Building a reflex becomes more complex when you want something different than the average end user. This is where those that are familiar with reflex designs will have the knowledge to build a cabinet that meets the aesthetics and performance level one is seeking. A lot of people down play a reflex design without realising a properly design reflex requires just as much effort as building a folded horn. 

It is precisely this reason why custom designs are not readily available whereas, more generic designs are available at an abundance on the Internet. 

Best Regards, 

DMorison wrote: The bigger the box and the lower the tuning frequency, the lower you may be able to go, but this normally comes at the cost of running out of linear excursion at lower power levels. HTH, David.

That only occurs when you choose the wrong driver for the job and try to extract every bit of SPL from a single driver. Things differ tremendously, once you use the proper driver for the job and use multiples which, is the concept of using a Quad Eighteen Box.

Once you move into multiple speakers playing the same frequencies, you will realise you will not need to drive your loudspeakers to mechanical failure to attain the SPL you are seeking. As a matter of fact, you will find yourself reducing the bass due to having too much bass.

Those who fall in the above category will understand wholeheartedly on such an experience.  

Best Regards,

Elliot Thompson wrote: DMorison wrote: The bigger the box and the lower the tuning frequency, the lower you may be able to go, but this normally comes at the cost of running out of linear excursion at lower power levels. HTH, David. That only occurs when you choose the wrong driver for the job and try to extract every bit of SPL from a single driver. Things differ tremendously, once you use the proper driver for the job .

That's why I brought it up - to try and help the OP avoid using the wrong box for their driver (or vice versa).

He seems set on using rather high powered amps for these, so over excursion is IMO almost inevitable.

Of course, I don't know how experienced he is - maybe he'll find that the extra efficiency from coupling lots of cones does indeed allow use at only a modest wattage, which will be fine - but if people don't highlight these issues before the build, then the possibility remains of the OP (or anyone else embarking on a similar project) trying to turn it up louder and being disappointed.

Elliot Thompson wrote: Building a reflex becomes more complex when you want something different than the average end user.

I don't know if I want something different than the average end user. I want to play old 70s Jamaican music and feel the bass. 90s synth bass in reggae, hip hop, house etc.

I don't want to miss out on the deepest lows. The aim is for magic in the dance.

When discussing frequencies it is interesting to note the lowest note on a bass guitar, the open E string is 41Hz. And I am also recalling that vinyl records (I won't be only playing vinyl) are said to be high passed at, IIRC, about 40Hz. If I aimed for 30Hz what compromises would I be incurring vs aiming for 40Hz. I may as well have my cake.

Just thinking aloud, a couple of people have quoted the lowest bass guitar open E string (41Hz) as a possible lowest necessary frequency to reproduce. But I am questioning if lower frequencies are still relevant. Perhaps the bass drum can have relevant info below 40Hz?

Elliot Thompson wrote:  This is where those that are familiar with reflex designs will have the knowledge to build a cabinet that meets the aesthetics and performance level one is seeking. A lot of people down play a reflex design without realising a properly design reflex requires just as much effort as building a folded horn.  It is precisely this reason why custom designs are not readily available whereas, more generic designs are available at an abundance on the Internet.  Best Regards,

Ok, so I do need to seek assistance from an experienced speaker box man.

Some previous comments about undesirable outcomes from mismatching a specific driver's characteristics with a cabinet design seem redundant if I am entering the Thiele and Small specifications of my JBL 2245H drivers into the bass reflex cabinet calculator.

Other comments regarding me having perhaps too much power for my configuration go against the recommendation of having twice the wattage per driver than the maximum RMS of the driver. Perhaps it was just warning me of the potential of blowing up drivers by turning it up too loud. I definitely don't intend to turn it up too loud. I assume that (4) quad 18 boxes with 1100W per driver playing in small to medium venues is bordering on overkill. Maybe I will be tempted to show off a little with some super Bassy tunes. But I doubt it.

I just want to be able to play Dawn Penn's 1992 version of 'No, no, no' produced by Steely and Clevie and have the synth baseline sound big, friendly and effortless.

I read the English blokes talk about which sound is the heaviest and cringe. It sounds like low self esteem egotistical male competitiveness turning what should be a fun, healing sound to dance to into a painful contest where hearing protection is required. Perhaps there is some subjectivity in what is too loud in individuals perceptions. But if you need ear plugs then that confirms to me it is too loud. I will have no part in that absurd mentality of masochism.

