think very loud is dependent on taste, I would find 1-2W severely lacking.

Hi @Decadent_Spectre

I wanted to buy 12 PR320 and 15HP1020. 15 inch one is too pricey But the 15PR400 was the one in stock and available at a justifiable price. I asked soundland.in
Not yet finalized in CDs. I want a pair of faital HF1440, but not able to get one. Then tried HF108, which is not available now. What is available is HF107 and HF146. Also looking around for BMS and Celestion CDs.

I will definitely try the foam method by Geddes but on Mabat's waveguides it may not be necessary if the CD is good, as Earl Geddes himslef seems to have remarked in that thread, I think. Anyway, we'll see..

The 15PR400 is a great driver, you made a good choice. If the budget accommodates BMS is well reputed. If you don't mind climbing higher, there is TAD. Celestion is of course also an excellent option.

The foam (other than "HOMs") my help a lot in taming the harshness of the sound and rolling off the top end which may be beneficial in a domestic setting. I look forward to your projects coming to fruition, if you do post graphs I ask you to please also post the phase and impulse graphs!

 

[liverpool_for_life]

But I haven't found any one yet.

I'm right here. Admittedly, a 6-hour drive may not qualify as close. HST, where there's a speaker you may want to listen to, there's a way.

AFAIK, my Catalysts use an 8" BC&C coax and a pair of customized 8" AE woofers. The playback capability (music/pink noise with all 3 drivers active) for the Catalyst 12Cs (the big brother of what I have) is around 130-133 dB at 1m. Mine are not quite as capable from an output perspective, but they aren't too shabby either. Invitation open to aeroash as well.

 

[aeroash]

I'm right here. Admittedly, a 6-hour drive may not qualify as close. HST, where there's a speaker you may want to listen to, there's a way.

AFAIK, my Catalysts use an 8" BC&C coax and a pair of customized 8" AE woofers. The playback capability (music/pink noise with all 3 drivers active) for the Catalyst 12Cs (the big brother of what I have) is around 130-133 dB at 1m. Mine are not quite as capable from an output perspective, but they aren't too shabby either. Invitation open to aeroash as well.

Awesome! Will get in touch. Thanks

 

[Vineethkumar01]

I think very loud is dependent on taste, I would find 1-2W severely lacking.



The 15PR400 is a great driver, you made a good choice. If the budget accommodates BMS is well reputed. If you don't mind climbing higher, there is TAD. Celestion is of course also an excellent option.

The foam (other than "HOMs") my help a lot in taming the harshness of the sound and rolling off the top end which may be beneficial in a domestic setting. I look forward to your projects coming to fruition, if you do post graphs I ask you to please also post the phase and impulse graphs!

Thanks @Decadent_Spectre
I am looking around for CDs. Will keep these brands in mind. As you said the foam will help in taming harshness. Usually harshness can be caused by break up modes of the CD and polar pattern flips due to diffraction. The speciality with Mabat's waveguides is that given a good driver with benign break ups, his waveguide is supposedly the best available one right now that tames diffraction to the best known possible extent due to the oblate spheroidal horn profile and his seemless horn mouth termination contour in the free standing configuration. This is why I think Earl Geddes said foam might not be required with this waveguide. But since I am new to all this, there might be some detail that I have missed and would have to find out issues with experimentation and more learning. Hence I will definitely keep the foam suggestion in mind.

Regarding development of overall acoustic concept (with crossover), I have attached a sample development chart that I use with VituixCAD, which will have all details that one can ask for. This is captured using a semi-dual channel measurement set up. It will have impulse response, step response, ETC, SPL magnitude and phase, excess group delay, power response, horizontal and vertical directivities, filter target transfer functions etc. So we are covered on the graphs front. Only thing is I will have to take 180degree horizontal polar measurements (won't probably need vertical due to the symmetries involved in the construct). I will do this with a turn table I have. All this effort so that we are fully insured and confident on the measurements front. Next step would be listening impressions and tuning, which is where the devil lies..

Hopefully I will get a cabinet built for the woofer, which is where my projects get stuck often due to me having no time to do woodworking and all friends who know that being busy. Will start a thread and keep updating progress once this starts.

