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markusA 18th February 2012 03:19 PM

Help me pick the best drivers for my hybrid esl?
I have four sets of perf-metal for my stators, both curved and flat in a larger and a smaller size.
I'm currently writing the code for the CNC mill to start cutting pieces for the jig/stretch -table. Hopefully I'll have something ready in the upcomming week.

I intend to build myself bass-towers similar to Calvin's.
I think 6 or 8 drivers per side will be just what the doctor ordered.
Now, it's di-poles in a A-frame and I've never really buildt any di-poles before.

I'd really appreciate if you could help me pick the best drivers for my build.
I'll X-over somewhere between 250-300Hz probably. (I'm undecided about regular passive crossover or digital ones?)
It would be great if I could use the panels + bass-towers as a stand alone system. I am however ready to discuss a subwoofer if the need arises.

So, please help. :shy:

I am on a budget so I'll probably have a difficult time finding the $$$ for the most exotic drivers but I'm open to all suggestions. :)

I suppose both 6" and 8" drivers are fair game?
I aim for 110dB peak sound pressure and 95dBc as loudest average listening level.

geraldfryjr 18th February 2012 08:20 PM

6 Attachment(s)
I personaly have not ventured into the Dipole bass realm as of yet,But I do know that displacement rules.

So try to choose a driver with the largest diameter that is suitable for you as well as the largest xmax.

There are many 8" subs that fit this requirement that are very affordable.
In my search's I find it difficult to find a 6.5" woofer that has as much Xmax as some of the 8"woofers that cost much less than a 6.5" in some cases.

I have 8 X 8" subs that I was going to use for a pair of dipoles but sadly two of them got ruined.

So just to give you an idea I have a design planned using a ported small box type cabinet that with 3 of them should produce 115db at only about 100 watts to 150 watts from 25hz on up using a filter assistance for below 40hz.
This will allow me to custom tailor the extreme lows for what ever room I will be using at the time.

Note, That at 25hz, This is at an Xmax of .4025" for three drivers according to Winlsd.

So I would think that 6 X 8" per side should easily get you to your 110db goal.

The woofer that I have are the Optimus PRO-CSW800 and MTX had a woofer with nearly the exact same specs.
Both are discontinued models But I have found the MTX woofers for $15 to $40 a peice online.

MCM and Parts Express have similar equivelent models in that price range as well.

I have mentioned before that I had built a 6 X 6.5" open back using Radio Shack drivers back in the day that I used for may bass guitar rig and I vaguely remember that I think they had gotten in to the 106db to 108db range and played very nicely.

That is all about I can remember as it was 15 years ago.
I didn't have the equipment at that time to do speaker measurements accurately as all I had was my trusty analog db meter from Radio Shack.

Right now I have 4 X 10" and 4 X 12" (in regular speaker boxes) and I can get a comfortable 109db at 14' away ( my listening point ) in a room of 11' X 18.5' X 8' with my 500 watt per channel amp.

This is at a clean level but I have not measured the exact amount of power it takes though.

I do measure about 119db standing about 2 feet from the front of the stack on one side.

I hope this give you a good Idea of what it takes to reach these kind levels.

In this room I get a very comfortable full sounding loudness of 105db with very low distortion all around the room.

It is very hard to measure the THD due to the reflections in the room but this system typically shows below .5% across its bandwidth and only about a maximum of 2% to 5% in below about 60hz.

The low THD is the benefit from using so many drivers.

I may have already posted these but here are a few samples.

Some of these are with no midranges or tweeters and is where I am at right now. he,he

Enjoy !!

jer :)

markusA 19th February 2012 08:20 AM

Just from the top of my head I have only one real candidate, the Peerless SLS8 (P830667).
Fair Xmax and highish Qts although the Fs is a little on the high side for my taste and the sensitivity isn't all that great.
The price is ok though...

I have next to no experience with Optimus or MTX, I don't know what they compare to sound wise? Are we talking true "hi-fi" level audio quality or what?
I know some PA drivers sound awsome so I'm not complaining, I just don't know anything about these brands and their performance.

geraldfryjr 19th February 2012 09:13 AM

They were car audio subs that Radio shack used to carry and I picked up a bunch of them in a sell out for $15 each back in 2004.
They were my first venture into these types of drivers and I was (still am) quite impressed with their performance for what they had cost me.

I just got off of the Parts Express web site and the only real deal they had were some 6.5" woofers for $8 if you by four or more they look similar to the ones I had only mine had poly cones and these are treated paper.
I am almost tempted to get 12 of them myself.

6-1/2" Subwoofer Speaker 299-114

The peerless woofer are very good drivers.
I know MCM used to have some good 8" subs for cheap but it has been a while since I have scoped them out.
Most all of the decent drivers from Parts Express are in the $30 to $80 range.