But hey it can be fun to push things a little and overload on bass. I may be more sensitive than most. I used to tolerate louder sound when drunk. I don't get drunk anymore.

The whole idea behind having so many drivers is to have a big effortless, friendly sound.

What do you guys think of my configuration of a quad 18 box with a double 15 on top and one JBL2445H 2 inch compression driver and multi cell wooden horn. Is that unbalanced? I assume that to get an even sound I just need to adjust the levels going to each box via the volume controls after each crossover band.

Elliott words of too much bass are soothing. Better to have too much than too little.

Can someone spoon feed me and tell me what they think are some good parameters. Just for food for thought.

I think I've communicated my sound intentions quite specifically.  

Roman wrote: Elliot Thompson wrote: Building a reflex becomes more complex when you want something different than the average end user. I don't know if I want something different than the average end user. I want to play old 70s Jamaican music and feel the bass. 90s synth bass in reggae, hip hop, house etc. I don't want to miss out on the deepest lows. The aim is for magic in the dance.

So what do you want a Quad Eighteen Box for?

Quad Eighteen boxes you see others own derived from Roots Sound systems.  None of them are going to play Hip Hop more so House Music. 

Roman wrote: When discussing frequencies it is interesting to note the lowest note on a bass guitar, the open E string is 41Hz. And I am also recalling that vinyl records (I won't be only playing vinyl) are said to be high passed at, IIRC, about 40Hz. If I aimed for 30Hz what compromises would I be incurring vs aiming for 40Hz. I may as well have my cake. Just thinking aloud, a couple of people have quoted the lowest bass guitar open E string (41Hz) as a possible lowest necessary frequency to reproduce. But I am questioning if lower frequencies are still relevant. Perhaps the bass drum can have relevant info below 40Hz?

If I recall correctly, 20 Hz - 20.000 kHz became the standard as it was based on what the human ear can hear in terms of audio reproduction. Of course, there are frequencies below 20 Hz that can be detected by the human ear. However, 20 Hz is pretty much commonly heard by the average person. Focusing on one instrument and assuming that is lowest frequency while disregarding other instruments is not how one looks to create a bass cabinet. The only person that follows that principal are those who play a bass guitar.

Have you even taken the time to enter the TS Parameters in a free loudspeaker program to determine if the loudspeakers you own are suitable for a Reflex Box?

Let me tell you how Speakerplans work. If you do not make the effort (post charts of the speaker in question in a loudspeaker simulation software) those who can help you, will not help you. The ones who know how achieve what a person seeks is willing to help along the way if we see the person is making the effort. So post some charts of the JBL 2245 in a box you designed in a loudspeaker simulation software program.

Once you do that, you will find answers and, we will help you.

Best Regards,

Here you go... http://www.linearteam.org/" rel="nofollow - http://www.linearteam.org/

Best Regards,

Elliot Thompson wrote: So what do you want a Quad Eighteen Box for?

Mostly 70s roots reggae. But also 70s and 80s soul, funk, disco, boogie dance music, hip hop, house. 

Elliot Thompson wrote: Quad Eighteen boxes you see others own derived from Roots Sound systems.  None of them are going to play Hip Hop more so House Music.

I have read people explain that bass reflex cabinets are flatter in frequency reproduction than scoops and extend lower in frequencies reproduced than scoops. Also that concert PA systems mostly use bass reflex cabinets because they are more broadly compatible with rock and other genres. How do the bass reflex cabinets used by reggae sound systems differ from other bass reflex cabinets?

Roman wrote: When discussing frequencies it is interesting to note the lowest note on a bass guitar, the open E string is 41Hz. And I am also recalling that vinyl records (I won't be only playing vinyl) are said to be high passed at, IIRC, about 40Hz. If I aimed for 30Hz what compromises would I be incurring vs aiming for 40Hz. I may as well have my cake. Just thinking aloud, a couple of people have quoted the lowest bass guitar open E string (41Hz) as a possible lowest necessary frequency to reproduce. But I am questioning if lower frequencies are still relevant. Perhaps the bass drum can have relevant info below 40Hz?

