Driver Suggestions

[bjackson]

Well I have been stumbling around in the dark looking for drivers that I might like, but never heard, so I thought I'd ask the people who know this stuff.

I am looking to make a 3way system, possibly WMTM, WMTMW, or even WMT. I want it to sound something like Canton Audio. This is because they are the only high end speaker I have ever heard (The Canton RC-A), so I know I am biased, but I absolutly loved the sound. I listen to a lot of rock, jazz and classical.

These will be used 100% for music, but may be moved over to home theater/music use later. I am pretty set on my Vifa XT25 ring radiator tweeter, but can anyone recommend the other componets?

I have been looking at Hi-Vi, Peerless Scanspeak Vifa, and Audax, primarily. I am looking to spend no more than 500-550 on drivers, but would like to get away with less. Also if you think my tweeter needs rethinking, please say so!

Thanks for any and all suggestions.

[5th element]

First Ill make a point about sensativity and bafflestep. After you take into consideration bafflestep you need to factor in a 6dB loss in bass somewhere now this can be done in a number of ways. In three ways.

One - use standard baffle step compensation on the midrange. This will pad down the upper end of its response by 6dB causing you to loose 6dB of sensativity. If you start with a 86dB mid you will be looking at 80 after the compensation. Now crossing this over to the bass requires a bass driver of 86dB sensativity, the bass driver will have already been thru bafflestep so its sensativity will be 80db, and will match the mid.

Two - in the design of the highpass on the midrange you alter the Q of the network to compensate for bafflestep, this results in no loss in sensativity so your 86dB midrange driver will still be 86dB. But your bass drivers at 86dB will still be 80 after baffle step. So to compensate for this you need to parallel up bass drivers to get back an extra 6dB to match the midrange.

So you would either have a WMT or a WWMT (same as the canton you mention) depending on which you choose.

I mention this because two of your designs mention MTM, there is no reason to do this unless you are going to use large numbers of bass drivers or are planning on going active.

WIth an MTM mid section (if using 86dB mids) would end up at 92dB, if going by rule one you would end up at 86dB and require a WWMTM. If by rule two you would keep the 92dB sensativity and requite a WWWWMTM. The first still requires loss because 6dB of your midsensativity is lost. The second requires a huge amount bass drivers and a potentially devastating impedance.

I would suggest a WWMT, this way you dont loose any power to bafflestep compensation circuits and the bass is kept at a 4ohm average which most solid states of today can handle.

Right now thats over, the XT you mention is a fine choice just dont cross it over too low. Seeming as the canton uses a metal midrange driver then I would suggest using a SEAS L15RLY/P. This presents a problem, the XT does not like low Xovers and to get the most out of the L15 you should cross is between 2-2.5khz, I would suggest using a SEAS 27TDFC or scan speak d2905 tweeter. The metal cone comes with its own difficulties in design, if you are not comfortable designing a crossover for a metal driver then use the peerless HDS 850488 as the midrange.

The peerless is an easier match for bass drivers because it is 3dB more sensative then the seas metal cone and matches the sensativity of bass drivers better. Im guessing you dont want to use huge drivers in this and if you like the canton 8" bass dirvers could be used. I would suggest using peerless CSX 850146 for bass, this is a 10" driver and sounds excellent for the price. The only draw back is the size, if used sealed this driver will require a 100l cabinet for two.

Its up to you 100l can be accomodated pretty easily if the box is tall, but you are still looking at a large speaker. If the speaker is a 1m tall and is 30cm wide then you arrive at about 43cm deep, this is not including the midrange chamber which should be about around 4-10 litres.

Give us more information on regards to size of this speaker.

[bjackson]

Hey thanks for the information, but I have some questions:

Well first, this speaker can literally be of any size as long as it's not more than 6 foot tall (i.e. goes out of the limits of me to carry it up the steps). Any sort of "acceptance factor" is unneccisary.

My idea for the MTM was to limit verticle dispersion, just BTW. I understand the concept of bafflestep...somewhat. Basically because there is a speaker (baffle) in the way, the bass does not radiate in a complete 2pi circle, but instead only goes directly, and therefore needs to be compensated for? WWMT would work for me, I was just wondering about vertical dispersion, etc, which I was told is much better in a MTM design.

Thank you for the reply!

[454Casull]

IIRC, wavelengths which are longer than the distance from the acoustic source to the edge of the baffle will radiate omnidirectionally, which means sound pressure at any given distance is 6dB lower than sound pressure from the same source firing only into half of 2pi steradians ("half" of omnidirectionality).

[5th element]

Yes that is correct so above a certain frequency all sound radiates 2pi but then as you drop below this frequency sound starts to radiate 4pi and then eventually all the sound is radiated 4pi.

