Help understanding DIY listening impressions (OB)

[krips]

Well, I now have my Omnimic V2 and in conjunction with my dcx2496 have got my speaker tuned a little. It is a ~17"x40"x3" OB with 2 alpha 15s and a Dayton PS220 FR, powered by a Dayton DTA-1 amp (like 5w/ch). Here are my impressions/questions:
DCX settings: 2nd order LR @ 150HZ, 7db notches @ 300hz & 4khz.
1: It sounds very reveling, however, the majority of music I listen to (90s+ rock/metal) sounds so aweful I can hardly stand it. Like it's over the telephone or something. I haven't had the change to hook up my SACD dark side of the moon, but is this normal? Hotel california sounds pretty darn good I think.
2: Being OB, I'm not sure if the bass being different makes me think there's less of it, but I have <200hz at about +10db (no eq). Is there something that makes us hear bass different with OB? Am I a bass head? Is my amp too weak? Or do I just have to have a sub? (My 150lb 15" is upstairs and insanely hard to move)
3: Does what I would call "clarity" make a speaker sound very...forward? The vocals stand out much more on this for me than a standard cheapo bookshelf. The rest of the band seems to be almost in the background on many tracks.

Thanks!

[JonMarsh]

Have you measured the net 2 meter response? Your comments sound like you may not have the correct equalization setup to compensate for dipole roll off on the baffles.

Generally, if you're starting from scratch like this, I'd first work out the EQ to get each driver as flat as possible, including to an octave above or below your selected crossover point, especially dealing with any driver peaks or issues; then experiment with crossover types you want to consider. Usually you may want to use a higher order crossover such as LR4, to minimize the bandwidth needed for the transition.

Look at off axis smoothness as well- it's not uncommon to see a driver flare in off axis response in areas where you're above the dipole frequency governed by the driver and panel width.

[CraigJ]

It is a ~17"x40"x3" OB with 2 alpha 15s and a Dayton PS220 FR, powered by a Dayton DTA-1 amp (like 5w/ch).

Krips, how many amps are you using?

[wkhanna]

Half way around the world, on a rare, far too infrequent & more than well deserved vacation…….
..and still Jon makes time to help out a fellow enthusiast in need…..

Great Scott! What a guy!

[craigk]

Is there something that makes us hear bass different with OB? Am I a bass head?

yes the bass in OB designs do not sound like a box, and because you have listened to enclosed base most of your life, more than likely, it does sound different. OB designs are hard to get right sometimes. i have attempted several builds and only really like the sound of one. the design i like ended up being OB tweeter/mid and closed box on the bottom end. OB speakers often end up in a love/hate realationship. i have hated more than loved.

[jim1961]

Well, I now have my Omnimic V2 and in conjunction with my dcx2496 have got my speaker tuned a little. It is a ~17"x40"x3" OB with 2 alpha 15s and a Dayton PS220 FR, powered by a Dayton DTA-1 amp (like 5w/ch). Here are my impressions/questions:
DCX settings: 2nd order LR @ 150HZ, 7db notches @ 300hz & 4khz.
1: It sounds very reveling, however, the majority of music I listen to (90s+ rock/metal) sounds so aweful I can hardly stand it. Like it's over the telephone or something. I haven't had the change to hook up my SACD dark side of the moon, but is this normal? Hotel california sounds pretty darn good I think.
2: Being OB, I'm not sure if the bass being different makes me think there's less of it, but I have <200hz at about +10db (no eq). Is there something that makes us hear bass different with OB? Am I a bass head? Is my amp too weak? Or do I just have to have a sub? (My 150lb 15" is upstairs and insanely hard to move)
3: Does what I would call "clarity" make a speaker sound very...forward? The vocals stand out much more on this for me than a standard cheapo bookshelf. The rest of the band seems to be almost in the background on many tracks.

Thanks!

What does the FR look like at the listening position? Can you post the graph?

[Face]

What does the FR look like at the listening position? Can you post the graph?

+1.

My thoughts are your issues are due to a lack of a tweeter, EQ at the bottom end, plus any other FR issues...

I hope you have them toed in towards your ears.

[krips]

Thanks to all who have pitched in thus far. I currently have one speaker (I have a second PS220, but no more alphas) which I am measuring. and I'm listening/measuring on axis. I have one amp (using one channel for ps220, one for alpha 15s). I will attempt to do as suggested and flatten the ps220 and alphas individually, then try again and see where I'm at. I will see if I can't post some FR graphs once I'm done.