 

[Vineethkumar01]

I'm right here. Admittedly, a 6-hour drive may not qualify as close. HST, where there's a speaker you may want to listen to, there's a way.

AFAIK, my Catalysts use an 8" BC&C coax and a pair of customized 8" AE woofers. The playback capability (music/pink noise with all 3 drivers active) for the Catalyst 12Cs (the big brother of what I have) is around 130-133 dB at 1m. Mine are not quite as capable from an output perspective, but they aren't too shabby either. Invitation open to aeroash as well.

Thanks a lot for the invitation..
Will try and contact you next time I am in Chennai..

 

[k-pad]

That's such a lovely question @Nitin K bhai!
And some very lovely answers.
It is sad that it got derailed into another topic - pro vs consumer audio.

And I do agree with the person who said that after post 37, it needed to be branched out. Mods may not have the time, so I am starting one anyway, cos it is as interesting as your question.

But I do hope we continue speaking about the pros and cons of front porting, considering most people (includes self) are space starved.
Regards

 

[Nitin K]

That's such a lovely question @Nitin K bhai!
And some very lovely answers.
It is sad that it got derailed into another topic - pro vs consumer audio.

And I do agree with the person who said that after post 37, it needed to be branched out. Mods may not have the time, so I am starting one anyway, cos it is as interesting as your question.

But I do hope we continue speaking about the pros and cons of front porting, considering most people (includes self) are space starved.
Regards

Thanks K-pad. Apparently the port chuffing is one of the main reasons for rear port design. Anyways let's hope there is a solution for bookshelf speakers in the future for people like us with a room size constrain

 

[imagineer]

Unless the port is very well designed and the inside of the cabinet well damped, it can cause leakage of midrange frequencies due to port pipe resonances, chuffing noises at higher drive levels, etc. These are more audible when the port is at the front of the speaker compared to when it is at the back.

This totally explains it for me.
As Argho said somewhere above, having rear ported speakers will need more space from back walls. That explains why some speakers have down firing ports (Polk ES55?s) .
But, I've also seen speakers having front and rear ports. What are they trying to solve?

 

[grindstone]

This totally explains it for me.
As Argho said somewhere above, having rear ported speakers will need more space from back walls. That explains why some speakers have down firing ports (Polk ES55?s) .
But, I've also seen speakers having front and rear ports. What are they trying to solve?

An extra source radiation origin to decrease the impact of any single reflection from a boundary by the driver, the other port, or both. Smoothing. Sometimes "mutual coupling" arguments can be made.

 

[imagineer]

Thank you!

An extra source radiation origin to decrease the impact of any single reflection from a boundary by the driver, the other port, or both. Smoothing. Sometimes "mutual coupling" arguments can be made.

 

[Decadent_Spectre]

Thanks @Decadent_Spectre
I am looking around for CDs. Will keep these brands in mind. As you said the foam will help in taming harshness. Usually harshness can be caused by break up modes of the CD and polar pattern flips due to diffraction. The speciality with Mabat's waveguides is that given a good driver with benign break ups, his waveguide is supposedly the best available one right now that tames diffraction to the best known possible extent due to the oblate spheroidal horn profile and his seemless horn mouth termination contour in the free standing configuration. This is why I think Earl Geddes said foam might not be required with this waveguide. But since I am new to all this, there might be some detail that I have missed and would have to find out issues with experimentation and more learning. Hence I will definitely keep the foam suggestion in mind.

Regarding development of overall acoustic concept (with crossover), I have attached a sample development chart that I use with VituixCAD, which will have all details that one can ask for. This is captured using a semi-dual channel measurement set up. It will have impulse response, step response, ETC, SPL magnitude and phase, excess group delay, power response, horizontal and vertical directivities, filter target transfer functions etc. So we are covered on the graphs front. Only thing is I will have to take 180degree horizontal polar measurements (won't probably need vertical due to the symmetries involved in the construct). I will do this with a turn table I have. All this effort so that we are fully insured and confident on the measurements front. Next step would be listening impressions and tuning, which is where the devil lies..

