Compact monitor

[sebackman]

That was neat. I have not seen them before. Is the 2450 without the snout identical to a 2450SL, except for the dia? Do you have any measures on the horns/box. Pretty cool that the horn cover the driver. –Learning every day.

I built a similar speaker using a SR4722X cabinets with 2206 and 2450SL on 2332. I had to make distance rings to the 2206 and add some acoustic foam to the sides to mitigate the standing waves from the recessed baffle. Maybe yours are better and it is not a problem.
http://www.audioheritage.org/vbullet...highlight=suck

Well, I need to manufacture adapters as the 2451 has a wider bold circle than the D2. I had hoped to have them this weekend but I won't get them until next week. I will post some measures then. Same with the VTX F12 horn, uses the smaller bolt circle. I’m making an adapter for them too. Please see picture.



All the best
//RoB

[John W]

That was neat. I have not seen them before. Is the 2450 without the snout identical to a 2450SL, except for the dia? Do you have any measures on the horns/box. Pretty cool that the horn cover the driver. –Learning every day.

Here are some measurements I took a while ago.

The first is with both the 2206 and the horn together.

The second is cut off at 200hz for some reason, but includes a small inductor I added to try and bring down the bump at 12k.

[sebackman]

John W, that is very good measurement results. I hope to get near that with my small project.

Ok, here is some update on the Compact Monitor project progress.

We are planning to use the 2206 beneath the M2 waveguide in an active setup. Driver will be a 2451Be and/or 2451Ti. I have looked at other 12” but it seem like the improvement, except possible for the fantastic 1200Fe, is not really that big when used with subs (80Hz) and crossed into the M2 waveguide at 800-ish Hz. I don’t really have room for a 15” in this system, so a 12 will have to do. 2006 should do a good job there. Comments or suggestions?

I have tried the M2 waveguide with the 2451Ti’s and that resulted in some interesting measures. It appears that the 2451 Ti is a bit sensitive to this horn, albeit nice and predictable. The picture shows two different drivers in the same graph just for a sanity check. Please disregard the black line which is the sum of them. The differences are close enough to be the result of position in my improvised measuring setup. I normally do measures out door and will do that here also later.



Attached is a picture of the M2 from the front and rear side.



They do not come with a driver mount and as far as I know the original is not available, so I had to make some of my own. Even if they were available they are designed for the D2 with a smaller nose that the 245x / 476 4” drivers. The larger bold circle of the 2451 is almost as bid as the mount circle on the horn. I had some adapters made by aircraft quality aluminium and drilled them for both the large and small JBL bolt circle. I also made some adapters for the VTXF12 horn to accept the larger bolt patter of the 2451. Please see picture.




I will revert with more info as we progress. Please come with suggestions and comments on the project.

All the best
//RoB

[sebackman]

Some additional info

The new VTX F12 horn seems good and attached is a picture of that beside the M2. -Pretty big difference size wise.



Even the VTX F12 horn seems to be an improvement over the older PT-F95HT. It is being offered by JBL in the new VTX series with the D2 and in the STX with the 2453 so it should be ok with booth. Attached is a measure with two 2451H Ti drivers. Please disregards the black line.



It appears that the Ti drivers may not reach all the way with the M2 waveguides but maybe the Be’s can. However there is room to introduce a 045 in the bottom of the M2 waveguide. Pls see picture. Let's see what happens with some EQ applied to those curves





All the best
//RoB

[4313B]

We are planning to use the 2206 beneath the M2 waveguide in an active setup. Driver will be a 2451Be and/or 2451Ti. I have looked at other 12” but it seem like the improvement, except possible for the fantastic 1200Fe, is not really that big when used with subs (80Hz) and crossed into the M2 waveguide at 800-ish Hz. I don’t really have room for a 15” in this system, so a 12 will have to do. 2006 should do a good job there. Comments or suggestions?

Compared to the 1200FE, the 2206H has the large four-inch voice coil and increased sensitivity.

[macaroonie]

Thanks for posting the pics of the M2 throat. For some reason I reckoned they were moulded in 4 parts with the joins along the diagonals. Seems not.
It would be fun to carve those from wood.

BTW you are not messing around here , some good engineering going on , nice.

[ivica]

I have tried the M2 waveguide with the 2451Ti’s and that resulted in some interesting measures. It appears that the 2451 Ti is a bit sensitive to this horn, albeit nice and predictable. The picture shows two different drivers in the same graph just for a sanity check. Please disregard the black line which is the sum of them. The differences are close enough to be the result of position in my improvised measuring setup. I normally do measures out door and will do that here also later.



All the best
//RoB

Hi RoB,

Interestingly that the response is almost flat, not as expected CD horn behavior.

regards
ivica

[sebackman]

JBL 2451J Be on JBL M2. Pretty nice.




Kind regards
//RoB

[sebackman]

Some additional data

Test JBL M2 / 2451H Be 2015 04 03

Indoor workshop lower floor, upward on work bench.

LSPCad 60 (latest update), M-Audio Fast Track Pro, Samson Servo 200, Earthworks M30 (calibrated), 33mf in series,
2-Channel measurement, 48kHz, 512 buff, 65536 MLS, 1/24 smooth offset 64 cm, range 40db, window 4ms (OBS short window only high frequency usable), approx 86db SP level. No EQ or PEQ.

Kind regards
//RoB

[baldrick]

An impressions how the m2 waveguide sound compared to other horns?? Are the M2 waveguid really that good or is it more the DSP and D2 driver makes the difference in M2?

Kind of surprised to see the measurment with 2451 dropping so much downto the 800hz crossing point, I would expect the D2 driver to drop even more than 2451!?