[Tip24/96]

I am looking to get some opinions on these two compression drivers. The JBL 2446 versus the 2447. I am itching to build three nice two way, high efficiency speakers for my ht. These will be used with either the JBL 2226 or the AE TD15M for the bottom octaves. I am also debating on using either the Seos 24 or the JBL 2384 waveguides, depending on which compression driver I choose. These will be installed in a baffle wall, and might use an active crossover as I have the necessary amplifier channels and DSP units to do so, or, if I can find someone that would be willing to assist on the crossover, I may go passive. Not entirely sure yet.

The 2446 is a 2" and the 2447 is a 1.5". I will at some point add a Be diaphragm to all 3. I am guessing that the 2447 will be slightly better on the top end being that it is a 1.5" versus a 2"? What are the pro's and cons of using one over the other? I can get the 2447's for under $175 each and the 2446's for around the same price. I like the idea of using a JBL 2384 horn with the 2447 as the horn is relatively cheap and can be shipped and received in less than a week compared to the Seos 24, which would take a long time and cost more.

How do you guys feel about these possibilities and what do you recommend?

 

[kingpin111]

Here is the technical difference in the two.
http://www.jblpro.com/pub/technote/tn_v1n21.pdf

I haven't heard the 2447 so I can't really comment on it.

 

[Mfusick]

Smaller will have a better top. Bigger will cross lower.

But either of those drivers is great to cross at 800hz so I would think the 1.5" is the ticket.

 

[MKtheater]

My 2447 extends down to 500hz in room easily.

 

[Mfusick]

My 2447 extends down to 500hz in room easily.

yeah my comment was more about where you would want to cross a 15" or lower. 800hz is about the size of a 15" wave.

 

[MKtheater]

yeah my comment was more about where you would want to cross a 15" or lower. 800hz is about the size of a 15" wave.

Yeah, I have my surrounds crossed at 1.5khz and unless at the extreme spl it is fine. The point being that there is no advantage to a 2inch if the 1.5 crosses just as low. I like the 2447 better overall myself. They are very heavy and huge though!

 

[Mfusick]

Yeah, I have my surrounds crossed at 1.5khz and unless at the extreme spl it is fine. The point being that there is no advantage to a 2inch if the 1.5 crosses just as low. I like the 2447 better overall myself. They are very heavy and huge though!

He said he wants to cross a JBL 2226 or a TD15M. Both 15" woofers.

Ideally you want to cross to a 15" woofer before cone break up becomes a problem, and you want to cross in a manner that allows a good blending at the crossover point both on and off axis. All woofers start beaming (sound straight out like a head lamp) when the frequency wave size is start to equal the woofer size. Smaller woofers this happens higher up, bigger the woofer the lower this happens. For a 15" ideally you'd want to cross at 800hz or less generally speaking- so my comment was mostly based on this but I didn't explain why I just arbitrarily picked 800hz of the top of my head so I can see where the confusion could be. That was my mistake. Since the CD he is looking at should both be able to handle this, I would probably lean towards the 1.5" because I feel like the 1.5" would have a better top end than the 2" (at least in theory). Most 2" can't reach up high to 20khz. While personally I don't always think you need all the way to 20khz, anything short of 18khz might be "pro audio" sounding since pro audio products often roll off above 10khz because they use big CD's that don't reach up very well. Also, those highs can be damaging at loud volumes so it's not a good idea to blast high frequencies very loud at people, which is another reason why a lot of pro audio stuff rolls off on top.

Often some wave guides will also lose directivity or collapse below a certain frequency so you could use this to account for the crossover blend too. Once you get to sub 1khz crossovers on wave guides the area where the wave guide will lose it's pattern control should be also accounted for. It takes a big wave guide to cross really low. Lot's of stuff to consider.

The more I learn about audio the more I realize it's all about trade offs. If you want a low freq, you lose some on the top. If you want a great top, you lose some ability on the bottom. It's this constant give and take of compromises and the endless challenge of maximizing everything that makes DIY audio so much fun.

Would't it just be so easy if there was a driver that did great 20hz-20khz in one driver, point source, and phase perfect. ?
The only design I know that even comes close to something like that is a synergy horn.

 

[tuxedocivic]

I would choose your waveguide then choose your compression driver, not the other way around.

Consider the Iwata 300. That's what kingpin selected and the match up with the 2446 is really impressive. But costs more than either of your choices and not easily mounted.

 

[Mfusick]

Good point ^.

@ OP what wave guide were you thinking? A wave guide that won't hold the pattern control that low also makes you not need the bigger CD.