The Dayton Audio DCS205-4 8" woofer looks pretty good as well.
It is a little cheaper than the Peerless and has a lower fs of 30Hz as well as a lower Qts.

Dayton Audio DCS205-4 8" Classic Subwoofer 4 Ohm 295-200

Peerless 830667 8" Paper Cone SLS Subwoofer 264-1102

The RS series would be the way to go but unfortunately they cost twice as much.

The one thing that I don't like about my subs is that I get some vent noise or something at high excursion from the voice coil area.
I have not exactly determined what is causing it but it really isn't noticeable when playing music,just when using test tones.

I even cut the dust cap off of one of them and it seems to be coming from the aluminium voice coil former making noise.
I tried to dampen it some how but I haven't figured it out yet.
But this just shows where quality counts I have heard some cheap 12's that were worse than mine.

I thought that I built my boxes strong enough but the drivers are powerful enough to make the front panel resonate badly at about 200Hz to 300Hz (almost right at 250Hz on one of them).
This is quite annoying,But again it is only noticeable when using test tones as music sounds just fine through them.

I will check out the MCM site and report back what I find.

Jer :)

geraldfryjr 19th February 2012 09:29 AM

This is the one I had in mind,

MCM Audio Select 8'' High Excursion Woofer - 120W RMS 4ohm | 55-2421 (552421) | MCM Audio Select

It is similar to my woofer In fact I like its specs better than mine.
It has a nice low Fs of 25.7Hz and a Qts of .22 and a High Qms at 14 but I think that is what you want for a dipole sub system.
But don't quote me on this as I forget right now what is supposed to be good and it always seems to be a very highly debatable subject.
But they look pretty good to me and would be my choice to try out.

But simulated it in Winlsd first I am not sure if the specs are correct the Qts and Qes seem kind of low this is typical of off brand driver specs.


jer :)

markusA 19th February 2012 10:07 AM

The Peerless 830667 appear to come with two different set of specs? They are very different and I don't know which to put my faith in?


It's like you say, what to actually look for in a driver?
You appear to look for lowish Qts while I've been searching for highish Qts?
You can't tune the box much so the lower Qts you get the more EQ'ing should be necessary?
I can be very much mistaken in this case? It's possible that low Qts is the way to go? I think a lot of people are attributing a "faster" sound to a low Qts, a high number being assosiated with a "slow or sluggish" sound.
I can only guess at the implications but impulse response seem a likely culprit?

A low Qts driver is much easier to find and they are usually more sensitive as well I believe? There are a lot of pro drivers that would fit I think?

I like the price of the MCM driver, almost half of the Peerless one. :)

geraldfryjr 19th February 2012 10:48 AM

Well like I said I am not sure what to look for,for dipole system as I will have to do some re-reading.

If you sim the MCM driver in Winlsd it doesn't look like alot but if you put 6 of them in a sealed 6 cu.ft. box they really start to shine.
You can put a Linkwitz transform filter on them to make them flat to 20hz,but they quickly run out of Xmax at 30hz and 37.4 watts.
But it is still producing 108.5db flat with -1db at 30Hz on up.
And with out the filter 119db at 432.4 watts.
This is only 72watts per driver and they are rated at 120watts rms/240peak so I don't for see any issues there.
That is still 104.6 at 20hz and 110.25 at 30hz.

Added another 6db to that for two cabinets.

It is the group delay that you want to watch in order to keep the bass from getting muddy sounding or as some say, Slow.

Also when looking at the simulation you have to keep in mind that the low end droop in the response curve is going to be more flat due to room gain as well.
Depending on the size of the room this can be anywhere from 3db to as much as 12db.

I have read in order to simulate a dipole in Winlsd is to use a very large closed box.
I am not sure how accurate this is but it does make sense.
As the box gets larger the effects of the pressure built up inside the the box has a lesser effect on the driver thus flattening out the response curve to a certain point showing just the effects of the driver parameters them selves,then the sensitivity appears to drop past that.

jer :)

markusA 19th February 2012 12:13 PM

I totally forgot about Linkwitz Transform, that would probably do the trick.

The most significant drawback of modeling as a large CB is probably not seeing the dipole cancellation?
Ah, group delay... I sometimes get the words mixed up.
Your figures does sound appealing to me and I'll see what I can do about running some sims.

I have an array of software so I'll se what can be done. :)
Winlsd I've never worked with though.

geraldfryjr 19th February 2012 12:33 PM

I have some good excel stuff on dipoles as well.
Let me know if you have excel and I will get them together for you.


markusA 19th February 2012 12:47 PM

That sounds awsome.
I can model a dipole in one piece of software.
In another I can do the Linwitz transform.
I don't know how to model a dipolar linearray with the LT though. :P

I'd love to see what you have in those excel files. :)

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