When making a three way I would cross the bass drivers over the midrange after baffle step has occured. So basically the bass would all be operating omnidirectionally. Then compensate for the bafflestep on the midrange driver using the highpass (this way you dont loose any sensativity). I would not worry about the verticle dispersion of the MTM design over a MT. The vertical dispersion is infact worse in an MTM over an MT because of the comb filter effects generated by the two midranges. This does control the directivity ( ie reduces it) in the vertical axis and lessens ceiling and floor reflections, but generally people do not go for an MTM design unless they need it for added sensativity, or to half compensate for bafflestep in a two way by giving you back the 6dB you loose to the compensation.

If this is going to be passive and size is not a concern then I would recommend a WWMT with two peerless 850146 mounted push pull (one driver firing into the cabinet one driver firing out) for the bass, a peerless HDS 850488 for midrange and your pick of tweeter crossed over at about 150hz and 3000hz. Do you have measuring equipment? If not the bass to mid xover could be a little tricky to get right I can give you as much assistance as I can with this. I can also give you help with the mid/tweeter xover but thats nowhere near as predictable unless I measure the drivers myself.

[bjackson]

I do not have any driver measuring equipment, except I have a jerry-rigged RTA setup with my computer, and a multimeter. How much would a setup to test the T/S parameters of individual drivers be?

And why go for the isobaric (push pull), configuration? I thought that was used only for reducing speaker volume? [i just re read this, and note I mean enclosure volume, not dB volume]

Note also, I will be using these in small/medium sized rooms, if that helps any (mostly very small). However, in no way do I want to go with a sub/sat configuration, or have a dedicated subwoofer in anyway, although making these active does appeal to me, I don't have the cash to buy plate amps also.

[5th element]

Measuring the t/s parameters is the least of your concern, for designing boxes, most of the time, the manufactures specs are fine.

I didnt mean isobarik, I meant arrange the drivers just as you would for two drivers in a box, but invert one so it fires into the cabinet.

The best way to mount two bass drivers in a cabinet is actually to have one driver on the back and one on the front. The driver on the front it mounted normally with the cone firing out of the cabinet, and the the driver on the back is mounted magnet outside, firing into the cabinet. The drivers are wired out of phase of one another so one driver pushes as the other one pulls. This means one driver is trying to shake the cabinet one way and the other is trying to shake it the other, the net effect is a cancellation effect of the vibration in the cabinet.

If this is for small/medium sized rooms then two 10" drivers per cabinet will probably be over the top. Two 8" would probably be a better bet. Now if this was my money I would use two SEAS L22RN4X for the bass, a L15RLY/P for the midrange and a 27TDFC for the trebble. I am happy using metal cone drivers you might not be. How small a room are we talking? a two way might be more appropriate anyway, you'd be surprised at how much sound a good 6.5" midbass can kick out.

[bjackson]

I am in an apartment that is 12 x 8, so that's pretty small. Right now I have polk R30s (cheap floorstanders that I picked up on sale for 100 a pair), and I want to make a speaker that I can be satisfied with, or can upgrade easily. I just bought these Polks in December and I am already wanting to upgrade, and before that I had some pioneers, etc, etc.

I want a speaker that will go full range with a minimum of fuss, my current speakers are good for everything but the bottom octave, almost 0 response below 40hz (single 6.5 woofer). However, since I am a college student, I could be moving at any point to a new larger residence (I currently reside in an apartment, but I may be purchasing a house soon.)

How do you do the calculations for the push-pull design, or an even better question, what programs will do it for me? :-)

[5th element]

You do not need to calculate new boxes for a push pull design, its just the same as two drivers in a box. So in other words you just double the box size you calculate for one driver.

If bass is your main concern then simply add a sub a Peerless XLS + passive radiator and a plate amp will not cost a huge amount and will give you bass flat to 20hz and also be a very small sub.

If however you are after better everything, then a two way MT + sub is probably your best bet. Due to your living arangements smaller speakers would make sense and be easier to design, also there are lots of two way designs around for you to copy if something goes wrong.

That last octave you are after is hard to get unless you use big drivers, there is not much information in music below 40hz mind you but for HT it is important.

The extra bass only really starts to happen when you use a 10" drive unit.

[BassAwdyO]

There IS alot of content below 40hz in music. But not in ALL music. For example... Lil jon and the eside boys get low has a low note that's fundemental is right around 30-31hz. Maybe you dont listen to rap so you're saying ohh most rock doesnt have anything that low. Well my favorite band is Third eye Blind which is rock. I've FFT'd notes in their stuff JUST AS LOW!

I would say for music, flat to 30hz is a MUST! 20hz is optional.

Most people cant hear down to 20hz with moderate Spl. But I know for a fact that 30hz is plainly audible to most at less than 95db and probably down into the 80's for some.

I measured my hearing(tone recognition) down to 24hz on my system's max level. Below that I only hear things rattling, and not actual tones.

The impact response below 30hz offers is unparalleled by loud plainly audible frequencys. Not only does it add to movies, but it seriously adds to music.