Elliot Thompson wrote: If I recall correctly, 20 Hz - 20.000 kHz became the standard as it was based on what the human ear can hear in terms of audio reproduction. Of course, there are frequencies below 20 Hz that can be detected by the human ear. However, 20 Hz is pretty much commonly heard by the average person. Focusing on one instrument and assuming that is lowest frequency while disregarding other instruments is not how one looks to create a bass cabinet. The only person that follows that principal are those who play a bass guitar.

You didn't respond to the possibility that vinyl records could be high passed at 40Hz which is interesting and I would have thought relevant when lot's of reggae sound systems that pride themselves on big bass are playing vinyl records.

If I can reproduce the full range of human hearing 20Hz to 20Khz that should be satisfactory.

I was responding to Davids advice in this thread, which was:

DMorison wrote: My advice: accept that getting down into the very low frequency range may be unrealistic,  http://www.target.com/" rel="nofollow - target  a system that goes good and loud to about 40Hz (which is the lowest note on a normally tuned bass guitar anyway) and you'll end up with a more manageable box size.

Elliot Thompson wrote: Have you even taken the time to enter the TS Parameters in a free loudspeaker program to determine if the loudspeakers you own are suitable for a Reflex Box?

I took the time to enter into the online calculator I detailed. I will now do as you advise and use WinISD for mac and report back with useful data. This is the first time someone has required me to use WinISD or similar. 

Elliot Thompson wrote: Let me tell you how Speakerplans work. If you do not make the effort (post charts of the speaker in question in a loudspeaker simulation software) those who can help you, will not help you. The ones who know how achieve what a person seeks is willing to help along the way if we see the person is making the effort. So post some charts of the JBL 2245 in a box you designed in a loudspeaker simulation software program. Once you do that, you will find answers and, we will help you.

Roman wrote: WinISD is for windows. I am on a mac. I will research mac alternatives. Roman.

Sounds good. The calculator you are using is too limited for those who are new to loudspeaker building. You need to visually see what is taking place with a graphical chart at the given frequencies. 

Best Regards, 

Using the bass guitar as a ballpark reference is, as Elliot points out, only part of the picture.

It’s a pretty good ballpark for getting started, but as with all generalizations, it only takes you so far. There certainly can be content that goes below this in many genres – even from instruments you wouldn’t think go as low.

Herewith the spectrum of track one from https://www.youtube.com/watch?v=SZbFLHlB8o4" rel="nofollow - Rodrigo Y Gabriela’s self titled album . This is made using only two acoustic guitars which have a normal lowest note of 82Hz, but due to their playing styles you can see that there is a bass peak at around 56Hz, and 40Hz is only a few dB lower in level than that.

At the time I suggested 40Hz, you hadn’t given any example of actual tracks you’d play, but you now have. I listened to a version of that Dawn Penn track on youtube and I think it has strong content at least a bit lower than 40Hz. The analyser I use requires a copy of the file on the hard drive though, so I can’t tell you that for sure.

I’ve already suggested you run some of your own tracks through an analyser – have you done that yet?

If not, please do so – then you’ll actually know something for a fact rather than trusting a couple of random blokes on t’interwebz. ;)

Some previous comments about undesirable outcomes from mismatching a specific driver's characteristics with a cabinet design seem redundant if I am entering the Thiele and Small specifications of my JBL 2245H drivers into the bass reflex cabinet calculator.

Not all calculators are created equal. They don’t all show you the complete picture. The one you linked to at mh-audio.nl for example didn’t seem to want to even show a response graph, much less an excursion curve so there’s no way it can tell you if you’re risking pushing the driver too far.

Elliot’s suggestion of WinISD is a good one – there are programs you can use on a Mac to run windows programs, Parallels is one name I’ve heard of, or if you’re more computer-savvy you can, I believe, set up your Mac to run windows itself – not sure how that works but it may need partitioning the hard drive and setting up a dual boot system.

Re: Power Levels.

The number on the spec sheet is measured without reference to excursion or sound quality – it’s merely the amount of power the driver can withstand without any damage or change to its operating parameters. You use modelling software to determine how much power it’s sensible to apply to a specific driver in a specific cabinet on a case by case basis.

The generalizations (eg 2x RMS) are best applied to whatever power rating you end up with after doing that, not the raw driver rating. To be fair, many people don’t realise that and simply think the nominal rating will be good regardless of what box the driver’s in.