Hopefully I will get a cabinet built for the woofer, which is where my projects get stuck often due to me having no time to do woodworking and all friends who know that being busy. Will start a thread and keep updating progress once this starts.

Thanks for the graphs but I meant the measured graphs of the end product when it is finished. Will you be measuring outdoors and taking high level/full power measurements? I know I might be in the minority but if it ain't loud...

 

[Vineethkumar01]

Thanks for the graphs but I meant the measured graphs of the end product when it is finished. Will you be measuring outdoors and taking high level/full power measurements? I know I might be in the minority but if it ain't loud...

I will definitely post measurement graphs at the end which will show overall trends but the absolute SPL levels, I don't know how much I will be able to increase to.
For initial development, I am planning indoor gated measurements/gated measurements on my apartment building roof top (as long as they don't kick me out ). For this, even 1W power will be plenty loud I guess due to the sensitivity of the drivers involved. This will also be reasonably enough for crossover work since a gate window of about 4-5ms will give reasonable (though less) accuracy around an 800Hz crossover point. I don't know if I will be able to get the speaker to an open place and take free field/ground plane measurements. I will try.

 

[Decadent_Spectre]

I will definitely post measurement graphs at the end which will show overall trends but the absolute SPL levels, I don't know how much I will be able to increase to.
For initial development, I am planning indoor gated measurements/gated measurements on my apartment building roof top (as long as they don't kick me out ). For this, even 1W power will be plenty loud I guess due to the sensitivity of the drivers involved. This will also be reasonably enough for crossover work since a gate window of about 4-5ms will give reasonable (though less) accuracy around an 800Hz crossover point. I don't know if I will be able to get the speaker to an open place and take free field/ground plane measurements. I will try.

1W? Are you shifting to tubes?

In all seriousness I doubt 1W will be that loud though on the rooftop it will travel far if your mid/hi is 105db sensitive or more.

 

[Vineethkumar01]

1W? Are you shifting to tubes?

In all seriousness I doubt 1W will be that loud though on the rooftop it will travel far if your mid/hi is 105db sensitive or more.

I have not yet decided about any tube amps..
The woofer is 99dB sensitive. So event after baffle step, it will be about 94ish dB sensitive which is loud enough for a 1-2m measurement using 1 W. The CD will most probably be 110dB ish sensitivity one if I go with a 1.4inch CD. Again 1W is loud enough for sweeps.
But I will try with other levels. Since I am only familiar with direct radiating drivers, this one might require more levels and measurement from farther away. Anyway postulating measurement levels now is a futile exercise given that I don't have a box for the woofer and a CD+horn combo.
A CD+ horn combo that I have in mind (as of now, may change later with further research ) is a 1.4inch CD on Yuichi A-290 type horn/its modern adaptations. Very interesting studies have been going on regarding this horn recently
I feel that we are polluting this thread . We can continue this horn discussion over at my thread here: https://www.hifivision.com/threads/horn-based-speaker-projects.87003/#post-976441

 

[k-pad]

So, shouldn't a sealed enclosure have it's own benefits? Am assuming it would. But I don't know what drawbacks it would have.

Also, TL designs do mitigate some of the issues posed by ports?

 

[Decadent_Spectre]

So, shouldn't a sealed enclosure have it's own benefits? Am assuming it would. But I don't know what drawbacks it would have.

Also, TL designs do mitigate some of the issues posed by ports?

A sealed enclosure will not have the backwave to deal with but it will also roll off at a shallower slope. It is also the least efficient and most power hungry, it also has minimal cooling. On the other hand it has the least inherent issues in the upper bandwidth. While there are technical advantages to a sealed design IMO it doesn't sound that good for the woofer/bass range. A sealed enclosure also has the highest excursion demands.

A TL would have a very long rear port that is stuffed, it might even be called a RLH in my view. While this would help dissipate the backwave more effectively than a ported enclosure it would also provide less efficiency. I like to think of it as a middle ground between a sealed and ported enclosure. My knowledge on TLs are limited, hopefully someone with more knowledge can correct me if I am wrong.