[jim1961]

Thanks to all who have pitched in thus far. I currently have one speaker (I have a second PS220, but no more alphas) which I am measuring. and I'm listening/measuring on axis. I have one amp (using one channel for ps220, one for alpha 15s). I will attempt to do as suggested and flatten the ps220 and alphas individually, then try again and see where I'm at. I will see if I can't post some FR graphs once I'm done.

While the mic may only see near field, your ears must be treated as far field. So lets a take a look at both in graph form.

[Saurav]

You need something around a 6dB/octave shelving EQ to lift the bass response of OB woofers. The EQ needs to start at the dipole corner frequency (determined by your baffle width), and go down as low as you can/want (depends on whether you're crossing to a sub, where you'll run out of excursion, etc. Linkwitz has some spreadsheets that help you calculate this stuff). You won't see the need for this in a nearfield measurement, because the dipole cancellation isn't really visible up close. And it's hard to measure bass far-field in a room because the room messes up bass measurements in general. But the math doesn't lie An individual speaker/room may need slightly more or less EQ, but I would suggest starting with a 6dB shelving filter, and then tweaking from there. Be careful about overdriving the DCX. I've done it, digital clipping doesn't sound pretty.

[Jonasz]

Without seeing any measurements it sounds like an eq/responseproblem. I listen to a lot of "bad" rock/metalrecordings on my dipoles and they sound very listenable in spite of the quality of the programmaterial. An even on- and offaxis response is the key to that I think. The bass should be full but without most of the "hangover" associated with most boxes. Maybe the alpha with its tiny xmax contributes to the lack of bass?

[krips]

I just figured out that I'm also using only half of the stereo signal, could it be that in some recordings the 'non-mononess' would make it sound off?

[Face]

You mean, "non-stereo"...and yes.

[AdelaaR]

I just figured out that I'm also using only half of the stereo signal, could it be that in some recordings the 'non-mononess' would make it sound off?

You're listening to only one side of a stereo recording and you're complaining that it doesn't sound very good.
I'm sorry but ... HELLO?
At least set your player to mix both signals so that you at least hear all of the material ... but even then it isn't going to sound as intended.
Stereo music isn't simply two signals ... the mixing and mastering engineers use the stereo to do all kinds of subconscious stuff with your brain.
If you leave out the stereo ... it obviously isn't going to sound as interesting.
That ... and the fact that indeed your FR may be off.

[krips]

Indeed. For some reason I thought I had it set to sum the two signals, but not so. I've since added an additional 14" or so of wings so that the drivers are in a U baffle. Now I'm getting some bass.

[Juhazi]

It is really unbelievable to hear how a OB/frameless driver loses it's low end. craigk said that the only dipole construction he liked had a closed box bass. I am doing the same! I use a 12" midbass as a dipole eq'd and highpassed LR4 at ~180Hz to 600 LR2

[AdelaaR]

Indeed. For some reason I thought I had it set to sum the two signals, but not so. I've since added an additional 14" or so of wings so that the drivers are in a U baffle. Now I'm getting some bass.

The problem with bass is that it doesn't move in a certain direction but behaves like air pressure.
Adding wings is unlikely going to help much, I'm afraid.
Unless you completely kill that energy coming from the back of those drivers, that energy will find it's way to the front and will disrupt whatever is going on there.

[Rudolf]

Well, I now have my Omnimic V2 and in conjunction with my dcx2496 have got my speaker tuned a little. It is a ~17"x40"x3" OB with 2 alpha 15s and a Dayton PS220 FR, powered by a Dayton DTA-1 amp (like 5w/ch). Here are my impressions/questions:
DCX settings: 2nd order LR @ 150HZ, 7db notches @ 300hz & 4khz.

You will not like to hear that, but in your current approach you are practically doing your best to avoid bass.
What can you do?
Extend your very small baffle to a H-frame for the Alphas. You find the dimensions in http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf
Get yourself a decent power amp to drive the Alphas. The cheapest used 50 W stereo amp you can get will perform better with your Alphas than the meager 5 W of that DTA-1 amp.
Measure the Alphas at your listening position and apply the proper bass EQ.

Dipole bass does sound different than boxed bass - but if done right, a large majority of listeners will prefer the dipole bass.

[BobEllis]

Another possibility, I don't see mention of shelving filters. Give them a try if you haven't. Usually dipoles want a shelving filter to match the dipole roll off. A shelf and notches has the effect of a Linkwitz transform. That may be what you need.

H-frames certainly make it easier to get deep bass, approximating a wider baffle. I haven't used Martin's tool, but suspect that it will help minimize the resonance issue of H-frames.