Note – the 2245H is a 300W driver – the 600W you see is already the “program” rating so that’s the one to which you match amp power, not 1200W.

Note 2 – pet peeve of mine:  “RMS” is a mathematical technique that applies to datasets that include both positive and negative values which would cancel out to zero if you did a normal average – this does not apply to power, so anyone you see mentioning Watts RMS is just using it as an (inaccurate) shorthand for “average” power. The best terms are continuous, program and peak – with program being the target for amp size in most common cases. (Again, Elliot will probably point out some exception to this generalization – to be fair he’s trying to get you to think more deeply, but IMO generalizations are a useful starting point as otherwise you can easily get overwhelmed with detail.)

What were the over excursion issues you mentioned? Too much amplifier power making the speakers move too much and causing damage?

If you ask the driver to move further than it can do so (in a linear manner), the first things that happen are 1, the sound quality reduces and 2, it stops getting louder in proportion to the increase in input signal – in other words, distortion increases. If you keep pushing it further then eventually, yes, you can end up damaging it.

Again, this is why you’re best to model in something more capable than that website first.

So would entering the TS specs into a cabinet design calculator guarantee the cabinet matches the driver?

I think you probably know the answer to this already, but just in case: No. As stated above, not all such calculators are equal. Generally the simpler it is, the more assumptions the creator of the calculator has had to make for you, meaning you can’t see the whole picture.

The only information I have about matching driver to cabinet is to enter in the Thiele and Small parameters of the Driver into the speaker box calculator. Anything else I should know.

Lots, if you want a really good outcome.

Even if you can’t run WinISD immediately, download it and read the helpfile – it’s HTML so even a Mac should manage that ;) It contains a lot of good info how to design a project taking account of things like practical box sizes, port lengths, excursion levels etc.

So essentially you are saying the lower I want the lowest frequencies of the box to reproduce the larger the box will need to be.

Yup, exactly.

Thanks for the Hoffmans Iron Law link. I have read that before but needed a refresher. It is a spectrum of decisions isn't it. I decide how big a cabinet is too big and work back from there.

That is one sensible way of going about it, yes. There’s no point designing a project that looks amazing on paper, then realizing once you’ve built it you can’t get it out your front door!

Whew! You still with me. Just thought I would share the specifics of using this online calculator. May help inform any helping me. My understanding is I can alter the 'box volume' and calculate different results. Maybe I can alter the F-3 frequency as Elliot and DMorison have suggested as the aim. 40Hz or something. A big question in my mind is why did the calculator recommend: 293.17L That seems to be the variable that has resulted in a box that is too big and goes down to 17Hz F-3.

Not gonna quote the whole post line by line, I hope what I’ve written above highlights some of the limitations of this particular calculator so just a few points.

First, if you get to using something like WinISD then you input the number of drivers as part of your setting up of the project, so what you see modelled already takes account of that.

I didn’t see any option in that calculator to adjust the tuning frequency, so again, that’s showing how limited this particular one is.

The suggested box size is based on assumptions made by the author of the calculator – usually starting with keeping the response as flat as possible, as deep as possible, hence coming up with a large box size. Not everyone needs that though – again, more complete modelling allows you to take more control of what you get out of the project, rather than relying on assumptions made by others.

Even entering JBL's minimum recommended enclosure volume of 225L times four 900L gives an F-3 of 19Hz? Half the suggested target of 40Hz. How accurate is this process and our communications?

I think that calculator might have assumed your 900l was for one driver, hence F3 appearing way deeper than you might have expected. Unless you’d input a revised set of TS parameters with Vas quadrupled first?

Can someone spoon feed me and tell me what they think are some good parameters.

I think Elliot more or less covered this but to put it another way: Speaker designing is too complicated for spoonfeeding, so newcomers do have to either tackle a bit of a learning curve, or get very frustrated. It looks like you’re on the right track though, so please do keep at it J

Unfortunately, the nature of the internet is that a lot of the info you need is spread around in different places, and there’s a lot of limited or even bad info out there. Even trying to answer most of the questions you’ve asked in the last few hours has resulted in this being a long and probably quite hard to follow post.

So, take-away messages: Do some spectral analysis to see how deep you actually need to go, and read the helpfile in WinISD as it is one fairly good starting point for the learning you’ll need to do to get the most out of this.

HTH,

David.