 

[pnw]

I haven't used either one, but they are both 4" diaphragms, so low-end response should be ~ equal. The 1.5" exit should have a bit more consistent off-axis response, the 2" a bit less throat distortion at truly ear-bleed levels (in a home environment, your ears may add more HD than the horns). In computer sims, I've found larger throats tend to have more internal HF cancellations than smaller throats -not a given, but a tendency- so the 1.5" exit may take better advantage of Be diaphragms when you get them. So, IF you can find the HxV pattern you want in a 1.5" horn with no diffraction bumps, that may be the better set of trade-offs.

 

[Tip24/96]

ok, so to take Tuxs' advice and pick the horn or waveguide first, how do you fellows think the Seos24 would work compared to a JBL 2384 or 2352? The main drawback that I see with the Seos24 is #1 the length of time it would take to order and receive, which, it is my understand that it could be weeks or months coming from Poland, and #2 being the cost, which at $250 each is pretty high, compared to the JBL2384 which I can get for around $100. So in your opinions, how would the Seos24 perform versus a JBL2384?

I am leaning towards the 2447 on a JBL 2384, but, I have yet to speak withor read anyone's opinion who have heard both, and MKtheater's comments about how awesome his 2446 sounds has me thinking that if I did end up going the 2447 route, I might wonder "what if?"

 

[MKtheater]

ok, so to take Tuxs' advice and pick the horn or waveguide first, how do you fellows think the Seos24 would work compared to a JBL 2384 or 2352? The main drawback that I see with the Seos24 is #1 the length of time it would take to order and receive, which, it is my understand that it could be weeks or months coming from Poland, and #2 being the cost, which at $250 each is pretty high, compared to the JBL2384 which I can get for around $100. So in your opinions, how would the Seos24 perform versus a JBL2384?

I am leaning towards the 2447 on a JBL 2384, but, I have yet to speak withor read anyone's opinion who have heard both, and MKtheater's comments about how awesome his 2446 sounds has me thinking that if I did end up going the 2447 route, I might wonder "what if?"

I have the 2447. I have them on 2352 horns. The 2384 is a much bigger horn being 30 inches wide

 

[Wrager]

The 2384 horn is 1.5" entry (as is the 2352) but there are many 1.5" throat JBL CD's- 2430, 2431, 2432, 2435 (Be), 2447, 2450-SL, 2451, 2452SL just to name a few. It's a nice compromise between the 1" and 2" versions. Maybe that's why JBL kept refining them. That's what so much fun about JBL!


Only the 4" versions can be fitted with a Truex (Materion) Be phragms. I wrote them recently and asked about the cheaper version as well as the 3" ones. He ducked the question. I don't think they will ever happen.

The 2384 was designed specifically to be behind a perfed screen. I'm not sure what the implications would be naked??? I wish Zilch (RIP) was still around.

 

[LTD02]

z says up to 10khz nothing really and if you listen a little off axis nothing at all. above 10k the directivity continues to increase in order to help the 10-20khz region "punch through" acoustically transparent screens. without the screen it may sound a smidgen bright, but that's about it. you can see this by the on axis rising response (red) as compared to the 30 degree off axis (green).

 

[Tip24/96]

I realize that the 2384 is huge, but, how does it compare, in directivity, polars, and how low does it hold the pattern compared to the Seos24? The 2384 can be had from JBL directly for $135 each, which is over $115 dollar cheaper than each Seos24.

Looks like I will definitely be going with the 2447! If it extends higher in frequency and has less overall distortion in the top end then it would seem like a "no brainer" compared to the 2446. Speaking of which, are there any categories, at all, that the 2446 does better than the 2447?

 

[kingpin111]

I don't know if this helps but here is a semi legible graphing I made.

 

[Tip24/96]

Ok, so right now I am planning to go with the big 2384 horn, instead of the Seos24. I can get three 2384's delivered for right at $400, as opposed to the Seos24, which would cost over $750 delivered. Before I finalize the order, do you guys think I am making the right decision on the 2384 versus the Seos24? These will definitely be going behind a screen and I have plenty of room in my baffle wall.

 

[Tip24/96]

For the compression driver, I am still leaning towards the 2447. Do you guys know of any better options, SQ wise, in the sub $200 catagory that would fit on a 1.5" 2384? I found a guy on A-gon with a pair of slightly used 2447's that are only a couple of years old, and he wants $350 for the pair. I will definitely be upgrading to Be diaphragms this fall, if I go this route.

 

[Wrager]

Are they the J or H version? The BMS 4555 is roughly $160

 

[tuxedocivic]

That's a 1".

EDIT - Mfusick's post dissapeared, so ignore that...